Chen, Jiahui; Zhou, Hui; Duan, Changkui; Peng, Xinhua
2017-03-01
Entanglement, a unique quantum resource with no classical counterpart, remains at the heart of quantum information. The Greenberger-Horne-Zeilinger (GHZ) and W states are two inequivalent classes of multipartite entangled states which cannot be transformed into each other by means of local operations and classic communication. In this paper, we present the methods to prepare the GHZ and W states via global controls on a long-range Ising spin model. For the GHZ state, general solutions are analytically obtained for an arbitrary-size spin system, while for the W state, we find a standard way to prepare the W state that is analytically illustrated in three- and four-spin systems and numerically demonstrated for larger-size systems. The number of parameters required in the numerical search increases only linearly with the size of the system.
Global Landslides on Rapidly Spinning Spheroids
Scheeres, Daniel J.; Sanchez, P.
2013-10-01
The angle of repose and conditions for global landslides on the surfaces of small, rapidly spinning, spheroidal asteroids are studied. Applying techniques of soil mechanics, we develop a theory for, and examples of, how regolith will fail and flow in this microgravity environment. Our motivation is to develop an understanding of the "top-shaped" class of asteroids based on analytical soil mechanics. Our analysis transforms the entire asteroid surface into a local frame where we can model it as a conventional granular pile with a surface slope, acceleration and height variations as a function of the body's spin rate, shape and density. A general finding is that the lowest point on a rapidly spinning spheroid is at the equator with the effective height of surface material monotonically increasing towards the polar regions, where the height can be larger than the physical radius of the body. We study the failure conditions of both cohesionless and cohesive regolith, and develop specific predictions of the surface profile as a function of the regolith angle of friction and the maximum spin rate experienced by the body. The theory also provides simple guidelines on what the shape may look like, although we do not analyze gravitationally self-consistent evolution of the body shape. The theory is tested with soft-sphere discrete element method granular mechanics simulations to better understand the dynamical aspects of global asteroid landslides. We find significant differences between failure conditions for cohesive and cohesionless regolith. In the case of cohesive regolith, we show that extremely small values of strength (much less than that found in lunar regolith) can stabilize a surface even at very rapid spin rates. Cohesionless surfaces, as expected, fail whenever their surface slopes exceed the angle of friction. Based on our analysis we propose that global landslides and the flow of material towards the equator on spheroidal bodies are precipitated by exogenous
International Nuclear Information System (INIS)
Bahr, Benjamin; Hellmann, Frank; Kaminski, Wojciech; Kisielowski, Marcin; Lewandowski, Jerzy
2011-01-01
The goal of this paper is to introduce a systematic approach to spin foams. We define operator spin foams, that is foams labelled by group representations and operators, as our main tool. A set of moves we define in the set of the operator spin foams (among other operations) allows us to split the faces and the edges of the foams. We assign to each operator spin foam a contracted operator, by using the contractions at the vertices and suitably adjusted face amplitudes. The emergence of the face amplitudes is the consequence of assuming the invariance of the contracted operator with respect to the moves. Next, we define spin foam models and consider the class of models assumed to be symmetric with respect to the moves we have introduced, and assuming their partition functions (state sums) are defined by the contracted operators. Briefly speaking, those operator spin foam models are invariant with respect to the cellular decomposition, and are sensitive only to the topology and colouring of the foam. Imposing an extra symmetry leads to a family we call natural operator spin foam models. This symmetry, combined with assumed invariance with respect to the edge splitting move, determines a complete characterization of a general natural model. It can be obtained by applying arbitrary (quantum) constraints on an arbitrary BF spin foam model. In particular, imposing suitable constraints on a spin(4) BF spin foam model is exactly the way we tend to view 4D quantum gravity, starting with the BC model and continuing with the Engle-Pereira-Rovelli-Livine (EPRL) or Freidel-Krasnov (FK) models. That makes our framework directly applicable to those models. Specifically, our operator spin foam framework can be translated into the language of spin foams and partition functions. Among our natural spin foam models there are the BF spin foam model, the BC model, and a model corresponding to the EPRL intertwiners. Our operator spin foam framework can also be used for more general spin
The susceptibilities in the spin-S Ising model
International Nuclear Information System (INIS)
Ainane, A.; Saber, M.
1995-08-01
The susceptibilities of the spin-S Ising model are evaluated using the effective field theory introduced by Tucker et al. for studying general spin-S Ising model. The susceptibilities are studied for all spin values from S = 1/2 to S = 5/2. (author). 12 refs, 4 figs
Stability of global entanglement in thermal states of spin chains
International Nuclear Information System (INIS)
Brennen, Gavin K.; Bullock, Stephen S.
2004-01-01
We investigate the entanglement properties of a one-dimensional chain of qubits coupled via nearest-neighbor spin-spin interactions. The entanglement measure used is the n-concurrence, which is distinct from other measures on spin chains such as bipartite entanglement in that it can quantify 'global' entanglement across the spin chain. Specifically, it computes the overlap of a quantum state with its time-reversed state. As such, this measure is well suited to study ground states of spin-chain Hamiltonians that are intrinsically time-reversal-symmetric. We study the robustness of n-concurrence of ground states when the interaction is subject to a time-reversal antisymmetric magnetic field perturbation. The n-concurrence in the ground state of the isotropic XX model is computed and it is shown that there is a critical magnetic field strength at which the entanglement experiences a jump discontinuity from the maximum value to zero. The n-concurrence for thermal mixed states is derived and a threshold temperature is computed below which the system has nonzero entanglement
A spin exchange model for singlet fission
Yago, Tomoaki; Wakasa, Masanobu
2018-03-01
Singlet fission has been analyzed with the Dexter model in which electron exchange occurs between chromophores, conserving the spin for each electron. In the present study, we propose a spin exchange model for singlet fission. In the spin exchange model, spins are exchanged by the exchange interaction between two electrons. Our analysis with simple spin functions demonstrates that singlet fission is possible by spin exchange. A necessary condition for spin exchange is a variation in exchange interactions. We also adapt the spin exchange model to triplet fusion and triplet energy transfer, which often occur after singlet fission in organic solids.
Nuclear spin noise in the central spin model
Fröhling, Nina; Anders, Frithjof B.; Glazov, Mikhail
2018-05-01
We study theoretically the fluctuations of the nuclear spins in quantum dots employing the central spin model which accounts for the hyperfine interaction of the nuclei with the electron spin. These fluctuations are calculated both with an analytical approach using homogeneous hyperfine couplings (box model) and with a numerical simulation using a distribution of hyperfine coupling constants. The approaches are in good agreement. The box model serves as a benchmark with low computational cost that explains the basic features of the nuclear spin noise well. We also demonstrate that the nuclear spin noise spectra comprise a two-peak structure centered at the nuclear Zeeman frequency in high magnetic fields with the shape of the spectrum controlled by the distribution of the hyperfine constants. This allows for direct access to this distribution function through nuclear spin noise spectroscopy.
New Spin Foam Models of Quantum Gravity
Miković, A.
We give a brief and a critical review of the Barret-Crane spin foam models of quantum gravity. Then we describe two new spin foam models which are obtained by direct quantization of General Relativity and do not have some of the drawbacks of the Barret-Crane models. These are the model of spin foam invariants for the embedded spin networks in loop quantum gravity and the spin foam model based on the integration of the tetrads in the path integral for the Palatini action.
Tunnel splitting in biaxial spin models investigated with spin-coherent-state path integrals
International Nuclear Information System (INIS)
Chen Zhide; Liang, J.-Q.; Pu, F.-C.
2003-01-01
Tunnel splitting in biaxial spin models is investigated with a full evaluation of the fluctuation functional integrals of the Euclidean kernel in the framework of spin-coherent-state path integrals which leads to a magnitude of tunnel splitting quantitatively comparable with the numerical results in terms of diagonalization of the Hamilton operator. An additional factor resulted from a global time transformation converting the position-dependent mass to a constant one seems to be equivalent to the semiclassical correction of the Lagrangian proposed by Enz and Schilling. A long standing question whether the spin-coherent-state representation of path integrals can result in an accurate tunnel splitting is therefore resolved
Spin-spin correlations in the tt'-Hubbard model
International Nuclear Information System (INIS)
Husslein, T.; Newns, D.M.; Mattutis, H.G.; Pattnaik, P.C.; Morgenstern, I.; Singer, J.M.; Fettes, W.; Baur, C.
1994-01-01
We present calculations of the tt'-Hubbard model using Quantum Monte Carlo techniques. The parameters are chosen so that the van Hove Singularity in the density of states and the Fermi level coincide. We study the behaviour of the system with increasing Hubbard interaction U. Special emphasis is on the spin-spin correlation (SSC). Unusual behaviour for large U is observed there and in the momentum distribution function (n(q)). (orig.)
Slave equations for spin models
International Nuclear Information System (INIS)
Catterall, S.M.; Drummond, I.T.; Horgan, R.R.
1992-01-01
We apply an accelerated Langevin algorithm to the simulation of continuous spin models on the lattice. In conjunction with the evolution equation for the spins we use slave equations to compute estimators for the connected correlation functions of the model. In situations for which the symmetry of the model is sufficiently strongly broken by an external field these estimators work well and yield a signal-to-noise ratio for the Green function at large time separations more favourable than that resulting from the standard method. With the restoration of symmetry, however, the slave equation estimators exhibit an intrinsic instability associated with the growth of a power law tail in the probability distributions for the measured quantities. Once this tail has grown sufficiently strong it results in a divergence of the variance of the estimator which then ceases to be useful for measurement purposes. The instability of the slave equation method in circumstances of weak symmetry breaking precludes its use in determining the mass gap in non-linear sigma models. (orig.)
Weigel, Martin
2011-09-01
Over the last couple of years it has been realized that the vast computational power of graphics processing units (GPUs) could be harvested for purposes other than the video game industry. This power, which at least nominally exceeds that of current CPUs by large factors, results from the relative simplicity of the GPU architectures as compared to CPUs, combined with a large number of parallel processing units on a single chip. To benefit from this setup for general computing purposes, the problems at hand need to be prepared in a way to profit from the inherent parallelism and hierarchical structure of memory accesses. In this contribution I discuss the performance potential for simulating spin models, such as the Ising model, on GPU as compared to conventional simulations on CPU.
Model independent spin determination at hadron colliders
International Nuclear Information System (INIS)
Edelhaeuser, Lisa
2012-01-01
By the end of the year 2011, both the CMS and ATLAS experiments at the Large Hadron Collider have recorded around 5 inverse femtobarns of data at an energy of 7 TeV. There are only vague hints from the already analysed data towards new physics at the TeV scale. However, one knows that around this scale, new physics should show up so that theoretical issues of the standard model of particle physics can be cured. During the last decades, extensions to the standard model that are supposed to solve its problems have been constructed, and the corresponding phenomenology has been worked out. As soon as new physics is discovered, one has to deal with the problem of determining the nature of the underlying model. A first hint is of course given by the mass spectrum and quantum numbers such as electric and colour charges of the new particles. However, there are two popular model classes, supersymmetric models and extradimensional models, which can exhibit almost equal properties at the accessible energy range. Both introduce partners to the standard model particles with the same charges and thus one needs an extended discrimination method. From the origin of these partners arises a relevant difference: The partners constructed in extradimensional models have the same spin as their standard model partners while in Supersymmetry they differ by spin 1/2. These different spins have an impact on the phenomenology of the two models. For example, one can exploit the fact that the total cross sections are affected, but this requires a very good knowledge of the couplings and masses involved. Another approach uses angular distributions depending on the particle spins. A prevailing method based on this idea uses the invariant mass distribution of the visible particles in decay chains. One can relate these distributions to the spin of the particle mediating the decay since it reflects itself in the highest power of the invariant mass s ff of the adjacent particles. In this thesis we
Model independent spin determination at hadron colliders
Energy Technology Data Exchange (ETDEWEB)
Edelhaeuser, Lisa
2012-04-25
By the end of the year 2011, both the CMS and ATLAS experiments at the Large Hadron Collider have recorded around 5 inverse femtobarns of data at an energy of 7 TeV. There are only vague hints from the already analysed data towards new physics at the TeV scale. However, one knows that around this scale, new physics should show up so that theoretical issues of the standard model of particle physics can be cured. During the last decades, extensions to the standard model that are supposed to solve its problems have been constructed, and the corresponding phenomenology has been worked out. As soon as new physics is discovered, one has to deal with the problem of determining the nature of the underlying model. A first hint is of course given by the mass spectrum and quantum numbers such as electric and colour charges of the new particles. However, there are two popular model classes, supersymmetric models and extradimensional models, which can exhibit almost equal properties at the accessible energy range. Both introduce partners to the standard model particles with the same charges and thus one needs an extended discrimination method. From the origin of these partners arises a relevant difference: The partners constructed in extradimensional models have the same spin as their standard model partners while in Supersymmetry they differ by spin 1/2. These different spins have an impact on the phenomenology of the two models. For example, one can exploit the fact that the total cross sections are affected, but this requires a very good knowledge of the couplings and masses involved. Another approach uses angular distributions depending on the particle spins. A prevailing method based on this idea uses the invariant mass distribution of the visible particles in decay chains. One can relate these distributions to the spin of the particle mediating the decay since it reflects itself in the highest power of the invariant mass s{sub ff} of the adjacent particles. In this thesis
Model independent spin determination at hadron colliders
Energy Technology Data Exchange (ETDEWEB)
Edelhaeuser, Lisa
2012-04-25
By the end of the year 2011, both the CMS and ATLAS experiments at the Large Hadron Collider have recorded around 5 inverse femtobarns of data at an energy of 7 TeV. There are only vague hints from the already analysed data towards new physics at the TeV scale. However, one knows that around this scale, new physics should show up so that theoretical issues of the standard model of particle physics can be cured. During the last decades, extensions to the standard model that are supposed to solve its problems have been constructed, and the corresponding phenomenology has been worked out. As soon as new physics is discovered, one has to deal with the problem of determining the nature of the underlying model. A first hint is of course given by the mass spectrum and quantum numbers such as electric and colour charges of the new particles. However, there are two popular model classes, supersymmetric models and extradimensional models, which can exhibit almost equal properties at the accessible energy range. Both introduce partners to the standard model particles with the same charges and thus one needs an extended discrimination method. From the origin of these partners arises a relevant difference: The partners constructed in extradimensional models have the same spin as their standard model partners while in Supersymmetry they differ by spin 1/2. These different spins have an impact on the phenomenology of the two models. For example, one can exploit the fact that the total cross sections are affected, but this requires a very good knowledge of the couplings and masses involved. Another approach uses angular distributions depending on the particle spins. A prevailing method based on this idea uses the invariant mass distribution of the visible particles in decay chains. One can relate these distributions to the spin of the particle mediating the decay since it reflects itself in the highest power of the invariant mass s{sub ff} of the adjacent particles. In this thesis
Transverse Ising spin-glass model
International Nuclear Information System (INIS)
Santos, Raimundo R. dos; Santos, R.M.Z. dos.
1984-01-01
The zero temperature behavior of the Transverse Ising spin-glass (+-J 0 ) model is discussed. The d-dimensional quantum model is shown to be equivalent to a classical (d + 1)- dimensional Ising spin-glass with correlated disorder. An exact Renormalization Group treatment of the one-dimensional quantum model indicates the existence of a spin-glass phase. The Migdal-Kadanoff approximation is used to obtain the phase diagram of the quantum spin-glass in two-dimensions. (Author) [pt
Global positioning of spin GPS scheme for half-spin massive spinors
Jadach, Stanislaw; Was, Zbigniew
2001-01-01
We present a simple and flexible method of keeping track of the complex phases and spin quantisation axes for half-spin initial- and final-state Weyl spinors in scattering amplitudes of Standard Model high energy physics processes. Both cases of massless and massive spinors are discussed. The method is demonstrated and checked numerically for spin correlations in tau tau production and decay. Its application is in our work of combining effects due to multiple photon emission (exponentiation) and spin, embodied in the Monte Carlo event generators for production and decay of unstable fermions such as the, tau lepton, t-quark and hypothetical new heavy particles. In particular, the recurrent problem of combining, for such unstable fermions, one author's calculation of production and another author's calculation of decay, in the presence or absence of multiple photon effects, is there given a practical solution, both for Weyl spinor methods and for the traditional Jacob-Wick helicity methods. Moreover, for massiv...
Inozemtsev's hyperbolic spin model and its related spin chain
International Nuclear Information System (INIS)
Barba, J.C.; Finkel, F.; Gonzalez-Lopez, A.; Rodriguez, M.A.
2010-01-01
In this paper we study Inozemtsev's su(m) quantum spin model with hyperbolic interactions and the associated spin chain of Haldane-Shastry type introduced by Frahm and Inozemtsev. We compute the spectrum of Inozemtsev's model, and use this result and the freezing trick to derive a simple analytic expression for the partition function of the Frahm-Inozemtsev chain. We show that the energy levels of the latter chain can be written in terms of the usual motifs for the Haldane-Shastry chain, although with a different dispersion relation. The formula for the partition function is used to analyze the behavior of the level density and the distribution of spacings between consecutive unfolded levels. We discuss the relevance of our results in connection with two well-known conjectures in quantum chaos.
Efficient micromagnetic modelling of spin-transfer torque and spin-orbit torque
Abert, Claas; Bruckner, Florian; Vogler, Christoph; Suess, Dieter
2018-05-01
While the spin-diffusion model is considered one of the most complete and accurate tools for the description of spin transport and spin torque, its solution in the context of dynamical micromagnetic simulations is numerically expensive. We propose a procedure to retrieve the free parameters of a simple macro-spin like spin-torque model through the spin-diffusion model. In case of spin-transfer torque the simplified model complies with the model of Slonczewski. A similar model can be established for the description of spin-orbit torque. In both cases the spin-diffusion model enables the retrieval of free model parameters from the geometry and the material parameters of the system. Since these parameters usually have to be determined phenomenologically through experiments, the proposed method combines the strength of the diffusion model to resolve material parameters and geometry with the high performance of simple torque models.
Experimental tests of proton spin models
International Nuclear Information System (INIS)
Ramsey, G.P.; Argonne National Lab., IL
1989-01-01
We have developed models for the spin-weighted quark and gluon distribution in a longitudinally polarized proton. The model parameters are determined from current algebra sum rules and polarized deep-inelastic scattering data. A number of different scenarios are presented for the fraction of spin carried the constituent parton distributions. A possible long-range experimental program is suggested for measuring various hard scattering processes using polarized lepton and proton beams. With the knowledge gained from these experiments, we can begin to understand the parton contributions to the proton spin. 28 refs., 5 figs
Discrete approximations to vector spin models
Energy Technology Data Exchange (ETDEWEB)
Van Enter, Aernout C D [University of Groningen, Johann Bernoulli Institute of Mathematics and Computing Science, Postbus 407, 9700 AK Groningen (Netherlands); Kuelske, Christof [Ruhr-Universitaet Bochum, Fakultaet fuer Mathematik, D44801 Bochum (Germany); Opoku, Alex A, E-mail: A.C.D.v.Enter@math.rug.nl, E-mail: Christof.Kuelske@ruhr-uni-bochum.de, E-mail: opoku@math.leidenuniv.nl [Mathematisch Instituut, Universiteit Leiden, Postbus 9512, 2300 RA, Leiden (Netherlands)
2011-11-25
We strengthen a result from Kuelske and Opoku (2008 Electron. J. Probab. 13 1307-44) on the existence of effective interactions for discretized continuous-spin models. We also point out that such an interaction cannot exist at very low temperatures. Moreover, we compare two ways of discretizing continuous-spin models, and show that except for very low temperatures, they behave similarly in two dimensions. We also discuss some possibilities in higher dimensions. (paper)
Discrete approximations to vector spin models
International Nuclear Information System (INIS)
Van Enter, Aernout C D; Külske, Christof; Opoku, Alex A
2011-01-01
We strengthen a result from Külske and Opoku (2008 Electron. J. Probab. 13 1307–44) on the existence of effective interactions for discretized continuous-spin models. We also point out that such an interaction cannot exist at very low temperatures. Moreover, we compare two ways of discretizing continuous-spin models, and show that except for very low temperatures, they behave similarly in two dimensions. We also discuss some possibilities in higher dimensions. (paper)
Quantum decoration transformation for spin models
Energy Technology Data Exchange (ETDEWEB)
Braz, F.F.; Rodrigues, F.C.; Souza, S.M. de; Rojas, Onofre, E-mail: ors@dfi.ufla.br
2016-09-15
It is quite relevant the extension of decoration transformation for quantum spin models since most of the real materials could be well described by Heisenberg type models. Here we propose an exact quantum decoration transformation and also showing interesting properties such as the persistence of symmetry and the symmetry breaking during this transformation. Although the proposed transformation, in principle, cannot be used to map exactly a quantum spin lattice model into another quantum spin lattice model, since the operators are non-commutative. However, it is possible the mapping in the “classical” limit, establishing an equivalence between both quantum spin lattice models. To study the validity of this approach for quantum spin lattice model, we use the Zassenhaus formula, and we verify how the correction could influence the decoration transformation. But this correction could be useless to improve the quantum decoration transformation because it involves the second-nearest-neighbor and further nearest neighbor couplings, which leads into a cumbersome task to establish the equivalence between both lattice models. This correction also gives us valuable information about its contribution, for most of the Heisenberg type models, this correction could be irrelevant at least up to the third order term of Zassenhaus formula. This transformation is applied to a finite size Heisenberg chain, comparing with the exact numerical results, our result is consistent for weak xy-anisotropy coupling. We also apply to bond-alternating Ising–Heisenberg chain model, obtaining an accurate result in the limit of the quasi-Ising chain.
Quantum decoration transformation for spin models
International Nuclear Information System (INIS)
Braz, F.F.; Rodrigues, F.C.; Souza, S.M. de; Rojas, Onofre
2016-01-01
It is quite relevant the extension of decoration transformation for quantum spin models since most of the real materials could be well described by Heisenberg type models. Here we propose an exact quantum decoration transformation and also showing interesting properties such as the persistence of symmetry and the symmetry breaking during this transformation. Although the proposed transformation, in principle, cannot be used to map exactly a quantum spin lattice model into another quantum spin lattice model, since the operators are non-commutative. However, it is possible the mapping in the “classical” limit, establishing an equivalence between both quantum spin lattice models. To study the validity of this approach for quantum spin lattice model, we use the Zassenhaus formula, and we verify how the correction could influence the decoration transformation. But this correction could be useless to improve the quantum decoration transformation because it involves the second-nearest-neighbor and further nearest neighbor couplings, which leads into a cumbersome task to establish the equivalence between both lattice models. This correction also gives us valuable information about its contribution, for most of the Heisenberg type models, this correction could be irrelevant at least up to the third order term of Zassenhaus formula. This transformation is applied to a finite size Heisenberg chain, comparing with the exact numerical results, our result is consistent for weak xy-anisotropy coupling. We also apply to bond-alternating Ising–Heisenberg chain model, obtaining an accurate result in the limit of the quasi-Ising chain.
DEFF Research Database (Denmark)
Manning, Stephan; Larsen, Marcus M.; Bharati, Pratyush
2013-01-01
This article examines antecedents and performance implications of global delivery models (GDMs) in global business services. GDMs require geographically distributed operations to exploit both proximity to clients and time-zone spread for efficient service delivery. We propose and empirically show...
Železný, J.
2017-01-10
One of the main obstacles that prevents practical applications of antiferromagnets is the difficulty of manipulating the magnetic order parameter. Recently, following the theoretical prediction [J. Železný, Phys. Rev. Lett. 113, 157201 (2014)]PRLTAO0031-900710.1103/PhysRevLett.113.157201, the electrical switching of magnetic moments in an antiferromagnet was demonstrated [P. Wadley, Science 351, 587 (2016)]SCIEAS0036-807510.1126/science.aab1031. The switching is due to the so-called spin-orbit torque, which has been extensively studied in ferromagnets. In this phenomena a nonequilibrium spin-polarization exchange coupled to the ordered local moments is induced by current, hence exerting a torque on the order parameter. Here we give a general systematic analysis of the symmetry of the spin-orbit torque in locally and globally noncentrosymmetric crystals. We study when the symmetry allows for a nonzero torque, when is the torque effective, and its dependence on the applied current direction and orientation of magnetic moments. For comparison, we consider both antiferromagnetic and ferromagnetic orders. In two representative model crystals we perform microscopic calculations of the spin-orbit torque to illustrate its symmetry properties and to highlight conditions under which the spin-orbit torque can be efficient for manipulating antiferromagnetic moments.
Železný , J.; Gao, H.; Manchon, Aurelien; Freimuth, Frank; Mokrousov, Yuriy; Zemen, J.; Mašek, J.; Sinova, Jairo; Jungwirth, T.
2017-01-01
One of the main obstacles that prevents practical applications of antiferromagnets is the difficulty of manipulating the magnetic order parameter. Recently, following the theoretical prediction [J. Železný, Phys. Rev. Lett. 113, 157201 (2014)]PRLTAO0031-900710.1103/PhysRevLett.113.157201, the electrical switching of magnetic moments in an antiferromagnet was demonstrated [P. Wadley, Science 351, 587 (2016)]SCIEAS0036-807510.1126/science.aab1031. The switching is due to the so-called spin-orbit torque, which has been extensively studied in ferromagnets. In this phenomena a nonequilibrium spin-polarization exchange coupled to the ordered local moments is induced by current, hence exerting a torque on the order parameter. Here we give a general systematic analysis of the symmetry of the spin-orbit torque in locally and globally noncentrosymmetric crystals. We study when the symmetry allows for a nonzero torque, when is the torque effective, and its dependence on the applied current direction and orientation of magnetic moments. For comparison, we consider both antiferromagnetic and ferromagnetic orders. In two representative model crystals we perform microscopic calculations of the spin-orbit torque to illustrate its symmetry properties and to highlight conditions under which the spin-orbit torque can be efficient for manipulating antiferromagnetic moments.
Restrictions on modeling spin injection by resistor networks
Rashba, Emmanuel
2008-01-01
Because of the technical difficulties of solving spin transport equations in inhomogeneous systems, different resistor networks are widely applied for modeling spin transport. By comparing an analytical solution for spin injection across a ferromagnet - paramagnet junction with a resistor model approach, its essential limitations stemming from inhomogeneous spin populations are clarified.
Modeling spin magnetization transport in a spatially varying magnetic field
International Nuclear Information System (INIS)
Picone, Rico A.R.; Garbini, Joseph L.; Sidles, John A.
2015-01-01
We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]). - Highlights: • A framework for modeling the transport of conserved magnetic and thermodynamic quantities in any spatial configuration. • A thermodynamically grounded model of spin magnetization transport valid in new regimes, including high-polarization. • Analysis of the separative quality of
Modeling spin magnetization transport in a spatially varying magnetic field
Energy Technology Data Exchange (ETDEWEB)
Picone, Rico A.R., E-mail: rpicone@stmartin.edu [Department of Mechanical Engineering, University of Washington, Seattle (United States); Garbini, Joseph L. [Department of Mechanical Engineering, University of Washington, Seattle (United States); Sidles, John A. [Department of Orthopædics, University of Washington, Seattle (United States)
2015-01-15
We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]). - Highlights: • A framework for modeling the transport of conserved magnetic and thermodynamic quantities in any spatial configuration. • A thermodynamically grounded model of spin magnetization transport valid in new regimes, including high-polarization. • Analysis of the separative quality of
International Nuclear Information System (INIS)
Hughes, T.J.; Fastook, J.L.
1994-05-01
The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed
Schematic model of nuclear spin excitations
International Nuclear Information System (INIS)
Boucher, P.M.
1990-01-01
A simple model to estimate the strength of spin and nonspin collective states is presented. The model was inspired by early schematic models based on energy-weighted sum rules and is a useful tool for interpreting experimental data without the complexities of realistic microscopic calculations. The strength of collective states is calculated by assuming that a single collective state completely exhausts the energy-weighted sum rule. 19 refs
Distributed MAP in the SpinJa Model Checker
Directory of Open Access Journals (Sweden)
Stefan Vijzelaar
2011-10-01
Full Text Available Spin in Java (SpinJa is an explicit state model checker for the Promela modelling language also used by the SPIN model checker. Designed to be extensible and reusable, the implementation of SpinJa follows a layered approach in which each new layer extends the functionality of the previous one. While SpinJa has preliminary support for shared-memory model checking, it did not yet support distributed-memory model checking. This tool paper presents a distributed implementation of a maximal accepting predecessors (MAP search algorithm on top of SpinJa.
On spinfoam models in large spin regime
International Nuclear Information System (INIS)
Han, Muxin
2014-01-01
We study the semiclassical behavior of Lorentzian Engle–Pereira–Rovelli–Livine (EPRL) spinfoam model, by taking into account the sum over spins in the large spin regime. We also employ the method of stationary phase analysis with parameters and the so-called, almost analytic machinery, in order to find the asymptotic behavior of the contributions from all possible large spin configurations in the spinfoam model. The spins contributing the sum are written as J f = λj f , where λ is a large parameter resulting in an asymptotic expansion via stationary phase approximation. The analysis shows that at least for the simplicial Lorentzian geometries (as spinfoam critical configurations), they contribute the leading order approximation of spinfoam amplitude only when their deficit angles satisfy γ Θ-ring f ≤λ −1/2 mod 4πZ. Our analysis results in a curvature expansion of the semiclassical low energy effective action from the spinfoam model, where the UV modifications of Einstein gravity appear as subleading high-curvature corrections. (paper)
Effective Hamiltonian for 2-dimensional arbitrary spin Ising model
International Nuclear Information System (INIS)
Sznajd, J.; Polska Akademia Nauk, Wroclaw. Inst. Niskich Temperatur i Badan Strukturalnych)
1983-08-01
The method of the reduction of the generalized arbitrary-spin 2-dimensional Ising model to spin-half Ising model is presented. The method is demonstrated in detail by calculating the effective interaction constants to the third order in cumulant expansion for the triangular spin-1 Ising model (the Blume-Emery-Griffiths model). (author)
GPGPU Parallel SPIN Model Checker
National Aeronautics and Space Administration — Model Checking is a powerful technique used to verify that a system does not violate its intended behavior. While this is very useful in proving the robustness of a...
Mean field models for spin glasses
Talagrand, Michel
2011-01-01
This is a new, completely revised, updated and enlarged edition of the author's Ergebnisse vol. 46: "Spin Glasses: A Challenge for Mathematicians". This new edition will appear in two volumes, the present first volume presents the basic results and methods, the second volume is expected to appear in 2011. In the eighties, a group of theoretical physicists introduced several models for certain disordered systems, called "spin glasses". These models are simple and rather canonical random structures, of considerable interest for several branches of science (statistical physics, neural networks and computer science). The physicists studied them by non-rigorous methods and predicted spectacular behaviors. This book introduces in a rigorous manner this exciting new area to the mathematically minded reader. It requires no knowledge whatsoever of any physics. The first volume of this new and completely rewritten edition presents six fundamental models and the basic techniques to study them.
Regionalizing global climate models
Pitman, A.J.; Arneth, A.; Ganzeveld, L.N.
2012-01-01
Global climate models simulate the Earth's climate impressively at scales of continents and greater. At these scales, large-scale dynamics and physics largely define the climate. At spatial scales relevant to policy makers, and to impacts and adaptation, many other processes may affect regional and
Parisi function for two spin glass models
International Nuclear Information System (INIS)
Sibani, P.; Hertz, J.A.
1984-01-01
The probability distribution function P(q) for the overlap of pairs of metastable states and the associated Parisi order function q(x) are calculated exactly at zero temperature for two simple models. The first is a chain in which each spin interacts randomly with the sum of all the spins between it and one end of the chain; the second is an infinite-range limit of a spin glass version of Dyson's hierarchical model. Both have nontrivial overlap distributions: In the first case the problem reduces to a variable-step-length random walk problem, leading to q(x)=sin(πx). In the second model P(q) can be calculated by a simple recursion relation which generates devil's staircase structure in q(x). If the fraction p of antiferromagnetic bonds is less than 1/√2, the staircase is complete and the fractal dimensionality of the complement of the domain where q(x) is flat is log 2/log (1/p 2 ). In both models the space of metastable states can be described in terms of Cayley trees, which however have a different physical interpretation than in the S.K. model. (orig.)
Ladder physics in the spin fermion model
Tsvelik, A. M.
2017-05-01
A link is established between the spin fermion (SF) model of the cuprates and the approach based on the analogy between the physics of doped Mott insulators in two dimensions and the physics of fermionic ladders. This enables one to use nonperturbative results derived for fermionic ladders to move beyond the large-N approximation in the SF model. It is shown that the paramagnon exchange postulated in the SF model has exactly the right form to facilitate the emergence of the fully gapped d -Mott state in the region of the Brillouin zone at the hot spots of the Fermi surface. Hence, the SF model provides an adequate description of the pseudogap.
Werner, A.; Sanderson, M.; Hand, W.; Blyth, A.; Groenemeijer, P.; Kunz, M.; Puskeiler, M.; Saville, G.; Michel, G.
2012-04-01
Hail risk models are rare for the insurance industry. This is opposed to the fact that average annual hail losses can be large and hail dominates losses for many motor portfolios worldwide. Insufficient observational data, high spatio-temporal variability and data inhomogenity have hindered creation of credible models so far. In January 2012, a selected group of hail experts met at Willis in London in order to discuss ways to model hail risk at various scales. Discussions aimed at improving our understanding of hail occurrence and severity, and covered recent progress in the understanding of microphysical processes and climatological behaviour and hail vulnerability. The final outcome of the meeting was the formation of a global hail risk model initiative and the launch of a realistic global hail model in order to assess hail loss occurrence and severities for the globe. The following projects will be tackled: Microphysics of Hail and hail severity measures: Understand the physical drivers of hail and hailstone size development in different regions on the globe. Proposed factors include updraft and supercooled liquid water content in the troposphere. What are the thresholds drivers of hail formation around the globe? Hail Climatology: Consider ways to build a realistic global climatological set of hail events based on physical parameters including spatial variations in total availability of moisture, aerosols, among others, and using neural networks. Vulnerability, Exposure, and financial model: Use historical losses and event footprints available in the insurance market to approximate fragility distributions and damage potential for various hail sizes for property, motor, and agricultural business. Propagate uncertainty distributions and consider effects of policy conditions along with aggregating and disaggregating exposure and losses. This presentation provides an overview of ideas and tasks that lead towards a comprehensive global understanding of hail risk for
Spin chain model for correlated quantum channels
Energy Technology Data Exchange (ETDEWEB)
Rossini, Davide [International School for Advanced Studies SISSA/ISAS, via Beirut 2-4, I-34014 Trieste (Italy); Giovannetti, Vittorio; Montangero, Simone [NEST-CNR-INFM and Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa (Italy)], E-mail: monta@sns.it
2008-11-15
We analyze the quality of the quantum information transmission along a correlated quantum channel by studying the average fidelity between input and output states and the average output purity, giving bounds for the entropy of the channel. Noise correlations in the channel are modeled by the coupling of each channel use with an element of a one-dimensional interacting quantum spin chain. Criticality of the environment chain is seen to emerge in the changes of the fidelity and of the purity.
Modeling spin magnetization transport in a spatially varying magnetic field
Picone, Rico A. R.; Garbini, Joseph L.; Sidles, John A.
2015-01-01
We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]).
Quasi spin pairing and the structure of the Lipkin model
International Nuclear Information System (INIS)
Cambiaggio, M.C.; Plastino, A.
1978-01-01
By introducing the concepts of quasi-spin pairing and quasi-spin seniority, the Lipkin model is extended to a variable number of particles. The properties of quasi-spin pairing are seen to be quite similar to those of ordinary pairing. The quasi-spin seniority allows one to obtain a simple classification of excited multiplets. A 'pairing plus monopole' model is studied in connection with the Hartree-Fock theory. (orig.) [de
The spin dependent odderon in the diquark model
Energy Technology Data Exchange (ETDEWEB)
Szymanowski, Lech [National Centre for Nuclear Research (NCBJ), Warsaw (Poland); Zhou, Jian, E-mail: jzhou@sdu.edu.cn [School of Physics, & Key Laboratory of Particle Physics and Particle Irradiation (MOE), Shandong University, Jinan, Shandong 250100 (China); Nikhef and Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, NL-1081 HV Amsterdam (Netherlands)
2016-09-10
In this short note, we report a di-quark model calculation for the spin dependent odderon and demonstrate that the asymmetrical color source distribution in the transverse plane of a transversely polarized hadron plays an essential role in yielding the spin dependent odderon. This calculation confirms the earlier finding that the spin dependent odderon is closely related to the parton orbital angular momentum.
The spin-s quantum Heisenberg ferromagnetic models in the physical magnon theory
International Nuclear Information System (INIS)
Liu, B.-G.; Pu, F.-C.
2001-01-01
The spin-s quantum Heisenberg ferromagnetic model is investigated in the physical magnon theory. The effect of the extra unphysical magnon states on every site is completely removed in the magnon Hamiltonian and during approximation procedure so that the condition †n i a n i >=0(n≥2s+1) is rigorously satisfied. The physical multi-magnon occupancy †n i a n i >(1≤n≤2s) is proportional to T 3n/2 at low temperature and is equivalent to 1/(2s+1) at the Curie temperature. The magnetization not only unified but also well-behaved from zero temperature to Curie temperature is obtained in the framework of the magnon theory for the spin-s quantum Heisenberg ferromagnetic model. The ill-behaved magnetizations at high temperature in earlier magnon theories are completely corrected. The relation of magnon (spin wave) theory with spin-operator decoupling theory is clearly understood
Testing proton spin models with polarized beams
International Nuclear Information System (INIS)
Ramsey, G.P.
1991-01-01
We review models for spin-weighted parton distributions in a proton. Sum rules involving the nonsinglet components of the structure function xg 1 p help narrow the range of parameters in these models. The contribution of the γ 5 anomaly term depends on the size of the integrated polarized gluon distribution and experimental predictions depend on its size. We have proposed three models for the polarized gluon distributions, whose range is considerable. These model distributions give an overall range is considerable. These model distributions give an overall range of parameters that can be tested with polarized beam experiments. These are discussed with regard to specific predictions for polarized beam experiments at energies typical of UNK
Spin foam models for quantum gravity
International Nuclear Information System (INIS)
Perez, Alejandro
2003-01-01
In this topical review, we review the present status of the spin foam formulation of non-perturbative (background-independent) quantum gravity. The topical review is divided into two parts. In the first part, we present a general introduction to the main ideas emphasizing their motivation from various perspectives. Riemannian three-dimensional gravity is used as a simple example to illustrate conceptual issues and the main goals of the approach. The main features of the various existing models for four-dimensional gravity are also presented here. We conclude with a discussion of important questions to be addressed in four dimensions (gauge invariance, discretization independence, etc). In the second part, we concentrate on the definition of the Barrett-Crane model. We present the main results obtained in this framework from a critical perspective. Finally, we review the combinatorial formulation of spin foam models based on the dual group field theory technology. We present the Barrett-Crane model in this framework and review the finiteness results obtained for both its Riemannian and its Lorentzian variants. (topical review)
Stochastic model of the spinning electron
International Nuclear Information System (INIS)
Simaciu, I.; Borsos, Z.
2002-01-01
In Stochastic Electrodynamics (SED) it is demonstrated that electrostatic interaction is the result of the scattering of the Classical Zero-Point Field (CZPF) background by the charged particles. In such models, the electron is modelled as a two-dimensional oscillator, which interacts with the electric component of the CZPF background. The electron with spin is not only an electric monopole but also a magnetic dipole. The interaction of the spin electron with the CZPF background is not only electric but also magnetic. We calculate the scattering cross-section of magnetic dipole in the situation when a magnetic field, variable in time B arrow = B 0 arrow sin ωt, acts over the rigid magnetic dipole given by the symmetry of the model. The cross-section of a magnetic dipole σ m must be equal to the cross-section of an electric monopole σ e . This equality between σ m and σ e cross-sections is motivated, too, by the fact that, in the model of the two-dimensional oscillator, the electric charge q e has the motion speed c. (authors)
Ladder physics in the spin fermion model
International Nuclear Information System (INIS)
Tsvelik, A. M.
2017-01-01
A link is established between the spin fermion (SF) model of the cuprates and the approach based on the analogy between the physics of doped Mott insulators in two dimensions and the physics of fermionic ladders. This enables one to use nonperturbative results derived for fermionic ladders to move beyond the large-N approximation in the SF model. Here, it is shown that the paramagnon exchange postulated in the SF model has exactly the right form to facilitate the emergence of the fully gapped d-Mott state in the region of the Brillouin zone at the hot spots of the Fermi surface. Hence, the SF model provides an adequate description of the pseudogap.
Low spin models for higher-spin Lagrangians
Czech Academy of Sciences Publication Activity Database
Francia, Dario
2011-01-01
Roč. 2011, č. 188 (2011), s. 94-105 ISSN 0375-9687. [International Conference on String Field Theory and Related Aspects (SFT2010). Kyoto, 18.10.2010-22.10.2010] Grant - others:EUROHORC and ESF(XE) EYI/07/E010 Institutional research plan: CEZ:AV0Z10100502 Keywords : higher spin theories * Maxwell's equations * open string theory Subject RIV: BF - Elementary Particles and High Energy Physics Impact factor: 1.063, year: 2011 http://ptp.ipap.jp/link?PTPS/188/94/
Exact sampling hardness of Ising spin models
Fefferman, B.; Foss-Feig, M.; Gorshkov, A. V.
2017-09-01
We study the complexity of classically sampling from the output distribution of an Ising spin model, which can be implemented naturally in a variety of atomic, molecular, and optical systems. In particular, we construct a specific example of an Ising Hamiltonian that, after time evolution starting from a trivial initial state, produces a particular output configuration with probability very nearly proportional to the square of the permanent of a matrix with arbitrary integer entries. In a similar spirit to boson sampling, the ability to sample classically from the probability distribution induced by time evolution under this Hamiltonian would imply unlikely complexity theoretic consequences, suggesting that the dynamics of such a spin model cannot be efficiently simulated with a classical computer. Physical Ising spin systems capable of achieving problem-size instances (i.e., qubit numbers) large enough so that classical sampling of the output distribution is classically difficult in practice may be achievable in the near future. Unlike boson sampling, our current results only imply hardness of exact classical sampling, leaving open the important question of whether a much stronger approximate-sampling hardness result holds in this context. The latter is most likely necessary to enable a convincing experimental demonstration of quantum supremacy. As referenced in a recent paper [A. Bouland, L. Mancinska, and X. Zhang, in Proceedings of the 31st Conference on Computational Complexity (CCC 2016), Leibniz International Proceedings in Informatics (Schloss Dagstuhl-Leibniz-Zentrum für Informatik, Dagstuhl, 2016)], our result completes the sampling hardness classification of two-qubit commuting Hamiltonians.
A low-temperature derivation of spin-spin exchange in Kondo lattice model
International Nuclear Information System (INIS)
Feng Szeshiang; Mochena, Mogus
2005-01-01
Using Hubbard-Stratonovich transformation and drone-fermion representations for spin-12 and for spin-32, which is presented for the first time, we make a path-integral formulation of the Kondo lattice model. In the case of weak coupling and low temperature, the functional integral over conduction fermions can be approximated to the quadratic order and this gives the well-known RKKY interaction. In the case of strong coupling, the same quadratic approximation leads to an effective local spin-spin interaction linear in hopping energy t
A low-temperature derivation of spin-spin exchange in Kondo lattice model
Energy Technology Data Exchange (ETDEWEB)
Feng Szeshiang [Physics Department, Florida A and M University, Tallahassee, FL 32307 (United States)]. E-mail: shixiang.feng@famu.edu; Mochena, Mogus [Physics Department, Florida A and M University, Tallahassee, FL 32307 (United States)
2005-11-01
Using Hubbard-Stratonovich transformation and drone-fermion representations for spin-12 and for spin-32, which is presented for the first time, we make a path-integral formulation of the Kondo lattice model. In the case of weak coupling and low temperature, the functional integral over conduction fermions can be approximated to the quadratic order and this gives the well-known RKKY interaction. In the case of strong coupling, the same quadratic approximation leads to an effective local spin-spin interaction linear in hopping energy t.
Williams, P.; Huddelston, M.; Michel, G.; Thompson, S.; Heynert, K.; Pickering, C.; Abbott Donnelly, I.; Fewtrell, T.; Galy, H.; Sperna Weiland, F.; Winsemius, H.; Weerts, A.; Nixon, S.; Davies, P.; Schiferli, D.
2012-04-01
Recently, a Global Flood Model (GFM) initiative has been proposed by Willis, UK Met Office, Esri, Deltares and IBM. The idea is to create a global community platform that enables better understanding of the complexities of flood risk assessment to better support the decisions, education and communication needed to mitigate flood risk. The GFM will provide tools for assessing the risk of floods, for devising mitigation strategies such as land-use changes and infrastructure improvements, and for enabling effective pre- and post-flood event response. The GFM combines humanitarian and commercial motives. It will benefit: - The public, seeking to preserve personal safety and property; - State and local governments, seeking to safeguard economic activity, and improve resilience; - NGOs, similarly seeking to respond proactively to flood events; - The insurance sector, seeking to understand and price flood risk; - Large corporations, seeking to protect global operations and supply chains. The GFM is an integrated and transparent set of modules, each composed of models and data. For each module, there are two core elements: a live "reference version" (a worked example) and a framework of specifications, which will allow development of alternative versions. In the future, users will be able to work with the reference version or substitute their own models and data. If these meet the specification for the relevant module, they will interoperate with the rest of the GFM. Some "crowd-sourced" modules could even be accredited and published to the wider GFM community. Our intent is to build on existing public, private and academic work, improve local adoption, and stimulate the development of multiple - but compatible - alternatives, so strengthening mankind's ability to manage flood impacts. The GFM is being developed and managed by a non-profit organization created for the purpose. The business model will be inspired from open source software (eg Linux): - for non-profit usage
Sparks, R. S. J.; Loughlin, S. C.; Cottrell, E.; Valentine, G.; Newhall, C.; Jolly, G.; Papale, P.; Takarada, S.; Crosweller, S.; Nayembil, M.; Arora, B.; Lowndes, J.; Connor, C.; Eichelberger, J.; Nadim, F.; Smolka, A.; Michel, G.; Muir-Wood, R.; Horwell, C.
2012-04-01
Over 600 million people live close enough to active volcanoes to be affected when they erupt. Volcanic eruptions cause loss of life, significant economic losses and severe disruption to people's lives, as highlighted by the recent eruption of Mount Merapi in Indonesia. The eruption of Eyjafjallajökull, Iceland in 2010 illustrated the potential of even small eruptions to have major impact on the modern world through disruption of complex critical infrastructure and business. The effects in the developing world on economic growth and development can be severe. There is evidence that large eruptions can cause a change in the earth's climate for several years afterwards. Aside from meteor impact and possibly an extreme solar event, very large magnitude explosive volcanic eruptions may be the only natural hazard that could cause a global catastrophe. GVM is a growing international collaboration that aims to create a sustainable, accessible information platform on volcanic hazard and risk. We are designing and developing an integrated database system of volcanic hazards, vulnerability and exposure with internationally agreed metadata standards. GVM will establish methodologies for analysis of the data (eg vulnerability indices) to inform risk assessment, develop complementary hazards models and create relevant hazards and risk assessment tools. GVM will develop the capability to anticipate future volcanism and its consequences. NERC is funding the start-up of this initiative for three years from November 2011. GVM builds directly on the VOGRIPA project started as part of the GRIP (Global Risk Identification Programme) in 2004 under the auspices of the World Bank and UN. Major international initiatives and partners such as the Smithsonian Institution - Global Volcanism Program, State University of New York at Buffalo - VHub, Earth Observatory of Singapore - WOVOdat and many others underpin GVM.
Theory of spin Hall effect: extension of the Drude model.
Chudnovsky, Eugene M
2007-11-16
An extension of the Drude model is proposed that accounts for the spin and spin-orbit interaction of charge carriers. Spin currents appear due to the combined action of the external electric field, crystal field, and scattering of charge carriers. The expression for the spin Hall conductivity is derived for metals and semiconductors that is independent of the scattering mechanism. In cubic metals, the spin Hall conductivity sigma s and charge conductivity sigma c are related through sigma s=[2pi variant /(3mc2)]sigma2c with m being the bare electron mass. The theoretically computed value is in agreement with experiment.
Mixed spin Ising model with four-spin interaction and random crystal field
International Nuclear Information System (INIS)
Benayad, N.; Ghliyem, M.
2012-01-01
The effects of fluctuations of the crystal field on the phase diagram of the mixed spin-1/2 and spin-1 Ising model with four-spin interactions are investigated within the finite cluster approximation based on a single-site cluster theory. The state equations are derived for the two-dimensional square lattice. It has been found that the system exhibits a variety of interesting features resulting from the fluctuation of the crystal field interactions. In particular, for low mean value D of the crystal field, the critical temperature is not very sensitive to fluctuations and all transitions are of second order for any value of the four-spin interactions. But for relatively high D, the transition temperature depends on the fluctuation of the crystal field, and the system undergoes tricritical behaviour for any strength of the four-spin interactions. We have also found that the model may exhibit reentrance for appropriate values of the system parameters.
Critical properties of a simple spin glass model
International Nuclear Information System (INIS)
Aharony, A.; Imry, Y.
1976-01-01
The Mattis spin glass model is described as following from a particular quenched random solid solution picture, and its zero-field properties are discussed. The random field model is reviewed. The application to the spin glass problem is made and the more general scaling theory presented, and the limitations of the model are discussed
Annealed n-vector p spin model
International Nuclear Information System (INIS)
Taucher, T.; Frankel, N.E.
1992-01-01
A disordered n-vector model with p spin interactions is introduced and studied in mean field theory for the annealed case. The complete solutions for the cases n = 2 and n = 3, is presented and explicit order parameter equations is given for all the stable solutions for arbitrary n. For all n and p was found on stable high temperature phase and one stable low temperature phase. The phase transition is of first order. For n = 2, it is continuous in the order parameters for p ≤ 4 and has a jump discontinuity in the order parameters if p > 4. For n = 3, it has a jump discontinuity in the order parameters for all p. 11 refs., 4 figs
The effect of spin in swing bowling in cricket: model trajectories for spin alone
Robinson, Garry; Robinson, Ian
2015-02-01
In ‘swing’ bowling, as employed by fast and fast-medium bowlers in cricket, back-spin along the line of the seam is normally applied in order to keep the seam vertical and to provide stability against ‘wobble’ of the seam. Whilst spin is normally thought of as primarily being the slow bowler's domain, the spin applied by the swing bowler has the side-effect of generating a lift or Magnus force. This force, depending on the orientation of the seam and hence that of the back-spin, can have a side-ways component as well as the expected vertical ‘lift’ component. The effect of the spin itself, in influencing the trajectory of the fast bowler's delivery, is normally not considered, presumably being thought of as negligible. The purpose of this paper is to investigate, using calculated model trajectories, the amount of side-ways movement due to the spin and to see how this predicted movement compares with the total observed side-ways movement. The size of the vertical lift component is also estimated. It is found that, although the spin is an essential part of the successful swing bowler's delivery, the amount of side-ways movement due to the spin itself amounts to a few centimetres or so, and is therefore small, but perhaps not negligible, compared to the total amount of side-ways movement observed. The spin does, however, provide a considerable amount of lift compared to the equivalent delivery bowled without spin, altering the point of pitching by up to 3 m, a very large amount indeed. Thus, for example, bowling a ball with the seam pointing directly down the pitch and not designed to swing side-ways at all, but with the amount of back-spin varied, could provide a very powerful additional weapon in the fast bowler's arsenal. So-called ‘sling bowlers’, who use a very low arm action, can take advantage of spin since effectively they can apply side-spin to the ball, giving rise to a large side-ways movement, ˜ 20{}^\\circ cm or more, which certainly is
Spherical 2+p spin-glass model: An exactly solvable model for glass to spin-glass transition
International Nuclear Information System (INIS)
Crisanti, A.; Leuzzi, L.
2004-01-01
We present the full phase diagram of the spherical 2+p spin-glass model with p≥4. The main outcome is the presence of a phase with both properties of full replica symmetry breaking phases of discrete models, e.g., the Sherrington-Kirkpatrick model, and those of one replica symmetry breaking. This phase has a finite complexity which leads to different dynamic and static properties. The phase diagram is rich enough to allow the study of different kinds of glass to spin glass and spin glass to spin glass phase transitions
(Non-) Gibbsianness and Phase Transitions in Random Lattice Spin Models
Külske, C.
1999-01-01
We consider disordered lattice spin models with finite-volume Gibbs measures µΛ[η](dσ). Here σ denotes a lattice spin variable and η a lattice random variable with product distribution P describing the quenched disorder of the model. We ask: when will the joint measures limΛ↑Zd P(dη)µΛ[η](dσ) be
STOCHASTIC MODEL OF THE SPIN DISTRIBUTION OF DARK MATTER HALOS
Energy Technology Data Exchange (ETDEWEB)
Kim, Juhan [Center for Advanced Computation, Korea Institute for Advanced Study, Heogiro 85, Seoul 130-722 (Korea, Republic of); Choi, Yun-Young [Department of Astronomy and Space Science, Kyung Hee University, Gyeonggi 446-701 (Korea, Republic of); Kim, Sungsoo S.; Lee, Jeong-Eun [School of Space Research, Kyung Hee University, Gyeonggi 446-701 (Korea, Republic of)
2015-09-15
We employ a stochastic approach to probing the origin of the log-normal distributions of halo spin in N-body simulations. After analyzing spin evolution in halo merging trees, it was found that a spin change can be characterized by a stochastic random walk of angular momentum. Also, spin distributions generated by random walks are fairly consistent with those directly obtained from N-body simulations. We derived a stochastic differential equation from a widely used spin definition and measured the probability distributions of the derived angular momentum change from a massive set of halo merging trees. The roles of major merging and accretion are also statistically analyzed in evolving spin distributions. Several factors (local environment, halo mass, merging mass ratio, and redshift) are found to influence the angular momentum change. The spin distributions generated in the mean-field or void regions tend to shift slightly to a higher spin value compared with simulated spin distributions, which seems to be caused by the correlated random walks. We verified the assumption of randomness in the angular momentum change observed in the N-body simulation and detected several degrees of correlation between walks, which may provide a clue for the discrepancies between the simulated and generated spin distributions in the voids. However, the generated spin distributions in the group and cluster regions successfully match the simulated spin distribution. We also demonstrated that the log-normality of the spin distribution is a natural consequence of the stochastic differential equation of the halo spin, which is well described by the Geometric Brownian Motion model.
Global symplectic structure-preserving integrators for spinning compact binaries
Zhong, Shuang-Ying; Wu, Xin; Liu, San-Qiu; Deng, Xin-Fa
2010-12-01
This paper deals mainly with the application of the second-order symplectic implicit midpoint rule and its symmetric compositions to a post-Newtonian Hamiltonian formulation with canonical spin variables in relativistic compact binaries. The midpoint rule, as a basic algorithm, is directly used to integrate the completely canonical Hamiltonian system. On the other hand, there are symmetric composite methods based on a splitting of the Hamiltonian into two parts: the Newtonian part associated with a Kepler motion, and a perturbation part involving the orbital post-Newtonian and spin contributions, where the Kepler flow has an analytic solution and the perturbation can be calculated by the midpoint rule. An example is the second-order mixed leapfrog symplectic integrator with one stage integration of the perturbation flow and two semistage computations of the Kepler flow at every integration step. Also, higher-order composite methods such as the Forest-Ruth fourth-order symplectic integrator and its optimized algorithm are applicable. Various numerical tests including simulations of chaotic orbits show that the mixed leapfrog integrator is always superior to the midpoint rule in energy accuracy, while both of them are almost equivalent in computational efficiency. Particularly, the optimized fourth-order algorithm compared with the mixed leapfrog scheme provides good precision and needs no expensive additional computational time. As a result, it is worth performing a more detailed and careful examination of the dynamical structure of chaos and order in the parameter windows and phase space of the binary system.
Spin-Wave Wave Function for Quantum Spin Models : Condensed Matter and Statistical Physics
Franjo, FRANJIC; Sandro, SORELLA; Istituto Nazionale di Fisica della Materia International School for Advance Studies; Istituto Nazionale di Fisica della Materia International School for Advance Studies
1997-01-01
We present a new approach to determine an accurate variational wave function for general quantum spin models, completely defined by a consistency requirement with the simple and well-known linear spin-wave expansion. With this wave function, it is also possible to obtain the correct behavior of the long distance correlation functions for the 1D S=1/2 antiferromagnet. In 2D the proposed spin-wave wave function represents an excellent approximation to the exact ground state of the S=1.2 XY mode...
Rigorous spin-spin correlation function of Ising model on a special kind of Sierpinski Carpets
International Nuclear Information System (INIS)
Yang, Z.R.
1993-10-01
We have exactly calculated the rigorous spin-spin correlation function of Ising model on a special kind of Sierpinski Carpets (SC's) by means of graph expansion and a combinatorial approach and investigated the asymptotic behaviour in the limit of long distance. The result show there is no long range correlation between spins at any finite temperature which indicates no existence of phase transition and thus finally confirms the conclusion produced by the renormalization group method and other physical arguments. (author). 7 refs, 6 figs
Marzeion, B.; Maussion, F.
2017-12-01
Mountain glaciers are one of the few remaining sub-systems of the global climate system for which no globally applicable, open source, community-driven model exists. Notable examples from the ice sheet community include the Parallel Ice Sheet Model or Elmer/Ice. While the atmospheric modeling community has a long tradition of sharing models (e.g. the Weather Research and Forecasting model) or comparing them (e.g. the Coupled Model Intercomparison Project or CMIP), recent initiatives originating from the glaciological community show a new willingness to better coordinate global research efforts following the CMIP example (e.g. the Glacier Model Intercomparison Project or the Glacier Ice Thickness Estimation Working Group). In the recent past, great advances have been made in the global availability of data and methods relevant for glacier modeling, spanning glacier outlines, automatized glacier centerline identification, bed rock inversion methods, and global topographic data sets. Taken together, these advances now allow the ice dynamics of glaciers to be modeled on a global scale, provided that adequate modeling platforms are available. Here, we present the Open Global Glacier Model (OGGM), developed to provide a global scale, modular, and open source numerical model framework for consistently simulating past and future global scale glacier change. Global not only in the sense of leading to meaningful results for all glaciers combined, but also for any small ensemble of glaciers, e.g. at the headwater catchment scale. Modular to allow combinations of different approaches to the representation of ice flow and surface mass balance, enabling a new kind of model intercomparison. Open source so that the code can be read and used by anyone and so that new modules can be added and discussed by the community, following the principles of open governance. Consistent in order to provide uncertainty measures at all realizable scales.
Minimal model of spin-transfer torque and spin pumping caused by the spin Hall Effect
Czech Academy of Sciences Publication Activity Database
Chen, W.; Sigrist, M.; Sinova, Jairo; Manske, D.
2016-01-01
Roč. 115, č. 21 (2016), 1-5, č. článku 217203. ISSN 0031-9007 Institutional support: RVO:68378271 Keywords : spintronics * spin Hall effect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 8.462, year: 2016
Kinetic models in spin chemistry. 1. The hyperfine interaction
DEFF Research Database (Denmark)
Mojaza, M.; Pedersen, J. B.
2012-01-01
Kinetic models for quantum systems are quite popular due to their simplicity, although they are difficult to justify. We show that the transformation from quantum to kinetic description can be done exactly for the hyperfine interaction of one nuclei with arbitrary spin; more spins are described w...... induced enhancement of the reaction yield. (C) 2012 Elsevier B.V. All rights reserved....
DEFF Research Database (Denmark)
Manning, Stephan; Møller Larsen, Marcus; Bharati, Pratyush
-zone spread allowing for 24/7 service delivery and access to resources. Based on comprehensive data we show that providers are likely to establish GDM configurations when clients value access to globally distributed talent pools and speed of service delivery, and in particular when services are highly...
DEFF Research Database (Denmark)
Manning, Stephan; Møller Larsen, Marcus; Bharati, Pratyush M.
2015-01-01
antecedents and contingencies of setting up GDM structures. Based on comprehensive data we show that providers are likely to establish GDM location configurations when clients value access to globally distributed talent and speed of service delivery, in particular when services are highly commoditized...
The proton's spin: A quark model perspective
International Nuclear Information System (INIS)
Close, F.E.
1989-01-01
Magnetic moments and g A /g V provide information on the correlations among quark spins and flavors in the proton. I compare this information with the deep inelastic polarized data from EMC which has been claimed to show that very little of the proton's spin is due to the quarks. The possibility that there is significant polarization of strange quarks within protons is discussed. 38 refs
International Nuclear Information System (INIS)
Li Jun; Wei Guozhu; Du An
2005-01-01
The compensation and critical behaviors of a mixed spin-2 and spin-12 Heisenberg ferrimagnetic system on a square lattice are investigated theoretically by the two-time Green's function technique, which takes into account the quantum nature of Heisenberg spins. The model can be relevant for understanding the magnetic behavior of the new class of organometallic ferromagnetic materials that exhibit spontaneous magnetic properties at room temperature. We carry out the calculation of the sublattice magnetizations and the spin-wave spectra of the ground state. In particular, we have studied the effects of the nearest, next-nearest-neighbor interactions, the crystal field and the external magnetic field on the compensation temperature and the critical temperature. When only the nearest-neighbor interactions and the crystal field are included, no compensation temperature exists; when the next-nearest-neighbor interaction between spin-12 is taken into account and exceeds a minimum value, a compensation point appears and it is basically unchanged for other parameters in Hamiltonian fixed. The next-nearest-neighbor interactions between spin-2 and the external magnetic field have the effects of changing the compensation temperature and there is a narrow range of parameters of the Hamiltonian for which the model has the compensation temperatures and compensation temperature exists only for a small value of them
Global nuclear material control model
International Nuclear Information System (INIS)
Dreicer, J.S.; Rutherford, D.A.
1996-01-01
The nuclear danger can be reduced by a system for global management, protection, control, and accounting as part of a disposition program for special nuclear materials. The development of an international fissile material management and control regime requires conceptual research supported by an analytical and modeling tool that treats the nuclear fuel cycle as a complete system. Such a tool must represent the fundamental data, information, and capabilities of the fuel cycle including an assessment of the global distribution of military and civilian fissile material inventories, a representation of the proliferation pertinent physical processes, and a framework supportive of national or international perspective. They have developed a prototype global nuclear material management and control systems analysis capability, the Global Nuclear Material Control (GNMC) model. The GNMC model establishes the framework for evaluating the global production, disposition, and safeguards and security requirements for fissile nuclear material
Ground state properties of a spin chain within Heisenberg model with a single lacking spin site
International Nuclear Information System (INIS)
Mebrouki, M.
2011-01-01
The ground state and first excited state energies of an antiferromagnetic spin-1/2 chain with and without a single lacking spin site are computed using exact diagonalization method, within the Heisenberg model. In order to keep both parts of a spin chain with a lacking site connected, next nearest neighbors interactions are then introduced. Also, the Density Matrix Renormalization Group (DMRG) method is used, to investigate ground state energies of large system sizes; which permits us to inquire about the effect of large system sizes on energies. Other quantum quantities such as fidelity and correlation functions are also studied and compared in both cases. - Research highlights: → In this paper we compute ground state and first excited state energies of a spin chain with and without a lacking spin site. The next nearest neighbors are introduced with the antiferromagnetic Heisenberg spin-half. → Exact diagonalization is used for small systems, where DMRG method is used to compute energies for large systems. Other quantities like quantum fidelity and correlation are also computed. → Results are presented in figures with comments. → E 0 /N is computed in a function of N for several values of J 2 and for both systems. First excited energies are also investigated.
Ground states of a spin-boson model
International Nuclear Information System (INIS)
Amann, A.
1991-01-01
Phase transition with respect to ground states of a spin-boson Hamiltonian are investigated. The spin-boson model under discussion consists of one spin and infinitely many bosons with a dipole-type coupling. It is shown that the order parameter of the model vanishes with respect to arbitrary ground states if it vanishes with respect to ground states obtained as (biased) temperature to zero limits of thermic equilibrium states. The ground states of the latter special type have been investigated by H. Spohn. Spohn's respective phase diagrams are therefore valid for arbitrary ground states. Furthermore, disjointness of ground states in the broken symmetry regime is examined
Analytic Models for Sunlight Charging of a Rapidly Spinning Satellite
National Research Council Canada - National Science Library
Tautz, Maurice
2003-01-01
... photoelectrons can be blocked by local potential barriers. In this report, we discuss two analytic models for sunlight charging of a rapidly spinning spherical satellite, both of which are based on blocked photoelectron currents...
Magnetic and electric order in the spin-1/2 XX model with three-spin interactions
Energy Technology Data Exchange (ETDEWEB)
Thakur, Pradeep; Durganandini, P. [Department of Physics, University of Pune, Ganeshkhind, Pune - 411007 (India)
2016-05-23
We study the spin-1/2 XX model in the presence of three-spin interactions of the XZX+YZY and XZY-YZX types. We solve the problem exactly and show that there is both finite magnetization and electric polarization for low non-zero strengths of the three-spin interactions.
Boson-mediated quantum spin simulators in transverse fields: X Y model and spin-boson entanglement
Wall, Michael L.; Safavi-Naini, Arghavan; Rey, Ana Maria
2017-01-01
The coupling of spins to long-wavelength bosonic modes is a prominent means to engineer long-range spin-spin interactions, and has been realized in a variety of platforms, such as atoms in optical cavities and trapped ions. To date, much of the experimental focus has been on the realization of long-range Ising models, but generalizations to other spin models are highly desirable. In this work, we explore a previously unappreciated connection between the realization of an X Y model by off-resonant driving of a single sideband of boson excitation (i.e., a single-beam Mølmer-Sørensen scheme) and a boson-mediated Ising simulator in the presence of a transverse field. In particular, we show that these two schemes have the same effective Hamiltonian in suitably defined rotating frames, and analyze the emergent effective X Y spin model through a truncated Magnus series and numerical simulations. In addition to X Y spin-spin interactions that can be nonperturbatively renormalized from the naive Ising spin-spin coupling constants, we find an effective transverse field that is dependent on the thermal energy of the bosons, as well as other spin-boson couplings that cause spin-boson entanglement not to vanish at any time. In the case of a boson-mediated Ising simulator with transverse field, we discuss the crossover from transverse field Ising-like to X Y -like spin behavior as a function of field strength.
Spin Glass Models of Syntax and Language Evolution
Siva, Karthik; Tao, Jim; Marcolli, Matilde
2015-01-01
Using the SSWL database of syntactic parameters of world languages, and the MIT Media Lab data on language interactions, we construct a spin glass model of language evolution. We treat binary syntactic parameters as spin states, with languages as vertices of a graph, and assigned interaction energies along the edges. We study a rough model of syntax evolution, under the assumption that a strong interaction energy tends to cause parameters to align, as in the case of ferromagnetic materials. W...
Continuum model for chiral induced spin selectivity in helical molecules
Energy Technology Data Exchange (ETDEWEB)
Medina, Ernesto [Centro de Física, Instituto Venezolano de Investigaciones Científicas, 21827, Caracas 1020 A (Venezuela, Bolivarian Republic of); Groupe de Physique Statistique, Institut Jean Lamour, Université de Lorraine, 54506 Vandoeuvre-les-Nancy Cedex (France); Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287 (United States); González-Arraga, Luis A. [IMDEA Nanoscience, Cantoblanco, 28049 Madrid (Spain); Finkelstein-Shapiro, Daniel; Mujica, Vladimiro [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287 (United States); Berche, Bertrand [Centro de Física, Instituto Venezolano de Investigaciones Científicas, 21827, Caracas 1020 A (Venezuela, Bolivarian Republic of); Groupe de Physique Statistique, Institut Jean Lamour, Université de Lorraine, 54506 Vandoeuvre-les-Nancy Cedex (France)
2015-05-21
A minimal model is exactly solved for electron spin transport on a helix. Electron transport is assumed to be supported by well oriented p{sub z} type orbitals on base molecules forming a staircase of definite chirality. In a tight binding interpretation, the spin-orbit coupling (SOC) opens up an effective π{sub z} − π{sub z} coupling via interbase p{sub x,y} − p{sub z} hopping, introducing spin coupled transport. The resulting continuum model spectrum shows two Kramers doublet transport channels with a gap proportional to the SOC. Each doubly degenerate channel satisfies time reversal symmetry; nevertheless, a bias chooses a transport direction and thus selects for spin orientation. The model predicts (i) which spin orientation is selected depending on chirality and bias, (ii) changes in spin preference as a function of input Fermi level and (iii) back-scattering suppression protected by the SO gap. We compute the spin current with a definite helicity and find it to be proportional to the torsion of the chiral structure and the non-adiabatic Aharonov-Anandan phase. To describe room temperature transport, we assume that the total transmission is the result of a product of coherent steps.
Vector spin modeling for magnetic tunnel junctions with voltage dependent effects
International Nuclear Information System (INIS)
Manipatruni, Sasikanth; Nikonov, Dmitri E.; Young, Ian A.
2014-01-01
Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects
Nonperturbative stochastic method for driven spin-boson model
Orth, Peter P.; Imambekov, Adilet; Le Hur, Karyn
2013-01-01
We introduce and apply a numerically exact method for investigating the real-time dissipative dynamics of quantum impurities embedded in a macroscopic environment beyond the weak-coupling limit. We focus on the spin-boson Hamiltonian that describes a two-level system interacting with a bosonic bath of harmonic oscillators. This model is archetypal for investigating dissipation in quantum systems, and tunable experimental realizations exist in mesoscopic and cold-atom systems. It finds abundant applications in physics ranging from the study of decoherence in quantum computing and quantum optics to extended dynamical mean-field theory. Starting from the real-time Feynman-Vernon path integral, we derive an exact stochastic Schrödinger equation that allows us to compute the full spin density matrix and spin-spin correlation functions beyond weak coupling. We greatly extend our earlier work [P. P. Orth, A. Imambekov, and K. Le Hur, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.82.032118 82, 032118 (2010)] by fleshing out the core concepts of the method and by presenting a number of interesting applications. Methodologically, we present an analogy between the dissipative dynamics of a quantum spin and that of a classical spin in a random magnetic field. This analogy is used to recover the well-known noninteracting-blip approximation in the weak-coupling limit. We explain in detail how to compute spin-spin autocorrelation functions. As interesting applications of our method, we explore the non-Markovian effects of the initial spin-bath preparation on the dynamics of the coherence σx(t) and of σz(t) under a Landau-Zener sweep of the bias field. We also compute to a high precision the asymptotic long-time dynamics of σz(t) without bias and demonstrate the wide applicability of our approach by calculating the spin dynamics at nonzero bias and different temperatures.
Yoshitake, Junki; Nasu, Joji; Motome, Yukitoshi
2016-10-07
Experimental identification of quantum spin liquids remains a challenge, as the pristine nature is to be seen in asymptotically low temperatures. We here theoretically show that the precursor of quantum spin liquids appears in the spin dynamics in the paramagnetic state over a wide temperature range. Using the cluster dynamical mean-field theory and the continuous-time quantum Monte Carlo method, which are newly developed in the Majorana fermion representation, we calculate the dynamical spin structure factor, relaxation rate in nuclear magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model whose ground state is a canonical example of the quantum spin liquid. We find that dynamical spin correlations show peculiar temperature and frequency dependence even below the temperature where static correlations saturate. The results provide the experimentally accessible symptoms of the fluctuating fractionalized spins evincing the quantum spin liquids.
Spin-density functional for exchange anisotropic Heisenberg model
International Nuclear Information System (INIS)
Prata, G.N.; Penteado, P.H.; Souza, F.C.; Libero, Valter L.
2009-01-01
Ground-state energies for antiferromagnetic Heisenberg models with exchange anisotropy are estimated by means of a local-spin approximation made in the context of the density functional theory. Correlation energy is obtained using the non-linear spin-wave theory for homogeneous systems from which the spin functional is built. Although applicable to chains of any size, the results are shown for small number of sites, to exhibit finite-size effects and allow comparison with exact-numerical data from direct diagonalization of small chains.
Digital Quantum Simulation of Spin Models with Circuit Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Y. Salathé
2015-06-01
Full Text Available Systems of interacting quantum spins show a rich spectrum of quantum phases and display interesting many-body dynamics. Computing characteristics of even small systems on conventional computers poses significant challenges. A quantum simulator has the potential to outperform standard computers in calculating the evolution of complex quantum systems. Here, we perform a digital quantum simulation of the paradigmatic Heisenberg and Ising interacting spin models using a two transmon-qubit circuit quantum electrodynamics setup. We make use of the exchange interaction naturally present in the simulator to construct a digital decomposition of the model-specific evolution and extract its full dynamics. This approach is universal and efficient, employing only resources that are polynomial in the number of spins, and indicates a path towards the controlled simulation of general spin dynamics in superconducting qubit platforms.
Spin foam models for quantum gravity
Perez, Alejandro
The definition of a quantum theory of gravity is explored following Feynman's path-integral approach. The aim is to construct a well defined version of the Wheeler-Misner- Hawking ``sum over four geometries'' formulation of quantum general relativity (GR). This is done by means of exploiting the similarities between the formulation of GR in terms of tetrad-connection variables (Palatini formulation) and a simpler theory called BF theory. One can go from BF theory to GR by imposing certain constraints on the BF-theory configurations. BF theory contains only global degrees of freedom (topological theory) and it can be exactly quantized á la Feynman introducing a discretization of the manifold. Using the path integral for BF theory we define a path integration for GR imposing the BF-to-GR constraints on the BF measure. The infinite degrees of freedom of gravity are restored in the process, and the restriction to a single discretization introduces a cut- off in the summed-over configurations. In order to capture all the degrees of freedom a sum over discretization is implemented. Both the implementation of the BF-to-GR constraints and the sum over discretizations are obtained by means of the introduction of an auxiliary field theory (AFT). 4-geometries in the path integral for GR are given by the Feynman diagrams of the AFT which is in this sense dual to GR. Feynman diagrams correspond to 2-complexes labeled by unitary irreducible representations of the internal gauge group (corresponding to tetrad rotation in the connection to GR). A model for 4-dimensional Euclidean quantum gravity (QG) is defined which corresponds to a different normalization of the Barrett-Crane model. The model is perturbatively finite; divergences appearing in the Barrett-Crane model are cured by the new normalization. We extend our techniques to the Lorentzian sector, where we define two models for four-dimensional QG. The first one contains only time-like representations and is shown to be
Digital Quantum Simulation of Spin Models with Circuit Quantum Electrodynamics
Salathé, Y.; Mondal, M.; Oppliger, M.; Heinsoo, J.; Kurpiers, P.; Potočnik, A.; Mezzacapo, Antonio; Las Heras García, Urtzi; Lamata Manuel, Lucas; Solano Villanueva, Enrique Leónidas; Filipp, S.; Wallraff, A.
2015-01-01
Systems of interacting quantum spins show a rich spectrum of quantum phases and display interesting many-body dynamics. Computing characteristics of even small systems on conventional computers poses significant challenges. A quantum simulator has the potential to outperform standard computers in calculating the evolution of complex quantum systems. Here, we perform a digital quantum simulation of the paradigmatic Heisenberg and Ising interacting spin models using a two transmon-qubit circuit...
The Global Tsunami Model (GTM)
Lorito, S.; Basili, R.; Harbitz, C. B.; Løvholt, F.; Polet, J.; Thio, H. K.
2017-12-01
The tsunamis occurred worldwide in the last two decades have highlighted the need for a thorough understanding of the risk posed by relatively infrequent but often disastrous tsunamis and the importance of a comprehensive and consistent methodology for quantifying the hazard. In the last few years, several methods for probabilistic tsunami hazard analysis have been developed and applied to different parts of the world. In an effort to coordinate and streamline these activities and make progress towards implementing the Sendai Framework of Disaster Risk Reduction (SFDRR) we have initiated a Global Tsunami Model (GTM) working group with the aim of i) enhancing our understanding of tsunami hazard and risk on a global scale and developing standards and guidelines for it, ii) providing a portfolio of validated tools for probabilistic tsunami hazard and risk assessment at a range of scales, and iii) developing a global tsunami hazard reference model. This GTM initiative has grown out of the tsunami component of the Global Assessment of Risk (GAR15), which has resulted in an initial global model of probabilistic tsunami hazard and risk. Started as an informal gathering of scientists interested in advancing tsunami hazard analysis, the GTM is currently in the process of being formalized through letters of interest from participating institutions. The initiative has now been endorsed by the United Nations International Strategy for Disaster Reduction (UNISDR) and the World Bank's Global Facility for Disaster Reduction and Recovery (GFDRR). We will provide an update on the state of the project and the overall technical framework, and discuss the technical issues that are currently being addressed, including earthquake source recurrence models, the use of aleatory variability and epistemic uncertainty, and preliminary results for a probabilistic global hazard assessment, which is an update of the model included in UNISDR GAR15.
Numerical study of the spin-1 Ashkin-Teller model
International Nuclear Information System (INIS)
Bekhechi, S.; Badehdah, M.; Benyoussef, A.; Ettaki, B.
1998-07-01
Two non perturbative methods by means of the Transfer-Matrix Finite-Size-Scaling (TMFSS) and Monte Carlo (MC) simulations are used to investigate the spin-1 Ashkin-Teller model (A.T.M.). We have obtained rich phase diagrams with first and second order phase transitions with several multicritical points of higher order. Also this model exhibits a new partially ordered phase PO2 which does not exist in the spin-1/2 Ashkin-Teller model (A.T.M.). Finally, the critical behaviour of this model is discussed. (author)
Hydrodynamic description of spin Calogero-Sutherland model
Abanov, Alexander; Kulkarni, Manas; Franchini, Fabio
2009-03-01
We study a non-linear collective field theory for an integrable spin-Calogero-Sutherland model. The hydrodynamic description of this SU(2) model in terms of charge density, charge velocity and spin currents is used to study non-perturbative solutions (solitons) and examine their correspondence with known quantum numbers of elementary excitations [1]. A conventional linear bosonization or harmonic approximation is not sufficient to describe, for example, the physics of spin-charge (non)separation. Therefore, we need this new collective bosonic field description that captures the effects of the band curvature. In the strong coupling limit [2] this model reduces to integrable SU(2) Haldane-Shastry model. We study a non-linear coupling of left and right spin currents which form a Kac-Moody algebra. Our quantum hydrodynamic description for the spin case is an extension for the one found in the spinless version in [3].[3pt] [1] Y. Kato,T. Yamamoto, and M. Arikawa, J. Phys. Soc. Jpn. 66, 1954-1961 (1997).[0pt] [2] A. Polychronakos, Phys Rev Lett. 70,2329-2331(1993).[0pt] [3] A.G.Abanov and P.B. Wiegmann, Phys Rev Lett 95, 076402(2005)
Isoscalar spin-spin interaction within the quasiparticle-phonon nuclear model
International Nuclear Information System (INIS)
Dao Tien Khoa; Ponomarev, V.Yu.; Vdovin, A.I.
1986-01-01
The isoscalar spin-spin interaction constant in the quasiparticle-phonon nuclear model (QPM) has been determined from the available experimental data on the isoscalar 1 + state (E x =5.846 MeV) in 208 Pb. The isoscalar spin-spin interaction turns out to be weaker than the isovector one by an order of magnitude. The cross sections of (e, e') and (p, p') reactions with the excitation of this 1 + -state have been calculated. The QPM gives a good description of the behaviour of (e, e')-cross section at q eff -1 and reproduces absolute value of this cross section with the effective g s -factors weaker than the g s -factors for free nucleon by 20%. The description of the (p, p')-angular distribution of 201 MeV photon inelastic scattering is poorer. The absolute value of the calculated (p, p') cross section overestimates the experimental data by a factor of about 1.4. This is consistent with the quenching factor for (e, e') cross section. The interaction with two-phonon configurations influences very weakly the isoscalar 1 + -level
Spin models for the single molecular magnet Mn12-AC
Al-Saqer, Mohamad A.
2005-11-01
The single molecular magnet (SMM) Mn12-AC attracted the attention of scientists since the discovery of its magnetic hystereses which are accompanied by sudden jumps in magnetic moments at low temperature. Unlike conventional bulk magnets, hysteresis in SMMs is of molecular origin. This qualifies them as candidates for next generation of high density storage media where a molecule which is at most few nanometers in size can be used to store a bit of information. However, the jumps in these hystereses, due to spin tunneling, can lead to undesired loss of information. Mn12-AC molecule contains twelve magnetic ions antiferromagnetically coupled by exchanges leading to S = 10 ground state manifold. The magnetic ions are surrounded by ligands which isolate them magnetically from neighboring molecules. The lowest state of S = 9 manifold is believed to lie at about 40 K above the ground state. Therefore, at low temperatures, the molecule is considered as a single uncoupled moment of spin S = 10. Such model has been used widely to understand phenomena exhibited by the molecule at low temperatures including the tunneling of its spin, while a little attention has been paid for the multi-spin nature of the molecule. Using the 8-spin model, we demonstrate that in order to understand the phenomena of tunneling, a full spin description of the molecule is required. We utilized a calculation scheme where a fraction of energy levels are used in the calculations and the influence of levels having higher energy is neglected. From the dependence of tunnel splittings on the number of states include, we conclude that models based on restricting the number of energy levels (single-spin and 8-spin models) lead to unreliable results of tunnel splitting calculations. To attack the full 12-spin model, we employed the Davidson algorithm to calculated lowest energy levels produced by exchange interactions and single ion anisotropies. The model reproduces the anisotropy properties at low
Spin delocalization phase transition in a correlated electrons model
International Nuclear Information System (INIS)
Huerta, L.
1990-11-01
In a simplified one-site model for correlated electrons systems we show the existence of a phase transition corresponding to spin delocalization. The system becomes a solvable model and zero-dimensional functional techniques are used. (author). 7 refs, 3 figs
3 QP plus rotor model and high spin states
International Nuclear Information System (INIS)
Mathur, Tripti
1995-01-01
Nuclear models are approximate methods to describe certain properties of a large number of nuclei. In this paper details of 3 QP (three quasi particle) plus rotor model and high spin state are discussed. The band head energies for the 3 QP rotational bands for 157 Ho and 159 Tm are also given. 5 refs., 8 figs
Impact of hadronic and nuclear corrections on global analysis of spin-dependent parton distributions
Energy Technology Data Exchange (ETDEWEB)
Jimenez-Delgado, Pedro [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Accardi, Alberto [Hampton University, Hampton, VA (United States); Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Melnitchouk, Wally [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
2014-02-01
We present the first results of a new global next-to-leading order analysis of spin-dependent parton distribution functions from the most recent world data on inclusive polarized deep-inelastic scattering, focusing in particular on the large-x and low-Q^2 regions. By directly fitting polarization asymmetries we eliminate biases introduced by using polarized structure function data extracted under nonuniform assumptions for the unpolarized structure functions. For analysis of the large-x data we implement nuclear smearing corrections for deuterium and 3He nuclei, and systematically include target mass and higher twist corrections to the g_1 and g_2 structure functions at low Q^2. We also explore the effects of Q^2 and W^2 cuts in the data sets, and the potential impact of future data on the behavior of the spin-dependent parton distributions at large x.
Global scale groundwater flow model
Sutanudjaja, Edwin; de Graaf, Inge; van Beek, Ludovicus; Bierkens, Marc
2013-04-01
As the world's largest accessible source of freshwater, groundwater plays vital role in satisfying the basic needs of human society. It serves as a primary source of drinking water and supplies water for agricultural and industrial activities. During times of drought, groundwater sustains water flows in streams, rivers, lakes and wetlands, and thus supports ecosystem habitat and biodiversity, while its large natural storage provides a buffer against water shortages. Yet, the current generation of global scale hydrological models does not include a groundwater flow component that is a crucial part of the hydrological cycle and allows the simulation of groundwater head dynamics. In this study we present a steady-state MODFLOW (McDonald and Harbaugh, 1988) groundwater model on the global scale at 5 arc-minutes resolution. Aquifer schematization and properties of this groundwater model were developed from available global lithological model (e.g. Dürr et al., 2005; Gleeson et al., 2010; Hartmann and Moorsdorff, in press). We force the groundwtaer model with the output from the large-scale hydrological model PCR-GLOBWB (van Beek et al., 2011), specifically the long term net groundwater recharge and average surface water levels derived from routed channel discharge. We validated calculated groundwater heads and depths with available head observations, from different regions, including the North and South America and Western Europe. Our results show that it is feasible to build a relatively simple global scale groundwater model using existing information, and estimate water table depths within acceptable accuracy in many parts of the world.
DISCERNING EXOPLANET MIGRATION MODELS USING SPIN-ORBIT MEASUREMENTS
International Nuclear Information System (INIS)
Morton, Timothy D.; Johnson, John Asher
2011-01-01
We investigate the current sample of exoplanet spin-orbit measurements to determine whether a dominant planet migration channel can be identified, and at what confidence. We use the predictions of Kozai migration plus tidal friction and planet-planet scattering as our misalignment models, and we allow for a fraction of intrinsically aligned systems, explainable by disk migration. Bayesian model comparison demonstrates that the current sample of 32 spin-orbit measurements strongly favors a two-mode migration scenario combining planet-planet scattering and disk migration over a single-mode Kozai migration scenario. Our analysis indicates that between 34% and 76% of close-in planets (95% confidence) migrated via planet-planet scattering. Separately analyzing the subsample of 12 stars with T eff >6250 K-which Winn et al. predict to be the only type of stars to maintain their primordial misalignments-we find that the data favor a single-mode scattering model over Kozai with 85% confidence. We also assess the number of additional hot star spin-orbit measurements that will likely be necessary to provide a more confident model selection, finding that an additional 20-30 measurement has a >50% chance of resulting in a 95% confident model selection, if the current model selection is correct. While we test only the predictions of particular Kozai and scattering migration models in this work, our methods may be used to test the predictions of any other spin-orbit misaligning mechanism.
The SU(2 vertical stroke 3) spin chain sigma model
International Nuclear Information System (INIS)
Hernandez, R.; Lopez, E.
2005-01-01
The one-loop planar dilatation operator of N = 4 supersymmetric Yang-Mills is isomorphic to the hamiltonian of an integrable PSU(2,2 vertical stroke 4) spin chain. We construct the non-linear sigma model describing the continuum limit of the SU(2 vertical stroke 3) subsector of the N = 4 chain. We explicitly identify the spin chain sigma model with the one for a superstring moving in AdS 5 x S 5 with large angular momentum along the five-sphere. (Abstract Copyright [2005], Wiley Periodicals, Inc.)
The exactly solvable spin Sutherland model of BN type and its related spin chain
International Nuclear Information System (INIS)
Basu-Mallick, B.; Finkel, F.; González-López, A.
2013-01-01
We compute the spectrum of the su(m) spin Sutherland model of B N type, including the exact degeneracy of all energy levels. By studying the large coupling constant limit of this model and of its scalar counterpart, we evaluate the partition function of their associated spin chain of Haldane–Shastry type in closed form. With the help of the formula for the partition function thus obtained we study the chain's spectrum, showing that it cannot be obtained as a limiting case of its BC N counterpart. The structure of the partition function also suggests that the spectrum of the Haldane–Shastry spin chain of B N type is equivalent to that of a suitable vertex model, as is the case for its A N−1 counterpart, and that the density of its eigenvalues is normally distributed when the number of sites N tends to infinity. We analyze this last conjecture numerically using again the explicit formula for the partition function, and check its validity for several values of N and m.
On the stochastic dynamics of disordered spin models
International Nuclear Information System (INIS)
Semerjian, G.; Montanari, A.; Cugliandolo, L.F.
2003-09-01
In this article we discuss several aspects of the stochastic dynamics of spin models. The paper has two independent parts. Firstly, we explore a few properties of the multi-point correlations and responses of generic systems evolving in equilibrium with a thermal bath. We propose a fluctuation principle that allows us to derive fluctuation-dissipation relations for many-time correlations and linear responses. We also speculate on how these features will be modified in systems evolving slowly out of equilibrium, as finite-dimensional or dilute spin-glasses. Secondly, we present a formalism that allows one to derive a series of approximated equations that determine the dynamics of disordered spin models on random (hyper) graphs. (author)
Modeling the neutron spin-flip process in a time-of-flight spin-resonance energy filter
Parizzi, A A; Klose, F
2002-01-01
A computer program for modeling the neutron spin-flip process in a novel time-of-flight (TOF) spin-resonance energy filter has been developed. The software allows studying the applicability of the device in various areas of spallation neutron scattering instrumentation, for example as a dynamic TOF monochromator. The program uses a quantum-mechanical approach to calculate the local spin-dependent spectra and is essential for optimizing the magnetic field profiles along the resonator axis. (orig.)
Spin foam models of matter coupled to gravity
International Nuclear Information System (INIS)
Mikovic, A
2002-01-01
We construct a class of spin foam models describing matter coupled to gravity, such that the gravitational sector is described by the unitary irreducible representations of the appropriate symmetry group, while the matter sector is described by the finite-dimensional irreducible representations of that group. The corresponding spin foam amplitudes in the four-dimensional gravity case are expressed in terms of the spin network amplitudes for pentagrams with additional external and internal matter edges. We also give a quantum field theory formulation of the model, where the matter degrees of freedom are described by spin network fields carrying the indices from the appropriate group representation. In the non-topological Lorentzian gravity case, we argue that the matter representations should be appropriate SO(3) or SO(2) representations contained in a given Lorentz matter representation, depending on whether one wants to describe a massive or a massless matter field. The corresponding spin network amplitudes are given as multiple integrals of propagators which are matrix spherical functions
Covariant introduction of quark spin into the dual resonance model
International Nuclear Information System (INIS)
Iroshnikov, G.S.
1979-01-01
A very simple method of insertion of a quark spin into the dual resonance model of hadron interaction is proposed. The method is suitable for amplitudes with an arbitrary number of particles. The amplitude of interaction of real particles is presented as a product of contribution of oscillatory excitations in the (q anti q) system and of a spin factor. The latter is equal to the trace of the product of the external particle wave functions constructed from structural quarks and satisfying the relativistic Bargman-Wigner equations. Two examples of calculating the meson interaction amplitudes are presented
Noisy Spins and the Richardson-Gaudin Model
Rowlands, Daniel A.; Lamacraft, Austen
2018-03-01
We study a system of spins (qubits) coupled to a common noisy environment, each precessing at its own frequency. The correlated noise experienced by the spins implies long-lived correlations that relax only due to the differing frequencies. We use a mapping to a non-Hermitian integrable Richardson-Gaudin model to find the exact spectrum of the quantum master equation in the high-temperature limit and, hence, determine the decay rate. Our solution can be used to evaluate the effect of inhomogeneous splittings on a system of qubits coupled to a common bath.
Tests of spinning turbine fragment impact on casing models
International Nuclear Information System (INIS)
Wilbeck, J.S.
1984-01-01
Ten 1/11-scale model turbine missile impact tests were conducted at a Naval spin chamber test facility to assess turbine missile effects in nuclear plant design. The objective of the tests was to determine the effects of missile spin, blade crush, and target edge conditions on the impact of turbine disk fragments on the steel casing. The results were intended for use in making realistic estimates for the initial conditions of fragments that might escape the casing in the event of a disk burst in a nuclear plant. The burst of a modified gas turbine rotor in a high-speed spin chamber provided three missiles with the proper rotational and translational velocities of actual steam turbine fragments. Tests of bladed, spinning missiles were compared with previous tests of unbladed, nonspinning missiles. The total residual energy of the spinning missiles, as observed from high-speed photographs of disk burst, was the same as that of the nonspinning missiles launched in a piercing orientation. Tests with bladed missiles showed that for equal burst speeds, the residual energy of bladed missiles is less than that of unbladed missiles. Impacts of missiles near the edge of targets resulted in residual missile velocities greater than for central impact. (orig.)
Correlation function of four spins in the percolation model
Directory of Open Access Journals (Sweden)
Vladimir S. Dotsenko
2016-10-01
It is known that the four-point functions define the actual fusion rules of a particular model. In this respect, we find that fusion of two spins, of dimension Δσ=596, produce a new channel, in the 4-point function, which is due to the operator with dimension Δ=5/8.
Impact of mass generation for spin-1 mediator simplified models
International Nuclear Information System (INIS)
Bell, Nicole F.; Cai, Yi; Leane, Rebecca K.
2017-01-01
In the simplified dark matter models commonly studied, the mass generation mechanism for the dark fields is not typically specified. We demonstrate that the dark matter interaction types, and hence the annihilation processes relevant for relic density and indirect detection, are strongly dictated by the mass generation mechanism chosen for the dark sector particles, and the requirement of gauge invariance. We focus on the class of models in which fermionic dark matter couples to a spin-1 vector or axial-vector mediator. However, in order to generate dark sector mass terms, it is necessary in most cases to introduce a dark Higgs field and thus a spin-0 scalar mediator will also be present. In the case that all the dark sector fields gain masses via coupling to a single dark sector Higgs field, it is mandatory that the axial-vector coupling of the spin-1 mediator to the dark matter is non-zero; the vector coupling may also be present depending on the charge assignments. For all other mass generation options, only pure vector couplings between the spin-1 mediator and the dark matter are allowed. If these coupling restrictions are not obeyed, unphysical results may be obtained such as a violation of unitarity at high energies. These two-mediator scenarios lead to important phenomenology that does not arise in single mediator models. We survey two-mediator dark matter models which contain both vector and scalar mediators, and explore their relic density and indirect detection phenomenology.
The spin S quantum Ising model at T=0
International Nuclear Information System (INIS)
Kamieniarz, G.; Kowalewski, L.; Piechocki, W.
1982-09-01
The Ising model with a transverse field for a general spin S is investigated within the framework of the Green-function method in the paramagnetic region at T=0. The analysis of selfconsistent equations gives a description of softmode phase transition as well as extrapolated values of critical fields and critical energy gap exponents. (author)
Irreversible Markov chains in spin models: Topological excitations
Lei, Ze; Krauth, Werner
2018-01-01
We analyze the convergence of the irreversible event-chain Monte Carlo algorithm for continuous spin models in the presence of topological excitations. In the two-dimensional XY model, we show that the local nature of the Markov-chain dynamics leads to slow decay of vortex-antivortex correlations while spin waves decorrelate very quickly. Using a Fréchet description of the maximum vortex-antivortex distance, we quantify the contributions of topological excitations to the equilibrium correlations, and show that they vary from a dynamical critical exponent z∼ 2 at the critical temperature to z∼ 0 in the limit of zero temperature. We confirm the event-chain algorithm's fast relaxation (corresponding to z = 0) of spin waves in the harmonic approximation to the XY model. Mixing times (describing the approach towards equilibrium from the least favorable initial state) however remain much larger than equilibrium correlation times at low temperatures. We also describe the respective influence of topological monopole-antimonopole excitations and of spin waves on the event-chain dynamics in the three-dimensional Heisenberg model.
Analysis of spin and gauge models with variational methods
International Nuclear Information System (INIS)
Dagotto, E.; Masperi, L.; Moreo, A.; Della Selva, A.; Fiore, R.
1985-01-01
Since independent-site (link) or independent-link (plaquette) variational states enhance the order or the disorder, respectively, in the treatment of spin (gauge) models, we prove that mixed states are able to improve the critical coupling while giving the qualitatively correct behavior of the relevant parameters
Dynamical phase transitions in spin models and automata
International Nuclear Information System (INIS)
Derrida, B.
1989-01-01
Some of the models and methods developed in the study of the dynamics of spin models and automata are described. Special attention is given to the distance method which consists of comparing the time evolution of two configurations. The method is used to obtain the phase boundary between a frozen and a chaotic phase in the case of deterministic models. For stochastic systems the method is used to obtain dynamical phase transitions
Modeling and optimizing of the random atomic spin gyroscope drift based on the atomic spin gyroscope
Energy Technology Data Exchange (ETDEWEB)
Quan, Wei; Lv, Lin, E-mail: lvlinlch1990@163.com; Liu, Baiqi [School of Instrument Science and Opto-Electronics Engineering, Beihang University, Beijing 100191 (China)
2014-11-15
In order to improve the atom spin gyroscope's operational accuracy and compensate the random error caused by the nonlinear and weak-stability characteristic of the random atomic spin gyroscope (ASG) drift, the hybrid random drift error model based on autoregressive (AR) and genetic programming (GP) + genetic algorithm (GA) technique is established. The time series of random ASG drift is taken as the study object. The time series of random ASG drift is acquired by analyzing and preprocessing the measured data of ASG. The linear section model is established based on AR technique. After that, the nonlinear section model is built based on GP technique and GA is used to optimize the coefficients of the mathematic expression acquired by GP in order to obtain a more accurate model. The simulation result indicates that this hybrid model can effectively reflect the characteristics of the ASG's random drift. The square error of the ASG's random drift is reduced by 92.40%. Comparing with the AR technique and the GP + GA technique, the random drift is reduced by 9.34% and 5.06%, respectively. The hybrid modeling method can effectively compensate the ASG's random drift and improve the stability of the system.
Analysis of Spin Financial Market by GARCH Model
International Nuclear Information System (INIS)
Takaishi, Tetsuya
2013-01-01
A spin model is used for simulations of financial markets. To determine return volatility in the spin financial market we use the GARCH model often used for volatility estimation in empirical finance. We apply the Bayesian inference performed by the Markov Chain Monte Carlo method to the parameter estimation of the GARCH model. It is found that volatility determined by the GARCH model exhibits ''volatility clustering'' also observed in the real financial markets. Using volatility determined by the GARCH model we examine the mixture-of-distribution hypothesis (MDH) suggested for the asset return dynamics. We find that the returns standardized by volatility are approximately standard normal random variables. Moreover we find that the absolute standardized returns show no significant autocorrelation. These findings are consistent with the view of the MDH for the return dynamics
GEM - The Global Earthquake Model
Smolka, A.
2009-04-01
Over 500,000 people died in the last decade due to earthquakes and tsunamis, mostly in the developing world, where the risk is increasing due to rapid population growth. In many seismic regions, no hazard and risk models exist, and even where models do exist, they are intelligible only by experts, or available only for commercial purposes. The Global Earthquake Model (GEM) answers the need for an openly accessible risk management tool. GEM is an internationally sanctioned public private partnership initiated by the Organisation for Economic Cooperation and Development (OECD) which will establish an authoritative standard for calculating and communicating earthquake hazard and risk, and will be designed to serve as the critical instrument to support decisions and actions that reduce earthquake losses worldwide. GEM will integrate developments on the forefront of scientific and engineering knowledge of earthquakes, at global, regional and local scale. The work is organized in three modules: hazard, risk, and socio-economic impact. The hazard module calculates probabilities of earthquake occurrence and resulting shaking at any given location. The risk module calculates fatalities, injuries, and damage based on expected shaking, building vulnerability, and the distribution of population and of exposed values and facilities. The socio-economic impact module delivers tools for making educated decisions to mitigate and manage risk. GEM will be a versatile online tool, with open source code and a map-based graphical interface. The underlying data will be open wherever possible, and its modular input and output will be adapted to multiple user groups: scientists and engineers, risk managers and decision makers in the public and private sectors, and the public-at- large. GEM will be the first global model for seismic risk assessment at a national and regional scale, and aims to achieve broad scientific participation and independence. Its development will occur in a
Dynamics of carrions in the spin-fermion model
International Nuclear Information System (INIS)
Kuzemskij, A.L.; Marvakov, D.
1996-01-01
The spectrum of hole quasiparticles (carrions) and the role of magnetic correlations has been considered in the framework of spin-fermion (Kondo-Heisenberg) model by means of the equation-of-motion method. The hole quasiparticle dynamics has been discussed for t-J model and compared with that of for spin-fermion model to determine how the one- and two-magnon processes define the true nature of carriers in HTSC. For this Kondo-Heisenberg-type model it was clearly pointed out on the self-energy level, beyond Hartree-Fock approximation, that two-magnon processes can play a role for the formation of the superconducting state. 60 refs
On spin and matrix models in the complex plane
International Nuclear Information System (INIS)
Damgaard, P.H.; Heller, U.M.
1993-01-01
We describe various aspects of statistical mechanics defined in the complex temperature or coupling-constant plane. Using exactly solvable models, we analyse such aspects as renormalization group flows in the complex plane, the distribution of partition function zeros, and the question of new coupling-constant symmetries of complex-plane spin models. The double-scaling form of matrix models is shown to be exactly equivalent to finite-size scaling of two-dimensional spin systems. This is used to show that the string susceptibility exponents derived from matrix models can be obtained numerically with very high accuracy from the scaling of finite-N partition function zeros in the complex plane. (orig.)
Twisted spin Sutherland models from quantum Hamiltonian reduction
International Nuclear Information System (INIS)
Feher, L; Pusztai, B G
2008-01-01
Recent general results on Hamiltonian reductions under polar group actions are applied to study some reductions of the free particle governed by the Laplace-Beltrami operator of a compact, connected, simple Lie group. The reduced systems associated with arbitrary finite-dimensional irreducible representations of the group by using the symmetry induced by twisted conjugations are described in detail. These systems generically yield integrable Sutherland-type many-body models with spin, which are called twisted spin Sutherland models if the underlying twisted conjugations are built on non-trivial Dynkin diagram automorphisms. The spectra of these models can be calculated, in principle, by solving certain Clebsch-Gordan problems, and the result is presented for the models associated with the symmetric tensorial powers of the defining representation of SU(N)
Quark potential model of baryon spin-orbit mass splittings
International Nuclear Information System (INIS)
Wang Fan; Wong Chunwa
1987-01-01
We show that it is possible to make the P-wave spin-orbit mass splittings in Λ baryons consistent with those of nonstrange baryons in a naive quark model, but only by introducing additional terms in the quark-quark effective interaction. These terms might be related to contributions due to pomeron exchange and sea excitations. The implications of our model in meson spectroscopy and nuclear forces are discussed. (orig.)
Stochastic higher spin six vertex model and Macdonald measures
Borodin, Alexei
2018-02-01
We prove an identity that relates the q-Laplace transform of the height function of a (higher spin inhomogeneous) stochastic six vertex model in a quadrant on one side and a multiplicative functional of a Macdonald measure on the other. The identity is used to prove the GUE Tracy-Widom asymptotics for two instances of the stochastic six vertex model via asymptotic analysis of the corresponding Schur measures.
Takaful Models and Global Practices
Akhter, Waheed
2010-01-01
There is a global interest in Islamic finance in general and Takāful in particular. The main feature that differentiates Takāful services from conventional ones is Sharī‟ah compliance nature of these services. Investors are taking keen interest in this potential market as Muslims constitute about one fourth of the world population (Muslim population, 2006). To streamline operations of a Takāful company, management and Sharī‟ah experts have developed different operational models for Takāful bu...
Green function study of a mixed spin-((3)/(2)) and spin-((1)/(2)) Heisenberg ferrimagnetic model
International Nuclear Information System (INIS)
Li Jun; Wei Guozhu; Du An
2004-01-01
The magnetic properties of a mixed spin-((3)/(2)) and spin-((1)/(2)) Heisenberg ferrimagnetic system on a square lattice are investigated theoretically by a multisublattice Green-function technique which takes into account the quantum nature of Heisenberg spins. This model can be relevant for understanding the magnetic behavior of the new class of organometallic materials that exhibit spontaneous magnetic moments at room temperature. We discuss the spontaneous magnetic moments and the finite-temperature phase diagram. We find that there is no compensation point at finite temperature when only the nearest-neighbor interaction and the single-ion anisotropy are included. When the next-nearest-neighbor interaction between spin-((1)/(2)) is taken into account and exceeds a minimum value, a compensation point appears and it is basically unchanged for other values in Hamiltonian fixed. The next-nearest-neighbor interaction between spin-((3)/(2)) has the effect of changing the compensation temperature
A self-consistent spin-diffusion model for micromagnetics
Abert, Claas; Ruggeri, Michele; Bruckner, Florian; Vogler, Christoph; Manchon, Aurelien; Praetorius, Dirk; Suess, Dieter
2016-01-01
We propose a three-dimensional micromagnetic model that dynamically solves the Landau-Lifshitz-Gilbert equation coupled to the full spin-diffusion equation. In contrast to previous methods, we solve for the magnetization dynamics and the electric potential in a self-consistent fashion. This treatment allows for an accurate description of magnetization dependent resistance changes. Moreover, the presented algorithm describes both spin accumulation due to smooth magnetization transitions and due to material interfaces as in multilayer structures. The model and its finite-element implementation are validated by current driven motion of a magnetic vortex structure. In a second experiment, the resistivity of a magnetic multilayer structure in dependence of the tilting angle of the magnetization in the different layers is investigated. Both examples show good agreement with reference simulations and experiments respectively.
The transverse spin-1 Ising model with random interactions
Energy Technology Data Exchange (ETDEWEB)
Bouziane, Touria [Department of Physics, Faculty of Sciences, University of Moulay Ismail, B.P. 11201 Meknes (Morocco)], E-mail: touria582004@yahoo.fr; Saber, Mohammed [Department of Physics, Faculty of Sciences, University of Moulay Ismail, B.P. 11201 Meknes (Morocco); Dpto. Fisica Aplicada I, EUPDS (EUPDS), Plaza Europa, 1, San Sebastian 20018 (Spain)
2009-01-15
The phase diagrams of the transverse spin-1 Ising model with random interactions are investigated using a new technique in the effective field theory that employs a probability distribution within the framework of the single-site cluster theory based on the use of exact Ising spin identities. A model is adopted in which the nearest-neighbor exchange couplings are independent random variables distributed according to the law P(J{sub ij})=p{delta}(J{sub ij}-J)+(1-p){delta}(J{sub ij}-{alpha}J). General formulae, applicable to lattices with coordination number N, are given. Numerical results are presented for a simple cubic lattice. The possible reentrant phenomenon displayed by the system due to the competitive effects between exchange interactions occurs for the appropriate range of the parameter {alpha}.
A self-consistent spin-diffusion model for micromagnetics
Abert, Claas
2016-12-17
We propose a three-dimensional micromagnetic model that dynamically solves the Landau-Lifshitz-Gilbert equation coupled to the full spin-diffusion equation. In contrast to previous methods, we solve for the magnetization dynamics and the electric potential in a self-consistent fashion. This treatment allows for an accurate description of magnetization dependent resistance changes. Moreover, the presented algorithm describes both spin accumulation due to smooth magnetization transitions and due to material interfaces as in multilayer structures. The model and its finite-element implementation are validated by current driven motion of a magnetic vortex structure. In a second experiment, the resistivity of a magnetic multilayer structure in dependence of the tilting angle of the magnetization in the different layers is investigated. Both examples show good agreement with reference simulations and experiments respectively.
Dynamics of the two-spin spin-boson model with a common bath
Energy Technology Data Exchange (ETDEWEB)
Deng, Tianrui [Division of Materials Science, Nanyang Technological University, Singapore 639798 (Singapore); Centre for Optical and Electromagnetic Research, Zhejiang Provincial Key Laboratory for Sensing Technologies, Zhejiang University, Hangzhou 310058 (China); Yan, Yiying; Chen, Lipeng; Zhao, Yang, E-mail: YZhao@ntu.edu.sg [Division of Materials Science, Nanyang Technological University, Singapore 639798 (Singapore)
2016-04-14
Dynamics of the two-spin spin-boson model in the presence of Ohmic and sub-Ohmic baths is investigated by employing a multitude of the Davydov D{sub 1} trial states, also known as the multi-D{sub 1} Ansatz. Its accuracy in dynamics simulations of the two-spin SBM is improved significantly over the single D{sub 1} Ansatz, especially in the weak to moderately strong coupling regime. Validity of the multi-D{sub 1} Ansatz for various coupling strengths is also systematically examined by making use of the deviation vector which quantifies how faithfully the trial state obeys the Schrödinger equation. The time evolution of population difference and entanglement has been studied for various initial conditions and coupling strengths. Careful comparisons are carried out between our approach and three other methods, i.e., the time-dependent numerical renormalization group (TD-NRG) approach, the Bloch-Redfield theory, and a method based on a variational master equation. For strong coupling, the multi-D{sub 1} trial state yields consistent results as the TD-NRG approach in the Ohmic regime while the two disagree in the sub-Ohmic regime, where the multi-D{sub 1} trial state is shown to be more accurate. For weak coupling, the multi-D{sub 1} trial state agrees with the two master-equation methods in the presence of both Ohmic and sub-Ohmic baths, but shows considerable differences with the TD-NRG approach in the presence of a sub-Ohmic bath, calling into question the validity of the TD-NRG results at long times in the literature.
Adiabatic analysis of collisions. III. Remarks on the spin model
International Nuclear Information System (INIS)
Fano, U.
1979-01-01
Analysis of a spin-rotation model illustrates how transitions between adiabatic channel states stem from the second, rather than from the first, rate of change of these states, provided that appropriate identification of channels and scaling of the independent variable are used. These remarks, like the earlier development of a post-adiabatic approach, aim at elucidating the surprising success of approximate separation of variables in the treatment of complex mechanical systems
A toy model for higher spin Dirac operators
International Nuclear Information System (INIS)
Eelbode, D.; Van de Voorde, L.
2010-01-01
This paper deals with the higher spin Dirac operator Q 2,1 acting on functions taking values in an irreducible representation space for so(m) with highest weight (5/2, 3/2, 1/2,..., 1/2). . This operator acts as a toy model for generalizations of the classical Rarita-Schwinger equations in Clifford analysis. Polynomial null solutions for this operator are studied in particular.
Long range anti-ferromagnetic spin model for prebiotic evolution
International Nuclear Information System (INIS)
Nokura, Kazuo
2003-01-01
I propose and discuss a fitness function for one-dimensional binary monomer sequences of macromolecules for prebiotic evolution. The fitness function is defined by the free energy of polymers in the high temperature random coil phase. With repulsive interactions among the same kind of monomers, the free energy in the high temperature limit becomes the energy function of the one-dimensional long range anti-ferromagnetic spin model, which is shown to have a dynamical phase transition and glassy states
A conformal invariant model of localized spinning test particles
International Nuclear Information System (INIS)
Duval, C.; Centre National de la Recherche Scientifique, 13 - Marseille; Fliche, H.H.; Centre National de la Recherche Scientifique, 13 - Marseille
1977-02-01
A purely classical model of massless test particle with spin s is introduced as the dynamical system defined by the 10 dimensional 0(4,2) co-adjoint orbit with Casimir numbers (s 2 ,0,0). The Mathisson Papapetrou et al. equations of motion in a gravitational field are recovered, and moreover the particle appears to travel on null geodesics. Several implications are discussed
Multi spin-flip dynamics: a solution of the one-dimensional Ising model
International Nuclear Information System (INIS)
Novak, I.
1990-01-01
The Glauber dynamics of interacting Ising spins (the single spin-flip dynamics) is generalized to p spin-flip dynamics with a simultaneous flip of up to p spins in a single configuration move. The p spin-flip dynamics is studied of the one-dimensional Ising model with uniform nearest-neighbour interaction. For this case, an exact relation is given for the time dependence of magnetization. It was found that the critical slowing down in this model could be avoided when p spin-flip dynamics with p>2 was considered. (author). 17 refs
Modeling of global biomass policies
International Nuclear Information System (INIS)
Gielen, Dolf; Fujino, Junichi; Hashimoto, Seiji; Moriguchi, Yuichi
2003-01-01
This paper discusses the BEAP model and its use for the analysis of biomass policies for CO 2 emission reduction. The model considers competing land use, trade and leakage effects, and competing emission reduction strategies. Two policy scenarios are presented. In case of a 2040 time horizon the results suggest that a combination of afforestation and limited use of biomass for energy and materials constitutes the most attractive set of strategies. In case of a 'continued Kyoto' scenario including afforestation permit trade, the results suggest 5.1 Gt emission reduction based on land use change in 2020, two thirds of the total emission reduction by then. In case of global emission reduction, land use, land use change and forestry (LULUCF) accounts for one quarter of the emission reduction. However these results depend on the modeling time horizon. In case of a broader time horizon, maximized biomass production is more attractive than LULUCF. This result can be interpreted as a warning against a market based trading scheme for LULUCF credits. The model results suggest that the bioenergy market is dominated by transportation fuels and heating, and to a lesser extent feedstocks. Bioelectricity does not gain a significant market share in case competing CO 2 -free electricity options such as CO 2 capture and sequestration and nuclear are considered. To some extent trade in agricultural food products such as beef and cereals will be affected by CO 2 policies
Modeling of global biomass policies
International Nuclear Information System (INIS)
Gielen, D.; Fujino, Junichi; Hashimoto, Seiji; Moriguchi, Yuichi
2003-01-01
This paper discusses the BEAP model and its use for the analysis of biomass policies for CO 2 emission reduction. The model considers competing land use, trade and leakage effects, and competing emission reduction strategies. Two policy scenarios are presented. In case of a 2040 time horizon the results suggest that a combination of afforestation and limited use of biomass for energy and materials constitutes the most attractive set of strategies. In case of a 'continued Kyoto' scenario including afforestation permit trade, the results suggest 5.1 Gt emission reduction based on land use change in 2020, two thirds of the total emission reduction by then. In case of global emission reduction, land use, land use change and forestry (LULUCF) accounts for one quarter of the emission reduction. However these results depend on the modeling time horizon. In case of a broader time horizon, maximized biomass production is more attractive than LULUCF. This result can be interpreted as a warning against a market based trading scheme for LULUCF credits. The model results suggest that the bioenergy market is dominated by transportation fuels and heating, and to a lesser extent feedstocks. Bioelectricity does not gain a significant market share in case competing CO 2 -free electricity options such as CO 2 capture and sequestration and nuclear are considered. To some extent trade in agricultural food products such as beef and cereals will be affected by CO 2 policies. (Author)
Kinetics of a mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model
International Nuclear Information System (INIS)
Deviren, Bayram; Keskin, Mustafa; Canko, Osman
2009-01-01
We present a study, within a mean-field approach, of the kinetics of a mixed ferrimagnetic model on a square lattice in which two interpenetrating square sublattices have spins that can take two values, σ=±1/2 , alternated with spins that can take the four values, S=±3/2 ,±1/2 . We use the Glauber-type stochastic dynamics to describe the time evolution of the system with a crystal-field interaction in the presence of a time-dependent oscillating external magnetic field. The nature (continuous and discontinuous) of transition is characterized by studying the thermal behaviors of average order parameters in a period. The dynamic phase transition points are obtained and the phase diagrams are presented in the reduced magnetic field amplitude (h) and reduced temperature (T) plane, and in the reduced temperature and interaction parameter planes, namely in the (h, T) and (d, T) planes, d is the reduced crystal-field interaction. The phase diagrams always exhibit a tricritical point in (h, T) plane, but do not exhibit in the (d, T) plane for low values of h. The dynamic multicritical point or dynamic critical end point exist in the (d, T) plane for low values of h. Moreover, phase diagrams contain paramagnetic (p), ferromagnetic (f), ferrimagnetic (i) phases, two coexistence or mixed phase regions, (f+p) and (i+p), that strongly depend on interaction parameters
Kinetics of a mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model
Energy Technology Data Exchange (ETDEWEB)
Deviren, Bayram [Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr; Canko, Osman [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)
2009-03-15
We present a study, within a mean-field approach, of the kinetics of a mixed ferrimagnetic model on a square lattice in which two interpenetrating square sublattices have spins that can take two values, {sigma}={+-}1/2 , alternated with spins that can take the four values, S={+-}3/2 ,{+-}1/2 . We use the Glauber-type stochastic dynamics to describe the time evolution of the system with a crystal-field interaction in the presence of a time-dependent oscillating external magnetic field. The nature (continuous and discontinuous) of transition is characterized by studying the thermal behaviors of average order parameters in a period. The dynamic phase transition points are obtained and the phase diagrams are presented in the reduced magnetic field amplitude (h) and reduced temperature (T) plane, and in the reduced temperature and interaction parameter planes, namely in the (h, T) and (d, T) planes, d is the reduced crystal-field interaction. The phase diagrams always exhibit a tricritical point in (h, T) plane, but do not exhibit in the (d, T) plane for low values of h. The dynamic multicritical point or dynamic critical end point exist in the (d, T) plane for low values of h. Moreover, phase diagrams contain paramagnetic (p), ferromagnetic (f), ferrimagnetic (i) phases, two coexistence or mixed phase regions, (f+p) and (i+p), that strongly depend on interaction parameters.
Deformations of N=4 SYM and integrable spin chain models
International Nuclear Information System (INIS)
Berenstein, David; Cherkis, Sergey A.
2004-01-01
Beginning with the planar limit of N=4 SYM theory, we study planar diagrams for field theory deformations of N=4 which are marginal at the free field theory level. We show that the requirement of integrability of the full one-loop dilatation operator in the scalar sector, places very strong constraints on the field theory, so that the only soluble models correspond essentially to orbifolds of N=4 SYM. For these, the associated spin chain model gets twisted boundary conditions that depend on the length of the chain, but which are still integrable. We also show that theories with integrable subsectors appear quite generically, and it is possible to engineer integrable subsectors to have some specific symmetry, however these do not generally lead to full integrability. We also try to construct a theory whose spin chain has quantum group symmetry SOq(6) as a deformation of the SO(6) R-symmetry structure of N=4 SYM. We show that it is not possible to obtain a spin chain with that symmetry from deformations of the scalar potential of N=4 SYM.We also show that the natural context for these questions can be better phrased in terms of multi-matrix quantum mechanics rather than in four-dimensional field theories
Edge states and conformal boundary conditions in super spin chains and super sigma models
International Nuclear Information System (INIS)
Bondesan, Roberto; Jacobsen, Jesper L.; Saleur, Hubert
2011-01-01
The sigma models on projective superspaces CP N+M-1|N with topological angle θ=πmod2π flow to non-unitary, logarithmic conformal field theories in the low-energy limit. In this paper, we determine the exact spectrum of these theories for all open boundary conditions preserving the full global symmetry of the model, generalizing recent work on the particular case M=0 [C. Candu et al., JHEP 1002 (2010) 015]. In the sigma model setting, these boundary conditions are associated with complex line bundles, and are labelled by an integer, related with the exact value of θ. Our approach relies on a spin chain regularization, where the boundary conditions now correspond to the introduction of additional edge states. The exact values of the exponents then follow from a lengthy algebraic analysis, a reformulation of the spin chain in terms of crossing and non-crossing loops (represented as a certain subalgebra of the Brauer algebra), and earlier results on the so-called one- and two-boundary Temperley-Lieb algebras (also known as blob algebras). A remarkable result is that the exponents, in general, turn out to be irrational. The case M=1 has direct applications to the spin quantum Hall effect, which will be discussed in a sequel.
Edge states and conformal boundary conditions in super spin chains and super sigma models
Energy Technology Data Exchange (ETDEWEB)
Bondesan, Roberto, E-mail: roberto.bondesan@cea.f [LPTENS, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris (France); Institute de Physique Theorique, CEA Saclay, F-91191 Gif-sur-Yvette (France); Jacobsen, Jesper L. [LPTENS, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris (France); Universite Pierre et Marie Curie, 4 place Jussieu, 75252 Paris (France); Saleur, Hubert [Institute de Physique Theorique, CEA Saclay, F-91191 Gif-sur-Yvette (France); Physics Department, USC, Los Angeles, CA 90089-0484 (United States)
2011-08-11
The sigma models on projective superspaces CP{sup N+M-1{vert_bar}N} with topological angle {theta}={pi}mod2{pi} flow to non-unitary, logarithmic conformal field theories in the low-energy limit. In this paper, we determine the exact spectrum of these theories for all open boundary conditions preserving the full global symmetry of the model, generalizing recent work on the particular case M=0 [C. Candu et al., JHEP 1002 (2010) 015]. In the sigma model setting, these boundary conditions are associated with complex line bundles, and are labelled by an integer, related with the exact value of {theta}. Our approach relies on a spin chain regularization, where the boundary conditions now correspond to the introduction of additional edge states. The exact values of the exponents then follow from a lengthy algebraic analysis, a reformulation of the spin chain in terms of crossing and non-crossing loops (represented as a certain subalgebra of the Brauer algebra), and earlier results on the so-called one- and two-boundary Temperley-Lieb algebras (also known as blob algebras). A remarkable result is that the exponents, in general, turn out to be irrational. The case M=1 has direct applications to the spin quantum Hall effect, which will be discussed in a sequel.
Modeling spin selectivity in charge transfer across the DNA/Gold interface
Energy Technology Data Exchange (ETDEWEB)
Behnia, S., E-mail: s.behnia@sci.uut.ac.ir [Department of Physics, Urmia University of Technology, Urmia (Iran, Islamic Republic of); Fathizadeh, S. [Department of Physics, Urmia University of Technology, Urmia (Iran, Islamic Republic of); Akhshani, A. [Department of Physics, Urmia Branch, Islamic Azad University, Urmia (Iran, Islamic Republic of)
2016-09-30
Highlights: • DNA in spintronics is applied. Nearly pure spin current is observed in the system. • A combined spin-polaronic PBH model is proposed for spin transfer in DNA molecule. • Spin Hall effect in DNA due to spin–orbit coupling is verified. • The temperature dependence of Hall conductivity is appeared. • Regions of parameters were determined that polarization of spin current is maximum. - Abstract: Experimental results show that the photoelectrons emitted from the gold substrate due to laser radiation, passe through DNA nanowires with spin-polarized nature. This study proposes the use of chiral DNA molecule in spintronics and information processing. To investigate the spin transfer in DNA molecules, we established a theoretical model based on a combined spin-polaronic Peyrard–Bishop–Holstein model. Accordingly, a nearly pure spin current is appeared. The simultaneous effects of the incident radiation and external magnetic field create characteristic islands corresponding to the pure spin currents, which can be predicted and detected using the multifractal dimensions spectrum. We can verify the spin Hall effect on DNA oligomers through spin–orbit coupling. As such, we can proceed to our significant purpose, which is to create a nearly pure spin current for information transfer and determine the regions of parameter values from which the maximal polarization in spin current emerges.
On mono-W signatures in spin-1 simplified models
Directory of Open Access Journals (Sweden)
Ulrich Haisch
2016-09-01
Full Text Available The potential sensitivity to isospin-breaking effects makes LHC searches for mono-W signatures promising probes of the coupling structure between the Standard Model and dark matter. It has been shown, however, that the strong sensitivity of the mono-W channel to the relative magnitude and sign of the up-type and down-type quark couplings to dark matter is an artifact of unitarity violation. We provide three different solutions to this mono-W problem in the context of spin-1 simplified models and briefly discuss the impact that our findings have on the prospects of mono-W searches at future LHC runs.
On mono-W signatures in spin-1 simplified models
International Nuclear Information System (INIS)
Haisch, Ulrich; Tait, Tim M.P.
2016-03-01
The potential sensitivity to isospin-breaking effects makes LHC searches for mono-W signatures promising probes of the coupling structure between the Standard Model and dark matter. It has been shown, however, that the strong sensitivity of the mono-W channel to the relative magnitude and sign of the up-type and down-type quark couplings to dark matter is an artefact of unitarity violation. We provide three different solutions to this mono-W problem in the context of spin-1 simplified models and briefly discuss the impact that our findings have on the prospects of mono-W searches at future LHC runs.
Completeness of classical spin models and universal quantum computation
International Nuclear Information System (INIS)
De las Cuevas, Gemma; Dür, Wolfgang; Briegel, Hans J; Van den Nest, Maarten
2009-01-01
We study mappings between different classical spin systems that leave the partition function invariant. As recently shown in Van den Nest et al (2008 Phys. Rev. Lett. 100 110501), the partition function of the 2D square lattice Ising model in the presence of an inhomogeneous magnetic field can specialize to the partition function of any Ising system on an arbitrary graph. In this sense the 2D Ising model is said to be 'complete'. However, in order to obtain the above result, the coupling strengths on the 2D lattice must assume complex values, and thus do not allow for a physical interpretation. Here we show how a complete model with real—and, hence, 'physical'—couplings can be obtained if the 3D Ising model is considered. We furthermore show how to map general q-state systems with possibly many-body interactions to the 2D Ising model with complex parameters, and give completeness results for these models with real parameters. We also demonstrate that the computational overhead in these constructions is in all relevant cases polynomial. These results are proved by invoking a recently found cross-connection between statistical mechanics and quantum information theory, where partition functions are expressed as quantum mechanical amplitudes. Within this framework, there exists a natural correspondence between many-body quantum states that allow for universal quantum computation via local measurements only, and complete classical spin systems
International Nuclear Information System (INIS)
Žukovič, Milan; Hristopulos, Dionissios T
2009-01-01
A current problem of practical significance is how to analyze large, spatially distributed, environmental data sets. The problem is more challenging for variables that follow non-Gaussian distributions. We show by means of numerical simulations that the spatial correlations between variables can be captured by interactions between 'spins'. The spins represent multilevel discretizations of environmental variables with respect to a number of pre-defined thresholds. The spatial dependence between the 'spins' is imposed by means of short-range interactions. We present two approaches, inspired by the Ising and Potts models, that generate conditional simulations of spatially distributed variables from samples with missing data. Currently, the sampling and simulation points are assumed to be at the nodes of a regular grid. The conditional simulations of the 'spin system' are forced to respect locally the sample values and the system statistics globally. The second constraint is enforced by minimizing a cost function representing the deviation between normalized correlation energies of the simulated and the sample distributions. In the approach based on the N c -state Potts model, each point is assigned to one of N c classes. The interactions involve all the points simultaneously. In the Ising model approach, a sequential simulation scheme is used: the discretization at each simulation level is binomial (i.e., ± 1). Information propagates from lower to higher levels as the simulation proceeds. We compare the two approaches in terms of their ability to reproduce the target statistics (e.g., the histogram and the variogram of the sample distribution), to predict data at unsampled locations, as well as in terms of their computational complexity. The comparison is based on a non-Gaussian data set (derived from a digital elevation model of the Walker Lake area, Nevada, USA). We discuss the impact of relevant simulation parameters, such as the domain size, the number of
Žukovič, Milan; Hristopulos, Dionissios T.
2009-02-01
A current problem of practical significance is how to analyze large, spatially distributed, environmental data sets. The problem is more challenging for variables that follow non-Gaussian distributions. We show by means of numerical simulations that the spatial correlations between variables can be captured by interactions between 'spins'. The spins represent multilevel discretizations of environmental variables with respect to a number of pre-defined thresholds. The spatial dependence between the 'spins' is imposed by means of short-range interactions. We present two approaches, inspired by the Ising and Potts models, that generate conditional simulations of spatially distributed variables from samples with missing data. Currently, the sampling and simulation points are assumed to be at the nodes of a regular grid. The conditional simulations of the 'spin system' are forced to respect locally the sample values and the system statistics globally. The second constraint is enforced by minimizing a cost function representing the deviation between normalized correlation energies of the simulated and the sample distributions. In the approach based on the Nc-state Potts model, each point is assigned to one of Nc classes. The interactions involve all the points simultaneously. In the Ising model approach, a sequential simulation scheme is used: the discretization at each simulation level is binomial (i.e., ± 1). Information propagates from lower to higher levels as the simulation proceeds. We compare the two approaches in terms of their ability to reproduce the target statistics (e.g., the histogram and the variogram of the sample distribution), to predict data at unsampled locations, as well as in terms of their computational complexity. The comparison is based on a non-Gaussian data set (derived from a digital elevation model of the Walker Lake area, Nevada, USA). We discuss the impact of relevant simulation parameters, such as the domain size, the number of
Magnetic properties of a quantum transverse spin-1 Blume-Emery-Griffiths model
International Nuclear Information System (INIS)
Ez Zahraouy, H.
1993-09-01
Using an expansion technique for cluster identities of spin-1 localized spin systems, we study the magnetic properties of a quantum transverse spin-1 Blume-Emery-Griffiths model. The longitudinal and transverse magnetizations and the quadrupolar moments are calculated. General formula applicable to structures with arbitrary coordination number are given. (author). 38 refs, 6 figs
Čenčariková, Hana; Strečka, Jozef; Gendiar, Andrej; Tomašovičová, Natália
2018-05-01
An exhaustive ground-state analysis of extended two-dimensional (2D) correlated spin-electron model consisting of the Ising spins localized on nodal lattice sites and mobile electrons delocalized over pairs of decorating sites is performed within the framework of rigorous analytical calculations. The investigated model, defined on an arbitrary 2D doubly decorated lattice, takes into account the kinetic energy of mobile electrons, the nearest-neighbor Ising coupling between the localized spins and mobile electrons, the further-neighbor Ising coupling between the localized spins and the Zeeman energy. The ground-state phase diagrams are examined for a wide range of model parameters for both ferromagnetic as well as antiferromagnetic interaction between the nodal Ising spins and non-zero value of external magnetic field. It is found that non-zero values of further-neighbor interaction leads to a formation of new quantum states as a consequence of competition between all considered interaction terms. Moreover, the new quantum states are accompanied with different magnetic features and thus, several kinds of field-driven phase transitions are observed.
Particle propagator of the spin Calogero–Sutherland model
International Nuclear Information System (INIS)
Nakai, Ryota; Kato, Yusuke
2014-01-01
Explicit-exact expressions for the particle propagator of the spin 1/2 Calogero–Sutherland model are derived for the system of a finite number of particles and for that in the thermodynamic limit. Derivation of the expression in the thermodynamic limit is also presented in detail. Combining this result with the hole propagator obtained in earlier studies, we calculate the spectral function of the single particle Green's function in the full range of the energy and momentum space. The resultant spectral function exhibits power-law singularity characteristic to correlated particle systems in one dimension. (paper)
An Analysis and Modelling of Spinning Process without Wall-Thickness Reduction
Directory of Open Access Journals (Sweden)
Jurković, M.
2006-01-01
Full Text Available Through the spinning process it is made the different axial-symmetrical parts by acting spinning roller on blank of sheet metal, which is shaped through a chuck. In the paper is shown an analyse of stressed and strained state, as well as forming force components of spinning process. On the ground of experimental results it is made mathematical modelling of spinning forming force. The obtained mathematical model describes enough accurate and reliable (P = 0,98 the spinning forming force.
Global constraints on Z2 fluxes in two different anisotropic limits of a hypernonagon Kitaev model
Kato, Yasuyuki; Kamiya, Yoshitomo; Nasu, Joji; Motome, Yukitoshi
2018-05-01
The Kitaev model is an exactly-soluble quantum spin model, whose ground state provides a canonical example of a quantum spin liquid. Spin excitations from the ground state are fractionalized into emergent matter fermions and Z2 fluxes. The Z2 flux excitation is pointlike in two dimensions, while it comprises a closed loop in three dimensions because of the local constraint for each closed volume. In addition, the fluxes obey global constraints involving (semi)macroscopic number of fluxes. We here investigate such global constraints in the Kitaev model on a three-dimensional lattice composed of nine-site elementary loops, dubbed the hypernonagon lattice, whose ground state is a chiral spin liquid. We consider two different anisotropic limits of the hypernonagon Kitaev model where the low-energy effective models are described solely by the Z2 fluxes. We show that there are two kinds of global constraints in the model defined on a three-dimensional torus, namely, surface and volume constraints: the surface constraint is imposed on the even-odd parity of the total number of fluxes threading a two-dimensional slice of the system, while the volume constraint is for the even-odd parity of the number of the fluxes through specific plaquettes whose total number is proportional to the system volume. In the two anisotropic limits, therefore, the elementary excitation of Z2 fluxes occurs in a pair of closed loops so as to satisfy both two global constraints as well as the local constraints.
Modelling MIZ dynamics in a global model
Rynders, Stefanie; Aksenov, Yevgeny; Feltham, Daniel; Nurser, George; Naveira Garabato, Alberto
2016-04-01
Exposure of large, previously ice-covered areas of the Arctic Ocean to the wind and surface ocean waves results in the Arctic pack ice cover becoming more fragmented and mobile, with large regions of ice cover evolving into the Marginal Ice Zone (MIZ). The need for better climate predictions, along with growing economic activity in the Polar Oceans, necessitates climate and forecasting models that can simulate fragmented sea ice with a greater fidelity. Current models are not fully fit for the purpose, since they neither model surface ocean waves in the MIZ, nor account for the effect of floe fragmentation on drag, nor include sea ice rheology that represents both the now thinner pack ice and MIZ ice dynamics. All these processes affect the momentum transfer to the ocean. We present initial results from a global ocean model NEMO (Nucleus for European Modelling of the Ocean) coupled to the Los Alamos sea ice model CICE. The model setup implements a novel rheological formulation for sea ice dynamics, accounting for ice floe collisions, thus offering a seamless framework for pack ice and MIZ simulations. The effect of surface waves on ice motion is included through wave pressure and the turbulent kinetic energy of ice floes. In the multidecadal model integrations we examine MIZ and basin scale sea ice and oceanic responses to the changes in ice dynamics. We analyse model sensitivities and attribute them to key sea ice and ocean dynamical mechanisms. The results suggest that the effect of the new ice rheology is confined to the MIZ. However with the current increase in summer MIZ area, which is projected to continue and may become the dominant type of sea ice in the Arctic, we argue that the effects of the combined sea ice rheology will be noticeable in large areas of the Arctic Ocean, affecting sea ice and ocean. With this study we assert that to make more accurate sea ice predictions in the changing Arctic, models need to include MIZ dynamics and physics.
On global and regional spectral evaluation of global geopotential models
International Nuclear Information System (INIS)
Ustun, A; Abbak, R A
2010-01-01
Spectral evaluation of global geopotential models (GGMs) is necessary to recognize the behaviour of gravity signal and its error recorded in spherical harmonic coefficients and associated standard deviations. Results put forward in this wise explain the whole contribution of gravity data in different kinds that represent various sections of the gravity spectrum. This method is more informative than accuracy assessment methods, which use external data such as GPS-levelling. Comparative spectral evaluation for more than one model can be performed both in global and local sense using many spectral tools. The number of GGMs has grown with the increasing number of data collected by the dedicated satellite gravity missions, CHAMP, GRACE and GOCE. This fact makes it necessary to measure the differences between models and to monitor the improvements in the gravity field recovery. In this paper, some of the satellite-only and combined models are examined in different scales, globally and regionally, in order to observe the advances in the modelling of GGMs and their strengths at various expansion degrees for geodetic and geophysical applications. The validation of the published errors of model coefficients is a part of this evaluation. All spectral tools explicitly reveal the superiority of the GRACE-based models when compared against the models that comprise the conventional satellite tracking data. The disagreement between models is large in local/regional areas if data sets are different, as seen from the example of the Turkish territory
Semi-local invariance in Ising models with multi-spin interaction
International Nuclear Information System (INIS)
Lipowski, A.
1996-08-01
We examine implications of semi-local invariance in Ising models with multispin interaction. In ergodic models all spin-spin correlation functions vanish and the local symmetry is the same as in locally gauge-invariant models. The d = 3 model with four-spin interaction is nonergodic at low temperature but the magnetic symmetry remains unbroken. The d = 3 model with eight-spin interaction is ergodic but undergoes the phase transition and most likely its low-temperature phase is characterized by a nonlocal order parameter. (author). 7 refs, 1 fig
2013-01-01
This book covers all principal aspects of currently investigated frustrated systems, from exactly solved frustrated models to real experimental frustrated systems, going through renormalization group treatment, Monte Carlo investigation of frustrated classical Ising and vector spin models, low-dimensional systems, spin ice and quantum spin glass. The reader can - within a single book - obtain a global view of the current research development in the field of frustrated systems.This new edition is updated with recent theoretical, numerical and experimental developments in the field of frustrated
Some models of spin coherence and decoherence in storage rings
International Nuclear Information System (INIS)
Heinemann, K.
1997-09-01
I present some simple exactly solvable models of spin diffusion caused by synchrotron radiation noise in storage rings. I am able to use standard stochastic differential equation and Fokker-Planck methods and I thereby introduce, and exploit, the polarization density. This quantity obeys a linear evolution equation of the Bloch type, which is, like the Fokker-Planck equation, universal in the sense that it is independent of the state of the system. I also briefly consider Bloch equations for other local polarization quantities derived from the polarization density. One of the models chosen is of relevance for some existing and proposed low energy electron (positron) storage rings which need polarization. I present numerical results for a ring with parameters typical of HERA and show that, where applicable, the results of my approach are in satisfactory agreement with calculations using SLIM. These calculations provide a numerical check of a basic tenet of the conventional method of calculating depolarization using the n-vector-axis. I also investigate the equilibrium behaviour of the spin ensemble when there is no synchrotron radiation. Finally, I summarize other results which I have obtained using the polarization density and which will be published separately. (orig.)
Topological order in an exactly solvable 3D spin model
International Nuclear Information System (INIS)
Bravyi, Sergey; Leemhuis, Bernhard; Terhal, Barbara M.
2011-01-01
Research highlights: RHtriangle We study exactly solvable spin model with six-qubit nearest neighbor interactions on a 3D face centered cubic lattice. RHtriangle The ground space of the model exhibits topological quantum order. RHtriangle Elementary excitations can be geometrically described as the corners of rectangular-shaped membranes. RHtriangle The ground space can encode 4g qubits where g is the greatest common divisor of the lattice dimensions. RHtriangle Logical operators acting on the encoded qubits are described in terms of closed strings and closed membranes. - Abstract: We study a 3D generalization of the toric code model introduced recently by Chamon. This is an exactly solvable spin model with six-qubit nearest-neighbor interactions on an FCC lattice whose ground space exhibits topological quantum order. The elementary excitations of this model which we call monopoles can be geometrically described as the corners of rectangular-shaped membranes. We prove that the creation of an isolated monopole separated from other monopoles by a distance R requires an operator acting on Ω(R 2 ) qubits. Composite particles that consist of two monopoles (dipoles) and four monopoles (quadrupoles) can be described as end-points of strings. The peculiar feature of the model is that dipole-type strings are rigid, that is, such strings must be aligned with face-diagonals of the lattice. For periodic boundary conditions the ground space can encode 4g qubits where g is the greatest common divisor of the lattice dimensions. We describe a complete set of logical operators acting on the encoded qubits in terms of closed strings and closed membranes.
Yield surface investigation of alloys during model disk spin tests
Directory of Open Access Journals (Sweden)
E. P. Kuzmin
2014-01-01
Full Text Available Gas-turbine engines operate under heavy subsequently static loading conditions. Disks of gas-turbine engine are high loaded parts of irregular shape having intensive stress concentrators wherein a 3D stress strain state occurs. The loss of load-carrying capability or burst of disk can lead to severe accident or disaster. Therefore, development of methods to assess deformations and to predict burst is one of the most important problems.Strength assessment approaches are used at all levels of engine creation. In recent years due to actively developing numerical method, particularly FEA, it became possible to investigate load-carrying capability of irregular shape disks, to use 3D computing schemes including flow theory and different options of force and deformation failure criteria. In spite of a wide progress and practical use of strength assessment approaches, there is a lack of detailed research data on yield surface of disk alloys. The main purpose of this work is to validate the use of basis hypothesis of flow theory and investigate the yield surface of disk alloys during the disks spin test.The results of quasi-static numerical simulation of spin tests of model disk made from high-temperature forged alloy are presented. To determine stress-strain state of disk during loading finite element analysis is used. Simulation of elastic-plastic strain fields was carried out using incremental theory of plasticity with isotropic hardening. Hardening function was taken from the results of specimens tensile test. Specimens were cut from a sinkhead of model disk. The paper investigates the model sensitivity affected by V.Mises and Tresca yield criteria as well as the Hosford model. To identify the material model parameters the eddy current sensors were used in the experimental approach to measure rim radial displacements during the load-unload of spin test. The results of calculation made using different material models were compared with the
Higher-spin currents in the Gross-Neveu model at 1/n"2
International Nuclear Information System (INIS)
Manashov, A.N.
2016-10-01
We calculate the anomalous dimensions of higher-spin currents, both singlet and non-singlet, in the Gross - Neveu model at the 1/n"2 order. It was conjectured that in the critical regime this model is dual to a higher-spin gauge theory on AdS_4. The AdS/CFT correspondence predicts that the masses of higher-spin fields correspond to the scaling dimensions of the singlet currents in the Gross - Neveu model.
Global potential energy surface of ground state singlet spin O4
Mankodi, Tapan K.; Bhandarkar, Upendra V.; Puranik, Bhalchandra P.
2018-02-01
A new global potential energy for the singlet spin state O4 system is reported using CASPT2/aug-cc-pVTZ ab initio calculations. The geometries for the six-dimensional surface are constructed using a novel point generation scheme that employs randomly generated configurations based on the beta distribution. The advantage of this scheme is apparent in the reduction of the number of required geometries for a reasonably accurate potential energy surface (PES) and the consequent decrease in the overall computational effort. The reported surface matches well with the recently published singlet surface by Paukku et al. [J. Chem. Phys. 147, 034301 (2017)]. In addition to the O4 PES, the ground state N4 PES is also constructed using the point generation scheme and compared with the existing PES [Y. Paukku et al., J. Chem. Phys. 139, 044309 (2013)]. The singlet surface is constructed with the aim of studying high energy O2-O2 collisions and predicting collision induced dissociation cross section to be used in simulating non-equilibrium aerothermodynamic flows.
Spherical Process Models for Global Spatial Statistics
Jeong, Jaehong; Jun, Mikyoung; Genton, Marc G.
2017-01-01
Statistical models used in geophysical, environmental, and climate science applications must reflect the curvature of the spatial domain in global data. Over the past few decades, statisticians have developed covariance models that capture
On modeling of statistical properties of classical 3D spin glasses
International Nuclear Information System (INIS)
Gevorkyan, A.S.; Abajyan, H.G.; Ayryan, E.A.
2011-01-01
We study statistical properties of 3D classical spin glass layer of certain width and infinite length. The 3D spin glass is represented as an ensemble of disordered 1D spatial spin chains (SSC) where interactions are random between spin chains (nonideal ensemble of 1D SSCs). It is proved that in the limit of Birkhoff's ergodic hypothesis performance, 3D spin glasses can be generated by Hamiltonian of disordered 1D SSC with random environment. Disordered 1D SSC is defined on a regular lattice where one randomly oriented spin is put on each node of lattice. Also, it is supposed that each spin randomly interacts with six nearest-neighboring spins (two spins on lattice and four in the environment). The recurrent transcendental equations are obtained on the nodes of spin-chain lattice. These equations, combined with the Silvester conditions, allow step-by-step construction of spin chain in the ground state of energy where all spins are in the minimal energy of a classical Hamiltonian. On the basis of these equations an original high-performance parallel algorithm is developed for 3D spin glasses simulation. Distributions of different parameters of unperturbed spin glass are calculated. In particular, it is analytically proved and numerical calculations show that the distribution of spin-spin interaction constant in Heisenberg nearest-neighboring Hamiltonian model, as opposed to widely used Gauss-Edwards-Anderson distribution, satisfies the Levy alpha-stable distribution law which does not have variance. A new formula is proposed for construction of partition function in the form of a one-dimensional integral on the energy distribution of 1D SSCs
The nucleon-nucleon spin-orbit interaction in the Skyrme model
International Nuclear Information System (INIS)
Riska, D.O.; Dannbom, K.
1987-01-01
The spin-orbit and quadratic spin-orbit components of the nucleon-nucleon interaction are derived in the Skyrme model at the classical level. These interaction components arise from the orbital and rotational motion of the soliton fields that form the nucleons. The isospin dependent part of the spin-orbit interaction is similar to the corresponding component obtained from boson exchange mechanisms at long distances although at short distances it is weaker. The isospin independent spin-orbit component is however different from the prediction of boson exchange mechanisms and has the opposite sign. The quadratic spin-orbit interaction is weak and has only an isospin dependent component
Controlling measurement-induced nonlocality in the Heisenberg XX model by three-spin interactions
Xie, Yu-Xia; Sun, Yu-Hang; Li, Zhao
2018-01-01
We investigate the well-defined measures of measurement-induced nonlocality (MIN) for thermal states of the transverse field XX model, with the addition of three-spin interaction terms being introduced. The results showed that the MINs are very sensitive to system parameters of the chain. The three-spin interactions can serve as flexible parameters for enhancing MINs of the boundary spins, and the maximum enhancement achievable by varying strengths of the three-spin interactions are different for the chain with different number of spins.
Critical exponents for the Reggeon quantum spin model
International Nuclear Information System (INIS)
Brower, R.C.; Furman, M.A.
1978-01-01
The Reggeon quantum spin (RQS) model on the transverse lattice in D dimensional impact parameter space has been conjectured to have the same critical behaviour as the Reggeon field theory (RFT). Thus from a high 'temperature' series of ten (D=2) and twenty (D=1) terms for the RQS model the authors extrapolate to the critical temperature T=Tsub(c) by Pade approximants to obtain the exponents eta=0.238 +- 0.008, z=1.16 +- 0.01, γ=1.271 +- 0.007 for D=2 and eta=0.317 +- 0.002, z=1.272 +- 0.007, γ=1.736 +- 0.001, lambda=0.57 +- 0.03 for D=1. These exponents naturally interpolate between the D=0 and D=4-epsilon results for RFT as expected on the basis of the universality conjecture. (Auth.)
Metric versus observable operator representation, higher spin models
Fring, Andreas; Frith, Thomas
2018-02-01
We elaborate further on the metric representation that is obtained by transferring the time-dependence from a Hermitian Hamiltonian to the metric operator in a related non-Hermitian system. We provide further insight into the procedure on how to employ the time-dependent Dyson relation and the quasi-Hermiticity relation to solve time-dependent Hermitian Hamiltonian systems. By solving both equations separately we argue here that it is in general easier to solve the former. We solve the mutually related time-dependent Schrödinger equation for a Hermitian and non-Hermitian spin 1/2, 1 and 3/2 model with time-independent and time-dependent metric, respectively. In all models the overdetermined coupled system of equations for the Dyson map can be decoupled algebraic manipulations and reduces to simple linear differential equations and an equation that can be converted into the non-linear Ermakov-Pinney equation.
Connections of the Liouville model and XXZ spin chain
Faddeev, Ludvig D.; Tirkkonen, Olav
1995-02-01
The quantum theory of the Liouville model with imaginary field is considered using the Quantum Inverse Scattering Method. An integrable structure with non-trivial spectral-parameter dependence is developed for lattice Liouville theory by scaling the L-matrix of lattice sine-Gordon theory. This L-matrix yields Bethe ansatz equations for Liouville theory, by the methods of the algebraic Bethe ansatz. Using the string picture of excited Bethe states, the lattice Liouville Bethe equations are mapped to the corresponding spin- {1}/{2} XXZ chain equations. The well developed theory of finite-size corrections in spin chains is used to deduce the conformal properties of the lattice Liouville Bethe states. The unitary series of conformal field theories emerge for Liouville couplings of the form γ = πν/( ν + 1), corresponding to root of unity XXZ anisotropies. The Bethe states give the full spectrum of the corresponding unitary conformal field theory, with the primary states in the Kač table parameterized by a string length K, and the remnant of the chain length mod ( ν + 1).
Connections of the Liouville model and XXZ spin chain
International Nuclear Information System (INIS)
Faddeev, L.D.; Tirkkonen, O.
1995-01-01
The quantum theory of the Liouville model with imaginary field is considered using the Quantum Inverse Scattering Method. An integrable structure with non-trivial spectral-parameter dependence is developed for lattice Liouville theory by scaling the L-matrix of lattice sine-Gordon theory. This L-matrix yields Bethe ansatz equations for Liouville theory, by the methods of the algebraic Bethe ansatz. Using the string picture of excited Bethe states, the lattice Liouville Bethe equations are mapped to the corresponding spin-1/2 XXZ chain equations. The well developed theory of finite-size corrections in spin chains is used to deduce the conformal properties of the lattice Liouville Bethe states. The unitary series of conformal field theories emerge for Liouville couplings of the form γ= πν/(ν+1), corresponding to root of unity XXZ anisotropies. The Bethe states give the full spectrum of the corresponding unitary conformal field theory, with the primary states in the Kac table parameterized by a string length K, and the remnant of the chain length mod (ν+1). (orig.)
Global model structures for ∗-modules
DEFF Research Database (Denmark)
Böhme, Benjamin
2018-01-01
We extend Schwede's work on the unstable global homotopy theory of orthogonal spaces and L-spaces to the category of ∗-modules (i.e., unstable S-modules). We prove a theorem which transports model structures and their properties from L-spaces to ∗-modules and show that the resulting global model...... structure for ∗-modules is monoidally Quillen equivalent to that of orthogonal spaces. As a consequence, there are induced Quillen equivalences between the associated model categories of monoids, which identify equivalent models for the global homotopy theory of A∞-spaces....
Model expressions for the spin-orbit interaction and phonon-mediated spin dynamics in quantum dots
Vaughan, M. P.; Rorison, J. M.
2018-01-01
Model expressions for the spin-orbit interaction in a quantum dot are obtained. The resulting form does not neglect cubic terms and allows for a generalized structural inversion asymmetry. We also obtain analytical expressions for the coupling between states for the electron-phonon interaction and use these to derive spin-relaxation rates, which are found to be qualitatively similar to those derived elsewhere in the literature. We find that, due to the inclusion of cubic terms, the Dresselhaus contribution to the ground state spin relaxation disappears for spherical dots. A comparison with previous theory and existing experimental results shows good agreement thereby presenting a clear analytical formalism for future developments. Comparative calculations for potential materials are presented.
De La Rosa Gomez, Alejandro; MacKay, Niall; Regelskis, Vidas
2017-04-01
We present a general method of folding an integrable spin chain, defined on a line, to obtain an integrable open spin chain, defined on a half-line. We illustrate our method through two fundamental models with sl2 Lie algebra symmetry: the Heisenberg XXX and the Inozemtsev hyperbolic spin chains. We obtain new long-range boundary Hamiltonians and demonstrate that they exhibit Yangian symmetries, thus ensuring integrability of the models we obtain. The method presented provides a ;bottom-up; approach for constructing integrable boundaries and can be applied to any spin chain model.
Solvable model of spin-dependent transport through a finite array of quantum dots
International Nuclear Information System (INIS)
Avdonin, S A; Dmitrieva, L A; Kuperin, Yu A; Sartan, V V
2005-01-01
The problem of spin-dependent transport of electrons through a finite array of quantum dots attached to a 1D quantum wire (spin gun) for various semiconductor materials is studied. The Breit-Fermi term for spin-spin interaction in the effective Hamiltonian of the device is shown to result in a dependence of transmission coefficient on the spin orientation. The difference of transmission probabilities for singlet and triplet channels can reach a few per cent for a single quantum dot. For several quantum dots in the array due to interference effects it can reach approximately 100% for some energy intervals. For the same energy intervals the conductance of the device reaches the value ∼1 in [e 2 /πℎ] units. As a result a model of the spin gun which transforms the spin-unpolarized electron beam into a completely polarized one is suggested
Nontrivial ac spin response in the effective Luttinger model
International Nuclear Information System (INIS)
Hu Liangbin; Zhong Jiansong; Hu Kaige
2006-01-01
Based on the three-dimensional effective Luttinger Hamiltonian and the exact Heisenberg equations of motion and within a self-consistent semiclassical approximation, we present a theoretical investigation on the nontrivial ac spin responses due to the intrinsic spin-orbit coupling of holes in p-doped bulk semiconductors. We show that the nontrivial ac spin responses induced by the combined action of an ac external electric field and the intrinsic spin-orbit coupling of holes may lead to the generation of a nonvanishing ac spin Hall current in a p-doped bulk semiconductor, which shares some similarities with the dissipationless dc spin Hall current conceived previously and also exhibits some interesting new features that was not found before
Critical behaviour of magnetic thin film with Heisenberg spin-S model
International Nuclear Information System (INIS)
Masrour, R.; Hamedoun, M.; Bouslykhane, K.; Hourmatallah, A.; Benzakour, N.; Benyoussef, A.
2009-01-01
The magnetic properties of a ferromagnetic thin film of face centered cubic (FCC) lattice with Heisenberg spin-S are examined using the high-temperature series expansions technique extrapolated with Pade approximations method. The critical reduced temperature of the system τ c is studied as function of thickness of the film and the exchange interactions in the bulk, and within the surfaces J b , J s and J perpendicular respectively. A critical value of surface exchange interaction above which surface magnetism appears is obtained. The dependence of the reduced critical temperature on the film thickness L has been investigated.
Modeling of diffusion of injected electron spins in spin-orbit coupled microchannels
Czech Academy of Sciences Publication Activity Database
Zarbo, Liviu; Sinova, Jairo; Knezevic, I.; Wunderlich, Joerg; Jungwirth, Tomáš
2010-01-01
Roč. 82, č. 20 (2010), 205320/1-205320/7 ISSN 1098-0121 R&D Projects: GA MŠk LC510; GA AV ČR KAN400100652 EU Projects: European Commission(XE) 215368 - SemiSpinNet Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : spintronics * spin dynamics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.772, year: 2010
Global Health Innovation Technology Models
Directory of Open Access Journals (Sweden)
Kimberly Harding
2016-04-01
Full Text Available Chronic technology and business process disparities between High Income, Low Middle Income and Low Income (HIC, LMIC, LIC research collaborators directly prevent the growth of sustainable Global Health innova‐ tion for infectious and rare diseases. There is a need for an Open Source-Open Science Architecture Framework to bridge this divide. We are proposing such a framework for consideration by the Global Health community, by utiliz‐ ing a hybrid approach of integrating agnostic Open Source technology and healthcare interoperability standards and Total Quality Management principles. We will validate this architecture framework through our programme called Project Orchid. Project Orchid is a conceptual Clinical Intelligence Exchange and Virtual Innovation platform utilizing this approach to support clinical innovation efforts for multi-national collaboration that can be locally sustainable for LIC and LMIC research cohorts. The goal is to enable LIC and LMIC research organizations to acceler‐ ate their clinical trial process maturity in the field of drug discovery, population health innovation initiatives and public domain knowledge networks. When sponsored, this concept will be tested by 12 confirmed clinical research and public health organizations in six countries. The potential impact of this platform is reduced drug discovery and public health innovation lag time and improved clinical trial interventions, due to reliable clinical intelligence and bio-surveillance across all phases of the clinical innovation process.
Multi-scale modeling of spin transport in organic semiconductors
Hemmatiyan, Shayan; Souza, Amaury; Kordt, Pascal; McNellis, Erik; Andrienko, Denis; Sinova, Jairo
In this work, we present our theoretical framework to simulate simultaneously spin and charge transport in amorphous organic semiconductors. By combining several techniques e.g. molecular dynamics, density functional theory and kinetic Monte Carlo, we are be able to study spin transport in the presence of anisotropy, thermal effects, magnetic and electric field effects in a realistic morphologies of amorphous organic systems. We apply our multi-scale approach to investigate the spin transport in amorphous Alq3 (Tris(8-hydroxyquinolinato)aluminum) and address the underlying spin relaxation mechanism in this system as a function of temperature, bias voltage, magnetic field and sample thickness.
Superstring sigma models from spin chains: the SU(1,1 vertical bar 1) case
International Nuclear Information System (INIS)
Bellucci, S.; Casteill, P.-Y.; Morales, J.F.
2005-01-01
We derive the coherent state representation of the integrable spin chain Hamiltonian with non-compact supersymmetry group G=SU(1,1 vertical bar 1). By passing to the continuous limit, we find a spin chain sigma model describing a string moving on the supercoset G/H, H being the stabilizer group. The action is written in a manifestly G-invariant form in terms of the Cartan forms and the string coordinates in the supercoset. The spin chain sigma model is shown to agree with that following from the Green-Schwarz action describing two-charged string spinning on AdS 5 xS 5
HYbrid Coordinate Ocean Model (HYCOM): Global
National Oceanic and Atmospheric Administration, Department of Commerce — Global HYbrid Coordinate Ocean Model (HYCOM) and U.S. Navy Coupled Ocean Data Assimilation (NCODA) 3-day, daily forecast at approximately 9-km (1/12-degree)...
ASTER Global Digital Elevation Model V002
National Aeronautics and Space Administration — The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) was developed jointly by the U.S. National...
Connor, Gregory
1996-01-01
Factor models are now widely used to support asset selection decisions. Global asset allocation, the allocation between stocks versus bonds and among nations, usually relies instead on correlation analysis of international equity and bond indexes. It would be preferable to have a single integrated framework for both asset selection and asset allocation. This framework would require a factor model applicable at an asset or country level, as well as at a global level,...
Higher-spin cluster algorithms: the Heisenberg spin and U(1) quantum link models
Energy Technology Data Exchange (ETDEWEB)
Chudnovsky, V
2000-03-01
I discuss here how the highly-efficient spin-1/2 cluster algorithm for the Heisenberg antiferromagnet may be extended to higher-dimensional representations; some numerical results are provided. The same extensions can be used for the U(1) flux cluster algorithm, but have not yielded signals of the desired Coulomb phase of the system.
Higher-spin cluster algorithms: the Heisenberg spin and U(1) quantum link models
International Nuclear Information System (INIS)
Chudnovsky, V.
2000-01-01
I discuss here how the highly-efficient spin-1/2 cluster algorithm for the Heisenberg antiferromagnet may be extended to higher-dimensional representations; some numerical results are provided. The same extensions can be used for the U(1) flux cluster algorithm, but have not yielded signals of the desired Coulomb phase of the system
Farberovich, Oleg V.; Mazalova, Victoria L.; Soldatov, Alexander V.
2015-11-01
We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density-functional scheme for the calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange coupling parameters linking the nickel ions with a silicon substrate. In this model the interaction of a spin qubit with substrate is considered in GSH at the calculation of exchange integrals Jij of the nanosystem Ni7-Si in the one-electron approach taking into account chemical bonds of all Si-atoms of a substrate (environment) with atoms of the Ni7-cluster. The energy pattern was found from the effective GSH Hamiltonian acting in the restricted spin space of the Ni ions by the application of the irreducible tensor operators (ITO) technique. In this paper we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on the silicon surface. The solution of the problem of the entanglement between spin states in the N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement (DOE). In this study we have developed and used the advanced high-precision numerical techniques to accurately assess the details of the decoherence process governing the dynamics of the N-spin qubits interacting with a silicon surface. We have studied the Rabi oscillations to evaluate the N-spin qubits system as a function of the time and the magnetic field. We have observed the stabilized Rabi oscillations and have stabilized the quantum dynamical qubit state and Rabi driving after a fixed time (0.327 μs). The comparison of the energy pattern with the
Role of spin-orbit coupling in the Kugel-Khomskii model on the honeycomb lattice
Koga, Akihisa; Nakauchi, Shiryu; Nasu, Joji
2018-03-01
We study the effective spin-orbital model for honeycomb-layered transition metal compounds, applying the second-order perturbation theory to the three-orbital Hubbard model with the anisotropic hoppings. This model is reduced to the Kitaev model in the strong spin-orbit coupling limit. Combining the cluster mean-field approximations with the exact diagonalization, we treat the Kugel-Khomskii type superexchange interaction and spin-orbit coupling on an equal footing to discuss ground-state properties. We find that a zigzag ordered state is realized in the model within nearest-neighbor interactions. We clarify how the ordered state competes with the nonmagnetic state, which is adiabatically connected to the quantum spin liquid state realized in a strong spin-orbit coupling limit. Thermodynamic properties are also addressed. The present paper should provide another route to account for the Kitaev-based magnetic properties in candidate materials.
The bond diluted spin-1 Blume-Emery-Griffiths model in a transverse field
International Nuclear Information System (INIS)
Ez Zahraouy, H.
1993-09-01
The effect of Bond-dilution on the magnetic properties of a quantum transverse spin-1 Blume-Emery-Griffiths model is investigated within an expansion technique for cluster identities of a spin-1 localized spin system. The longitudinal and transverse magnetizations and quadrupolar moments are studied for several values of the bond concentration. A general formula, applicable to structures with arbitrary coordination number N, are given. (author). 41 refs, 6 figs
A global central banker competency model
Directory of Open Access Journals (Sweden)
David W. Brits
2014-07-01
Full Text Available Orientation: No comprehensive, integrated competency model exists for central bankers. Due to the importance of central banks in the context of the ongoing global financial crisis, it was deemed necessary to design and validate such a model. Research purpose: To craft and validate a comprehensive, integrated global central banker competency model (GCBCM and to assess whether central banks using the GCBCM for training have a higher global influence. Motivation for the study: Limited consensus exists globally about what constitutes a ‘competent’ central banker. A quantitatively validated GCBCM would make a significant contribution to enhancing central banker effectiveness, and also provide a solid foundation for effective people management. Research approach, design and method: A blended quantitative and qualitative research approach was taken. Two sets of hypotheses were tested regarding the relationships between the GCBCM and the training offered, using the model on the one hand, and a central bank’s global influence on the other. Main findings: The GCBCM was generally accepted across all participating central banks globally, although some differences were found between central banks with higher and lower global influence. The actual training offered by central banks in terms of the model, however, is generally limited to technical-functional skills. The GCBCM is therefore at present predominantly aspirational. Significant differences were found regarding the training offered. Practical/managerial implications: By adopting the GCBCM, central banks would be able to develop organisation-specific competency models in order to enhance their organisational capabilities and play their increasingly important global role more effectively. Contribution: A generic conceptual framework for the crafting of a competency model with evaluation criteria was developed. A GCBCM was quantitatively validated.
Regional forecasting with global atmospheric models
International Nuclear Information System (INIS)
Crowley, T.J.; North, G.R.; Smith, N.R.
1994-05-01
The scope of the report is to present the results of the fourth year's work on the atmospheric modeling part of the global climate studies task. The development testing of computer models and initial results are discussed. The appendices contain studies that provide supporting information and guidance to the modeling work and further details on computer model development. Complete documentation of the models, including user information, will be prepared under separate reports and manuals
Coupled intertwiner dynamics: A toy model for coupling matter to spin foam models
Steinhaus, Sebastian
2015-09-01
The universal coupling of matter and gravity is one of the most important features of general relativity. In quantum gravity, in particular spin foams, matter couplings have been defined in the past, yet the mutual dynamics, in particular if matter and gravity are strongly coupled, are hardly explored, which is related to the definition of both matter and gravitational degrees of freedom on the discretization. However, extracting these mutual dynamics is crucial in testing the viability of the spin foam approach and also establishing connections to other discrete approaches such as lattice gauge theories. Therefore, we introduce a simple two-dimensional toy model for Yang-Mills coupled to spin foams, namely an Ising model coupled to so-called intertwiner models defined for SU (2 )k. The two systems are coupled by choosing the Ising coupling constant to depend on spin labels of the background, as these are interpreted as the edge lengths of the discretization. We coarse grain this toy model via tensor network renormalization and uncover an interesting dynamics: the Ising phase transition temperature turns out to be sensitive to the background configurations and conversely, the Ising model can induce phase transitions in the background. Moreover, we observe a strong coupling of both systems if close to both phase transitions.
Directory of Open Access Journals (Sweden)
J. Y. Xia
2012-10-01
Full Text Available The spin-up of land models to steady state of coupled carbon–nitrogen processes is computationally so costly that it becomes a bottleneck issue for global analysis. In this study, we introduced a semi-analytical solution (SAS for the spin-up issue. SAS is fundamentally based on the analytic solution to a set of equations that describe carbon transfers within ecosystems over time. SAS is implemented by three steps: (1 having an initial spin-up with prior pool-size values until net primary productivity (NPP reaches stabilization, (2 calculating quasi-steady-state pool sizes by letting fluxes of the equations equal zero, and (3 having a final spin-up to meet the criterion of steady state. Step 2 is enabled by averaged time-varying variables over one period of repeated driving forcings. SAS was applied to both site-level and global scale spin-up of the Australian Community Atmosphere Biosphere Land Exchange (CABLE model. For the carbon-cycle-only simulations, SAS saved 95.7% and 92.4% of computational time for site-level and global spin-up, respectively, in comparison with the traditional method (a long-term iterative simulation to achieve the steady states of variables. For the carbon–nitrogen coupled simulations, SAS reduced computational cost by 84.5% and 86.6% for site-level and global spin-up, respectively. The estimated steady-state pool sizes represent the ecosystem carbon storage capacity, which was 12.1 kg C m^{−2} with the coupled carbon–nitrogen global model, 14.6% lower than that with the carbon-only model. The nitrogen down-regulation in modeled carbon storage is partly due to the 4.6% decrease in carbon influx (i.e., net primary productivity and partly due to the 10.5% reduction in residence times. This steady-state analysis accelerated by the SAS method can facilitate comparative studies of structural differences in determining the ecosystem carbon storage capacity among biogeochemical models. Overall, the
Global-warming forecasting models
International Nuclear Information System (INIS)
Moeller, K.P.
1992-01-01
In spite of an annual man-made quantity of about 20 billion tons, carbon dioxide has remained a trace gas in the atmosphere (350 ppm at present). The reliability of model calculations which forecast temperatures is dicussed in view of the world-wide increase in carbon dioxides. Computer simulations reveal a general, serious threat to the future of mankind. (DG) [de
Exact ground and excited states of an antiferromagnetic quantum spin model
International Nuclear Information System (INIS)
Bose, I.
1989-08-01
A quasi-one-dimensional spin model which consists of a chain of octahedra of spins has been suggested for which a certain parameter regime of the Hamiltonian, the ground state, can be written down exactly. The ground state is highly degenerate and can be other than a singlet. Also, several excited states can be constructed exactly. The ground state is a local RVB state for which resonance is confined to rings of spins. Some exact numerical results for an octahedron of spins have also been reported. (author). 16 refs, 2 figs, 1 tab
From equilibrium spin models to probabilistic cellular automata
International Nuclear Information System (INIS)
Georges, A.; Le Doussal, P.
1989-01-01
The general equivalence between D-dimensional probabilistic cellular automata (PCA) and (D + 1)-dimensional equilibrium spin models satisfying a disorder condition is first described in a pedagogical way and then used to analyze the phase diagrams, the critical behavior, and the universality classes of some automato. Diagrammatic representations of time-dependent correlation functions PCA are introduced. Two important classes of PCA are singled out for which these correlation functions simplify: (1) Quasi-Hamiltonian automata, which have a current-carrying steady state, and for which some correlation functions are those of a D-dimensional static model PCA satisfying the detailed balance condition appear as a particular case of these rules for which the current vanishes. (2) Linear (and more generally affine) PCA for which the diagrammatics reduces to a random walk problem closely related to (D + 1)-dimensional directed SAWs: both problems display a critical behavior with mean-field exponents in any dimension. The correlation length and effective velocity of propagation of excitations can be calculated for affine PCA, as is shown on an explicit D = 1 example. The authors conclude with some remarks on nonlinear PCA, for which the diagrammatics is related to reaction-diffusion processes, and which belong in some cases to the universality class of Reggeon field theory
Technical Note: Reducing the spin-up time of integrated surface water–groundwater models
Ajami, H.; Evans, J. P.; McCabe, Matthew; Stisen, S.
2014-01-01
uncertainty in model initialization is to run the model recursively using a single or multiple years of forcing data until the system equilibrates with respect to state and diagnostic variables. However, such "spin-up" approaches often require many years
International Nuclear Information System (INIS)
Yamaji, Youhei; Misawa, Takahiro; Yoshimi, Kazuyoshi; Kawamura, Mitsuaki; Kawashima, Naoki; Todo, Synge
2017-01-01
HΦ is a program package based on the Lanczos-type method applicable to a broad range of quantum lattice models. HΦ has a flexible and simple-to-use interface, and runs efficiently on massively parallel computers. Unlike most existing packages, HΦ supports finite-temperature calculations. In this article, we apply HΦ to typical strongly correlated electron systems in proximity to quantum spin liquids. (author)
Central Limit Theorem for Exponentially Quasi-local Statistics of Spin Models on Cayley Graphs
Reddy, Tulasi Ram; Vadlamani, Sreekar; Yogeshwaran, D.
2018-04-01
Central limit theorems for linear statistics of lattice random fields (including spin models) are usually proven under suitable mixing conditions or quasi-associativity. Many interesting examples of spin models do not satisfy mixing conditions, and on the other hand, it does not seem easy to show central limit theorem for local statistics via quasi-associativity. In this work, we prove general central limit theorems for local statistics and exponentially quasi-local statistics of spin models on discrete Cayley graphs with polynomial growth. Further, we supplement these results by proving similar central limit theorems for random fields on discrete Cayley graphs taking values in a countable space, but under the stronger assumptions of α -mixing (for local statistics) and exponential α -mixing (for exponentially quasi-local statistics). All our central limit theorems assume a suitable variance lower bound like many others in the literature. We illustrate our general central limit theorem with specific examples of lattice spin models and statistics arising in computational topology, statistical physics and random networks. Examples of clustering spin models include quasi-associated spin models with fast decaying covariances like the off-critical Ising model, level sets of Gaussian random fields with fast decaying covariances like the massive Gaussian free field and determinantal point processes with fast decaying kernels. Examples of local statistics include intrinsic volumes, face counts, component counts of random cubical complexes while exponentially quasi-local statistics include nearest neighbour distances in spin models and Betti numbers of sub-critical random cubical complexes.
On Models with Uncountable Set of Spin Values on a Cayley Tree: Integral Equations
International Nuclear Information System (INIS)
Rozikov, Utkir A.; Eshkobilov, Yusup Kh.
2010-01-01
We consider models with nearest-neighbor interactions and with the set [0, 1] of spin values, on a Cayley tree of order k ≥ 1. We reduce the problem of describing the 'splitting Gibbs measures' of the model to the description of the solutions of some nonlinear integral equation. For k = 1 we show that the integral equation has a unique solution. In case k ≥ 2 some models (with the set [0, 1] of spin values) which have a unique splitting Gibbs measure are constructed. Also for the Potts model with uncountable set of spin values it is proven that there is unique splitting Gibbs measure.
Incorporating implementation overheads in the analysis for the flexible spin-lock model
Balasubramanian, S.M.N.; Afshar, S.; Gai, P.; Behnam, M.; Bril, R.J.
2017-01-01
The flexible spin-lock model (FSLM) unifies suspension-based and spin-based resource sharing protocols for partitioned fixed-priority preemptive scheduling based real-time multiprocessor platforms. Recent work has been done in defining the protocol for FSLM and providing a schedulability analysis
Engineering the Dynamics of Effective Spin-Chain Models for Strongly Interacting Atomic Gases
DEFF Research Database (Denmark)
Volosniev, A. G.; Petrosyan, D.; Valiente, M.
2015-01-01
We consider a one-dimensional gas of cold atoms with strong contact interactions and construct an effective spin-chain Hamiltonian for a two-component system. The resulting Heisenberg spin model can be engineered by manipulating the shape of the external confining potential of the atomic gas. We...
AN-type Dunkl operators and new spin Calogero-Sutherland models
International Nuclear Information System (INIS)
Finkel, F.; Gomez-Ullate, D.; Gonzalez-Lopez, A.; Rodriguez, M.A.; Zhdanov, R.
2001-01-01
A new family of A N -type Dunkl operators preserving a polynomial subspace of finite dimension is constructed. Using a general quadratic combination of these operators and the usual Dunkl operators, several new families of exactly and quasi-exactly solvable quantum spin Calogero-Sutherland models are obtained. These include, in particular, three families of quasi-exactly solvable elliptic spin Hamiltonians. (orig.)
Qualitative models of global warming amplifiers
Milošević, U.; Bredeweg, B.; de Kleer, J.; Forbus, K.D.
2010-01-01
There is growing interest from ecological experts to create qualitative models of phenomena for which numerical information is sparse or missing. We present a number of successful models in the field of environmental science, namely, the domain of global warming. The motivation behind the effort is
Technology Learning Ratios in Global Energy Models
International Nuclear Information System (INIS)
Varela, M.
2001-01-01
The process of introduction of a new technology supposes that while its production and utilisation increases, also its operation improves and its investment costs and production decreases. The accumulation of experience and learning of a new technology increase in parallel with the increase of its market share. This process is represented by the technological learning curves and the energy sector is not detached from this process of substitution of old technologies by new ones. The present paper carries out a brief revision of the main energy models that include the technology dynamics (learning). The energy scenarios, developed by global energy models, assume that the characteristics of the technologies are variables with time. But this trend is incorporated in a exogenous way in these energy models, that is to say, it is only a time function. This practice is applied to the cost indicators of the technology such as the specific investment costs or to the efficiency of the energy technologies. In the last years, the new concept of endogenous technological learning has been integrated within these global energy models. This paper examines the concept of technological learning in global energy models. It also analyses the technological dynamics of the energy system including the endogenous modelling of the process of technological progress. Finally, it makes a comparison of several of the most used global energy models (MARKAL, MESSAGE and ERIS) and, more concretely, about the use these models make of the concept of technological learning. (Author) 17 refs
Coherent manipulation of spin correlations in the Hubbard model
Wurz, N.; Chan, C. F.; Gall, M.; Drewes, J. H.; Cocchi, E.; Miller, L. A.; Pertot, D.; Brennecke, F.; Köhl, M.
2018-05-01
We coherently manipulate spin correlations in a two-component atomic Fermi gas loaded into an optical lattice using spatially and time-resolved Ramsey spectroscopy combined with high-resolution in situ imaging. This technique allows us not only to imprint spin patterns but also to probe the static magnetic structure factor at an arbitrary wave vector, in particular, the staggered structure factor. From a measurement along the diagonal of the first Brillouin zone of the optical lattice, we determine the magnetic correlation length and the individual spatial spin correlators. At half filling, the staggered magnetic structure factor serves as a sensitive thermometer, which we employ to study the equilibration in the spin and density sector during a slow quench of the lattice depth.
CFD model of a spinning pipe gas lens
CSIR Research Space (South Africa)
Snedden, Glen C
2006-07-01
Full Text Available Slides on: Spinning Pipe Gas Lens; Focal Length; Refractive Index; Gas Dynamics; Guess at the gas dynamics; Density Profile; Flow Profile; Rosby Waves; Rayleigh–Taylor Instabilities...
Higher spin currents in the enhanced N=3 Kazama-Suzuki model
Energy Technology Data Exchange (ETDEWEB)
Ahn, Changhyun; Kim, Hyunsu [Department of Physics, Kyungpook National University,Taegu 41566 (Korea, Republic of)
2016-12-01
The N=3 Kazama-Suzuki model at the ‘critical’ level has been found by Creutzig, Hikida and Ronne. We construct the lowest higher spin currents of spins ((3/2),2,2,2,(5/2),(5/2),(5/2),3) in terms of various fermions. In order to obtain the operator product expansions (OPEs) between these higher spin currents, we describe three N=2 OPEs between the two N=2 higher spin currents denoted by ((3/2),2,2,(5/2)) and (2,(5/2),(5/2),3) (corresponding 36 OPEs in the component approach). Using the various Jacobi identities, the coefficient functions appearing on the right hand side of these N=2 OPEs are determined in terms of central charge completely. Then we describe them as one single N=3 OPE in the N=3 superspace. The right hand side of this N=3 OPE contains the SO(3)-singlet N=3 higher spin multiplet of spins (2,(5/2),(5/2),(5/2),3,3,3,(7/2)), the SO(3)-singlet N=3 higher spin multiplet of spins ((5/2),3,3,3,(7/2),(7/2),(7/2),4), and the SO(3)-triplet N=3 higher spin multiplets where each multiplet has the spins (3,(7/2),(7/2),(7/2),4,4,4,(9/2)), in addition to N=3 superconformal family of the identity operator. Finally, by factoring out the spin-(1/2) current of N=3 linear superconformal algebra generated by eight currents of spins ((1/2),1,1,1,(3/2),(3/2),(3/2),2), we obtain the extension of so-called SO(3) nonlinear Knizhnik Bershadsky algebra.
New global ICT-based business models
DEFF Research Database (Denmark)
The New Global Business model (NEWGIBM) book describes the background, theory references, case studies, results and learning imparted by the NEWGIBM project, which is supported by ICT, to a research group during the period from 2005-2011. The book is a result of the efforts and the collaborative ...... The NEWGIBM Cases Show? The Strategy Concept in Light of the Increased Importance of Innovative Business Models Successful Implementation of Global BM Innovation Globalisation Of ICT Based Business Models: Today And In 2020......The New Global Business model (NEWGIBM) book describes the background, theory references, case studies, results and learning imparted by the NEWGIBM project, which is supported by ICT, to a research group during the period from 2005-2011. The book is a result of the efforts and the collaborative....... The NEWGIBM book serves as a part of the final evaluation and documentation of the NEWGIBM project and is supported by results from the following projects: M-commerce, Global Innovation, Global Ebusiness & M-commerce, The Blue Ocean project, International Center for Innovation and Women in Business, NEFFICS...
A high resolution global scale groundwater model
de Graaf, Inge; Sutanudjaja, Edwin; van Beek, Rens; Bierkens, Marc
2014-05-01
As the world's largest accessible source of freshwater, groundwater plays a vital role in satisfying the basic needs of human society. It serves as a primary source of drinking water and supplies water for agricultural and industrial activities. During times of drought, groundwater storage provides a large natural buffer against water shortage and sustains flows to rivers and wetlands, supporting ecosystem habitats and biodiversity. Yet, the current generation of global scale hydrological models (GHMs) do not include a groundwater flow component, although it is a crucial part of the hydrological cycle. Thus, a realistic physical representation of the groundwater system that allows for the simulation of groundwater head dynamics and lateral flows is essential for GHMs that increasingly run at finer resolution. In this study we present a global groundwater model with a resolution of 5 arc-minutes (approximately 10 km at the equator) using MODFLOW (McDonald and Harbaugh, 1988). With this global groundwater model we eventually intend to simulate the changes in the groundwater system over time that result from variations in recharge and abstraction. Aquifer schematization and properties of this groundwater model were developed from available global lithological maps and datasets (Dürr et al., 2005; Gleeson et al., 2010; Hartmann and Moosdorf, 2013), combined with our estimate of aquifer thickness for sedimentary basins. We forced the groundwater model with the output from the global hydrological model PCR-GLOBWB (van Beek et al., 2011), specifically the net groundwater recharge and average surface water levels derived from routed channel discharge. For the parameterization, we relied entirely on available global datasets and did not calibrate the model so that it can equally be expanded to data poor environments. Based on our sensitivity analysis, in which we run the model with various hydrogeological parameter settings, we observed that most variance in groundwater
Modeling Global Biogenic Emission of Isoprene: Exploration of Model Drivers
Alexander, Susan E.; Potter, Christopher S.; Coughlan, Joseph C.; Klooster, Steven A.; Lerdau, Manuel T.; Chatfield, Robert B.; Peterson, David L. (Technical Monitor)
1996-01-01
Vegetation provides the major source of isoprene emission to the atmosphere. We present a modeling approach to estimate global biogenic isoprene emission. The isoprene flux model is linked to a process-based computer simulation model of biogenic trace-gas fluxes that operates on scales that link regional and global data sets and ecosystem nutrient transformations Isoprene emission estimates are determined from estimates of ecosystem specific biomass, emission factors, and algorithms based on light and temperature. Our approach differs from an existing modeling framework by including the process-based global model for terrestrial ecosystem production, satellite derived ecosystem classification, and isoprene emission measurements from a tropical deciduous forest. We explore the sensitivity of model estimates to input parameters. The resulting emission products from the global 1 degree x 1 degree coverage provided by the satellite datasets and the process model allow flux estimations across large spatial scales and enable direct linkage to atmospheric models of trace-gas transport and transformation.
Emergent Chiral Spin State in the Mott Phase of a Bosonic Kane-Mele-Hubbard Model
Plekhanov, Kirill; Vasić, Ivana; Petrescu, Alexandru; Nirwan, Rajbir; Roux, Guillaume; Hofstetter, Walter; Le Hur, Karyn
2018-04-01
Recently, the frustrated X Y model for spins 1 /2 on the honeycomb lattice has attracted a lot of attention in relation with the possibility to realize a chiral spin liquid state. This model is relevant to the physics of some quantum magnets. Using the flexibility of ultracold atom setups, we propose an alternative way to realize this model through the Mott regime of the bosonic Kane-Mele-Hubbard model. The phase diagram of this model is derived using bosonic dynamical mean-field theory. Focusing on the Mott phase, we investigate its magnetic properties as a function of frustration. We do find an emergent chiral spin state in the intermediate frustration regime. Using exact diagonalization we study more closely the physics of the effective frustrated X Y model and the properties of the chiral spin state. This gapped phase displays a chiral order, breaking time-reversal and parity symmetry, but is not topologically ordered (the Chern number is zero).
Magnetic properties of a ferromagnet spin-S, Ising, XY and Heisenberg models semi-infinites systems
International Nuclear Information System (INIS)
Masrour, R.; Hamedoun, M.; Hourmatallah, A.; Bouslykhane, K.; Benzakour, N.
2008-01-01
The magnetic properties of a ferromagnet spin-S a disordered semi-infinite system with a face-centered cubic lattice are investigated using the high-temperature series expansions technique extrapolated with Pade approximants method for Heisenberg, XY and Ising models. The reduced critical temperature of the system τ c =(k B T c )/(2S(S+1)J b ) is studied as function of the thickness of the film and the exchange interactions in the bulk, and within the surfaces J b ,J s and J perpendicular , respectively. It is found that τ c increases with the exchange interactions of surface. The magnetic phase diagrams (τ c versus the dilution x) and the percolation threshold are obtained
Klokishner, Sophia I; Roman, Marianna A; Reu, Oleg S
2011-11-21
A microscopic approach to the problem of cooperative spin crossover in the [MnL2]NO3 crystal, which contains Mn(III) ions as structural units, is elaborated on, and the main mechanisms governing this effect are revealed. The proposed model also takes into account the splitting of the low-spin 3T1 (t(2)(4)) and high-spin 5E (t(2)(3)e) terms by the low-symmetry crystal field. The low-spin → high-spin transition has been considered as a cooperative phenomenon driven by interaction of the electronic shells of the Mn(III) ions with the all-around full-symmetric deformation that is extended over the crystal lattice via the acoustic phonon field. The model well explains the observed thermal dependencies of the magnetic susceptibility and the effective magnetic moment.
Spin-splitting calculation for zincblende semiconductors using an atomic bond-orbital model
International Nuclear Information System (INIS)
Kao, Hsiu-Fen; Lo, Ikai; Chiang, Jih-Chen; Wang, Wan-Tsang; Hsu, Yu-Chi; Wu, Chieh-Lung; Gau, Ming-Hong; Chen, Chun-Nan; Ren, Chung-Yuan; Lee, Meng-En
2012-01-01
We develop a 16-band atomic bond-orbital model (16ABOM) to compute the spin splitting induced by bulk inversion asymmetry in zincblende materials. This model is derived from the linear combination of atomic-orbital (LCAO) scheme such that the characteristics of the real atomic orbitals can be preserved to calculate the spin splitting. The Hamiltonian of 16ABOM is based on a similarity transformation performed on the nearest-neighbor LCAO Hamiltonian with a second-order Taylor expansion over k-vector at the Γ point. The spin-splitting energies in bulk zincblende semiconductors, GaAs and InSb, are calculated, and the results agree with the LCAO and first-principles calculations. However, we find that the spin-orbit coupling between bonding and antibonding p-like states, evaluated by the 16ABOM, dominates the spin splitting of the lowest conduction bands in the zincblende materials.
Environment overwhelms both nature and nurture in a model spin glass
Middleton, A. Alan; Yang, Jie
We are interested in exploring what information determines the particular history of the glassy long term dynamics in a disordered material. We study the effect of initial configurations and the realization of stochastic dynamics on the long time evolution of configurations in a two-dimensional Ising spin glass model. The evolution of nearest neighbor correlations is computed using patchwork dynamics, a coarse-grained numerical heuristic for temporal evolution. The dependence of the nearest neighbor spin correlations at long time on both initial spin configurations and noise histories are studied through cross-correlations of long-time configurations and the spin correlations are found to be independent of both. We investigate how effectively rigid bond clusters coarsen. Scaling laws are used to study the convergence of configurations and the distribution of sizes of nearly rigid clusters. The implications of the computational results on simulations and phenomenological models of spin glasses are discussed. We acknowledge NSF support under DMR-1410937 (CMMT program).
Nested Bethe Ansatz for Spin Ladder Model with Open Boundary Conditions
International Nuclear Information System (INIS)
Wu Junfang; Zhang Chunmin; Yue Ruihong; Li Runling
2005-01-01
The nested Bethe ansatz (BA) method is applied to find the eigenvalues and the eigenvectors of the transfer matrix for spin-ladder model with open boundary conditions. Based on the reflection equation, we find the general diagonal solution, which determines the general boundary interaction in the Hamiltonian. We introduce the spin-ladder model with open boundary conditions. By finding the solution K ± of the reflection equation which determines the nontrivial boundary terms in the Hamiltonian, we diagonalize the transfer matrix of the spin-ladder model with open boundary conditions in the framework of nested BA.
Higher-spin currents in the Gross-Neveu model at 1/n{sup 2}
Energy Technology Data Exchange (ETDEWEB)
Manashov, A.N. [Institut für Theoretische Physik, Universität Hamburg,Hamburg, D-22761 (Germany); Institut für Theoretische Physik, Universität Regensburg,Regensburg, D-93040 (Germany); Skvortsov, E.D. [Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians University Munich, Theresienstr. 37, Munich, D-80333 (Germany); Lebedev Institute of Physics,Leninsky ave. 53, Moscow, 119991 (Russian Federation)
2017-01-30
We calculate the anomalous dimensions of higher-spin currents, both singlet and non-singlet, in the Gross-Neveu model at the 1/n{sup 2} order. It was conjectured that in the critical regime this model is dual to a higher-spin gauge theory on AdS{sub 4}. The AdS/CFT correspondence predicts that the masses of higher-spin fields correspond to the scaling dimensions of the singlet currents in the Gross-Neveu model.
International Nuclear Information System (INIS)
Nagadi, M.M.; Weisel, G.J.; Walter, R.L.; Delaroche, J.P.; Romain, P.
2004-01-01
Coupled-channel and dispersive-optical model analyses of published neutron scattering and reaction data for 27 Al, 59 Co, and 93 Nb at incident energies between 0.1 and 80 MeV have been performed. The resulting potentials are used to place constraints on the determination of the spin-spin interaction from published spin-spin cross-section measurements. For the three nuclei, the strength of the central real spin-spin potential, which was taken to have a surface plus volume shape, was found to be small. Volume integrals for this central potential component were determined to be in the 4-7 MeV fm 3 range and to decrease somewhat as mass number increases
Improved Analysis of GW150914 Using a Fully Spin-Precessing Waveform Model
Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Bejger, M.; Bell, A. S.; Berger, B. K.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Birnholtz, O.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Brunett, S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, C.; Casentini, J.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Cheeseboro, B. D.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dasgupta, A.; Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; De, S.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Devine, R. C.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etienne, Z.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Fauchon-Jones, E.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Fenyvesi, E.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gaebel, S.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gehrels, N.; Gemme, G.; Geng, P.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Henry, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jian, L.; Jiménez-Forteza, F.; Johnson, W. W.; Johnson-McDaniel, N. K.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; K, Haris; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kapadia, S. J.; Karki, S.; Karvinen, K. S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chi-Woong; Kim, Chunglee; Kim, J.; Kim, K.; Kim, N.; Kim, W.; Kim, Y.-M.; Kimbrell, S. J.; King, E. J.; King, P. J.; Kissel, J. S.; Klein, B.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kumar, R.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Lewis, J. B.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Lombardi, A. L.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lousto, C. O.; Lovelace, G.; Lück, H.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magaña Zertuche, L.; Magee, R. M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, A.; Miller, B. B.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Nedkova, K.; Nelemans, G.; Nelson, T. J. N.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Perri, L. M.; Pfeiffer, H. P.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poe, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Qiu, S.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci, F.; Riles, K.; Rizzo, M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O. E. S.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Setyawati, Y.; Shaddock, D. A.; Shaffer, T.; Shahriar, M. S.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stevenson, S. P.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tomlinson, C.; Tonelli, M.; Tornasi, Z.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; Vallisneri, M.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van der Sluys, M. V.; van Heijningen, J. V.; Vano-Vinuales, A.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Worden, J.; Wright, J. L.; Wu, D. S.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yu, H.; Yvert, M.; ZadroŻny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; Boyle, M.; Brügmann, B.; Campanelli, M.; Chu, T.; Clark, M.; Haas, R.; Hemberger, D.; Hinder, I.; Kidder, L. E.; Kinsey, M.; Laguna, P.; Ossokine, S.; Pan, Y.; Röver, C.; Scheel, M.; Szilagyi, B.; Teukolsky, S.; Zlochower, Y.; LIGO Scientific Collaboration; Virgo Collaboration
2016-10-01
This paper presents updated estimates of source parameters for GW150914, a binary black-hole coalescence event detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 [Abbott et al. Phys. Rev. Lett. 116, 061102 (2016).]. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] presented parameter estimation of the source using a 13-dimensional, phenomenological precessing-spin model (precessing IMRPhenom) and an 11-dimensional nonprecessing effective-one-body (EOB) model calibrated to numerical-relativity simulations, which forces spin alignment (nonprecessing EOBNR). Here, we present new results that include a 15-dimensional precessing-spin waveform model (precessing EOBNR) developed within the EOB formalism. We find good agreement with the parameters estimated previously [Abbott et al. Phys. Rev. Lett. 116, 241102 (2016).], and we quote updated component masses of 35-3+5 M⊙ and 3 0-4+3 M⊙ (where errors correspond to 90% symmetric credible intervals). We also present slightly tighter constraints on the dimensionless spin magnitudes of the two black holes, with a primary spin estimate <0.65 and a secondary spin estimate <0.75 at 90% probability. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] estimated the systematic parameter-extraction errors due to waveform-model uncertainty by combining the posterior probability densities of precessing IMRPhenom and nonprecessing EOBNR. Here, we find that the two precessing-spin models are in closer agreement, suggesting that these systematic errors are smaller than previously quoted.
Regional forecasting with global atmospheric models
International Nuclear Information System (INIS)
Crowley, T.J.; North, G.R.; Smith, N.R.
1994-05-01
This report was prepared by the Applied Research Corporation (ARC), College Station, Texas, under subcontract to Pacific Northwest Laboratory (PNL) as part of a global climate studies task. The task supports site characterization work required for the selection of a potential high-level nuclear waste repository and is part of the Performance Assessment Scientific Support (PASS) Program at PNL. The work is under the overall direction of the Office of Civilian Radioactive Waste Management (OCRWM), US Department of Energy Headquarters, Washington, DC. The scope of the report is to present the results of the third year's work on the atmospheric modeling part of the global climate studies task. The development testing of computer models and initial results are discussed. The appendices contain several studies that provide supporting information and guidance to the modeling work and further details on computer model development. Complete documentation of the models, including user information, will be prepared under separate reports and manuals
Covariant quantization of infinite spin particle models, and higher order gauge theories
International Nuclear Information System (INIS)
Edgren, Ludde; Marnelius, Robert
2006-01-01
Further properties of a recently proposed higher order infinite spin particle model are derived. Infinitely many classically equivalent but different Hamiltonian formulations are shown to exist. This leads to a condition of uniqueness in the quantization process. A consistent covariant quantization is shown to exist. Also a recently proposed supersymmetric version for half-odd integer spins is quantized. A general algorithm to derive gauge invariances of higher order Lagrangians is given and applied to the infinite spin particle model, and to a new higher order model for a spinning particle which is proposed here, as well as to a previously given higher order rigid particle model. The latter two models are also covariantly quantized
Global thermal models of the lithosphere
Cammarano, F.; Guerri, M.
2017-12-01
Unraveling the thermal structure of the outermost shell of our planet is key for understanding its evolution. We obtain temperatures from interpretation of global shear-velocity (VS) models. Long-wavelength thermal structure is well determined by seismic models and only slightly affected by compositional effects and uncertainties in mineral-physics properties. Absolute temperatures and gradients with depth, however, are not well constrained. Adding constraints from petrology, heat-flow observations and thermal evolution of oceanic lithosphere help to better estimate absolute temperatures in the top part of the lithosphere. We produce global thermal models of the lithosphere at different spatial resolution, up to spherical-harmonics degree 24, and provide estimated standard deviations. We provide purely seismic thermal (TS) model and hybrid models where temperatures are corrected with steady-state conductive geotherms on continents and cooling model temperatures on oceanic regions. All relevant physical properties, with the exception of thermal conductivity, are based on a self-consistent thermodynamical modelling approach. Our global thermal models also include density and compressional-wave velocities (VP) as obtained either assuming no lateral variations in composition or a simple reference 3-D compositional structure, which takes into account a chemically depleted continental lithosphere. We found that seismically-derived temperatures in continental lithosphere fit well, overall, with continental geotherms, but a large variation in radiogenic heat is required to reconcile them with heat flow (long wavelength) observations. Oceanic shallow lithosphere below mid-oceanic ridges and young oceans is colder than expected, confirming the possible presence of a dehydration boundary around 80 km depth already suggested in previous studies. The global thermal models should serve as the basis to move at a smaller spatial scale, where additional thermo-chemical variations
Spherical Process Models for Global Spatial Statistics
Jeong, Jaehong
2017-11-28
Statistical models used in geophysical, environmental, and climate science applications must reflect the curvature of the spatial domain in global data. Over the past few decades, statisticians have developed covariance models that capture the spatial and temporal behavior of these global data sets. Though the geodesic distance is the most natural metric for measuring distance on the surface of a sphere, mathematical limitations have compelled statisticians to use the chordal distance to compute the covariance matrix in many applications instead, which may cause physically unrealistic distortions. Therefore, covariance functions directly defined on a sphere using the geodesic distance are needed. We discuss the issues that arise when dealing with spherical data sets on a global scale and provide references to recent literature. We review the current approaches to building process models on spheres, including the differential operator, the stochastic partial differential equation, the kernel convolution, and the deformation approaches. We illustrate realizations obtained from Gaussian processes with different covariance structures and the use of isotropic and nonstationary covariance models through deformations and geographical indicators for global surface temperature data. To assess the suitability of each method, we compare their log-likelihood values and prediction scores, and we end with a discussion of related research problems.
Surface tension and Wulff shape for a lattice model without spin flip symmetry.
Bodineau, T
2003-01-01
We propose a new definition of surface tension and check it in a spin model of the Pirogov-Sinai class where the spin flip symmetry is broken. We study the model at low temperatures on the phase transitions line and prove: (i) existence of the surface tension in the thermodynamic limit, for any orientation of the surface and in all dimensions $d\\ge 2$; (ii) the Wulff shape constructed with such a surface tension coincides with the equilibrium shape of the cluster which appears when fixing the total spin magnetization (Wulff problem).
Spin foam models of Yang-Mills theory coupled to gravity
International Nuclear Information System (INIS)
Mikovic, A
2003-01-01
We construct a spin foam model of Yang-Mills theory coupled to gravity by using a discretized path integral of the BF theory with polynomial interactions and the Barrett-Crane ansatz. In the Euclidean gravity case, we obtain a vertex amplitude which is determined by a vertex operator acting on a simple spin network function. The Euclidean gravity results can be straightforwardly extended to the Lorentzian case, so that we propose a Lorentzian spin foam model of Yang-Mills theory coupled to gravity
Higher spin currents in the critical O(N) vector model at 1/N2
International Nuclear Information System (INIS)
Manashov, A.N.; Strohmaier, M.
2017-06-01
We calculate the anomalous dimensions of higher spin singlet currents in the critical O(N) vector model at order 1/N 2 . The results are shown to be in agreement with the four-loop perturbative computation in φ 4 theory in 4-2ε dimensions. It is known that the order 1/N anomalous dimensions of higher-spin currents happen to be the same in the Gross-Neveu and the critical vector model. On the contrary, the order 1/N 2 corrections are different. The results can also be interpreted as a prediction for the two-loop computation in the dual higher-spin gravity.
On coupling global biome models with climate models
Claussen, M.
1994-01-01
The BIOME model of Prentice et al. (1992; J. Biogeogr. 19: 117-134), which predicts global vegetation patterns in equilibrium with climate, was coupled with the ECHAM climate model of the Max-Planck-Institut fiir Meteorologie, Hamburg, Germany. It was found that incorporation of the BIOME model into ECHAM, regardless at which frequency, does not enhance the simulated climate variability, expressed in terms of differences between global vegetation patterns. Strongest changes are seen only betw...
Spin squeezing as an indicator of quantum chaos in the Dicke model.
Song, Lijun; Yan, Dong; Ma, Jian; Wang, Xiaoguang
2009-04-01
We study spin squeezing, an intrinsic quantum property, in the Dicke model without the rotating-wave approximation. We show that the spin squeezing can reveal the underlying chaotic and regular structures in phase space given by a Poincaré section, namely, it acts as an indicator of quantum chaos. Spin squeezing vanishes after a very short time for an initial coherent state centered in a chaotic region, whereas it persists over a longer time for the coherent state centered in a regular region of the phase space. We also study the distribution of the mean spin directions when quantum dynamics takes place. Finally, we discuss relations among spin squeezing, bosonic quadrature squeezing, and two-qubit entanglement in the dynamical processes.
COLUMBUS. A global gas market model
Energy Technology Data Exchange (ETDEWEB)
Hecking, Harald; Panke, Timo
2012-03-15
A model of the global gas market is presented which in its basic version optimises the future development of production, transport and storage capacities as well as the actual gas flows around the world assuming perfect competition. Besides the transport of natural gas via pipelines also the global market for liquefied natural gas (LNG) is modelled using a hub-and-spoke approach. While in the basic version of the model an inelastic demand and a piecewise-linear supply function are used, both can be changed easily, e.g. to a Golombek style production function or a constant elasticity of substitution (CES) demand function. Due to the usage of mixed complementary programming (MCP) the model additionally allows for the simulation of strategic behaviour of different players in the gas market, e.g. the gas producers.
Current induced torques and interfacial spin-orbit coupling: Semiclassical modeling
Haney, Paul M.
2013-05-07
In bilayer nanowires consisting of a ferromagnetic layer and a nonmagnetic layer with strong spin-orbit coupling, currents create torques on the magnetization beyond those found in simple ferromagnetic nanowires. The resulting magnetic dynamics appear to require torques that can be separated into two terms, dampinglike and fieldlike. The dampinglike torque is typically derived from models describing the bulk spin Hall effect and the spin transfer torque, and the fieldlike torque is typically derived from a Rashba model describing interfacial spin-orbit coupling. We derive a model based on the Boltzmann equation that unifies these approaches. We also consider an approximation to the Boltzmann equation, the drift-diffusion model, that qualitatively reproduces the behavior, but quantitatively differs in some regimes. We show that the Boltzmann equation with physically reasonable parameters can match the torques for any particular sample, but in some cases, it fails to describe the experimentally observed thickness dependencies.
Stability and replica symmetry in the ising spin glass: a toy model
International Nuclear Information System (INIS)
De Dominicis, C.; Mottishaw, P.
1986-01-01
Searching for possible replica symmetric solutions in an Ising spin glass (in the tree approximation) we investigate a toy model whose bond distribution has two non vanishing cumulants (instead of one only as in a gaussian distribution)
Hidden spin-3/2 field in the standard model
Energy Technology Data Exchange (ETDEWEB)
Demir, Durmus; Karahan, Canan; Sargin, Ozan [Izmir Institute of Technology, Department of Physics, Urla (Turkey); Korutlu, Beste [TUeBITAK National Metrology Institute, Gebze, Kocaeli (Turkey)
2017-09-15
Here we show that a massive spin-3/2 field can hide in the SM spectrum in a way revealing itself only virtually. We study collider signatures and loop effects of this field, and determine its role in Higgs inflation and its potential as dark matter. We show that this spin-3/2 field has a rich linear collider phenomenology and motivates consideration of a neutrino-Higgs collider. We also show that the study of Higgs inflation, dark matter and dark energy can reveal more about the neutrino and dark sector. (orig.)
Model for decays of boson resonances with arbitrary spins
International Nuclear Information System (INIS)
Grigoryan, A.A.; Ivanov, N.Ya.
1985-01-01
A formula for the width of resonance with spin J decay into hadrons with arbitrary spins is derived. This width is expressed via S-channel helicity residues of Regge trajectory α J where the resonance J lies. Using the quark-gluon picture predictions for the coupling of quarks with Regge trajectories and SU(6)-classification of hadrons this formula is applied to calculate the widths of decays of resonances, which lie on the vector and tensor trajectories, into pseudoscalar and vector, two vectors and NN-bar-pair
Variance squeezing and entanglement of the XX central spin model
International Nuclear Information System (INIS)
El-Orany, Faisal A A; Abdalla, M Sebawe
2011-01-01
In this paper, we study the quantum properties for a system that consists of a central atom interacting with surrounding spins through the Heisenberg XX couplings of equal strength. Employing the Heisenberg equations of motion we manage to derive an exact solution for the dynamical operators. We consider that the central atom and its surroundings are initially prepared in the excited state and in the coherent spin state, respectively. For this system, we investigate the evolution of variance squeezing and entanglement. The nonclassical effects have been remarked in the behavior of all components of the system. The atomic variance can exhibit revival-collapse phenomenon based on the value of the detuning parameter.
Variance squeezing and entanglement of the XX central spin model
Energy Technology Data Exchange (ETDEWEB)
El-Orany, Faisal A A [Department of Mathematics and Computer Science, Faculty of Science, Suez Canal University, Ismailia (Egypt); Abdalla, M Sebawe, E-mail: m.sebaweh@physics.org [Mathematics Department, College of Science, King Saud University PO Box 2455, Riyadh 11451 (Saudi Arabia)
2011-01-21
In this paper, we study the quantum properties for a system that consists of a central atom interacting with surrounding spins through the Heisenberg XX couplings of equal strength. Employing the Heisenberg equations of motion we manage to derive an exact solution for the dynamical operators. We consider that the central atom and its surroundings are initially prepared in the excited state and in the coherent spin state, respectively. For this system, we investigate the evolution of variance squeezing and entanglement. The nonclassical effects have been remarked in the behavior of all components of the system. The atomic variance can exhibit revival-collapse phenomenon based on the value of the detuning parameter.
GLOMO - Global Mobility Model: Beschreibung und Ergebnisse
Kühn, André; Novinsky, Patrick; Schade, Wolfgang
2014-01-01
The development of both, emerging markets as well as the already establish markets (USA, Japan, Europe), is highly relevant for future success of the export-oriented German automotive industry. This paper describes the so called Global Mobility Model (GLOMO) based on the system dynamics approach, which simulates the future development of car sales by segment and drive technology. The modularized model contains population, income and GDP development in order to describe the framework in the mo...
Validation of A Global Hydrological Model
Doell, P.; Lehner, B.; Kaspar, F.; Vassolo, S.
Freshwater availability has been recognized as a global issue, and its consistent quan- tification not only in individual river basins but also at the global scale is required to support the sustainable use of water. The Global Hydrology Model WGHM, which is a submodel of the global water use and availability model WaterGAP 2, computes sur- face runoff, groundwater recharge and river discharge at a spatial resolution of 0.5. WGHM is based on the best global data sets currently available, including a newly developed drainage direction map and a data set of wetlands, lakes and reservoirs. It calculates both natural and actual discharge by simulating the reduction of river discharge by human water consumption (as computed by the water use submodel of WaterGAP 2). WGHM is calibrated against observed discharge at 724 gauging sta- tions (representing about 50% of the global land area) by adjusting a parameter of the soil water balance. It not only computes the long-term average water resources but also water availability indicators that take into account the interannual and seasonal variability of runoff and discharge. The reliability of the model results is assessed by comparing observed and simulated discharges at the calibration stations and at se- lected other stations. We conclude that reliable results can be obtained for basins of more than 20,000 km2. In particular, the 90% reliable monthly discharge is simu- lated well. However, there is the tendency that semi-arid and arid basins are modeled less satisfactorily than humid ones, which is partially due to neglecting river channel losses and evaporation of runoff from small ephemeral ponds in the model. Also, the hydrology of highly developed basins with large artificial storages, basin transfers and irrigation schemes cannot be simulated well. The seasonality of discharge in snow- dominated basins is overestimated by WGHM, and if the snow-dominated basin is uncalibrated, discharge is likely to be underestimated
A model for global cycling of tritium
International Nuclear Information System (INIS)
Killough, G.G.; Kocher, D.C.
1988-01-01
Dynamic compartment models are widely used to describe global cycling of radionuclides for purposes of dose estimation. In this paper the authors present a new global tritium model that reproduces environmental time-series data on concentrations in precipitation, ocean surface waters, and surface fresh waters in the northern hemisphere, concentrations of atmospheric tritium in the southern hemisphere, and the latitude dependence of tritium in both hemispheres. Names TRICYCLE (for TRItium CYCLE) the model is based on the global hydrologic cycle and includes hemispheric stratospheric compartments, disaggregation of the troposphere and ocean surface waters into eight latitude zones, consideration of the different concentrations of atmospheric tritium over land and over the ocean, and a diffusive model for transport in the ocean. TRICYCLE reproduces the environmental data if it is assumed that about 50% of the tritium from atmospheric weapons testing was injected directly into the northern stratosphere as HTO. The model's latitudinal disaggregation permits taking into account the distribution of population. For a uniformly distributed release of HTO into the worldwide troposphere, TRICYCLE predicts a collective dose commitment to the world population that exceeds the NCRP model's corresponding prediction by a factor of three
A model for global cycling of tritium
International Nuclear Information System (INIS)
Killough, G.G.; Kocher, D.C.
1988-01-01
Dynamic compartment models are widely used to describe global cycling of radionuclides for purposes of dose estimation. In this paper, we present a new global tritium model that reproduces environmental time-series data on concentrations in precipitation, ocean surface waters, and surface fresh waters in the northern hemisphere, concentrations of atmospheric tritium in the soutehrn hemisphere, and the latitude dependence of tritium in both hemispheres. Named TRICYCLE for Tritium CYCLE, the model is based on the global hydrologic cycle and includes hemisphereic stratospheric compartments, disaggregation of the troposphere and ocean surface waters into eight latitudezones, consideration of the different concentrations of atmospheric tritium over land and over the ocean, and a diffusive model for transport in the ocean. TRICYCLE reproduces the environmental data if we assume that about 50% of the tritium from atmospheric weapons testing was injected directly into the northern stratosphere as HTO. The models latitudinal disaggregation permits taking into account the distribution of population. For a unfiormaly distributed release of HTO into the worldwide troposphere, TRICYCLE predicts a collective dose commitment to the world population that exceeds the corresponding prediction by the NCRP model by about a factor of 3. 11 refs., 5 figs., 1 tab
International Nuclear Information System (INIS)
Vasconcelos Dos Santos, R.J.; Coutinho, S.
1995-01-01
The effect of a local field acting on decorating classical D-vector bond spins of an antiferromagnetic Ising model on the square lattice is studied for both the annealed isotropic and the axial decorated cases. In both models the effect on the phase diagrams of the transversal and the longitudinal components of the local field acting on the decorating spins are fully analyzed and discussed
On the validity of Brownian assumptions in the spin van der Waals model
International Nuclear Information System (INIS)
Oh, Suhk Kun
1985-01-01
A simple Brownian motion theory of the spin van der Waals model, which can be stationary, Markoffian or Gaussian, is studied. By comparing the Brownian motion theory with an exact theory called the generalized Langevin equation theory, the validity of the Brownian assumptions is tested. Thereby, it is shown explicitly how the Markoffian and Gaussian properties are modified in the spin van der Waals model under the influence of quantum fluctuations and long range ordering. (Author)
MODELING AND ANALYSIS OF COUPLED FLEXURAL-TORSIONAL SPINNING BEAMS WITH UNSYMMETRICAL CROSS SECTIONS
Wang, Jie; Li, Dongxu; Jiang, Jianping
2017-01-01
The structural modeling and dynamic properties of a spinning beam with an unsymmetrical cross section are studied. Due to the eccentricity and spinning, transverse deflections along the two principal directions and the torsional motion about the longitudinal axis are coupled. The structural model of the beam is established based on the Hamilton principle and by incorporating the torsional inertia. Moreover, because of its significant influence on characteristics for the non-circular cross-sec...
Variational approach for the N-state spin and gauge Potts model
International Nuclear Information System (INIS)
Masperi, L.; Omero, C.
1981-05-01
A hamiltonian variational treatment is applied both to the spin Potts model and to its gauge version for any number of states N and spatial dimensions d>=2. Regarding the former we reproduce correct critical coupling and latent heat for not too low N and d. For the latter, our approach turns the gauge theory into an equivalent d-dimensional classical spin model, which evaluated for d+1=4 gives results in agreement with 1/N expansions. (author)
Spin alignment and collective moment of inertia of the basic rotational band in the cranking model
International Nuclear Information System (INIS)
Tanaka, Yoshihide
1982-01-01
By making an attempt to separate the intrinsic particle and collective rotational motions in the cranking model, the spin alignment and the collective moment of inertia characterizing the basic rotational bands are defined, and are investigated by using a simple i sub(13/2) shell model. The result of the calculation indicates that the collective moment of inertia decreases under the presence of the quasiparticles which are responsible for the increase of the spin alignment of the band. (author)
Ajami, Hoori; McCabe, Matthew; Evans, Jason P.; Stisen, Simon
2014-01-01
is to minimize the impact of initialization while using the smallest spin-up time possible. In this study, multicriteria analysis was performed to assess the spin-up behavior of the ParFlow.CLM integrated groundwater-surface water-land surface model over a 208 km
Global nuclear material flow/control model
International Nuclear Information System (INIS)
Dreicer, J.S.; Rutherford, D.S.; Fasel, P.K.; Riese, J.M.
1997-01-01
This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The nuclear danger can be reduced by a system for global management, protection, control, and accounting as part of an international regime for nuclear materials. The development of an international fissile material management and control regime requires conceptual research supported by an analytical and modeling tool which treats the nuclear fuel cycle as a complete system. The prototype model developed visually represents the fundamental data, information, and capabilities related to the nuclear fuel cycle in a framework supportive of national or an international perspective. This includes an assessment of the global distribution of military and civilian fissile material inventories, a representation of the proliferation pertinent physical processes, facility specific geographic identification, and the capability to estimate resource requirements for the management and control of nuclear material. The model establishes the foundation for evaluating the global production, disposition, and safeguards and security requirements for fissile nuclear material and supports the development of other pertinent algorithmic capabilities necessary to undertake further global nuclear material related studies
Quantum phase transitions in effective spin-ladder models for graphene zigzag nanoribbons
Koop, Cornelie; Wessel, Stefan
2017-10-01
We examine the magnetic correlations in quantum spin models that were derived recently as effective low-energy theories for electronic correlation effects on the edge states of graphene nanoribbons. For this purpose, we employ quantum Monte Carlo simulations to access the large-distance properties, accounting for quantum fluctuations beyond mean-field-theory approaches to edge magnetism. For certain chiral nanoribbons, antiferromagnetic interedge couplings were previously found to induce a gapped quantum disordered ground state of the effective spin model. We find that the extended nature of the intraedge couplings in the effective spin model for zigzag nanoribbons leads to a quantum phase transition at a large, finite value of the interedge coupling. This quantum critical point separates the quantum disordered region from a gapless phase of stable edge magnetism at weak intraedge coupling, which includes the ground states of spin-ladder models for wide zigzag nanoribbons. To study the quantum critical behavior, the effective spin model can be related to a model of two antiferromagnetically coupled Haldane-Shastry spin-half chains with long-ranged ferromagnetic intrachain couplings. The results for the critical exponents are compared also to several recent renormalization-group calculations for related long-ranged interacting quantum systems.
Global Optimization Ensemble Model for Classification Methods
Anwar, Hina; Qamar, Usman; Muzaffar Qureshi, Abdul Wahab
2014-01-01
Supervised learning is the process of data mining for deducing rules from training datasets. A broad array of supervised learning algorithms exists, every one of them with its own advantages and drawbacks. There are some basic issues that affect the accuracy of classifier while solving a supervised learning problem, like bias-variance tradeoff, dimensionality of input space, and noise in the input data space. All these problems affect the accuracy of classifier and are the reason that there is no global optimal method for classification. There is not any generalized improvement method that can increase the accuracy of any classifier while addressing all the problems stated above. This paper proposes a global optimization ensemble model for classification methods (GMC) that can improve the overall accuracy for supervised learning problems. The experimental results on various public datasets showed that the proposed model improved the accuracy of the classification models from 1% to 30% depending upon the algorithm complexity. PMID:24883382
Global Optimization Ensemble Model for Classification Methods
Directory of Open Access Journals (Sweden)
Hina Anwar
2014-01-01
Full Text Available Supervised learning is the process of data mining for deducing rules from training datasets. A broad array of supervised learning algorithms exists, every one of them with its own advantages and drawbacks. There are some basic issues that affect the accuracy of classifier while solving a supervised learning problem, like bias-variance tradeoff, dimensionality of input space, and noise in the input data space. All these problems affect the accuracy of classifier and are the reason that there is no global optimal method for classification. There is not any generalized improvement method that can increase the accuracy of any classifier while addressing all the problems stated above. This paper proposes a global optimization ensemble model for classification methods (GMC that can improve the overall accuracy for supervised learning problems. The experimental results on various public datasets showed that the proposed model improved the accuracy of the classification models from 1% to 30% depending upon the algorithm complexity.
Accuracy of binary black hole waveform models for aligned-spin binaries
Kumar, Prayush; Chu, Tony; Fong, Heather; Pfeiffer, Harald P.; Boyle, Michael; Hemberger, Daniel A.; Kidder, Lawrence E.; Scheel, Mark A.; Szilagyi, Bela
2016-05-01
Coalescing binary black holes are among the primary science targets for second generation ground-based gravitational wave detectors. Reliable gravitational waveform models are central to detection of such systems and subsequent parameter estimation. This paper performs a comprehensive analysis of the accuracy of recent waveform models for binary black holes with aligned spins, utilizing a new set of 84 high-accuracy numerical relativity simulations. Our analysis covers comparable mass binaries (mass-ratio 1 ≤q ≤3 ), and samples independently both black hole spins up to a dimensionless spin magnitude of 0.9 for equal-mass binaries and 0.85 for unequal mass binaries. Furthermore, we focus on the high-mass regime (total mass ≳50 M⊙ ). The two most recent waveform models considered (PhenomD and SEOBNRv2) both perform very well for signal detection, losing less than 0.5% of the recoverable signal-to-noise ratio ρ , except that SEOBNRv2's efficiency drops slightly for both black hole spins aligned at large magnitude. For parameter estimation, modeling inaccuracies of the SEOBNRv2 model are found to be smaller than systematic uncertainties for moderately strong GW events up to roughly ρ ≲15 . PhenomD's modeling errors are found to be smaller than SEOBNRv2's, and are generally irrelevant for ρ ≲20 . Both models' accuracy deteriorates with increased mass ratio, and when at least one black hole spin is large and aligned. The SEOBNRv2 model shows a pronounced disagreement with the numerical relativity simulation in the merger phase, for unequal masses and simultaneously both black hole spins very large and aligned. Two older waveform models (PhenomC and SEOBNRv1) are found to be distinctly less accurate than the more recent PhenomD and SEOBNRv2 models. Finally, we quantify the bias expected from all four waveform models during parameter estimation for several recovered binary parameters: chirp mass, mass ratio, and effective spin.
Global Analysis, Interpretation and Modelling: An Earth Systems Modelling Program
Moore, Berrien, III; Sahagian, Dork
1997-01-01
The Goal of the GAIM is: To advance the study of the coupled dynamics of the Earth system using as tools both data and models; to develop a strategy for the rapid development, evaluation, and application of comprehensive prognostic models of the Global Biogeochemical Subsystem which could eventually be linked with models of the Physical-Climate Subsystem; to propose, promote, and facilitate experiments with existing models or by linking subcomponent models, especially those associated with IGBP Core Projects and with WCRP efforts. Such experiments would be focused upon resolving interface issues and questions associated with developing an understanding of the prognostic behavior of key processes; to clarify key scientific issues facing the development of Global Biogeochemical Models and the coupling of these models to General Circulation Models; to assist the Intergovernmental Panel on Climate Change (IPCC) process by conducting timely studies that focus upon elucidating important unresolved scientific issues associated with the changing biogeochemical cycles of the planet and upon the role of the biosphere in the physical-climate subsystem, particularly its role in the global hydrological cycle; and to advise the SC-IGBP on progress in developing comprehensive Global Biogeochemical Models and to maintain scientific liaison with the WCRP Steering Group on Global Climate Modelling.
Global modelling of Cryptosporidium in surface water
Vermeulen, Lucie; Hofstra, Nynke
2016-04-01
Introduction Waterborne pathogens that cause diarrhoea, such as Cryptosporidium, pose a health risk all over the world. In many regions quantitative information on pathogens in surface water is unavailable. Our main objective is to model Cryptosporidium concentrations in surface waters worldwide. We present the GloWPa-Crypto model and use the model in a scenario analysis. A first exploration of global Cryptosporidium emissions to surface waters has been published by Hofstra et al. (2013). Further work has focused on modelling emissions of Cryptosporidium and Rotavirus to surface waters from human sources (Vermeulen et al 2015, Kiulia et al 2015). A global waterborne pathogen model can provide valuable insights by (1) providing quantitative information on pathogen levels in data-sparse regions, (2) identifying pathogen hotspots, (3) enabling future projections under global change scenarios and (4) supporting decision making. Material and Methods GloWPa-Crypto runs on a monthly time step and represents conditions for approximately the year 2010. The spatial resolution is a 0.5 x 0.5 degree latitude x longitude grid for the world. We use livestock maps (http://livestock.geo-wiki.org/) combined with literature estimates to calculate spatially explicit livestock Cryptosporidium emissions. For human Cryptosporidium emissions, we use UN population estimates, the WHO/UNICEF JMP sanitation country data and literature estimates of wastewater treatment. We combine our emissions model with a river routing model and data from the VIC hydrological model (http://vic.readthedocs.org/en/master/) to calculate concentrations in surface water. Cryptosporidium survival during transport depends on UV radiation and water temperature. We explore pathogen emissions and concentrations in 2050 with the new Shared Socio-economic Pathways (SSPs) 1 and 3. These scenarios describe plausible future trends in demographics, economic development and the degree of global integration. Results and
Global energy modeling - A biophysical approach
Energy Technology Data Exchange (ETDEWEB)
Dale, Michael
2010-09-15
This paper contrasts the standard economic approach to energy modelling with energy models using a biophysical approach. Neither of these approaches includes changing energy-returns-on-investment (EROI) due to declining resource quality or the capital intensive nature of renewable energy sources. Both of these factors will become increasingly important in the future. An extension to the biophysical approach is outlined which encompasses a dynamic EROI function that explicitly incorporates technological learning. The model is used to explore several scenarios of long-term future energy supply especially concerning the global transition to renewable energy sources in the quest for a sustainable energy system.
Energy Technology Data Exchange (ETDEWEB)
Farberovich, Oleg V. [School of Physics and Astronomy, Beverly and Raymond Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978 (Israel); Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation); Voronezh State University, Voronezh 394000 (Russian Federation); Mazalova, Victoria L., E-mail: mazalova@sfedu.ru [Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation); Soldatov, Alexander V. [Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation)
2015-11-15
We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density-functional scheme for the calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange coupling parameters linking the nickel ions with a silicon substrate. In this model the interaction of a spin qubit with substrate is considered in GSH at the calculation of exchange integrals J{sub ij} of the nanosystem Ni{sub 7}–Si in the one-electron approach taking into account chemical bonds of all Si-atoms of a substrate (environment) with atoms of the Ni{sub 7}-cluster. The energy pattern was found from the effective GSH Hamiltonian acting in the restricted spin space of the Ni ions by the application of the irreducible tensor operators (ITO) technique. In this paper we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on the silicon surface. The solution of the problem of the entanglement between spin states in the N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement (DOE). In this study we have developed and used the advanced high-precision numerical techniques to accurately assess the details of the decoherence process governing the dynamics of the N-spin qubits interacting with a silicon surface. We have studied the Rabi oscillations to evaluate the N-spin qubits system as a function of the time and the magnetic field. We have observed the stabilized Rabi oscillations and have stabilized the quantum dynamical qubit state and Rabi driving after a fixed time (0.327 μs). The comparison of the energy
International Nuclear Information System (INIS)
Farberovich, Oleg V.; Mazalova, Victoria L.; Soldatov, Alexander V.
2015-01-01
We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density-functional scheme for the calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange coupling parameters linking the nickel ions with a silicon substrate. In this model the interaction of a spin qubit with substrate is considered in GSH at the calculation of exchange integrals J ij of the nanosystem Ni 7 –Si in the one-electron approach taking into account chemical bonds of all Si-atoms of a substrate (environment) with atoms of the Ni 7 -cluster. The energy pattern was found from the effective GSH Hamiltonian acting in the restricted spin space of the Ni ions by the application of the irreducible tensor operators (ITO) technique. In this paper we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on the silicon surface. The solution of the problem of the entanglement between spin states in the N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement (DOE). In this study we have developed and used the advanced high-precision numerical techniques to accurately assess the details of the decoherence process governing the dynamics of the N-spin qubits interacting with a silicon surface. We have studied the Rabi oscillations to evaluate the N-spin qubits system as a function of the time and the magnetic field. We have observed the stabilized Rabi oscillations and have stabilized the quantum dynamical qubit state and Rabi driving after a fixed time (0.327 μs). The comparison of the energy pattern with
Lima, L. S.
2018-06-01
We study the effect of Dzyaloshisnkii-Moriya interaction on spin transport in the two and three-dimensional Heisenberg antiferromagnetic models in the square lattice and cubic lattice respectively. For the three-dimensional model, we obtain a large peak for the spin conductivity and therefore a finite AC conductivity. For the two-dimensional model, we have gotten the AC spin conductivity tending to the infinity at ω → 0 limit and a suave decreasing in the spin conductivity with increase of ω. We obtain a small influence of the Dzyaloshinskii-Moriya interaction on the spin conductivity in all cases analyzed.
Statistical models of global Langmuir mixing
Li, Qing; Fox-Kemper, Baylor; Breivik, Øyvind; Webb, Adrean
2017-05-01
The effects of Langmuir mixing on the surface ocean mixing may be parameterized by applying an enhancement factor which depends on wave, wind, and ocean state to the turbulent velocity scale in the K-Profile Parameterization. Diagnosing the appropriate enhancement factor online in global climate simulations is readily achieved by coupling with a prognostic wave model, but with significant computational and code development expenses. In this paper, two alternatives that do not require a prognostic wave model, (i) a monthly mean enhancement factor climatology, and (ii) an approximation to the enhancement factor based on the empirical wave spectra, are explored and tested in a global climate model. Both appear to reproduce the Langmuir mixing effects as estimated using a prognostic wave model, with nearly identical and substantial improvements in the simulated mixed layer depth and intermediate water ventilation over control simulations, but significantly less computational cost. Simpler approaches, such as ignoring Langmuir mixing altogether or setting a globally constant Langmuir number, are found to be deficient. Thus, the consequences of Stokes depth and misaligned wind and waves are important.
Rate equation modelling of the optically pumped spin-exchange source
International Nuclear Information System (INIS)
Stenger, J.; Rith, K.
1995-01-01
Sources for spin polarized hydrogen or deuterium, polarized via spin-exchange of a laser optically pumped alkali metal, can be modelled by rate equations. The rate equations for this type of source, operated either with hydrogen or deuterium, are given explicitly with the intention of providing a useful tool for further source optimization and understanding. Laser optical pumping of alkali metal, spin-exchange collisions of hydrogen or deuterium atoms with each other and with alkali metal atoms are included, as well as depolarization due to flow and wall collisions. (orig.)
Modeling of the Global Water Cycle - Analytical Models
Yongqiang Liu; Roni Avissar
2005-01-01
Both numerical and analytical models of coupled atmosphere and its underlying ground components (land, ocean, ice) are useful tools for modeling the global and regional water cycle. Unlike complex three-dimensional climate models, which need very large computing resources and involve a large number of complicated interactions often difficult to interpret, analytical...
An implementation of the flexible spin-lock model in ERIKA Enterprise on a multi-core platform
Afshar, S.; Verwielen, M.P.W.; Gai, P.; Behnam, M.; Bril, R.J.
2016-01-01
Recently, the flexible spin-lock model (FSLM) has been introduced, unifying spin-based and suspension-based resource sharing protocols for real-time multiprocessor platforms by explicitly identifying the spin-lock priority as a parameter. Earlier work focused on the definition of a protocol for FSLM
Global Environmental Change: An integrated modelling approach
International Nuclear Information System (INIS)
Den Elzen, M.
1993-01-01
Two major global environmental problems are dealt with: climate change and stratospheric ozone depletion (and their mutual interactions), briefly surveyed in part 1. In Part 2 a brief description of the integrated modelling framework IMAGE 1.6 is given. Some specific parts of the model are described in more detail in other Chapters, e.g. the carbon cycle model, the atmospheric chemistry model, the halocarbon model, and the UV-B impact model. In Part 3 an uncertainty analysis of climate change and stratospheric ozone depletion is presented (Chapter 4). Chapter 5 briefly reviews the social and economic uncertainties implied by future greenhouse gas emissions. Chapters 6 and 7 describe a model and sensitivity analysis pertaining to the scientific uncertainties and/or lacunae in the sources and sinks of methane and carbon dioxide, and their biogeochemical feedback processes. Chapter 8 presents an uncertainty and sensitivity analysis of the carbon cycle model, the halocarbon model, and the IMAGE model 1.6 as a whole. Part 4 presents the risk assessment methodology as applied to the problems of climate change and stratospheric ozone depletion more specifically. In Chapter 10, this methodology is used as a means with which to asses current ozone policy and a wide range of halocarbon policies. Chapter 11 presents and evaluates the simulated globally-averaged temperature and sea level rise (indicators) for the IPCC-1990 and 1992 scenarios, concluding with a Low Risk scenario, which would meet the climate targets. Chapter 12 discusses the impact of sea level rise on the frequency of the Dutch coastal defence system (indicator) for the IPCC-1990 scenarios. Chapter 13 presents projections of mortality rates due to stratospheric ozone depletion based on model simulations employing the UV-B chain model for a number of halocarbon policies. Chapter 14 presents an approach for allocating future emissions of CO 2 among regions. (Abstract Truncated)
Santhanam, K S V; Chen, Xu; Gupta, S
2014-04-01
Ab initio studies of ferromagnetic atom interacting with carbon nanotubes have been reported in the literature that predict when the interaction is strong, a higher hybridization with confinement effect will result in spin polarization in the ferromagnetic atom. The spin polarization effect on the thermal oxidation to form its oxide is modeled here for the ferromagnetic atom and its alloy, as the above studies predict the 4s electrons are polarized in the atom. The four models developed here provide a pathway for distinguishing the type of interaction that exists in the real system. The extent of spin polarization in the ferromagnetic atom has been examined by varying the amount of carbon nanotubes in the composites in the thermogravimetric experiments. In this study we report the experimental results on the CoNi alloy which appears to show selective spin polarization. The products of the thermal oxidation has been analyzed by Fourier Transform Infrared Spectroscopy.
Modelling and Analysis of a Collision Avoidance Protocol using SPIN and UPPAAL
DEFF Research Database (Denmark)
Skou, Arne; Larsen, Kim Guldstrand; Jensen, Henrik Ejersbo
1997-01-01
, the modelling of the media becomes ackward due to the lack of broadcast communication in the PROMELA language. On the other hand we find it easy to model the timed aspects using the UPPAAL tool. Especially, the notion of committed locations supports the modelling of broadcast communication. However......This paper compares the tools SPIN and UPPAAL by modelling and verifying a Collision Avoidance Protocol for an Ethernet-like medium. We find that SPIN is well suited for modelling the untimed aspects of the protocol processes and for expressing the relevant (untimed) properties. However...
Introduction to thermodynamics of spin models in the Hamiltonian limit
Energy Technology Data Exchange (ETDEWEB)
Berche, Bertrand [Groupe M, Laboratoire de Physique des Materiaux, UMR CNRS No 7556, Universite Henri Poincare, Nancy 1, BP 239, F-54506 Vandoeuvre les Nancy, (France); Lopez, Alexander [Instituto Venezolano de Investigaciones CientIficas, Centro de Fisica, Carr. Panamericana, km 11, Altos de Pipe, Aptdo 21827, 1020-A Caracas, (Venezuela)
2006-01-01
A didactic description of the thermodynamic properties of classical spin systems is given in terms of their quantum counterpart in the Hamiltonian limit. Emphasis is on the construction of the relevant Hamiltonian and the calculation of thermal averages is explicitly done in the case of small systems described, in Hamiltonian field theory, by small matrices. The targeted students are those of a graduate statistical physics course.
A linear dynamic model for rotor-spun composite yarn spinning process
International Nuclear Information System (INIS)
Yang, R H; Wang, S Y
2008-01-01
A linear dynamic model is established for the stable rotor-spun composite yarn spinning process. Approximate oscillating frequencies in the vertical and horizontal directions are obtained. By suitable choice of certain processing parameters, the mixture construction after the convergent point can be optimally matched. The presented study is expected to provide a general pathway to understand the motion of the rotor-spun composite yarn spinning process
[OsF6]x−: Molecular Models for Spin-Orbit Entangled Phenomena
DEFF Research Database (Denmark)
Pedersen, Kasper Steen; Woodruff, Daniel N.; Singh, Saurabh Kumar
2017-01-01
Heavy 5d elements, like osmium, feature strong spin-orbit interactions which are at the origin of exotic physical behaviors. Revealing the full potential of, for example, novel osmium oxide materials (“osmates”) is however contingent upon a detailed understanding of the local single-ion propertie...... state was elucidated; mirroring the osmium electronic structure in osmates. The realization of such molecular model systems provides a unique chemical playground to engineer materials exhibiting spin-orbit entangled phenomena....
From spinning conformal blocks to matrix Calogero-Sutherland models
Schomerus, Volker; Sobko, Evgeny
2018-04-01
In this paper we develop further the relation between conformal four-point blocks involving external spinning fields and Calogero-Sutherland quantum mechanics with matrix-valued potentials. To this end, the analysis of [1] is extended to arbitrary dimensions and to the case of boundary two-point functions. In particular, we construct the potential for any set of external tensor fields. Some of the resulting Schrödinger equations are mapped explicitly to the known Casimir equations for 4-dimensional seed conformal blocks. Our approach furnishes solutions of Casimir equations for external fields of arbitrary spin and dimension in terms of functions on the conformal group. This allows us to reinterpret standard operations on conformal blocks in terms of group-theoretic objects. In particular, we shall discuss the relation between the construction of spinning blocks in any dimension through differential operators acting on seed blocks and the action of left/right invariant vector fields on the conformal group.
One dimensionalization in the spin-1 Heisenberg model on the anisotropic triangular lattice
Gonzalez, M. G.; Ghioldi, E. A.; Gazza, C. J.; Manuel, L. O.; Trumper, A. E.
2017-11-01
We investigate the effect of dimensional crossover in the ground state of the antiferromagnetic spin-1 Heisenberg model on the anisotropic triangular lattice that interpolates between the regime of weakly coupled Haldane chains (J'≪J ) and the isotropic triangular lattice (J'=J ). We use the density-matrix renormalization group (DMRG) and Schwinger boson theory performed at the Gaussian correction level above the saddle-point solution. Our DMRG results show an abrupt transition between decoupled spin chains and the spirally ordered regime at (J'/J) c˜0.42 , signaled by the sudden closing of the spin gap. Coming from the magnetically ordered side, the computation of the spin stiffness within Schwinger boson theory predicts the instability of the spiral magnetic order toward a magnetically disordered phase with one-dimensional features at (J'/J) c˜0.43 . The agreement of these complementary methods, along with the strong difference found between the intra- and the interchain DMRG short spin-spin correlations for sufficiently large values of the interchain coupling, suggests that the interplay between the quantum fluctuations and the dimensional crossover effects gives rise to the one-dimensionalization phenomenon in this frustrated spin-1 Hamiltonian.
IMPROVING THE MODEL OF EMISSION FROM SPINNING DUST: EFFECTS OF GRAIN WOBBLING AND TRANSIENT SPIN-UP
International Nuclear Information System (INIS)
Hoang, Thiem; Lazarian, A.; Draine, B. T.
2010-01-01
Observations continue to support the interpretation of the anomalous microwave foreground as electric dipole radiation from spinning dust grains as proposed by Draine and Lazarian. In this paper, we present a refinement of the original model by improving the treatment of a number of physical effects. First, we consider a disk-like grain rotating with angular velocity at an arbitrary angle with respect to the grain symmetry axis (i.e., grain wobbling) and derive the rotational damping and excitation coefficients arising from infrared emission, plasma-grain interactions, and electric dipole emission. The angular velocity distribution and the electric dipole emission spectrum for disk-like grains is calculated using the Langevin equation, for cases both with and without fast internal relaxation. Our results show that for fast internal relaxation, the peak emissivity of spinning dust, compared to earlier studies, increases by a factor of ∼2 for the warm neutral medium (WNM), the warm ionized medium (WIM), the cold neutral medium (CNM), and the photodissociation region, and by a factor ∼4 for reflection nebulae. The frequency at the emission peak also increases by factors ∼1.4 to ∼2 for these media. Without internal relaxation, the increase of emissivity is comparable, but the emission spectrum is more extended to higher frequency. The increased emission results from the non-sphericity of grain shape and from the anisotropy in damping and excitation along directions parallel and perpendicular to the grain symmetry axis. Second, we provide a detailed numerical study including transient spin-up of grains by single-ion collisions. The range of grain size in which single-ion collisions are important is identified. The impulses broaden the emission spectrum and increase the peak emissivity for the CNM, WNM, and WIM, although the increases are not as large as those due to the grain wobbling. In addition, we present an improved treatment of rotational excitation and
A new spin on primordial hydrogen recombination and a refined model for spinning dust radiation
Ali-Haimoud, Yacine
2011-08-01
This thesis describes theoretical calculations in two subjects: the primordial recombination of the electron-proton plasma about 400,000 years after the Big Bang and electric dipole radiation from spinning dust grains in the present-day interstellar medium. Primordial hydrogen recombination has recently been the subject of a renewed attention because of the impact of its theoretical uncertainties on predicted cosmic microwave background (CMB) anisotropy power spectra. The physics of the primordial recombination problem can be divided into two qualitatively different aspects. On the one hand, a detailed treatment of the non-thermal radiation field in the optically thick Lyman lines is required for an accurate recombination history near the peak of the visibility function. On the other hand, stimulated recombinations and out-of equilibrium effects are important at late times and a multilevel calculation is required to correctly compute the low-redshift end of the ionization history. Another facet of the problem is the requirement of computational efficiency, as a large number of recombination histories must be evaluated in Markov chains when analyzing CMB data. In this thesis, an effective multilevel atom method is presented, that speeds up multilevel atom computations by more than 5 orders of magnitude. The impact of previously ignored radiative transfer effects is quantified, and explicitly shown to be negligible. Finally, the numerical implementation of a fast and highly accurate primordial recombination code partly written by the author is described. The second part of this thesis is devoted to one of the potential galactic foregrounds for CMB experiments: the rotational emission from small dust grains. The rotational state of dust grains is described, first classically, and assuming that grains are rotating about their axis of greatest inertia. This assumption is then lifted, and a quantum-mechanical calculation is presented for disk-like grains with a
Development of an Integrated Global Energy Model
International Nuclear Information System (INIS)
Krakowski, R.A.
1999-01-01
The primary objective of this research was to develop a forefront analysis tool for application to enhance understanding of long-term, global, nuclear-energy and nuclear-material futures. To this end, an existing economics-energy-environmental (E 3 ) model was adopted, modified, and elaborated to examine this problem in a multi-regional (13), long-term (approximately2,100) context. The E 3 model so developed was applied to create a Los Alamos presence in this E 3 area through ''niche analyses'' that provide input to the formulation of policies dealing with and shaping of nuclear-energy and nuclear-materials futures. Results from analyses using the E 3 model have been presented at a variety of national and international conferences and workshops. Through use of the E 3 model Los Alamos was afforded the opportunity to participate in a multi-national E 3 study team that is examining a range of global, long-term nuclear issues under the auspices of the IAEA during the 1998-99 period . Finally, the E 3 model developed under this LDRD project is being used as an important component in more recent Nuclear Material Management Systems (NMMS) project
Drought Persistence Errors in Global Climate Models
Moon, H.; Gudmundsson, L.; Seneviratne, S. I.
2018-04-01
The persistence of drought events largely determines the severity of socioeconomic and ecological impacts, but the capability of current global climate models (GCMs) to simulate such events is subject to large uncertainties. In this study, the representation of drought persistence in GCMs is assessed by comparing state-of-the-art GCM model simulations to observation-based data sets. For doing so, we consider dry-to-dry transition probabilities at monthly and annual scales as estimates for drought persistence, where a dry status is defined as negative precipitation anomaly. Though there is a substantial spread in the drought persistence bias, most of the simulations show systematic underestimation of drought persistence at global scale. Subsequently, we analyzed to which degree (i) inaccurate observations, (ii) differences among models, (iii) internal climate variability, and (iv) uncertainty of the employed statistical methods contribute to the spread in drought persistence errors using an analysis of variance approach. The results show that at monthly scale, model uncertainty and observational uncertainty dominate, while the contribution from internal variability is small in most cases. At annual scale, the spread of the drought persistence error is dominated by the statistical estimation error of drought persistence, indicating that the partitioning of the error is impaired by the limited number of considered time steps. These findings reveal systematic errors in the representation of drought persistence in current GCMs and suggest directions for further model improvement.
Antari, A. El; Zahir, H.; Hasnaoui, A.; Hachem, N.; Alrajhi, A.; Madani, M.; Bouziani, M. El
2018-04-01
Using the renormalization group approximation, specifically the Migdal-Kadanoff technique, we investigate the Blume-Capel model with mixed spins S = 1/2 and S = 5/2 on d-dimensional hypercubic lattice. The flow in the parameter space of the Hamiltonian and the thermodynamic functions are determined. The phase diagram of this model is plotted in the (anisotropy, temperature) plane for both cases d = 2 and d = 3 in which the system exhibits the first and second order phase transitions and critical end-points. The associated fixed points are drawn up in a table, and by linearizing the transformation at the vicinity of these points, we determine the critical exponents for d = 2 and d = 3. We have also presented a variation of the free energy derivative at the vicinity of the first and second order transitions. Finally, this work is completed by a discussion and comparison with other approximation.
International Nuclear Information System (INIS)
Castro-Alvaredo, Olalla A; Fring, Andreas
2009-01-01
We investigate a lattice version of the Yang-Lee model which is characterized by a non-Hermitian quantum spin chain Hamiltonian. We propose a new way to implement PT-symmetry on the lattice, which serves to guarantee the reality of the spectrum in certain regions of values of the coupling constants. In that region of unbroken PT-symmetry, we construct a Dyson map, a metric operator and find the Hermitian counterpart of the Hamiltonian for small values of the number of sites, both exactly and perturbatively. Besides the standard perturbation theory about the Hermitian part of the Hamiltonian, we also carry out an expansion in the second coupling constant of the model. Our constructions turn out to be unique with the sole assumption that the Dyson map is Hermitian. Finally, we analyse the magnetization of the chain in the z- and x-direction.
Progress in Global Multicompartmental Modelling of DDT
Stemmler, I.; Lammel, G.
2009-04-01
Dichlorophenyltrichloroethane, DDT, and its major metabolite dichlorophenyldichloroethylene, DDE, are long-lived in the environment (persistent) and circulate since the 1950s. They accumulate along food chains, cause detrimental effects in marine and terrestrial wild life, and pose a hazard for human health. DDT was widely used as an insecticide in the past and is still in use in a number of tropical countries to combat vector borne diseases like malaria and typhus. It is a multicompartmental substance with only a small mass fraction residing in air. A global multicompartment chemistry transport model (MPI-MCTM; Semeena et al., 2006) is used to study the environmental distribution and fate of dichlorodiphenyltrichloroethane (DDT). For the first time a horizontally and vertically resolved global model was used to perform a long-term simulation of DDT and DDE. The model is based on general circulation models for the ocean (MPIOM; Marsland et al., 2003) and atmosphere (ECHAM5). In addition, an oceanic biogeochemistry model (HAMOCC5.1; Maier-Reimer et al., 2005 ) and a microphysical aerosol model (HAM; Stier et al., 2005 ) are included. Multicompartmental substances are cycling in atmosphere (3 phases), ocean (3 phases), top soil (3 phases), and vegetation surfaces. The model was run for 40 years forced with historical agricultural application data of 1950-1990. The model results show that the global environmental contamination started to decrease in air, soil and vegetation after the applications peaked in 1965-70. In some regions, however, the DDT mass had not yet reached a maximum in 1990 and was still accumulating mass until the end of the simulation. Modelled DDT and DDE concentrations in atmosphere, ocean and soil are evaluated by comparison with observational data. The evaluation of the model results indicate that degradation of DDE in air was underestimated. Also for DDT, the discrepancies between model results and observations are related to uncertainties of
A satellite-based global landslide model
Directory of Open Access Journals (Sweden)
A. Farahmand
2013-05-01
Full Text Available Landslides are devastating phenomena that cause huge damage around the world. This paper presents a quasi-global landslide model derived using satellite precipitation data, land-use land cover maps, and 250 m topography information. This suggested landslide model is based on the Support Vector Machines (SVM, a machine learning algorithm. The National Aeronautics and Space Administration (NASA Goddard Space Flight Center (GSFC landslide inventory data is used as observations and reference data. In all, 70% of the data are used for model development and training, whereas 30% are used for validation and verification. The results of 100 random subsamples of available landslide observations revealed that the suggested landslide model can predict historical landslides reliably. The average error of 100 iterations of landslide prediction is estimated to be approximately 7%, while approximately 2% false landslide events are observed.
Modeling and simulation of spin-polarized transport at the kinetic and diffusive level
International Nuclear Information System (INIS)
Possanner, S.
2012-01-01
The aim of this thesis is to contribute to the understanding of spin-induced phenomena in electron motion. These phenomena arise when electrons move through a (partially) magnetic environment, in such a way that its magnetic moment (spin) may interact with the surroundings. The pure quantum nature of the spin requires transport models that deal with effects like quantum coherence, entanglement (correlation) and quantum dissipation. On the meso- and macroscopic level it is not yet clear under which circumstances these quantum effects may transpire. The purpose of this work is, on the one hand, to derive novel spin transport models from basic principles and, on the other hand, to develop numerical algorithms that allow for a solution of these new and other existing model equations. The thesis consists of four parts. The first part comprises an overview of fundamental spin-related concepts in electronic transport such as the giant-magneto-resistance (GMR) effect, the spin-transfer torque in metallic magnetic multilayers and the matrix-character of transport equations that take spin-coherent electron states into account. In particular, we consider the diffusive Zhang-Levy-Fert (ZLF) model, an exchange-torque model that consists of the Landau-Lifshitz equation and a heuristic matrix spin-diffusion equation. A finite difference scheme based on Strang operator splitting is developed that enables a numerical, self-consistent solution of this non-linear system within multilayer structures. Finally, the model is tested by comparison of numerical results to recent experimental data. In part two we propose a matrix-Boltzmann equation that allows for the description of spin-coherent electron transport on a kinetic level. The novelty here is a linear collision operator in which the transition rates from momentum k to momentum k' are modeled by a 2x2 Hermitian matrix; hence the mean-free paths of spin-up and spin-down electrons are represented by the eigenvalues of this
A hydroclimatic model of global fire patterns
Boer, Matthias
2015-04-01
Satellite-based earth observation is providing an increasingly accurate picture of global fire patterns. The highest fire activity is observed in seasonally dry (sub-)tropical environments of South America, Africa and Australia, but fires occur with varying frequency, intensity and seasonality in almost all biomes on Earth. The particular combination of these fire characteristics, or fire regime, is known to emerge from the combined influences of climate, vegetation, terrain and land use, but has so far proven difficult to reproduce by global models. Uncertainty about the biophysical drivers and constraints that underlie current global fire patterns is propagated in model predictions of how ecosystems, fire regimes and biogeochemical cycles may respond to projected future climates. Here, I present a hydroclimatic model of global fire patterns that predicts the mean annual burned area fraction (F) of 0.25° x 0.25° grid cells as a function of the climatic water balance. Following Bradstock's four-switch model, long-term fire activity levels were assumed to be controlled by fuel productivity rates and the likelihood that the extant fuel is dry enough to burn. The frequency of ignitions and favourable fire weather were assumed to be non-limiting at long time scales. Fundamentally, fuel productivity and fuel dryness are a function of the local water and energy budgets available for the production and desiccation of plant biomass. The climatic water balance summarizes the simultaneous availability of biologically usable energy and water at a site, and may therefore be expected to explain a significant proportion of global variation in F. To capture the effect of the climatic water balance on fire activity I focused on the upper quantiles of F, i.e. the maximum level of fire activity for a given climatic water balance. Analysing GFED4 data for annual burned area together with gridded climate data, I found that nearly 80% of the global variation in the 0.99 quantile of F
On coupling global biome models with climate models
International Nuclear Information System (INIS)
Claussen, M.
1994-01-01
The BIOME model of Prentice et al. (1992), which predicts global vegetation patterns in equilibrium with climate, is coupled with the ECHAM climate model of the Max-Planck-Institut fuer Meteorologie, Hamburg. It is found that incorporation of the BIOME model into ECHAM, regardless at which frequency, does not enhance the simulated climate variability, expressed in terms of differences between global vegetation patterns. Strongest changes are seen only between the initial biome distribution and the biome distribution computed after the first simulation period, provided that the climate-biome model is started from a biome distribution that resembles the present-day distribution. After the first simulation period, there is no significant shrinking, expanding, or shifting of biomes. Likewise, no trend is seen in global averages of land-surface parameters and climate variables. (orig.)
International Nuclear Information System (INIS)
Battistin, C; Roudi, Y; Hertz, J; Tyrcha, J
2015-01-01
We propose a new algorithm for inferring the state of hidden spins and reconstructing the connections in a synchronous kinetic Ising model, given the observed history. Focusing on the case in which the hidden spins are conditionally independent of each other given the state of observable spins, we show that calculating the likelihood of the data can be simplified by introducing a set of replicated auxiliary spins. Belief propagation (BP) and susceptibility propagation (SusP) can then be used to infer the states of hidden variables and to learn the couplings. We study the convergence and performance of this algorithm for networks with both Gaussian-distributed and binary bonds. We also study how the algorithm behaves as the fraction of hidden nodes and the amount of data are changed, showing that it outperforms the Thouless–Anderson–Palmer (TAP) equations for reconstructing the connections. (paper)
Tree-Based Global Model Tests for Polytomous Rasch Models
Komboz, Basil; Strobl, Carolin; Zeileis, Achim
2018-01-01
Psychometric measurement models are only valid if measurement invariance holds between test takers of different groups. Global model tests, such as the well-established likelihood ratio (LR) test, are sensitive to violations of measurement invariance, such as differential item functioning and differential step functioning. However, these…
Global and local level density models
International Nuclear Information System (INIS)
Koning, A.J.; Hilaire, S.; Goriely, S.
2008-01-01
Four different level density models, three phenomenological and one microscopic, are consistently parameterized using the same set of experimental observables. For each of the phenomenological models, the Constant Temperature Model, the Back-shifted Fermi gas Model and the Generalized Superfluid Model, a version without and with explicit collective enhancement is considered. Moreover, a recently published microscopic combinatorial model is compared with the phenomenological approaches and with the same set of experimental data. For each nuclide for which sufficient experimental data exists, a local level density parameterization is constructed for each model. Next, these local models have helped to construct global level density prescriptions, to be used for cases for which no experimental data exists. Altogether, this yields a collection of level density formulae and parameters that can be used with confidence in nuclear model calculations. To demonstrate this, a large-scale validation with experimental discrete level schemes and experimental cross sections and neutron emission spectra for various different reaction channels has been performed
Improved Analysis of GW150914 Using a Fully Spin-Precessing Waveform Model
Directory of Open Access Journals (Sweden)
2016-10-01
Full Text Available This paper presents updated estimates of source parameters for GW150914, a binary black-hole coalescence event detected by the Laser Interferometer Gravitational-wave Observatory (LIGO in 2015 [Abbott et al. Phys. Rev. Lett. 116, 061102 (2016.]. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016.] presented parameter estimation of the source using a 13-dimensional, phenomenological precessing-spin model (precessing IMRPhenom and an 11-dimensional nonprecessing effective-one-body (EOB model calibrated to numerical-relativity simulations, which forces spin alignment (nonprecessing EOBNR. Here, we present new results that include a 15-dimensional precessing-spin waveform model (precessing EOBNR developed within the EOB formalism. We find good agreement with the parameters estimated previously [Abbott et al. Phys. Rev. Lett. 116, 241102 (2016.], and we quote updated component masses of 35_{-3}^{+5} M_{⊙} and 30_{-4}^{+3} M_{⊙} (where errors correspond to 90% symmetric credible intervals. We also present slightly tighter constraints on the dimensionless spin magnitudes of the two black holes, with a primary spin estimate <0.65 and a secondary spin estimate <0.75 at 90% probability. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016.] estimated the systematic parameter-extraction errors due to waveform-model uncertainty by combining the posterior probability densities of precessing IMRPhenom and nonprecessing EOBNR. Here, we find that the two precessing-spin models are in closer agreement, suggesting that these systematic errors are smaller than previously quoted.
A Global Model of Meteoric Sodium
Marsh, Daniel R.; Janches, Diego; Feng, Wuhu; Plane, John M. C.
2013-01-01
A global model of sodium in the mesosphere and lower thermosphere has been developed within the framework of the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model (WACCM). The standard fully interactive WACCM chemistry module has been augmented with a chemistry scheme that includes nine neutral and ionized sodium species. Meteoric ablation provides the source of sodium in the model and is represented as a combination of a meteoroid input function (MIF) and a parameterized ablation model. The MIF provides the seasonally and latitudinally varying meteoric flux which is modeled taking into consideration the astronomical origins of sporadic meteors and considers variations in particle entry angle, velocity, mass, and the differential ablation of the chemical constituents. WACCM simulations show large variations in the sodium constituents over time scales from days to months. Seasonality of sodium constituents is strongly affected by variations in the MIF and transport via the mean meridional wind. In particular, the summer to winter hemisphere flow leads to the highest sodium species concentrations and loss rates occurring over the winter pole. In the Northern Hemisphere, this winter maximum can be dramatically affected by stratospheric sudden warmings. Simulations of the January 2009 major warming event show that it caused a short-term decrease in the sodium column over the polar cap that was followed by a factor of 3 increase in the following weeks. Overall, the modeled distribution of atomic sodium in WACCM agrees well with both ground-based and satellite observations. Given the strong sensitivity of the sodium layer to dynamical motions, reproducing its variability provides a stringent test of global models and should help to constrain key atmospheric variables in this poorly sampled region of the atmosphere.
Global adjoint tomography: first-generation model
Bozdağ, Ebru
2016-09-23
We present the first-generation global tomographic model constructed based on adjoint tomography, an iterative full-waveform inversion technique. Synthetic seismograms were calculated using GPU-accelerated spectral-element simulations of global seismic wave propagation, accommodating effects due to 3-D anelastic crust & mantle structure, topography & bathymetry, the ocean load, ellipticity, rotation, and self-gravitation. Fréchet derivatives were calculated in 3-D anelastic models based on an adjoint-state method. The simulations were performed on the Cray XK7 named \\'Titan\\', a computer with 18 688 GPU accelerators housed at Oak Ridge National Laboratory. The transversely isotropic global model is the result of 15 tomographic iterations, which systematically reduced differences between observed and simulated three-component seismograms. Our starting model combined 3-D mantle model S362ANI with 3-D crustal model Crust2.0. We simultaneously inverted for structure in the crust and mantle, thereby eliminating the need for widely used \\'crustal corrections\\'. We used data from 253 earthquakes in the magnitude range 5.8 ≤ M ≤ 7.0. We started inversions by combining ~30 s body-wave data with ~60 s surface-wave data. The shortest period of the surface waves was gradually decreased, and in the last three iterations we combined ~17 s body waves with ~45 s surface waves. We started using 180 min long seismograms after the 12th iteration and assimilated minor- and major-arc body and surface waves. The 15th iteration model features enhancements of well-known slabs, an enhanced image of the Samoa/Tahiti plume, as well as various other plumes and hotspots, such as Caroline, Galapagos, Yellowstone and Erebus. Furthermore, we see clear improvements in slab resolution along the Hellenic and Japan Arcs, as well as subduction along the East of Scotia Plate, which does not exist in the starting model. Point-spread function tests demonstrate that we are approaching the
The Kadanoff lower-bound variational renormalization group applied to an SU(2) lattice spin model
International Nuclear Information System (INIS)
Thorleifsson, G.; Damgaard, P.H.
1990-07-01
We apply the variational lower-bound Renormalization Group transformation of Kadanoff to an SU(2) lattice spin model in 2 and 3 dimensions. Even in the one-hypercube framework of this renormalization group transformation the present model is characterised by having an infinite basis of fundamental operators. We investigate whether the lower-bound variational renormalization group transformation yields results stable under truncations of this operator basis. Our results show that for this particular spin model this is not the case. (orig.)
Challenges in Modeling of the Global Atmosphere
Janjic, Zavisa; Djurdjevic, Vladimir; Vasic, Ratko; Black, Tom
2015-04-01
") with significant amplitudes can develop. Due to their large scales, that are comparable to the scales of the dominant Rossby waves, such fictitious solutions are hard to identify and remove. Another new challenge on the global scale is that the limit of validity of the hydrostatic approximation is rapidly being approached. Having in mind the sensitivity of extended deterministic forecasts to small disturbances, we may need global non-hydrostatic models sooner than we think. The unified Non-hydrostatic Multi-scale Model (NMMB) that is being developed at the National Centers for Environmental Prediction (NCEP) as a part of the new NOAA Environmental Modeling System (NEMS) will be discussed as an example. The non-hydrostatic dynamics were designed in such a way as to avoid over-specification. The global version is run on the latitude-longitude grid, and the polar filter selectively slows down the waves that would otherwise be unstable. The model formulation has been successfully tested on various scales. A global forecasting system based on the NMMB has been run in order to test and tune the model. The skill of the medium range forecasts produced by the NMMB is comparable to that of other major medium range models. The computational efficiency of the global NMMB on parallel computers is good.
Theoretical models of the spin-dependent charge-carrier dynamics in metals and semiconductors
International Nuclear Information System (INIS)
Krauss, Michael
2010-01-01
-spots'', which are an important characteristic of the spin-orbit interaction in the hole system. Based on the results for holes in GaAs, we have introduced a model for the laser-induced ultrafast demagnetization in the ferromagnetic transition metals cobalt and nickel. Our approach is based on an Elliott-Yafet-type mechanism, i.e., it describes spin-dependent dynamics due to (mainly electron-electron) scattering transitions between states including the spin-orbit interaction. By incorporating details of the optical excitation and scattering mechanisms as well as a sufficiently realistic single-particle band structure we obtain a good agreement with experimental results for the magnitude and time scale of the demagnetization in cobalt and nickel. The last part of this thesis is concerned with an attempt to include correlations of a magnetic type and to go beyond the scattering dynamics in single-particle band structures. We investigate model systems with parameters typical of ferromagnetic semiconductors. We examine correlated spin dynamics in a one-dimensional Kondo-lattice system, and explore the ground state properties by computing the relevant two-particle correlation functions starting from an uncorrelated initial state. (orig.)
Negativity as the Entanglement Measure to Probe the Kondo Regime in the Spin-Chain Kondo Model
Bayat, Abolfazl; Sodano, Pasquale; Bose, Sougato
2009-01-01
We study the entanglement of an impurity at one end of a spin chain with a block of spins using negativity as a true measure of entanglement to characterize the unique features of the gapless Kondo regime in the spin chain Kondo model. For this spin chain in the Kondo regime we determine- with a true entanglement measure- the spatial extent of the Kondo screening cloud, we propose an ansatz for its ground state and demonstrate that the impurity spin is indeed maximally entangled with the clou...
Block spins and chirality in Heisenberg model on Kagome and triangular lattices
International Nuclear Information System (INIS)
Subrahmanyam, V.
1994-01-01
The spin-1/2 Heisenberg model (HM) is investigated using a block-spin renormalization approach on Kagome and triangular lattices. In both cases, after coarse graining the triangles on original lattice and truncation of the Hilbert space to the triangular ground state subspace, HM reduces to an effective model on a triangular lattice in terms of the triangular-block degrees of freedom viz. the spin and the chirality quantum numbers. The chirality part of the effective Hamiltonian captures the essential difference between the two lattices. It is seen that simple eigenstates can be constructed for the effective model whose energies serve as upper bounds on the exact ground state energy of HM, and chiral ordered variational states have high energies compared to the other variational states. (author). 12 refs, 2 figs
On the TAP Free Energy in the Mixed p-Spin Models
Chen, Wei-Kuo; Panchenko, Dmitry
2018-05-01
Thouless et al. (Phys Mag 35(3):593-601, 1977), derived a representation for the free energy of the Sherrington-Kirkpatrick model, called the TAP free energy, written as the difference of the energy and entropy on the extended configuration space of local magnetizations with an Onsager correction term. In the setting of mixed p-spin models with Ising spins, we prove that the free energy can indeed be written as the supremum of the TAP free energy over the space of local magnetizations whose Edwards-Anderson order parameter (self-overlap) is to the right of the support of the Parisi measure. Furthermore, for generic mixed p-spin models, we prove that the free energy is equal to the TAP free energy evaluated on the local magnetization of any pure state.
Higher order spin-dependent terms in D0-brane scattering from the matrix model
International Nuclear Information System (INIS)
McArthur, I.N.
1998-01-01
The potential describing long-range interactions between D0-branes contains spin-dependent terms. In the matrix model, these should be reproduced by the one-loop effective action computed in the presence of a non-trivial fermionic background ψ. The v 3 ψ 2 /r 8 term in the effective action has been computed by Kraus and shown to correspond to a spin-orbit interaction between D0-branes, and the ψ 8 /r 11 term in the static potential has been obtained by Barrio et al. In this paper, the v 2 ψ 4 /r 9 term is computing in the matrix model and compared with the corresponding results of Morales et al. obtained using string theoretic methods. The technique employed is adapted to the underlying supersymmetry of the matrix model, and should be useful in the calculation of spin-dependent effects in more general Dp-brane scatterings. (orig.)
Path integral for spinning particle in the plane wave field: Global and local projections
International Nuclear Information System (INIS)
Boudiaf, N.; Boudjedaa, T.; Chetouani, L.
2001-01-01
The Green function related to the problem of a Dirac particle interacting with a plane wave is calculated via the path integral formalism proposed recently by Alexandrou et al. according to the two so-called global and local projections. With the help of the incorporation of two simple identities, it is shown that the contribution to the calculation of the integrals comes essentially from classical solutions projected along the direction of wave propagation. (orig.)
Quasi-realistic distribution of interaction fields leading to a variant of Ising spin glass model
International Nuclear Information System (INIS)
Tanasa, Radu; Enachescu, Cristian; Stancu, Alexandru; Linares, Jorge; Varret, Francois
2004-01-01
The distribution of interaction fields of an Ising-like system, obtained by Monte Carlo entropic sampling is used for modeling the hysteretic behavior of patterned media made of magnetic particles with a common anisotropy axis; a variant of the canonical Edwards-Anderson Ising spin glass model is introduced
Technical Note: Reducing the spin-up time of integrated surface water–groundwater models
Ajami, H.; Evans, J. P.; McCabe, Matthew; Stisen, S.
2014-01-01
in model initialization is to run the model recursively using either a single year or multiple years of forcing data until the system equilibrates with respect to state and diagnostic variables. However, such "spin-up" approaches often require many years
Fermionic Hubbard model with Rashba or Dresselhaus spin-orbit coupling
Sun, Fadi; Ye, Jinwu; Liu, Wu-Ming
2017-06-01
In this work, we investigate the possible dramatic effects of Rashba or Dresselhaus spin-orbit coupling (SOC) on the fermionic Hubbard model in a two-dimensional square lattice. In the strong coupling limit, it leads to the rotated antiferromagnetic Heisenberg model which is a new class of quantum spin model. For a special equivalent class, we identify a new spin-orbital entangled commensurate ground (Y-y) state subject to strong quantum fluctuations at T = 0. We evaluate the quantum fluctuations by the spin wave expansion up to order 1/{S}2. In some SOC parameter regimes, the Y-y state supports a massive relativistic incommensurate magnon (C-IC) with its two gap minima positions continuously tuned by the SOC parameters. The C-IC magnons dominate all the low temperature thermodynamic quantities and also lead to the separation of the peak positions between the longitudinal and the transverse spin structure factors. In the weak coupling limit, any weak repulsive interaction also leads to a weak Y-y state. There is only a crossover from the weak to the strong coupling. High temperature expansions of the specific heats in both weak and strong coupling are presented. The dramatic roles to be played by these C-IC magnons at generic SOC parameters or under various external probes are hinted at. Experimental applications to both layered noncentrosymmetric materials and cold atoms are discussed.
Effects of doping on spin correlations in the periodic Anderson model
International Nuclear Information System (INIS)
Bonca, J.; Gubernatis, J.E.
1998-01-01
We studied the effects of hole doping on spin correlations in the two-dimensional periodic Anderson model, mainly at the full and three-quarters-full lower bands cases. In the full lower band case, strong antiferromagnetic correlations develop when the on-site repulsive interaction strength U becomes comparable to the quasiparticle bandwidth. In the three-quarters full case, a kind of spin correlation develops that is consistent with the resonance between a (π,0) and a (0,π) spin-density wave. In this state the spins on different sublattices appear uncorrelated. Hole doping away from the completely full case rapidly destroys the long-range antiferromagnetic correlations, in a manner reminiscent of the destruction of antiferromagnetism in the Hubbard model. In contrast to the Hubbard model, the doping does not shift the peak in the magnetic structure factor from the (π,π) position. At dopings intermediate to the full and three-quarters full cases, only weak spin correlations exist. copyright 1998 The American Physical Society
Global plastic models for computerized structural analysis
International Nuclear Information System (INIS)
Roche, R.L.; Hoffmann, A.
1977-01-01
In many types of structures, it is possible to use generalized stresses (like membrane forces, bending moment, torsion moment...) to define a yield surface for a part of the structure. Analysis can be achieved by using the HILL's principle and a hardening rule. The whole formulation is said 'Global Plastic Model'. Two different global models are used in the CEASEMT system for structural analysis, one for shell analysis and the other for piping analysis (in plastic or creep field). In shell analysis the generalized stresses chosen are the membrane forces and bending (including torsion) moments. There is only one yield condition for a normal to the middle surface and no integration along the thickness is required. In piping analysis, the choice of generalized stresses is bending moments, torsional moment, hoop stress and tension stress. There is only a set of stresses for a cross section and no integration over the cross section area is needed. Connected strains are axis curvature, torsion, uniform strains. The definition of the yield surface is the most important item. A practical way is to use a diagonal quadratic function of the stress components. But the coefficients are depending of the shape of the pipe element, especially for curved segments. Indications will be given on the yield functions used. Some examples of applications in structural analysis are added to the text
Modeling global scene factors in attention
Torralba, Antonio
2003-07-01
Models of visual attention have focused predominantly on bottom-up approaches that ignored structured contextual and scene information. I propose a model of contextual cueing for attention guidance based on the global scene configuration. It is shown that the statistics of low-level features across the whole image can be used to prime the presence or absence of objects in the scene and to predict their location, scale, and appearance before exploring the image. In this scheme, visual context information can become available early in the visual processing chain, which allows modulation of the saliency of image regions and provides an efficient shortcut for object detection and recognition. 2003 Optical Society of America
Global embedding of fibre inflation models
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [Dipartimento di Fisica e Astronomia, Università di Bologna,via Irnerio 46, 40126 Bologna (Italy); INFN - Sezione di Bologna,viale Berti Pichat 6/2, 40127 Bologna (Italy); Abdus Salam ICTP,Strada Costiera 11, Trieste 34151 (Italy); Muia, Francesco [Rudolf Peierls Centre for Theoretical Physics, University of Oxford,1 Keble Rd., Oxford OX1 3NP (United Kingdom); Shukla, Pramod [Abdus Salam ICTP,Strada Costiera 11, Trieste 34151 (Italy)
2016-11-30
We present concrete embeddings of fibre inflation models in globally consistent type IIB Calabi-Yau orientifolds with closed string moduli stabilisation. After performing a systematic search through the existing list of toric Calabi-Yau manifolds, we find several examples that reproduce the minimal setup to embed fibre inflation models. This involves Calabi-Yau manifolds with h{sup 1,1}=3 which are K3 fibrations over a ℙ{sup 1} base with an additional shrinkable rigid divisor. We then provide different consistent choices of the underlying brane set-up which generate a non-perturbative superpotential suitable for moduli stabilisation and string loop corrections with the correct form to drive inflation. For each Calabi-Yau orientifold setting, we also compute the effect of higher derivative contributions and study their influence on the inflationary dynamics.
A Global Atmospheric Model of Meteoric Iron
Feng, Wuhu; Marsh, Daniel R.; Chipperfield, Martyn P.; Janches, Diego; Hoffner, Josef; Yi, Fan; Plane, John M. C.
2013-01-01
The first global model of meteoric iron in the atmosphere (WACCM-Fe) has been developed by combining three components: the Whole Atmosphere Community Climate Model (WACCM), a description of the neutral and ion-molecule chemistry of iron in the mesosphere and lower thermosphere (MLT), and a treatment of the injection of meteoric constituents into the atmosphere. The iron chemistry treats seven neutral and four ionized iron containing species with 30 neutral and ion-molecule reactions. The meteoric input function (MIF), which describes the injection of Fe as a function of height, latitude, and day, is precalculated from an astronomical model coupled to a chemical meteoric ablation model (CABMOD). This newly developed WACCM-Fe model has been evaluated against a number of available ground-based lidar observations and performs well in simulating the mesospheric atomic Fe layer. The model reproduces the strong positive correlation of temperature and Fe density around the Fe layer peak and the large anticorrelation around 100 km. The diurnal tide has a significant effect in the middle of the layer, and the model also captures well the observed seasonal variations. However, the model overestimates the peak Fe+ concentration compared with the limited rocket-borne mass spectrometer data available, although good agreement on the ion layer underside can be obtained by adjusting the rate coefficients for dissociative recombination of Fe-molecular ions with electrons. Sensitivity experiments with the same chemistry in a 1-D model are used to highlight significant remaining uncertainties in reaction rate coefficients, and to explore the dependence of the total Fe abundance on the MIF and rate of vertical transport.
The Software Architecture of Global Climate Models
Alexander, K. A.; Easterbrook, S. M.
2011-12-01
It has become common to compare and contrast the output of multiple global climate models (GCMs), such as in the Climate Model Intercomparison Project Phase 5 (CMIP5). However, intercomparisons of the software architecture of GCMs are almost nonexistent. In this qualitative study of seven GCMs from Canada, the United States, and Europe, we attempt to fill this gap in research. We describe the various representations of the climate system as computer programs, and account for architectural differences between models. Most GCMs now practice component-based software engineering, where Earth system components (such as the atmosphere or land surface) are present as highly encapsulated sub-models. This architecture facilitates a mix-and-match approach to climate modelling that allows for convenient sharing of model components between institutions, but it also leads to difficulty when choosing where to draw the lines between systems that are not encapsulated in the real world, such as sea ice. We also examine different styles of couplers in GCMs, which manage interaction and data flow between components. Finally, we pay particular attention to the varying levels of complexity in GCMs, both between and within models. Many GCMs have some components that are significantly more complex than others, a phenomenon which can be explained by the respective institution's research goals as well as the origin of the model components. In conclusion, although some features of software architecture have been adopted by every GCM we examined, other features show a wide range of different design choices and strategies. These architectural differences may provide new insights into variability and spread between models.
Sensitivities in global scale modeling of isoprene
Directory of Open Access Journals (Sweden)
R. von Kuhlmann
2004-01-01
Full Text Available A sensitivity study of the treatment of isoprene and related parameters in 3D atmospheric models was conducted using the global model of tropospheric chemistry MATCH-MPIC. A total of twelve sensitivity scenarios which can be grouped into four thematic categories were performed. These four categories consist of simulations with different chemical mechanisms, different assumptions concerning the deposition characteristics of intermediate products, assumptions concerning the nitrates from the oxidation of isoprene and variations of the source strengths. The largest differences in ozone compared to the reference simulation occured when a different isoprene oxidation scheme was used (up to 30-60% or about 10 nmol/mol. The largest differences in the abundance of peroxyacetylnitrate (PAN were found when the isoprene emission strength was reduced by 50% and in tests with increased or decreased efficiency of the deposition of intermediates. The deposition assumptions were also found to have a significant effect on the upper tropospheric HOx production. Different implicit assumptions about the loss of intermediate products were identified as a major reason for the deviations among the tested isoprene oxidation schemes. The total tropospheric burden of O3 calculated in the sensitivity runs is increased compared to the background methane chemistry by 26±9 Tg( O3 from 273 to an average from the sensitivity runs of 299 Tg(O3. % revised Thus, there is a spread of ± 35% of the overall effect of isoprene in the model among the tested scenarios. This range of uncertainty and the much larger local deviations found in the test runs suggest that the treatment of isoprene in global models can only be seen as a first order estimate at present, and points towards specific processes in need of focused future work.
On the zeros of the Husimi functions of the spin boson model
International Nuclear Information System (INIS)
Cibils, M.B.; Cuche, Y.; Leboeuf, P.; Wreszinski, W.F.
1992-03-01
The distribution of zeros of the Husimi functions for the spin-boson model is studied, following an approach introduced by Leboeuf and Voros. The interest lies in the model's double feature of possessing both a classical integrable to chaotic transition and an unbounded four-dimensional phase space. The latter gives rise to several new questions regarding the Husimi zeros which are discussed and partially answered. Some significant results occur in spite of the fact that the case of spin one-half is treated. (authors) 20 refs., 4 figs
Evaluation of global solar radiation models for Shanghai, China
International Nuclear Information System (INIS)
Yao, Wanxiang; Li, Zhengrong; Wang, Yuyan; Jiang, Fujian; Hu, Lingzhou
2014-01-01
Highlights: • 108 existing models are compared and analyzed by 42 years meteorological data. • Fitting models based on measured data are established according to 42 years data. • All models are compared by recently 10 years meteorological data. • The results show that polynomial models are the most accurate models. - Abstract: In this paper, 89 existing monthly average daily global solar radiation models and 19 existing daily global solar radiation models are compared and analyzed by 42 years meteorological data. The results show that for existing monthly average daily global solar radiation models, linear models and polynomial models have been able to estimate global solar radiation accurately, and complex equation types cannot obviously improve the precision. Considering direct parameters such as latitude, altitude, solar altitude and sunshine duration can help improve the accuracy of the models, but indirect parameters cannot. For existing daily global solar radiation models, multi-parameter models are more accurate than single-parameter models, polynomial models are more accurate than linear models. Then measured data fitting monthly average daily global solar radiation models (MADGSR models) and daily global solar radiation models (DGSR models) are established according to 42 years meteorological data. Finally, existing models and fitting models based on measured data are comparative analysis by recent 10 years meteorological data, and the results show that polynomial models (MADGSR model 2, DGSR model 2 and Maduekwe model 2) are the most accurate models
Bovier, Anton
2007-01-01
Spin glass theory is going through a stunning period of progress while finding exciting new applications in areas beyond theoretical physics, in particular in combinatorics and computer science. This collection of state-of-the-art review papers written by leading experts in the field covers the topic from a wide variety of angles. The topics covered are mean field spin glasses, including a pedagogical account of Talagrand's proof of the Parisi solution, short range spin glasses, emphasizing the open problem of the relevance of the mean-field theory for lattice models, and the dynamics of spin glasses, in particular the problem of ageing in mean field models. The book will serve as a concise introduction to the state of the art of spin glass theory, usefull to both graduate students and young researchers, as well as to anyone curious to know what is going on in this exciting area of mathematical physics.
Spin decoherence in electron storage rings. More from a simple model
Energy Technology Data Exchange (ETDEWEB)
Barber, D.P. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Heinemann, K. [The Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Mathematics and Statistics
2015-06-15
This is an addendum to the paper ''Some models of spin coherence and decoherence in storage rings'' by one of the authors (K. Heinemann, DESY Report 97-166 (1997)), in which spin diffusion in simple electron storage rings is studied. In particular, we illustrate in a compact way, namely that the exact formalism of this article delivers a rate of depolarisation which can differ from that obtained by the conventional treatments of spin diffusion which rely on the use of the derivative ∂n/∂η. As a vehicle we consider a ring with a Siberian Snake and electron polarisation in the plane of the ring. For this simple setup with its one-dimensional spin motion, we avoid having to deal directly with the Bloch equation for the polarisation density. Our treatment, which is deliberately pedagogical, shows that the use of ∂n/∂η provides a very good approximation to the rate of spin depolarisation in the model considered. But it then shows that the exact rate of depolarisation can be obtained by replacing ∂n/∂η by another derivative, while giving a heuristic justification for the new derivative.
A global digital elevation model - GTOP030
1999-01-01
GTOP030, the U.S. Geological Survey's (USGS) digital elevation model (DEM) of the Earth, provides the flrst global coverage of moderate resolution elevation data. The original GTOP30 data set, which was developed over a 3-year period through a collaborative effort led by the USGS, was completed in 1996 at the USGS EROS Data Center in Sioux Falls, South Dakota. The collaboration involved contributions of staffing, funding, or source data from cooperators including the National Aeronautics and Space Administration (NASA), the United Nations Environment Programme Global Resource Information Database (UNEP/GRID), the U.S. Agency for International Development (USAID), the Instituto Nacional de Estadistica Geografia e Informatica (INEGI) of Mexico, the Geographical Survey Institute (GSI) of Japan, Manaaki Whenua Landcare Research of New Zealand, and the Scientific Committee on Antarctic Research (SCAR). In 1999, work was begun on an update to the GTOP030 data set. Additional data sources are being incorporated into GTOP030 with an enhanced and improved data set planned for release in 2000.
Use of wind data in global modelling
Pailleux, J.
1985-01-01
The European Centre for Medium Range Weather Forecasts (ECMWF) is producing operational global analyses every 6 hours and operational global forecasts every day from the 12Z analysis. How the wind data are used in the ECMWF golbal analysis is described. For each current wind observing system, its ability to provide initial conditions for the forecast model is discussed as well as its weaknesses. An assessment of the impact of each individual system on the quality of the analysis and the forecast is given each time it is possible. Sometimes the deficiencies which are pointed out are related not only to the observing system itself but also to the optimum interpolation (OI) analysis scheme; then some improvements are generally possible through ad hoc modifications of the analysis scheme and especially tunings of the structure functions. Examples are given. The future observing network over the North Atlantic is examined. Several countries, coordinated by WMO, are working to set up an 'Operational WWW System Evaluation' (OWSE), in order to evaluate the operational aspects of the deployment of new systems (ASDAR, ASAP). Most of the new systems are expected to be deployed before January 1987, and in order to make the best use of the available resources during the deployment phase, some network studies are carried out at the present time, by using simulated data for ASDAR and ASAP systems. They are summarized.
Thermodynamics of spin chains of Haldane–Shastry type and one-dimensional vertex models
International Nuclear Information System (INIS)
Enciso, Alberto; Finkel, Federico; González-López, Artemio
2012-01-01
We study the thermodynamic properties of spin chains of Haldane–Shastry type associated with the A N−1 root system in the presence of a uniform external magnetic field. To this end, we exactly compute the partition function of these models for an arbitrary finite number of spins. We then show that these chains are equivalent to a suitable inhomogeneous classical Ising model in a spatially dependent magnetic field, generalizing the results of Basu-Mallick et al. for the zero magnetic field case. Using the standard transfer matrix approach, we are able to compute in closed form the free energy per site in the thermodynamic limit. We perform a detailed analysis of the chains’ thermodynamics in a unified way, with special emphasis on the zero field and zero temperature limits. Finally, we provide a novel interpretation of the thermodynamic quantities of spin chains of Haldane–Shastry type as weighted averages of the analogous quantities over an ensemble of classical Ising models. - Highlights: ► Partition function of spin chains of Haldane–Shastry type in magnetic field. ► Equivalence to classical inhomogeneous Ising models. ► Free energy per site, other thermodynamic quantities in thermodynamic limit. ► Zero field, zero temperature limits. ► Thermodynamic equivalence with ensemble of classical Ising models.
Generalized spin-wave theory: Application to the bilinear-biquadratic model
Muniz, Rodrigo A.; Kato, Yasuyuki; Batista, Cristian D.
2014-08-01
We present a mathematical framework for the multi-boson approach that has been used several times for treating spin systems. We demonstrate that the multi-boson approach corresponds to a generalization of the traditional spin-wave theory from SU(2) to SU(N), where N is the number of states of the local degree of freedom. Low-energy excitations are waves of the local order parameter that fluctuates in the SU(N) space of unitary transformations of the local spin states, instead of the SU(2) space of local spin rotations. Since the generators of the SU(N) group can be represented as bilinear forms in N-flavored bosons, the low-energy modes of the generalized spin-wave theory (GSWT) are described with N-1 different bosons, which provide a more accurate description of low-energy excitations even for the usual ferromagnetic and antiferromagnetic phases. The generalization enables the treatment of quantum spin systems whose ground states exhibit multipolar ordering as well as the detection of instabilities of magnetically ordered states (dipolar ordering) towards higher multipolar orderings. We illustrate the advantages of the GSWT by applying it to a bilinear-biquadratic model of arbitrary spin S on hypercubic lattices, and then analyzing the spectrum of dipolar phases in order to find their instabilities. In contrast to the known results for S=1 when the biquadratic term in the Hamiltonian is negative, we find that there is no nematic phase between the ferromagnetic or antiferromagnetic orderings for S>1.
2-D model of global aerosol transport
Energy Technology Data Exchange (ETDEWEB)
Rehkopf, J; Newiger, M; Grassl, H
1984-01-01
The distribution of aerosol particles in the troposphere is described. Starting with long term mean seasonal flow and diffusivities as well as temperature, cloud distribution (six cloud classes), relative humidity and OH radical concentration, the steady state concentration of aerosol particles and SO/sub 2/ are calculated in a two-dimensional global (height and latitude) model. The following sources and sinks for particles are handled: direct emission, gas-to-particle conversion from SO/sub 2/, coagulation, rainout, washout, gravitational settling, and dry deposition. The sinks considered for sulphur emissions are dry deposition, washout, rainout, gasphase oxidation, and aqueous phase oxidation. Model tests with the water vapour cycle show a good agreement between measured and calculated zonal mean precipitation distribution. The steady state concentration distribution for natural emissions reached after 10 weeks model time, may be described by a mean exponent ..cap alpha.. = 3.2 near the surface assuming a modified Junge distribution and an increased value, ..cap alpha.. = 3.7, for the combined natural and man-made emission. The maximum ground level concentrations are 2000 and 10,000 particules cm/sup -3/ for natural and natural plus man-made emissions, respectively. The resulting distribution of sulphur dioxide agrees satisfactorily with measurements given by several authors. 37 references, 4 figures.
Integrated assessment models of global climate change
International Nuclear Information System (INIS)
Parson, E.A.; Fisher-Vanden, K.
1997-01-01
The authors review recent work in the integrated assessment modeling of global climate change. This field has grown rapidly since 1990. Integrated assessment models seek to combine knowledge from multiple disciplines in formal integrated representations; inform policy-making, structure knowledge, and prioritize key uncertainties; and advance knowledge of broad system linkages and feedbacks, particularly between socio-economic and bio-physical processes. They may combine simplified representations of the socio-economic determinants of greenhouse gas emissions, the atmosphere and oceans, impacts on human activities and ecosystems, and potential policies and responses. The authors summarize current projects, grouping them according to whether they emphasize the dynamics of emissions control and optimal policy-making, uncertainty, or spatial detail. They review the few significant insights that have been claimed from work to date and identify important challenges for integrated assessment modeling in its relationships to disciplinary knowledge and to broader assessment seeking to inform policy- and decision-making. 192 refs., 2 figs
Li, Rui
2018-02-01
The Kronig-Penney model, an exactly solvable one-dimensional model of crystal in solid physics, shows how the allowed and forbidden bands are formed in solids. In this paper, we study this model in the presence of both strong spin-orbit coupling and the Zeeman field. We analytically obtain four transcendental equations that represent an implicit relation between the energy and the Bloch wave vector. Solving these four transcendental equations, we obtain the spin-orbital bands exactly. In addition to the usual band gap opened at the boundary of the Brillouin zone, a much larger spin-orbital band gap is also opened at some special sites inside the Brillouin zone. The x component of the spin-polarization vector is an even function of the Bloch wave vector, while the z component of the spin-polarization vector is an odd function of the Bloch wave vector. At the band edges, the optical transition rates between adjacent bands are nonzero.
Caspers, W J
1989-01-01
This book is about spin systems as models for magnetic materials, especially antiferromagnetic lattices. Spin-systems are well-defined models, for which, in special cases, exact properties may be derived. These special cases are for the greater part, one- dimensional and restricted in their applicability, but they may give insight into general properties that also exist in higher dimension. This work pays special attention to qualitative differences between spin lattices of different dimensions. It also replaces the traditional picture of an (ordered) antiferromagnetic state of a Heisenberg sy
Critical properties of a ferroelectric superlattice described by a transverse spin-1/2 Ising model
International Nuclear Information System (INIS)
Tabyaoui, A; Saber, M; Baerner, K; Ainane, A
2007-01-01
The phase transition properties of a ferroelectric superlattice with two alternating layers A and B described by a transverse spin-1/2 Ising model have been investigated using the effective field theory within a probability distribution technique that accounts for the self spin correlation functions. The Curie temperature T c , polarization and susceptibility have been obtained. The effects of the transverse field and the ferroelectric and antiferroelectric interfacial coupling strength between two ferroelectric materials are discussed. They relate to the physical properties of antiferroelectric/ferroelectric superlattices
The ground-state phase diagrams of the spin-3/2 Ising model
International Nuclear Information System (INIS)
Canko, Osman; Keskin, Mustafa
2003-01-01
The ground-state spin configurations are obtained for the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic exchange interactions and a single-ion crystal field. The interactions are assumed to be only between nearest-neighbors. The calculated ground-state phase diagrams are presented on diatomic lattices, such as the square, honeycomb and sc lattices, and triangular lattice in the (Δ/z vertical bar J vertical bar ,K/ vertical bar J vertical bar) and (H/z vertical bar J vertical bar, K/ vertical bar J vertical bar) planes
A novel approach to modelling non-exponential spin glass relaxation
Energy Technology Data Exchange (ETDEWEB)
Pickup, R.M. [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom)]. E-mail: r.cywinski@leeds.ac.uk; Cywinski, R. [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Pappas, C. [Hahn-Meitner Institut, Glienicker Strasse 100, 14109 Berlin (Germany)
2007-07-15
A probabilistic cluster model, originally proposed by Weron to explain the universal power law of dielectric relaxation, is shown to account for the non-exponential relaxation in spin glasses above T {sub g}. Neutron spin echo spectra measured for the cluster glass compound Co{sub 55}Ga{sub 45} are well described by the Weron relaxation function, {phi}(t)={phi} {sub o}(1+k(t/{tau}) {sup {beta}}){sup -1/k}, with the interaction parameter k scaling linearly with the non-Curie-Weiss susceptibility.
Janssen, Hans-Karl; Stenull, Olaf
2004-02-01
We investigate corrections to scaling induced by irrelevant operators in randomly diluted systems near the percolation threshold. The specific systems that we consider are the random resistor network and a class of continuous spin systems, such as the x-y model. We focus on a family of least irrelevant operators and determine the corrections to scaling that originate from this family. Our field theoretic analysis carefully takes into account that irrelevant operators mix under renormalization. It turns out that long standing results on corrections to scaling are respectively incorrect (random resistor networks) or incomplete (continuous spin systems).
Critical behavior of the quantum spin- {1}/{2} anisotropic Heisenberg model
Sousa, J. Ricardo de
A two-step renormalization group approach - a decimation followed by an effective field renormalization group (EFRG) - is proposed in this work to study the critical behavior of the quantum spin- {1}/{2} anisotropic Heisenberg model. The new method is illustrated by employing approximations in which clusters with one, two and three spins are used. The values of the critical parameter and critical exponent, in two- and three-dimensional lattices, for the Ising and isotropic Heisenberg limits are calculated and compared with other renormalization group approaches and exact (or series) results.
Monte Carlo simulations of the Spin-2 Blume-Emery-Griffiths model
International Nuclear Information System (INIS)
Iwashita, Takashi; Uragami, Kakuko; Muraoka, Yoshinori; Kinoshita, Takehiro; Idogaki, Toshihiro
2010-01-01
The magnetic properties of the spin S = 2 Ising system with the bilinear exchange interaction J 1 S iz S jz , the biquadratic exchange interaction J 2 S iz 2 S jz 2 and the single-ion anisotropy DS iz 2 are discussed by making use of the Monte Carlo (MC) simulation for the magnetization z >, sub-lattice magnetizations z (A)> and z (B)>, the magnetic specific heat C M and spin structures. This Ising spin system of S = 2 with interactions J 1 and J 2 and with anisotropy D corresponds to the spin-2 Blume-Emery-Griffiths model. The phase diagram of this Ising spin system on a two-dimensional square lattice has been obtained for exchange parameter J 2 /J 1 and anisotropy parameter D/J 1 . The shapes of the temperature dependence of sublattice magnetizations z (A)> and z (B)> are related with abnormal behavior of temperature dependence of z > at low temperatures and affected significantly by the single-ion anisotropy D. The staggered quadrupolar (SQ) ordering turns out to be different largely between Ising systems with the single-ion anisotropy (D ≠ 0) and without the one (D 0).
Degli Esposti, M.; Giardinà, C.; Graffi, S.; Isola, S.
2001-01-01
We consider the zero-temperature dynamics for the infinite-range, non translation invariant one-dimensional spin model introduced by Marinari, Parisi and Ritort to generate glassy behaviour out of a deterministic interaction. It is argued that there can be a large number of metastable (i.e.,
Investigation of high spin structure of N ∼ 28 nuclei with PHF model
International Nuclear Information System (INIS)
Naik, Z.
2016-01-01
Nucleus in 50 mass shows verity of high spin phenomena. Some of them are K-Isomer, Band termination, States Beyond Band termination, Superdeformed Structure, Shape co-existence and many more. Some of these phenomena with Projected Hartree-Fock (PHF) model are addressed and the microscopic structure associate with them is discussed
Kosterlitz-Thouless transitions in simple spin-models with strongly varying vortex densities
Himbergen, J.E.J.M. van
1985-01-01
A generalized XY-model, consisting of a family of nearest neighbour potentials of varying shape, for classical planar spins on a two-dimensional square lattice is analysed by a combination of Migdal-Kadanoff real-space renormalization and Monte Carlo simulations on a sequence of finite lattices of
The spin predictions of the relativistic quark model for baryon decuplet production
Montvay, István
1973-01-01
Single-quark scattering contributions are considered in the case of ground-state decuplet baryon production. It is shown within the framework of an explicitly covariant approach that the spin consequences of the quark additivity assumption hold in the t-channel helicity frame independently of much of the details of the model. (12 refs).
Large Deviations for the Annealed Ising Model on Inhomogeneous Random Graphs: Spins and Degrees
Dommers, Sander; Giardinà, Cristian; Giberti, Claudio; Hofstad, Remco van der
2018-04-01
We prove a large deviations principle for the total spin and the number of edges under the annealed Ising measure on generalized random graphs. We also give detailed results on how the annealing over the Ising model changes the degrees of the vertices in the graph and show how it gives rise to interesting correlated random graphs.
Weyl and transverse diffeomorphism invariant spin-2 models in D = 2 + 1
International Nuclear Information System (INIS)
Dalmazi, Denis; Mendonca, E.L.; Santos, A.L.R. dos; Ghosh, Subir
2017-01-01
There are two covariant descriptions of massless spin-2 particles in D = 3 + 1 via a symmetric rank-2 tensor: the linearized Einstein-Hilbert (LEH) theory and the Weyl plus transverse diffeomorphism (WTDIFF) invariant model. From the LEH theory one can obtain the linearized new massive gravity (NMG) in D = 2 + 1 via Kaluza-Klein dimensional reduction followed by a dual master action. Here we show that a similar route takes us from the WTDIFF model to a linearized scalar-tensor NMG which belongs to a larger class of consistent spin-0 modifications of NMG. We also show that a traceless master action applied to a parity singlet furnishes two new spin-2 self-dual models. Moreover, we examine the singular replacement h_μ_ν → h_μ_ν - η_μ_νh/D and prove that it leads to consistent massive spin-2 models in D = 2 + 1. They include linearized versions of unimodular topologically massive gravity (TMG) and unimodular NMG. Although the free part of those unimodular theories are Weyl invariant, we do not expect any improvement in the renormalizability. Both the linearized K-term (in NMG) and the linearized gravitational Chern-Simons term (in TMG) are invariant under longitudinal reparametrizations δh_μ_ν = ∂_μ∂_νζ, which is not a symmetry of the WTDIFF Einstein-Hilbert term. Therefore, we still have one degree of freedom whose propagator behaves like 1/p"2 for large momentum. (orig.)
Weyl and transverse diffeomorphism invariant spin-2 models in D=2+1
Dalmazi, Denis; dos Santos, A. L. R.; Ghosh, Subir; Mendonça, E. L.
2017-09-01
There are two covariant descriptions of massless spin-2 particles in D=3+1 via a symmetric rank-2 tensor: the linearized Einstein-Hilbert (LEH) theory and the Weyl plus transverse diffeomorphism (WTDIFF) invariant model. From the LEH theory one can obtain the linearized new massive gravity (NMG) in D=2+1 via Kaluza-Klein dimensional reduction followed by a dual master action. Here we show that a similar route takes us from the WTDIFF model to a linearized scalar-tensor NMG which belongs to a larger class of consistent spin-0 modifications of NMG. We also show that a traceless master action applied to a parity singlet furnishes two new spin-2 self-dual models. Moreover, we examine the singular replacement h_{μ ν } → h_{μ ν } - η _{μ ν }h/D and prove that it leads to consistent massive spin-2 models in D=2+1. They include linearized versions of unimodular topologically massive gravity (TMG) and unimodular NMG. Although the free part of those unimodular theories are Weyl invariant, we do not expect any improvement in the renormalizability. Both the linearized K-term (in NMG) and the linearized gravitational Chern-Simons term (in TMG) are invariant under longitudinal reparametrizations δ h_{μ ν } = partial _{μ }partial _{ν }ζ , which is not a symmetry of the WTDIFF Einstein-Hilbert term. Therefore, we still have one degree of freedom whose propagator behaves like 1/p^2 for large momentum.
The dilute spin-one Ising model with both bilinear and biquadratic exchange interactions
International Nuclear Information System (INIS)
Saber, M.
1987-08-01
The influence of bond and site dilution on the two-dimensional spin-one Ising model on a honeycomb lattice is investigated. Temperature-concentration phase diagrams for fixed values of the ratio of bilinear and biquadratic exchange interactions are determined. (author). 7 refs, 3 figs
International Nuclear Information System (INIS)
Chen Yuan; Song Chuangchuang; Xiang Ying
2010-01-01
In this paper, we apply the two-time Green's function method, and provide a simple way to study the magnetic properties of one-dimensional spin-(S,s) Heisenberg ferromagnets. The magnetic susceptibility and correlation functions are obtained by using the Tyablikov decoupling approximation. Our results show that the magnetic susceptibility and correlation length are a monotonically decreasing function of temperature regardless of the mixed spins. It is found that in the case of S=s, our results of one-dimensional mixed-spin model is reduced to be those of the isotropic ferromagnetic Heisenberg chain in the whole temperature region. Our results for the susceptibility are in agreement with those obtained by other theoretical approaches. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Marginal deformations of 3d supersymmetric U(N) model and broken higher spin symmetry
Energy Technology Data Exchange (ETDEWEB)
Hikida, Yasuaki [Center for Gravitational Physics, Yukawa Institute for Theoretical Physics, Kyoto University,Kyoto 606-8502 (Japan); Wada, Taiki [Department of Physical Sciences, College of Science and Engineering, Ritsumeikan University,Shiga 525-8577 (Japan)
2017-03-08
We examine the marginal deformations of double-trace type in 3d supersymmetric U(N) model with N complex free bosons and fermions. We compute the anomalous dimensions of higher spin currents to the 1/N order but to all orders in the deformation parameters by mainly applying the conformal perturbation theory. The 3d field theory is supposed to be dual to 4d supersymmetric Vasiliev theory, and the marginal deformations are argued to correspond to modifying boundary conditions for bulk scalars and fermions. Thus the modification should break higher spin gauge symmetry and generate the masses of higher spin fields. We provide supports for the dual interpretation by relating bulk computation in terms of Witten diagrams to boundary one in conformal perturbation theory.
Marginal deformations of 3d supersymmetric U(N) model and broken higher spin symmetry
International Nuclear Information System (INIS)
Hikida, Yasuaki; Wada, Taiki
2017-01-01
We examine the marginal deformations of double-trace type in 3d supersymmetric U(N) model with N complex free bosons and fermions. We compute the anomalous dimensions of higher spin currents to the 1/N order but to all orders in the deformation parameters by mainly applying the conformal perturbation theory. The 3d field theory is supposed to be dual to 4d supersymmetric Vasiliev theory, and the marginal deformations are argued to correspond to modifying boundary conditions for bulk scalars and fermions. Thus the modification should break higher spin gauge symmetry and generate the masses of higher spin fields. We provide supports for the dual interpretation by relating bulk computation in terms of Witten diagrams to boundary one in conformal perturbation theory.
Uniqueness of Gibbs Measure for Models with Uncountable Set of Spin Values on a Cayley Tree
International Nuclear Information System (INIS)
Eshkabilov, Yu. Kh.; Haydarov, F. H.; Rozikov, U. A.
2013-01-01
We consider models with nearest-neighbor interactions and with the set [0, 1] of spin values, on a Cayley tree of order K ≥ 1. It is known that the ‘splitting Gibbs measures’ of the model can be described by solutions of a nonlinear integral equation. For arbitrary k ≥ 2 we find a sufficient condition under which the integral equation has unique solution, hence under the condition the corresponding model has unique splitting Gibbs measure.
International Nuclear Information System (INIS)
Bobak, Andrej; Dely, Jan; Pokorny, Vladislav
2010-01-01
The effects of both an exchange anisotropy and a single-ion anisotropy on the magnetic susceptibility of the mixed spin-1 and spin- 1/2 Heisenberg model are investigated by the use of an Oguchi approximation. Particular emphasis is given to the simple cubic lattice with coordination number z = 6 for which the magnetic susceptibility is determined numerically. Anomalous behaviour in the thermal variation of the magnetic susceptibility in the low-temperature region is found due to the applied negative single-ion anisotropy field strength. Also, the difference between the behaviours of the magnetic susceptibility of the Heisenberg and Ising models is discussed.
Healy, Frederick M.
1958-01-01
A supplementary investigation to determine the effect of external fuel tanks on the spin and recovery characteristics of a l/28-scale model of the North American FJ-4 airplane has been conducted in the Langley 20-foot free-spinning tunnel. The model had been extensively tested previously (NACA Research Memorandum SL38A29) and therefore only brief tests were made to evaluate the effect of tank installation. Erect spin tests of the model indicate that flat-type spins-are more prevalent with 200-gallon external fuel tanks than with tanks not installed. The recovery technique determined for spins without tanks, rudder reversal to full against the spin accompanied by simultaneous movement of ailerons to full with the spin, is recommended for spins encountered with external tanks installed. If inverted spins are encountered with external tanks installed, the tanks should be jettisoned and recovery attempted by rudder reversal to full against the spin with ailerons maintained at neutral.
BETR global - A geographically-explicit global-scale multimedia contaminant fate model
International Nuclear Information System (INIS)
MacLeod, Matthew; Waldow, Harald von; Tay, Pascal; Armitage, James M.; Woehrnschimmel, Henry; Riley, William J.; McKone, Thomas E.; Hungerbuhler, Konrad
2011-01-01
We present two new software implementations of the BETR Global multimedia contaminant fate model. The model uses steady-state or non-steady-state mass-balance calculations to describe the fate and transport of persistent organic pollutants using a desktop computer. The global environment is described using a database of long-term average monthly conditions on a 15 o x 15 o grid. We demonstrate BETR Global by modeling the global sources, transport, and removal of decamethylcyclopentasiloxane (D5). - Two new software implementations of the Berkeley-Trent Global Contaminant Fate Model are available. The new model software is illustrated using a case study of the global fate of decamethylcyclopentasiloxane (D5).
Spin-dependent level density in interacting Boson-Fermion-Fermion model of the Odd-Odd Nucleus 196Au
International Nuclear Information System (INIS)
Kabashi, S.; Bekteshi, S.; Ahmetaj, S.; Shaqiri, Z.
2009-01-01
The level density of the odd-odd nucleus 196 Au is investigated in the interacting boson-fermion-fermion model (IBFFM) which accounts for collectivity and complex interaction between quasiparticle and collective modes.The IBFFM spin-dependent level densities show high-spin reduction with respect to Bethe formula.This can be well accounted for by a modified spin-dependent level density formula. (authors)
Modelling and analysis of global coal markets
International Nuclear Information System (INIS)
Trueby, Johannes
2013-01-01
International Steam Coal Trade. In this paper, we analyse steam coal market equilibria in the years 2006 and 2008 by testing for two possible market structure scenarios: perfect competition and an oligopoly setup with major exporters competing in quantities. The assumed oligopoly scenario cannot explain market equilibria for any year. While we find that the competitive model simulates market equilibria well in 2006, the competitive model is not able to reproduce real market outcomes in 2008. The analysis shows that not all available supply capacity was utilised in 2008. We conclude that either unknown capacity bottlenecks or more sophisticated non-competitive strategies were the cause for the high prices in 2008. Chapter 4 builds upon the findings of the analysis in chapter 3 and adds a more detailed representation of domestic markets. The corresponding essay is titled Nations as Strategic Players in Global Commodity Markets: Evidence from World Coal Trade. In this chapter we explore the hypothesis that export policies and trade patterns of national players in the steam coal market are consistent with non-competitive market behaviour. We test this hypothesis by developing a static equilibrium model which is able to model coal producing nations as strategic players. We explicitly account for integrated seaborne trade and domestic markets. The global steam coal market is simulated under several imperfect market structure setups. We find that trade and prices of a China - Indonesia duopoly fits the real market outcome best and that real Chinese export quotas in 2008 were consistent with simulated exports under a Cournot-Nash strategy. Chapter 5 looks at the long-term effect of Chinese energy system planning decisions. The time horizon is 2006 to 2030. The analysis in this chapter combines a dynamic equilibrium model with the scenario analysis technique. The corresponding essay is titled Coal Lumps vs. Electrons: How Do Chinese Bulk Energy Transport Decisions Affect the Global
Modelling and analysis of global coal markets
Energy Technology Data Exchange (ETDEWEB)
Trueby, Johannes
2013-01-17
International Steam Coal Trade. In this paper, we analyse steam coal market equilibria in the years 2006 and 2008 by testing for two possible market structure scenarios: perfect competition and an oligopoly setup with major exporters competing in quantities. The assumed oligopoly scenario cannot explain market equilibria for any year. While we find that the competitive model simulates market equilibria well in 2006, the competitive model is not able to reproduce real market outcomes in 2008. The analysis shows that not all available supply capacity was utilised in 2008. We conclude that either unknown capacity bottlenecks or more sophisticated non-competitive strategies were the cause for the high prices in 2008. Chapter 4 builds upon the findings of the analysis in chapter 3 and adds a more detailed representation of domestic markets. The corresponding essay is titled Nations as Strategic Players in Global Commodity Markets: Evidence from World Coal Trade. In this chapter we explore the hypothesis that export policies and trade patterns of national players in the steam coal market are consistent with non-competitive market behaviour. We test this hypothesis by developing a static equilibrium model which is able to model coal producing nations as strategic players. We explicitly account for integrated seaborne trade and domestic markets. The global steam coal market is simulated under several imperfect market structure setups. We find that trade and prices of a China - Indonesia duopoly fits the real market outcome best and that real Chinese export quotas in 2008 were consistent with simulated exports under a Cournot-Nash strategy. Chapter 5 looks at the long-term effect of Chinese energy system planning decisions. The time horizon is 2006 to 2030. The analysis in this chapter combines a dynamic equilibrium model with the scenario analysis technique. The corresponding essay is titled Coal Lumps vs. Electrons: How Do Chinese Bulk Energy Transport Decisions Affect the Global
Long-wavelength spin-effective actions for the infinite U Hubbard model
Braghin, Fábio L.
2013-04-01
The derivation of spin-effective actions is envisaged for the Hubbard model with infinite Coulomb repulsion for a very low concentration of holes with a slave fermion representation for electronic operators. For that, spinless charge variables (vacancies or holes) are integrated out and the resulting effective action at finite temperature is expanded up to the fourth order in the hopping term as proposed in reference [F.L. Braghin, A. Ferraz, E.A. Kochetov, Phys. Rev. B 78, 115109 (2008)] and, in a square lattice, the fourth order term is shown to have the structure of an extended gauge invariant J-Q model for localized spins. Two cases for which the resulting model is non trivial are analysed and they correspond basically to (1) holes hopping between two sub-lattices and (2) a time-dependent solution for the spinon variables in the square lattice. Whereas the first of these cases yields, at the leading order, an effective antiferromagnetic Heisenberg coupling for localized spins and the second one may lead either to ferromagnetic or antiferromagnetic effective coupling. In the second case, the ordering should appear rather in finite size domains and, although charge variables were integrated out, a subtle imbalance between charge degrees of freedom and spins should be at work.
Passarelli, G.; De Filippis, G.; Cataudella, V.; Lucignano, P.
2018-02-01
We investigate the quantum annealing of the ferromagnetic p -spin model in a dissipative environment (p =5 and p =7 ). This model, in the large-p limit, codifies Grover's algorithm for searching in an unsorted database [L. K. Grover, Proceedings of the 28th Annual ACM Symposium on Theory of Computing (ACM, New York, 1996), pp. 212-219]. The dissipative environment is described by a phonon bath in thermal equilibrium at finite temperature. The dynamics is studied in the framework of a Lindblad master equation for the reduced density matrix describing only the spins. Exploiting the symmetries of our model Hamiltonian, we can describe many spins and extrapolate expected trends for large N and p . While at weak system-bath coupling the dissipative environment has detrimental effects on the annealing results, we show that in the intermediate-coupling regime, the phonon bath seems to speed up the annealing at low temperatures. This improvement in the performance is likely not due to thermal fluctuation but rather arises from a correlated spin-bath state and persists even at zero temperature. This result may pave the way to a new scenario in which, by appropriately engineering the system-bath coupling, one may optimize quantum annealing performances below either the purely quantum or the classical limit.
Nonequilibrium dynamics of spin-boson models from phase-space methods
Piñeiro Orioli, Asier; Safavi-Naini, Arghavan; Wall, Michael L.; Rey, Ana Maria
2017-09-01
An accurate description of the nonequilibrium dynamics of systems with coupled spin and bosonic degrees of freedom remains theoretically challenging, especially for large system sizes and in higher than one dimension. Phase-space methods such as the truncated Wigner approximation (TWA) have the advantage of being easily scalable and applicable to arbitrary dimensions. In this work we adapt the TWA to generic spin-boson models by making use of recently developed algorithms for discrete phase spaces [J. Schachenmayer, A. Pikovski, and A. M. Rey, Phys. Rev. X 5, 011022 (2015), 10.1103/PhysRevX.5.011022]. Furthermore we go beyond the standard TWA approximation by applying a scheme based on the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy of equations to our coupled spin-boson model. This allows us, in principle, to study how systematically adding higher-order corrections improves the convergence of the method. To test various levels of approximation we study an exactly solvable spin-boson model, which is particularly relevant for trapped-ion arrays. Using TWA and its BBGKY extension we accurately reproduce the time evolution of a number of one- and two-point correlation functions in several dimensions and for an arbitrary number of bosonic modes.
New spin Calogero-Sutherland models related to BN-type Dunkl operators
International Nuclear Information System (INIS)
Finkel, F.; Gomez-Ullate, D.; Gonzalez-Lopez, A.; Rodriguez, M.A.; Zhdanov, R.
2001-01-01
We construct several new families of exactly and quasi-exactly solvable BC N -type Calogero-Sutherland models with internal degrees of freedom. Our approach is based on the introduction of a new family of Dunkl operators of B N type which, together with the original B N -type Dunkl operators, are shown to preserve certain polynomial subspaces of finite dimension. We prove that a wide class of quadratic combinations involving these three sets of Dunkl operators always yields a spin Calogero-Sutherland model, which is (quasi-)exactly solvable by construction. We show that all the spin Calogero-Sutherland models obtainable within this framework can be expressed in a unified way in terms of a Weierstrass ζ function with suitable half-periods. This provides a natural spin counterpart of the well-known general formula for a scalar completely integrable potential of BC N type due to Olshanetsky and Perelomov. As an illustration of our method, we exactly compute several energy levels and their corresponding wavefunctions of an elliptic quasi-exactly solvable potential for two and three particles of spin 1/2
Energy Technology Data Exchange (ETDEWEB)
Zhang, G.P., E-mail: bugubird_zhang@hotmail.com [Department of Physics, Renmin University of China, Beijing 100872 (China); Zhang, Jian [3M Company, 3M Corporate Headquarters, 3M Center, St. Paul, MN 55144-1000 (United States); Zhang, Qi-Li [Data Center for High Energy Density Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Zhou, Jiang-Tao [College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Shangguan, M.H. [Department of Physics, Renmin University of China, Beijing 100872 (China)
2013-05-15
Unconventional anomalous Hall effect in frustrated pyrochlore oxides is originated from spin chirality of non-coplanar localized spins, which can also be induced by the competition between ferromagnetic (FM) double exchange interaction J{sub H} and antiferromagnetic superexchange interaction J{sub AF}. Here truncated polynomial expansion method and Monte Carlo simulation are adopted to investigate the above model on two-dimensional triangular lattice. We discuss the influence of the range of FM-type spin–spin correlation and strong electron–spin correlation on the truncation error of spin–spin correlation near quarter filling. Two peaks of the probability distribution of spin–spin correlation in non-coplanar spin configuration clearly show that non-coplanar spin configuration is an intermediate phase between FM and 120° spin phase. Near quarter filling, there is a phase transition from FM into non-coplanar and further into 120° spin phase when J{sub AF} continually increases. Finally the effect of temperature on the magnetic structure is discussed.
BETR Global - A geographically explicit global-scale multimedia contaminant fate model
Energy Technology Data Exchange (ETDEWEB)
Macleod, M.; Waldow, H. von; Tay, P.; Armitage, J. M.; Wohrnschimmel, H.; Riley, W.; McKone, T. E.; Hungerbuhler, K.
2011-04-01
We present two new software implementations of the BETR Global multimedia contaminant fate model. The model uses steady-state or non-steady-state mass-balance calculations to describe the fate and transport of persistent organic pollutants using a desktop computer. The global environment is described using a database of long-term average monthly conditions on a 15{sup o} x 15{sup o} grid. We demonstrate BETR Global by modeling the global sources, transport, and removal of decamethylcyclopentasiloxane (D5).
Moduli stabilisation for chiral global models
International Nuclear Information System (INIS)
Cicoli, Michele; Mayrhofer, Christoph; Valandro, Roberto
2011-10-01
We combine moduli stabilisation and (chiral) model building in a fully consistent global set-up in Type IIB/F-theory. We consider compactifications on Calabi-Yau orientifolds which admit an explicit description in terms of toric geometry. We build globally consistent compactifications with tadpole and Freed-Witten anomaly cancellation by choosing appropriate brane set-ups and world-volume fluxes which also give rise to SU(5)- or MSSM-like chiral models. We fix all the Kaehler moduli within the Kaehler cone and the regime of validity of the 4D effective field theory. This is achieved in a way compatible with the local presence of chirality. The hidden sector generating the non-perturbative effects is placed on a del Pezzo divisor that does not have any chiral intersections with any other brane. In general, the vanishing D-term condition implies the shrinking of the rigid divisor supporting the visible sector. However, we avoid this problem by generating r< n D-term conditions on a set of n intersecting divisors. The remaining (n-r) flat directions are fixed by perturbative corrections to the Kaehler potential. We illustrate our general claims in an explicit example. We consider a K3-fibred Calabi-Yau with four Kaehler moduli, that is an hypersurface in a toric ambient space and admits a simple F-theory up-lift. We present explicit choices of brane set-ups and fluxes which lead to three different phenomenological scenarios: the first with GUT-scale strings and TeV-scale SUSY by fine-tuning the background fluxes; the second with an exponentially large value of the volume and TeV-scale SUSY without fine-tuning the background fluxes; and the third with a very anisotropic configuration that leads to TeV-scale strings and two micron-sized extra dimensions. The K3 fibration structure of the Calabi-Yau three-fold is also particularly suitable for cosmological purposes. (orig.)
Moduli stabilisation for chiral global models
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Abdus Salam International Centre for Theoretical Physics, Trieste (Italy); Mayrhofer, Christoph [Heidelberg Univ. (Germany). Inst. fuer Theoretische Physik; Valandro, Roberto [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2011-10-15
We combine moduli stabilisation and (chiral) model building in a fully consistent global set-up in Type IIB/F-theory. We consider compactifications on Calabi-Yau orientifolds which admit an explicit description in terms of toric geometry. We build globally consistent compactifications with tadpole and Freed-Witten anomaly cancellation by choosing appropriate brane set-ups and world-volume fluxes which also give rise to SU(5)- or MSSM-like chiral models. We fix all the Kaehler moduli within the Kaehler cone and the regime of validity of the 4D effective field theory. This is achieved in a way compatible with the local presence of chirality. The hidden sector generating the non-perturbative effects is placed on a del Pezzo divisor that does not have any chiral intersections with any other brane. In general, the vanishing D-term condition implies the shrinking of the rigid divisor supporting the visible sector. However, we avoid this problem by generating r
International Nuclear Information System (INIS)
Baktybaev, K.; Koilyk, N.; Ramankulov, K.
2006-01-01
Full text: Collective Schrodinger equations are applied to describe low-energy spectra of even-even nuclei [1]. Spectra for even-odd nuclei are calculated by coupling the single particle degrees of freedom to the collective degree of freedom of the core nucleus, which is of even-even type. The collective spin has a value of 3/2. This leads to the assumption that the linearized equation may be applied to describe nuclei with spin 3/2 in the ground state. Good description of the low energy spectra and electromagnetic transition probabilities can be obtained only with introduction of spin-dependent potentials, which apart from coordinates and momenta also depend on the matrices of the Clifford algebra arising in the linearization,. The interacting boson-fermion models (IBFM) [2] represent another approach to describe spectra of even-odd nuclei. For even-odd nuclei with spin 3/2 in the ground state one uses so-called j=3/2 - IBFM, which is also denoted as the U B (6)xU F (4) IBFM. In this paper we establish the relation between the matrices of the Clifford algebra, which arise in the linearization procedure, and the fermion operators of the j=3/2 IBFM. This allows us to establish a connection between the j=3/2 IBFM and spin dependent generalized collective model (SGCM). The results of the SGCM for Ir and Au nuclei are presented and compared with the results of the j=3/2 IBFM with a dynamical spin symmetry [3] present. In this respect we could apply the linearized collective Schrodinger equation and IBFM with arbitrary spin to all other even-odd nuclei. (author)
Cold Attractive Spin Polarized Fermi Lattice Gases and the Doped Positive U Hubbard Model
International Nuclear Information System (INIS)
Moreo, Adriana; Scalapino, D. J.
2007-01-01
Experiments on polarized fermion gases performed by trapping ultracold atoms in optical lattices allow the study of an attractive Hubbard model for which the strength of the on-site interaction is tuned by means of a Feshbach resonance. Using a well-known particle-hole transformation we discuss how results obtained for this system can be reinterpreted in the context of a doped repulsive Hubbard model. In particular, we show that the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state corresponds to the striped state of the two-dimensional doped positive U Hubbard model. We then use the results of numerical studies of the striped state to relate the periodicity of the FFLO state to the spin polarization. We also comment on the relationship of the d x 2 -y 2 superconducting phase of the doped 2D repulsive Hubbard model to a d-wave spin density wave state for the attractive case
Simplified dark matter models with a spin-2 mediator at the LHC
Energy Technology Data Exchange (ETDEWEB)
Kraml, Sabine [Universite Grenoble-Alpes, CNRS/IN2P3, Laboratoire de Physique Subatomique et de Cosmologie, Grenoble (France); Laa, Ursula [Universite Grenoble-Alpes, CNRS/IN2P3, Laboratoire de Physique Subatomique et de Cosmologie, Grenoble (France); LAPTh, Universite Savoie Mont Blanc, CNRS, B.P.110, Annecy Cedex (France); Mawatari, Kentarou [Universite Grenoble-Alpes, CNRS/IN2P3, Laboratoire de Physique Subatomique et de Cosmologie, Grenoble (France); Theoretische Natuurkunde and IIHE/ELEM, Vrije Universiteit Brussel, and International Solvay Institutes, Brussels (Belgium); Yamashita, Kimiko [Ochanomizu University, Department of Physics, Graduate School of Humanities and Sciences, and Program for Leading Graduate Schools, Tokyo (Japan)
2017-05-15
We consider simplified dark matter models where a dark matter candidate couples to the standard model (SM) particles via an s-channel spin-2 mediator, and study constraints on the model parameter space from the current LHC data. Our focus lies on the complementarity among different searches, in particular monojet and multijet plus missing-energy searches and resonance searches. For universal couplings of the mediator to SM particles, missing-energy searches can give stronger constraints than WW, ZZ, dijet, dihiggs, t anti t, b anti b resonance searches in the low-mass region and/or when the coupling of the mediator to dark matter is much larger than its couplings to SM particles. The strongest constraints, however, come from diphoton and dilepton resonance searches. Only if these modes are suppressed, missing-energy searches can be competitive in constraining dark matter models with a spin-2 mediator. (orig.)
Simplified dark matter models with a spin-2 mediator at the LHC
International Nuclear Information System (INIS)
Kraml, Sabine; Laa, Ursula; Mawatari, Kentarou; Yamashita, Kimiko
2017-01-01
We consider simplified dark matter models where a dark matter candidate couples to the standard model (SM) particles via an s-channel spin-2 mediator, and study constraints on the model parameter space from the current LHC data. Our focus lies on the complementarity among different searches, in particular monojet and multijet plus missing-energy searches and resonance searches. For universal couplings of the mediator to SM particles, missing-energy searches can give stronger constraints than WW, ZZ, dijet, dihiggs, t anti t, b anti b resonance searches in the low-mass region and/or when the coupling of the mediator to dark matter is much larger than its couplings to SM particles. The strongest constraints, however, come from diphoton and dilepton resonance searches. Only if these modes are suppressed, missing-energy searches can be competitive in constraining dark matter models with a spin-2 mediator. (orig.)
Frequency-domain reduced order models for gravitational waves from aligned-spin compact binaries
International Nuclear Information System (INIS)
Pürrer, Michael
2014-01-01
Black-hole binary coalescences are one of the most promising sources for the first detection of gravitational waves. Fast and accurate theoretical models of the gravitational radiation emitted from these coalescences are highly important for the detection and extraction of physical parameters. Spinning effective-one-body models for binaries with aligned-spins have been shown to be highly faithful, but are slow to generate and thus have not yet been used for parameter estimation (PE) studies. I provide a frequency-domain singular value decomposition-based surrogate reduced order model that is thousands of times faster for typical system masses and has a faithfulness mismatch of better than ∼0.1% with the original SEOBNRv1 model for advanced LIGO detectors. This model enables PE studies up to signal-to-noise ratios (SNRs) of 20 and even up to 50 for total masses below 50 M ⊙ . This paper discusses various choices for approximations and interpolation over the parameter space that can be made for reduced order models of spinning compact binaries, provides a detailed discussion of errors arising in the construction and assesses the fidelity of such models. (paper)
Spin-Tunnel Investigation of a 1/20-Scale Model of the Northrop F-5E Airplane
Scher, Stanley H.; White, William L.
1977-01-01
An investigation has been conducted in the Langley spin tunnel to determine the spin and recovery characteristics of a 1/20-scale model of the Northrop F-5E airplane. The investigation included erect and inverted spins, a range of center-of- gravity locations and moments of inertia, symmetric and asymmetric store loadings, and a determination of the parachute size required for emergency spin recovery. The effects of increased elevator trailing-edge-up deflections, of leading-edge and trailing-edge flap deflections, and of simulating the geometry of large external stores were also determined.
International Nuclear Information System (INIS)
Gridneva, S.A.; Rus'kin, V.I.
1980-01-01
Basic features of the statistical model of multiple hadron production based on microcanonical distribution and taking into account the laws of conservation of total angular momentum, isotopic spin, p-, G-, C-eveness and Bose-Einstein statistics requirements are given. The model predictions are compared with experimental data on anti NN annihilation at rest and e + e - annihilation in hadrons at annihilation total energy from 2 to 3 GeV [ru
Light-cone quark model with spin force for the nucleon and Δ(1232)
International Nuclear Information System (INIS)
Weber, H.J.
1992-01-01
Electromagnetic structure functions for the nucleon, static observables for the nucleon and N→D(1232) transition form factors are calculated in a relativistic constituent quark model on the light cone. The model simulates the main effect of the spin force between quarks in terms of smaller (and lighter) scalar ud diquarks in the nucleon. The polarized proton structure function is found to agree with the EMC data. (orig.)
Global plastic models for computerized structural analysis
International Nuclear Information System (INIS)
Roche, R.; Hoffmann, A.
1977-01-01
Two different global models are used in the CEASEMT system for structural analysis, one for the shells analysis and the other for piping analysis (in plastic or creep field). In shell analysis the generalized stresses choosed are the membrane forces Nsub(ij) and bending (including torsion) moments Msub(ij). There is only one yield condition for a normal (to the middle surface) and no integration along the thickness is required. In piping analysis, the choice of generalized stresses is: bending moments, torsional moments, Hoop stress and tension stress. There is only a set of stresses for a cross section and non integration over the cross section area is needed. Connected strains are axis curvature, torsion, uniform strains. The definition of the yield surface is the most important item. A practical way is to use a diagonal quadratic fonction of the stress components. But the coefficients are depending of the shape of the pipe element, especially for curved segments. Indications will be given on the yield fonctions used. Some examples of applications in structural analysis are added to the text [fr
The Canadian Centre for Climate Modelling and Analysis global coupled model and its climate
Energy Technology Data Exchange (ETDEWEB)
Flato, G.M.; Boer, G.J.; Lee, W.G.; McFarlane, N.A.; Ramsden, D.; Reader, M.C. [Canadian Centre for Climate Modelling and Analysis, Victoria, BC (Canada); Weaver, A.J. [School of Earth and Ocean Sciences, University of Victoria, BC (Canada)
2000-06-01
A global, three-dimensional climate model, developed by coupling the CCCma second-generation atmospheric general circulation model (GCM2) to a version of the GFDL modular ocean model (MOM1), forms the basis for extended simulations of past, current and projected future climate. The spin-up and coupling procedures are described, as is the resulting climate based on a 200 year model simulation with constant atmospheric composition and external forcing. The simulated climate is systematically compared to available observations in terms of mean climate quantities and their spatial patterns, temporal variability, and regional behavior. Such comparison demonstrates a generally successful reproduction of the broad features of mean climate quantities, albeit with local discrepancies. Variability is generally well-simulated over land, but somewhat underestimated in the tropical ocean and the extratropical storm-track regions. The modelled climate state shows only small trends, indicating a reasonable level of balance at the surface, which is achieved in part by the use of heat and freshwater flux adjustments. The control simulation provides a basis against which to compare simulated climate change due to historical and projected greenhouse gas and aerosol forcing as described in companion publications. (orig.)
International Nuclear Information System (INIS)
Schuettler, H.; Norman, M.R.
1996-01-01
We compare the normal-state resistivities ρ and the critical temperatures T c for superconducting d x 2 -y 2 pairing due to antiferromagnetic (AF) spin fluctuation exchange in the context of two phenomenological dynamical spin susceptibility models for the cuprate high-T c materials, one based on fits to NMR data on Y-Ba-Cu-O (YBCO) proposed by Millis, Monien, and Pines (MMP) and Monthoux and Pines (MP), and the other based on fits to neutron scattering data on YBCO proposed by Radtke, Ullah, Levin, and Norman (RULN). Assuming comparable electronic bandwidths and resistivities in both models, we show that the RULN model gives a much lower d-wave T c (approx-lt 20 K) than the MMP model (with T c ∼100 K). We demonstrate that these profound differences in the T c close-quote s arise from fundamental differences in the spectral weight distributions of the two model susceptibilities at high (>100 meV) frequencies and are not primarily caused by differences in the calculational techniques employed by MP and RULN. Further neutron scattering experiments, to explore the spectral weight distribution at all wave vectors over a sufficiently large excitation energy range, will thus be of crucial importance to resolve the question whether AF spin fluctuation exchange can provide a viable mechanism to account for high-T c superconductivity. Limitations of the Migdal-Eliashberg approach in such models will be discussed. copyright 1996 The American Physical Society
Technical Note: Reducing the spin-up time of integrated surface water–groundwater models
Ajami, H.
2014-12-12
One of the main challenges in the application of coupled or integrated hydrologic models is specifying a catchment\\'s initial conditions in terms of soil moisture and depth-to-water table (DTWT) distributions. One approach to reducing uncertainty in model initialization is to run the model recursively using either a single year or multiple years of forcing data until the system equilibrates with respect to state and diagnostic variables. However, such "spin-up" approaches often require many years of simulations, making them computationally intensive. In this study, a new hybrid approach was developed to reduce the computational burden of the spin-up procedure by using a combination of model simulations and an empirical DTWT function. The methodology is examined across two distinct catchments located in a temperate region of Denmark and a semi-arid region of Australia. Our results illustrate that the hybrid approach reduced the spin-up period required for an integrated groundwater–surface water–land surface model (ParFlow.CLM) by up to 50%. To generalize results to different climate and catchment conditions, we outline a methodology that is applicable to other coupled or integrated modeling frameworks when initialization from an equilibrium state is required.
The topological B model as a twisted spinning particle
International Nuclear Information System (INIS)
Marcus, Neil; Yankielowicz, Shimon
1994-01-01
The B-twisted topological sigma model coupled to topological gravity is supposed to be described by an ordinary field theory: a type of holomorphic Chern-Simons theory for the open string, and the Kodaira-Spencer theory for the closed string. We show that the B model can be represented as a particle theory, obtained by reducing the sigma model to one dimension, and replacing the coupling to topological gravity by a coupling to a twisted one-dimensional supergravity. The particle can be defined on any Kaehler manifold - it does not require the Calabi-Yau condition - so it may provide a more generalized setting for the B model than the topological sigma model.The one-loop partition function of the particle can be written in terms of the Ray-Singer torsion of the manifold, and agrees with that of the original B model. After showing how to deform the Kaehler and complex structures in the particle, we prove the independence of this partition function on the Kaehler structure, and investigate the origin of the holomorphic anomaly. To define other amplitudes, one needs to introduce interactions into the particle. The particle will then define a field theory, which may or may not be the Chern-Simons or Kodaira-Spencer theories. ((orig.))
Uimin-Lai-Sutherland spin-3/2 chain model in terms of fermion creation and annihilation operators
International Nuclear Information System (INIS)
Mirumyan, M.B.
2002-01-01
The Uimin-Lai-Sutherland spin-3/2 chain model is investigated. The representation of the su(2) algebra for the spin 3/2 is constructed in the linear space of the creation and annihilation operators of three fermions. Expressions are obtained for the Hamiltonian and energy spectrum as well as the corresponding Bethe equations are derived
Uimin-Lai-Sutherland spin-3/2 chain model in terms of fermion creation and annihilation operators
Mirumyan, M B
2002-01-01
The Uimin-Lai-Sutherland spin-3/2 chain model is investigated. The representation of the su(2) algebra for the spin 3/2 is constructed in the linear space of the creation and annihilation operators of three fermions. Expressions are obtained for the Hamiltonian and energy spectrum as well as the corresponding Bethe equations are derived.
Global Information Enterprise (GIE) Modeling and Simulation (GIESIM)
National Research Council Canada - National Science Library
Bell, Paul
2005-01-01
... AND S) toolkits into the Global Information Enterprise (GIE) Modeling and Simulation (GIESim) framework to create effective user analysis of candidate communications architectures and technologies...
Magnetic properties of Fe–Al for quenched diluted spin-1 Ising model
International Nuclear Information System (INIS)
Freitas, A.S.; Albuquerque, Douglas F. de; Fittipaldi, I.P.; Moreno, N.O.
2014-01-01
We study the phase diagram of Fe 1−q Al q alloys via the quenched site diluted spin-1 ferromagnetic Ising model by employing effective field theory. One suggests a new approach to exchange interaction between nearest neighbors of Fe that depends on the powers of the Al (q) instead of the linear dependence proposed in other papers. In such model we propose the same kind of the exchange interaction in which the iron–nickel alloys obtain an excellent theoretical description of the experimental data of the T–q phase diagram for all Al concentration q. - Highlights: • We apply the quenched Ising model spin-1 to study the properties of Fe–Al. • We employ the EFT and suggest a new approach to ferromagnetic coupling. • The new probability distribution is considered. • The phase diagram is obtained for all values of q in T–q plane
Magnetic properties of Fe–Al for quenched diluted spin-1 Ising model
Energy Technology Data Exchange (ETDEWEB)
Freitas, A.S. [Departamento de Física, Universidade Federal de Sergipe, 49100-000, São Cristovão, SE (Brazil); Coordenadoria de Física, Instituto Federal de Sergipe, 49400-000 Lagarto, SE (Brazil); Albuquerque, Douglas F. de, E-mail: douglas@ufs.br [Departamento de Física, Universidade Federal de Sergipe, 49100-000, São Cristovão, SE (Brazil); Departamento de Matemática, Universidade Federal de Sergipe, 49100-000, São Cristovão, SE (Brazil); Fittipaldi, I.P. [Representação Regional do Ministério da Ciência, Tecnologia e Inovação no Nordeste - ReNE, 50740-540 Recife, PE (Brazil); Moreno, N.O. [Departamento de Física, Universidade Federal de Sergipe, 49100-000, São Cristovão, SE (Brazil)
2014-08-01
We study the phase diagram of Fe{sub 1−q}Al{sub q} alloys via the quenched site diluted spin-1 ferromagnetic Ising model by employing effective field theory. One suggests a new approach to exchange interaction between nearest neighbors of Fe that depends on the powers of the Al (q) instead of the linear dependence proposed in other papers. In such model we propose the same kind of the exchange interaction in which the iron–nickel alloys obtain an excellent theoretical description of the experimental data of the T–q phase diagram for all Al concentration q. - Highlights: • We apply the quenched Ising model spin-1 to study the properties of Fe–Al. • We employ the EFT and suggest a new approach to ferromagnetic coupling. • The new probability distribution is considered. • The phase diagram is obtained for all values of q in T–q plane.
International Nuclear Information System (INIS)
Tao, Ruibao.
1991-09-01
A method is developed to make a Bose transformation which is restricted in proper space. A self-consistent independent spin wave representation (SCISWR) is found for two dimensional isotropic antiferromagnet of Heisenberg square lattices. In the SCISWR, we have successfully done the renormalization from both the dynamic and kinematic interaction and calculated the corrections from the correlations of the nearest neighbour and next nearest neighbour sites. An anisotropic excitation energy of spin wave in improper space is found self-consistently and has a gap. The difficulty of divergence appearing from higher order perturbation terms in the conventional spin wave theory has been overcome and the convergence in our approach seems quite good. We find the energy of ground state E approx. -0.659 in low order approximation and the magnetization of sublattice M z = 0.430 x (N/2) for system with spin 1/2. It is also proved that a physical spin excitation restricted in proper space is still isotropic and has no gap. (author). 17 refs
2D higher spin gravity and the multimatrix models
International Nuclear Information System (INIS)
Awada, M.; Qiu Zongan
1990-01-01
We quantize W-gravity coupled to matter fields in the conformal gauge and obtain the critical exponents. We demonstrate explicitly how the generators of the W-algebra are described by an infinite set of conserved charges of the KdV hierarchy. We obtain the generalized hamiltonian equation of motion and show that it contains the class of universal differential equations of the matrix models. Thus we propose that these models describe pure W-gravity theories of the A-type. Consequently we give a new set of universal equations that correspond to other types of W-gravity theories. (orig.)
Technical Note: Reducing the spin-up time of integrated surface water–groundwater models
Ajami, H.
2014-06-26
One of the main challenges in catchment scale application of coupled/integrated hydrologic models is specifying a catchment\\'s initial conditions in terms of soil moisture and depth to water table (DTWT) distributions. One approach to reduce uncertainty in model initialization is to run the model recursively using a single or multiple years of forcing data until the system equilibrates with respect to state and diagnostic variables. However, such "spin-up" approaches often require many years of simulations, making them computationally intensive. In this study, a new hybrid approach was developed to reduce the computational burden of spin-up time for an integrated groundwater-surface water-land surface model (ParFlow.CLM) by using a combination of ParFlow.CLM simulations and an empirical DTWT function. The methodology is examined in two catchments located in the temperate and semi-arid regions of Denmark and Australia respectively. Our results illustrate that the hybrid approach reduced the spin-up time required by ParFlow.CLM by up to 50%, and we outline a methodology that is applicable to other coupled/integrated modelling frameworks when initialization from equilibrium state is required.
SEP modeling based on global heliospheric models at the CCMC
Mays, M. L.; Luhmann, J. G.; Odstrcil, D.; Bain, H. M.; Schwadron, N.; Gorby, M.; Li, Y.; Lee, K.; Zeitlin, C.; Jian, L. K.; Lee, C. O.; Mewaldt, R. A.; Galvin, A. B.
2017-12-01
Heliospheric models provide contextual information of conditions in the heliosphere, including the background solar wind conditions and shock structures, and are used as input to SEP models, providing an essential tool for understanding SEP properties. The global 3D MHD WSA-ENLIL+Cone model provides a time-dependent background heliospheric description, into which a spherical shaped hydrodynamic CME can be inserted. ENLIL simulates solar wind parameters and additionally one can extract the magnetic topologies of observer-connected magnetic field lines and all plasma and shock properties along those field lines. An accurate representation of the background solar wind is necessary for simulating transients. ENLIL simulations also drive SEP models such as the Solar Energetic Particle Model (SEPMOD) (Luhmann et al. 2007, 2010) and the Energetic Particle Radiation Environment Module (EPREM) (Schwadron et al. 2010). The Community Coordinated Modeling Center (CCMC) is in the process of making these SEP models available to the community and offering a system to run SEP models driven by a variety of heliospheric models available at CCMC. SEPMOD injects protons onto a sequence of observer field lines at intensities dependent on the connected shock source strength which are then integrated at the observer to approximate the proton flux. EPREM couples with MHD models such as ENLIL and computes energetic particle distributions based on the focused transport equation along a Lagrangian grid of nodes that propagate out with the solar wind. The coupled SEP models allow us to derive the longitudinal distribution of SEP profiles of different types of events throughout the heliosphere. The coupled ENLIL and SEP models allow us to derive the longitudinal distribution of SEP profiles of different types of events throughout the heliosphere. In this presentation we demonstrate several case studies of SEP event modeling at different observers based on WSA-ENLIL+Cone simulations.
Globalization and Shanghai Model: A Retrospective and Prospective Analysis
Directory of Open Access Journals (Sweden)
Linsun Cheng
2012-11-01
Full Text Available Intended to shed light on the debate on the results of globalization and providebetter understanding of the influences of globalization upon China as well as theworld, this article traces the history of Shanghai’s economic globalization over thepast 170 years since 1843 and demonstrates the benefits and problems Shanghaireceived from (or connected to its economic globalization. Divided into threesections (Globalization, de-globalization and re-globalization of Shanghai’s economy;Manufacturing-Oriented vs. Tertiary-oriented—Shanghai’s Double PriorityStrategy of Economic Growth; Free market, state enterprises, and Shanghai’s mixedeconomy the article summarizes and analyzes several characteristics that madeShanghai a unique model in the history of globalization: In adapting and adoptinginevitable economic globalization, Shanghai created its unique model of economicdevelopment—widely embracing economic globalization; placing Shanghai’seconomy on a solid foundation of both strong modern manufacturing and strongtertiary industry (consisting of finance and insurance, real estate, transportations,post and telecommunication, wholesale and retailing; and creating a mixedeconomic structure with hybrid of private and state owned enterprises. TheShanghai model proves that globalization has been an unavoidable trend as scienceand technology have made the world “smaller” and “smaller.” Actively engaging intoeconomic globalization is the only way for Shanghai, as well as many developingcountries, to accelerate its economic growth.
Raman scattering in cuprate superconductors : an analysis in the spin bag model
International Nuclear Information System (INIS)
Behera, S.N.; Gaitonde, D.M.
1992-01-01
The spin bag model for the high temperature superconductivity (SC) in the cuprates is reformulated, so that the spin density wave (SDW) collective mode mediated pairing interaction between the doped charge carriers, has a formal similarity to the usual phonon mediated BCS mechanism. The collective modes of the spin bag superconductor are calculated and the spectral density function for the amplitude mode is plotted. The self energy and the spectral density function of an optic phonon are calculated in the spin bag superconducting state. The spectral density function does not couple to the SDW-amplitude mode. A low frequency is shown to harden while the high frequency (greater than the SC-gap) one softens; which are features in qualitative agreement with the behaviour seen in the Raman data. When the phonon frequency is larger than the SC-gap, its spectral function shows a low frequency weak peak, attributed to the SC-gap excitation which is not observed experimentally. (author). 21 refs., 3 figs
Stability of superfluid phases in the 2D spin-polarized attractive Hubbard model
Kujawa-Cichy, A.; Micnas, R.
2011-08-01
We study the evolution from the weak coupling (BCS-like limit) to the strong coupling limit of tightly bound local pairs (LPs) with increasing attraction, in the presence of the Zeeman magnetic field (h) for d=2, within the spin-polarized attractive Hubbard model. The broken symmetry Hartree approximation as well as the strong coupling expansion are used. We also apply the Kosterlitz-Thouless (KT) scenario to determine the phase coherence temperatures. For spin-independent hopping integrals (t↑=t↓), we find no stable homogeneous polarized superfluid (SCM) state in the ground state for the strong attraction and obtain that for a two-component Fermi system on a 2D lattice with population imbalance, phase separation (PS) is favoured for a fixed particle concentration, even on the LP (BEC) side. We also examine the influence of spin-dependent hopping integrals (mass imbalance) on the stability of the SCM phase. We find a topological quantum phase transition (Lifshitz type) from the unpolarized superfluid phase (SC0) to SCM and tricritical points in the h-|U| and t↑/t↓-|U| ground-state phase diagrams. We also construct the finite temperature phase diagrams for both t↑=t↓ and t↑≠t↓ and analyze the possibility of occurrence of a spin-polarized KT superfluid.
Chappell, Michael A; Woolrich, Mark W; Petersen, Esben T; Golay, Xavier; Payne, Stephen J
2013-05-01
Amongst the various implementations of arterial spin labeling MRI methods for quantifying cerebral perfusion, the QUASAR method is unique. By using a combination of labeling with and without flow suppression gradients, the QUASAR method offers the separation of macrovascular and tissue signals. This permits local arterial input functions to be defined and "model-free" analysis, using numerical deconvolution, to be used. However, it remains unclear whether arterial spin labeling data are best treated using model-free or model-based analysis. This work provides a critical comparison of these two approaches for QUASAR arterial spin labeling in the healthy brain. An existing two-component (arterial and tissue) model was extended to the mixed flow suppression scheme of QUASAR to provide an optimal model-based analysis. The model-based analysis was extended to incorporate dispersion of the labeled bolus, generally regarded as the major source of discrepancy between the two analysis approaches. Model-free and model-based analyses were compared for perfusion quantification including absolute measurements, uncertainty estimation, and spatial variation in cerebral blood flow estimates. Major sources of discrepancies between model-free and model-based analysis were attributed to the effects of dispersion and the degree to which the two methods can separate macrovascular and tissue signal. Copyright © 2012 Wiley Periodicals, Inc.
National Aeronautics and Space Administration — The ability of the Global Hawk air vehicle to autonomously fly long distances and remain aloft for extended periods of time means that measuring, monitoring, and...
International Nuclear Information System (INIS)
Sergeenkov, S.; Moraes, F.; Furtado, C.; Araujo-Moreira, F.M.
2010-01-01
By mapping a Hubbard-like model describing a two-component polymer in the presence of strong enough electron-phonon interactions (κ) onto the system of two coupled nonlinear Schroedinger equations with U(2) symmetry group, some nontrivial correlations between topological solitons mediated charge Q and spin S degrees of freedom are obtained. Namely, in addition to a charge fractionalization and reentrant like behavior of both Q(κ) and S(κ), the model also predicts a decrease of soliton velocity with κ as well as spin-charge conversion effects which manifest themselves through an explicit S(Q,Ω) dependence (with Ω being a mixing angle between spin-up and spin-down electron amplitudes). A possibility to observe the predicted effects in low-dimensional systems with charge and spin soliton carriers is discussed.
Derivation of Green's function of a spin Calogero-Sutherland model by Uglov's method
International Nuclear Information System (INIS)
Nakai, Ryota; Kato, Yusuke
2009-01-01
The hole propagator of a spin 1/2 Calogero-Sutherland model is derived using Uglov's method, which maps the exact eigenfunctions of the model, called the Yangian Gelfand-Zetlin basis, to a limit of Macdonald polynomials (gl 2 -Jack polynomials). To apply this mapping method to the calculation of 1-particle Green's function, we confirm that the sum of the field annihilation operator ψ u + ψ ↓ on a Yangian Gelfand-Zetlin basis is transformed to the field annihilation operator ψ on gl 2 -Jack polynomials by the mapping. The resultant expression for the hole propagator for a finite-size system is written in terms of renormalized momenta and spin of quasi-holes, and the expression in the thermodynamic limit coincides with the earlier result derived by another method. We also discuss the singularity of the spectral function for a specific coupling parameter where the hole propagator of the spin Calogero-Sutherland model becomes equivalent to the dynamical colour correlation function of an SU(3) Haldane-Shastry model
Spin-glass-like transition in the majority-vote model with anticonformists
Krawiecki, Andrzej
2018-03-01
Majority-vote model on scale-free networks and random graphs is investigated in which a randomly chosen fraction p of agents (called anticonformists) follows an antiferromagnetic update rule, i.e., they assume, with probability governed by a parameter q (0 transition from a disordered (paramagnetic) state to a spin-glass-like state, characterized by a non-zero value of the spin-glass order parameter measuring the overlap of agents' opinions in two replicas of the system, and simultaneously by the magnetization close to zero. In the case of the model on scale-free networks the critical value of the parameter q weakly depends on the details of the degree distribution. As p is decreased, the critical value of q falls quickly to zero and only the disordered phase is observed. On the other hand, for p close to zero for decreasing q the usual ferromagnetic transition is observed.
Formation of spin-polarons in the ferromagnetic Kondo lattice model away from half-filling
International Nuclear Information System (INIS)
Arredondo, Y; Navarro, O; Vallejo, E; Avignon, M
2012-01-01
Even though realistic one-dimensional experiments in the field of half-metallic semiconductors are not at hand yet, we are interested in the underlying fundamental physics. In this regard we study a one-dimensional ferromagnetic Kondo lattice model, a model in which a conduction band is coupled ferromagnetically to a background of localized d moments with coupling constant J H , and investigate the T = 0 phase diagram as a function of the antiferromagnetic interaction J between the localized moments and the band-filling n, since it has been observed that doping of the compounds has led to formation of magnetic domains. We explore the spin-polaron formation by looking at the nearest-neighbour correlation functions in the spin and charge regimes for which we use the density matrix renormalization group method, which is a highly efficient method to investigate quasi-one-dimensional strongly correlated systems. (paper)
Resonance-sum model for Reggeization in the scattering of particles with arbitrary spin
International Nuclear Information System (INIS)
King, M.J.; Durand, L.; Wali, K.C.
1976-01-01
Using a field-theoretic description of nonzero-spin particles, center-of-mass helicity amplitudes have been obtained which correspond to pole terms in four-particle reactions with arbitrary-spin external particles. Construction of a van Hove-Durand--type model starting from these helicity amplitudes (which have a well specified kinematic structure in the field-theoretic description) is discussed. Special attention has been paid to boson-fermion scattering. Straightforward Reggeization of helicity amplitudes assuming linear trajectories is known to produce parity doubling. One cannot have a pure fermion Regge pole unaccompanied by cuts. This conclusion has important consequences on both fitting data using Regge formulas in, say, backward scattering in boson-fermion scattering and theoretical considerations such as dual bootstrap models
Ponzano-Regge model revisited: I. Gauge fixing, observables and interacting spinning particles
International Nuclear Information System (INIS)
Freidel, Laurent; Louapre, David
2004-01-01
We show how to properly gauge fix all the symmetries of the Ponzano-Regge model for 3D quantum gravity. This amounts to doing explicit finite computations for transition amplitudes. We give the construction of the transition amplitudes in the presence of interacting quantum spinning particles. We introduce a notion of operators whose expectation value gives rise to either gauge fixing, introduction of time, or insertion of particles, according to the choice. We give the link between the spin foam quantization and the Hamiltonian quantization. We finally show the link between the Ponzano-Regge model and the quantization of Chern-Simons theory based on the double quantum group of SU(2)
Uniqueness of Gibbs measure for Potts model with countable set of spin values
International Nuclear Information System (INIS)
Ganikhodjaev, N.N.; Rozikov, U.A.
2004-11-01
We consider a nearest-neighbor Potts model with countable spin values 0,1,..., and non zero external field, on a Cayley tree of order k (with k+1 neighbors). We study translation-invariant 'splitting' Gibbs measures. We reduce the problem to the description of the solutions of some infinite system of equations. For any k≥1 and any fixed probability measure ν with ν(i)>0 on the set of all non negative integer numbers Φ={0,1,...} we show that the set of translation-invariant splitting Gibbs measures contains at most one point, independently on parameters of the Potts model with countable set of spin values on Cayley tree. Also we give a full description of the class of measures ν on Φ such that wit respect to each element of this class our infinite system of equations has unique solution {a i =1,2,...}, where a is an element of (0,1). (author)
Modelling the Earth's Main Magnetic Field by the spinning Astrid-2 satellite
DEFF Research Database (Denmark)
Merayo, Jose Maria Garcia; Jørgensen, Peter Siegbjørn; Risbo, T.
1999-01-01
and therefore the mapping of the Earth's magnetic field may be possible. The spinning of the spacecraft about a certain axis makes the stabilisation in space possible. This fact and the well distributed data over the globe makes the magnetic data well suited for the estimation of the magnetic field model......The Swedish micro-satellite Astrid-2 was successfully launched into a near polar orbit last December 98. Despite the fact that its primary mission was the research of Auroral phenomena, the magnetic instrumentation has been designed to accomplish high resolution vector field magnetic measurements...... at the spacecraft altitude (circa 1000km). Several methods for field modelling are presented in this paper with the assumption that the direction of the spin axis is nearly constant. In any case the orientation of the magnetometer is to bedetermined simultaneously with the instrument calibration and main field...
Quantum influence in the criticality of the spin- {1}/{2} anisotropic Heisenberg model
Ricardo de Sousa, J.; Araújo, Ijanílio G.
1999-07-01
We study the spin- {1}/{2} anisotropic Heisenberg antiferromagnetic model using the effective field renormalization group (EFRG) approach. The EFRG method is illustrated by employing approximations in which clusters with one ( N'=1) and two ( N=2) spins are used. The dependence of the critical temperature Tc (ferromagnetic-F case) and TN (antiferromagnetic-AF case) and thermal critical exponent, Yt, are obtained as a function of anisotropy parameter ( Δ) on a simple cubic lattice. We find that, in our results, TN is higher than Tc for the quantum anisotropic Heisenberg limit and TN= Tc for the Ising and quantum XY limits. We have also shown that the thermal critical exponent Yt for the isotropic Heisenberg model shows a small dependence on the type of interaction (F or AF) due to finite size effects.
Spin model for nontrivial types of magnetic order in inverse-perovskite antiferromagnets
Mochizuki, Masahito; Kobayashi, Masaya; Okabe, Reoya; Yamamoto, Daisuke
2018-02-01
Nontrivial magnetic orders in the inverse-perovskite manganese nitrides are theoretically studied by constructing a classical spin model describing the magnetic anisotropy and frustrated exchange interactions inherent in specific crystal and electronic structures of these materials. With a replica-exchange Monte Carlo technique, a theoretical analysis of this model reproduces the experimentally observed triangular Γ5 g and Γ4 g spin-ordered patterns and the systematic evolution of magnetic orders. Our Rapid Communication solves a 40-year-old problem of nontrivial magnetism for the inverse-perovskite manganese nitrides and provides a firm basis for clarifying the magnetism-driven negative thermal expansion phenomenon discovered in this class of materials.
Rényi Entropies from Random Quenches in Atomic Hubbard and Spin Models
Elben, A.; Vermersch, B.; Dalmonte, M.; Cirac, J. I.; Zoller, P.
2018-02-01
We present a scheme for measuring Rényi entropies in generic atomic Hubbard and spin models using single copies of a quantum state and for partitions in arbitrary spatial dimensions. Our approach is based on the generation of random unitaries from random quenches, implemented using engineered time-dependent disorder potentials, and standard projective measurements, as realized by quantum gas microscopes. By analyzing the properties of the generated unitaries and the role of statistical errors, with respect to the size of the partition, we show that the protocol can be realized in existing quantum simulators and used to measure, for instance, area law scaling of entanglement in two-dimensional spin models or the entanglement growth in many-body localized systems.
Spin and Wind Directions II: A Bell State Quantum Model.
Aerts, Diederik; Arguëlles, Jonito Aerts; Beltran, Lester; Geriente, Suzette; Sassoli de Bianchi, Massimiliano; Sozzo, Sandro; Veloz, Tomas
2018-01-01
In the first half of this two-part article (Aerts et al. in Found Sci. doi:10.1007/s10699-017-9528-9, 2017b), we analyzed a cognitive psychology experiment where participants were asked to select pairs of directions that they considered to be the best example of Two Different Wind Directions , and showed that the data violate the CHSH version of Bell's inequality, with same magnitude as in typical Bell-test experiments in physics. In this second part, we complete our analysis by presenting a symmetrized version of the experiment, still violating the CHSH inequality but now also obeying the marginal law, for which we provide a full quantum modeling in Hilbert space, using a singlet state and suitably chosen product measurements. We also address some of the criticisms that have been recently directed at experiments of this kind, according to which they would not highlight the presence of genuine forms of entanglement. We explain that these criticisms are based on a view of entanglement that is too restrictive, thus unable to capture all possible ways physical and conceptual entities can connect and form systems behaving as a whole. We also provide an example of a mechanical model showing that the violations of the marginal law and Bell inequalities are generally to be associated with different mechanisms.
Modeling of reservoir operation in UNH global hydrological model
Shiklomanov, Alexander; Prusevich, Alexander; Frolking, Steve; Glidden, Stanley; Lammers, Richard; Wisser, Dominik
2015-04-01
Climate is changing and river flow is an integrated characteristic reflecting numerous environmental processes and their changes aggregated over large areas. Anthropogenic impacts on the river flow, however, can significantly exceed the changes associated with climate variability. Besides of irrigation, reservoirs and dams are one of major anthropogenic factor affecting streamflow. They distort hydrological regime of many rivers by trapping of freshwater runoff, modifying timing of river discharge and increasing the evaporation rate. Thus, reservoirs is an integral part of the global hydrological system and their impacts on rivers have to be taken into account for better quantification and understanding of hydrological changes. We developed a new technique, which was incorporated into WBM-TrANS model (Water Balance Model-Transport from Anthropogenic and Natural Systems) to simulate river routing through large reservoirs and natural lakes based on information available from freely accessible databases such as GRanD (the Global Reservoir and Dam database) or NID (National Inventory of Dams for US). Different formulations were applied for unregulated spillway dams and lakes, and for 4 types of regulated reservoirs, which were subdivided based on main purpose including generic (multipurpose), hydropower generation, irrigation and water supply, and flood control. We also incorporated rules for reservoir fill up and draining at the times of construction and decommission based on available data. The model were tested for many reservoirs of different size and types located in various climatic conditions using several gridded meteorological data sets as model input and observed daily and monthly discharge data from GRDC (Global Runoff Data Center), USGS Water Data (US Geological Survey), and UNH archives. The best results with Nash-Sutcliffe model efficiency coefficient in the range of 0.5-0.9 were obtained for temperate zone of Northern Hemisphere where most of large
Theory and modeling of spin-transport on the microscopic and the mesoscopic scale
International Nuclear Information System (INIS)
Stickler, B.
2013-01-01
It is the aim of this thesis to contribute to the description of spin dynamics in solid state systems. In the first part of this work we present a full quantum treatment of spin-coherent transport in halfmetal / semiconductor CrAs / GaAs heterostructures. The theoretical approach is based on the ab-initio determination of the electronic structures of the materials involved and on the calculation of the band offset. These ingredients are in the second step cast into an effective nearest-neighbor tight-binding Hamiltonian. Finally, in the third step, we investigate by means of the non-equilibrium Green's function technique the current which flows through such a heterostructure if a finite bias is applied. With the help of this strategy it is possible to identify CrAs / GaAs heterostructures as probable candidates for all-semiconductor room-temperature spin-filtering devices, which operate without externally applied magnetic fields. In the second part of this thesis we derive a linear semiclassical spinorial Boltzmann equation. For many (mesoscopic) device geometries a full quantum treatment of transport dynamics may not be necessary and may not be feasible with state-of-the-art techniques. The derivation is based on the quantum mechanical description of a composite quantum system by means of von Neumann's equation. The Born-Markov limit allows us to derive a Lindblad master equation for the reduced system plus non-Markovian corrections. Finally, we perform a Wigner transformation and take the semiclassical limit in order to obtain a spinorial Boltzmann equation, suitable for the description of spin transport on the mesoscopic scale. It has to be emphasized that the spinorial Boltzmann equation constitutes the missing link between a full quantum treatment and heuristically introduced mesoscopic models for spin transport in solid state systems. (author) [de
Quantum Gelfand-Levitan equations for nonlinear Schroedinger model of spin-1/2 particles
International Nuclear Information System (INIS)
Pu, F.; Zhao, B.
1984-01-01
The quantum Gelfand-Levitan equations for the nonlinear Schroedinger model of spin-(1/2) particles are obtained. Two Izergin-Korepin relations are used in the derivation. A new type commutation relation of L operators is introduced to get the commutation relations which are needed for the study of S matrices and Green's functions. As examples, the four-point Green's functions and the two-body S matrices are given
Competition between spin, charge, and bond waves in a Peierls-Hubbard model
International Nuclear Information System (INIS)
Venegas, P.A.; Henriquez, C.; Roessler, J.
1996-01-01
We study a one-dimensional extended Peierls-Hubbard model coupled to intracell and intercell phonons for a half-filled band. The calculations are made using the Hartree-Fock and adiabatic approximations for arbitrary temperature. In addition to static spin, charge, and bond density waves, we predict intermediate phases that lack inversion symmetry, and phase transitions that reduce symmetry on increasing temperature. copyright 1996 The American Physical Society
Modelling of Octahedral Manganese II Complexes with Inorganic Ligands: A Problem with Spin-States
Directory of Open Access Journals (Sweden)
Ludwik Adamowicz
2003-08-01
Full Text Available Abstract: Quantum mechanical ab initio UHF, MP2, MC-SCF and DFT calculations with moderate Gaussian basis sets were performed for MnX6, X = H2O, F-, CN-, manganese octahedral complexes. The correct spin-state of the complexes was obtained only when the counter ions neutralizing the entire complexes were used in the modelling at the B3LYP level of theory.
su(1,2) Algebraic Structure of XYZ Antiferromagnetic Model in Linear Spin-Wave Frame
International Nuclear Information System (INIS)
Jin Shuo; Xie Binghao; Yu Zhaoxian; Hou Jingmin
2008-01-01
The XYZ antiferromagnetic model in linear spin-wave frame is shown explicitly to have an su(1,2) algebraic structure: the Hamiltonian can be written as a linear function of the su(1,2) algebra generators. Based on it, the energy eigenvalues are obtained by making use of the similar transformations, and the algebraic diagonalization method is investigated. Some numerical solutions are given, and the results indicate that only one group solution could be accepted in physics
Weyl and transverse diffeomorphism invariant spin-2 models in D = 2 + 1
Energy Technology Data Exchange (ETDEWEB)
Dalmazi, Denis; Mendonca, E.L. [UNESP-Campus de Guaratingueta-DFQ, Guaratingueta, SP (Brazil); ICTP South American Institute for Fundamental Research, IFT-UNESP, Sao Paulo, SP (Brazil); Santos, A.L.R. dos [UNESP-Campus de Guaratingueta-DFQ, Guaratingueta, SP (Brazil); Ghosh, Subir [ICTP South American Institute for Fundamental Research, IFT-UNESP, Sao Paulo, SP (Brazil); Indian Statistical Institute, Physics and Applied Mathematics Unit, Kolkata (India)
2017-09-15
There are two covariant descriptions of massless spin-2 particles in D = 3 + 1 via a symmetric rank-2 tensor: the linearized Einstein-Hilbert (LEH) theory and the Weyl plus transverse diffeomorphism (WTDIFF) invariant model. From the LEH theory one can obtain the linearized new massive gravity (NMG) in D = 2 + 1 via Kaluza-Klein dimensional reduction followed by a dual master action. Here we show that a similar route takes us from the WTDIFF model to a linearized scalar-tensor NMG which belongs to a larger class of consistent spin-0 modifications of NMG. We also show that a traceless master action applied to a parity singlet furnishes two new spin-2 self-dual models. Moreover, we examine the singular replacement h{sub μν} → h{sub μν} - η{sub μν}h/D and prove that it leads to consistent massive spin-2 models in D = 2 + 1. They include linearized versions of unimodular topologically massive gravity (TMG) and unimodular NMG. Although the free part of those unimodular theories are Weyl invariant, we do not expect any improvement in the renormalizability. Both the linearized K-term (in NMG) and the linearized gravitational Chern-Simons term (in TMG) are invariant under longitudinal reparametrizations δh{sub μν} = ∂{sub μ}∂{sub ν}ζ, which is not a symmetry of the WTDIFF Einstein-Hilbert term. Therefore, we still have one degree of freedom whose propagator behaves like 1/p{sup 2} for large momentum. (orig.)
Analytic treatment of nuclear spin-lattice relaxation for diffusion in a cone model
Sitnitsky, A. E.
2011-12-01
We consider nuclear spin-lattice relaxation rate resulted from a diffusion equation for rotational wobbling in a cone. We show that the widespread point of view that there are no analytical expressions for correlation functions for wobbling in a cone model is invalid and prove that nuclear spin-lattice relaxation in this model is exactly tractable and amenable to full analytical description. The mechanism of relaxation is assumed to be due to dipole-dipole interaction of nuclear spins and is treated within the framework of the standard Bloemberger, Purcell, Pound-Solomon scheme. We consider the general case of arbitrary orientation of the cone axis relative the magnetic field. The BPP-Solomon scheme is shown to remain valid for systems with the distribution of the cone axes depending only on the tilt relative the magnetic field but otherwise being isotropic. We consider the case of random isotropic orientation of cone axes relative the magnetic field taking place in powders. Also we consider the cases of their predominant orientation along or opposite the magnetic field and that of their predominant orientation transverse to the magnetic field which may be relevant for, e.g., liquid crystals. Besides we treat in details the model case of the cone axis directed along the magnetic field. The latter provides direct comparison of the limiting case of our formulas with the textbook formulas for free isotropic rotational diffusion. The dependence of the spin-lattice relaxation rate on the cone half-width yields results similar to those predicted by the model-free approach.
Nucleon spin-flavor structure in the SU(3)-breaking chiral quark model
International Nuclear Information System (INIS)
Song, X.; McCarthy, J.S.; Weber, H.J.
1997-01-01
The SU(3) symmetric chiral quark model, which describes interactions between quarks, gluons, and the Goldstone bosons, explains reasonably well many aspects of the flavor and spin structure of the proton, except for the values of f 3 /f 8 and Δ 3 /Δ 8 . Introducing the SU(3)-breaking effect suggested by the mass difference between the strange and nonstrange quarks, we find that this discrepancy can be removed and better overall agreement obtained. copyright 1997 The American Physical Society
Two site spin correlation function in Bethe-Peierls approximation for Ising model
Energy Technology Data Exchange (ETDEWEB)
Kumar, D [Roorkee Univ. (India). Dept. of Physics
1976-07-01
Two site spin correlation function for an Ising model above Curie temperature has been calculated by generalising Bethe-Peierls approximation. The results derived by a graphical method due to Englert are essentially the same as those obtained earlier by Elliott and Marshall, and Oguchi and Ono. The earlier results were obtained by a direct generalisation of the cluster method of Bethe, while these results are derived by retaining that class of diagrams , which is exact on Bethe lattice.
Integer Quantum Magnon Hall Plateau-Plateau Transition in a Spin Ice Model
Xu, Baolong; Ohtsuki, Tomi; Shindou, Ryuichi
2016-01-01
Low-energy magnon bands in a two-dimensional spin ice model become integer quantum magnon Hall bands. By calculating the localization length and the two-terminal conductance of magnon transport, we show that the magnon bands with disorders undergo a quantum phase transition from an integer quantum magnon Hall regime to a conventional magnon localized regime. Finite size scaling analysis as well as a critical conductance distribution shows that the quantum critical point belongs to the same un...
Boundary Layer Studies on a Spinning Tangent-Ogive-Cylinder Model
1975-07-01
ca) An experimental investigation of the Magnus effect on a seven caliber tangent-I ;’ ogive- cylinder model in supersonic flow is reported. The...necessary and Identify by block number) Three-Dimiensional Boundary Layer Compressible Flow Body of Revolution Magnus Effects Boundary Layer...factors have resulted in renewed interest in the study of the Magnus effect . This report describes an experimental study of the effects of spin on
The diluted tri-dimensional spin-one Ising model with crystal field interactions
International Nuclear Information System (INIS)
Saber, M.
1988-09-01
3D spin-one Ising models with nearest-neighbour ferromagnetic interactions with crystal-field exhibit tricritical behaviour. A new method that applies to a wide class of random systems is used to study the influence of site and bond dilution on this behaviour. We have calculated temperature-crystal-field-concentration phase diagrams and determined, in particular, the influence of dilution on the zero temperature tricritical temperature. (author). 10 refs, 8 figs
Improved analysis of GW150914 using a fully spin-precessing waveform model
Abbott, B. P.; Abbott, R.; Adhikari, R. X.; Anderson, S. B.; Arai, K.; Araya, M. C.; Barayoga, J. C.; Barish, B. C.; Berger, B. K.; Billingsley, G.; Blackburn, J. K.; Bork, R.; Brooks, A. F.; Brunett, S.; Cahillane, C.
2016-01-01
This paper presents updated estimates of source parameters for GW150914, a binary black-hole coalescence event detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 [Abbott et al. Phys. Rev. Lett. 116, 061102 (2016).]. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] presented parameter estimation of the source using a 13-dimensional, phenomenological precessing-spin model (precessing IMRPhenom) and an 11-dimensional nonprecessing effective-one-body (EOB) mode...
Elementary isovector spin and orbital magnetic dipole modes revisited in the shell model
International Nuclear Information System (INIS)
Richter, A.
1988-08-01
A review is given on the status of mainly spin magnetic dipole modes in some sd- and fp-shell nuclei studied with inelastic electron and proton scattering, and by β + -decay. Particular emphasis is also placed on a fairly new, mainly orbital magnetic dipole mode investigated by high-resolution (e,e') and (p,p') scattering experiments on a series of fp-shell nuclei. Both modes are discussed in terms of the shell model with various effective interactions. (orig.)
Jordan-Wigner fermionization and the theory of low-dimensional quantum spin models
International Nuclear Information System (INIS)
Derzhko, O.
2007-01-01
The idea of mapping quantum spin lattice model onto fermionic lattice model goes back to Jordan and Wigner (1928) who transformed s = 1/2 operators which commute at different lattice sites into fermionic operators. Later on the Jordan-Wigner transformation was used for mapping one-dimensional s = 1/2 isotropic XY (XX) model onto an exactly solvable tight-binding model of spinless fermions (Lieb, Schultz and Mattis, 1961). Since that times the Jordan-Wigner transformation is known as a powerful tool in the condensed matter theory especially in the theory of low-dimensional quantum spin systems. The aim of these lectures is to review the applications of the Jordan-Wigner fermionization technique for calculating dynamic properties of low-dimensional quantum spin models. The dynamic quantities (such as dynamic structure factors or dynamic susceptibilities) are observable directly or indirectly in various experiments. The frequency and wave-vector dependence of the dynamic quantities yields valuable information about the magnetic structure of materials. Owing to a tremendous recent progress in synthesizing low-dimensional magnetic materials detailed comparisons of theoretical results with direct experimental observation are becoming possible. The lectures are organized as follows. After a brief introduction of the Jordan-Wigner transformation for one-dimensional spin one half systems and some of its extensions for higher dimensions and higher spin values we focus on the dynamic properties of several low-dimensional quantum spin models. We start from a famous s = 1/2 XX chain. As a first step we recall well-known results for dynamics of the z-spin-component fluctuation operator and then turn to dynamics of the dimer and trimer fluctuation operators. The dynamics of the trimer fluctuations involves both the two fermion (one particle and one hole) and the four-fermion (two particles and two holes) excitations. We discuss some properties of the two-fermion and four
Exploring diurnal and seasonal characteristics of global carbon cycle with GISS Model E2 GCM
Aleinov, I. D.; Kiang, N. Y.; Romanou, A.
2017-12-01
The ability to properly model surface carbon fluxes on the diurnal and seasonal time scale is a necessary requirement for understanding of the global carbon cycle. It is also one of the most challenging tasks faced by modern General Circulation Models (GCMs) due to complexity of the algorithms and variety of relevant spatial and temporal scales. The observational data, though abundant, is difficult to interpret at the global scale, because flux tower observations are very sparse for large impact areas (such as Amazon and African rainforest and most of Siberia) and satellite missions often struggle to produce sufficiently high confidence data over the land and may be missing CO2 amounts near the surface due to the nature of the method. In this work we use the GISS Model E2 GCM to perform a subset of experiments proposed by the Coupled Climate-Carbon Cycle Model Intercomparison Project (C4MIP) and relate the results to available observations.The GISS Model E2 GCM is currently equipped with a complete global carbon cycle algorithm. Its surface carbon fluxes are computed by the Ent Terrestrial Biosphere Model (Ent TBM) over the land with observed leaf area index of the Moderate Resolution Imaging Spectrometer (MODIS) and by the NASA Ocean Biogeochemistry Model (NOBM) over the ocean. The propagation of atmospheric CO2 is performed by a generic Model E2 tracer algorithm, which is based on a quadratic upstream method (Prather 1986). We perform a series spin-up experiments for preindustrial climate conditions and fixed preindustrial atmospheric CO2 concentration. First, we perform separate spin-up simulations each for terrestrial and ocean carbon. We then combine the spun-up states and perform a coupled spin-up simulation until the model reaches a sufficient equilibrium. We then release restrictions on CO2 concentration and allow it evolve freely, driven only by simulated surface fluxes. We then study the results of the unforced run, comparing the amplitude and the phase
Analytical solutions for the invariant spin field for model storage rings
International Nuclear Information System (INIS)
Mane, S.R.
2002-01-01
We present nonperturbative analytical expressions for the invariant spin field for several storage ring models. In particular, we solve the important models of a ring with one Snake and a single resonance driving term, and a ring with two Snakes and a single resonance driving term. We also treat several other models, all of which contain Siberian Snakes. Our solutions contain some novel features, e.g. in some cases the polarization does not point along the direction of the closed-orbit spin quantization axis. We also include vertical resonance driving terms, and consider the contributions of sextupoles and higher order multipoles to the resonance driving terms, and argue that these can play a significant role in some circumstances. We offer some brief remarks on the so-called Snake resonances. We relate our results to observations of higher-order depolarizing spin resonances for polarized proton beams in a real ring, and offer some suggestions as to how our ideas might be verified
Virtual walks in spin space: A study in a family of two-parameter models
Mullick, Pratik; Sen, Parongama
2018-05-01
We investigate the dynamics of classical spins mapped as walkers in a virtual "spin" space using a generalized two-parameter family of spin models characterized by parameters y and z [de Oliveira et al., J. Phys. A 26, 2317 (1993), 10.1088/0305-4470/26/10/006]. The behavior of S (x ,t ) , the probability that the walker is at position x at time t , is studied in detail. In general S (x ,t ) ˜t-αf (x /tα) with α ≃1 or 0.5 at large times depending on the parameters. In particular, S (x ,t ) for the point y =1 ,z =0.5 corresponding to the Voter model shows a crossover in time; associated with this crossover, two timescales can be defined which vary with the system size L as L2logL . We also show that as the Voter model point is approached from the disordered regions along different directions, the width of the Gaussian distribution S (x ,t ) diverges in a power law manner with different exponents. For the majority Voter case, the results indicate that the the virtual walk can detect the phase transition perhaps more efficiently compared to other nonequilibrium methods.
Architecture design in global and model-centric software development
Heijstek, Werner
2012-01-01
This doctoral dissertation describes a series of empirical investigations into representation, dissemination and coordination of software architecture design in the context of global software development. A particular focus is placed on model-centric and model-driven software development.
Soliton like excitations on a deformable spin model
International Nuclear Information System (INIS)
Nguenang, Jean-Pierre; Kenfack, Aurelien J.; Kofane, Timoleon C.
2003-07-01
We study numerically non-linear excitations on a one-dimensional deformable discrete classical ferromagnetic chain. In the continuum limits the equations of motion are reduced to a Klein-Gordon equation with a Remoissenet - Peyrard substrate potential. From a numerical computation of the discrete system with a suitable choice of the deformability parameters, the solitons solutions are shown to exist and move both with a monotonic oscillating (i.e. nanopteron) and a monotonic non- oscillating tails and also with a non- oscillating tails but with a splitting propagating shape. The stability of all these various solitons shape is confirmed numerically in a greater range of the reduced magnetic field 0≤b≤0.61 compared to the case of a rigid magnetic chain i.e. 0≤b≤0.33. From a kink- antikink and a kink-kink colliding simulation, we found various effects including a bound state of a kink and an antikink as well as a moving kink profile with higher topological charge that appears to be the bound state of two kinks. We also observed a three particles interaction that also arises from a kink-kink collision. The breather that intercalates between the two kinks has length that varies from its minimal value to the maximal one as far as the alternation between an attractive and a repulsive phenomenon is produced. From our results it appears that the value of the shape parameter of the substrate potential or the modified Zeeman energy is a factor of outmost importance when modelling magnetic chains. (author)
Soliton-like excitations in a deformable spin model
International Nuclear Information System (INIS)
Nguenang, Jean-Pierre; Kenfack, Aurelien J; Kofane, Timoleon C
2004-01-01
Nonlinear excitations in a one-dimensional deformable, discrete, classical, ferromagnetic chain are numerically investigated. In the continuum limit the equations of motion are reduced to a Klein-Gordon equation, with a Remoissenet-Peyrard substrate potential. From a numerical computation of the discrete system with a suitable choice of the deformability parameters, the soliton solutions are shown to exist and move both with a monotonic oscillating (i.e. nanopteron) and a monotonic nonoscillating tail, and also with a non-oscillating tail but with a splitting propagating shape. The stability of all these various soliton shapes is confirmed numerically in a range of the reduced magnetic fields greater than for a rigid magnetic chain i.e. 0 ≤ b ≤0.33. From a kink-antikink and a kink-kink colliding simulation, we found various effects, including a bound state of a kink and an antikink, as well as a moving kink profile with higher topological charge that appears to be the bound state of two kinks. For some values of the deformability parameter, with a suitable choice of the initial velocity, we observed that the presence of an internal mode leads to the combination of an attractive and a repulsive phenomenon, that arises when the kink-kink collision is engaged. The fact that this collision happens only in the centre of the magnetic chain with the presence of a minimal distance between the two kinks as long as the collision is produced is also a feature of the deformability effect in the dynamics of a magnetic chain. From our results, it appears that the value of the shape parameter of the substrate potential or the modified Zeeman energy is a factor of utmost importance when modelling magnetic chains
Climatology of the HOPE-G global ocean general circulation model - Sea ice general circulation model
Energy Technology Data Exchange (ETDEWEB)
Legutke, S. [Deutsches Klimarechenzentrum (DKRZ), Hamburg (Germany); Maier-Reimer, E. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany)
1999-12-01
The HOPE-G global ocean general circulation model (OGCM) climatology, obtained in a long-term forced integration is described. HOPE-G is a primitive-equation z-level ocean model which contains a dynamic-thermodynamic sea-ice model. It is formulated on a 2.8 grid with increased resolution in low latitudes in order to better resolve equatorial dynamics. The vertical resolution is 20 layers. The purpose of the integration was both to investigate the models ability to reproduce the observed general circulation of the world ocean and to obtain an initial state for coupled atmosphere - ocean - sea-ice climate simulations. The model was driven with daily mean data of a 15-year integration of the atmosphere general circulation model ECHAM4, the atmospheric component in later coupled runs. Thereby, a maximum of the flux variability that is expected to appear in coupled simulations is included already in the ocean spin-up experiment described here. The model was run for more than 2000 years until a quasi-steady state was achieved. It reproduces the major current systems and the main features of the so-called conveyor belt circulation. The observed distribution of water masses is reproduced reasonably well, although with a saline bias in the intermediate water masses and a warm bias in the deep and bottom water of the Atlantic and Indian Oceans. The model underestimates the meridional transport of heat in the Atlantic Ocean. The simulated heat transport in the other basins, though, is in good agreement with observations. (orig.)
New Approaches For Asteroid Spin State and Shape Modeling From Delay-Doppler Radar Images
Raissi, Chedy; Lamee, Mehdi; Mosiane, Olorato; Vassallo, Corinne; Busch, Michael W.; Greenberg, Adam; Benner, Lance A. M.; Naidu, Shantanu P.; Duong, Nicholas
2016-10-01
Delay-Doppler radar imaging is a powerful technique to characterize the trajectories, shapes, and spin states of near-Earth asteroids; and has yielded detailed models of dozens of objects. Reconstructing objects' shapes and spins from delay-Doppler data is a computationally intensive inversion problem. Since the 1990s, delay-Doppler data has been analyzed using the SHAPE software. SHAPE performs sequential single-parameter fitting, and requires considerable computer runtime and human intervention (Hudson 1993, Magri et al. 2007). Recently, multiple-parameter fitting algorithms have been shown to more efficiently invert delay-Doppler datasets (Greenberg & Margot 2015) - decreasing runtime while improving accuracy. However, extensive human oversight of the shape modeling process is still required. We have explored two new techniques to better automate delay-Doppler shape modeling: Bayesian optimization and a machine-learning neural network.One of the most time-intensive steps of the shape modeling process is to perform a grid search to constrain the target's spin state. We have implemented a Bayesian optimization routine that uses SHAPE to autonomously search the space of spin-state parameters. To test the efficacy of this technique, we compared it to results with human-guided SHAPE for asteroids 1992 UY4, 2000 RS11, and 2008 EV5. Bayesian optimization yielded similar spin state constraints within a factor of 3 less computer runtime.The shape modeling process could be further accelerated using a deep neural network to replace iterative fitting. We have implemented a neural network with a variational autoencoder (VAE), using a subset of known asteroid shapes and a large set of synthetic radar images as inputs to train the network. Conditioning the VAE in this manner allows the user to give the network a set of radar images and get a 3D shape model as an output. Additional development will be required to train a network to reliably render shapes from delay
Mixed-order phase transition in a minimal, diffusion-based spin model.
Fronczak, Agata; Fronczak, Piotr
2016-07-01
In this paper we exactly solve, within the grand canonical ensemble, a minimal spin model with the hybrid phase transition. We call the model diffusion based because its Hamiltonian can be recovered from a simple dynamic procedure, which can be seen as an equilibrium statistical mechanics representation of a biased random walk. We outline the derivation of the phase diagram of the model, in which the triple point has the hallmarks of the hybrid transition: discontinuity in the average magnetization and algebraically diverging susceptibilities. At this point, two second-order transition curves meet in equilibrium with the first-order curve, resulting in a prototypical mixed-order behavior.
Panda, Saswati; Sahoo, D. D.; Rout, G. C.
2018-04-01
We report here a tight binding model for colossal magnetoresistive (CMR) manganites to study the pseudo gap (PG) behavior near Fermi level. In the Kubo-Ohata type DE model, we consider first and second nearest neighbor interactions for transverse spin fluctuations in core band and hopping integrals in conduction band, in the presence of static band Jahn-Teller distortion. The model Hamiltonian is solved using Zubarev's Green's function technique. The electron density of states (DOS) is found out from the Green's functions. We observe clear PG near Fermi level in the electron DOS.
Entangled spins and ghost-spins
Directory of Open Access Journals (Sweden)
Dileep P. Jatkar
2017-09-01
Full Text Available We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple quantum mechanical toy models for theories containing negative norm states. We define a single ghost-spin as in [20] as a 2-state spin variable with an indefinite inner product in the state space. We find that whenever the spin sector is disentangled from the ghost-spin sector (both of which could be entangled within themselves, the reduced density matrix obtained by tracing over all the ghost-spins gives rise to positive entanglement entropy for positive norm states, while negative norm states have an entanglement entropy with a negative real part and a constant imaginary part. However when the spins are entangled with the ghost-spins, there are new entanglement patterns in general. For systems where the number of ghost-spins is even, it is possible to find subsectors of the Hilbert space where positive norm states always lead to positive entanglement entropy after tracing over the ghost-spins. With an odd number of ghost-spins however, we find that there always exist positive norm states with negative real part for entanglement entropy after tracing over the ghost-spins.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Xiaojun; Tung, Chang-Shung; Sowa, Glenna; Hatmal, Ma' mon M.; Haworth, Ian S.; Qin, Peter Z.
2012-02-08
The condensation of bacteriophage phi29 genomic DNA into its preformed procapsid requires the DNA packaging motor, which is the strongest known biological motor. The packaging motor is an intricate ring-shaped protein/RNA complex, and its function requires an RNA component called packaging RNA (pRNA). Current structural information on pRNA is limited, which hinders studies of motor function. Here, we used site-directed spin labeling to map the conformation of a pRNA three-way junction that bridges binding sites for the motor ATPase and the procapsid. The studies were carried out on a pRNA dimer, which is the simplest ring-shaped pRNA complex and serves as a functional intermediate during motor assembly. Using a nucleotide-independent labeling scheme, stable nitroxide radicals were attached to eight specific pRNA sites without perturbing RNA folding and dimer formation, and a total of 17 internitroxide distances spanning the three-way junction were measured using Double Electron-Electron Resonance spectroscopy. The measured distances, together with steric chemical constraints, were used to select 3662 viable three-way junction models from a pool of 65 billion. The results reveal a similar conformation among the viable models, with two of the helices (HT and HL) adopting an acute bend. This is in contrast to a recently reported pRNA tetramer crystal structure, in which HT and HL stack onto each other linearly. The studies establish a new method for mapping global structures of complex RNA molecules, and provide information on pRNA conformation that aids investigations of phi29 packaging motor and developments of pRNA-based nanomedicine and nanomaterial.
Modeling the Global Workplace Using Emerging Technologies
Dorazio, Patricia; Hickok, Corey
2008-01-01
The Fall 2006 term of COM495, Senior Practicum in Communication, offered communication and information design students the privilege of taking part in a transatlantic intercultural virtual project. To emulate real world experience in today's global workplace, these students researched and completed a business communication project with German…
Modelling global container freight transport demand
Tavasszy, L.A.; Ivanova, O.; Halim, R.A.
2015-01-01
The objective of this chapter is to discuss methods and techniques for a quantitative and descriptive analysis of future container transport demand at a global level. Information on future container transport flows is useful for various purposes. It is instrumental for the assessment of returns of
International Nuclear Information System (INIS)
Uma, V.S.; Goel, Alpana; Yadav, Archana; Jain, A.K.
2016-01-01
The band-head spin (I 0 ) of superdeformed (SD) rotational bands in A ∼ 190 mass region is predicted using the variable moment of inertia (VMI) model for 66 SD rotational bands. The superdeformed rotational bands exhibited considerably good rotational property and rigid behaviour. The transition energies were dependent on the prescribed band-head spins. The ratio of transition energies over spin Eγ/ 2 I (RTEOS) vs. angular momentum (I) have confirmed the rigid behaviour, provided the band-head spin value is assigned correctly. There is a good agreement between the calculated and the observed transition energies. This method gives a very comprehensive interpretation for spin assignment of SD rotational bands which could help in designing future experiments for SD bands. (author)
Bodily tides near the 1:1 spin-orbit resonance: correction to Goldreich's dynamical model
Williams, James G.; Efroimsky, Michael
2012-12-01
Spin-orbit coupling is often described in an approach known as " the MacDonald torque", which has long become the textbook standard due to its apparent simplicity. Within this method, a concise expression for the additional tidal potential, derived by MacDonald (Rev Geophys 2:467-541, 1994), is combined with a convenient assumption that the quality factor Q is frequency-independent (or, equivalently, that the geometric lag angle is constant in time). This makes the treatment unphysical because MacDonald's derivation of the said formula was, very implicitly, based on keeping the time lag frequency-independent, which is equivalent to setting Q scale as the inverse tidal frequency. This contradiction requires the entire MacDonald treatment of both non-resonant and resonant rotation to be rewritten. The non-resonant case was reconsidered by Efroimsky and Williams (Cel Mech Dyn Astron 104:257-289, 2009), in application to spin modes distant from the major commensurabilities. In the current paper, we continue this work by introducing the necessary alterations into the MacDonald-torque-based model of falling into a 1-to-1 resonance. (The original version of this model was offered by Goldreich (Astron J 71:1-7, 1996). Although the MacDonald torque, both in its original formulation and in its corrected version, is incompatible with realistic rheologies of minerals and mantles, it remains a useful toy model, which enables one to obtain, in some situations, qualitatively meaningful results without resorting to the more rigorous (and complicated) theory of Darwin and Kaula. We first address this simplified model in application to an oblate primary body, with tides raised on it by an orbiting zero-inclination secondary. (Here the role of the tidally-perturbed primary can be played by a satellite, the perturbing secondary being its host planet. A planet may as well be the perturbed primary, its host star acting as the tide-raising secondary). We then extend the model to a
Silva, João Paulo Santos; Mônaco, Luciana da Mata; Paschoal, André Monteiro; Oliveira, Ícaro Agenor Ferreira de; Leoni, Renata Ferranti
2018-05-16
Arterial spin labeling (ASL) is an established magnetic resonance imaging (MRI) technique that is finding broader applications in functional studies of the healthy and diseased brain. To promote improvement in cerebral blood flow (CBF) signal specificity, many algorithms and imaging procedures, such as subtraction methods, were proposed to eliminate or, at least, minimize noise sources. Therefore, this study addressed the main considerations of how CBF functional connectivity (FC) is changed, regarding resting brain network (RBN) identification and correlations between regions of interest (ROI), by different subtraction methods and removal of residual motion artifacts and global signal fluctuations (RMAGSF). Twenty young healthy participants (13 M/7F, mean age = 25 ± 3 years) underwent an MRI protocol with a pseudo-continuous ASL (pCASL) sequence. Perfusion-based images were obtained using simple, sinc and running subtraction. RMAGSF removal was applied to all CBF time series. Independent Component Analysis (ICA) was used for RBN identification, while Pearson' correlation was performed for ROI-based FC analysis. Temporal signal-to-noise ratio (tSNR) was higher in CBF maps obtained by sinc subtraction, although RMAGSF removal had a significant effect on maps obtained with simple and running subtractions. Neither the subtraction method nor the RMAGSF removal directly affected the identification of RBNs. However, the number of correlated and anti-correlated voxels varied for different subtraction and filtering methods. In an ROI-to-ROI level, changes were prominent in FC values and their statistical significance. Our study showed that both RMAGSF filtering and subtraction method might influence resting-state FC results, especially in an ROI level, consequently affecting FC analysis and its interpretation. Taking our results and the whole discussion together, we understand that for an exploratory assessment of the brain, one could avoid removing RMAGSF to
Stuhne-Sekalec, L; Stanacev, N Z
1977-02-01
Several spin-labelled phospholipids carrying covalently bound 5-doxylstearic acid (2-(3-carboxydecyl)-2-hexyl-4,4-dimethyl-3-oxazolidinoxyl) were intercalated in liposomes of saturated and unsaturated lecithins. Temperature-induced changes of these liposomes, detected by the spin-labelled phospholipids, were found to be in agreement with the previously described transitions of hydrocarbon chains of host lecithins detected by different probes and different techniques, establishing that spin-labelled phosopholipids are sensitive probes for the detection of temperature-induced changes in lecithin model membranes. In addition to the detection of already-known transitions in lecithin liposomes, the coexistence of two distinctly different enviroments was observed above the characteristic transition temperature. This phenomenon was tentatively attributed to the influence of the lecithin polar group on the fluidity of fatty acyl chains near the polar group. Combined with other results from the literature, the coexistence of two environments could be associated with the coexistence of two conformational isomers of lecithin, differing in the orientation of the polar head group with respect to the plane of bilayer. These findings have been discussed in view of the present state of knowledge regarding temperature-induced changes in model membranes.
Dynamical correlation functions of the quadratic coupling spin-Boson model
Zheng, Da-Chuan; Tong, Ning-Hua
2017-06-01
The spin-boson model with quadratic coupling is studied using the bosonic numerical renormalization group method. We focus on the dynamical auto-correlation functions {C}O(ω ), with the operator \\hat{O} taken as {\\hat{{{σ }}}}x, {\\hat{{{σ }}}}z, and \\hat{X}, respectively. In the weak-coupling regime α qualitatively, showing enhanced dephasing at the spin flip point. Project supported by the National Key Basic Research Program of China (Grant No. 2012CB921704), the National Natural Science Foundation of China (Grant No. 11374362), the Fundamental Research Funds for the Central Universities, China, and the Research Funds of Renmin University of China (Grant No. 15XNLQ03).
Quantum state transfer via a two-qubit Heisenberg XXZ spin model
Energy Technology Data Exchange (ETDEWEB)
Liu Jia; Zhang Guofeng [Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China); Chen Ziyu [Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)], E-mail: chenzy@buaa.edu.cn
2008-04-14
Transfer of quantum states through a two-qubit Heisenberg XXZ spin model with a nonuniform magnetic field b is investigated by means of quantum theory. The influences of b, the spin exchange coupling J and the effective transfer time T=Jt on the fidelity have been studied for some different initial states. Results show that fidelity of the transferred state is determined not only by J, T and b but also by the initial state of this quantum system. Ideal information transfer can be realized for some kinds of initial states. We also found that the interactions of the z-component J{sub z} and uniform magnetic field B do not have any contribution to the fidelity. These results may be useful for quantum information processing.
Quantum state transfer via a two-qubit Heisenberg XXZ spin model
International Nuclear Information System (INIS)
Liu Jia; Zhang Guofeng; Chen Ziyu
2008-01-01
Transfer of quantum states through a two-qubit Heisenberg XXZ spin model with a nonuniform magnetic field b is investigated by means of quantum theory. The influences of b, the spin exchange coupling J and the effective transfer time T=Jt on the fidelity have been studied for some different initial states. Results show that fidelity of the transferred state is determined not only by J, T and b but also by the initial state of this quantum system. Ideal information transfer can be realized for some kinds of initial states. We also found that the interactions of the z-component J z and uniform magnetic field B do not have any contribution to the fidelity. These results may be useful for quantum information processing
Pini, Maria Gloria; Rettori, Angelo
1993-08-01
The thermodynamical properties of an alternating spin (S,s) one-dimensional (1D) Ising model with competing nearest- and next-nearest-neighbor interactions are exactly calculated using a transfer-matrix technique. In contrast to the case S=s=1/2, previously investigated by Harada, the alternation of different spins (S≠s) along the chain is found to give rise to two-peaked static structure factors, signaling the coexistence of different short-range-order configurations. The relevance of our calculations with regard to recent experimental data by Gatteschi et al. in quasi-1D molecular magnetic materials, R (hfac)3 NITEt (R=Gd, Tb, Dy, Ho, Er, . . .), is discussed; hfac is hexafluoro-acetylacetonate and NlTEt is 2-Ethyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxide.
Adiabatically modeling quantum gates with two-site Heisenberg spins chain: Noise vs interferometry
Jipdi, M. N.; Tchoffo, M.; Fai, L. C.
2018-02-01
We study the Landau Zener (LZ) dynamics of a two-site Heisenberg spin chain assisted with noise and focus on the implementation of logic gates via the resulting quantum interference. We present the evidence of the quantum interference phenomenon in triplet spin states and confirm that, three-level systems mimic Landau-Zener-Stückelberg (LZS) interferometers with occupancies dependent on the effective phase. It emerges that, the critical parameters tailoring the system are obtained for constructive interferences where the two sets of the chain are found to be maximally entangled. Our findings demonstrate that the enhancement of the magnetic field strength suppresses noise effects; consequently, the noise severely impacts the occurrence of quantum interference for weak magnetic fields while for strong fields, quantum interference subsists and allows the modeling of universal sets of quantum gates.
Software package for modeling spin-orbit motion in storage rings
Zyuzin, D. V.
2015-12-01
A software package providing a graphical user interface for computer experiments on the motion of charged particle beams in accelerators, as well as analysis of obtained data, is presented. The software package was tested in the framework of the international project on electric dipole moment measurement JEDI (Jülich Electric Dipole moment Investigations). The specific features of particle spin motion imply the requirement to use a cyclic accelerator (storage ring) consisting of electrostatic elements, which makes it possible to preserve horizontal polarization for a long time. Computer experiments study the dynamics of 106-109 particles in a beam during 109 turns in an accelerator (about 1012-1015 integration steps for the equations of motion). For designing an optimal accelerator structure, a large number of computer experiments on polarized beam dynamics are required. The numerical core of the package is COSY Infinity, a program for modeling spin-orbit dynamics.
Tricritical behavior in the diluted transverse spin-1 Ising model with a longitudinal crystal field
International Nuclear Information System (INIS)
Htoutou, K.; Oubelkacem, A.; Ainane, A.; Saber, M.
2005-01-01
The transverse spin-1 Ising model with a longitudinal crystal field exhibits a tricritical behavior. Within the effective field theory with a probability distribution technique that accounts for the self-spin correlations, we have studied the influence of site dilution on this behavior and have calculated the temperature-transverse field-longitudinal crystal field-concentration phase diagrams and determined, in particular, the influence of the concentration of magnetic atoms c on the tricritical behavior. We have found that the tricritical point appears for large values of the concentration c of magnetic atoms and disappears with the increase in dilution (small values of c). Results for square lattice are calculated numerically and some interesting results are obtained. In certain ranges of values of the strength of the longitudinal crystal field D/J when it becomes sufficiently negative, we found re-entrant phenomenon, which disappears with increase in the value of the strength of the transverse field
Nonplanar spiral states of the t-J model with classical spins
International Nuclear Information System (INIS)
Hamada, M.; Shimahara, H.; Mori, H.
1995-01-01
The spiral state in the two-dimensional t-J model is studied by numerical diagonalization of an effective Hamiltonian. We examine all possibilities of the spiral spin states including the nonplanar states. It is found that nonplanar spiral states occur, but the deviations from the planar spiral state in the nonplanar spiral states are small for small hole concentrations where our effective Hamiltonian is valid. The modulation of the spin configuration increases continuously from the antiferromagnetic order as the hole concentration increases, and discontinuously changes at a critical hole concentration. Then the state undergoes the first-order phase transition either to the (π,0) phase or to the ferromagnetic phase, depending on the value of J/t
Valence bond solids for SU(n) spin chains: Exact models, spinon confinement, and the Haldane gap
International Nuclear Information System (INIS)
Greiter, Martin; Rachel, Stephan
2007-01-01
To begin with, we introduce several exact models for SU(3) spin chains: First is a translationally invariant parent Hamiltonian involving four-site interactions for the trimer chain, with a threefold degenerate ground state. We provide numerical evidence that the elementary excitations of this model transform under representation 3 of SU(3) if the original spins of the model transform under representation 3. Second is a family of parent Hamiltonians for valence bond solids of SU(3) chains with spin representations 6, 10, and 8 on each lattice site. We argue that of these three models, only the latter two exhibit spinon confinement and, hence, a Haldane gap in the excitation spectrum. We generalize some of our models to SU(n). Finally, we use the emerging rules for the construction of valence bond solid states to argue that models of antiferromagnetic chains of SU(n) spins, in general, possess a Haldane gap if the spins transform under a representation corresponding to a Young tableau consisting of a number of boxes λ which is divisible by n. If λ and n have no common divisor, the spin chain will support deconfined spinons and not exhibit a Haldane gap. If λ and n have a common divisor different from n, it will depend on the specifics of the model including the range of the interaction
Booth, B. B. B.; Bernie, D.; McNeall, D.; Hawkins, E.; Caesar, J.; Boulton, C.; Friedlingstein, P.; Sexton, D.
2012-09-01
We compare future changes in global mean temperature in response to different future scenarios which, for the first time, arise from emission driven rather than concentration driven perturbed parameter ensemble of a Global Climate Model (GCM). These new GCM simulations sample uncertainties in atmospheric feedbacks, land carbon cycle, ocean physics and aerosol sulphur cycle processes. We find broader ranges of projected temperature responses arising when considering emission rather than concentration driven simulations (with 10-90 percentile ranges of 1.7 K for the aggressive mitigation scenario up to 3.9 K for the high end business as usual scenario). A small minority of simulations resulting from combinations of strong atmospheric feedbacks and carbon cycle responses show temperature increases in excess of 9 degrees (RCP8.5) and even under aggressive mitigation (RCP2.6) temperatures in excess of 4 K. While the simulations point to much larger temperature ranges for emission driven experiments, they do not change existing expectations (based on previous concentration driven experiments) on the timescale that different sources of uncertainty are important. The new simulations sample a range of future atmospheric concentrations for each emission scenario. Both in case of SRES A1B and the Representative Concentration Pathways (RCPs), the concentration pathways used to drive GCM ensembles lies towards the lower end of our simulated distribution. This design decision (a legecy of previous assessments) is likely to lead concentration driven experiments to under-sample strong feedback responses in concentration driven projections. Our ensemble of emission driven simulations span the global temperature response of other multi-model frameworks except at the low end, where combinations of low climate sensitivity and low carbon cycle feedbacks lead to responses outside our ensemble range. The ensemble simulates a number of high end responses which lie above the CMIP5 carbon
USING GEM - GLOBAL ECONOMIC MODEL IN ACHIEVING A GLOBAL ECONOMIC FORECAST
Directory of Open Access Journals (Sweden)
Camelia Madalina Orac
2013-12-01
Full Text Available The global economic development model has proved to be insufficiently reliable under the new economic crisis. As a result, the entire theoretical construction about the global economy needs rethinking and reorientation. In this context, it is quite clear that only through effective use of specific techniques and tools of economic-mathematical modeling, statistics, regional analysis and economic forecasting it is possible to obtain an overview of the future economy.
SPICE modelling of magnetic tunnel junctions written by spin-transfer torque
Energy Technology Data Exchange (ETDEWEB)
Guo, W; Prenat, G; De Mestier, N; Baraduc, C; Dieny, B [SPINTEC, UMR(8191), INAC, CEA/CNRS/UJF, 17 Av. des Martyrs, 38054 Grenoble Cedex 9 (France); Javerliac, V; El Baraji, M, E-mail: guillaume.prenat@cea.f [CROCUS Technology, 5 Place Robert Schuman, 38025 Grenoble (France)
2010-06-02
Spintronics aims at extending the possibility of conventional electronics by using not only the charge of the electron but also its spin. The resulting spintronic devices, combining the front-end complementary metal oxide semiconductor technology of electronics with a magnetic back-end technology, employ magnetic tunnel junctions (MTJs) as core elements. With the intent of simulating a circuit without fabricating it first, a reliable MTJ electrical model which is applicable to the standard SPICE (Simulation Program with Integrated Circuit Emphasis) simulator is required. Since such a model was lacking so far, we present a MTJ SPICE model whose magnetic state is written by using the spin-transfer torque effect. This model has been developed in the C language and validated on the Cadence Virtuoso Platform with a Spectre simulator. Its operation is similar to that of the standard BSIM (Berkeley Short-channel IGFET Model) SPICE model of the MOS transistor and fully compatible with the SPICE electrical simulator. The simulation results obtained using this model have been found in good accord with those theoretical macrospin calculations and results.
Directory of Open Access Journals (Sweden)
Hyein Lim
2013-01-01
Full Text Available Spin-torque oscillator (STO is a promising new technology for the future RF oscillators, which is based on the spin-transfer torque (STT effect in magnetic multilayered nanostructure. It is expected to provide a larger tunability, smaller size, lower power consumption, and higher level of integration than the semiconductor-based oscillators. In our previous work, a circuit-level model of the giant magnetoresistance (GMR STO was proposed. In this paper, we present a physics-based circuit-level model of the magnetic tunnel junction (MTJ-based STO. MTJ-STO model includes the effect of perpendicular torque that has been ignored in the GMR-STO model. The variations of three major characteristics, generation frequency, mean oscillation power, and generation linewidth of an MTJ-STO with respect to the amount of perpendicular torque, are investigated, and the results are applied to our model. The operation of the model was verified by HSPICE simulation, and the results show an excellent agreement with the experimental data. The results also prove that a full circuit-level simulation with MJT-STO devices can be made with our proposed model.
Directory of Open Access Journals (Sweden)
Héctor Torres-Silva
2008-11-01
Full Text Available The quantum relationship may be regarded as the equivalence between two expressions for the rest energy of the particle, if is considered as the spin angular velocity of the particle in its rest frame. The invariance of the relativistic space-time interval to such a spin motion (space isotropy leads to the spin momentum for all structureless particles irrespective of their mass values. The inertia is an intrinsic property due to the spin motion of the particles. The signs of the mass values occurring in the solutions of the Dirac equation might be related to the orientation of the spin motion, as suggested by the fundamental relationship . Besides it deals with the electron, and more specifically with two key properties: its complex wavefunction, and its intrinsic spin. In the standard interpretation, there is no clear real-space picture of what is oscillating in the wave, or what is rotating in the spin. Indeed, it is generally believed that no simple model of rotation can account for the spin of the electron. On the contrary, the present paper shows that a crude mechanical model of coherently rotating vortices can account quantitatively not only for spin, but also for the wavefunction itself. The implications of this are discussed in this paper.La relación cuántica puede ser considerada como la equivalencia entre dos expresiones para la energía en reposo de la partícula, si se considera la velocidad angular de giro de partículas en su marco en reposo. La invariancia del intervalo relativista espacio- tiempo para tal movimiento de espín (isotropía espacial conduce al impulso de espín para todas las partículas sin estructura, independientemente de sus valores de masa. La inercia es una propiedad intrínseca debido al movimiento de spin de las partículas. Los signos de los valores de masa que se producen en las soluciones de la ecuación de Dirac podrían estar relacionados con la orientación del espín, según lo sugerido por la
Global spatiotemporal distribution of soil respiration modeled using a global database
Hashimoto, S.; Carvalhais, N.; Ito, A.; Migliavacca, M.; Nishina, K.; Reichstein, M.
2015-07-01
The flux of carbon dioxide from the soil to the atmosphere (soil respiration) is one of the major fluxes in the global carbon cycle. At present, the accumulated field observation data cover a wide range of geographical locations and climate conditions. However, there are still large uncertainties in the magnitude and spatiotemporal variation of global soil respiration. Using a global soil respiration data set, we developed a climate-driven model of soil respiration by modifying and updating Raich's model, and the global spatiotemporal distribution of soil respiration was examined using this model. The model was applied at a spatial resolution of 0.5°and a monthly time step. Soil respiration was divided into the heterotrophic and autotrophic components of respiration using an empirical model. The estimated mean annual global soil respiration was 91 Pg C yr-1 (between 1965 and 2012; Monte Carlo 95 % confidence interval: 87-95 Pg C yr-1) and increased at the rate of 0.09 Pg C yr-2. The contribution of soil respiration from boreal regions to the total increase in global soil respiration was on the same order of magnitude as that of tropical and temperate regions, despite a lower absolute magnitude of soil respiration in boreal regions. The estimated annual global heterotrophic respiration and global autotrophic respiration were 51 and 40 Pg C yr-1, respectively. The global soil respiration responded to the increase in air temperature at the rate of 3.3 Pg C yr-1 °C-1, and Q10 = 1.4. Our study scaled up observed soil respiration values from field measurements to estimate global soil respiration and provide a data-oriented estimate of global soil respiration. The estimates are based on a semi-empirical model parameterized with over one thousand data points. Our analysis indicates that the climate controls on soil respiration may translate into an increasing trend in global soil respiration and our analysis emphasizes the relevance of the soil carbon flux from soil to
New Temperature-based Models for Predicting Global Solar Radiation
International Nuclear Information System (INIS)
Hassan, Gasser E.; Youssef, M. Elsayed; Mohamed, Zahraa E.; Ali, Mohamed A.; Hanafy, Ahmed A.
2016-01-01
Highlights: • New temperature-based models for estimating solar radiation are investigated. • The models are validated against 20-years measured data of global solar radiation. • The new temperature-based model shows the best performance for coastal sites. • The new temperature-based model is more accurate than the sunshine-based models. • The new model is highly applicable with weather temperature forecast techniques. - Abstract: This study presents new ambient-temperature-based models for estimating global solar radiation as alternatives to the widely used sunshine-based models owing to the unavailability of sunshine data at all locations around the world. Seventeen new temperature-based models are established, validated and compared with other three models proposed in the literature (the Annandale, Allen and Goodin models) to estimate the monthly average daily global solar radiation on a horizontal surface. These models are developed using a 20-year measured dataset of global solar radiation for the case study location (Lat. 30°51′N and long. 29°34′E), and then, the general formulae of the newly suggested models are examined for ten different locations around Egypt. Moreover, the local formulae for the models are established and validated for two coastal locations where the general formulae give inaccurate predictions. Mostly common statistical errors are utilized to evaluate the performance of these models and identify the most accurate model. The obtained results show that the local formula for the most accurate new model provides good predictions for global solar radiation at different locations, especially at coastal sites. Moreover, the local and general formulas of the most accurate temperature-based model also perform better than the two most accurate sunshine-based models from the literature. The quick and accurate estimations of the global solar radiation using this approach can be employed in the design and evaluation of performance for
An effective correlated mean-field theory applied in the spin-1/2 Ising ferromagnetic model
Energy Technology Data Exchange (ETDEWEB)
Roberto Viana, J.; Salmon, Octávio R. [Universidade Federal do Amazonas – UFAM, Manaus 69077-000, AM (Brazil); Ricardo de Sousa, J. [Universidade Federal do Amazonas – UFAM, Manaus 69077-000, AM (Brazil); National Institute of Science and Technology for Complex Systems, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Neto, Minos A.; Padilha, Igor T. [Universidade Federal do Amazonas – UFAM, Manaus 69077-000, AM (Brazil)
2014-11-15
We developed a new treatment for mean-field theory applied in spins systems, denominated effective correlated mean-field (ECMF). We apply this theory to study the spin-1/2 Ising ferromagnetic model with nearest-neighbor interactions on a square lattice. We use clusters of finite sizes and study the criticality of the ferromagnetic system, where we obtain a convergence of critical temperature for the value k{sub B}T{sub c}/J≃2.27905±0.00141. Also the behavior of magnetic and thermodynamic properties, using the condition of minimum energy of the physical system is obtained. - Highlights: • We developed spin models to study real magnetic systems. • We study the thermodynamic and magnetic properties of the ferromagnetism. • We enhanced a mean-field theory applied in spins models.
Evaluation of global climate models for Indian monsoon climatology
International Nuclear Information System (INIS)
Kodra, Evan; Ganguly, Auroop R; Ghosh, Subimal
2012-01-01
The viability of global climate models for forecasting the Indian monsoon is explored. Evaluation and intercomparison of model skills are employed to assess the reliability of individual models and to guide model selection strategies. Two dominant and unique patterns of Indian monsoon climatology are trends in maximum temperature and periodicity in total rainfall observed after 30 yr averaging over India. An examination of seven models and their ensembles reveals that no single model or model selection strategy outperforms the rest. The single-best model for the periodicity of Indian monsoon rainfall is the only model that captures a low-frequency natural climate oscillator thought to dictate the periodicity. The trend in maximum temperature, which most models are thought to handle relatively better, is best captured through a multimodel average compared to individual models. The results suggest a need to carefully evaluate individual models and model combinations, in addition to physical drivers where possible, for regional projections from global climate models. (letter)
Replica analysis of partition-function zeros in spin-glass models
International Nuclear Information System (INIS)
Takahashi, Kazutaka
2011-01-01
We study the partition-function zeros in mean-field spin-glass models. We show that the replica method is useful to find the locations of zeros in a complex parameter plane. For the random energy model, we obtain the phase diagram in the plane and find that there are two types of distributions of zeros: two-dimensional distribution within a phase and one-dimensional one on a phase boundary. Phases with a two-dimensional distribution are characterized by a novel order parameter defined in the present replica analysis. We also discuss possible patterns of distributions by studying several systems.
Multicritical phase diagrams of the antiferromagnetic spin-3/2 Blume-Capel model
Energy Technology Data Exchange (ETDEWEB)
Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)]. E-mail: keskin@erciyes.edu.tr; Ali Pinar, M. [Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Erdinc, Ahmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Canko, Osman [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)
2006-04-24
The antiferromagnetic spin-3/2 Blume-Capel model in an external magnetic field is investigated, and the phase diagrams are obtained in detail by using the cluster variation method. The model exhibits distinct critical regions, including the first-order, second-order and special points: two double critical points, a critical end point, a tricritical point and a zero-temperature critical point. The new phase diagram topology is also found that was not obtained previously. Comparison of the results with those of other studies on this, and closely related systems, is made.
Multicritical phase diagrams of the antiferromagnetic spin-3/2 Blume-Capel model
International Nuclear Information System (INIS)
Keskin, Mustafa; Ali Pinar, M.; Erdinc, Ahmet; Canko, Osman
2006-01-01
The antiferromagnetic spin-3/2 Blume-Capel model in an external magnetic field is investigated, and the phase diagrams are obtained in detail by using the cluster variation method. The model exhibits distinct critical regions, including the first-order, second-order and special points: two double critical points, a critical end point, a tricritical point and a zero-temperature critical point. The new phase diagram topology is also found that was not obtained previously. Comparison of the results with those of other studies on this, and closely related systems, is made
A Simple Model of Global Aerosol Indirect Effects
Ghan, Steven J.; Smith, Steven J.; Wang, Minghuai; Zhang, Kai; Pringle, Kirsty; Carslaw, Kenneth; Pierce, Jeffrey; Bauer, Susanne; Adams, Peter
2013-01-01
Most estimates of the global mean indirect effect of anthropogenic aerosol on the Earth's energy balance are from simulations by global models of the aerosol lifecycle coupled with global models of clouds and the hydrologic cycle. Extremely simple models have been developed for integrated assessment models, but lack the flexibility to distinguish between primary and secondary sources of aerosol. Here a simple but more physically based model expresses the aerosol indirect effect (AIE) using analytic representations of cloud and aerosol distributions and processes. Although the simple model is able to produce estimates of AIEs that are comparable to those from some global aerosol models using the same global mean aerosol properties, the estimates by the simple model are sensitive to preindustrial cloud condensation nuclei concentration, preindustrial accumulation mode radius, width of the accumulation mode, size of primary particles, cloud thickness, primary and secondary anthropogenic emissions, the fraction of the secondary anthropogenic emissions that accumulates on the coarse mode, the fraction of the secondary mass that forms new particles, and the sensitivity of liquid water path to droplet number concentration. Estimates of present-day AIEs as low as 5 W/sq m and as high as 0.3 W/sq m are obtained for plausible sets of parameter values. Estimates are surprisingly linear in emissions. The estimates depend on parameter values in ways that are consistent with results from detailed global aerosol-climate simulation models, which adds to understanding of the dependence on AIE uncertainty on uncertainty in parameter values.
Modeling the hyperfine state selectivity of a short lamb-shift spin-filter polarimeter
International Nuclear Information System (INIS)
Mendez, A.J.; Roper, C.D.; Clegg, T.B.
1995-01-01
An rf cavity, previously used as a spin filter in a Lamb-shift polarized ion source, is being adapted for use as a polarimeter in an atomic beam polarized hydrogen and deuterium ion source. Paramount among the design criteria is maintaining the current source performance while providing on-line beam polarization monitoring. This requires minimizing both the polarimeter system length and the coupling with the magnetic fields of the other ion source systems. Detailed computer calculations have modeled the four-level interaction involving the 2S 1/2 -2P 1/2 states of the atomic beam. These indicate that a significantly shorter spin-filter cavity and uniform axial magnetic field than used in the Lamb-shift source do not compromise the spin-state selectivity. The calculations also predict the axial magnetic field uniformity needed as well as the gains achieved from proper shaping of the cavity rf and dc fields. copyright 1995 American Institute of Physics
Thermodynamic curvature for a two-parameter spin model with frustration.
Ruppeiner, George; Bellucci, Stefano
2015-01-01
Microscopic models of realistic thermodynamic systems usually involve a number of parameters, not all of equal macroscopic relevance. We examine a decorated (1+3) Ising spin chain containing two microscopic parameters: a stiff parameter K mediating the long-range interactions, and a sloppy J operating within local spin groups. We show that K dominates the macroscopic behavior, with varying J having only a weak effect, except in regions where J brings about transitions between phases through its conditioning of the local spin groups with which K interacts. We calculate the heat capacity C(H), the magnetic susceptibility χ(T), and the thermodynamic curvature R. For large |J/K|, we identify four magnetic phases: ferromagnetic, antiferromagnetic, and two ferrimagnetic, according to the signs of K and J. We argue that for characterizing these phases, the strongest picture is offered by the thermodynamic geometric invariant R, proportional to the correlation length ξ. This picture has correspondences to other cases, such as fluids.
Study of spin crossover nanoparticles thermal hysteresis using FORC diagrams on an Ising-like model
International Nuclear Information System (INIS)
Atitoaie, Alexandru; Tanasa, Radu; Stancu, Alexandru; Enachescu, Cristian
2014-01-01
Recent developments in the synthesis and characterization of spin crossover (SCO) nanoparticles and their prospects of switching at molecular level turned these bistable compounds into possible candidates for replacing the materials used in recording media industry for development of solid state pressure and temperature sensors or for bringing contributions in engineering. Compared to bulk samples with the same chemical structure, SCO nanoparticles display different characteristics of the hysteretic and relaxation properties like the shift of the transition temperature towards lower values along with decrease of the hysteresis width with nanoparticles size. Using an Ising-like model with specific boundary conditions within a Monte Carlo procedure, we here reproduce most of the hysteretic properties of SCO nanoparticles by considering the interaction between spin crossover edge molecules and embedding surfactant molecules and we propose a complex analysis concerning the effect of the interactions and sizes during the thermal transition in systems of SCO nanoparticles by using the First Order Reversal Curves diagram method and by comparison with similar effects in mixed crystal systems. - Highlights: • The influence of size effects in spin crossover nanoparticles is analyzed. • The environment shifts the hysteresis loop towards lower temperatures. • First Order Reversal Curves technique is employed. • One determines the distributions of switching temperatures. • One disentangles between kinetics and non-kinetic parts of the hysteresis
Lee, Henry A.
1952-01-01
An investigation has been conducted in the Langley 20-foot free-spinning tunnel on a l/20-scale model of the Consolidated Vultee XFY-1 airplane with a windmilling propeller simulated to determine the effects of control setting and movements upon the erect spin and recovery characteristics for a range of airplane-loading conditions. The effects on the model's spin-recovery characteristics of removing the lower vertical tail, removing the gun pods, and fixing the rudders at neutral were also investigated briefly. The investigation included determination of the size parachute required for emergency recovery from demonstration spins. The tumbling tendencies of the model were also investigated. Brief static force tests were made to determine the aerodynamic characteristics in pitch at high angles of attack. The investigation indicated that the spin and recovery characteristics of the airplane with propeller windmilling will be satisfactory for all loading conditions if recovery is attempted by full rudder reversal accompanied by simultaneous movement of the stick laterally to full with the spin (stick right in a right spin) and longitudinally to neutral. Inverted spins should be satisfactorily terminated by fully reversing the rudder followed immediately by moving the stick laterally towards the forward rudder pedal and longitudinally to neutral. Removal of the gun pods or fixing the rudders at neutral will not adversely affect the airplane's spin-recovery characteristics, but removal of the lower vertical tail will result in unsatisfactory spin-recovery characteristics. The model-test results showed that a 13.3-foot wing-tip conventional parachute (drag coefficient approximately 0.7) should be effective as an emergency spin-recovery device during demonstration spins of the airplane. It was indicated that the airplane should not tumble and that no unusual longitudinal-trim characteristics should be obtained for the center-of-gravity positions investigated.
Field Modeling, Symplectic Tracking, and Spin Decoherence for EDM and Muon $g\\textrm{-}2$ Lattices
Energy Technology Data Exchange (ETDEWEB)
Valetov, Eremey Vladimirovich [Michigan State U.
2017-01-01
While the first particle accelerators were electrostatic machines, and several electrostatic storage rings were subsequently commissioned and operated, electrostatic storage rings pose a number of challenges. Unlike motion in the magnetic field, where particle energy remains constant, particle energy generally changes in electrostatic elements. Conservation of energy in an electrostatic element is, in practice, only approximate, and it requires careful and accurate design, manufacturing, installation, and operational use. Electrostatic deflectors require relatively high electrostatic fields, tend to introduce nonlinear aberrations of all orders, and are more challenging to manufacture than homogeneous magnetic dipoles. Accordingly, magnetic storage rings are overwhelmingly prevalent. The search for electric dipole moments (EDMs) of fundamental particles is of key importance in the study of C and CP violations and their sources. C and CP violations are part of the Sakharov conditions that explain the matter–antimatter asymmetry in the universe. Determining the source of CP violations would provide valuable empirical insight for beyond-Standard-Model physics. EDMs of fundamental particles have not to this date been experimentally observed. The search for fundamental particle EDMs has narrowed the target search region; however, an EDM signal is yet to be discovered. In 2008, Brookhaven National Laboratory (BNL) had proposed the frozen spin (FS) concept for the search of a deuteron EDM. The FS concept envisions launching deuterons through a storage ring with combined electrostatic and magnetic fields. The electrostatic and magnetic fields are in a proportion that would, without an EDM, freeze the deuteron’s spin along its momentum as the deuteron moves around the lattice. The radial electrostatic field would result in a torque on the spin vector, proportional to a deuteron EDM, rotating the spin vector out of the midplane.
Global qualitative analysis of a quartic ecological model
Broer, Hendrik; Gaiko, Valery A.
2010-01-01
in this paper we complete the global qualitative analysis of a quartic ecological model. In particular, studying global bifurcations of singular points and limit cycles, we prove that the corresponding dynamical system has at most two limit cycles. (C) 2009 Elsevier Ltd. All rights reserved.
Existence of global attractor for the Trojan Y Chromosome model
Directory of Open Access Journals (Sweden)
Xiaopeng Zhao
2012-04-01
Full Text Available This paper is concerned with the long time behavior of solution for the equation derived by the Trojan Y Chromosome (TYC model with spatial spread. Based on the regularity estimates for the semigroups and the classical existence theorem of global attractors, we prove that this equations possesses a global attractor in $H^k(\\Omega^4$ $(k\\geq 0$ space.
Models for prediction of global solar radiation on horizontal surface ...
African Journals Online (AJOL)
The estimation of global solar radiation continues to play a fundamental role in solar engineering systems and applications. This paper compares various models for estimating the average monthly global solar radiation on horizontal surface for Akure, Nigeria, using solar radiation and sunshine duration data covering years ...
OILMAP: A global approach to spill modeling
International Nuclear Information System (INIS)
Spaulding, M.L.; Howlett, E.; Anderson, E.; Jayko, K.
1992-01-01
OILMAP is an oil spill model system suitable for use in both rapid response mode and long-range contingency planning. It was developed for a personal computer and employs full-color graphics to enter data, set up spill scenarios, and view model predictions. The major components of OILMAP include environmental data entry and viewing capabilities, the oil spill models, and model prediction display capabilities. Graphic routines are provided for entering wind data, currents, and any type of geographically referenced data. Several modes of the spill model are available. The surface trajectory mode is intended for quick spill response. The weathering model includes the spreading, evaporation, entrainment, emulsification, and shoreline interaction of oil. The stochastic and receptor models simulate a large number of trajectories from a single site for generating probability statistics. Each model and the algorithms they use are described. Several additional capabilities are planned for OILMAP, including simulation of tactical spill response and subsurface oil transport. 8 refs
Kar, J. K.; Panda, Saswati; Rout, G. C.
2017-05-01
We propose here a tight binding model study of the interplay between charge and spin orderings in the CMR manganites taking anisotropic effect due to electron hoppings and spin exchanges. The Hamiltonian consists of the kinetic energies of eg and t2g electrons of manganese ion. It further includes double exchange and Heisenberg interactions. The charge density wave interaction (CDW) describes an extra mechanism for the insulating character of the system. The CDW gap and spin parameters are calculated using Zubarev's Green's function technique and computed self-consistently. The results are reported in this communication.
Greiter, Martin
2011-01-01
This monograph introduces an exact model for a critical spin chain with arbitrary spin S, which includes the Haldane--Shastry model as the special case S=1/2. While spinons in the Haldane-Shastry model obey abelian half-fermi statistics, the spinons in the general model introduced here obey non-abelian statistics. This manifests itself through topological choices for the fractional momentum spacings. The general model is derived by mapping exact models of quantized Hall states onto spin chains. The book begins with pedagogical review of all the relevant models including the non-abelian statistics in the Pfaffian Hall state, and is understandable to every student with a graduate course in quantum mechanics.
Kontturi, E.J.; Thuene, P.C.; Niemantsverdriet, J.W.
2003-01-01
Spin coating is introduced as a simplified method to prep. model surfaces of cellulose. Prior to spin coating, trimethylsilyl cellulose (TMSC), a nonpolar deriv. of cellulose, is synthesized in order to dissolve the otherwise immiscible cellulose. After the spin coating deposition of TMSC on an
Ajami, Hoori
2014-03-01
Integrated land surface-groundwater models are valuable tools in simulating the terrestrial hydrologic cycle as a continuous system and exploring the extent of land surface-subsurface interactions from catchment to regional scales. However, the fidelity of model simulations is impacted not only by the vegetation and subsurface parameterizations, but also by the antecedent condition of model state variables, such as the initial soil moisture, depth to groundwater, and ground temperature. In land surface modeling, a given model is often run repeatedly over a single year of forcing data until it reaches an equilibrium state: the point at which there is minimal artificial drift in the model state or prognostic variables (most often the soil moisture). For more complex coupled and integrated systems, where there is an increased computational cost of simulation and the number of variables sensitive to initialization is greater than in traditional uncoupled land surface modeling schemes, the challenge is to minimize the impact of initialization while using the smallest spin-up time possible. In this study, multicriteria analysis was performed to assess the spin-up behavior of the ParFlow.CLM integrated groundwater-surface water-land surface model over a 208 km2 subcatchment of the Ringkobing Fjord catchment in Denmark. Various measures of spin-up performance were computed for model state variables such as the soil moisture and groundwater storage, as well as for diagnostic variables such as the latent and sensible heat fluxes. The impacts of initial conditions on surface water-groundwater interactions were then explored. Our analysis illustrates that the determination of an equilibrium state depends strongly on the variable and performance measure used. Choosing an improper initialization of the model can generate simulations that lead to a misinterpretation of land surface-subsurface feedback processes and result in large biases in simulated discharge. Estimated spin
Global Atmosphere Watch Workshop on Measurement-Model ...
The World Meteorological Organization’s (WMO) Global Atmosphere Watch (GAW) Programme coordinates high-quality observations of atmospheric composition from global to local scales with the aim to drive high-quality and high-impact science while co-producing a new generation of products and services. In line with this vision, GAW’s Scientific Advisory Group for Total Atmospheric Deposition (SAG-TAD) has a mandate to produce global maps of wet, dry and total atmospheric deposition for important atmospheric chemicals to enable research into biogeochemical cycles and assessments of ecosystem and human health effects. The most suitable scientific approach for this activity is the emerging technique of measurement-model fusion for total atmospheric deposition. This technique requires global-scale measurements of atmospheric trace gases, particles, precipitation composition and precipitation depth, as well as predictions of the same from global/regional chemical transport models. The fusion of measurement and model results requires data assimilation and mapping techniques. The objective of the GAW Workshop on Measurement-Model Fusion for Global Total Atmospheric Deposition (MMF-GTAD), an initiative of the SAG-TAD, was to review the state-of-the-science and explore the feasibility and methodology of producing, on a routine retrospective basis, global maps of atmospheric gas and aerosol concentrations as well as wet, dry and total deposition via measurement-model
Magnetization plateaus in the spin-1/2 antiferromagnetic Heisenberg model on a kagome-strip chain
Morita, Katsuhiro; Sugimoto, Takanori; Sota, Shigetoshi; Tohyama, Takami
2018-01-01
The spin-1/2 Heisenberg model on a kagome lattice is a typical frustrated quantum spin system. The basic structure of a kagome lattice is also present in the kagome-strip lattice in one dimension, where a similar type of frustration is expected. We thus study the magnetization plateaus of the spin-1/2 Heisenberg model on a kagome-strip chain with three-independent antiferromagnetic exchange interactions using the density-matrix renormalization-group method. In a certain range of exchange parameters, we find twelve kinds of magnetization plateaus, nine of which have magnetic structures breaking translational and/or reflection symmetry spontaneously. The structures are classified by an array of five-site unit cells with specific bond-spin correlations. In a case with a nontrivial plateau, namely a 3/10 plateau, we find long-period magnetic structure with a period of four unit cells.
Spin foam model for pure gauge theory coupled to quantum gravity
International Nuclear Information System (INIS)
Oriti, Daniele; Pfeiffer, Hendryk
2002-01-01
We propose a spin foam model for pure gauge fields coupled to Riemannian quantum gravity in four dimensions. The model is formulated for the triangulation of a four-manifold which is given merely combinatorially. The Riemannian Barrett-Crane model provides the gravity sector of our model and dynamically assigns geometric data to the given combinatorial triangulation. The gauge theory sector is a lattice gauge theory living on the same triangulation and obtains from the gravity sector the geometric information which is required to calculate the Yang-Mills action. The model is designed so that one obtains a continuum approximation of the gauge theory sector at an effective level, similarly to the continuum limit of lattice gauge theory, when the typical length scale of gravity is much smaller than the Yang-Mills scale
Assessment of Global Forecast Ocean Assimilation Model (FOAM) using new satellite SST data
Ascione Kenov, Isabella; Sykes, Peter; Fiedler, Emma; McConnell, Niall; Ryan, Andrew; Maksymczuk, Jan
2016-04-01
There is an increased demand for accurate ocean weather information for applications in the field of marine safety and navigation, water quality, offshore commercial operations, monitoring of oil spills and pollutants, among others. The Met Office, UK, provides ocean forecasts to customers from governmental, commercial and ecological sectors using the Global Forecast Ocean Assimilation Model (FOAM), an operational modelling system which covers the global ocean and runs daily, using the NEMO (Nucleus for European Modelling of the Ocean) ocean model with horizontal resolution of 1/4° and 75 vertical levels. The system assimilates salinity and temperature profiles, sea surface temperature (SST), sea surface height (SSH), and sea ice concentration observations on a daily basis. In this study, the FOAM system is updated to assimilate Advanced Microwave Scanning Radiometer 2 (AMSR2) and the Spinning Enhanced Visible and Infrared Imager (SEVIRI) SST data. Model results from one month trials are assessed against observations using verification tools which provide a quantitative description of model performance and error, based on statistical metrics, including mean error, root mean square error (RMSE), correlation coefficient, and Taylor diagrams. A series of hindcast experiments is used to run the FOAM system with AMSR2 and SEVIRI SST data, using a control run for comparison. Results show that all trials perform well on the global ocean and that largest SST mean errors were found in the Southern hemisphere. The geographic distribution of the model error for SST and temperature profiles are discussed using statistical metrics evaluated over sub-regions of the global ocean.
Spin Current Noise of the Spin Seebeck Effect and Spin Pumping
Matsuo, M.; Ohnuma, Y.; Kato, T.; Maekawa, S.
2018-01-01
We theoretically investigate the fluctuation of a pure spin current induced by the spin Seebeck effect and spin pumping in a normal-metal-(NM-)ferromagnet(FM) bilayer system. Starting with a simple ferromagnet-insulator-(FI-)NM interface model with both spin-conserving and non-spin-conserving processes, we derive general expressions of the spin current and the spin-current noise at the interface within second-order perturbation of the FI-NM coupling strength, and estimate them for a yttrium-iron-garnet-platinum interface. We show that the spin-current noise can be used to determine the effective spin carried by a magnon modified by the non-spin-conserving process at the interface. In addition, we show that it provides information on the effective spin of a magnon, heating at the interface under spin pumping, and spin Hall angle of the NM.
Spin dynamics modeling in the AGS based on a stepwise ray-tracing method
Energy Technology Data Exchange (ETDEWEB)
Dutheil, Yann [Univ. of Grenoble (France)
2006-08-07
The AGS provides a polarized proton beam to RHIC. The beam is accelerated in the AGS from Gγ= 4.5 to Gγ = 45.5 and the polarization transmission is critical to the RHIC spin program. In the recent years, various systems were implemented to improve the AGS polarization transmission. These upgrades include the double partial snakes configuration and the tune jumps system. However, 100% polarization transmission through the AGS acceleration cycle is not yet reached. The current efficiency of the polarization transmission is estimated to be around 85% in typical running conditions. Understanding the sources of depolarization in the AGS is critical to improve the AGS polarized proton performances. The complexity of beam and spin dynamics, which is in part due to the specialized Siberian snake magnets, drove a strong interest for original methods of simulations. For that, the Zgoubi code, capable of direct particle and spin tracking through field maps, was here used to model the AGS. A model of the AGS using the Zgoubi code was developed and interfaced with the current system through a simple command: the AgsFromSnapRampCmd. Interfacing with the machine control system allows for fast modelization using actual machine parameters. Those developments allowed the model to realistically reproduce the optics of the AGS along the acceleration ramp. Additional developments on the Zgoubi code, as well as on post-processing and pre-processing tools, granted long term multiturn beam tracking capabilities: the tracking of realistic beams along the complete AGS acceleration cycle. Beam multiturn tracking simulations in the AGS, using realistic beam and machine parameters, provided a unique insight into the mechanisms behind the evolution of the beam emittance and polarization during the acceleration cycle. Post-processing softwares were developed to allow the representation of the relevant quantities from the Zgoubi simulations data. The Zgoubi simulations proved particularly
Modeling the Acceleration of Global Surface Temperture
Jones, B.
2017-12-01
A mathematical projection focusing on the changing rate of acceleration of Global Surface Temperatures. Using historical trajectory and informed expert near-term prediction, it is possible to extend this further forward drawing a reference arc of acceleration. Presented here is an example of this technique based on data found in the Summary of Findings of A New Estimate of the Average Earth Surface Land Temperature Spanning 1753 to 2011 and that same team's stated prediction to 2050. With this, we can project a curve showing future acceleration: Decade (midpoint) Change in Global Land Temp Degrees C Known Slope Projected Trend 1755 0.000 1955 0.600 0.0030 2005 1.500 0.0051 2045 3.000 0.0375 2095 5.485 0.0497 2145 8.895 0.0682 2195 13.488 0.0919 Observations: Slopes are getting steeper and doing so faster in an "acceleration of the acceleration" or an "arc of acceleration". This is consistent with the non-linear accelerating feedback loops of global warming. Such projected temperatures threaten human civilization and human life. This `thumbnail' projection is consistent with the other long term predictions based on anthropogenic greenhouse gases. This projection is low when compared to those whose forecasts include greenhouse gases released from thawing permafrost and clathrate hydrates. A reference line: This curve should be considered a point of reference. In the near term and absent significant drawdown of greenhouse gases, my "bet" for this AGU session is that future temperatures will generally be above this reference curve. For example, the decade ending 2020 - more than 1.9C and the decade ending 2030 - more than 2.3C - again measured from the 1750 start point. *Caveat: The long term curve and prediction assumes that mankind does not move quickly away from high cost fossil fuels and does not invent, mobilize and take actions drawing down greenhouse gases. Those seeking a comprehensive action plan are directed to drawdown.org
Numerical Simulation of Hydrogen Combustion: Global Reaction Model and Validation
Energy Technology Data Exchange (ETDEWEB)
Zhang, Yun [School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an (China); Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY (United States); Liu, Yinhe, E-mail: yinheliu@mail.xjtu.edu.cn [School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an (China)
2017-11-20
Due to the complexity of modeling the combustion process in nuclear power plants, the global mechanisms are preferred for numerical simulation. To quickly perform the highly resolved simulations with limited processing resources of large-scale hydrogen combustion, a method based on thermal theory was developed to obtain kinetic parameters of global reaction mechanism of hydrogen–air combustion in a wide range. The calculated kinetic parameters at lower hydrogen concentration (C{sub hydrogen} < 20%) were validated against the results obtained from experimental measurements in a container and combustion test facility. In addition, the numerical data by the global mechanism (C{sub hydrogen} > 20%) were compared with the results by detailed mechanism. Good agreement between the model prediction and the experimental data was achieved, and the comparison between simulation results by the detailed mechanism and the global reaction mechanism show that the present calculated global mechanism has excellent predictable capabilities for a wide range of hydrogen–air mixtures.
Numerical Simulation of Hydrogen Combustion: Global Reaction Model and Validation
International Nuclear Information System (INIS)
Zhang, Yun; Liu, Yinhe
2017-01-01
Due to the complexity of modeling the combustion process in nuclear power plants, the global mechanisms are preferred for numerical simulation. To quickly perform the highly resolved simulations with limited processing resources of large-scale hydrogen combustion, a method based on thermal theory was developed to obtain kinetic parameters of global reaction mechanism of hydrogen–air combustion in a wide range. The calculated kinetic parameters at lower hydrogen concentration (C hydrogen < 20%) were validated against the results obtained from experimental measurements in a container and combustion test facility. In addition, the numerical data by the global mechanism (C hydrogen > 20%) were compared with the results by detailed mechanism. Good agreement between the model prediction and the experimental data was achieved, and the comparison between simulation results by the detailed mechanism and the global reaction mechanism show that the present calculated global mechanism has excellent predictable capabilities for a wide range of hydrogen–air mixtures.
Energy Technology Data Exchange (ETDEWEB)
Varela, M.
2001-07-01
The process of introduction of a new technology supposes that while its production and utilisation increases, also its operation improves and its investment costs and production decreases. The accumulation of experience and learning of a new technology increase in parallel with the increase of its market share. This process is represented by the technological learning curves and the energy sector is not detached from this process of substitution of old technologies by new ones. The present paper carries out a brief revision of the main energy models that include the technology dynamics (learning). The energy scenarios, developed by global energy models, assume that the characteristics of the technologies are variables with time. But this tend is incorporated in a exogenous way in these energy models, that is to say, it is only a time function. This practice is applied to the cost indicators of the technology such as the specific investment costs or to the efficiency of the energy technologies. In the last years, the new concept of endogenous technological learning has been integrated within these global energy models. This paper examines the concept of technological learning in global energy models. It also analyses the technological dynamics of the energy systems including the endogenous modelling of the process of technological progress. Finally, it makes a comparison of several of the most used global energy models (MARKAL, MESSAGE and ERIS) and, more concretely, about the use these models make of the concept of technological learning. (Author) 17 refs.
Global Nonlinear Model Identification with Multivariate Splines
De Visser, C.C.
2011-01-01
At present, model based control systems play an essential role in many aspects of modern society. Application areas of model based control systems range from food processing to medical imaging, and from process control in oil refineries to the flight control systems of modern aircraft. Central to a
Fourier series models through transformation | Omekara | Global ...
African Journals Online (AJOL)
As a result, the square transformation which outperforms the others is adopted. Consequently, each of the multiplicative and additive FSA models fitted to the transformed data are then subjected to a test for white noise based on spectral analysis. The result of this test shows that only the multiplicative model is adequate.
Bowman, James S., Jr.
1955-01-01
An investigation is being conducted in the Langley 20-foot free-spinning tunnel on a 1/24-scale model of the Grumman F11F-1 airplane to determine spin and recovery characteristics and the minimum-size parachute required to satisfactorily terminate the spin in an emergency. Results obtained to date are presented herein. Test results indicate that it may be difficult to obtain an erect or inverted spin on the airplane, but, if a spin is obtained, the spin will be very oscillatory and recovery from the developed erect spin by rudder reversal may not be possible. The lateral controls will have no appreciable effect on recoveries from erect.spins. Recovery from the inverted spin by merely neutralizing the rudder will be satisfactory. After recoveries by rudder reversal and after recoveries from spins without control movement (no spins), the model oftentimes rolled very rapidly about the X-axis. Based on limited preliminary tests made in this investigation to make the model recover satisfactorily, it appears that canards near the nose of the airplane or differentially operated horizontal tails may be utilized to provide rapid recoveries. The parachute test results indicate that an 11-foot-diameter (laid-out-flat) parachute with a drag coefficient of 0.650 (based on the laid- out-flat diameter) and with a towline length equal to the wing span is the minimum-size parachute required to satisfactorily terminate an erect or inverted spin in an emergency.
Modeling global distribution of agricultural insecticides in surface waters
International Nuclear Information System (INIS)
Ippolito, Alessio; Kattwinkel, Mira; Rasmussen, Jes J.; Schäfer, Ralf B.; Fornaroli, Riccardo; Liess, Matthias
2015-01-01
Agricultural insecticides constitute a major driver of animal biodiversity loss in freshwater ecosystems. However, the global extent of their effects and the spatial extent of exposure remain largely unknown. We applied a spatially explicit model to estimate the potential for agricultural insecticide runoff into streams. Water bodies within 40% of the global land surface were at risk of insecticide runoff. We separated the influence of natural factors and variables under human control determining insecticide runoff. In the northern hemisphere, insecticide runoff presented a latitudinal gradient mainly driven by insecticide application rate; in the southern hemisphere, a combination of daily rainfall intensity, terrain slope, agricultural intensity and insecticide application rate determined the process. The model predicted the upper limit of observed insecticide exposure measured in water bodies (n = 82) in five different countries reasonably well. The study provides a global map of hotspots for insecticide contamination guiding future freshwater management and conservation efforts. - Highlights: • First global map on insecticide runoff through modelling. • Model predicts upper limit of insecticide exposure when compared to field data. • Water bodies in 40% of global land surface may be at risk of adverse effects. • Insecticide application rate, terrain slope and rainfall main drivers of exposure. - We provide the first global map on insecticide runoff to surface water predicting that water bodies in 40% of global land surface may be at risk of adverse effects
Usefulness and limitations of global flood risk models
Ward, Philip; Jongman, Brenden; Salamon, Peter; Simpson, Alanna; Bates, Paul; De Groeve, Tom; Muis, Sanne; Coughlan de Perez, Erin; Rudari, Roberto; Mark, Trigg; Winsemius, Hessel
2016-04-01
Global flood risk models are now a reality. Initially, their development was driven by a demand from users for first-order global assessments to identify risk hotspots. Relentless upward trends in flood damage over the last decade have enhanced interest in such assessments. The adoption of the Sendai Framework for Disaster Risk Reduction and the Warsaw International Mechanism for Loss and Damage Associated with Climate Change Impacts have made these efforts even more essential. As a result, global flood risk models are being used more and more in practice, by an increasingly large number of practitioners and decision-makers. However, they clearly have their limits compared to local models. To address these issues, a team of scientists and practitioners recently came together at the Global Flood Partnership meeting to critically assess the question 'What can('t) we do with global flood risk models?'. The results of this dialogue (Ward et al., 2013) will be presented, opening a discussion on similar broader initiatives at the science-policy interface in other natural hazards. In this contribution, examples are provided of successful applications of global flood risk models in practice (for example together with the World Bank, Red Cross, and UNISDR), and limitations and gaps between user 'wish-lists' and model capabilities are discussed. Finally, a research agenda is presented for addressing these limitations and reducing the gaps. Ward et al., 2015. Nature Climate Change, doi:10.1038/nclimate2742
An inversion-relaxation approach for sampling stationary points of spin model Hamiltonians
International Nuclear Information System (INIS)
Hughes, Ciaran; Mehta, Dhagash; Wales, David J.
2014-01-01
Sampling the stationary points of a complicated potential energy landscape is a challenging problem. Here, we introduce a sampling method based on relaxation from stationary points of the highest index of the Hessian matrix. We illustrate how this approach can find all the stationary points for potentials or Hamiltonians bounded from above, which includes a large class of important spin models, and we show that it is far more efficient than previous methods. For potentials unbounded from above, the relaxation part of the method is still efficient in finding minima and transition states, which are usually the primary focus of attention for atomistic systems
Relativistic wave functions of two spin 1/2 quarks in a model with QCD interaction
International Nuclear Information System (INIS)
Skachkov, N.B.; Solovtsov, I.L.
1981-01-01
Within the hamiltonian formulation of quantum field theory an equation is obtained for the vertex and wave functions of a composite system of two spin 1/2 quarks. Exact solutions are found for the relativistic potential having in the momentum representation the ''asymptotically-free'' behaviour at large values of momentum transfer Q 2 . It is shown that within the given model the π-meson wave function has zero at a finite distance corresponding to the point of discontinuity of the effective potential [ru
Heat transfer in the spin-boson model: a comparative study in the incoherent tunneling regime.
Segal, Dvira
2014-07-01
We study the transfer of heat in the nonequilibrium spin-boson model with an Ohmic dissipation. In the nonadiabatic limit we derive a formula for the thermal conductance based on a rate equation formalism at the level of the noninteracting blip approximation, valid for temperatures T>T(K), with T(K) as the Kondo temperature. We evaluate this expression analytically assuming either weak or strong couplings, and demonstrate that our results agree with exact relations. Far-from-equilibrium situations are further examined, showing a close correspondence to the linear response limit.
Volume simplicity constraint in the Engle-Livine-Pereira-Rovelli spin foam model
Bahr, Benjamin; Belov, Vadim
2018-04-01
We propose a quantum version of the quadratic volume simplicity constraint for the Engle-Livine-Pereira-Rovelli spin foam model. It relies on a formula for the volume of 4-dimensional polyhedra, depending on its bivectors and the knotting class of its boundary graph. While this leads to no further condition for the 4-simplex, the constraint becomes nontrivial for more complicated boundary graphs. We show that, in the semiclassical limit of the hypercuboidal graph, the constraint turns into the geometricity condition observed recently by several authors.
KN phase shifts in a model with a spin-orbit interaction
International Nuclear Information System (INIS)
Lemaire, S.; Labarsouque, J.; Silvestre-Brac, B.
2001-01-01
The I=1 and I=0 kaon-nucleon s, p, d, f, g-waves phase shifts have been calculated in a non relativistic quark potential model using the resonating group method (RGM). The interquark potential includes gluon exchanges with a spin-orbit interaction. This force was determined to reproduce as well as possible the meson and baryon spectra. The same force is employed for the cluster and intercluster dynamics and the relative KN wave function is calculated without any approximation. While some channels are correctly described, the theory is still unable to explain others
Entanglement Properties of a Higher-Integer-Spin AKLT Model with Quantum Group Symmetry
Directory of Open Access Journals (Sweden)
Chikashi Arita
2012-10-01
Full Text Available We study the entanglement properties of a higher-integer-spin Affleck-Kennedy-Lieb-Tasaki model with quantum group symmetry in the periodic boundary condition. We exactly calculate the finite size correction terms of the entanglement entropies from the double scaling limit. We also evaluate the geometric entanglement, which serves as another measure for entanglement. We find the geometric entanglement reaches its maximum at the isotropic point, and decreases with the increase of the anisotropy. This behavior is similar to that of the entanglement entropies.
Minimal spin-3/2 dark matter in a simple s-channel model
Energy Technology Data Exchange (ETDEWEB)
Khojali, Mohammed Omer; Goyal, Ashok; Kumar, Mukesh; Cornell, Alan S. [University of the Witwatersrand, Wits, National Institute for Theoretical Physics, School of Physics and Mandelstam Institute for Theoretical Physics, Johannesburg (South Africa)
2017-01-15
We consider a spin-3/2 fermionic dark matter candidate (DM) interacting with Standard Model fermions through a vector mediator in the s-channel. We find that for pure vector couplings almost the entire parameter space of the DM and mediator mass consistent with the observed relic density is ruled out by the direct detection observations through DM-nucleon elastic scattering cross sections. In contrast, for pure axial-vector coupling, the most stringent constraints are obtained from monojet searches at the Large Hadron Collider. (orig.)
Globalizing High-Tech Business Models
DEFF Research Database (Denmark)
Turcan, Romeo V.
2012-01-01
resources and behavioral patterns. Two sources could be identified that effect these tensions, namely strategic experimentation and business model experimentation. For example, entrepreneurs are trying to ease the tensions in the organizational gestalt as a result of a change in the business model...... and growth path. To internationalize, international new ventures have to develop a product-led business model as services do not travel. Opting to attract venture capital, entrepreneurs are to deal with dyadic tensions that are the result of differences in entrepreneurs’ and VCs’ goals and measures...
Magnetic behavior of a spin-1 Blume-Emery-Griffiths model
International Nuclear Information System (INIS)
Mancini, F P
2010-01-01
I study the one-dimensional spin-1 Blume-Emery-Griffiths model with bilinear and biquadratic exchange interactions and single-ion crystal field under an applied magnetic field. This model can be exactly mapped into a tight-binding Hubbard model - extended to include intersite interactions - provided one renormalizes the chemical and the on-site potentials, which become temperature dependent. After this transformation, I provide the exact solution of the Blume-Emery-Griffiths model in one dimension by means of the Green's functions and equations of motion formalism. I investigate the magnetic variations of physical quantities - such as magnetization, quadrupolar moment, susceptibility - for different values of the interaction parameters and of the applied field, focusing on the role played by the biquadratic interaction in the breakdown of the magnetization plateaus.
Quantum-memory-assisted entropic uncertainty in spin models with Dzyaloshinskii-Moriya interaction
Huang, Zhiming
2018-02-01
In this article, we investigate the dynamics and correlations of quantum-memory-assisted entropic uncertainty, the tightness of the uncertainty, entanglement, quantum correlation and mixedness for various spin chain models with Dzyaloshinskii-Moriya (DM) interaction, including the XXZ model with DM interaction, the XY model with DM interaction and the Ising model with DM interaction. We find that the uncertainty grows to a stable value with growing temperature but reduces as the coupling coefficient, anisotropy parameter and DM values increase. It is found that the entropic uncertainty is closely correlated with the mixedness of the system. The increasing quantum correlation can result in a decrease in the uncertainty, and the robustness of quantum correlation is better than entanglement since entanglement means sudden birth and death. The tightness of the uncertainty drops to zero, apart from slight volatility as various parameters increase. Furthermore, we propose an effective approach to steering the uncertainty by weak measurement reversal.
Topological phases in the Haldane model with spin–spin on-site interactions
Rubio-García, A.; García-Ripoll, J. J.
2018-04-01
Ultracold atom experiments allow the study of topological insulators, such as the non-interacting Haldane model. In this work we study a generalization of the Haldane model with spin–spin on-site interactions that can be implemented on such experiments. We focus on measuring the winding number, a topological invariant, of the ground state, which we compute using a mean-field calculation that effectively captures long-range correlations and a matrix product state computation in a lattice with 64 sites. Our main result is that we show how the topological phases present in the non-interacting model survive until the interactions are comparable to the kinetic energy. We also demonstrate the accuracy of our mean-field approach in efficiently capturing long-range correlations. Based on state-of-the-art ultracold atom experiments, we propose an implementation of our model that can give information about the topological phases.
Gronau, Greta; Jacobsen, Matthew M.; Huang, Wenwen; Rizzo, Daniel J.; Li, David; Staii, Cristian; Pugno, Nicola M.; Wong, Joyce Y.; Kaplan, David L.; Buehler, Markus J.
2016-01-01
Scalable computational modelling tools are required to guide the rational design of complex hierarchical materials with predictable functions. Here, we utilize mesoscopic modelling, integrated with genetic block copolymer synthesis and bioinspired spinning process, to demonstrate de novo materials design that incorporates chemistry, processing and material characterization. We find that intermediate hydrophobic/hydrophilic block ratios observed in natural spider silks and longer chain lengths lead to outstanding silk fibre formation. This design by nature is based on the optimal combination of protein solubility, self-assembled aggregate size and polymer network topology. The original homogeneous network structure becomes heterogeneous after spinning, enhancing the anisotropic network connectivity along the shear flow direction. Extending beyond the classical polymer theory, with insights from the percolation network model, we illustrate the direct proportionality between network conductance and fibre Young's modulus. This integrated approach provides a general path towards de novo functional network materials with enhanced mechanical properties and beyond (optical, electrical or thermal) as we have experimentally verified. PMID:26017575
Topological Symmetry, Spin Liquids and CFT Duals of Polyakov Model with Massless Fermions
Energy Technology Data Exchange (ETDEWEB)
Unsal, Mithat
2008-04-30
We prove the absence of a mass gap and confinement in the Polyakov model with massless complex fermions in any representation of the gauge group. A U(1){sub *} topological shift symmetry protects the masslessness of one dual photon. This symmetry emerges in the IR as a consequence of the Callias index theorem and abelian duality. For matter in the fundamental representation, the infrared limits of this class of theories interpolate between weakly and strongly coupled conformal field theory (CFT) depending on the number of flavors, and provide an infinite class of CFTs in d = 3 dimensions. The long distance physics of the model is same as certain stable spin liquids. Altering the topology of the adjoint Higgs field by turning it into a compact scalar does not change the long distance dynamics in perturbation theory, however, non-perturbative effects lead to a mass gap for the gauge fluctuations. This provides conceptual clarity to many subtle issues about compact QED{sub 3} discussed in the context of quantum magnets, spin liquids and phase fluctuation models in cuprate superconductors. These constructions also provide new insights into zero temperature gauge theory dynamics on R{sup 2,1} and R{sup 2,1} x S{sup 1}. The confined versus deconfined long distance dynamics is characterized by a discrete versus continuous topological symmetry.
Lin, Shangchao; Ryu, Seunghwa; Tokareva, Olena; Gronau, Greta; Jacobsen, Matthew M; Huang, Wenwen; Rizzo, Daniel J; Li, David; Staii, Cristian; Pugno, Nicola M; Wong, Joyce Y; Kaplan, David L; Buehler, Markus J
2015-05-28
Scalable computational modelling tools are required to guide the rational design of complex hierarchical materials with predictable functions. Here, we utilize mesoscopic modelling, integrated with genetic block copolymer synthesis and bioinspired spinning process, to demonstrate de novo materials design that incorporates chemistry, processing and material characterization. We find that intermediate hydrophobic/hydrophilic block ratios observed in natural spider silks and longer chain lengths lead to outstanding silk fibre formation. This design by nature is based on the optimal combination of protein solubility, self-assembled aggregate size and polymer network topology. The original homogeneous network structure becomes heterogeneous after spinning, enhancing the anisotropic network connectivity along the shear flow direction. Extending beyond the classical polymer theory, with insights from the percolation network model, we illustrate the direct proportionality between network conductance and fibre Young's modulus. This integrated approach provides a general path towards de novo functional network materials with enhanced mechanical properties and beyond (optical, electrical or thermal) as we have experimentally verified.
The status and challenge of global fire modelling
Hantson, Stijn; Arneth, Almut; Harrison, Sandy P.; Kelley, Douglas I.; Prentice, I. Colin; Rabin, Sam S.; Archibald, Sally; Mouillot, Florent; Arnold, Steve R.; Artaxo, Paulo; Bachelet, Dominique; Ciais, Philippe; Forrest, Matthew; Friedlingstein, Pierre; Hickler, Thomas; Kaplan, Jed O.; Kloster, Silvia; Knorr, Wolfgang; Lasslop, Gitta; Li, Fang; Mangeon, Stephane; Melton, Joe R.; Meyn, Andrea; Sitch, Stephen; Spessa, Allan; van der Werf, Guido R.; Voulgarakis, Apostolos; Yue, Chao
2016-06-01
Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ability to model fire regimes, using either well-founded empirical relationships or process-based models with good predictive skill. While a large variety of models exist today, it is still unclear which type of model or degree of complexity is required to model fire adequately at regional to global scales. This is the central question underpinning the creation of the Fire Model Intercomparison Project (FireMIP), an international initiative to compare and evaluate existing global fire models against benchmark data sets for present-day and historical conditions. In this paper we review how fires have been represented in fire-enabled dynamic global vegetation models (DGVMs) and give an overview of the current state of the art in fire-regime modelling. We indicate which challenges still remain in global fire modelling and stress the need for a comprehensive model evaluation and outline what lessons may be learned from FireMIP.
International Nuclear Information System (INIS)
Ji Xiangdong
2003-01-01
Spin is a beautiful concept that plays an ever important role in modern physics. In this talk, I start with a discussion of the origin of spin, and then turn to three themes in which spin has been crucial in subatomic physics: a lab to explore physics beyond the standard model, a tool to measure physical observables that are hard to obtain otherwise, a probe to unravel nonperturbative QCD. I conclude with some remarks on a world without spin
Validation of a Global Hydrodynamic Flood Inundation Model
Bates, P. D.; Smith, A.; Sampson, C. C.; Alfieri, L.; Neal, J. C.
2014-12-01
In this work we present first validation results for a hyper-resolution global flood inundation model. We use a true hydrodynamic model (LISFLOOD-FP) to simulate flood inundation at 1km resolution globally and then use downscaling algorithms to determine flood extent and depth at 90m spatial resolution. Terrain data are taken from a custom version of the SRTM data set that has been processed specifically for hydrodynamic modelling. Return periods of flood flows along the entire global river network are determined using: (1) empirical relationships between catchment characteristics and index flood magnitude in different hydroclimatic zones derived from global runoff data; and (2) an index flood growth curve, also empirically derived. Bankful return period flow is then used to set channel width and depth, and flood defence impacts are modelled using empirical relationships between GDP, urbanization and defence standard of protection. The results of these simulations are global flood hazard maps for a number of different return period events from 1 in 5 to 1 in 1000 years. We compare these predictions to flood hazard maps developed by national government agencies in the UK and Germany using similar methods but employing detailed local data, and to observed flood extent at a number of sites including St. Louis, USA and Bangkok in Thailand. Results show that global flood hazard models can have considerable skill given careful treatment to overcome errors in the publicly available data that are used as their input.
Global tropospheric ozone modeling: Quantifying errors due to grid resolution
Wild, Oliver; Prather, Michael J
2006-01-01
Ozone production in global chemical models is dependent on model resolution because ozone chemistry is inherently nonlinear, the timescales for chemical production are short, and precursors are artificially distributed over the spatial scale of the model grid. In this study we examine the sensitivity of ozone, its precursors, and its production to resolution by running a global chemical transport model at four different resolutions between T21 (5.6° × 5.6°) and T106 (1.1° × 1.1°) and by quant...
Directory of Open Access Journals (Sweden)
Omoruyi Credit Irabor
2017-12-01
Full Text Available A major contributor to the disparity in cancer outcome across the globe is the limited health care access in low- and middle-income countries that results from the shortfall in human resources for health (HRH, fomented by the limited training and leadership capacity of low-resource countries. In 2012, Seed Global Health teamed up with the Peace Corps to create the Global Health Service Partnership, an initiative that has introduced a novel model for tackling the HRH crises in developing regions of the world. The Global Health Service Partnership has made global health impacts in leveraging partnerships for HRH development, faculty activities and output, scholarship engagement, adding value to the learning environment, health workforce empowerment, and infrastructure development.
Quantification of effective plant rooting depth: advancing global hydrological modelling
Yang, Y.; Donohue, R. J.; McVicar, T.
2017-12-01
Plant rooting depth (Zr) is a key parameter in hydrological and biogeochemical models, yet the global spatial distribution of Zr is largely unknown due to the difficulties in its direct measurement. Moreover, Zr observations are usually only representative of a single plant or several plants, which can differ greatly from the effective Zr over a modelling unit (e.g., catchment or grid-box). Here, we provide a global parameterization of an analytical Zr model that balances the marginal carbon cost and benefit of deeper roots, and produce a climatological (i.e., 1982-2010 average) global Zr map. To test the Zr estimates, we apply the estimated Zr in a highly transparent hydrological model (i.e., the Budyko-Choudhury-Porporato (BCP) model) to estimate mean annual actual evapotranspiration (E) across the globe. We then compare the estimated E with both water balance-based E observations at 32 major catchments and satellite grid-box retrievals across the globe. Our results show that the BCP model, when implemented with Zr estimated herein, optimally reproduced the spatial pattern of E at both scales and provides improved model outputs when compared to BCP model results from two already existing global Zr datasets. These results suggest that our Zr estimates can be effectively used in state-of-the-art hydrological models, and potentially biogeochemical models, where the determination of Zr currently largely relies on biome type-based look-up tables.
Radiative heating in global climate models
Energy Technology Data Exchange (ETDEWEB)
Baer, F.; Arsky, N.; Rocque, K. [Univ. of Maryland, College Park, MD (United States)
1996-04-01
LWR algorithms from various GCMs vary significantly from one another for the same clear sky input data. This variability becomes pronounced when clouds are included. We demonstrate this effect by intercomparing the various models` output using observed data including clouds from ARM/CART data taken in Oklahoma.
Global comparison of three greenhouse climate models
Bavel, van C.H.M.; Takakura, T.; Bot, G.P.A.
1985-01-01
Three dynamic simulation models for calculating the greenhouse climate and its energy requirements for both heating and cooling were compared by making detailed computations for each of seven sets of data. The data sets ranged from a cold winter day, requiring heating, to a hot summer day, requiring
Global ocean modeling on the Connection Machine
International Nuclear Information System (INIS)
Smith, R.D.; Dukowicz, J.K.; Malone, R.C.
1993-01-01
The authors have developed a version of the Bryan-Cox-Semtner ocean model (Bryan, 1969; Semtner, 1976; Cox, 1984) for massively parallel computers. Such models are three-dimensional, Eulerian models that use latitude and longitude as the horizontal spherical coordinates and fixed depth levels as the vertical coordinate. The incompressible Navier-Stokes equations, with a turbulent eddy viscosity, and mass continuity equation are solved, subject to the hydrostatic and Boussinesq approximations. The traditional model formulation uses a rigid-lid approximation (vertical velocity = 0 at the ocean surface) to eliminate fast surface waves. These waves would otherwise require that a very short time step be used in numerical simulations, which would greatly increase the computational cost. To solve the equations with the rigid-lid assumption, the equations of motion are split into two parts: a set of twodimensional ''barotropic'' equations describing the vertically-averaged flow, and a set of three-dimensional ''baroclinic'' equations describing temperature, salinity and deviations of the horizontal velocities from the vertically-averaged flow
Constraints on Models for the Higgs Boson with Exotic Spin and Parity
Energy Technology Data Exchange (ETDEWEB)
Johnson, Emily Hannah [Michigan State U.
2016-01-01
The production of a Higgs boson in association with a vector boson at the Tevatron offers a unique opportunity to study models for the Higgs boson with exotic spin J and parity P assignments. At the Tevatron the V H system is produced near threshold. Different JP assignments of the Higgs boson can be distinguished by examining the behavior of the cross section near threshold. The relatively low backgrounds at the Tevatron compared to the LHC put us in a unique position to study the direct decay of the Higgs boson to fermions. If the Higgs sector is more complex than predicted, studying the spin and parity of the Higgs boson in all decay modes is important. In this Thesis we will examine the WH → ℓνb¯b production and decay mode using 9.7 fb^{-1} of data collected by the D0 experiment in an attempt to derive constraints on models containing exotic values for the spin and parity of the Higgs boson. In particular, we will examine models for a Higgs boson with JP = 0- and JP = 2+. We use a likelihood ratio to quantify the degree to which our data are incompatible with exotic JP predictions for a range of possible production rates. Assuming the production cross section times branching ratio of the signals in the models considered is equal to the standard model prediction, the WH → ℓνb¯b mode alone is unable to reject either exotic model considered. We will also discuss the combination of the ZH → ℓℓb¯b, WH → ℓνb¯b, and V H → ννb¯b production modes at the D0 experiment and with the CDF experiment. When combining all three production modes at the D0 experiment we reject the JP = 0- and JP = 2+ hypotheses at the 97.6% CL and at the 99.0% CL, respectively, when assuming the signal production cross section times branching ratio is equal to the standard model predicted value. When combining with the CDF experiment we reject the JP = 0- and JP = 2+ hypotheses with significances of 5.0 standard deviations and 4.9 standard deviations
A novel macro-model for spin-transfer-torque based magnetic-tunnel-junction elements
Lee, Seungyeon; Lee, Hyunjoo; Kim, Sojeong; Lee, Seungjun; Shin, Hyungsoon
2010-04-01
Spin-transfer-torque (STT) switching in magnetic-tunnel-junction (MTJ) has important merits over the conventional field induced magnetic switching (FIMS) MRAM in avoiding half-select problem, and improving scalability and selectivity. Design of MRAM circuitry using STT-based MTJ elements requires an accurate circuit model which exactly emulates the characteristics of an MTJ in a circuit simulator such as HSPICE. This work presents a novel macro-model that fully emulates the important characteristics of STT-based MTJ. The macro-model is realized as a three terminal sub-circuit that reproduces asymmetric resistance versus current (R-I) characteristics and temperature dependence of R-I hysteresis of STT-based MTJ element.
Coupled intertwiner dynamics: A toy model for coupling matter to spin foam models
Steinhaus, Sebastian
2015-01-01
The universal coupling of matter and gravity is one of the most important features of general relativity. In quantum gravity, in particular spin foams, matter couplings have been defined in the past, yet the mutual dynamics, in particular if matter and gravity are strongly coupled, are hardly explored, which is related to the definition of both matter and gravitational degrees of freedom on the discretisation. However extracting this mutual dynamics is crucial in testing the viability of the ...
Modelling the molecular composition and nuclear-spin chemistry of collapsing prestellar sources
Hily-Blant, P.; Faure, A.; Rist, C.; Pineau des Forêts, G.; Flower, D. R.
2018-04-01
We study the gravitational collapse of prestellar sources and the associated evolution of their chemical composition. We use the University of Grenoble Alpes Astrochemical Network (UGAN), which includes reactions involving the different nuclear-spin states of H2, H+3, and of the hydrides of carbon, nitrogen, oxygen, and sulfur, for reactions involving up to seven protons. In addition, species-to-species rate coefficients are provided for the ortho/para interconversion of the H_3^+ + H2 system and isotopic variants. The composition of the medium is followed from an initial steady state through the early phase of isothermal gravitational collapse. Both the freeze-out of the molecules on to grains and the coagulation of the grains were incorporated in the model. The predicted abundances and column densities of the spin isomers of ammonia and its deuterated forms are compared with those measured recently towards the prestellar cores H-MM1, L16293E, and Barnard B1. We find that gas-phase processes alone account satisfactorily for the observations, without recourse to grain-surface reactions. In particular, our model reproduces both the isotopologue abundance ratios and the ortho:para ratios of NH2D and NHD2 within observational uncertainties. More accurate observations are necessary to distinguish between full scrambling processes—as assumed in our gas-phase network—and direct nucleus- or atom-exchange reactions.
Free-energy analysis of spin models on hyperbolic lattice geometries.
Serina, Marcel; Genzor, Jozef; Lee, Yoju; Gendiar, Andrej
2016-04-01
We investigate relations between spatial properties of the free energy and the radius of Gaussian curvature of the underlying curved lattice geometries. For this purpose we derive recurrence relations for the analysis of the free energy normalized per lattice site of various multistate spin models in the thermal equilibrium on distinct non-Euclidean surface lattices of the infinite sizes. Whereas the free energy is calculated numerically by means of the corner transfer matrix renormalization group algorithm, the radius of curvature has an analytic expression. Two tasks are considered in this work. First, we search for such a lattice geometry, which minimizes the free energy per site. We conjecture that the only Euclidean flat geometry results in the minimal free energy per site regardless of the spin model. Second, the relations among the free energy, the radius of curvature, and the phase transition temperatures are analyzed. We found out that both the free energy and the phase transition temperature inherit the structure of the lattice geometry and asymptotically approach the profile of the Gaussian radius of curvature. This achievement opens new perspectives in the AdS-CFT correspondence theories.
Reconstructing 1/2 BPS space-time metrics from matrix models and spin chains
International Nuclear Information System (INIS)
Vazquez, Samuel E.
2007-01-01
Using the anti-de Sitter/conformal field theories (AdS/CFT) correspondence, we address the question of how to measure complicated space-time metrics using gauge theory probes. In particular, we consider the case of the 1/2 Bogomol'nyi-Prasad-Sommerfield geometries of type IIB supergravity. These geometries are classified by certain droplets in a two-dimensional spacelike hypersurface. We show how to reconstruct the full metric inside these droplets using the one-loop N=4 super Yang-Mills theory dilatation operator. This is done by considering long operators in the SU(2) sector, which are dual to fast rotating strings on the droplets. We develop new powerful techniques for large N complex matrix models that allow us to construct the Hamiltonian for these strings. We find that the Hamiltonian can be mapped to a dynamical spin chain. That is, the length of the chain is not fixed. Moreover, all of these spin chains can be explicitly constructed using an interesting algebra which is derived from the matrix model. Our techniques work for general droplet configurations. As an example, we study a single elliptical droplet and the hypotrochoid
Global warming description using Daisyworld model with greenhouse gases.
Paiva, Susana L D; Savi, Marcelo A; Viola, Flavio M; Leiroz, Albino J K
2014-11-01
Daisyworld is an archetypal model of the earth that is able to describe the global regulation that can emerge from the interaction between life and environment. This article proposes a model based on the original Daisyworld considering greenhouse gases emission and absorption, allowing the description of the global warming phenomenon. Global and local analyses are discussed evaluating the influence of greenhouse gases in the planet dynamics. Numerical simulations are carried out showing the general qualitative behavior of the Daisyworld for different scenarios that includes solar luminosity variations and greenhouse gases effect. Nonlinear dynamics perspective is of concern discussing a way that helps the comprehension of the global warming phenomenon. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.
A coupled chemotaxis-fluid model: Global existence
Liu, Jian-Guo; Lorz, Alexander
2011-01-01
We consider a model arising from biology, consisting of chemotaxis equations coupled to viscous incompressible fluid equations through transport and external forcing. Global existence of solutions to the Cauchy problem is investigated under certain conditions. Precisely, for the chemotaxis-Navier- Stokes system in two space dimensions, we obtain global existence for large data. In three space dimensions, we prove global existence of weak solutions for the chemotaxis-Stokes system with nonlinear diffusion for the cell density.© 2011 Elsevier Masson SAS. All rights reserved.
A coupled chemotaxis-fluid model: Global existence
Liu, Jian-Guo
2011-09-01
We consider a model arising from biology, consisting of chemotaxis equations coupled to viscous incompressible fluid equations through transport and external forcing. Global existence of solutions to the Cauchy problem is investigated under certain conditions. Precisely, for the chemotaxis-Navier- Stokes system in two space dimensions, we obtain global existence for large data. In three space dimensions, we prove global existence of weak solutions for the chemotaxis-Stokes system with nonlinear diffusion for the cell density.© 2011 Elsevier Masson SAS. All rights reserved.
Global asymptotic stability of density dependent integral population projection models.
Rebarber, Richard; Tenhumberg, Brigitte; Townley, Stuart
2012-02-01
Many stage-structured density dependent populations with a continuum of stages can be naturally modeled using nonlinear integral projection models. In this paper, we study a trichotomy of global stability result for a class of density dependent systems which include a Platte thistle model. Specifically, we identify those systems parameters for which zero is globally asymptotically stable, parameters for which there is a positive asymptotically stable equilibrium, and parameters for which there is no asymptotically stable equilibrium. Copyright © 2011 Elsevier Inc. All rights reserved.