Wigner phase space distribution via classical adiabatic switching
Energy Technology Data Exchange (ETDEWEB)
Bose, Amartya [Department of Chemistry, University of Illinois, 600 S. Goodwin Avenue, Urbana, Illinois 61801 (United States); Makri, Nancy [Department of Chemistry, University of Illinois, 600 S. Goodwin Avenue, Urbana, Illinois 61801 (United States); Department of Physics, University of Illinois, 1110 W. Green Street, Urbana, Illinois 61801 (United States)
2015-09-21
Evaluation of the Wigner phase space density for systems of many degrees of freedom presents an extremely demanding task because of the oscillatory nature of the Fourier-type integral. We propose a simple and efficient, approximate procedure for generating the Wigner distribution that avoids the computational difficulties associated with the Wigner transform. Starting from a suitable zeroth-order Hamiltonian, for which the Wigner density is available (either analytically or numerically), the phase space distribution is propagated in time via classical trajectories, while the perturbation is gradually switched on. According to the classical adiabatic theorem, each trajectory maintains a constant action if the perturbation is switched on infinitely slowly. We show that the adiabatic switching procedure produces the exact Wigner density for harmonic oscillator eigenstates and also for eigenstates of anharmonic Hamiltonians within the Wentzel-Kramers-Brillouin (WKB) approximation. We generalize the approach to finite temperature by introducing a density rescaling factor that depends on the energy of each trajectory. Time-dependent properties are obtained simply by continuing the integration of each trajectory under the full target Hamiltonian. Further, by construction, the generated approximate Wigner distribution is invariant under classical propagation, and thus, thermodynamic properties are strictly preserved. Numerical tests on one-dimensional and dissipative systems indicate that the method produces results in very good agreement with those obtained by full quantum mechanical methods over a wide temperature range. The method is simple and efficient, as it requires no input besides the force fields required for classical trajectory integration, and is ideal for use in quasiclassical trajectory calculations.
Torus as phase space: Weyl quantization, dequantization, and Wigner formalism
Energy Technology Data Exchange (ETDEWEB)
Ligabò, Marilena, E-mail: marilena.ligabo@uniba.it [Dipartimento di Matematica, Università di Bari, I-70125 Bari (Italy)
2016-08-15
The Weyl quantization of classical observables on the torus (as phase space) without regularity assumptions is explicitly computed. The equivalence class of symbols yielding the same Weyl operator is characterized. The Heisenberg equation for the dynamics of general quantum observables is written through the Moyal brackets on the torus and the support of the Wigner transform is characterized. Finally, a dequantization procedure is introduced that applies, for instance, to the Pauli matrices. As a result we obtain the corresponding classical symbols.
Tunneling of an energy eigenstate through a parabolic barrier viewed from Wigner phase space
DEFF Research Database (Denmark)
Heim, D.M.; Schleich, W.P.; Alsing, P.M.
2013-01-01
We analyze the tunneling of a particle through a repulsive potential resulting from an inverted harmonic oscillator in the quantum mechanical phase space described by the Wigner function. In particular, we solve the partial differential equations in phase space determining the Wigner function...
Torre, Amalia
2005-01-01
Ray, wave and quantum concepts are central to diverse and seemingly incompatible models of light. Each model particularizes a specific ''manifestation'' of light, and then corresponds to adequate physical assumptions and formal approximations, whose domains of applicability are well-established. Accordingly each model comprises its own set of geometric and dynamic postulates with the pertinent mathematical means.At a basic level, the book is a complete introduction to the Wigner optics, which bridges between ray and wave optics, offering the optical phase space as the ambience and the Wigner f
Wigner's quantum phase-space current in weakly-anharmonic weakly-excited two-state systems
Kakofengitis, Dimitris; Steuernagel, Ole
2017-09-01
There are no phase-space trajectories for anharmonic quantum systems, but Wigner's phase-space representation of quantum mechanics features Wigner current J . This current reveals fine details of quantum dynamics —finer than is ordinarily thought accessible according to quantum folklore invoking Heisenberg's uncertainty principle. Here, we focus on the simplest, most intuitive, and analytically accessible aspects of J. We investigate features of J for bound states of time-reversible, weakly-anharmonic one-dimensional quantum-mechanical systems which are weakly-excited. We establish that weakly-anharmonic potentials can be grouped into three distinct classes: hard, soft, and odd potentials. We stress connections between each other and the harmonic case. We show that their Wigner current fieldline patterns can be characterised by J's discrete stagnation points, how these arise and how a quantum system's dynamics is constrained by the stagnation points' topological charge conservation. We additionally show that quantum dynamics in phase space, in the case of vanishing Planck constant ℏ or vanishing anharmonicity, does not pointwise converge to classical dynamics.
Weyl-Wigner correspondence in two space dimensions
DEFF Research Database (Denmark)
Dahl, Jens Peder; Varro, S.; Wolf, A.
2007-01-01
the eigenvalue equations for energy and angular momentum into phase space. As a result we arrive at partial differential equations in phase space which determine the corresponding Wigner function. We then solve the resulting equations using appropriate coordinates....
A number-phase Wigner function
Energy Technology Data Exchange (ETDEWEB)
Moya-Cessa, Hector [INAOE, Coordinacion de Optica, Apartado Postal 51 y 216, 72000 Puebla, Puebla (Mexico)
2003-06-01
One of the most prominent quasiprobability functions in quantum mechanics is the Wigner function, which gives the correct marginal probability functions if integrated over position or momentum. Here we depart from the definition of the position-momentum Wigner function to, by analogy, construct a number-phase Wigner function that, if summed over photon numbers, gives the correct phase distribution and, if integrated over phase, gives the correct photon distribution.
Bencheikh, K.; Nieto, L. M.
2008-11-01
Closed form analytical expressions are obtained for the Wigner transform of the Bloch density matrix and for the Wigner phase-space density of a two-dimensional harmonically trapped charged quantum gas in a uniform magnetic field of arbitrary strength, at zero and nonzero temperatures. An exact analytic expression is also obtained for the autocorrelation function. The strong magnetic field case, where only few Landau levels are occupied, is also examined, and useful approximate expressions for the spatial and momentum densities are given.
Space fractional Wigner equation and its semiclassical limit.
Stickler, B A; Schachinger, E
2011-12-01
Manifestations of space fractional quantum mechanics (SFQM), as it was formulated by Laskin [Phys. Rev. E 62, 3135 (2000)], are deemed to offer a better physical interpretation of Lévy flight statistics on a quantum mechanical level. We start with the SFQM Schrödinger equation characterized by a Lévy flight index α∈ (1,2), perform a Wigner transform, and draw the limit h/Eτ → 0 (i.e., let the observed energy scale E go to infinity in comparison to the quantization given by h/τ). In order to obtain classical transport equations two possible substitutions for the terms |p|(α) and |p'|α which appear in von Neumann's equation are presented. It is demonstrated that they conform to the criteria for a successful Wigner transform. Their benefits and caveats are discussed in detail. We find, that, indeed, SFQM manifests itself in an anomalous kinetic term of the free particle's motion and, assuming an external potential diagonal in momentum space for the sake of simplicity, in corresponding anomalous terms in the resulting drift current. All our results reduce to the classical forms in the limit α = 2.
On quantum mechanical phase-space wave functions
DEFF Research Database (Denmark)
Wlodarz, Joachim J.
1994-01-01
An approach to quantum mechanics based on the notion of a phase-space wave function is proposed within the Weyl-Wigner-Moyal representation. It is shown that the Schrodinger equation for the phase-space wave function is equivalent to the quantum Liouville equation for the Wigner distribution...
Dynamics of Gaussian Wigner functions derived from a time-dependent variational principle
National Research Council Canada - National Science Library
Poulsen, Jens Aage; Svensson, S. Karl-Mikael; Nyman, Gunnar
2017-01-01
By using a time-dependent variational principle formulated for Wigner phase-space functions, we obtain the optimal time-evolution for two classes of Gaussian Wigner functions, namely those of either...
Quantum Shuttle in Phase Space
DEFF Research Database (Denmark)
Novotny, Tomas; Donarini, Andrea; Jauho, Antti-Pekka
2003-01-01
Abstract: We present a quantum theory of the shuttle instability in electronic transport through a nanostructure with a mechanical degree of freedom. A phase space formulation in terms of the Wigner function allows us to identify a crossover from the tunneling to the shuttling regime, thus...... extending the previously found classical results to the quantum domain. Further, a new dynamical regime is discovered, where the shuttling is driven exclusively by the quantum noise....
Optical image encryption in phase space
Liu, Jun; Xu, Xiaobin; Situ, Guohai; Wu, Quanying
2014-11-01
In the field of optical information security, the research of double random phase encoding is becoming deeper with each passing day, however the encryption system is linear, and the dependencies between plaintext and ciphertext is not complicated, with leaving a great hidden danger to the security of the encryption system. In this paper, we encrypted the higher dimensional Wigner distribution function of low dimensional plaintext by using the bilinear property of Wigner distribution function. Computer simulation results show that this method can not only enlarge the key space, but also break through the linear characteristic of the traditional optical encryption technology. So it can significantly improve the safety of the encryption system.
Presumption of Phase Shift in Resonant Dynamical Systems using Wigner-Ville Distribution Function
Niimi, Hironobu; Yatsu, Shigeo; Kayukawa, Naoyuki
2002-02-01
The time evolution of the forced and eigen oscillation modes of a basic rotor model induced by an external force with frequencies of linear functions of time was analyzed by means of the Wigner-Ville distribution function. The instantaneous frequency of the forced oscillation was extracted from the spectrum distribution on the time-frequency plane, and the phase shift between the forced oscillation and the external force was calculated for both weak and strong nonstationariness cases. In the latter case, neither forced nor eigen modes could be separated definitely around the resonant point. This resulted in a discrepancy of the asymptotic value of the phase shift from π in cooperation with the finite frequency resolution. It was shown that the phase shift in this “mixed mode region” could be numerically traced and the bifurcation point could be approximately identified on the basis of the finding that the asymptotic value of the phase shift in the present model was π, irrespective of the nonstationariness.
The eigenvalue problem in phase space.
Cohen, Leon
2017-07-27
We formulate the standard quantum mechanical eigenvalue problem in quantum phase space. The equation obtained involves the c-function that corresponds to the quantum operator. We use the Wigner distribution for the phase space function. We argue that the phase space eigenvalue equation obtained has, in addition to the proper solutions, improper solutions. That is, solutions for which no wave function exists which could generate the distribution. We discuss the conditions for ascertaining whether a position momentum function is a proper phase space distribution. We call these conditions psi-representability conditions, and show that if these conditions are imposed, one extracts the correct phase space eigenfunctions. We also derive the phase space eigenvalue equation for arbitrary phase space distributions functions. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.
Floquet projections of a Gaussian Wigner function in a Kronig-Penney potential
Energy Technology Data Exchange (ETDEWEB)
Maccari, L; Demeio, L [Dipartimento di Scienze Matematiche, Via Brecce Bianche, Universita Politecnica delle Marche, 60131 Ancona (Italy); Bordone, P, E-mail: maccari@dipmat.univpm.i [Physics Department, University of Modena and Reggio Emilia, Via Campi 213/A, I-41025 Modena (Italy)
2009-11-15
In this contribution, we apply the multiband model developed in [1] to a Kronig-Penney potential and calculate the Floquet projections of a Gaussian Wigner function in phase space. The Bloch functions are calculated numerically and then used in the expressions of the Wigner projections.
The Morse oscillator in position space, momentum space, and phase space
DEFF Research Database (Denmark)
Dahl, Jens Peder; Springborg, Michael
1988-01-01
We present a unified description of the position-space wave functions, the momentum-space wave functions, and the phase-space Wigner functions for the bound states of a Morse oscillator. By comparing with the functions for the harmonic oscillator the effects of anharmonicity are visualized. Analy...... for the Morse oscillator. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....
Quantum dynamics via a time propagator in Wigner's phase space
DEFF Research Database (Denmark)
Grønager, Michael; Henriksen, Niels Engholm
1995-01-01
that the simple classical deterministic motion breaks down surprisingly fast in an anharmonic potential. Finally, we discuss the possibility of using the scheme as a useful approach to quantum dynamics in many dimensions. To that end we present a Monte Carlo integration scheme using the norm of the propagator...
Applications of the Wigner Distribution Function in Signal Processing
Directory of Open Access Journals (Sweden)
Dragoman Daniela
2005-01-01
Full Text Available We present a review of the applications of the Wigner distribution function in various areas of signal processing: amplitude and phase retrieval, signal recognition, characterization of arbitrary signals, optical systems and devices, and coupling coefficient estimation in phase space. Although reference is made to specific signals and systems, the mathematical formulation is general and can be applied to either spatial, temporal, or spatio-temporal phase spaces, to coherent, partially coherent, or discrete signals. The universal and intuitive character of the Wigner distribution approach to signal characterization and processing and its simplicity in solving many issues are evidenced throughout the paper.
Wigner functions for angle and orbital angular momentum. Operators and dynamics
Energy Technology Data Exchange (ETDEWEB)
Kastrup, Hans A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie
2017-02-15
Recently a paper on the construction of consistent Wigner functions for cylindrical phase spaces S{sup 1} x R, i.e. for the canonical pair angle and orbital angular momentum, was presented, main properties of those functions derived, discussed and their usefulness illustrated by examples. The present paper is a continuation which compares properties of the new Wigner functions for cylindrical phase spaces with those of the well-known Wigner functions on planar ones in more detail. Furthermore, the mutual (Weyl) correspondence between HIlbert space operators and their phase space functions is discussed. The * product formalism is shown to be completely implementable. In addition basic dynamical laws for Wigner and Moyal functions are derived as generalized Liouville and energy equations. They are very similar to those of the planar case, but also show characteristic differences.
Simple procedure for phase-space measurement and entanglement validation
Rundle, R. P.; Mills, P. W.; Tilma, Todd; Samson, J. H.; Everitt, M. J.
2017-08-01
It has recently been shown that it is possible to represent the complete quantum state of any system as a phase-space quasiprobability distribution (Wigner function) [Phys. Rev. Lett. 117, 180401 (2016), 10.1103/PhysRevLett.117.180401]. Such functions take the form of expectation values of an observable that has a direct analogy to displaced parity operators. In this work we give a procedure for the measurement of the Wigner function that should be applicable to any quantum system. We have applied our procedure to IBM's Quantum Experience five-qubit quantum processor to demonstrate that we can measure and generate the Wigner functions of two different Bell states as well as the five-qubit Greenberger-Horne-Zeilinger state. Because Wigner functions for spin systems are not unique, we define, compare, and contrast two distinct examples. We show how the use of these Wigner functions leads to an optimal method for quantum state analysis especially in the situation where specific characteristic features are of particular interest (such as for spin Schrödinger cat states). Furthermore we show that this analysis leads to straightforward, and potentially very efficient, entanglement test and state characterization methods.
Wigner distribution function for finite signals
Wolf, Kurt B.; Atakishiyev, Natig M.; Chumakov, Sergey M.
1997-07-01
We construct a bilinear form with the properties of the Wigner distribution function for a model of finite optics: the multimodal linear waveguide. This is a guide that can carry a finite number of oscillator modes, and sends/reads the data by an equal number of sensors. The Wigner distribution function is a function of the classical observables of position and momentum, as well as the mode content; it provides a visual image corresponding to the (`musical') score of the signal. The dynamical group for this model is SU(2) and the wavefunctions span the space of a finite-dimensional irreducible representation of this group. Phase space is a sphere and the linear optical transformations are: translations along the waveguide, refractive wedges and inclined slabs, which correspond to rotations around the 3-, 1-, and 2-axes, respectively. Coherent and Schrodinger cat states are readily identified.
Quantum mechanics on phase space and the Coulomb potential
Campos, P.; Martins, M. G. R.; Vianna, J. D. M.
2017-04-01
Symplectic quantum mechanics (SMQ) makes possible to derive the Wigner function without the use of the Liouville-von Neumann equation. In this formulation of the quantum theory the Galilei Lie algebra is constructed using the Weyl (or star) product with Q ˆ = q ⋆ = q +iħ/2∂p , P ˆ = p ⋆ = p -iħ/2∂q, and the Schrödinger equation is rewritten in phase space; in consequence physical applications involving the Coulomb potential present some specific difficulties. Within this context, in order to treat the Schrödinger equation in phase space, a procedure based on the Levi-Civita (or Bohlin) transformation is presented and applied to two-dimensional (2D) hydrogen atom. Amplitudes of probability in phase space and the correspondent Wigner quasi-distribution functions are derived and discussed.
Semiclassical TEM image formation in phase space.
Lubk, Axel; Röder, Falk
2015-04-01
Current developments in TEM such as high-resolution imaging at low acceleration voltages and large fields of view, the ever larger capabilities of hardware aberration correction and the systematic shaping of electron beams require accurate descriptions of TEM imaging in terms of wave optics. Since full quantum mechanic solutions have not yet been established for, e.g., the theory of aberrations, we are exploring semiclassical image formation in the TEM from the perspective of quantum mechanical phase space, here. Firstly, we use two well-known semiclassical approximations, Miller's semiclassical algebra and the frozen Gaussian method, for describing the wave optical generalization of arbitrary geometric aberrations, including nonisoplanatic and slope aberrations. Secondly, we demonstrate that the Wigner function representation of phase space is well suited to also describe incoherent aberrations as well as the ramifications of partial coherence due to the emission process at the electron source. We identify a close relationship between classical phase space and Wigner function distortions due to aberrations as well as classical brightness and quantum mechanical purity. Copyright © 2014 Elsevier B.V. All rights reserved.
An elementary aspect of the Weyl-Wigner representation
DEFF Research Database (Denmark)
Dahl, Jens Peder; Schleich, W.P.
2003-01-01
It is an elementary aspect of the Weyl-Wigner representation of quantum mechanics that the dynamical phase-space function corresponding to the square of a quantum-mechanical operator is, in general, different from the square of the function representing the operator itself. We call attention...
A Quantum Version of Wigner's Transition State Theory
Schubert, R.; Waalkens, H.; Wiggins, S.
A quantum version of a recent realization of Wigner's transition state theory in phase space is presented. The theory developed builds on a quantum normal form which locally decouples the quantum dynamics near the transition state to any desired order in (h) over bar. This leads to an explicit
Phase space picture of quantum mechanics group theoretical approach
Kim, Y S
1991-01-01
This book covers the theory and applications of the Wigner phase space distribution function and its symmetry properties. The book explains why the phase space picture of quantum mechanics is needed, in addition to the conventional Schrödinger or Heisenberg picture. It is shown that the uncertainty relation can be represented more accurately in this picture. In addition, the phase space picture is shown to be the natural representation of quantum mechanics for modern optics and relativistic quantum mechanics of extended objects.
Discrete Wigner Function Derivation of the Aaronson–Gottesman Tableau Algorithm
Directory of Open Access Journals (Sweden)
Lucas Kocia
2017-07-01
Full Text Available The Gottesman–Knill theorem established that stabilizer states and Clifford operations can be efficiently simulated classically. For qudits with odd dimension three and greater, stabilizer states and Clifford operations have been found to correspond to positive discrete Wigner functions and dynamics. We present a discrete Wigner function-based simulation algorithm for odd-d qudits that has the same time and space complexity as the Aaronson–Gottesman algorithm for qubits. We show that the efficiency of both algorithms is due to harmonic evolution in the symplectic structure of discrete phase space. The differences between the Wigner function algorithm for odd-d and the Aaronson–Gottesman algorithm for qubits are likely due only to the fact that the Weyl–Heisenberg group is not in S U ( d for d = 2 and that qubits exhibit state-independent contextuality. This may provide a guide for extending the discrete Wigner function approach to qubits.
The Phase Space Formulation of Time-Symmetric Quantum Mechanics
Directory of Open Access Journals (Sweden)
Charlyne de Gosson
2015-11-01
Full Text Available Time-symmetric quantum mechanics can be described in the Weyl–Wigner–Moyal phase space formalism by using the properties of the cross-terms appearing in the Wigner distribution of a sum of states. These properties show the appearance of a strongly oscillating interference between the pre-selected and post-selected states. It is interesting to note that the knowledge of this interference term is sufficient to reconstruct both states. Quanta 2015; 4: 27–34.
On the Salecker-Wigner limit and the use of interferometers in space-time-foam studies
Amelino-Camelia, G
2000-01-01
The recent paper gr-qc/9909017 criticizes the limit on the measurability of distances that was derived by Salecker and Wigner in the 1950s. If justified, this criticism would have important implications for all the recent studies that have used in various ways the celebrated Salecker-Wigner result, but I show here that the analysis reported in gr-qc/9909017 is incorrect. Whereas Salecker and Wigner sought an operative definition of distances suitable for the Planck regime, the analysis in gr-qc/9909017 relies on several assumptions that appear to be natural in the context of most present-day experiments but are not even meaningful in the Planck regime. Moreover, contrary to the claim made in gr-qc/9909017, a relevant quantum uncertainty which is used in the Salecker-Wigner derivation cannot be truly eliminated; unsurprisingly, it can only be traded for another comparable contribution to the total uncertainty in the measurement. I also comment on the role played by the Salecker-Wigner limit in my recent propos...
Energy Technology Data Exchange (ETDEWEB)
Chao, Alexander Wu; /SLAC
2012-03-01
As accelerator technology advances, the requirements on accelerator beam quality become increasingly demanding. Facing these new demands, the topic of phase space gymnastics is becoming a new focus of accelerator physics R&D. In a phase space gymnastics, the beam's phase space distribution is manipulated and precision tailored to meet the required beam qualities. On the other hand, all realization of such gymnastics will have to obey accelerator physics principles as well as technological limitations. Recent examples of phase space gymnastics include Emittance exchanges, Phase space exchanges, Emittance partitioning, Seeded FELs and Microbunched beams. The emittance related topics of this list are reviewed in this report. The accelerator physics basis, the optics design principles that provide these phase space manipulations, and the possible applications of these gymnastics, are discussed. This fascinating new field promises to be a powerful tool of the future.
Phase space and phase space transformations
Energy Technology Data Exchange (ETDEWEB)
Alefeld, B.
1985-03-01
For neutron scattering instrumentation Liouville's theorem plays a similar role as the second law of thermodynamics at least in the sense that from time to time 'ingenious' devices are discussed seriously, which are meant to increase the phase space density, these devices are analogous to a perpetuum mobile of the second kind.
An introduction to applied quantum mechanics in the Wigner Monte Carlo formalism
Energy Technology Data Exchange (ETDEWEB)
Sellier, J.M., E-mail: jeanmichel.sellier@parallel.bas.bg [IICT, Bulgarian Academy of Sciences, Acad. G. Bonchev str. 25A, 1113 Sofia (Bulgaria); Nedjalkov, M. [IICT, Bulgarian Academy of Sciences, Acad. G. Bonchev str. 25A, 1113 Sofia (Bulgaria); Institute for Microelectronics, TU Wien, Gußhausstraße 27-29/E360, 1040 Wien (Austria); Dimov, I. [IICT, Bulgarian Academy of Sciences, Acad. G. Bonchev str. 25A, 1113 Sofia (Bulgaria)
2015-05-12
The Wigner formulation of quantum mechanics is a very intuitive approach which allows the comprehension and prediction of quantum mechanical phenomena in terms of quasi-distribution functions. In this review, our aim is to provide a detailed introduction to this theory along with a Monte Carlo method for the simulation of time-dependent quantum systems evolving in a phase-space. This work consists of three main parts. First, we introduce the Wigner formalism, then we discuss in detail the Wigner Monte Carlo method and, finally, we present practical applications. In particular, the Wigner model is first derived from the Schrödinger equation. Then a generalization of the formalism due to Moyal is provided, which allows to recover important mathematical properties of the model. Next, the Wigner equation is further generalized to the case of many-body quantum systems. Finally, a physical interpretation of the negative part of a quasi-distribution function is suggested. In the second part, the Wigner Monte Carlo method, based on the concept of signed (virtual) particles, is introduced in detail for the single-body problem. Two extensions of the Wigner Monte Carlo method to quantum many-body problems are introduced, in the frameworks of time-dependent density functional theory and ab-initio methods. Finally, in the third and last part of this paper, applications to single- and many-body problems are performed in the context of quantum physics and quantum chemistry, specifically focusing on the hydrogen, lithium and boron atoms, the H{sub 2} molecule and a system of two identical Fermions. We conclude this work with a discussion on the still unexplored directions the Wigner Monte Carlo method could take in the next future.
Wigner functions for angle and orbital angular momentum: Operators and dynamics
Kastrup, H. A.
2017-05-01
Recently a paper on the construction of consistent Wigner functions for cylindrical phase spaces S1×R , i.e., for the canonical pair angle and orbital angular momentum, was published [H. A. Kastrup, Phys. Rev. A 94, 062113 (2016), 10.1103/PhysRevA.94.062113] in which the main properties of these functions are derived and discussed and their usefulness is illustrated with examples. The present paper is a continuation which compares the properties of the Wigner functions for cylindrical phase spaces with those of the well-known Wigner functions for planar phase spaces in more detail. Furthermore, the mutual (Weyl) correspondence between Hilbert space operators and their phase-space functions is discussed. The product formalism is shown to be completely implementable. In addition, basic dynamical laws for Wigner and Moyal functions are derived as generalized Liouville and energy equations. They are very similar to those in the planar case but also show characteristic differences.
Unrestricted Hartree-Fock theory of Wigner crystals
Trail, J. R.; Towler, M. D.; Needs, R. J.
2009-01-01
We demonstrate that unrestricted Hartree-Fock theory applied to electrons in a uniform potential has stable Wigner crystal solutions for $r_s \\geq 1.44$ in two dimensions and $r_s \\geq 4.5$ in three dimensions. The correlation energies of the Wigner crystal phases are considerably smaller than those of the fluid phases at the same density.
Discrete Wigner function dynamics
Energy Technology Data Exchange (ETDEWEB)
Klimov, A B; Munoz, C [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44410, Guadalajara, Jalisco (Mexico)
2005-12-01
We study the evolution of the discrete Wigner function for prime and the power of prime dimensions using the discrete version of the star-product operation. Exact and semiclassical dynamics in the limit of large dimensions are considered.
Wigner's Symmetry Representation Theorem
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 10. Wigner's Symmetry Representation Theorem: At the Heart of Quantum Field Theory! Aritra Kr Mukhopadhyay. General Article Volume 19 Issue 10 October 2014 pp 900-916 ...
Quantum Potential and Symmetries in Extended Phase Space
Directory of Open Access Journals (Sweden)
Sadollah Nasiri
2006-06-01
Full Text Available The behavior of the quantum potential is studied for a particle in a linear and a harmonic potential by means of an extended phase space technique. This is done by obtaining an expression for the quantum potential in momentum space representation followed by the generalization of this concept to extended phase space. It is shown that there exists an extended canonical transformation that removes the expression for the quantum potential in the dynamical equation. The situation, mathematically, is similar to disappearance of the centrifugal potential in going from the spherical to the Cartesian coordinates that changes the physical potential to an effective one. The representation where the quantum potential disappears and the modified Hamilton-Jacobi equation reduces to the familiar classical form, is one in which the dynamical equation turns out to be the Wigner equation.
Nonclassical phase-space trajectories for the damped harmonic quantum oscillator
Energy Technology Data Exchange (ETDEWEB)
Pachon, L.A. [Departamento de Fisica, Universidad Nacional de Colombia, Bogota D.C. (Colombia); Institut fuer Physik, Universitaet Augsburg, Universitaetsstrasse 1, D-86135 Augsburg (Germany); CeiBA - Complejidad, Bogota D.C. (Colombia); Ingold, G.-L., E-mail: gert.ingold@physik.uni-augsburg.de [Institut fuer Physik, Universitaet Augsburg, Universitaetsstrasse 1, D-86135 Augsburg (Germany); Dittrich, T. [Departamento de Fisica, Universidad Nacional de Colombia, Bogota D.C. (Colombia); CeiBA - Complejidad, Bogota D.C. (Colombia)
2010-10-05
Graphical abstract: The phase-space path-integral approach to the damped harmonic oscillator is analyzed beyond the Markovian approximation and the appearance of nonclassical trajectories is discussed. - Abstract: The phase-space path-integral approach to the damped harmonic oscillator is analyzed beyond the Markovian approximation. It is found that pairs of nonclassical trajectories contribute to the path-integral representation of the Wigner propagating function. Due to the linearity of the problem, the sum coordinate of a pair still satisfies the classical equation of motion. Furthermore, it is shown that the broadening of the Wigner propagating function of the damped oscillator arises due to the time-nonlocal interaction mediated by the heat bath.
Wigner Distribution of Twisted Photons
Mirhosseini, Mohammad; Magaña-Loaiza, Omar S.; Chen, Changchen; Hashemi Rafsanjani, Seyed Mohammad; Boyd, Robert W.
2016-04-01
We present the first experimental characterization of the azimuthal Wigner distribution of a photon. Our protocol fully characterizes the transverse structure of a photon in conjugate bases of orbital angular momentum (OAM) and azimuthal angle. We provide a test of our protocol by characterizing pure superpositions and incoherent mixtures of OAM modes in a seven-dimensional space. The time required for performing measurements in our scheme scales only linearly with the dimension size of the state under investigation. This time scaling makes our technique suitable for quantum information applications involving a large number of OAM states.
Collective motion in the frame of phase space moments (Nuclear scissors)
Energy Technology Data Exchange (ETDEWEB)
Balbutsev, E B, E-mail: balbuts@thsun1.jinr.r [Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region (Russian Federation)
2010-01-01
We consider the phase space moments (or Wigner Function Moments (WFM)) method, which is developed to describe the collective motion. The method is generalized to take into account pair correlations. Its connection with RPA and Green's function method is analyzed in the simple model, the Harmonic Oscillator with Quadrupole-Quadrupole (HO+QQ) interaction. Possibilities of WFM method are demonstrated on an example of the nuclear scissors mode.
Phase-space representation of non-classical behaviour of scalar wave-fields
Energy Technology Data Exchange (ETDEWEB)
Canas-Cardona, Gustavo; Castaneda, Roman [Physics School, Universidad Nacional de Colombia Sede Medellin, A.A. 3840 Medellin (Colombia); Vinck-Posada, Herbert, E-mail: gcanas@unal.edu.co [Physics Department, Universidad Nacional de Colombia Sede Bogota, Bogota D.C (Colombia)
2011-01-01
The modelling of optical fields by using radiant and virtual point sources for the spatial coherence wavelets in the phase-space representation evidences some effects, conventionally attributed to non-classical correlations of light, although such type of correlations are not explicitly included in the model. Specifically, a light state is produced that has similar morphology to the Wigner Distribution Function of the well-known quantum Schroedinger cat and squeezed states.
Phase-space evolution of x-ray coherence in phase-sensitive imaging.
Wu, Xizeng; Liu, Hong
2008-08-01
X-ray coherence evolution in the imaging process plays a key role for x-ray phase-sensitive imaging. In this work we present a phase-space formulation for the phase-sensitive imaging. The theory is reformulated in terms of the cross-spectral density and associated Wigner distribution. The phase-space formulation enables an explicit and quantitative account of partial coherence effects on phase-sensitive imaging. The presented formulas for x-ray spectral density at the detector can be used for performing accurate phase retrieval and optimizing the phase-contrast visibility. The concept of phase-space shearing length derived from this phase-space formulation clarifies the spatial coherence requirement for phase-sensitive imaging with incoherent sources. The theory has been applied to x-ray Talbot interferometric imaging as well. The peak coherence condition derived reveals new insights into three-grating-based Talbot-interferometric imaging and gratings-based x-ray dark-field imaging.
Wigner's Symmetry Representation Theorem
Indian Academy of Sciences (India)
IAS Admin
This article elucidates the important role the no- tion of symmetry has played in physics. It dis- cusses the proof of one of the important theorems of quantum mechanics, viz., Wigner's Symmetry. Representation Theorem. It also shows how the representations of various continuous and dis- crete symmetries follow from the ...
Orthogonality preserving property, Wigner equation, and stability
Directory of Open Access Journals (Sweden)
Chmieliński Jacek
2006-01-01
Full Text Available We deal with the stability of the orthogonality preserving property in the class of mappings phase-equivalent to linear or conjugate-linear ones. We give a characterization of approximately orthogonality preserving mappings in this class and we show some connections between the considered stability and the stability of the Wigner equation.
Moshinsky atom and density functional theory - A phase space view(1)
DEFF Research Database (Denmark)
Dahl, Jens Peder
2009-01-01
Le probleme de deux particules dans un potentiel d'oscillateur harmonique commun interagissant par le biais de forces d'oscillateur harmonique est discute dans la representation phase-espace de Weyl-Wigner. La fonction de Wigner du systeme est une fonction ordinaire des constantes phase-espace du...
Observation of a magnetically induced Wigner solid
Andrei, E. Y.; Deville, G.; Glattli, D. C.; Williams, F. I. B.; Paris, E.; Etienne, B.
1988-06-01
The existence of the magnetic-field-induced liquid-to-solid phase transition in an extreme quantum-limit 2D electron plasma is established for electrons at a high-quality GaAs/GaAlAs heterojunction by detection of a gapless magnetophonon excitation branch with radio-frequency spectroscopy. The phase diagram, determined for Wigner-Seitz to Bohr radius ratio 1.6∞) limit.
Higher-order stochastic differential equations and the positive Wigner function
Drummond, P. D.
2017-12-01
General higher-order stochastic processes that correspond to any diffusion-type tensor of higher than second order are obtained. The relationship of multivariate higher-order stochastic differential equations with tensor decomposition theory and tensor rank is explained. Techniques for generating the requisite complex higher-order noise are proved to exist either using polar coordinates and γ distributions, or from products of Gaussian variates. This method is shown to allow the calculation of the dynamics of the Wigner function, after it is extended to a complex phase space. The results are illustrated physically through dynamical calculations of the positive Wigner distribution for three-mode parametric downconversion, widely used in quantum optics. The approach eliminates paradoxes arising from truncation of the higher derivative terms in Wigner function time evolution. Anomalous results of negative populations and vacuum scattering found in truncated Wigner quantum simulations in quantum optics and Bose-Einstein condensate dynamics are shown not to occur with this type of stochastic theory.
Schleich, W P; Mayr, E
1998-01-01
Quantum Optics in Phase Space provides a concise introduction to the rapidly moving field of quantum optics from the point of view of phase space. Modern in style and didactically skillful, Quantum Optics in Phase Space prepares students for their own research by presenting detailed derivations, many illustrations and a large set of workable problems at the end of each chapter. Often, the theoretical treatments are accompanied by the corresponding experiments. An exhaustive list of references provides a guide to the literature. Quantum Optics in Phase Space also serves advanced researchers as
Zonal-flow dynamics from a phase-space perspective
Ruiz, D. E.; Parker, J. B.; Shi, E. L.; Dodin, I. Y.
2017-10-01
The wave kinetic equation (WKE) describing drift-wave (DW) turbulence is widely used in the studies of zonal flows (ZFs) emerging from DW turbulence. However, this formulation neglects the exchange of enstrophy between DWs and ZFs and also ignores effects beyond the geometrical-optics (GO) limit. Here we present a new theory that captures both of these effects, while still treating DW quanta (``driftons'') as particles in phase space. In this theory, the drifton dynamics is described by an equation of the Wigner-Moyal type, which is analogous to the phase-space formulation of quantum mechanics. The ``Hamiltonian'' and the ``dissipative'' parts of the DW-ZF interactions are clearly identified. Moreover, this theory can be interpreted as a phase-space representation of the second-order cumulant expansion (CE2). In the GO limit, this formulation features additional terms missing in the traditional WKE that ensure conservation of the total enstrophy of the system, in addition to the total energy, which is the only conserved invariant in previous theories based on the traditional WKE. Numerical simulations are presented to illustrate the importance of these additional terms. Supported by the U.S. DOE through Contract Nos. DE-AC02-09CH11466 and DE-AC52-07NA27344, by the NNSA SSAA Program through DOE Research Grant No. DE-NA0002948, and by the U.S. DOD NDSEG Fellowship through Contract No. 32-CFR-168a.
DEFF Research Database (Denmark)
Dahl, Jens Peder; Varro, S.; Wolf, A.
2007-01-01
We derive explicit expressions for the Wigner function of wave functions in D dimensions which depend on the hyperradius-that is, of s waves. They are based either on the position or the momentum representation of the s wave. The corresponding Wigner function depends on three variables......: the absolute value of the D-dimensional position and momentum vectors and the angle between them. We illustrate these expressions by calculating and discussing the Wigner functions of an elementary s wave and the energy eigenfunction of a free particle....
Tertiary instability of zonal flows within the Wigner-Moyal formulation of drift turbulence
Zhu, Hongxuan; Ruiz, D. E.; Dodin, I. Y.
2017-10-01
The stability of zonal flows (ZFs) is analyzed within the generalized-Hasegawa-Mima model. The necessary and sufficient condition for a ZF instability, which is also known as the tertiary instability, is identified. The qualitative physics behind the tertiary instability is explained using the recently developed Wigner-Moyal formulation and the corresponding wave kinetic equation (WKE) in the geometrical-optics (GO) limit. By analyzing the drifton phase space trajectories, we find that the corrections proposed in Ref. to the WKE are critical for capturing the spatial scales characteristic for the tertiary instability. That said, we also find that this instability itself cannot be adequately described within a GO formulation in principle. Using the Wigner-Moyal equations, which capture diffraction, we analytically derive the tertiary-instability growth rate and compare it with numerical simulations. The research was sponsored by the U.S. Department of Energy.
Wigner function for twisted photons
Rigas, I.; Sánchez Soto, L. L.; Klimov, A. B.; Řeháček, J.; Hradil, Z.
2010-02-01
A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angles-angular momentum is presented, with special emphasis in the implications of rotational periodicity and angular-momentum discreteness.
Rogers, Fergus J. M.; Loos, Pierre-François
2017-01-01
Wigner crystals (WCs) are electronic phases peculiar to low-density systems, particularly in the uniform electron gas. Since its introduction in the early twentieth century, this model has remained essential to many aspects of electronic structure theory and condensed-matter physics. Although the (lowest-energy) ground-state WC (GSWC) has been thoroughly studied, the properties of excited-state WCs (ESWCs) are basically unknown. To bridge this gap, we present a well-defined procedure to obtain an entire family of ESWCs in a one-dimensional electron gas using a symmetry-broken mean-field approach. While the GSWC is a commensurate crystal (i.e., the number of density maxima equals the number of electrons), these ESWCs are incommensurate crystals exhibiting more or less maxima. Interestingly, they are lower in energy than the (uniform) Fermi fluid state. For some of these ESWCs, we have found asymmetrical band gaps, which would lead to anisotropic conductivity. These properties are associated with unusual characteristics in their electronic structure.
Longitudinal Phase Space Tomography with Space Charge
Hancock, S; Lindroos, M
2000-01-01
Tomography is now a very broad topic with a wealth of algorithms for the reconstruction of both qualitative and quantitative images. In an extension in the domain of particle accelerators, one of the simplest algorithms has been modified to take into account the non-linearity of large-amplitude synchrotron motion. This permits the accurate reconstruction of longitudinal phase space density from one-dimensional bunch profile data. The method is a hybrid one which incorporates particle tracking. Hitherto, a very simple tracking algorithm has been employed because only a brief span of measured profile data is required to build a snapshot of phase space. This is one of the strengths of the method, as tracking for relatively few turns relaxes the precision to which input machine parameters need to be known. The recent addition of longitudinal space charge considerations as an optional refinement of the code is described. Simplicity suggested an approach based on the derivative of bunch shape with the properties of...
Quantum mechanics in phase space
DEFF Research Database (Denmark)
Hansen, Frank
1984-01-01
A reformulation of quantum mechanics for a finite system is given using twisted multiplication of functions on phase space and Tomita's theory of generalized Hilbert algebras. Quantization of a classical observable h is achieved when the twisted exponential Exp0(-h) is defined as a tempered...
Eugene Paul Wigner's Nobel Prize
Kim, Y S
2016-01-01
In 1963, Eugene Paul Wigner was awarded the Nobel Prize in Physics for his contributions to the theory of the atomic nucleus and the elementary particles, particularly through the discovery and application of fundamental symmetry principles. There are no disputes about this statement. On the other hand, there still is a question of why the statement did not mention Wigner's 1939 paper on the Lorentz group, which was regarded by Wigner and many others as his most important contribution in physics. By many physicists, this paper was regarded as a mathematical exposition having nothing to do with physics. However, it has been more than one half century since 1963, and it is of interest to see what progress has been made toward understanding physical implications of this paper and its historical role in physics. Wigner in his 1963 paper defined the subgroups of the Lorentz group whose transformations do not change the four-momentum of a given particle, and he called them the little groups. Thus, Wigner's little g...
Phase space representation of quantum mechanics
DEFF Research Database (Denmark)
Henriksen, Niels Engholm; Billing, G. D.; Hansen, Flemming Yssing
1988-01-01
The accuracy of the Wigner propagation method is studied for stationary as well as non-stationary states of Morse oscillators. We investigate the possibility of improving the approach by introducing an effective potential. We find that the Wigner propagation method is accurate only for the ground...
Longitudinal phase space tomography with space charge
Directory of Open Access Journals (Sweden)
S. Hancock
2000-12-01
Full Text Available Tomography is now a very broad topic with a wealth of algorithms for the reconstruction of both qualitative and quantitative images. In an extension in the domain of particle accelerators, one of the simplest algorithms has been modified to take into account the nonlinearity of large-amplitude synchrotron motion. This permits the accurate reconstruction of longitudinal phase space density from one-dimensional bunch profile data. The method is a hybrid one which incorporates particle tracking. Hitherto, a very simple tracking algorithm has been employed because only a brief span of measured profile data is required to build a snapshot of phase space. This is one of the strengths of the method, as tracking for relatively few turns relaxes the precision to which input machine parameters need to be known. The recent addition of longitudinal space charge considerations as an optional refinement of the code is described. Simplicity suggested an approach based on the derivative of bunch shape with the properties of the vacuum chamber parametrized by a single value of distributed reactive impedance and by a geometrical coupling coefficient. This is sufficient to model the dominant collective effects in machines of low to moderate energy. In contrast to simulation codes, binning is not an issue since the profiles to be differentiated are measured ones. The program is written in Fortran 90 with high-performance Fortran extensions for parallel processing. A major effort has been made to identify and remove execution bottlenecks, for example, by reducing floating-point calculations and recoding slow intrinsic functions. A pointerlike mechanism which avoids the problems associated with pointers and parallel processing has been implemented. This is required to handle the large, sparse matrices that the algorithm employs. Results obtained with and without the inclusion of space charge are presented and compared for proton beams in the CERN protron synchrotron
Directory of Open Access Journals (Sweden)
Sadolah Nasiri
2008-02-01
Full Text Available In a previous work the concept of quantum potential is generalized into extended phase space (EPS for a particle in linear and harmonic potentials. It was shown there that in contrast to the Schrödinger quantum mechanics by an appropriate extended canonical transformation one can obtain the Wigner representation of phase space quantum mechanics in which the quantum potential is removed from dynamical equation. In other words, one still has the form invariance of the ordinary Hamilton-Jacobi equation in this representation. The situation, mathematically, is similar to the disappearance of the centrifugal potential in going from the spherical to the Cartesian coordinates. Here we show that the Husimi representation is another possible representation where the quantum potential for the harmonic potential disappears and the modified Hamilton-Jacobi equation reduces to the familiar classical form. This happens when the parameter in the Husimi transformation assumes a specific value corresponding to Q-function.
Phase-space quantum control; Quantenkontrolle im Zeit-Frequenz-Phasenraum
Energy Technology Data Exchange (ETDEWEB)
Fechner, Susanne
2008-08-06
The von Neumann-representation introduced in this thesis describes each laser pulse in a one-to-one manner as a sum of bandwidth-limited, Gaussian laser pulses centered around different points in phase space. These pulses can be regarded as elementary building blocks from which every single laser pulse can be constructed. The von Neumann-representation combines different useful properties for applications in quantum control. First, it is a one-to-one map between the degrees of freedom of the pulse shaper and the phase-space representation of the corresponding shaped laser pulse. In other words: Every possible choice of pulse shaper parameters corresponds to exactly one von Neumann-representation and vice versa. Moreover, since temporal and spectral structures become immediately sizable, the von Neumann-representation, as well as the Husimi- or the Wigner-representations, allows for an intuitive interpretation of the represented laser pulse. (orig.)
Chaotic eigenfunctions in phase space
Nonnenmacher, S
1997-01-01
We study individual eigenstates of quantized area-preserving maps on the 2-torus which are classically chaotic. In order to analyze their semiclassical behavior, we use the Bargmann-Husimi representations for quantum states, as well as their stellar parametrization, which encodes states through a minimal set of points in phase space (the constellation of zeros of the Husimi density). We rigorously prove that a semiclassical uniform distribution of Husimi densities on the torus entails a similar equidistribution for the corresponding constellations. We deduce from this property a universal behavior for the phase patterns of chaotic Bargmann eigenfunctions, which reminds of the WKB approximation for eigenstates of integrable systems (though in a weaker sense). In order to obtain more precise information on ``chaotic eigenconstellations", we then model their properties by ensembles of random states, generalizing former results on the 2-sphere to the torus geometry. This approach yields statistical predictions fo...
Passive longitudinal phase space linearizer
Directory of Open Access Journals (Sweden)
P. Craievich
2010-03-01
Full Text Available We report on the possibility to passively linearize the bunch compression process in electron linacs for the next generation x-ray free electron lasers. This can be done by using the monopole wakefields in a dielectric-lined waveguide. The optimum longitudinal voltage loss over the length of the bunch is calculated in order to compensate both the second-order rf time curvature and the second-order momentum compaction terms. Thus, the longitudinal phase space after the compression process is linearized up to a fourth-order term introduced by the convolution between the bunch and the monopole wake function.
An advective-spectral-mixed method for time-dependent many-body Wigner simulations
Xiong, Yunfeng; Shao, Sihong
2016-01-01
As a phase space language for quantum mechanics, the Wigner function approach bears a close analogy to classical mechanics and has been drawing growing attention, especially in simulating quantum many-body systems. However, deterministic numerical solutions have been almost exclusively confined to one-dimensional one-body systems and few results are reported even for one-dimensional two-body problems. This paper serves as the first attempt to solve the time-dependent many-body Wigner equation through a grid-based advective-spectral-mixed method. The main feature of the method is to resolve the linear advection in $(\\bm{x},t)$-space by an explicit three-step characteristic scheme coupled with the piecewise cubic spline interpolation, while the Chebyshev spectral element method in $\\bm k$-space is adopted for accurate calculation of the nonlocal pseudo-differential term. Not only the time step of the resulting method is not restricted by the usual CFL condition and thus a large time step is allowed, but also th...
Noncommutative phase spaces on Aristotle group
Directory of Open Access Journals (Sweden)
Ancille Ngendakumana
2012-03-01
Full Text Available We realize noncommutative phase spaces as coadjoint orbits of extensions of the Aristotle group in a two dimensional space. Through these constructions the momenta of the phase spaces do not commute due to the presence of a naturally introduced magnetic eld. These cases correspond to the minimal coupling of the momentum with a magnetic potential.
Experimental evidence for Wigner's tunneling time
Camus, Nicolas; Fechner, Lutz; Klaiber, Michael; Laux, Martin; Mi, Yonghao; Hatsagortsyan, Karen Z; Pfeifer, Thomas; Keitel, Christoph H; Moshammer, Robert
2016-01-01
Tunneling of a particle through a potential barrier remains one of the most remarkable quantum phenomena. Owing to advances in laser technology, electric fields comparable to those electrons experience in atoms are readily generated and open opportunities to dynamically investigate the process of electron tunneling through the potential barrier formed by the superposition of both laser and atomic fields. Attosecond-time and angstrom-space resolution of the strong laser-field technique allow to address fundamental questions related to tunneling, which are still open and debated: Which time is spent under the barrier and what momentum is picked up by the particle in the meantime? In this combined experimental and theoretical study we demonstrate that for strong-field ionization the leading quantum mechanical Wigner treatment for the time resolved description of tunneling is valid. We achieve a high sensitivity on the tunneling barrier and unambiguously isolate its effects by performing a differential study of t...
Construction of the Wigner Data Centre
2013-01-01
A remote extension of the CERN data centre has recently been inaugurated. Hosted at the Wigner Research Centre for Physics in Hungary, it provides extra computing power required to cover CERN’s needs. This video presents the construction of the Wigner Data Centre from initial demolishing work through to its completion and details the major technical characteristics of the Data Centre.
Energy Technology Data Exchange (ETDEWEB)
Cleary, Liam; Coffey, William T; Dowling, William J [Department of Electronic and Electrical Engineering, Trinity College, Dublin 2 (Ireland); Kalmykov, Yuri P [Laboratoire de Mathematiques et Physique, Universite de Perpignan Via Domitia, 52, Avenue de Paul Alduy, 66860 Perpignan Cedex (France); Titov, Serguey V, E-mail: kalmykov@univ-perp.fr [Institute of Radio Engineering and Electronics of the Russian Academy of Sciences, Vvedenskii Square 1, Fryazino, 141190 (Russian Federation)
2011-11-25
The dynamics of quantum Brownian particles in a cosine periodic potential are studied using the phase space formalism associated with the Wigner representation of quantum mechanics. Various kinetic phase space master equation models describing quantum Brownian motion in a potential are compared by evaluating the dynamic structure factor and escape rate from the differential recurrence relations generated by the models. The numerical solution is accomplished via matrix continued fractions in the manner customarily used for the classical Fokker-Planck equation. The results of numerical calculations of the escape rate from a well of the cosine potential are compared with those given analytically by the quantum-mechanical reaction rate theory solution of the Kramers turnover problem for a periodic potential, given by Georgievskii and Pollak (1994 Phys. Rev. E 49 5098), enabling one to appraise each model. (paper)
Wigner-Poisson statistics of topological transitions in a Josephson junction.
Beenakker, C W J; Edge, J M; Dahlhaus, J P; Pikulin, D I; Mi, Shuo; Wimmer, M
2013-07-19
The phase-dependent bound states (Andreev levels) of a Josephson junction can cross at the Fermi level if the superconducting ground state switches between even and odd fermion parity. The level crossing is topologically protected, in the absence of time-reversal and spin-rotation symmetry, irrespective of whether the superconductor itself is topologically trivial or not. We develop a statistical theory of these topological transitions in an N-mode quantum-dot Josephson junction by associating the Andreev level crossings with the real eigenvalues of a random non-Hermitian matrix. The number of topological transitions in a 2π phase interval scales as √[N], and their spacing distribution is a hybrid of the Wigner and Poisson distributions of random-matrix theory.
Wigner method dynamics in the interaction picture
DEFF Research Database (Denmark)
Møller, Klaus Braagaard; Dahl, Jens Peder; Henriksen, Niels Engholm
1994-01-01
The possibility of introducing an interaction picture in the semiclassical Wigner method is investigated. This is done with an interaction Picture description of the density operator dynamics as starting point. We show that the dynamics of the density operator dynamics as starting point. We show...... that the dynamics of the interaction picture Wigner function is solved by running a swarm of trajectories in the classical interaction picture introduced previously in the literature. Solving the Wigner method dynamics of collision processes in the interaction picture ensures that the calculated transition...... probabilities are unambiguous even when the asymptotic potentials are anharmonic. An application of the interaction picture Wigner method to a Morse oscillator interacting with a laser field is presented. The calculated transition probabilities are in good agreement with results obtained by a numerical...
Resonance controlled transport in phase space
Leoncini, Xavier; Vasiliev, Alexei; Artemyev, Anton
2018-02-01
We consider the mechanism of controlling particle transport in phase space by means of resonances in an adiabatic setting. Using a model problem describing nonlinear wave-particle interaction, we show that captures into resonances can be used to control transport in momentum space as well as in physical space. We design the model system to provide creation of a narrow peak in the distribution function, thus producing effective cooling of a sub-ensemble of the particles.
Wigner surmise for mixed symmetry classes in random matrix theory
Schierenberg, Sebastian; Bruckmann, Falk; Wettig, Tilo
2012-06-01
We consider the nearest-neighbor spacing distributions of mixed random matrix ensembles interpolating between different symmetry classes or between integrable and nonintegrable systems. We derive analytical formulas for the spacing distributions of 2×2 or 4×4 matrices and show numerically that they provide very good approximations for those of random matrices with large dimension. This generalizes the Wigner surmise, which is valid for pure ensembles that are recovered as limits of the mixed ensembles. We show how the coupling parameters of small and large matrices must be matched depending on the local eigenvalue density.
Quantum harmonic Brownian motion in a general environment: A modified phase-space approach
Energy Technology Data Exchange (ETDEWEB)
Yeh, Leehwa [Univ. of California, Berkeley, CA (United States). Dept. of Physics
1993-06-23
After extensive investigations over three decades, the linear-coupling model and its equivalents have become the standard microscopic models for quantum harmonic Brownian motion, in which a harmonically bound Brownian particle is coupled to a quantum dissipative heat bath of general type modeled by infinitely many harmonic oscillators. The dynamics of these models have been studied by many authors using the quantum Langevin equation, the path-integral approach, quasi-probability distribution functions (e.g., the Wigner function), etc. However, the quantum Langevin equation is only applicable to some special problems, while other approaches all involve complicated calculations due to the inevitable reduction (i.e., contraction) operation for ignoring/eliminating the degrees of freedom of the heat bath. In this dissertation, the author proposes an improved methodology via a modified phase-space approach which employs the characteristic function (the symplectic Fourier transform of the Wigner function) as the representative of the density operator. This representative is claimed to be the most natural one for performing the reduction, not only because of its simplicity but also because of its manifestation of geometric meaning. Accordingly, it is particularly convenient for studying the time evolution of the Brownian particle with an arbitrary initial state. The power of this characteristic function is illuminated through a detailed study of several physically interesting problems, including the environment-induced damping of quantum interference, the exact quantum Fokker-Planck equations, and the relaxation of non-factorizable initial states. All derivations and calculations axe shown to be much simplified in comparison with other approaches. In addition to dynamical problems, a novel derivation of the fluctuation-dissipation theorem which is valid for all quantum linear systems is presented.
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.
Phase space methods for degenerate quantum gases
Dalton, Bryan J; Barnett, Stephen M
2015-01-01
Recent experimental progress has enabled cold atomic gases to be studied at nano-kelvin temperatures, creating new states of matter where quantum degeneracy occurs - Bose-Einstein condensates and degenerate Fermi gases. Such quantum states are of macroscopic dimensions. This book presents the phase space theory approach for treating the physics of degenerate quantum gases, an approach already widely used in quantum optics. However, degenerate quantum gases involve massive bosonic and fermionic atoms, not massless photons. The book begins with a review of Fock states for systems of identical atoms, where large numbers of atoms occupy the various single particle states or modes. First, separate modes are considered, and here the quantum density operator is represented by a phase space distribution function of phase space variables which replace mode annihilation, creation operators, the dynamical equation for the density operator determines a Fokker-Planck equation for the distribution function, and measurable...
Using the Phase Space to Design Complexity
DEFF Research Database (Denmark)
Heinrich, Mary Katherine; Ayres, Phil
2016-01-01
Architecture that is responsive, adaptive, or interactive can contain active architectural elements or robotic sensor-actuator systems. The consideration of architectural robotic elements that utilize distributed control and distributed communication allows for self-organization, emergence...... it to the realm of computational design in architecture, specifically by considering the phase space and related concepts. We consider the scale and predictability of certain design characteristics, and originate the concept of a formation space extension to the phase space, for design to deal directly...... with materializations left by robot swarms or elements, rather than robots' internal states. We detail a case study examination of design methodology using the formation space concept for assessment and decision-making in the design of active architectural artifacts....
Grassmann phase space theory for fermions
Energy Technology Data Exchange (ETDEWEB)
Dalton, Bryan J. [Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne, Victoria, 3122 (Australia); Jeffers, John [Department of Physics, University of Strathclyde, Glasgow, G4 ONG (United Kingdom); Barnett, Stephen M. [School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)
2017-06-15
A phase space theory for fermions has been developed using Grassmann phase space variables which can be used in numerical calculations for cold Fermi gases and for large fermion numbers. Numerical calculations are feasible because Grassmann stochastic variables at later times are related linearly to such variables at earlier times via c-number stochastic quantities. A Grassmann field version has been developed making large fermion number applications possible. Applications are shown for few mode and field theory cases. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Identifying Phase Space Boundaries with Voronoi Tessellations
Debnath, Dipsikha; Kilic, Can; Kim, Doojin; Matchev, Konstantin T.; Yang, Yuan-Pao
2016-11-24
Determining the masses of new physics particles appearing in decay chains is an important and longstanding problem in high energy phenomenology. Recently it has been shown that these mass measurements can be improved by utilizing the boundary of the allowed region in the fully differentiable phase space in its full dimensionality. Here we show that the practical challenge of identifying this boundary can be solved using techniques based on the geometric properties of the cells resulting from Voronoi tessellations of the relevant data. The robust detection of such phase space boundaries in the data could also be used to corroborate a new physics discovery based on a cut-and-count analysis.
Quantum entropy production in phase space
Deffner, Sebastian
2014-03-01
A fluctuation theorem for the nonequilibrium entropy production in quantum phase space is derived, which enables the consistent thermodynamic description of arbitrary quantum systems, open and closed. The new treatment naturally generalizes classical results to the quantum domain. As an illustration the harmonic oscillator dragged through a thermal bath is solved numerically. Finally, the significance of the new approach is discussed in detail, and the phase space treatment is opposed to the two time energy measurement approach. We acknowledge financial support by a fellowship within the postdoc-program of the German Academic Exchange Service (DAAD, contract No D/11/40955) and from the National Science Foundation (USA) under grant DMR-1206971.
Noether symmetries in the phase space
Directory of Open Access Journals (Sweden)
Bogar Díaz
2014-09-01
Full Text Available The constants of motion of a mechanical system with a finite number of degrees of freedom are related to the variational symmetries of a Lagrangian constructed from the Hamiltonian of the original system. The configuration space for this Lagrangian is the phase space of the original system. The symmetries considered in this manner include transformations of the time and may not be canonical in the standard sense.
Zhou, Yimin; Zhou, Guoquan; Dai, Chaoqing; Ru, Guoyun
2015-03-01
Based on the Collins integral formula and the Hermite-Gaussian expansion of a Lorentz function, an analytical expression for the Wigner distribution function (WDF) of a Lorentz-Gauss vortex beam passing through a paraxial ABCD optical system is derived. The WDF properties of a Lorentz-Gauss vortex beam propagating in free space are also demonstrated. During propagation, the WDF pattern shrinks in the direction of the spatial frequency variables and elongates in the direction of the transverse spatial coordinates. With given the transverse spatial coordinates or the spatial frequency variables, the evolvement of the WDF of a Lorentz-Gauss vortex beam during propagation is examined in detail. To show the WDF application, the second-order moments of the WDF for a Lorentz-Gauss vortex beam in free space are also presented. This research exhibits the propagation properties of a Lorentz-Gauss vortex beam from the phase space.
Quantum melting of a two-dimensional Wigner crystal
Dolgopolov, V. T.
2017-10-01
The paper reviews theoretical predictions about the behavior of two-dimensional low-density electron systems at nearly absolute zero temperatures, including the formation of an electron (Wigner) crystal, crystal melting at a critical electron density, and transitions between crystal modifications in more complex (for example, two-layer) systems. The paper presents experimental results obtained from real two-dimensional systems in which the nonconducting (solid) state of the electronic system with indications of collective localization is actually realized. Experimental methods for detecting a quantum liquid–solid phase interface are discussed.
Chaotic systems in complex phase space
Indian Academy of Sciences (India)
Abstract. This paper examines numerically the complex classical trajectories of the kicked rotor and the double pendulum. Both of these systems exhibit a transition to chaos, and this feature is studied in complex phase space. Additionally, it is shown that the short-time and long-time behaviours of these two PT -symmetric ...
Chaotic systems in complex phase space
Indian Academy of Sciences (India)
This paper examines numerically the complex classical trajectories of the kicked rotor and the double pendulum. Both of these systems exhibit a transition to chaos, and this feature is studied in complex phase space. Additionally, it is shown that the short-time and long-time behaviours of these two P T -symmetric dynamical ...
Phase space diffusion in turbulent plasmas
DEFF Research Database (Denmark)
Pécseli, Hans
1990-01-01
Turbulent diffusion of charged test particles in electrostatic plasma turbulence is reviewed. Two different types of test particles can be distinguished. First passive particles which are subject to the fluctuating electric fields without themselves contributing to the local space charge. The sec......Turbulent diffusion of charged test particles in electrostatic plasma turbulence is reviewed. Two different types of test particles can be distinguished. First passive particles which are subject to the fluctuating electric fields without themselves contributing to the local space charge....... The second type are particles introduced at a prescribed phase space position at a certain time and which then self-consistently participate in the phase space dynamics of the turbulence. The latter "active" type of particles can be subject to an effective frictional force due to radiation of plasma waves....... In terms of these test particle types, two basically different problems can be formulated. One deals with the diffusion of a particle with respect to its point of release in phase space. Alternatively the relative diffusion between many, or just two, particles can be analyzed. Analytical expressions...
Thermodynamic Products in the Extended Phase Space
Pradhan, Parthapratim
2016-01-01
We have examined the thermodynamic properties of spherically symmetric charged-AdS black hole, charged AdS BH surrounded by quintessence and charged AdS BH in $f(R)$ gravity in the extended phase-space. Where the cosmological constant should be treated as thermodynamic pressure and its conjugate parameter as thermodynamic volume. Then they should behave as a analog of Van der Waal like systems. In the extended phase space we have calculated the \\emph{entropy product} and \\emph{thermodynamic volume product} of all horizons. The mass(or enthalpy) independent nature of the said products signals they are "universal" quantities. Various types of pictorial diagram of the specific heat is given. The divergence of the specific heat indicates that the second order phase transition occurs under certain condition.
Many-Body Quantum Spin Dynamics with Monte Carlo Trajectories on a Discrete Phase Space
Directory of Open Access Journals (Sweden)
J. Schachenmayer
2015-02-01
Full Text Available Interacting spin systems are of fundamental relevance in different areas of physics, as well as in quantum information science and biology. These spin models represent the simplest, yet not fully understood, manifestation of quantum many-body systems. An important outstanding problem is the efficient numerical computation of dynamics in large spin systems. Here, we propose a new semiclassical method to study many-body spin dynamics in generic spin lattice models. The method is based on a discrete Monte Carlo sampling in phase space in the framework of the so-called truncated Wigner approximation. Comparisons with analytical and numerically exact calculations demonstrate the power of the technique. They show that it correctly reproduces the dynamics of one- and two-point correlations and spin squeezing at short times, thus capturing entanglement. Our results open the possibility to study the quantum dynamics accessible to recent experiments in regimes where other numerical methods are inapplicable.
The Quantum Space Phase Transitions for Particles and Force Fields
Chung D.-Y.; Krasnoholovets V.
2006-01-01
We introduce a phenomenological formalism in which the space structure is treated in terms of attachment space and detachment space. Attachment space attaches to an object, while detachment space detaches from the object. The combination of these spaces results in three quantum space phases: binary partition space, miscible space and binary lattice space. Binary lattice space consists of repetitive units of alternative attachment space and detachment spac...
Space market model development project, phase 3
Bishop, Peter C.; Hamel, Gary P.
1989-01-01
The results of a research project investigating information needs for space commercialization is described. The Space Market Model Development Project (SMMDP) was designed to help NASA identify the information needs of the business community and to explore means to meet those needs. The activity of the SMMDP is reviewed and a report of its operation via three sections is presented. The first part contains a brief historical review of the project since inception. The next part reports results of Phase 3, the most recent stage of activity. Finally, overall conclusions and observations based on the SMMDP research results are presented.
Phase transitions in de Sitter space
Directory of Open Access Journals (Sweden)
Alexander Vilenkin
1983-10-01
Full Text Available An effective potential in de Sitter space is calculated for a model of two interacting scalar fields in one-loop approximation and in a self-consistent approximation which takes into account an infinite set of diagrams. Various approaches to renormalization in de Sitter space are discussed. The results are applied to analyze the phase transition in the Hawking-Moss version of the inflationary universe scenario. Requiring that inflation is sufficiently large, we derive constraints on the parameters of the model.
Wigner particle theory and local quantum physics
Energy Technology Data Exchange (ETDEWEB)
Fassarella, Lucio; Schroer, Bert [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]. E-mail: fassarel@cbpf.br; schroer@cbpf.br
2002-01-01
Wigner's irreducible positive energy representations of the Poincare group are often used to give additional justifications for the Lagrangian quantization formalism of standard QFT. Here we study another more recent aspect. We explain in this paper modular concepts by which we are able to construct the local operator algebras for all standard positive energy representations directly without going through field coordinations. In this way the artificial emphasis on Lagrangian field coordinates is avoided from the very beginning. These new concepts allow to treat also those cases of 'exceptional' Wigner representations associated with anyons and the famous Wigner spin tower which have remained inaccessible to Lagrangian quantization. Together with the d=1+1 factorizing models (whose modular construction has been studied previously), they form an interesting family of theories with a rich vacuum-polarization structure (but no on shell real particle creation) to which the modular methods can be applied for their explicit construction. We explain and illustrate the algebraic strategy of this construction. We also comment on possibilities of formulating the Wigner theory in a setting of a noncommutativity. (author)
Wigner's Semicircle Law and Free Independence
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 14; Issue 10. Wigner's Semicircle Law and Free Independence. B V Rajarama Bhat. General Article Volume 14 Issue 10 October 2009 pp 970-977. Fulltext. Click here to view fulltext PDF. Permanent link:
Entanglement versus negative domains of Wigner functions
DEFF Research Database (Denmark)
Dahl, Jens Peder; Mack, H.; Wolf, A.
2006-01-01
We show that s waves, that is wave functions that only depend on a hyperradius, are entangled if and only if the corresponding Wigner functions exhibit negative domains. We illustrate this feature using a special class of s waves which allows us to perform the calculations analytically. This class...
Relativistic transformation of phase-space distributions
Directory of Open Access Journals (Sweden)
R. A. Treumann
2011-07-01
Full Text Available We investigate the transformation of the distribution function in the relativistic case, a problem of interest in plasma when particles with high (relativistic velocities come into play as for instance in radiation belt physics, in the electron-cyclotron maser radiation theory, in the vicinity of high-Mach number shocks where particles are accelerated to high speeds, and generally in solar and astrophysical plasmas. We show that the phase-space volume element is a Lorentz constant and construct the general particle distribution function from first principles. Application to thermal equilibrium lets us derive a modified version of the isotropic relativistic thermal distribution, the modified Jüttner distribution corrected for the Lorentz-invariant phase-space volume element. Finally, we discuss the relativistic modification of a number of plasma parameters.
Phase Space Invertible Asynchronous Cellular Automata
Directory of Open Access Journals (Sweden)
Simon Wacker
2012-08-01
Full Text Available While for synchronous deterministic cellular automata there is an accepted definition of reversibility, the situation is less clear for asynchronous cellular automata. We first discuss a few possibilities and then investigate what we call phase space invertible asynchronous cellular automata in more detail. We will show that for each Turing machine there is such a cellular automaton simulating it, and that it is decidable whether an asynchronous cellular automaton has this property or not, even in higher dimensions.
Entropy production in continuous phase space systems
Luposchainsky, David; Hinrichsen, Haye
2013-01-01
We propose an alternative method to compute the entropy production of a classical underdamped nonequilibrium system in a continuous phase space. This approach has the advantage that it is not necessary to distinguish between even and odd-parity variables. We show that the method leads to the same local entropy production as in previous studies while the differential entropy production along a stochastic trajectory turns out to be different. This demonstrates that the differential entropy prod...
Periodic orbits and TDHF phase space structure
Energy Technology Data Exchange (ETDEWEB)
Hashimoto, Yukio; Iwasawa, Kazuo [Tsukuba Univ., Ibaraki (Japan). Inst. of Physics; Tsukuma, Hidehiko; Sakata, Fumihiko
1998-03-01
The collective motion of atomic nuclei is closely coupled with the motion of nucleons, therefore, it is nonlinear, and the contents of the motion change largely with the increase of its amplitude. As the framework which describes the collective motion accompanied by the change of internal structure, time-dependent Hurtley Fock (TDHF) method is suitable. At present, the authors try to make the method for studying the large region structure in quantum system by utilizing the features of the TDHF phase space. The studies made so far are briefed. In this report, the correspondence of the large region patterns appearing in the band structure chart of three-level model with the periodic orbit group in the TDHF phase space is described. The Husimi function is made, and it possesses the information on the form of respective corresponding intrinsic state. The method of making the band structure chart is explained. There are three kinds of the tendency in the intrinsic state group. The E-T charts are made for the band structure charts to quantitatively express the large region tendency. The E-T chart and the T{sub r}-T chart are drawn for a selected characteristic orbit group. It became to be known that the large region properties of the quantum intrinsic state group of three-level model can be forecast by examining the properties of the periodic orbit group in the TDHF phase space. (K.I.)
Dissipative fragmentation in a phase space approach
Energy Technology Data Exchange (ETDEWEB)
Adorno, A.; Di Toro, M.; Bonasera, A.; Gregoire, C.; Gulminelli, F.
Semi-classical approaches have evidenced the role of one and two-body dissipation in nucleus-nucleus collisions. On the other hand, a substantial energy dissipation and some angular momentum transfer have been observed at moderate energy where a fragmentation process is the dominant reaction mechanism. In order to analyse main features of these reactions, we developed a phenomenological model taking into account phase space constraints. The transition between deep inelastic collisions and abrasion-like fragmentation is described and a general agreement with available data is found.
Phase space structures governing reaction dynamics in rotating molecules
Ciftci, Unver; Waalkens, Holger
Recently, the phase space structures governing reaction dynamics in Hamiltonian systems have been identified and algorithms for their explicit construction have been developed. These phase space structures are induced by saddle type equilibrium points which are characteristic for reaction type
On marginalization of phase-space distribution functions
Włodarz, Joachim J.
1999-12-01
We discuss marginalization procedures based on integration of quantum phase-space distribution functions over a family of phase-space manifolds. We show that under some conditions the resulting marginals are always nonnegative.
Space Transportation Engine Program (STEP), phase B
1990-01-01
The Space Transportation Engine Program (STEP) Phase 2 effort includes preliminary design and activities plan preparation that will allow smooth and time transition into a Prototype Phase and then into Phases 3, 4, and 5. A Concurrent Engineering approach using Total Quality Management (TQM) techniques, is being applied to define an oxygen-hydrogen engine. The baseline from Phase 1/1' studies was used as a point of departure for trade studies and analyses. Existing STME system models are being enhanced as more detailed module/component characteristics are determined. Preliminary designs for the open expander, closed expander, and gas generator cycles were prepared, and recommendations for cycle selection made at the Design Concept Review (DCR). As a result of July '90 DCR, and information subsequently supplied to the Technical Review Team, a gas generator cycle was selected. Results of the various Advanced Development Programs (ADP's) for the Advanced Launch Systems (ALS) were contributive to this effort. An active vehicle integration effort is supplying the NASA, Air Force, and vehicle contractors with engine parameters and data, and flowing down appropriate vehicle requirements. Engine design and analysis trade studies are being documented in a data base that was developed and is being used to organize information. To date, seventy four trade studies were input to the data base.
Experimental Observations of Ion Phase-Space Vortices
DEFF Research Database (Denmark)
Pécseli, Hans; Armstrong, R. J.; Trulsen, J.
1981-01-01
Experimental observations of ion phase-space vortices are reported. The ion phase-space vortices form in the region of heated ions behind electrostatic ion acoustic shocks. The results are in qualitative agreement with numerical and analytic studies.......Experimental observations of ion phase-space vortices are reported. The ion phase-space vortices form in the region of heated ions behind electrostatic ion acoustic shocks. The results are in qualitative agreement with numerical and analytic studies....
Visualization of Thomas–Wigner Rotations
Directory of Open Access Journals (Sweden)
Georg Beyerle
2017-11-01
Full Text Available It is well known that a sequence of two non-collinear Lorentz boosts (pure Lorentz transformations does not correspond to a Lorentz boost, but involves a spatial rotation, the Wigner or Thomas–Wigner rotation. We visualize the interrelation between this rotation and the relativity of distant simultaneity by moving a Born-rigid object on a closed trajectory in several steps of uniform proper acceleration. Born-rigidity implies that the stern of the boosted object accelerates faster than its bow. It is shown that at least five boost steps are required to return the object’s center to its starting position, if in each step the center is assumed to accelerate uniformly and for the same proper time duration. With these assumptions, the Thomas–Wigner rotation angle depends on a single parameter only. Furthermore, it is illustrated that accelerated motion implies the formation of a “frame boundary”. The boundaries associated with the five boosts constitute a natural barrier and ensure the object’s finite size.
Violent relaxation in phase-space
Bindoni, D.; Secco, L.
2008-05-01
The problem of violent relaxation mechanism in collisionless systems from the point of view of the distribution function (DF) in μ-space is reviewed. The literature run starts from the seminal paper of Lynden-Bell [Lynden-Bell, D., 1967. MNRAS 136, 101] and is closed by that of the same author [Arad, I., Lynden-Bell, D., 2005. MNRAS 361, 385]. After some introductive sections on the stellar dynamical equilibria and on the Shannon's information theory, the different approaches follow each accompanied with its criticism on the previous works. Different coarse-grained DFs proposed by different authors have been taken into account. It appears that for a collisionless gas of a unique mass specie there is not significant discrepancies among the different approaches which converge to the same DF at the end of relaxation process. The main problem is to avoid the non observed mass segregation in the case of multi-species composition, e.g., in a star-dominated galaxy component. On this topic the results are very different and are depending on the shape and size one chooses for μ-space tiles. A great effort has been spent into the visualization of the different partitions in phase-space in order to understand clearly from what the differences arise.
The Quantum Space Phase Transitions for Particles and Force Fields
Directory of Open Access Journals (Sweden)
Chung D.-Y.
2006-07-01
Full Text Available We introduce a phenomenological formalism in which the space structure is treated in terms of attachment space and detachment space. Attachment space attaches to an object, while detachment space detaches from the object. The combination of these spaces results in three quantum space phases: binary partition space, miscible space and binary lattice space. Binary lattice space consists of repetitive units of alternative attachment space and detachment space. In miscible space, attachment space is miscible to detachment space, and there is no separation between attachment space and detachment spaces. In binary partition space, detachment space and attachment space are in two separat continuous regions. The transition from wavefunction to the collapse of wavefuction under interference becomes the quantum space phase transition from binary lattice space to miscible space. At extremely conditions, the gauge boson force field undergoes a quantum space phase transition to a "hedge boson force field", consisting of a "vacuum" core surrounded by a hedge boson shell, like a bubble with boundary.
The Wigner-Yanase entropy is not subadditive
DEFF Research Database (Denmark)
Hansen, Frank
2007-01-01
Wigner and Yanase introduced in 1963 the Wigner-Yanase entropy defined as minus the skew information of a state with respect to a conserved observable. They proved that the Wigner-Yanase entropy is a concave function in the state and conjectured that it is subadditive with respect...... to the aggregation of possibly interacting subsystems. While this turned out to be true for the quantum-mechanical entropy, we negate the conjecture for the Wigner-Yanase entropy by providing a counter example....
May-Wigner transition in large random dynamical systems
Ipsen, J. R.
2017-09-01
We consider stability in a class of random non-linear dynamical systems characterised by a relaxation rate together with a Gaussian random vector field which is white-in-time and spatial homogeneous and isotropic. We will show that in the limit of large dimension there is a stability-complexity phase transition analogue to the so-called May-Wigner transition known from linear models. Our approach uses an explicit derivation of a stochastic description of the finite-time Lyapunov exponents. These exponents are given as a system of coupled Brownian motions with hyperbolic repulsion called geometric Dyson Brownian motions. We compare our results with known models from the literature.
Phase Space Reduction of Star Products on Cotangent Bundles.
Kowalzig, N.; Neumaier, N.; Pflaum, M.
2005-01-01
In this paper we construct star products on Marsden-Weinstein reduced spaces in case both the original phase space and the reduced phase space are (symplectomorphic to) cotangent bundles. Under the assumption that the original cotangent bundle $T^*Q$ carries a symplectic structure of form
Bertrand systems and their phase space
Directory of Open Access Journals (Sweden)
O. A. Zagryadskij
2014-01-01
Full Text Available Consider a pair (S, V , where S is a two-dimensional surface of revolution without equators, i.e. cylinder equipped Riemannian metric of revolution, V is a central potential on S such that it keeps constant when the group of rotation acts. Also consider central potentials acting on the surfaces equipped Pseudoriemannian metric of revolution. Lets select Bertrand pairs in the set of all considered pairs | the potential has to be locking, i.e. under the influence of it all bounded orbits must be closed. Such dynamical systems are Hamiltonian ones possessed four-dimensional phase space. And one could represent Bertand pairs as five-parametric set, three parameters define the inner product of the manifold, other two define potential. It is proved that only generalized law of universal gravitation and the generalized oscillator Hook law could be locking.It is well-known that in case of closed orbit the period of moving depends on the full energy, but not depends on angular momentum (classical Gordon's theorem; in this paper we established the explicit form of this relation for Bertrand systems. In case of nonbounded orbits we calculated full time of moving, noted the infinite cases, and derived the fullness of corresponding phase flows, i.e. whether time-parameter could be continued to infinitely on the integral curves of Hamiltonian vector field of energy.We show, thatBertrand systemsin pseudoriemannian case weren't integrable by the Liouville| Arnold theorem, however the connected components of regular Liouvill folia of two first integrals energy and angular momentum stayed either torii or cylinders. We proved any folia of the foliation could be either circle or torus or cylinder or pair of cylinders. Also we constructed bifurcation diagrams of momentum map, all the diagrams is divided into areas corresponding to different types of Liouville folii. Finally it was discovered whether flows were full or not.
Space storm as a phase transition
Wanliss, J. A.; Dobias, P.
2007-04-01
Fluctuations of the SYM-H index were analyzed for several space storms preceded by more than a week of extremely quiet conditions to establish that there was a rapid and unidirectional change in the Hurst scaling exponent at the time of storm onset. That is, the transition was accompanied by the specific signature of a rapid unidirectional change in the temporal fractal scaling of fluctuations in SYM-H, signaling the formation of a new dynamical phase (or mode) which was considerably more organized than the background state. We compare these results to a model of multifractional Brownian motion and suggest that the relatively sudden change from a less correlated to a more correlated pattern of multiscale fluctuations at storm onset can be characterized in terms of nonequilibrium dynamical phase transitions. The results show that a dynamical transition in solar wind VB is correlated with the storm onset for intense storms, suggesting that the dynamical transition observed in SYM-H is of external solar wind origin, rather than internal magnetospheric origin. However, some results showed a dynamical transition in solar wind scaling exponents not matched by similar transitions in SYM-H. In other instances, we observed some small storms where there was a strong dynamical transition in SYM-H without similar changes in the VB scaling statistics, suggesting that changes were due to internal magnetospheric processes. In summary, the results for intense storms points to the solar wind as being responsible for providing the scale free properties in the SYM-H fluctuations but the evidence for small storms clearly limit the importance of the solar wind fluctuations; their interaction is more complex than simple causality.
Phase Space Cell in Nonextensive Classical Systems
Directory of Open Access Journals (Sweden)
Piero Quarati
2003-06-01
Full Text Available Abstract: We calculate the phase space volume ÃŽÂ© occupied by a nonextensive system of N classical particles described by an equilibrium (or steady-state, or long-term stationary state of a nonequilibrium system distribution function, which slightly deviates from Maxwell-Boltzmann (MB distribution in the high energy tail. We explicitly require that the number of accessible microstates does not change respect to the extensive MB case. We also derive, within a classical scheme, an analytical expression of the elementary cell that can be seen as a macrocell, different from the third power of Planck constant. Thermodynamic quantities like entropy, chemical potential and free energy of a classical ideal gas, depending on elementary cell, are evaluated. Considering the fractional deviation from MB distribution we can deduce a physical meaning of the nonextensive parameter q of the Tsallis nonextensive thermostatistics in terms of particle correlation functions (valid at least in the case, discussed in this work, of small deviations from MB standard case.
Space market model development project, phase 2
Bishop, Peter C.
1988-01-01
The results of the prototype operations of the Space Business Information Center are presented. A clearinghouse for space business information for members of the U.S. space industry composed of public, private, and academic sectors was conducted. Behavioral and evaluation statistics were recorded from the clearinghouse and the conclusions from these statistics are presented. Business guidebooks on major markets in space business are discussed. Proprietary research and briefings for firms and agencies in the space industry are also discussed.
Overview of Phase Space Manipulations of Relativistic Electron Beams
Energy Technology Data Exchange (ETDEWEB)
Xiang, Dao; /SLAC
2012-08-31
Phase space manipulation is a process to rearrange beam's distribution in 6-D phase space. In this paper, we give an overview of the techniques for tailoring beam distribution in 2D, 4D, and 6D phase space to meet the requirements of various applications. These techniques become a new focus of accelerator physics R&D and very likely these advanced concepts will open up new opportunities in advanced accelerators and the science enabled by them.
Liu, Jian
2011-05-21
We show two more approaches for generating trajectory-based dynamics in the phase space formulation of quantum mechanics: "equilibrium continuity dynamics" (ECD) in the spirit of the phase space continuity equation in classical mechanics, and "equilibrium Hamiltonian dynamics" (EHD) in the spirit of the Hamilton equations of motion in classical mechanics. Both ECD and EHD can recover exact thermal correlation functions (of even nonlinear operators, i.e., nonlinear functions of position or momentum operators) in the classical, high temperature, and harmonic limits. Both ECD and EHD conserve the quasi-probability within the infinitesimal volume dx(t)dp(t) around the phase point (x(t), p(t)) along the trajectory. Numerical tests of both approaches in the Wigner phase space have been made for two strongly anharmonic model problems and a double well system, for each potential auto-correlation functions of both linear and nonlinear operators have been calculated. The results suggest EHD and ECD are two additional potential useful approaches for describing quantum effects for complex systems in condense phase. © 2011 American Institute of Physics.
Phase-space topography characterization of nonlinear ultrasound waveforms.
Dehghan-Niri, Ehsan; Al-Beer, Helem
2018-03-01
Fundamental understanding of ultrasound interaction with material discontinuities having closed interfaces has many engineering applications such as nondestructive evaluation of defects like kissing bonds and cracks in critical structural and mechanical components. In this paper, to analyze the acoustic field nonlinearities due to defects with closed interfaces, the use of a common technique in nonlinear physics, based on a phase-space topography construction of ultrasound waveform, is proposed. The central idea is to complement the "time" and "frequency" domain analyses with the "phase-space" domain analysis of nonlinear ultrasound waveforms. A nonlinear time series method known as pseudo phase-space topography construction is used to construct equivalent phase-space portrait of measured ultrasound waveforms. Several nonlinear models are considered to numerically simulate nonlinear ultrasound waveforms. The phase-space response of the simulated waveforms is shown to provide different topographic information, while the frequency domain shows similar spectral behavior. Thus, model classification can be substantially enhanced in the phase-space domain. Experimental results on high strength aluminum samples show that the phase-space transformation provides a unique detection and classification capabilities. The Poincaré map of the phase-space domain is also used to better understand the nonlinear behavior of ultrasound waveforms. It is shown that the analysis of ultrasound nonlinearities is more convenient and informative in the phase-space domain than in the frequency domain. Copyright © 2017 Elsevier B.V. All rights reserved.
Incorporation of Duffing Oscillator and Wigner-Ville Distribution in Traffic Flow Prediction
Directory of Open Access Journals (Sweden)
Anamarija L. Mrgole
2017-02-01
Full Text Available The main purpose of this study was to investigate the use of various chaotic pattern recognition methods for traffic flow prediction. Traffic flow is a variable, dynamic and complex system, which is non-linear and unpredictable. The emergence of traffic flow congestion in road traffic is estimated when the traffic load on a specific section of the road in a specific time period is close to exceeding the capacity of the road infrastructure. Under certain conditions, it can be seen in concentrating chaotic traffic flow patterns. The literature review of traffic flow theory and its connection with chaotic features implies that this kind of method has great theoretical and practical value. Researched methods of identifying chaos in traffic flow have shown certain restrictions in their techniques but have suggested guidelines for improving the identification of chaotic parameters in traffic flow. The proposed new method of forecasting congestion in traffic flow uses Wigner-Ville frequency distribution. This method enables the display of a chaotic attractor without the use of reconstruction phase space.
Orr, Lindsay; Hernández de la Peña, Lisandro; Roy, Pierre-Nicholas
2017-06-01
A derivation of quantum statistical mechanics based on the concept of a Feynman path centroid is presented for the case of generalized density operators using the projected density operator formalism of Blinov and Roy [J. Chem. Phys. 115, 7822-7831 (2001)]. The resulting centroid densities, centroid symbols, and centroid correlation functions are formulated and analyzed in the context of the canonical equilibrium picture of Jang and Voth [J. Chem. Phys. 111, 2357-2370 (1999)]. The case where the density operator projects onto a particular energy eigenstate of the system is discussed, and it is shown that one can extract microcanonical dynamical information from double Kubo transformed correlation functions. It is also shown that the proposed projection operator approach can be used to formally connect the centroid and Wigner phase-space distributions in the zero reciprocal temperature β limit. A Centroid Molecular Dynamics (CMD) approximation to the state-projected exact quantum dynamics is proposed and proven to be exact in the harmonic limit. The state projected CMD method is also tested numerically for a quartic oscillator and a double-well potential and found to be more accurate than canonical CMD. In the case of a ground state projection, this method can resolve tunnelling splittings of the double well problem in the higher barrier regime where canonical CMD fails. Finally, the state-projected CMD framework is cast in a path integral form.
Cosmology with galaxy cluster phase spaces
Stark, Alejo; Miller, Christopher J.; Huterer, Dragan
2017-07-01
We present a novel approach to constrain accelerating cosmologies with galaxy cluster phase spaces. With the Fisher matrix formalism we forecast constraints on the cosmological parameters that describe the cosmological expansion history. We find that our probe has the potential of providing constraints comparable to, or even stronger than, those from other cosmological probes. More specifically, with 1000 (100) clusters uniformly distributed in the redshift range 0 ≤z ≤0.8 , after applying a conservative 80% mass scatter prior on each cluster and marginalizing over all other parameters, we forecast 1 σ constraints on the dark energy equation of state w and matter density parameter ΩM of σw=0.138 (0.431 ) and σΩM=0.007(0.025 ) in a flat universe. Assuming 40% mass scatter and adding a prior on the Hubble constant we can achieve a constraint on the Chevallier-Polarski-Linder parametrization of the dark energy equation of state parameters w0 and wa with 100 clusters in the same redshift range: σw 0=0.191 and σwa=2.712. Dropping the assumption of flatness and assuming w =-1 we also attain competitive constraints on the matter and dark energy density parameters: σΩ M=0.101 and σΩ Λ=0.197 for 100 clusters uniformly distributed in the range 0 ≤z ≤0.8 after applying a prior on the Hubble constant. We also discuss various observational strategies for tightening constraints in both the near and far future.
Phase-space treatment of the driven quantum harmonic oscillator
Indian Academy of Sciences (India)
2017-02-22
Feb 22, 2017 ... Phase-space quantum mechanics; coherent states; harmonic oscillator; Husimi distribution; cross- ... is the Weyl operator assigned to the phase-space ...... formulae used in this work. The Hermite polynomials satisfy the following relations: 1. [19, Section 5.6.4],. Hη(y + σ) = η. ∑ k=0. ( η k. ) Hk(y)(2σ)η−k. = η.
On phase-space representations of quantum mechanics using ...
Indian Academy of Sciences (India)
A phase-space formulation of quantum mechanics is proposed by constructing two representations (identified as p q and q p ) in terms of the Glauber coherent states, in which phase-space wave functions (probability amplitudes) play the central role, and position q and momentum p are treated on equal footing. After finding ...
Fault diagnosis technology based on Wigner-Ville distribution in power electronics circuit
Rongjie, Wang; Yiju, Zhan; Meiqian, Chen; Haifeng, Zhou
2011-09-01
Based on Wigner-Ville distribution similarity, a method of fault diagnosis is proposed for power electronics circuits. After setting up the module time-frequency matrices of Wigner-Ville distribution for all fault signals, the similarities between the module time-frequency matrices of the fault signal and the former standard are then calculated, thus arriving at the diagnosis according to the principle of maximum similarity. The simulation result of fault diagnosis of a thyristor in a three-phase full-bridge-controlled rectifier shows that the method can accurately identify the fault types as well as the location of the fault elements for power electronics circuits, and it has an excellent performance for noise robustness and calculation complexity. Therefore, it is quite practically valuable in the solution to the fault problems for power electronics circuits.
Time-Frequency (Wigner Analysis of Linear and Nonlinear Pulse Propagation in Optical Fibers
Directory of Open Access Journals (Sweden)
José Azaña
2005-06-01
Full Text Available Time-frequency analysis, and, in particular, Wigner analysis, is applied to the study of picosecond pulse propagation through optical fibers in both the linear and nonlinear regimes. The effects of first- and second-order group velocity dispersion (GVD and self-phase modulation (SPM are first analyzed separately. The phenomena resulting from the interplay between GVD and SPM in fibers (e.g., soliton formation or optical wave breaking are also investigated in detail. Wigner analysis is demonstrated to be an extremely powerful tool for investigating pulse propagation dynamics in nonlinear dispersive systems (e.g., optical fibers, providing a clearer and deeper insight into the physical phenomena that determine the behavior of these systems.
Wigner and Huntington: the long quest for metallic hydrogen
Nellis, W. J.
2013-06-01
In 1935, Wigner and Huntington (WH) predicted that at a density D Met=0.62 mole H/cm3, 'very low temperatures', and a pressure greater than 25 GPa, body-centered cubic H2 would undergo an isostructural phase transition directly to H with an associated insulator-metal transition (IMT). WH also predicted an H2 structure type that might occur if the simple H2/H dissociative IMT does not exist: 'It is possible … that a layer-like lattice … is obtainable under high pressure'. In 1991, Ashcroft predicted that the 'geometric and dynamic nature of the (H-H) pairing', possibly in a layered graphite-like structure, would substantially impede achieving metallic H2. In 1996, metallic fluid H was made under dynamic compression at 0.64 mole H/cm3, 140 GPa and T/T F≪1, where T F is Fermi temperature. In 2012, a layer-like lattice, called Phase IV, was discovered above ∼220 GPa static pressure. Phase IV is insulating and possibly semi-metallic up to ∼360 GPa, above which it has been predicted to become metallic. This paper is a historical perspective - a comparison of WH's predictions with recent dynamic, static and theoretical high pressure results. WH did extremely well.
Real-space Berry phases: Skyrmion soccer (invited)
Energy Technology Data Exchange (ETDEWEB)
Everschor-Sitte, Karin, E-mail: karin@physics.utexas.edu; Sitte, Matthias [The University of Texas at Austin, Department of Physics, 2515 Speedway, Austin, Texas 78712 (United States)
2014-05-07
Berry phases occur when a system adiabatically evolves along a closed curve in parameter space. This tutorial-like article focuses on Berry phases accumulated in real space. In particular, we consider the situation where an electron traverses a smooth magnetic structure, while its magnetic moment adjusts to the local magnetization direction. Mapping the adiabatic physics to an effective problem in terms of emergent fields reveals that certain magnetic textures, skyrmions, are tailormade to study these Berry phase effects.
Real-space Berry phases: Skyrmion soccer (invited)
Everschor-Sitte, Karin; Sitte, Matthias
2014-05-01
Berry phases occur when a system adiabatically evolves along a closed curve in parameter space. This tutorial-like article focuses on Berry phases accumulated in real space. In particular, we consider the situation where an electron traverses a smooth magnetic structure, while its magnetic moment adjusts to the local magnetization direction. Mapping the adiabatic physics to an effective problem in terms of emergent fields reveals that certain magnetic textures, skyrmions, are tailormade to study these Berry phase effects.
Schrodinger Equation and Phase Space in Quantum Mechanics
Kim, Kiyoung
1997-01-01
Using classical statistics, Schrodinger equation in quantum mechanics is derived from complex space model. Phase-space probability amplitude, that can be defined on classical point of view, has connections to probability amplitude in internal space and to wave function in quantum mechanics. In addition, the physical entity of wave function in quantum mechanics is confirmed once again.
Order and chaos in quantum irregular scattering Wigner's time delay
Eckhardt, B
1993-01-01
Abstract: Recent developments in the semiclassical analysis of chaotic systems are reviewed and illustrated for Wigner's time delay in elastic scattering of a point particle from three disks in the plane. The convergence of the cycle expanded periodic orbit expression for Wigners time delay is demonstrated. Different regimes in form factor (the Fourier transform of the two point correlation function) of the semiclassical time delay are identified and their relation to Berry's semiclassical theory of the spectral rigidity are discussed.
Reading Neural Encodings using Phase Space Methods
Abarbanel, Henry D. I.; Tumer, Evren C.
2003-01-01
Environmental signals sensed by nervous systems are often represented in spike trains carried from sensory neurons to higher neural functions where decisions and functional actions occur. Information about the environmental stimulus is contained (encoded) in the train of spikes. We show how to "read" the encoding using state space methods of nonlinear dynamics. We create a mapping from spike signals which are output from the neural processing system back to an estimate of the analog input sig...
Explaining Gibbsean phase space to second year students
Energy Technology Data Exchange (ETDEWEB)
Vesely, Franz J [Institute of Experimental Physics, University of Vienna (Austria)
2005-03-01
A new approach to teaching introductory statistical physics is presented. We recommend making extensive use of the fact that even systems with a very few degrees of freedom may display chaotic behaviour. This permits a didactic 'bottom-up' approach, starting out with toy systems whose phase space may be depicted on a screen or blackboard, then proceeding to ever higher dimensions in Gibbsean phase space.
Group theoretical construction of planar noncommutative phase spaces
Energy Technology Data Exchange (ETDEWEB)
Ngendakumana, Ancille, E-mail: nancille@yahoo.fr; Todjihoundé, Leonard, E-mail: leonardt@imsp.uac.org [Institut de Mathématiques et des Sciences Physiques (IMSP), Porto-Novo (Benin); Nzotungicimpaye, Joachim, E-mail: kimpaye@kie.ac.rw [Kigali Institute of Education (KIE), Kigali (Rwanda)
2014-01-15
Noncommutative phase spaces are generated and classified in the framework of centrally extended anisotropic planar kinematical Lie groups as well as in the framework of noncentrally abelian extended planar absolute time Lie groups. Through these constructions the coordinates of the phase spaces do not commute due to the presence of naturally introduced fields giving rise to minimal couplings. By symplectic realizations methods, physical interpretations of generators coming from the obtained structures are given.
Generalized bracket formulation of constrained dynamics in phase space.
Sergi, Alessandro
2004-02-01
A generalized bracket formalism is used to define the phase space flow of constrained systems. The generalized bracket naturally subsumes the approach to constrained dynamics given by Dirac some time ago. The dynamical invariant measure and the linear response of systems subjected to holonomic constraints are explicitly derived. In light of previous results, it is shown that generalized brackets provide a simple and unified view of the statistical mechanics of non-Hamiltonian phase space flows with a conserved energy.
The Wigner distribution function in modal characterisation
CSIR Research Space (South Africa)
Mredlana, Prince
2016-07-01
Full Text Available function in modal characterisation P. MREDLANA1, D. NAIDOO1, C MAFUSIRE2, T. KRUGER2, A. DUDLEY1,3, A. FORBES1,3 1CSIR National Laser Centre, PO BOX 395, Pretoria 0001, South Africa. 2Department of Physics, Faculty of Natural and Agricultural..., the Wigner distribution of ð ð¥ is an integral of the correlation function ð ð¥ + 1 2 ð¥â² ð â ð¥ + 1 2 ð¥â² represented as: ðð ð¥, ð = ð ð¥ + 1 2 ð¥â² ð â ð¥ + 1 2 ð¥â² ðâððð¥â²ðð...
Wigner time delay and spin-orbit activated confinement resonances
Keating, D. A.; Deshmukh, P. C.; Manson, S. T.
2017-09-01
A study of the photoionization of spin-orbit split subshells of high-Z atoms confined in C60 has been performed using the relativistic-random-phase approximation. Specifically, Hg@C60 5p, Rn@C60 6p and Ra@C60 5d were investigated and the near-threshold confinement resonances in the j = l - 1/2 channels were found to engender structures in the j = l + 1/2 cross sections via correlation in the form of interchannel coupling. These structures are termed spin-orbit induced confinement resonances and they are found to profoundly influence the Wigner time delay spectrum resulting in time delays of tens or hundreds of attoseconds along with dramatic swings in time delay over small energy intervals. Pronounced relativistic effects in time delay are also found. These structures, including their manifestation in time delay spectra, are expected to be general phenomena in the photoionization of spin-orbit doublets in confined high-Z atoms.
Evolution of classical projected phase space density in billiards
Indian Academy of Sciences (India)
Abstract. The classical phase space density projected on to the configuration space offers a means of comparing classical and quantum evolution. In this alternate approach that we adopt here, we show that for billiards, the eigenfunctions of the coarse-grained projected classical evolution operator are identical to a first ...
Para-Galilean versus Galilean Noncommutative Phase spaces
Ngendakumana, Ancille; Nzotungicimpaye, Joachim; Todjihounde, Leonard
2012-01-01
The present paper deals with the construction of noncommutative phase spaces as coadjoint orbits of noncentral extensions of Galilei and Para-Galilei groups in two-dimensional space. The noncommutativity is due to the presence of a dual magnetic field B* in the Galilei case and of a magnetic field B in the Para-Galilei case.
Elementary particles and emergent phase space
Zenczykowski, Piotr
2014-01-01
The Standard Model of elementary particles, although very successful, contains various elements that are put in by hand. Understanding their origin requires going beyond the model and searching for ""new physics"". The present book elaborates on one particular proposal concerning such physics. While the original conception is 50 years old, it has not lost its appeal over time. Its basic idea is that space - an arena of events treated in the Standard Model as a classical background - is a concept which emerges from a strictly discrete quantum layer in the limit of large quantum numbers. This bo
The diffusion of stars through phase space
Binney, James; Lacey, Cedric
1988-01-01
An orbit-averaged Fokker-Planck equation has been derived to study the secular evolution of stellar systems with regular orbits and the heating of stellar disks. It is shown that a population of stars with an initially Maxwellian peculiar-velocity distribution will remain Maxwellian as it diffuses through orbit space only if: (1) a second-order diffusion tensor is proportional to epicycle energy; and (2) the population's velocity dispersion grows as the square root of time. Scattering by ephemeral spiral waves is able to account for the observed kinematics of the solar neighborhood only if the waves have wavelengths in excess of 9 kpc and constantly drifting pattern speeds.
Space Storm as a Dynamical Phase Transition
Wanliss, J. A.
2006-12-01
Fluctuations of the DST index were analyzed for several magnetic storms preceded by more than a week of extremely quiet conditions to establish that there is a rapid and unidirectional change in the Hurst scaling exponent at the time of storm onset. That is, the transition is accompanied by the specific signature of a rapid unidirectional change in the temporal fractal scaling of fluctuations in DST, signaling the formation of a new dynamical phase (or mode) which is considerably more organized than the background state. We compare these results to a model of multifractional Brownian motion and suggest that the relatively sudden change from a less correlated to a more correlated pattern of multiscale fluctuations at storm onset can be characterized in terms of nonequilibrium dynamical phase transitions. Initial results show that a dynamical transition in solar wind VBs is correlated with the storm onset for intense storms, suggesting that the transition observed in DST is of external solar wind origin, rather than internal magnetospheric origin. On the other hand, some results show a dynamical transition in solar wind scaling exponents not matched in DST. As well, we also present results for small storms where there is a strong dynamical transition in DST without a similar changes in the VBs scaling statistics. The results for small storms seem to reduce the importance of the solar wind fluctuations but the evidence for the intense storms seems to point to the solar wind as being responsible for providing the scale free properties in the DST fluctuations.
Controlling quantum interference in phase space with amplitude.
Xue, Yinghong; Li, Tingyu; Kasai, Katsuyuki; Okada-Shudo, Yoshiko; Watanabe, Masayoshi; Zhang, Yun
2017-05-23
We experimentally show a quantum interference in phase space by interrogating photon number probabilities (n = 2, 3, and 4) of a displaced squeezed state, which is generated by an optical parametric amplifier and whose displacement is controlled by amplitude of injected coherent light. It is found that the probabilities exhibit oscillations of interference effect depending upon the amplitude of the controlling light field. This phenomenon is attributed to quantum interference in phase space and indicates the capability of controlling quantum interference using amplitude. This remarkably contrasts with the oscillations of interference effects being usually controlled by relative phase in classical optics.
Kinematic variables in noncommutative phase space and parameters of noncommutativity
Gnatenko, Kh. P.
2017-10-01
We consider a space with noncommutativity of coordinates and noncommutativity of momenta. It is shown that coordinates in noncommutative phase space depend on mass therefore they cannot be considered as kinematic variables. Also, noncommutative momenta are not proportional to a mass as it has to be. We find conditions on the parameters of noncommutativity on which these problems are solved. It is important that on the same conditions the properties of kinetic energy are preserved, the motion of the center-of-mass of composite system and relative motion are independent, the trajectory of a particle (composite system) is independent of its mass and composition therefore the weak equivalence principle is recovered in four-dimensional (2D configurational space and 2D momentum space) noncommutative phase space.
Zeeman deceleration beyond periodic phase space stability
Toscano, Jutta; Tauschinsky, Atreju; Dulitz, Katrin; Rennick, Christopher J.; Heazlewood, Brianna R.; Softley, Timothy P.
2017-08-01
In Zeeman deceleration, time-varying spatially inhomogeneous magnetic fields are used to create packets of translationally cold, quantum-state-selected paramagnetic particles with a tuneable forward velocity, which are ideal for cold reaction dynamics studies. Here, the covariance matrix adaptation evolutionary strategy is adopted in order to optimise deceleration switching sequences for the operation of a Zeeman decelerator. Using the optimised sequences, a 40% increase in the number of decelerated particles is observed compared to standard sequences for the same final velocity, imposing the same experimental boundary conditions. Furthermore, we demonstrate that it is possible to remove up to 98% of the initial kinetic energy of particles in the incoming beam, compared to the removal of a maximum of 83% of kinetic energy with standard sequences. Three-dimensional particle trajectory simulations are employed to reproduce the experimental results and to investigate differences in the deceleration mechanism adopted by standard and optimised sequences. It is experimentally verified that the optimal solution uncovered by the evolutionary algorithm is not merely a local optimisation of the experimental parameters—it is a novel mode of operation that goes beyond the standard periodic phase stability approach typically adopted.
Wigner function and the probability representation of quantum states
Directory of Open Access Journals (Sweden)
Man’ko Margarita A.
2014-01-01
Full Text Available The relation of theWigner function with the fair probability distribution called tomographic distribution or quantum tomogram associated with the quantum state is reviewed. The connection of the tomographic picture of quantum mechanics with the integral Radon transform of the Wigner quasidistribution is discussed. The Wigner–Moyal equation for the Wigner function is presented in the form of kinetic equation for the tomographic probability distribution both in quantum mechanics and in the classical limit of the Liouville equation. The calculation of moments of physical observables in terms of integrals with the state tomographic probability distributions is constructed having a standard form of averaging in the probability theory. New uncertainty relations for the position and momentum are written in terms of optical tomograms suitable for directexperimental check. Some recent experiments on checking the uncertainty relations including the entropic uncertainty relations are discussed.
Accessing the gluon Wigner distribution in ultraperipheral p A collisions
Hagiwara, Yoshikazu; Hatta, Yoshitaka; Pasechnik, Roman; Tasevsky, Marek; Teryaev, Oleg
2017-08-01
We propose to constrain the gluon Wigner distribution in the nucleon by studying the exclusive diffractive dijet production process in ultraperipheral proton-nucleus collisions (UPCs) at the RHIC and the LHC. Compared to the previous proposal in Ref. [Y. Hatta, B. W. Xiao, and F. Yuan, Phys. Rev. Lett. 116, 202301 (2016)., 10.1103/PhysRevLett.116.202301] to study the same observable in lepton-nucleon scattering, the use of UPCs has a few advantages: not only is the cross section larger, but the extraction of the Wigner distribution from the data also becomes simpler, including its elliptic angular dependence. We compute the corresponding cross section and evaluate the coefficients using models which include the gluon saturation effects. A potential for the measurements of the Wigner distribution at current and future experimental facilities is also discussed.
Strong semiclassical approximation of Wigner functions for the Hartree dynamics
Athanassoulis, Agissilaos
2011-01-01
We consider the Wigner equation corresponding to a nonlinear Schrödinger evolution of the Hartree type in the semiclassical limit h → 0. Under appropriate assumptions on the initial data and the interaction potential, we show that the Wigner function is close in L 2 to its weak limit, the solution of the corresponding Vlasov equation. The strong approximation allows the construction of semiclassical operator-valued observables, approximating their quantum counterparts in Hilbert-Schmidt topology. The proof makes use of a pointwise-positivity manipulation, which seems necessary in working with the L 2 norm and the precise form of the nonlinearity. We employ the Husimi function as a pivot between the classical probability density and the Wigner function, which - as it is well known - is not pointwise positive in general.
The Collected Works of Eugene Paul Wigner the Scientific Papers
Wigner, Eugene Paul
1993-01-01
Eugene Wigner is one of the few giants of 20th-century physics His early work helped to shape quantum mechanics, he laid the foundations of nuclear physics and nuclear engineering, and he contributed significantly to solid-state physics His philosophical and political writings are widely known All his works will be reprinted in Eugene Paul Wigner's Collected Workstogether with descriptive annotations by outstanding scientists The present volume begins with a short biographical sketch followed by Wigner's papers on group theory, an extremely powerful tool he created for theoretical quantum physics They are presented in two parts The first, annotated by B Judd, covers applications to atomic and molecular spectra, term structure, time reversal and spin In the second, G Mackey introduces to the reader the mathematical papers, many of which are outstanding contributions to the theory of unitary representations of groups, including the famous paper on the Lorentz group
Wigner Ville Distribution in Signal Processing, using Scilab Environment
Directory of Open Access Journals (Sweden)
Petru Chioncel
2011-01-01
Full Text Available The Wigner Ville distribution offers a visual display of quantitative information about the way a signal’s energy is distributed in both, time and frequency. Through that, this distribution embodies the fundamentally concepts of the Fourier and time-domain analysis. The energy of the signal is distributed so that specific frequencies are localized in time by the group delay time and at specifics instants in time the frequency is given by the instantaneous frequency. The net positive volum of the Wigner distribution is numerically equal to the signal’s total energy. The paper shows the application of the Wigner Ville distribution, in the field of signal processing, using Scilab environment.
The Phase Space Elementary Cell in Classical and Generalized Statistics
Directory of Open Access Journals (Sweden)
Piero Quarati
2013-10-01
Full Text Available In the past, the phase-space elementary cell of a non-quantized system was set equal to the third power of the Planck constant; in fact, it is not a necessary assumption. We discuss how the phase space volume, the number of states and the elementary-cell volume of a system of non-interacting N particles, changes when an interaction is switched on and the system becomes or evolves to a system of correlated non-Boltzmann particles and derives the appropriate expressions. Even if we assume that nowadays the volume of the elementary cell is equal to the cube of the Planck constant, h3, at least for quantum systems, we show that there is a correspondence between different values of h in the past, with important and, in principle, measurable cosmological and astrophysical consequences, and systems with an effective smaller (or even larger phase-space volume described by non-extensive generalized statistics.
Grassmann phase space methods for fermions. II. Field theory
Energy Technology Data Exchange (ETDEWEB)
Dalton, B.J., E-mail: bdalton@swin.edu.au [Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne, Victoria 3122 (Australia); Jeffers, J. [Department of Physics, University of Strathclyde, Glasgow G4ONG (United Kingdom); Barnett, S.M. [School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)
2017-02-15
In both quantum optics and cold atom physics, the behaviour of bosonic photons and atoms is often treated using phase space methods, where mode annihilation and creation operators are represented by c-number phase space variables, with the density operator equivalent to a distribution function of these variables. The anti-commutation rules for fermion annihilation, creation operators suggests the possibility of using anti-commuting Grassmann variables to represent these operators. However, in spite of the seminal work by Cahill and Glauber and a few applications, the use of Grassmann phase space methods in quantum-atom optics to treat fermionic systems is rather rare, though fermion coherent states using Grassmann variables are widely used in particle physics. This paper presents a phase space theory for fermion systems based on distribution functionals, which replace the density operator and involve Grassmann fields representing anti-commuting fermion field annihilation, creation operators. It is an extension of a previous phase space theory paper for fermions (Paper I) based on separate modes, in which the density operator is replaced by a distribution function depending on Grassmann phase space variables which represent the mode annihilation and creation operators. This further development of the theory is important for the situation when large numbers of fermions are involved, resulting in too many modes to treat separately. Here Grassmann fields, distribution functionals, functional Fokker–Planck equations and Ito stochastic field equations are involved. Typical applications to a trapped Fermi gas of interacting spin 1/2 fermionic atoms and to multi-component Fermi gases with non-zero range interactions are presented, showing that the Ito stochastic field equations are local in these cases. For the spin 1/2 case we also show how simple solutions can be obtained both for the untrapped case and for an optical lattice trapping potential.
Relativistic Hydrogen-Like Atom on a Noncommutative Phase Space
Masum, Huseyin; Dulat, Sayipjamal; Tohti, Mutallip
2017-09-01
The energy levels of hydrogen-like atom on a noncommutative phase space were studied in the framework of relativistic quantum mechanics. The leading order corrections to energy levels 2 S 1/2, 2 P 1/2 and 2 P 3/2 were obtained by using the 𝜃 and the \\bar θ modified Dirac Hamiltonian of hydrogen-like atom on a noncommutative phase space. The degeneracy of the energy levels 2 P 1/2 and 2 P 3/2 were removed completely by 𝜃-correction. And the \\bar θ -correction shifts these energy levels.
Phase space flows for non-Hamiltonian systems with constraints.
Sergi, Alessandro
2005-09-01
In this paper, non-Hamiltonian systems with holonomic constraints are treated by a generalization of Dirac's formalism. Non-Hamiltonian phase space flows can be described by generalized antisymmetric brackets or by general Liouville operators which cannot be derived from brackets. Both situations are treated. In the first case, a Nosé-Dirac bracket is introduced as an example. In the second one, Dirac's recipe for projecting out constrained variables from time translation operators is generalized and then applied to non-Hamiltonian linear response. Dirac's formalism avoids spurious terms in the response function of constrained systems. However, corrections coming from phase space measure must be considered for general perturbations.
Naval Space Surveillance Center uses of time, frequency, and phase
Hayden, Carroll C.; Knowles, Stephen H.
1992-01-01
The Naval Space Surveillance Center (NAVSPASUR) is an operational naval command that has the mission of determining the location of all manmade objects in space and transmitting information on objects of interest to the fleet. NAVSPASUR operates a 217 MHz radar fence that has 9 transmitting and receiving stations deployed in a line across southern Continental United States (CONUS). This surveillance fence provides unalerted detection of satellites overflying CONUS. NAVSPASUR also maintains a space catalog of all orbiting space objects. NAVSPASUR plays an important role as operational alternate to the primary national Space Surveillance Center (SSC) and Space Defence Operations Center (SPADOC). In executing these responsibilities, NAVSPASUR needs precise and/or standardized time and frequency in a number of applications. These include maintenance of the radar fence references to specification, and coordination with other commands and agencies for data receipt and dissemination. Precise time and frequency must be maintained within each site to enable proper operation of the interferometry phasing technique used. Precise time-of-day clocking must exist between sites for proper intersite coordination. Phase may be considered a derivative of time and frequency. Its control within each transmitter or receiver site is of great importance to NAVSPASUR because of the operation of the sensor as an interferometer system, with source direction angles as the primary observable. Determination of the angular position of a satellite is directly dependent on the accuracy with which the differential phase between spaced subarrays can be measured at each receiver site. Various aspects of the NAVSPASUR are discussed with respect to time, frequency, and phase.
Energy Technology Data Exchange (ETDEWEB)
Shit, Anindita [Department of Chemistry, Bengal Engineering and Science University, Shibpur, Howrah 711103 (India); Chattopadhyay, Sudip, E-mail: sudip_chattopadhyay@rediffmail.com [Department of Chemistry, Bengal Engineering and Science University, Shibpur, Howrah 711103 (India); Ray Chaudhuri, Jyotipratim, E-mail: jprc_8@yahoo.com [Department of Physics, Katwa College, Katwa, Burdwan 713130 (India)
2014-03-18
Highlights: • Nonadiabatic dynamics of quantum particle under the impact of high-frequency force. • Formulation of time-independent dynamics via Floquet and Kapitza schemes. • Manipulation of external force parameters allows us to control the escape rate. • Increase of (amplitudes/frequency) causes the system to decay faster, in general. • Crossover temperature increases in the presence of the field. - Abstract: Escape under the action of the external modulation constitutes a nontrivial generalization of an conventional Kramers rate because the system is away from thermal equilibrium. A derivation of this result from the point of view of Langevin dynamics in the frame of Floquet theorem in conjunction with the Kapitza–Landau time window (that leads to an attractive description of the time-dependent quantum dynamics in terms of time-independent one) has been provided. The quantum escape rate in the intermediate-to-high and very-high damping regime so obtained analytically using the phase space formalism associated with the Wigner distribution and path-integral formalism bears a quantum correction that depends strongly on the barrier height. It is shown that an increase of (amplitude/frequency) ratio causes the system to decay faster, in general. The crossover temperature between tunneling and thermal activation increases in the presence of field so that quantum effects in the escape are relevant at higher temperatures.
An Asymmetrical Space Vector Method for Single Phase Induction Motor
DEFF Research Database (Denmark)
Cui, Yuanhai; Blaabjerg, Frede; Andersen, Gert Karmisholt
2002-01-01
the motor torque performance is not good enough. This paper addresses a new control method, an asymmetrical space vector method with PWM modulation, also a three-phase inverter is used for the main winding and the auxiliary winding. This method with PWM modulation is implemented to control the motor speed...
Quantum Theory of Reactive Scattering in Phase Space
Goussev, A.; Schubert, R.; Waalkens, H.; Wiggins, S.; Nicolaides, CA; Brandas, E
2010-01-01
We review recent results on quantum reactive scattering from a phase space perspective. The approach uses classical and quantum versions of Poincare-Birkhoff normal form theory and the perspective of dynamical systems theory. Over the past 10 years the classical normal form theory has provided a
Geometrical Series and Phase Space in a Finite Oscillatory Motion
Mareco, H. R. Olmedo
2006-01-01
This article discusses some interesting physical properties of oscillatory motion of a particle on two joined inclined planes. The geometrical series demonstrates that the particle will oscillate during a finite time. Another detail is the converging path to the origin of the phase space. Due to its simplicity, this motion may be used as a…
Phase-space treatment of the driven quantum harmonic oscillator
Indian Academy of Sciences (India)
A recent phase-space formulation of quantum mechanics in terms of the Glauber coherent states is applied to study the interaction of a one-dimensional harmonic oscillator with an arbitrary time-dependent force. Wave functions of the simultaneous values of position q and momentum p are deduced, which in turn give the ...
q-Path entropy phenomenology for phase-space curves
Zamora, D. J.; Rocca, M. C.; Plastino, A.; Ferri, G. L.
2018-01-01
We describe the phenomenology of the classical q-path entropy of a phase-space curve. This allows one to disclose an entropic force-like mechanism that is able to mimic some phenomenological aspects of the strong force, such as confinement, hard core, and asymptotic freedom.
Trigonometry of the quantum state space, geometric phases and relative phases
Ortega, R
2003-01-01
A complete set of invariants for three states in the quantum space of states P is obtained together with a complete set of relationships linking them. This is done in a way that preserves the self-duality of P and leads to a clear geometric description of invariants (distances, lateral phases; Hermitian angles, angular phases; and two purely triangular phases). Some of these invariants appear here for the first time. Symplectic area (and hence the triangle geometric phase) is proportional to a 'mixed phase excess', thus extending to P the relation 'area-angular excess' in the real sphere. The new triangle lateral phases provide a description, intrinsic to P, of relative phases in a superposition. This approach also provides closed expressions for the triangle holonomy associated with the usual Fubini-Study metric in P, as well as many other expressions for similar 'loop' operators along the triangle, including closed and exact expressions for the triangle Aharonov-Anandan geometric phase.
Driven phase space vortices in plasmas with nonextensive velocity distribution
Trivedi, Pallavi; Ganesh, Rajaraman
2017-03-01
The evolution of chirp-driven electrostatic waves in unmagnetized plasmas is numerically investigated by using a one-dimensional (1D) Vlasov-poisson solver with periodic boundary conditions. The initial velocity distribution of the 1D plasma is assumed to be governed by nonextensive q distribution [C. Tsallis, J. Stat. Phys. 52, 479 (1988)]. For an infinitesimal amplitude of an external drive, we investigate the effects of chirp driven dynamics that leads to the formation of giant phase space vortices (PSV) for both Maxwellian (q = 1) and non-Maxwellian ( q ≠ 1 ) plasmas. For non-Maxwellian plasmas, the formation of giant PSV with multiple extrema and phase velocities is shown to be dependent on the strength of "q". Novel features such as "shark"-like and transient "honeycomb"-like structures in phase space are discussed. Wherever relevant, we compare our results with previous work.
The projection-like techniques for Wigner's distribution function
Kajfosz, A.
1987-12-01
Starting from the quantum Liouville equation for many-particle distribution function an evolution equation for fully factorized and symmetrized Wigner's distribution function is derived. Our approach is formally similar to the projection operator method. Details of the used techniques are presented as an example of the two-particle system.
Variational Wigner-Kirkwood approach to relativistic mean field theory
Energy Technology Data Exchange (ETDEWEB)
Del Estal, M.; Centelles, M.; Vinas, X. [Departament d`Estructura i Constituents de la Materia, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona (Spain)
1997-10-01
The recently developed variational Wigner-Kirkwood approach is extended to the relativistic mean field theory for finite nuclei. A numerical application to the calculation of the surface energy coefficient in semi-infinite nuclear matter is presented. The new method is contrasted with the standard density functional theory and the fully quantal approach. {copyright} {ital 1997} {ital The American Physical Society}
The Wigner molecule in a 2D quantum dot
Akman, N.; Tomak, M.
1999-01-01
The charge density and pair correlation function of three interacting electrons confined within a two-dimensional disc-like hard wall quantum dot are calculated by full numerical diagonalization of the Hamiltonian. The formation of a Wigner-molecule in the form of equilateral triangular configuration for electrons is observed as the size of the dot is increased.
Eugene P. Wigner – in the light of unexpected events
Directory of Open Access Journals (Sweden)
Koblinger L.
2014-01-01
Full Text Available In the first part of the paper, Wigner’s humane attitude is overviewed based on the author’s personal impressions and on selected quotations from Wigner and his contemporaries. The second part briefly summarizes Wigner’s contribution to the development of nuclear science and technology.
Wigner function non-classicality as indicator of quantum chaos
Kowalewska-Kudłaszyk, A.; Kalaga, J. K.; Leoński, W.
2009-01-01
We propose a Wigner function based parameter that can be used as an indicator of quantum chaos. This parameter is defined as "entropy" from the time-dependence of "non-classicallity" proposed in \\cite{KZ04}. We perform our considerations for the system of damped nonlinear (Kerr-like) oscillator excited by a series of ultra-short external pulses.
Emittance and Phase Space Tomography for the Fermilab Linac
Energy Technology Data Exchange (ETDEWEB)
Garcia, F.G.G.; Johnstone, C.; Kobilarcik, T.; Koizumi, G.M.; Moore, C.D.; /Fermilab; Newhart, D.L.; /Fermilab
2012-05-01
The Fermilab Linac delivers a variable intensity, 400-MeV beam to the MuCool Test Area experimental hall via a beam line specifically designed to facilitate measurements of the Linac beam emittance and properties. A 10 m, dispersion-free and magnet-free straight utilizes an upstream quadrupole focusing triplet in combination with the necessary in-straight beam diagnostics to fully characterize the transverse beam properties. Since the Linac does not produce a strictly elliptical phase space, tomography must be performed on the profile data to retrieve the actual particle distribution in phase space. This is achieved by rotating the phase space distribution using different waist focusing conditions of the upstream triplet and performing a deconvolution of the profile data. Preliminary measurements using this diagnostic section are reported here. These data represent a first-pass measurement of the Linac emittance based on various techniques. It is clear that the most accurate representation of the emittance is given by the 3-profile approach. Future work will entail minimizing the beam spot size on MW5 to test and possibly improve the accuracy of the 2-profile approach. The 95% emittance is {approx} 18{pi} in the vertical and {approx} 13{pi} in the horizontal, which is especially larger than anticipated - 8-10{pi} was expected. One possible explanation is that the entire Linac pulse is extracted into the MTA beamline and during the first few microseconds, the feed forward and RF regulation are not stable. This may result in a larger net emittance observed versus beam injected into Booster, where the leading part of the Linac beam pulse is chopped. Future studies will clearly entail a measurement of the emittance vs. pulse length. One additional concern is that the Linac phase space is most likely aperture-defined and non-elliptical in nature. A non-elliptical phase-space determination would require a more elaborate analysis and provide another explanation of the
Phase-space Dynamics of Runaway Electrons In Tokamaks
Energy Technology Data Exchange (ETDEWEB)
Xiaoyin Guan, Hong Qin, and Nathaniel J. Fisch
2010-08-31
The phase-space dynamics of runaway electrons is studied, including the influence of loop voltage, radiation damping, and collisions. A theoretical model and a numerical algorithm for the runaway dynamics in phase space are developed. Instead of standard integrators, such as the Runge-Kutta method, a variational symplectic integrator is applied to simulate the long-term dynamics of a runaway electron. The variational symplectic integrator is able to globally bound the numerical error for arbitrary number of time-steps, and thus accurately track the runaway trajectory in phase space. Simulation results show that the circulating orbits of runaway electrons drift outward toward the wall, which is consistent with experimental observations. The physics of the outward drift is analyzed. It is found that the outward drift is caused by the imbalance between the increase of mechanical angular momentum and the input of toroidal angular momentum due to the parallel acceleration. An analytical expression of the outward drift velocity is derived. The knowledge of trajectory of runaway electrons in configuration space sheds light on how the electrons hit the first wall, and thus provides clues for possible remedies.
New science from the phase space of old stellar systems
Varri, Anna Lisa; Breen, Philip G.; Heggie, Douglas C.; Tiongco, Maria; Vesperini, Enrico
2017-06-01
Our traditional interpretative picture of the internal dynamics of globular clusters has been recently revolutionized by a series of discoveries about their chemical, structural, and kinematic properties. The empirical evidence that their velocity space is much more complex than usually expected encourages us to use them as refreshingly novel phase space laboratories for some long-forgotten aspects of collisional gravitational dynamics. Such a realization, coupled with the discovery that the stars in clusters were not all born at once in a single population, makes them new, challenging chemodynamical puzzles.Thanks to the proper motions of thousands of stars that will be available from the Gaia mission, we are about to enter a new ''golden age'' for the study of the dynamics of this class of stellar systems, as the full phase space of several Galactic globular clusters will be soon unlocked for the first time. In this context, I will present the highlights of a more realistic dynamical paradigm for these intriguing stellar systems, with emphasis on the role of angular momentum, velocity anisotropy and external tidal field. Such a fundamental understanding of the emerging phase space complexity of globulars will allow us to address many open questions about their rich dynamical evolution, their elusive stellar populations and putative black holes, and their role within the history of our Galaxy.
Generalized Uncertainty Principle Corrections to the Simple Harmonic Oscillator in Phase Space
Das, Saurya; Walton, Mark A
2016-01-01
We compute Wigner functions for the harmonic oscillator including corrections from generalized uncertainty principles (GUPs), and study the corresponding marginal probability densities and other properties. We show that the GUP corrections to the Wigner functions can be significant, and comment on their potential measurability in the laboratory.
Laser Interferometer Space Antenna (LISA) Far Field Phase Pattern
Waluschka, Eugene
1999-01-01
The Laser Interferometry Space Antenna (LISA) for the detection of Gravitational Waves is a very long baseline interferometer that will measure the changes in the distance of a five million kilometer arm to pico meter accuracies. Knowledge of the phase deviations from a spherical wave and what causes these deviations are needed considerations in (as a minimum) the design of the telescope and in determining pointing requirements. Here we present the far field phase deviations from a spherical wave for given Zernike aberrations and obscurations of the exit pupil.
Probabilistic phase space trajectory description for anomalous polymer dynamics
Energy Technology Data Exchange (ETDEWEB)
Panja, Debabrata [Institute for Theoretical Physics, Universiteit van Amsterdam, Science Park 904, Postbus 94485, 1090 GL Amsterdam (Netherlands)
2011-03-16
It has been recently shown that the phase space trajectories for the anomalous dynamics of a tagged monomer of a polymer-for single polymeric systems and phenomena such as phantom Rouse, self-avoiding Rouse, and Zimm ones, reptation, and translocation through a narrow pore in a membrane, as well as for many polymeric systems such as polymer melts in the entangled regime-are robustly described by the generalized Langevin equation. Here I show that the probability distribution of phase space trajectories for all of these classical anomalous dynamics for single polymers is that of a fractional Brownian motion (fBm), while the dynamics for polymer melts between the entangled regime and the eventual diffusive regime exhibits small but systematic deviations from that of a fBm.
Identifying phase-space boundaries with Voronoi tessellations
Energy Technology Data Exchange (ETDEWEB)
Debnath, Dipsikha; Matchev, Konstantin T. [University of Florida, Physics Department, Gainesville, FL (United States); Gainer, James S. [University of Hawaii, Department of Physics and Astronomy, Honolulu, HI (United States); Kilic, Can; Yang, Yuan-Pao [The University of Texas at Austin, Theory Group, Department of Physics and Texas Cosmology Center, Austin, TX (United States); Kim, Doojin [University of Florida, Physics Department, Gainesville, FL (United States); CERN, Theory Division, Geneva 23 (Switzerland)
2016-11-15
Determining the masses of new physics particles appearing in decay chains is an important and longstanding problem in high energy phenomenology. Recently it has been shown that these mass measurements can be improved by utilizing the boundary of the allowed region in the fully differentiable phase space in its full dimensionality. Here we show that the practical challenge of identifying this boundary can be solved using techniques based on the geometric properties of the cells resulting from Voronoi tessellations of the relevant data. The robust detection of such phase-space boundaries in the data could also be used to corroborate a new physics discovery based on a cut-and-count analysis. (orig.)
On the calculation of soft phase space integral
Zhu, Hua
2014-01-01
The recent discovery of the Higgs boson at the LHC attracts much attention to the precise calculation of its production cross section in quantum chromodynamics. In this work, we discuss the calculation of soft triple-emission phase space integral, which is an essential ingredient in the recently calculated soft-virtual corrections to Higgs boson production at next-to-next-to-next-to-leading order. The main techniques used this calculation are method of differential equation for Feynman integr...
A simple algorithm for longitudinal phase space tomography
Hancock, S
1997-01-01
Tomography is now a very broad topic with a wealth of different algorithms for the reconstruction of both qualitative and quantitative images. One of the simplest algorithms has been modified to take into account the non-linearity of large-amplitude synchrotron motion. This permits the accurate reconstruction of longitudinal phase space density from one-dimensional bunch profile data. The method may be further extended to treat, for example, multi-harmonic systems and self-fields.
Prediction of Tropical Rainfall by Local Phase Space Reconstruction.
Waelbroeck, H.; López-Pea, R.; Morales, T.; Zertuche, F.
1994-11-01
The authors propose a weather prediction model based on a local reconstruction of the dynamics in phase space, using an 11-year dataset from Tlaxcala, Mexico. A vector in phase space corresponds to T consecutive days of data; the best predictions are found for T = 14. The prediction for the next day, x0 fL(x0), is based on a local reconstruction of the dynamical map f in an ball centered at x0. The high dimensionality of the phase space implies a large optimal value of , so that the number of points in an ball is sufficient to reconstruct the local map. The local approximation fL f is therefore not very good and the prediction skill drops off quickly at first, with a timescale of 2 days. On the other hand, the authors find useful skill in the prediction of 10-day rainfall accumulations, which reflects the persistence of weather patterns. The mean-squared error in the prediction of the rainfall anomaly for the year 1992 was 64% of the variance, and the early beginning of the rain season was correctly predicted.
Multifractal spectrum of phase space related to generalized thermostatistics
Olemskoi, A. I.; Kharchenko, V. O.; Borisyuk, V. N.
2008-03-01
We consider a self-similar phase space with specific fractal dimension d being distributed with spectrum function f(d) . Related thermostatistics is shown to be governed by the Tsallis formalism of the non-extensive statistics, where the non-additivity parameter equals to τ ¯ (q) ≡ 1 / τ(q) > 1, and the multifractal function τ(q) = qdq - f(dq) is the specific heat determined with multifractal parameter q ∈ [ 1 , ∞ ] . At that, the equipartition law is shown to take place. Optimization of the multifractal spectrum function f(d) arrives at the relation between the statistical weight and the system complexity. It is shown that the statistical weight exponent τ(q) can be modeled by hyperbolic tangent deformed in accordance with both Tsallis and Kaniadakis exponential functions to describe arbitrary multifractal phase space explicitly. The spectrum function f(d) is proved to increase monotonically from minimum value f = - 1 at d = 0 to maximum one f = 1 at d = 1. At the same time, the number of monofractals increases with the growth of the phase-space volume at small dimensions d and falls down in the limit d → 1.
Pseudosymmetric random matrices: Semi-Poisson and sub-Wigner statistics.
Kumar, Sachin; Ahmed, Zafar
2017-08-01
Real nonsymmetric matrices may have either real or complex conjugate eigenvalues. These matrices can be seen to be pseudosymmetric as ηMη^{-1}=M^{t}, where the metric η could be secular (a constant matrix) or depending upon the matrix elements of M. Here we construct ensembles of a large number N of pseudosymmetric n×n (n large) matrices using N[n(n+1)/2≤N≤n^{2}] independent and identically distributed random numbers as their elements. Based on our numerical calculations, we conjecture that for these ensembles the nearest level spacing distributions [NLSDs, p(s)] are sub-Wigner as p_{abc}(s)=ase^{-bs^{c}}(0distributions of their eigenvalues fit well to D(ε)=A[tanh{(ε+B)/C}-tanh{(ε-B)/C}] (exceptions also discussed). These sub-Wigner NLSDs are encountered in Anderson metal-insulator transition and topological transitions in a Josephson junction. Interestingly, p(s) for c=1 is called semi-Poisson, and we show that it lies close to the form p(s)=0.59sK_{0}(0.45s^{2}) derived for the case of 2×2 pseudosymmetric matrix where the eigenvalues are most aptly conditionally real, E_{1,2}=a±sqrt[b^{2}-c^{2}], which represent characteristic coalescing of eigenvalues in parity-time (PT) -symmetric systems.
Grassmann phase space methods for fermions. I. Mode theory
Dalton, B. J.; Jeffers, J.; Barnett, S. M.
2016-07-01
In both quantum optics and cold atom physics, the behaviour of bosonic photons and atoms is often treated using phase space methods, where mode annihilation and creation operators are represented by c-number phase space variables, with the density operator equivalent to a distribution function of these variables. The anti-commutation rules for fermion annihilation, creation operators suggest the possibility of using anti-commuting Grassmann variables to represent these operators. However, in spite of the seminal work by Cahill and Glauber and a few applications, the use of Grassmann phase space methods in quantum-atom optics to treat fermionic systems is rather rare, though fermion coherent states using Grassmann variables are widely used in particle physics. The theory of Grassmann phase space methods for fermions based on separate modes is developed, showing how the distribution function is defined and used to determine quantum correlation functions, Fock state populations and coherences via Grassmann phase space integrals, how the Fokker-Planck equations are obtained and then converted into equivalent Ito equations for stochastic Grassmann variables. The fermion distribution function is an even Grassmann function, and is unique. The number of c-number Wiener increments involved is 2n2, if there are n modes. The situation is somewhat different to the bosonic c-number case where only 2 n Wiener increments are involved, the sign of the drift term in the Ito equation is reversed and the diffusion matrix in the Fokker-Planck equation is anti-symmetric rather than symmetric. The un-normalised B distribution is of particular importance for determining Fock state populations and coherences, and as pointed out by Plimak, Collett and Olsen, the drift vector in its Fokker-Planck equation only depends linearly on the Grassmann variables. Using this key feature we show how the Ito stochastic equations can be solved numerically for finite times in terms of c-number stochastic
Basire, Marie; Borgis, Daniel; Vuilleumier, Rodolphe
2013-08-14
Langevin dynamics coupled to a quantum thermal bath (QTB) allows for the inclusion of vibrational quantum effects in molecular dynamics simulations at virtually no additional computer cost. We investigate here the ability of the QTB method to reproduce the quantum Wigner distribution of a variety of model potentials, designed to assess the performances and limits of the method. We further compute the infrared spectrum of a multidimensional model of proton transfer in the gas phase and in solution, using classical trajectories sampled initially from the Wigner distribution. It is shown that for this type of system involving large anharmonicities and strong nonlinear coupling to the environment, the quantum thermal bath is able to sample the Wigner distribution satisfactorily and to account for both zero point energy and tunneling effects. It leads to quantum time correlation functions having the correct short-time behavior, and the correct associated spectral frequencies, but that are slightly too overdamped. This is attributed to the classical propagation approximation rather than the generation of the quantized initial conditions themselves.
Stochastic Nuclear Reaction Theory: Breit-Wigner nuclear noise
Energy Technology Data Exchange (ETDEWEB)
de Saussure, G.; Perez, R.B.
1988-01-01
The purpose of this paper is the application of various statistical tests for the detection of the intermediate structure, which lies immersed in the Breit-Wigner ''noise'' arising from the superposition of many compound nucleus resonances. To this end, neutron capture cross sections are constructed by Monte-Carlo simulations of the compound nucleus, hence providing the ''noise'' component. In a second step intermediate structure is added to the Breit-Wigner noise. The performance of the statistical tests in detecting the intermediate structure is evaluated using mocked-up neutron cross sections as the statistical samples. Afterwards, the statistical tests are applied to actual nuclear cross section data. 10 refs., 1 fig., 2 tabs.
Momentum-space cigar geometry in topological phases
Palumbo, Giandomenico
2018-01-01
In this paper, we stress the importance of momentum-space geometry in the understanding of two-dimensional topological phases of matter. We focus, for simplicity, on the gapped boundary of three-dimensional topological insulators in class AII, which are described by a massive Dirac Hamiltonian and characterized by an half-integer Chern number. The gap is induced by introducing a magnetic perturbation, such as an external Zeeman field or a ferromagnet on the surface. The quantum Bures metric acquires a central role in our discussion and identifies a cigar geometry. We first derive the Chern number from the cigar geometry and we then show that the quantum metric can be seen as a solution of two-dimensional non-Abelian BF theory in momentum space. The gauge connection for this model is associated to the Maxwell algebra, which takes into account the Lorentz symmetries related to the Dirac theory and the momentum-space magnetic translations connected to the magnetic perturbation. The Witten black-hole metric is a solution of this gauge theory and coincides with the Bures metric. This allows us to calculate the corresponding momentum-space entanglement entropy that surprisingly carries information about the real-space conformal field theory describing the defect lines that can be created on the gapped boundary.
Breit-Wigner Enhancement of Dark Matter Annihilation
Energy Technology Data Exchange (ETDEWEB)
Ibe, Masahiro; /SLAC; Murayama, Hitoshi; /Tokyo U., IPMU /UC, Berkeley /LBL, Berkeley; Yanagida, T.T.; /Tokyo U. /Tokyo U., IPMU
2009-06-19
We point out that annihilation of dark matter in the galactic halo can be enhanced relative to that in the early universe due to a Breit-Wigner tail, if the dark matter annihilates through a pole just below the threshold. This provides a new explanation to the 'boost factor' which is suggested by the recent data of the PAMELA, ATIC and PPB-BETS cosmic-ray experiments.
Spin-orbit-enhanced Wigner localization in quantum dots
DEFF Research Database (Denmark)
Cavalli, Andrea; Malet, F.; Cremon, J. C.
2011-01-01
We investigate quantum dots with Rashba spin-orbit coupling in the strongly-correlated regime. We show that the presence of the Rashba interaction enhances the Wigner localization in these systems, making it achievable for higher densities than those at which it is observed in Rashba-free quantum...... dots. Recurring shapes in the pair distribution functions of the yrast spectrum, which might be associated with rotational and vibrational modes, are also reported....
Wigner crystals: New realizations of an old idea
Directory of Open Access Journals (Sweden)
Sólyom J.
2014-01-01
Full Text Available In this review, after a brief discussion of Wigner’s ideas about the localization of electrons due to Coulomb interaction in a low-density electron system with neutralizing background and the formation of a periodic array, we present the various possibilities to realize Wigner crystals: on the surface of liquid helium, in semiconductor heterostructures, in graphene, in 1D systems and the analogous crystalline states in dusty plasma or in the assembly of trapped ions.
Wigner-function nonclassicality as indicator of quantum chaos.
Kowalewska-Kudłaszyk, A; Kalaga, J K; Leoński, W
2008-12-01
We propose a Wigner-function-based parameter that can be used as an indicator of quantum chaos. This parameter is defined as "entropy" from the time dependence of "nonclassicality" proposed by A. Kenfack and K. Zyczkowski [J. Opt. B 6, 394 (2004)]. We perform our considerations for the system of damped nonlinear (Kerr-like) oscillator excited by a series of ultrashort external pulses.
Universality of Wigner random matrices: a survey of recent results
Energy Technology Data Exchange (ETDEWEB)
Erdos, Laszlo [Ludwig-Maximilians-University of Munich (Germany)
2011-06-30
This is a study of the universality of spectral statistics for large random matrices. Considered are NxN symmetric, Hermitian, or quaternion self-dual random matrices with independent identically distributed entries (Wigner matrices), where the probability distribution of each matrix element is given by a measure {nu} with zero expectation and with subexponential decay. The main result is that the correlation functions of the local eigenvalue statistics in the bulk of the spectrum coincide with those of the Gaussian Orthogonal Ensemble (GOE), the Gaussian Unitary Ensemble (GUE), and the Gaussian Symplectic Ensemble (GSE), respectively, in the limit as N {yields} {infinity}. This approach is based on a study of the Dyson Brownian motion via a related new dynamics, the local relaxation flow. As a main input, it is established that the density of the eigenvalues converges to the Wigner semicircle law, and this holds even down to the smallest possible scale. Moreover, it is shown that the eigenvectors are completely delocalized. These results hold even without the condition that the matrix elements are identically distributed: only independence is used. In fact, for the matrix elements of the Green function strong estimates are given that imply that the local statistics of any two ensembles in the bulk are identical if the first four moments of the matrix elements match. Universality at the spectral edges requires matching only two moments. A Wigner-type estimate is also proved, and it is shown that the eigenvalues repel each other on arbitrarily small scales. Bibliography: 108 titles.
Wigner distribution moments in fractional Fourier transform systems.
Bastiaans, Martin J; Alieva, Tatiana
2002-09-01
It is shown how all global Wigner distribution moments of arbitrary order in the output plane of a (generally anamorphic) two-dimensional fractional Fourier transform system can be expressed in terms of the moments in the input plane. Since Wigner distribution moments are identical to derivatives of the ambiguity function at the origin, a similar relation holds for these derivatives. The general input-output relationship is then broken down into a number of rotation-type input-output relationships between certain combinations of moments. It is shown how the Wigner distribution moments (or ambiguity function derivatives) can be measured as intensity moments in the output planes of a set of appropriate fractional Fourier transform systems and thus be derived from the corresponding fractional power spectra. The minimum number of (anamorphic) fractional power spectra that are needed for the determination of these moments is derived. As an important by-product we get a number of moment combinations that are invariant under (anamorphic) fractional Fourier transformation.
Method of phase space beam dilution utilizing bounded chaos generated by rf phase modulation
Directory of Open Access Journals (Sweden)
Alfonse N. Pham
2015-12-01
Full Text Available This paper explores the physics of chaos in a localized phase-space region produced by rf phase modulation applied to a double rf system. The study can be exploited to produce rapid particle bunch broadening exhibiting longitudinal particle distribution uniformity. Hamiltonian models and particle-tracking simulations are introduced to understand the mechanism and applicability of controlled particle diffusion. When phase modulation is applied to the double rf system, regions of localized chaos are produced through the disruption and overlapping of parametric resonant islands and configured to be bounded by well-behaved invariant tori to prevent particle loss. The condition of chaoticity and the degree of particle dilution can be controlled by the rf parameters. The method has applications in alleviating adverse space-charge effects in high-intensity beams, particle bunch distribution uniformization, and industrial radiation-effects experiments.
Linearization of the longitudinal phase space without higher harmonic field
Directory of Open Access Journals (Sweden)
Benno Zeitler
2015-12-01
Full Text Available Accelerator applications like free-electron lasers, time-resolved electron diffraction, and advanced accelerator concepts like plasma acceleration desire bunches of ever shorter longitudinal extent. However, apart from space charge repulsion, the internal bunch structure and its development along the beam line can limit the achievable compression due to nonlinear phase space correlations. In order to improve such a limited longitudinal focus, a correction by properly linearizing the phase space is required. At large scale facilities like Flash at Desy or the European Xfel, a higher harmonic cavity is installed for this purpose. In this paper, another method is described and evaluated: Expanding the beam after the electron source enables a higher order correction of the longitudinal focus by a subsequent accelerating cavity which is operated at the same frequency as the electron gun. The elaboration of this idea presented here is based on a ballistic bunching scheme, but can be extended to bunch compression based on magnetic chicanes. The core of this article is an analytic model describing this approach, which is verified by simulations, predicting possible bunch length below 1 fs at low bunch charge. Minimizing the energy spread down to σ_{E}/E<10^{-5} while keeping the bunch long is another interesting possibility, which finds applications, e.g., in time resolved transmission electron microscopy concepts.
Balamurugan, M.; Chakrabarti, R.; Jenisha, B. Virgin
2017-05-01
We study the evolution of the hybrid entangled squeezed states of the qubit-oscillator system in the strong coupling domain. Following the adiabatic approximation we obtain the reduced density matrices of the qubit and the oscillator degrees of freedom. The oscillator reduced density matrix is utilized to calculate the quasiprobability distributions such as the Sudarshan-Glauber diagonal P-representation, the Wigner W-distribution, and the nonnegative Husimi Q-function. The negativity associated with the W-distribution indicates the nonclassicality of the developing state. The existence of the multiple time scales induced by the interaction introduces certain features in the bipartite system. In the strong coupling regime the transient evolution to low entropy configurations reveals brief emergence of nearly pure squeezed Schrödinger kitten states that may be regarded as superposition of uniformly separated distinguishable squeezed coherent states. However, the quantum fluctuations with a short time period engender bifurcation and subsequent rejoining of these peaks in the phase space. The abovementioned doubling of the number of peaks increases the entropy to its near maximal value. Nonetheless, these states characterized by high entropy values, are endowed with a large negativity of the W-distribution that points towards their non-Gaussian behavior. This may be ascertained by the significantly large Hilbert-Schmidt distance between the oscillator state and an ensemble of most general statistical mixture of squeezed Gaussian states possessing nearly identical second order quadrature moments as that of the oscillator.
Tomographic measurement of the phase space distribution of a space-charge-dominated beam
Stratakis, Diktys
Many applications of accelerators, such as free electron lasers, pulsed neutron sources, and heavy ion fusion, require a good quality beam with high intensity. In practice, the achievable intensity is often limited by the dynamics at the low-energy, space-charge dominated end of the machine. Because low-energy beams can have complex distribution functions, a good understanding of their detailed evolution is needed. To address this issue, we have developed a simple and accurate tomographic method to map the beam phase using quadrupole magnets, which includes the effects from space charge. We extend this technique to use also solenoidal magnets which are commonly used at low energies, especially in photoinjectors, thus making the diagnostic applicable to most machines. We simulate our technique using a particle in cell code (PIC), to ascertain accuracy of the reconstruction. Using this diagnostic we report a number of experiments to study and optimize injection, transport and acceleration of intense space charge dominated beams. We examine phase mixing, by studying the phase-space evolution of an intense beam with a transversely nonuniform initial density distribution. Experimental measurements, theoretical predictions and PIC simulations are in good agreement each other. Finally, we generate a parabolic beam pulse to model those beams from photoinjectors, and combine tomography with fast imaging techniques to investigate the time-sliced parameters of beam current, size, energy spread and transverse emittance. We found significant differences between the slice emittance profiles and slice orientation as the beam propagates downstream. The combined effect of longitudinal nonuniform profiles and fast imaging of the transverse phase space provided us with information about correlations between longitudinal and transverse dynamics that we report within this dissertation.
Invulnerability, coping, salutogenesis, integration: four phases of space psychology.
Suedfeld, Peter
2005-06-01
The relationship between NASA and the psychological research community has progressed through a number of phases during the past four decades. This paper summarizes how the relationship has developed as data have accumulated and space missions and crews have changed. In the beginning, most NASA astronauts and staff considered possible psychological problems during space missions to be a non-issue. It was assumed that people with "the right stuff" would not experience any such problems. A more realistic recognition of stress and its consequences has led to a concern with prevention and countermeasures, a concern that has come to dominate NASA's involvement with psychology. Very recently, space psychologists have started to import the concepts of positive psychology, and consider the benefits of participation in the space program, including the self-enhancing aspects of stressful experiences (salutogenesis). Both the agency and psychologists now need to broaden their thinking and their research to cover the gamut of empirical data and theoretical concepts. These include human strengths as well as vulnerabilities, both negative and positive impacts of spaceflight, long- as well as short-term effects, and the reactions not only of the astronauts themselves but also of ground personnel and the families of both groups.
Geometrical approach to the discrete Wigner function in prime power dimensions
Energy Technology Data Exchange (ETDEWEB)
Klimov, A B; Munoz, C; Romero, J L [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44410, Guadalajara, Jal. (Mexico)
2006-11-17
We analyse the Wigner function in prime power dimensions constructed on the basis of the discrete rotation and displacement operators labelled with elements of the underlying finite field. We separately discuss the case of odd and even characteristics and analyse the algebraic origin of the non-uniqueness of the representation of the Wigner function. Explicit expressions for the Wigner kernel are given in both cases.
Discrete phase-space approach to mutually orthogonal Latin squares
Gaeta, Mario; Di Matteo, Olivia; Klimov, Andrei B.; de Guise, Hubert
2014-10-01
We show there is a natural connection between Latin squares and commutative sets of monomials defining geometric structures in finite phase-space of prime power dimensions. A complete set of such monomials defines a mutually unbiased basis (MUB) and may be associated with a complete set of mutually orthogonal Latin squares (MOLS). We translate some possible operations on the monomial sets into isomorphisms of Latin squares, and find a general form of permutations that map between Latin squares corresponding to unitarily equivalent mutually unbiased sets.
Dynamical tunneling in systems with a mixed phase space
Energy Technology Data Exchange (ETDEWEB)
Loeck, Steffen
2010-04-22
Tunneling is one of the most prominent features of quantum mechanics. While the tunneling process in one-dimensional integrable systems is well understood, its quantitative prediction for systems with a mixed phase space is a long-standing open challenge. In such systems regions of regular and chaotic dynamics coexist in phase space, which are classically separated but quantum mechanically coupled by the process of dynamical tunneling. We derive a prediction of dynamical tunneling rates which describe the decay of states localized inside the regular region towards the so-called chaotic sea. This approach uses a fictitious integrable system which mimics the dynamics inside the regular domain and extends it into the chaotic region. Excellent agreement with numerical data is found for kicked systems, billiards, and optical microcavities, if nonlinear resonances are negligible. Semiclassically, however, such nonlinear resonance chains dominate the tunneling process. Hence, we combine our approach with an improved resonance-assisted tunneling theory and derive a unified prediction which is valid from the quantum to the semiclassical regime. We obtain results which show a drastically improved accuracy of several orders of magnitude compared to previous studies. (orig.)
What is the phase space of the last glacial inception?
Bahadory, Taimaz; Tarasov, Lev
2017-04-01
Would the ice and climate pattern of glacial inception changed much with small tweaks to the initial Eemian climate state? Given the very limited available geological constraints, what is the range of potential spatio-temporal patterns of ice sheet inception and associated climate? What positive and negative feedbacks between ice, atmospheric and ocean circulation, and vegetation dominate glacial inception? As a step towards answering these questions, we examine the phase space of glacial inception in response to a subset of uncertainties in a coupled 3D model through an ensemble of simulations. The coupled model consists of the GSM (Glacial Systems Model) and LOVECLIM earth systems model of intermediate complexity. The former includes a 3D ice sheet model, asynchronously coupled glacio isostatic adjustment, surface drainage solver, and permafrost resolving bed thermal model. The latter includes an ocean GCM, atmospheric component, dynamic/thermodynamic seaice, and simplified dynamical vegetation. Our phase space exploration probes uncertainties in: initial conditions, downscaling and upscaling, the radiative effect of clouds, snow and ice albedo, precipitation parameterization, and freshwater discharge. The probe is constrained by model fit to present day climate and LGM climate.
Laser Interferometer Space Antenna (LISA) Far Field Phase Patterns
Waluschka, Eugene; Obenschain, Arthur F. (Technical Monitor)
2000-01-01
The Laser Interferometer Space Antenna (LISA) consists of three spacecraft in orbit about the sun. The orbits are chosen such that the three spacecraft are always at (roughly) the vertices of a equilateral triangle with 5 million kilometer leg lengths. Even though the distances between the three spacecraft are 5 million kilometers, the expected phase shifts between any two beams, due to a gravitational wave, only correspond to a distance change of about 10 pico meters, which is about 10(exp -5) waves for a laser wavelength of 1064 nm. To obtain the best signal-to-noise ratio, noise sources such as changes in the apparent distances due to pointing jitter must be controlled carefully. This is the main reason for determining the far-field phase patterns of a LISA type telescope. Because of torque on the LISA spacecraft and other disturbances, continuous adjustments to the pointing of the telescopes are required. These pointing adjustments will be a "jitter" source. If the transmitted wave is perfectly spherical then rotations (Jitter) about its geometric center will not produce any effect at the receiving spacecraft. However, if the outgoing wave is not perfectly spherical, then pointing jitter will produce a phase variation at the receiving spacecraft. The following sections describe the "brute force" computational approach used to determine the scalar wave front as a function of exit pupil (Zernike) aberrations and to show the results (mostly graphically) of the computations. This approach is straightforward and produces believable phase variations to sub-pico meter accuracy over distances on the order of 5 million kilometers. As such this analyzes the far field phase sensitivity to exit pupil aberrations.
Tomography of the electron beam transverse phase space at PITZ
Energy Technology Data Exchange (ETDEWEB)
Asova, Galina
2013-09-15
The operation of a Free Elector Laser, FEL, requires high energy, high peak current electron beams with small transverse emittance. In the contemporary FELs, the electron beam is passed through a periodic magnetic structure - an undulator - which modifies the straight beam trajectory into a sinusoidal one, where FEL light is generated at each bend. According to the energy, the transverse emittance and the peak current of the beam and the parameters of the undulator, FEL radiation with wavelength in the range of nano- to micrometers can be generated. Studies and development of FELs are done all over the world. The Free electron LASer in Hamburg, FLASH, and the international European X-ray FEL, XFEL, in Hamburg, Germany, are two leading projects of the Deutsches Elektronen SYnchrotron, DESY. Part of the research program on FELs in DESY is realized in Zeuthen within the project Photo-Injector Test Facility at DESY in Zeuthen, PITZ. PITZ is an international collaboration including Germany, Russia, Italy, France, Bulgaria, Thailand, United Kingdom. The Institute of Nuclear Research and Nuclear Energy, INRNE, at the Bulgarian Academy of Sciences participates from bulgarian side. PITZ studies and optimizes the photo-injectors for FLASH and the XFEL. The research program emphasizes on detailed measurements of the transverse phase-space density distribution. Until 2010 the single slit scan technique has been used to measure the beam transverse distributions. At the end of 2010 a module for tomographic diagnostics has been installed which extends the possibilities of PITZ to measure simultaneously the two transverse planes of a single micropulse with improved signal-to-noise ratio. The difficult conditions of low emittance for high bunch charge and low energy make the operation of the module challenging. This thesis presents the design considerations for the tomography module, a number of reconstruction algorithms and their applicability to limited data sets, the influence
A Wigner Function Approach to Coherence in a Talbot-Lau Interferometer
Directory of Open Access Journals (Sweden)
Eric Imhof
2016-06-01
Full Text Available Using a thermal gas, we model the signal of a trapped interferometer. This interferometer uses two short laser pulses, separated by time T, which act as a phase grating for the matter waves. Near time 2 T , there is an echo in the cloud’s density due to the Talbot-Lau effect. Our model uses the Wigner function approach and includes a weak residual harmonic trap. The analysis shows that the residual potential limits the interferometer’s visibility, shifts the echo time of the interferometer, and alters its time dependence. Loss of visibility can be mitigated by optimizing the initial trap frequency just before the interferometer cycle begins.
Zarenia, Mohammad; Peeters, Francois; Neilson, David
The juxtaposition of superconducting and charge density wave (CDW) phases that is often observed in connection with High-Temperature Superconductors, is attracting considerable attention. In these systems, the crystal lattice provides a polarizable background, needed to drive the CDW phase. We report on a different system that exhibits the association of superfluid and CDW phases, but in which the polarizable background is uniform. Our system consists of two coupled two-dimensional bilayers of graphene, one bilayer containing electrons and the other holes interacting through the long range Coulomb interaction. To account for the inter-layer correlation energy accurately, we introduce a new approach which is based on the random phase approximation at high densities and interpolation between the weakly- and strongly-interacting regimes. We determine the zero temperature phase diagram in which the two control parameters are the equal electron and hole densities and the thickness of the insulating barrier separating the two bilayers. We find in addition to an electron-hole superfluid and a one-dimensional CDW phases that there exist also a coupled electron-hole Wigner crystal. The structure of the crystal background plays no role in determining the phase diagram. This work was supported by the Flemish Science Foundation (FWO).
Volumic omit maps in ab initio dual-space phasing.
Oszlányi, Gábor; Sütő, András
2016-07-01
Alternating-projection-type dual-space algorithms have a clear construction, but are susceptible to stagnation and, thus, inefficient for solving the phase problem ab initio. To improve this behaviour new omit maps are introduced, which are real-space perturbations applied periodically during the iteration process. The omit maps are called volumic, because they delete some predetermined subvolume of the unit cell without searching for atomic regions or analysing the electron density in any other way. The basic algorithms of positivity, histogram matching and low-density elimination are tested by their solution statistics. It is concluded that, while all these algorithms based on weak constraints are practically useless in their pure forms, appropriate volumic omit maps can transform them to practically useful methods. In addition, the efficiency of the already useful reflector-type charge-flipping algorithm can be further improved. It is important that these results are obtained by using non-sharpened structure factors and without any weighting scheme or reciprocal-space perturbation. The mathematical background of volumic omit maps and their expected applications are also discussed.
The Racah-Wigner algebra and coherent tensors
Rowe, D. J.; Repka, J.
1996-05-01
We present a set of tensors which are shift tensors (Wigner tensors) in accordance with the definitions of Biedenharn and Louck and satisfy the coherence conditions of Flath and Towber. Our tensors are defined for all connected compact Lie groups and for finite-dimensional representations of connected reductive Lie groups. Thus, we have a realization of the coherent tensors in a rather general setting. Moreover, this realization enables us to confirm most of the conjectures of Flath and Towber concerning the properties of coherent tensors.
Harder, G; Silberhorn, Ch; Rehacek, J; Hradil, Z; Motka, L; Stoklasa, B; Sánchez-Soto, L L
2016-04-01
We report the experimental point-by-point sampling of the Wigner function for nonclassical states created in an ultrafast pulsed type-II parametric down-conversion source. We use a loss-tolerant time-multiplexed detector based on a fiber-optical setup and a pair of photon-number-resolving avalanche photodiodes. By capitalizing on an expedient data-pattern tomography, we assess the properties of the light states with outstanding accuracy. The method allows us to reliably infer the squeezing of genuine two-mode states without any phase reference.
ORIGAMI: DELINEATING HALOS USING PHASE-SPACE FOLDS
Energy Technology Data Exchange (ETDEWEB)
Falck, Bridget L.; Neyrinck, Mark C.; Szalay, Alexander S. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
2012-08-01
We present the ORIGAMI method of identifying structures, particularly halos, in cosmological N-body simulations. Structure formation can be thought of as the folding of an initially flat three-dimensional manifold in six-dimensional phase space. ORIGAMI finds the outer folds that delineate these structures. Halo particles are identified as those that have undergone shell-crossing along three orthogonal axes, providing a dynamical definition of halo regions that is independent of density. ORIGAMI also identifies other morphological structures: particles that have undergone shell-crossing along 2, 1, or 0 orthogonal axes correspond to filaments, walls, and voids, respectively. We compare this method to a standard friends-of-friends halo-finding algorithm and find that ORIGAMI halos are somewhat larger, more diffuse, and less spherical, though the global properties of ORIGAMI halos are in good agreement with other modern halo-finding algorithms.
Aspects of phase-space noncommutative quantum mechanics
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O. Bertolami
2015-11-01
Full Text Available In this work some issues in the context of Noncommutative Quantum Mechanics (NCQM are addressed. The main focus is on finding whether symmetries present in Quantum Mechanics still hold in the phase-space noncommutative version. In particular, the issues related with gauge invariance of the electromagnetic field and the weak equivalence principle (WEP in the context of the gravitational quantum well (GQW are considered. The question of the Lorentz symmetry and the associated dispersion relation is also examined. Constraints are set on the relevant noncommutative parameters so that gauge invariance and Lorentz invariance holds. In opposition, the WEP is verified to hold in the noncommutative setup, and it is only possible to observe a violation through an anisotropy of the noncommutative parameters.
Analysis of PFG Anomalous Diffusion via Real-Space and Phase-Space Approaches
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Guoxing Lin
2018-01-01
Full Text Available Pulsed-field gradient (PFG diffusion experiments can be used to measure anomalous diffusion in many polymer or biological systems. However, it is still complicated to analyze PFG anomalous diffusion, particularly the finite gradient pulse width (FGPW effect. In practical applications, the FGPW effect may not be neglected, such as in clinical diffusion magnetic resonance imaging (MRI. Here, two significantly different methods are proposed to analyze PFG anomalous diffusion: the effective phase-shift diffusion equation (EPSDE method and a method based on observing the signal intensity at the origin. The EPSDE method describes the phase evolution in virtual phase space, while the method to observe the signal intensity at the origin describes the magnetization evolution in real space. However, these two approaches give the same general PFG signal attenuation including the FGPW effect, which can be numerically evaluated by a direct integration method. The direct integration method is fast and without overflow. It is a convenient numerical evaluation method for Mittag-Leffler function-type PFG signal attenuation. The methods here provide a clear view of spin evolution under a field gradient, and their results will help the analysis of PFG anomalous diffusion.
Generalizing the Boltzmann equation in complex phase space
Zadehgol, Abed
2016-08-01
In this work, a generalized form of the BGK-Boltzmann equation is proposed, where the velocity, position, and time can be represented by real or complex variables. The real representation leads to the conventional BGK-Boltzmann equation, which can recover the continuity and Navier-Stokes equations. We show that the complex representation yields a different set of equations, and it can also recover the conservation and Navier-Stokes equations, at low Mach numbers, provided that the imaginary component of the macroscopic mass can be neglected. We briefly review the Constant Speed Kinetic Model (CSKM), which was introduced in Zadehgol and Ashrafizaadeh [J. Comp. Phys. 274, 803 (2014), 10.1016/j.jcp.2014.06.053] and Zadehgol [Phys. Rev. E 91, 063311 (2015), 10.1103/PhysRevE.91.063311]. The CSKM is then used as a basis to show that the complex-valued equilibrium distribution function of the present model can be identified with a simple singularity in the complex phase space. The virtual particles, in the present work, are concentrated on virtual "branes" which surround the computational nodes. Employing the Cauchy integral formula, it is shown that certain variations of the "branes," in the complex phase space, do not affect the local kinetic states. This property of the new model, which is referred to as the "apparent jumps" in the present work, is used to construct new models. The theoretical findings have been tested by simulating three benchmark flows. The results of the present simulations are in excellent agreement with the previous results reported by others.
Sherkatghanad, Zeinab; Mirzaeyan, Zahra; Mansoori, Seyed Ali Hosseini
2014-01-01
We consider the critical behaviors and phase transitions of Gauss Bonnet-Born Infeld-AdS black holes (GB-BI-AdS) for $d=5,6$ and the extended phase space. We assume the cosmological constant, $\\Lambda$, the coupling coefficient $\\alpha$, and the BI parameter $\\beta$ to be thermodynamic pressures of the system. Having made these assumptions, the critical behaviors are then studied in the two canonical and grand canonical ensembles. We find "reentrant and triple point phase transitions" (RPT-TP) and "multiple reentrant phase transitions" (multiple RPT) with increasing pressure of the system for specific values of the coupling coefficient $\\alpha$ in the canonical ensemble. Also, we observe a reentrant phase transition (RPT) of GB-BI-AdS black holes in the grand canonical ensemble and for $d=6$. These calculations are then expanded to the critical behavior of Born-Infeld-AdS (BI-AdS) black holes in the third order of Lovelock gravity and in the grand canonical ensemble to find a Van der Waals behavior for $d=7$ ...
Position and Spin Operators, Wigner Rotation and the Origin of Hidden Momentum Forces
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O’Connell R. F.
2014-01-01
Full Text Available Using a position operator obtained for spin ½ particles by the present author and Wigner, we obtain a quantum relativistic result for the hidden momentum force experienced by particles with structure. In particular, our result applies to the hidden magnetic forces manifest in some problems of electromagnetism. We also discuss spin and orbital angular momentum operators, as well as Wigner rotation.
The phase-space structure of tidally stripped haloes
Drakos, Nicole E.; Taylor, James E.; Benson, Andrew J.
2017-06-01
We propose a new method for generating equilibrium models of spherical systems of collisionless particles that are finite in extent, but whose central regions resemble dark matter haloes from cosmological simulations. This method involves iteratively removing unbound particles from a Navarro-Frenk-White (NFW) profile truncated sharply at some radius. The resulting models are extremely stable, and thus provide a good starting point for N-body simulations of isolated haloes. We provide a code to generate such models for NFW and a variety of other common density profiles. We then develop an analytic approximation to this truncated distribution function. Our method proceeds by analogy with the King model, truncating and shifting the original distribution function of an infinitely extended NFW profile in energy space. We show that the density profiles of our models closely resemble the tidally truncated density profiles seen previously in studies of satellite evolution. Pursuing this analogy further with a series of simulations of tidal mass-loss, we find that our models provide a good approximation to the full distribution function of tidally stripped systems, thus allowing theoretically motivated phase-space calculations for such systems.
On Quantum Mechanics on Noncommutative Quantum Phase Space
Djemaï, A. E. F.; Smail, H.
2004-06-01
In this work, we develop a general framework in which Noncommutative Quantum Mechanics (NCQM), characterized by a space noncommutativity matrix parameter θ=ɛ^kijθ_k and a momentum noncommutativity matrix parameter βij=ɛ^kijβ_k, is shown to be equivalent to Quantum Mechanics (QM) on a suitable transformed Quantum Phase Space (QPS). Imposing some constraints on this particular transformation, we firstly find that the product of the two parameters θ and β possesses a lower bound in direct relation with Heisenberg incertitude relations, and secondly that the two parameters are equivalent but with opposite sign, up to a dimension factor depending on the physical system under study. This means that noncommutativity is represented by a unique parameter which may play the role of a fundamental constant characterizing the whole NCQPS. Within our framework, we treat some physical systems on NCQPS : free particle, harmonic oscillator, system of two-charged particles, Hydrogen atom. Among the obtained results, we discover a new phenomenon which consists of a free particle on NCQPS viewed as equivalent to a harmonic oscillator with Larmor frequency depending on β, representing the same particle in presence of a magnetic field B=q-1β. For the other examples, additional correction terms depending on β appear in the expression of the energy spectrum. Finally, in the two-particle system case, we emphasize the fact that for two opposite charges noncommutativity is effectively feeled with opposite sign.
Nonlinear Landau-Zener tunneling in quantum phase space
Energy Technology Data Exchange (ETDEWEB)
Trimborn, F [Institut fuer theoretische Physik, Leibniz Universitaet Hannover, D-30167 Hannover (Germany); Witthaut, D [QUANTOP, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); Kegel, V; Korsch, H J, E-mail: friederike.trimborn@itp.uni-hannover.d [Fachbereich Physik, TU Kaiserslautern, D-67663 Kaiserslautern (Germany)
2010-05-15
We present a detailed analysis of the Landau-Zener problem for an interacting Bose-Einstein condensate in a time-varying double-well trap, especially focusing on the relation between the full many-particle problem and the mean-field approximation. Due to the nonlinear self-interaction a dynamical instability occurs, which leads to a breakdown of adiabaticity and thus fundamentally alters the dynamics. It is shown that essentially all the features of the Landau-Zener problem including the depletion of the condensate mode can be already understood within a semiclassical phase-space picture. In particular, this treatment resolves the formerly imputed incommutability of the adiabatic and semiclassical limits. The possibility of exploiting Landau-Zener sweeps to generate squeezed states for spectroscopic tasks is analyzed in detail. Moreover, we study the influence of phase noise and propose a Landau-Zener sweep as a sensitive yet readily implementable probe for decoherence, since the noise has significant effect on the transition rate for slow parameter variations.
Hybrid phase-space-Fock-space approach to evolution of a driven nonlinear resonator
Khezri, Mostafa; Korotkov, Alexander N.
2017-10-01
We analyze the quantum evolution of a weakly nonlinear resonator due to a classical near-resonant drive and damping. The resonator nonlinearity leads to squeezing and heating of the resonator state. Using a hybrid phase-space-Fock-space representation for the resonator state within the Gaussian approximation, we derive evolution equations for the four parameters characterizing the Gaussian state. Numerical solution of these four ordinary differential equations is much simpler and faster than simulation of the full density matrix evolution, while providing good accuracy for the system analysis during transients and in the steady state. We show that steady-state squeezing of the resonator state is limited by 3 dB; however, this limit can be exceeded during transients.
Gelfert, Axel
2014-05-01
In his influential 1960 paper `The Unreasonable Effectiveness of Mathematics in the Natural Sciences', Eugene P. Wigner raises the question of why something that was developed without concern for empirical facts—mathematics—should turn out to be so powerful in explaining facts about the natural world. Recent philosophy of science has developed `Wigner's puzzle' in two different directions: First, in relation to the supposed indispensability of mathematical facts to particular scientific explanations and, secondly, in connection with the idea that aesthetic criteria track theoretical desiderata such as empirical success. An important aspect of Wigner's article has, however, been overlooked in these debates: his worries about the underdetermination of physical theories by mathematical frameworks. The present paper argues that, by restoring this aspect of Wigner's argument to its proper place, Wigner's puzzle may become an instructive case study for the teaching of core issues in the philosophy of science and its history.
Phase Space Dissimilarity Measures for Structural Health Monitoring
Energy Technology Data Exchange (ETDEWEB)
Bubacz, Jacob A [ORNL; Chmielewski, Hana T [ORNL; Pape, Alexander E [ORNL; Depersio, Andrew J [ORNL; Hively, Lee M [ORNL; Abercrombie, Robert K [ORNL; Boone, Shane [ORNL
2011-11-01
A novel method for structural health monitoring (SHM), known as the Phase Space Dissimilarity Measures (PSDM) approach, is proposed and developed. The patented PSDM approach has already been developed and demonstrated for a variety of equipment and biomedical applications. Here, we investigate SHM of bridges via analysis of time serial accelerometer measurements. This work has four aspects. The first is algorithm scalability, which was found to scale linearly from one processing core to four cores. Second, the same data are analyzed to determine how the use of the PSDM approach affects sensor placement. We found that a relatively low-density placement sufficiently captures the dynamics of the structure. Third, the same data are analyzed by unique combinations of accelerometer axes (vertical, longitudinal, and lateral with respect to the bridge) to determine how the choice of axes affects the analysis. The vertical axis is found to provide satisfactory SHM data. Fourth, statistical methods were investigated to validate the PSDM approach for this application, yielding statistically significant results.
Phase space of modified Gauss-Bonnet gravity
Energy Technology Data Exchange (ETDEWEB)
Carloni, Sante [Universidade de Lisboa-UL, Centro Multidisciplinar de Astrofisica-CENTRA, Instituto Superior Tecnico-IST, Lisbon (Portugal); Mimoso, Jose P. [Instituto de Astrofisica e Ciencias do Espaco, Universidade de Lisboa, Departamento de Fisica, Faculdade de Ciencias, Lisbon (Portugal)
2017-08-15
We investigate the evolution of non-vacuum Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetimes with any spatial curvature in the context of Gauss-Bonnet gravity. The analysis employs a new method which enables us to explore the phase space of any specific theory of this class. We consider several examples, discussing the transition from a decelerating into an acceleration universe within these theories. We also deduce from the dynamical equations some general conditions on the form of the action which guarantee the presence of specific behaviours like the emergence of accelerated expansion. As in f(R) gravity, our analysis shows that there is a set of initial conditions for which these models have a finite time singularity which can be an attractor. The presence of this instability also in the Gauss-Bonnet gravity is to be ascribed to the fourth-order derivative in the field equations, i.e., is the direct consequence of the higher order of the equations. (orig.)
Phase space of modified Gauss-Bonnet gravity
Carloni, Sante; Mimoso, José P.
2017-08-01
We investigate the evolution of non-vacuum Friedmann-Lemaître-Robertson-Walker (FLRW) spacetimes with any spatial curvature in the context of Gauss-Bonnet gravity. The analysis employs a new method which enables us to explore the phase space of any specific theory of this class. We consider several examples, discussing the transition from a decelerating into an acceleration universe within these theories. We also deduce from the dynamical equations some general conditions on the form of the action which guarantee the presence of specific behaviours like the emergence of accelerated expansion. As in f( R) gravity, our analysis shows that there is a set of initial conditions for which these models have a finite time singularity which can be an attractor. The presence of this instability also in the Gauss-Bonnet gravity is to be ascribed to the fourth-order derivative in the field equations, i.e., is the direct consequence of the higher order of the equations.
Covariant phase space, constraints, gauge and the Peierls formula
Khavkine, Igor
2014-02-01
It is well known that both the symplectic structure and the Poisson brackets of classical field theory can be constructed directly from the Lagrangian in a covariant way, without passing through the noncovariant canonical Hamiltonian formalism. This is true even in the presence of constraints and gauge symmetries. These constructions go under the names of the covariant phase space formalism and the Peierls bracket. We review both of them, paying more careful attention, than usual, to the precise mathematical hypotheses that they require, illustrating them in examples. Also an extensive historical overview of the development of these constructions is provided. The novel aspect of our presentation is a significant expansion and generalization of an elegant and quite recent argument by Forger and Romero showing the equivalence between the resulting symplectic and Poisson structures without passing through the canonical Hamiltonian formalism as an intermediary. We generalize it to cover theories with constraints and gauge symmetries and formulate precise sufficient conditions under which the argument holds. These conditions include a local condition on the equations of motion that we call hyperbolizability, and some global conditions of cohomological nature. The details of our presentation may shed some light on subtle questions related to the Poisson structure of gauge theories and their quantization.
National Aeronautics and Space Administration — In this SBIR Phase 1 we propose to develop a novel microscope by integrating Fourier phase contrast microscopy (FPCM) and epi-fluorescence microscopy. In FPCM, the...
High Performance Ka-band Phase Shifters for Space Telecommunications Project
National Aeronautics and Space Administration — We propose a novel MEMS-based digital phase shifter targeted for Ka-band operation, but scalable down to X-band and up to W-band. This novel phase shifter will...
Observation of the Wigner-Huntington transition to metallic hydrogen
Dias, Ranga P.; Silvera, Isaac F.
2017-02-01
Producing metallic hydrogen has been a great challenge in condensed matter physics. Metallic hydrogen may be a room-temperature superconductor and metastable when the pressure is released and could have an important impact on energy and rocketry. We have studied solid molecular hydrogen under pressure at low temperatures. At a pressure of 495 gigapascals, hydrogen becomes metallic, with reflectivity as high as 0.91. We fit the reflectance using a Drude free-electron model to determine the plasma frequency of 32.5 ± 2.1 electron volts at a temperature of 5.5 kelvin, with a corresponding electron carrier density of 7.7 ± 1.1 × 1023 particles per cubic centimeter, which is consistent with theoretical estimates of the atomic density. The properties are those of an atomic metal. We have produced the Wigner-Huntington dissociative transition to atomic metallic hydrogen in the laboratory.
Inoenue-Wigner contraction and D = 2 + 1 supergravity
Energy Technology Data Exchange (ETDEWEB)
Concha, P.K.; Rodriguez, E.K. [Universidad Adolfo Ibanez, Departamento de Ciencias, Facultad de Artes Liberales, Vina del Mar (Chile); Universidad Austral de Chile, Instituto de Ciencias Fisicas y Matematicas, Valdivia (Chile); Fierro, O. [Universidad Catolica de la Santisima Concepcion, Departamento de Matematica y Fisica Aplicadas, Concepcion (Chile)
2017-01-15
We present a generalization of the standard Inoenue-Wigner contraction by rescaling not only the generators of a Lie superalgebra but also the arbitrary constants appearing in the components of the invariant tensor. The procedure presented here allows one to obtain explicitly the Chern-Simons supergravity action of a contracted superalgebra. In particular we show that the Poincare limit can be performed to a D = 2 + 1 (p,q) AdS Chern-Simons supergravity in presence of the exotic form. We also construct a new three-dimensional (2,0) Maxwell Chern-Simons supergravity theory as a particular limit of (2,0) AdS-Lorentz supergravity theory. The generalization for N = p + q gravitinos is also considered. (orig.)
Microscopic-Macroscopic Mass Calculations with Wigner-Kirkwood expansion
Energy Technology Data Exchange (ETDEWEB)
Bhagwat, A [UM-DAE Centre for Excellence in Basic Sciences, Mumbai 400 098 (India); Vinas, X; Centelles, M [Departament d' Estructura i Constituents de la Materia and Institut de Ciencies del Cosmos, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona (Spain); Wyss, R [KTH (Royal Institute of Technology), Alba Nova University Center, Department of Nuclear Physics, S-10691 Stockholm (Sweden); Schuck, P, E-mail: ameeya@cbs.ac.in [Institut de Physique Nucleaire, IN2P3-CNRS, Universite Paris-Sud, F-91406 Orsay Cedex (France)
2011-09-16
The systematic study and calculation of ground state nuclear masses continues to be one of the active and important areas of research in nuclear physics. The present work is an attempt to determine the ground state masses of nuclei spanning the entire periodic table, using the Microscopic-Macroscopic approach. The semi-classical Wigner-Kirkwood (WK) h expansion method is used to calculate shell corrections for spherical and deformed nuclei. The expansion is achieved upto the fourth order in h. The shell corrections, along with the pairing energies obtained by using the Lipkin-Nogami scheme, constitute the microscopic part of the nuclear masses. The macroscopic part is obtained from a liquid drop formula with six adjustable parameters. It is shown that the Microscopic-Macroscopic mass calculation thus achieved, yields reliable description of ground state masses of nuclei across the periodic table. The present status of the WK mass calculations and the possible future perspectives are discussed.
Chemical Reactions Using a Non-Equilibrium Wigner Function Approach
Directory of Open Access Journals (Sweden)
Ramón F. Álvarez-Estrada
2016-10-01
Full Text Available A three-dimensional model of binary chemical reactions is studied. We consider an ab initio quantum two-particle system subjected to an attractive interaction potential and to a heat bath at thermal equilibrium at absolute temperature T > 0 . Under the sole action of the attraction potential, the two particles can either be bound or unbound to each other. While at T = 0 , there is no transition between both states, such a transition is possible when T > 0 (due to the heat bath and plays a key role as k B T approaches the magnitude of the attractive potential. We focus on a quantum regime, typical of chemical reactions, such that: (a the thermal wavelength is shorter than the range of the attractive potential (lower limit on T and (b ( 3 / 2 k B T does not exceed the magnitude of the attractive potential (upper limit on T. In this regime, we extend several methods previously applied to analyze the time duration of DNA thermal denaturation. The two-particle system is then described by a non-equilibrium Wigner function. Under Assumptions (a and (b, and for sufficiently long times, defined by a characteristic time scale D that is subsequently estimated, the general dissipationless non-equilibrium equation for the Wigner function is approximated by a Smoluchowski-like equation displaying dissipation and quantum effects. A comparison with the standard chemical kinetic equations is made. The time τ required for the two particles to transition from the bound state to unbound configurations is studied by means of the mean first passage time formalism. An approximate formula for τ, in terms of D and exhibiting the Arrhenius exponential factor, is obtained. Recombination processes are also briefly studied within our framework and compared with previous well-known methods.
Field theoretic perspectives of the Wigner function formulation of the chiral magnetic effect
Wu, Yan; Hou, De-fu; Ren, Hai-cang
2017-11-01
We assess the applicability of the Wigner function formulation in its present form to the chiral magnetic effect and note some issues regarding the conservation and the consistency of the electric current in the presence of an inhomogeneous and time-dependent axial chemical potential. The problems are rooted in the ultraviolet divergence of the underlying field theory associated with the axial anomaly and can be fixed with the Pauli-Villars regularization of the Wigner function. The chiral magnetic current with a nonconstant axial chemical potential is calculated with the regularized Wigner function and the phenomenological implications are discussed.
Generalised partition functions: inferences on phase space distributions
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R. A. Treumann
2016-06-01
Full Text Available It is demonstrated that the statistical mechanical partition function can be used to construct various different forms of phase space distributions. This indicates that its structure is not restricted to the Gibbs–Boltzmann factor prescription which is based on counting statistics. With the widely used replacement of the Boltzmann factor by a generalised Lorentzian (also known as the q-deformed exponential function, where κ = 1∕|q − 1|, with κ, q ∈ R both the kappa-Bose and kappa-Fermi partition functions are obtained in quite a straightforward way, from which the conventional Bose and Fermi distributions follow for κ → ∞. For κ ≠ ∞ these are subject to the restrictions that they can be used only at temperatures far from zero. They thus, as shown earlier, have little value for quantum physics. This is reasonable, because physical κ systems imply strong correlations which are absent at zero temperature where apart from stochastics all dynamical interactions are frozen. In the classical large temperature limit one obtains physically reasonable κ distributions which depend on energy respectively momentum as well as on chemical potential. Looking for other functional dependencies, we examine Bessel functions whether they can be used for obtaining valid distributions. Again and for the same reason, no Fermi and Bose distributions exist in the low temperature limit. However, a classical Bessel–Boltzmann distribution can be constructed which is a Bessel-modified Lorentzian distribution. Whether it makes any physical sense remains an open question. This is not investigated here. The choice of Bessel functions is motivated solely by their convergence properties and not by reference to any physical demands. This result suggests that the Gibbs–Boltzmann partition function is fundamental not only to Gibbs–Boltzmann but also to a large class of generalised Lorentzian distributions as well as to the
Garcia-Gasco Trujillo, Javier; Noval Sánchez de Toca, Alvaro; Montesinos Ortego, Ignacio; Fernández González, José Manuel; Sierra Pérez, Manuel
2013-01-01
The Space Situational Awareness (SSA) program from the European Space Agency (ESA) protects Europe's citizens and their satellite-based services by detecting space hazards. ESA Ground Systems (GS) division is currently designing a phased array radar composed of thousands of radiating elements for future stages of the SSA program [1]. The radar shall guarantee the detection of most of the Low Earth Orbit (LEO) space debris, providing a general map of space junk. While range accuracy is mainly ...
Variational principle and phase space measure in non-canonical coordinates
Directory of Open Access Journals (Sweden)
Sergi, A
2005-11-01
Full Text Available Non-canonical equations of motion are derived from a variational principle written in symplectic form. The invariant measure of phase space and the covariant expression for the entropy are derived from non-canonical transformations of coordinates. This shows that the geometry of non-canonical phase space is non trivial even if dynamics has no compressibility.
Higher order point and continuum mechanics from phase-space action
Energy Technology Data Exchange (ETDEWEB)
Shamanna, J.; Talukdar, B.; Das, U
2002-12-02
It is pointed out that use of phase-space action provides an elegant method to study the canonical structure of problems in mechanics. Higher order Lagrangian systems are Hamiltonized by employing the variational principle in phase space. Studies are envisaged for both particle dynamics and field theory. Hamilton's equations are expressed in terms of appropriate Poisson brackets.
Wigner-like crystallization of Anderson-localized electron systems with low electron densities
Slutskin, A A; Pepper, M
2002-01-01
We consider an electron system under conditions of strong Anderson localization, taking into account interelectron long-range Coulomb repulsion. We establish that at sufficiently low electron densities and sufficiently low temperatures the Coulomb electron interaction brings about ordering of the Anderson-localized electrons into a structure that is close to an ideal (Wigner) crystal lattice, provided the dimension of the system is > 1. This Anderson-Wigner glass (AWG) is a new macroscopic electron state that, on the one hand, is beyond the conventional Fermi glass concept, and on the other hand, qualitatively differs from the known 'plain' Wigner glass (inherent in self-localized electron systems) in that the random slight electron displacements from the ideal crystal sites essentially depend on the electron density. With increasing electron density the AWG is found to turn into the plain Wigner glass or Fermi glass, depending on the width of the random spread of the electron levels. It is shown that the res...
Efficient characterization of phase space mapping in axially symmetric optical systems
Barbero, Sergio; Portilla, Javier
2018-01-01
Phase space mapping, typically between an object and image plane, characterizes an optical system within a geometrical optics framework. We propose a novel conceptual frame to characterize the phase mapping in axially symmetric optical systems for arbitrary object locations, not restricted to a specific object plane. The idea is based on decomposing the phase mapping into a set of bivariate equations corresponding to different values of the radial coordinate on a specific object surface (most likely the entrance pupil). These equations are then approximated through bivariate Chebyshev interpolation at Chebyshev nodes, which guarantees uniform convergence. Additionally, we propose the use of a new concept (effective object phase space), defined as the set of points of the phase space at the first optical element (typically the entrance pupil) that are effectively mapped onto the image surface. The effective object phase space provides, by means of an inclusion test, a way to avoid tracing rays that do not reach the image surface.
Directory of Open Access Journals (Sweden)
Ivan V. Bazarov
2008-10-01
Full Text Available We present a comparison between space charge calculations and direct measurements of the transverse phase space of space charge dominated electron bunches from a high voltage dc photoemission gun followed by an emittance compensation solenoid magnet. The measurements were performed using a double-slit emittance measurement system over a range of bunch charge and solenoid current values. The data are compared with detailed simulations using the 3D space charge codes GPT and Parmela3D. The initial particle distributions were generated from measured transverse and temporal laser beam profiles at the photocathode. The beam brightness as a function of beam fraction is calculated for the measured phase space maps and found to approach within a factor of 2 the theoretical maximum set by the thermal energy and the accelerating field at the photocathode.
Families of vector-like deformations of relativistic quantum phase spaces, twists and symmetries
Meljanac, Daniel; Meljanac, Stjepan; Pikutić, Danijel
2017-12-01
Families of vector-like deformed relativistic quantum phase spaces and corresponding realizations are analyzed. A method for a general construction of the star product is presented. The corresponding twist, expressed in terms of phase space coordinates, in the Hopf algebroid sense is presented. General linear realizations are considered and corresponding twists, in terms of momenta and Poincaré-Weyl generators or gl(n) generators are constructed and R-matrix is discussed. A classification of linear realizations leading to vector-like deformed phase spaces is given. There are three types of spaces: (i) commutative spaces, (ii) κ -Minkowski spaces and (iii) κ -Snyder spaces. The corresponding star products are (i) associative and commutative (but non-local), (ii) associative and non-commutative and (iii) non-associative and non-commutative, respectively. Twisted symmetry algebras are considered. Transposed twists and left-right dual algebras are presented. Finally, some physical applications are discussed.
Space Station Freedom - Approaching the critical design phase
Kohrs, Richard H.; Huckins, Earle, III
1992-01-01
The status and future developments of the Space Station Freedom are discussed. To date detailed design drawings are being produced to manufacture SSF hardware. A critical design review (CDR) for the man-tended capability configuration is planned to be performed in 1993 under the SSF program. The main objective of the CDR is to enable the program to make a full commitment to proceed to manufacture parts and assemblies. NASA recently signed a contract with the Russian space company, NPO Energia, to evaluate potential applications of various Russian space hardware for on-going NASA programs.
Multimegawatt space nuclear power supply: Phase 1, Final report
Energy Technology Data Exchange (ETDEWEB)
1989-02-17
The Phase 2 program objectives are to (1) demonstrate concept feasibility, (2) develop a preliminary design, and (3) complete Phase 3 engineering development and ground test plans. The approach to accomplish these objectives is to prove technical feasibility of our baseline design early in the program while maintaining flexibility to easily respond to changing requirements and advances in technology. This approach recognizes that technology is advancing rapidly while the operational phase MSNPS is 15 to 20 years in the future. This plan further recognizes that the weapons platform and Advanced Launch System (ALS) are in very early program definition stages; consequently, their requirements, interfaces, and technological basis will evolve. This document outlines the Phase 2 plan along with task scheduling of the various program aspects.
Pseudosymmetric random matrices: Semi-Poisson and sub-Wigner statistics
Kumar, Sachin; Ahmed, Zafar
2017-08-01
Real nonsymmetric matrices may have either real or complex conjugate eigenvalues. These matrices can be seen to be pseudosymmetric as η M η-1=Mt , where the metric η could be secular (a constant matrix) or depending upon the matrix elements of M . Here we construct ensembles of a large number N of pseudosymmetric n ×n (n large) matrices using N [n (n +1 ) /2 ≤N ≤n2] independent and identically distributed random numbers as their elements. Based on our numerical calculations, we conjecture that for these ensembles the nearest level spacing distributions [NLSDs, p (s )] are sub-Wigner as pa b c(s ) =a s e-b sc(0 topological transitions in a Josephson junction. Interestingly, p (s ) for c =1 is called semi-Poisson, and we show that it lies close to the form p (s ) =0.59 s K0(0.45 s2) derived for the case of 2 ×2 pseudosymmetric matrix where the eigenvalues are most aptly conditionally real, E1 ,2=a ±√{b2-c2 } , which represent characteristic coalescing of eigenvalues in parity-time (PT) -symmetric systems.
Novel low Wigner energy amorphous carbon-carbon composite
Dasgupta, Kinshuk; Prakash, Jyoti; Tripathi, B. M.
2014-02-01
A novel amorphous carbon-carbon composite has been developed using carbon black dispersed in carbonized phenolic resin matrix in order to avoid Wigner energy problem associated with graphite. The as prepared sample showed a density of 1320 kg m-3. This has been further densified by resin impregnation and chemical vapour infiltration. The effect of processing parameters on final density (1517 kg m-3) has been investigated. This composite possesses the compressive strength of 65 Mpa, coefficient of thermal expansion of 3 × 10-6 K-1 and the specific heat of 1.2 J g-1 K-1. This novel composite was subjected to 145 MeV Ne+6 heavy ion irradiation at different doses. The highest dose was kept at 3 × 10-4 dpa. The stored energy in the composite was found to be 212 J g-1 at the highest dose of irradiation, which is much below than that of graphite. The composite remained amorphous after irradiation as confirmed by X-ray diffraction.
Novel low Wigner energy amorphous carbon–carbon composite
Energy Technology Data Exchange (ETDEWEB)
Dasgupta, Kinshuk, E-mail: kdg@barc.gov.in; Prakash, Jyoti; Tripathi, B.M.
2014-02-01
A novel amorphous carbon–carbon composite has been developed using carbon black dispersed in carbonized phenolic resin matrix in order to avoid Wigner energy problem associated with graphite. The as prepared sample showed a density of 1320 kg m{sup −3}. This has been further densified by resin impregnation and chemical vapour infiltration. The effect of processing parameters on final density (1517 kg m{sup −3}) has been investigated. This composite possesses the compressive strength of 65 Mpa, coefficient of thermal expansion of 3 × 10{sup −6} K{sup −1} and the specific heat of 1.2 J g{sup −1} K{sup −1}. This novel composite was subjected to 145 MeV Ne{sup +6} heavy ion irradiation at different doses. The highest dose was kept at 3 × 10{sup −4} dpa. The stored energy in the composite was found to be 212 J g{sup −1} at the highest dose of irradiation, which is much below than that of graphite. The composite remained amorphous after irradiation as confirmed by X-ray diffraction.
Observation of the Wigner-Huntington transition to metallic hydrogen.
Dias, Ranga P; Silvera, Isaac F
2017-02-17
Producing metallic hydrogen has been a great challenge in condensed matter physics. Metallic hydrogen may be a room-temperature superconductor and metastable when the pressure is released and could have an important impact on energy and rocketry. We have studied solid molecular hydrogen under pressure at low temperatures. At a pressure of 495 gigapascals, hydrogen becomes metallic, with reflectivity as high as 0.91. We fit the reflectance using a Drude free-electron model to determine the plasma frequency of 32.5 ± 2.1 electron volts at a temperature of 5.5 kelvin, with a corresponding electron carrier density of 7.7 ± 1.1 × 1023 particles per cubic centimeter, which is consistent with theoretical estimates of the atomic density. The properties are those of an atomic metal. We have produced the Wigner-Huntington dissociative transition to atomic metallic hydrogen in the laboratory. Copyright © 2017, American Association for the Advancement of Science.
Equilibrium Phase Behavior of a Continuous-Space Microphase Former.
Zhuang, Yuan; Zhang, Kai; Charbonneau, Patrick
2016-03-04
Periodic microphases universally emerge in systems for which short-range interparticle attraction is frustrated by long-range repulsion. The morphological richness of these phases makes them desirable material targets, but our relatively coarse understanding of even simple models hinders controlling their assembly. We report here the solution of the equilibrium phase behavior of a microscopic microphase former through specialized Monte Carlo simulations. The results for cluster crystal, cylindrical, double gyroid, and lamellar ordering qualitatively agree with a Landau-type free energy description and reveal the nontrivial interplay between cluster, gel, and microphase formation.
Transverse emittance and phase space program developed for use at the Fermilab A0 Photoinjector
Energy Technology Data Exchange (ETDEWEB)
Thurman-Keup, R.; Johnson, A.S.; Lumpkin, A.H.; Ruan, J.; /Fermilab
2011-03-01
The Fermilab A0 Photoinjector is a 16 MeV high intensity, high brightness electron linac developed for advanced accelerator R&D. One of the key parameters for the electron beam is the transverse beam emittance. Here we report on a newly developed MATLAB based GUI program used for transverse emittance measurements using the multi-slit technique. This program combines the image acquisition and post-processing tools for determining the transverse phase space parameters with uncertainties. An integral part of accelerator research is a measurement of the beam phase space. Measurements of the transverse phase space can be accomplished by a variety of methods including multiple screens separated by drift spaces, or by sampling phase space via pepper pots or slits. In any case, the measurement of the phase space parameters, in particular the emittance, can be drastically simplified and sped up by automating the measurement in an intuitive fashion utilizing a graphical interface. At the A0 Photoinjector (A0PI), the control system is DOOCS, which originated at DESY. In addition, there is a library for interfacing to MATLAB, a graphically capable numerical analysis package sold by The Mathworks. It is this graphical package which was chosen as the basis for a graphical phase space measurement system due to its combination of analysis and display capabilities.
On phase-space representations of quantum mechanics using ...
Indian Academy of Sciences (India)
2016-07-16
-space wave functions using the Glauber coherent states [2,23–25] and the Husimi amplitude, 〈z | (t)〉. Thus, in order to put into con- text the present paper, some previous literature in this area of research (`a la Bargmann) will ...
Deep Space Habitat Concept of Operations for Transit Mission Phases
Hoffman, Stephen J.
2011-01-01
The National Aeronautics and Space Administration (NASA) has begun evaluating various mission and system components of possible implementations of what the U.S. Human Spaceflight Plans Committee (also known as the Augustine Committee) has named the flexible path (Anon., 2009). As human spaceflight missions expand further into deep space, the duration of these missions increases to the point where a dedicated crew habitat element appears necessary. There are several destinations included in this flexible path a near Earth asteroid (NEA) mission, a Phobos/Deimos (Ph/D) mission, and a Mars surface exploration mission that all include at least a portion of the total mission in which the crew spends significant periods of time (measured in months) in the deep space environment and are thus candidates for a dedicated habitat element. As one facet of a number of studies being conducted by the Human Spaceflight Architecture Team (HAT) a workshop was conducted to consider how best to define and quantify habitable volume for these future deep space missions. One conclusion reached during this workshop was the need for a description of the scope and scale of these missions and the intended uses of a habitat element. A group was set up to prepare a concept of operations document to address this need. This document describes a concept of operations for a habitat element used for these deep space missions. Although it may eventually be determined that there is significant overlap with this concept of operations and that of a habitat destined for use on planetary surfaces, such as the Moon and Mars, no such presumption is made in this document.
Study of a measurement of beam distribution on the phase space in the space charge dominant region
Energy Technology Data Exchange (ETDEWEB)
Nomura, Masahiro [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center
1998-06-01
Beam distribution on the phase space which is figured by the emittance and Twiss parameters is one of the most important parameters when applications and performance of accelerator are studied. In the high energy region where the space charge effect is week, the emittance is measured by a quadrupole magnet and in the space charge dominant region, the pepper-pot technique is used. I studied a method to measure the beam distribution on the phase space by magnetic lenses in the space charge dominant region. In this method, an initial beam distribution is figured by parameters such as a momentum spread, a waist position and a beam radius at the exit of gun instead of Twiss parameters. And the beam trajectory and radius are calculated by a new simulation code instead of transfer matrix because transfer matrix can not be used in the space charge dominant region. I developed a new one dimensional simulation code. In this code, when the space charge force is calculated, a mesh size is changed automatically according to the beam radius in order to reduce the calculation error. The relations between the beam radius and strength of the magnetic lenses were calculated by this simulation code. The results show that the waist position and the beam radius at the exit of gun can be estimated from those relations. (author)
Interacton-driven phenomena and Wigner transition in two-dimensional systems
Knighton, Talbot
The formation of a quantum Wigner Cyrstal (WC) is one of the most anticipated predictions of electron-electron interaction. This is expected to occur in zero magnetic field when the Coulomb energy EC dominates over the Fermi energy EF (at a ratio rs ≡ EC/ EF ˜ 37) for temperatures T High purity systems with large interaction rs >1 tend to exhibit reentrant insulating phases (RIP) between the integer and fractional Hall states. These are suspected to be a form of WC, but the evidence is not yet conclusive. We use transport measurements to identify a conduction threshold in the RIP at filling factor nu = 0.37 (close to the 1/3 state) that is several orders of magnitude larger than the pinning observed in many other systems. We analyze the temperature and electric E-field dependence of this insulating phase and find them to be consistent with a second-order phase transition to WC. The measurements are performed on dilute holes p = 4 x 1010 cm-2 of mobility mu = 1/perho ˜ 2.5 x 106 cm 2/Vs in 20 nm GaAs/AlGaAs quantum square wells. We also discuss various other projects related to the study of topological states and strongly interacting charges: direct testing of the bulk conduction in a developing quantum Hall state using a corbino-disk-like geometry (or "anti-Hall bar"); preliminary results for ultra dilute charges in undoped heterojunction insulated gated field effect transistors; quantum capacitance measurement of the density of states across the vanadium dioxide metal insulator transition; progress towards a scanning capacitance measurement using the tip of an atomic force microscope; and graphene devices for optical detection.
Phase space investigation of the lithium amide halides
Energy Technology Data Exchange (ETDEWEB)
Davies, Rosalind A. [Hydrogen Storage Chemistry Group, School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Hydrogen and Fuel Cell Group, School of Chemical Engineering, University of Birmingham, Edgbaston B15 2TT (United Kingdom); Hewett, David R.; Korkiakoski, Emma [Hydrogen Storage Chemistry Group, School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Thompson, Stephen P. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX (United Kingdom); Anderson, Paul A., E-mail: p.a.anderson@bham.ac.uk [Hydrogen Storage Chemistry Group, School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)
2015-10-05
Highlights: • The lower limits of halide incorporation in lithium amide have been investigated. • The only amide iodide stoichiometry observed was Li{sub 3}(NH{sub 2}){sub 2}I. • Solid solutions were observed in both the amide chloride and amide bromide systems. • A 46% reduction in chloride content resulted in a new phase: Li{sub 7}(NH{sub 2}){sub 6}Cl. • New low-chloride phase maintained improved H{sub 2} desorption properties of Li{sub 4}(NH{sub 2}){sub 3}Cl. - Abstract: An investigation has been carried out into the lower limits of halide incorporation in lithium amide (LiNH{sub 2}). It was found that the lithium amide iodide Li{sub 3}(NH{sub 2}){sub 2}I was unable to accommodate any variation in stoichiometry. In contrast, some variation in stoichiometry was accommodated in Li{sub 7}(NH{sub 2}){sub 6}Br, as shown by a decrease in unit cell volume when the bromide content was reduced. The amide chloride Li{sub 4}(NH{sub 2}){sub 3}Cl was found to adopt either a rhombohedral or a cubic structure depending on the reaction conditions. Reduction in chloride content generally resulted in a mixture of phases, but a new rhombohedral phase with the stoichiometry Li{sub 7}(NH{sub 2}){sub 6}Cl was observed. In comparison to LiNH{sub 2}, this new low-chloride phase exhibited similar improved hydrogen desorption properties as Li{sub 4}(NH{sub 2}){sub 3}Cl but with a much reduced weight penalty through addition of chloride. Attempts to dope lithium amide with fluoride ions have so far proved unsuccessful.
Nishigaki, Shinsuke M.
2012-12-01
Schierenberg [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.061130 85, 061130 (2012)] recently applied the Wigner surmise, i.e., substitution of ∞×∞ matrices by their 2×2 counterparts for the computation of level spacing distributions, to random matrix ensembles in transition between two universality classes. I examine the accuracy and the range of validity of the surmise for the crossover between the Gaussian orthogonal and unitary ensembles by contrasting them with the large-N results that I evaluated using the Nyström-type method for the Fredholm determinant. The surmised expression at the best-fitting parameter provides a good approximation for 0≲s≲2, i.e., the validity range of the original surmise.
Selection of Phase Space Reconstruction Parameters for EMG Signals of the Uterus
Directory of Open Access Journals (Sweden)
Brzozowska Ewelina
2016-12-01
Full Text Available Biological time series have a finite number of samples with noise included in them. Because of this fact, it is not possible to reconstruct phase space in an ideal manner. One kind of biomedical signals are electrohisterographical (EHG datasets, which represent uterine muscle contractile activity. In the process of phase space reconstruction, the most important thing is suitable choice of the method for calculating the time delay τ and embedding dimension d, which will reliably reconstruct the original signal. The parameters used in digital signal processing are key to arranging adequate parameters of the analysed attractor embedded in the phase space. The aim of this paper is to present a method employed for phase space reconstruction for EHG signals that will make it possible for their further analysis to be carried out.
Phase Space of Rolling Solutions of the Tippe Top
Directory of Open Access Journals (Sweden)
S. Torkel Glad
2007-03-01
Full Text Available Equations of motion of an axially symmetric sphere rolling and sliding on a plane are usually taken as model of the tippe top. We study these equations in the nonsliding regime both in the vector notation and in the Euler angle variables when they admit three integrals of motion that are linear and quadratic in momenta. In the Euler angle variables (θ,φ,ψ these integrals give separation equations that have the same structure as the equations of the Lagrange top. It makes it possible to describe the whole space of solutions by representing them in the space of parameters (D,λ,E being constant values of the integrals of motion.
Phase-space dynamics of runaway electrons in magnetic fields
Guo, Zehua; McDevitt, Christopher J.; Tang, Xian-Zhu
2017-04-01
Dynamics of runaway electrons in magnetic fields are governed by the competition of three dominant physics: parallel electric field acceleration, Coulomb collision, and synchrotron radiation. Examination of the energy and pitch-angle flows reveals that the presence of local vortex structure and global circulation is crucial to the saturation of primary runaway electrons. Models for the vortex structure, which has an O-point to X-point connection, and the bump of runaway electron distribution in energy space have been developed and compared against the simulation data. Identification of these velocity-space structures opens a new venue to re-examine the conventional understanding of runaway electron dynamics in magnetic fields.
ACOSS FIVE (Active Control of Space Structures). Phase 1A
1982-03-01
Again, in this case the specimen had been perturbed by a four-second chirp and then allowed to settle. Once a filter design has been established , the...The control design MKUCTUKAL MOOC L PtRFOHMANCl MÜDtL DISTURBANCE MODEL I ’ II Q|S£) XM=) STATE SPACE MODEL KEDUCED MODELS (HAC... establishing robustness with respect to two "point- design " perturbations. Based on the above results, and in the context of the analysis defined by the
A simulation of weak-light phase-locking for space laser interferometer
Li, Y. Q.; Dong, Y. H.; Liu, H. S.; Luo, Z. R.; Jin, G.
2017-05-01
A simulation was investigated to better understand the impacts and effects of the additional technical noises on weak-light phase-locking for space laser interferometer. The result showed that the locking precision was limited by the phase readout noise when the laser frequency noise and clock jitter noise were removed, and this result was then confirmed by a benchtop experimental test. The required space laser interferometer noise floor was recovered from the simulation which proved the validity of the simulation program.
Phase-space Analysis in the Group and Cluster Environment: Introduction and Application
Rhee, Jinsu
2018-01-01
Using the latest cosmological hydrodynamic N-body simulations of groups and clusters, we study how location in phase-space coordinates at z = 0 can provide information on environmental effects acting in clusters. We confirm the results of previous authors showing that galaxies tend to follow a typical path in phase-space as they settle into the cluster potential. As such, different regions of phase-space can be associated with different times since first infalling into the cluster. However, in addition, we see a clear trend between total mass loss due to cluster tides and time since infall. Thus, we find location in phase-space provides information on both infall time and tidal mass loss. We find the predictive power of phase-space diagrams remains even when projected quantities are used (i.e., line of sight velocities, and projected distances from the cluster). We provide figures that can be directly compared with observed samples of cluster galaxies and we also provide the data used to make them as supplementary data to encourage the use of phase-space diagrams as a tool to understand cluster environmental effects. We find that our results depend very weakly on galaxy mass or host mass, so the predictions in our phase-space diagrams can be applied to groups or clusters alike, or to galaxy populations from dwarfs up to giants. Finally, we give some guiding examples how our phase-space diagrams can be used in real observation, inferring time evolution of galaxy properties under cluster environment.
Wang, Rui-Ning; Dong, Guo-Yi; Wang, Shu-Fang; Fu, Guang-Sheng; Wang, Jiang-Long
2016-11-01
Quantum interference is a well-known phenomenon which results in unique features of the transmission spectra of molecular junctions at the nanoscale. We investigate and compare the thermoelectric properties of three types of junctions like the anti, Breit-Wigner, and Fano resonances. Due to its asymmetric line-shaped transmission function, Fano resonances lead to a larger thermoelectric figure of merit (ZT) than the symmetric anti and Breit-Wigner resonances. The occurrence of quantum interference in molecular and other nanoscale junctions is independent of contact couplings between the sandwiched molecules and left/right electrodes. However, it is found that the contact couplings determine the electric and thermoelectric performances of quantum interference junctions. In anti-resonant junctions, the Seebeck coefficient is enhanced by strong contact couplings. By contrast, for Breit-Wigner resonant junctions, this same property will increase in the weak contact coupling regime. Contrary to what is observed for anti and Breit-Wigner resonant junctions, some optimal contact couplings are found in Fano-resonant junctions for which the maximum Seebeck coefficient and ZT are obtained. Finally, thermoelectric properties are also investigated when the resonances crossover from Breit-Wigner to Fano types and, subsequently, to anti resonances.
Field diversity phase retrieval method for wavefront sensing in monolithic mirror space telescopes.
Ju, Guohao; Yan, Changxiang; Yue, Dan; Gu, Zhiyuan
2017-05-20
To guarantee the uniqueness of the solution for the wavefront phase, a series of intensity images with known phase diversities is usually needed in the current phase retrieval wavefront sensing methods. However, to obtain these intensity images with deliberately added diversity phases, some additional instruments (e.g., beam splitters) or operations (e.g., adjustment of the focus) are usually needed, which can pose a challenge for wavefront sensing in space telescopes. This paper proposes a new concept for retrieving the wavefront phase of monolithic mirror space telescopes with perturbations, where the intensity measurements with phase diversities are directly obtained from different field positions of one image, without the need for any additional instruments or operations. To realize this new concept, we present a modified phase diversity method to account for the unknown phase diversities between these intensity measurements based on an in-depth understanding of the net aberration fields induced by misalignments and figure errors. Relevant simulations for different cases are performed to demonstrate the feasibility and accuracy of the proposed method. Since in this method the phase diversities between different intensity measurements are mainly induced by the diversities in the field position, we call it the field diversity phase retrieval method. This work can present great facility for wavefront sensing in monolithic mirror space telescopes.
Critical phenomena experiments in space. [for fluid phase-equilibrium
Sengers, J. V.; Moldover, M. R.
1978-01-01
The paper analyzes several types of critical phenomena in fluids, shows how they are affected by the presence of gravity, and describes how experiments conducted in an orbiting laboratory under low gravity conditions could extend the range of measurements needed to study critical phenomena. Future experiments are proposed. One would be a careful measurement of the dielectric constant in a low gravity environment. Two basic problems that can benefit especially from space experiments are the specific heat near the critical point and the shear viscosity at the gas-liquid critical point.
Analysis of Scalar Field Cosmology with Phase Space Deformations
Directory of Open Access Journals (Sweden)
Sinuhe Perez-Payan
2014-01-01
modifying the symplectic structure of the minisuperspace variables. The effects of the deformation are studied in the “C-frame” and the “NC-frame.” In order to remove the ambiguities of working on different frames, a new principle is introduced. When we impose that both frames should be physically equivalent, we conclude that the only possibility for this model, is to have an effective cosmological constant Λeff≥0. Finally we bound the parameter space for θ and β.
Space qualified Nd:YAG laser (phase 1 - design)
Foster, J. D.; Kirk, R. F.
1971-01-01
Results of a design study and preliminary design of a space qualified Nd:YAG laser are presented. A theoretical model of the laser was developed to allow the evaluation of the effects of various parameters on its performance. Various pump lamps were evaluated and sum pumping was considered. Cooling requirements were examined and cooling methods such as radiation, cryogenic and conductive were analysed. Power outputs and efficiences of various configurations and the pump and laser lifetime are discussed. Also considered were modulation and modulating methods.
Phase-space quantum mechanics study of two identical particles in an external oscillatory potential
Nieto, Luis M.; Gadella, Manuel
1993-01-01
This simple example is used to show how the formalism of Moyal works when it is applied to systems of identical particles. The symmetric and antisymmetric Moyal propagators are evaluated for this case; from them, the correct energy levels of energy are obtained, as well as the Wigner functions for the symmetric and antisymmetric states of the two identical particle system. Finally, the solution of the Bloch equation is straightforwardly obtained from the expressions of the Moyal propagators.
On evolution of small spheres in the phase space of a dynamical system*
Directory of Open Access Journals (Sweden)
Komech Sergei
2012-08-01
Full Text Available We study the connection between the entropy of a dynamical system and the boundary distortion rate of regions in the phase space of the system. Nous étudions la connexion entre l’entropie d’un système dynamique et le taux de distortion au bord dans l’espace des phases du système.
Phase 1 space fission propulsion system testing and development progress
van Dyke, Melissa; Houts, Mike; Pedersen, Kevin; Godfroy, Tom; Dickens, Ricky; Poston, David; Reid, Bob; Salvail, Pat; Ring, Peter
2001-02-01
Successful development of space fission systems will require an extensive program of affordable and realistic testing. In addition to tests related to design/development of the fission system, realistic testing of the actual flight unit must also be performed. Testing can be divided into two categories, non-nuclear tests and nuclear tests. Full power nuclear tests of space fission systems are expensive, time consuming, and of limited use, even in the best of programmatic environments. If the system is designed to operate within established radiation damage and fuel burn up limits while simultaneously being designed to allow close simulation of heat from fission using resistance heaters, high confidence in fission system performance and lifetime can be attained through a series of non-nuclear tests. Non-nuclear tests are affordable and timely, and the cause of component and system failures can be quickly and accurately identified, MSFC is leading a Safe Affordable Fission Engine (SAFE) test series whose ultimate goal is the demonstration of a 300 kW flight configuration system using non-nuclear testing. This test series is carried out in collaboration with other NASA centers, other government agencies, industry, and universities. If SAFE-related nuclear tests are desired, they will have a high probability of success and can be performed at existing nuclear facilities. The paper describes the SAFE non-nuclear test series, which includes test article descriptions, test results and conclusions, and future test plans. .
Proliferation of stability in phase and parameter spaces of nonlinear systems
Manchein, Cesar; da Silva, Rafael M.; Beims, Marcus W.
2017-08-01
In this work, we show how the composition of maps allows us to multiply, enlarge, and move stable domains in phase and parameter spaces of discrete nonlinear systems. Using Hénon maps with distinct parameters, we generate many identical copies of isoperiodic stable structures (ISSs) in the parameter space and attractors in phase space. The equivalence of the identical ISSs is checked by the largest Lyapunov exponent analysis, and the multiplied basins of attraction become riddled. Our proliferation procedure should be applicable to any two-dimensional nonlinear system.
Phase-space representation and polarization domains of random electromagnetic fields.
Castaneda, Roman; Betancur, Rafael; Herrera, Jorge; Carrasquilla, Juan
2008-08-01
The phase-space representation of stationary random electromagnetic fields is developed by using electromagnetic spatial coherence wavelets. The propagation of the field's power and states of spatial coherence and polarization results from correlations between the components of the field vectors at pairs of points in space. Polarization domains are theoretically predicted as the structure of the field polarization at the observation plane. In addition, the phase-space representation provides a generalization of the Poynting theorem. Theoretical predictions are examined by numerically simulating the Young experiment with electromagnetic waves. The experimental implementation of these results is a current subject of research.
New Space Vector Selection Scheme for VSI Supplied Dual Three-Phase Induction Machine
Directory of Open Access Journals (Sweden)
MILICEVIC, D.
2013-02-01
Full Text Available This paper presents a novel space vector selection scheme applicable for the control of dual three-phase induction motor drives supplied from a six-phase voltage source inverter (VSI. The vector selection method is based on the vector space decomposition technique (VSD. Unique vector selection pattern simplifies problems related to complicated implementation of standard VSD in commercially available digital signals processors (DSP. The proposed vector selection scheme is verified through a theoretical analysis, computer simulations and practical experimental results conducted on a dual three-phase test rig prototype with control algorithm implemented in Texas Instrument?s TMS320F2808 DSP.
Comparison of deterministic and stochastic methods for time-dependent Wigner simulations
Energy Technology Data Exchange (ETDEWEB)
Shao, Sihong, E-mail: sihong@math.pku.edu.cn [LMAM and School of Mathematical Sciences, Peking University, Beijing 100871 (China); Sellier, Jean Michel, E-mail: jeanmichel.sellier@parallel.bas.bg [IICT, Bulgarian Academy of Sciences, Acad. G. Bonchev str. 25A, 1113 Sofia (Bulgaria)
2015-11-01
Recently a Monte Carlo method based on signed particles for time-dependent simulations of the Wigner equation has been proposed. While it has been thoroughly validated against physical benchmarks, no technical study about its numerical accuracy has been performed. To this end, this paper presents the first step towards the construction of firm mathematical foundations for the signed particle Wigner Monte Carlo method. An initial investigation is performed by means of comparisons with a cell average spectral element method, which is a highly accurate deterministic method and utilized to provide reference solutions. Several different numerical tests involving the time-dependent evolution of a quantum wave-packet are performed and discussed in deep details. In particular, this allows us to depict a set of crucial criteria for the signed particle Wigner Monte Carlo method to achieve a satisfactory accuracy.
Entanglement with Negative Wigner Function of Three Thousand Atoms Heralded by One Photon
McConnell, Robert; Hu, Jiazhong; Cuk, Senka; Vuletic, Vladan
2015-01-01
Quantum-mechanically correlated (entangled) states of many particles are of interest in quantum information, quantum computing and quantum metrology. Metrologically useful entangled states of large atomic ensembles have been experimentally realized, but these states display Gaussian spin distribution functions with a non-negative Wigner function. Non-Gaussian entangled states have been produced in small ensembles of ions, and very recently in large atomic ensembles. Here, we generate entanglement in a large atomic ensemble via the interaction with a very weak laser pulse; remarkably, the detection of a single photon prepares several thousand atoms in an entangled state. We reconstruct a negative-valued Wigner function, an important hallmark of nonclassicality, and verify an entanglement depth (minimum number of mutually entangled atoms) of 2910(190) out of 3100 atoms. This is the first time a negative Wigner function or the mutual entanglement of virtually all atoms have been attained in an ensemble containin...
Concurrent growth of two phases in 2D space
Directory of Open Access Journals (Sweden)
A.A. Burbelko
2008-12-01
Full Text Available The kinetics of phase transformations has been studied within the framework of the Kolmogorov-Johnson-Mehl-Avrami (KJMA theory. This theory accurately describes only the parallel growth of anisotropic products with identical convex shape. The identical growth velocity distribution at an interface is the indispensable condition for the above restriction. The proposed earlier extension of KJMA theory (statistical theory of the screened growth enlarges the scope of its application and eliminates the above limitation. The results of the application of this extension were compared with the results obtained during modelling of the concurrent growth of the two types of circular particles on a plane, where the said particles were characterised by different growth rates and modelling was carried out by the method of cellular automata (CA.
Weak equivalence principle in noncommutative phase space and the parameters of noncommutativity
Gnatenko, Kh. P.; Tkachuk, V. M.
2017-08-01
The weak equivalence principle is studied in a space with noncommutativity of coordinates and noncommutativity of momenta. We find conditions on the parameters of noncommutativity which give the possibility to recover the equivalence principle in two-dimensional noncommutative phase space. It is also shown that in the case when these conditions are satisfied the motion of the center-of-mass of a composite system in noncommutative phase space and the relative motion are independent, the kinetic energy of composite system has additivity property and is independent on the systems composition. So, we propose conditions on the parameters of noncommutativity which give the possibility to solve the list of problems in noncommutative phase space.
Meierhenrich, Uwe J.; Cason, Julie R. L.; Szopa, Cyril; Sternberg, Robert; Raulin, François; Thiemann, Wolfram H.-P.; Goesmann, Fred
2013-12-01
The European Space Agency's Rosetta mission was launched in March 2004 in order to reach comet 67P/Churyumov-Gerasimenko by August 2014. The Cometary Sampling and Composition experiment (COSAC) onboard the Rosetta mission's lander "Philae" has been designed for the cometary in situ detection and quantification of organic molecules using gas chromatography coupled to mass spectrometry (GC-MS). The GC unit of COSAC is equipped with eight capillary columns that will each provide a specific stationary phase for molecular separation. Three of these stationary phases will be used to chromatographically resolve enantiomers, as they are composed of liquid polymers of polydimethylsiloxane (PDMS) to which chiral valine or cyclodextrin units are attached. Throughout the ten years of Rosetta's journey through space to reach comet 67P, these liquid stationary phases have been exposed to space vacuum, as the capillary columns within the COSAC unit were not sealed or filled with carrier gas. Long term exposures to space vacuum can cause damage to such liquid stationary phases as key monomers, volatiles, and chiral selectors can be vaporized and lost in transit. We have therefore exposed identical spare units of COSAC's chiral stationary phases over eight years to vacuum conditions mimicking those experienced in space and we have now investigated their resolution capabilities towards different enantiomers both before and after exposure to space vacuum environments. We have observed that enantiomeric resolution capabilities of these chiral liquid enantioselective stationary phases has not been affected by exposure to space vacuum conditions. Thus we conclude that the three chiral stationary phases of the COSAC experiment onboard the Rosetta mission lander "Philae" can be considered to have maintained their resolution capacities throughout their journey prior to cometary landing in November 2014.
Wigner measure and semiclassical limits of nonlinear Schrödinger equations
Zhang, Ping
2008-01-01
This book is based on a course entitled "Wigner measures and semiclassical limits of nonlinear Schrödinger equations," which the author taught at the Courant Institute of Mathematical Sciences at New York University in the spring of 2007. The author's main purpose is to apply the theory of semiclassical pseudodifferential operators to the study of various high-frequency limits of equations from quantum mechanics. In particular, the focus of attention is on Wigner measure and recent progress on how to use it as a tool to study various problems arising from semiclassical limits of Schrödinger-ty
Geometrical comparison of two protein structures using Wigner-D functions
Fathi, S M Saberi
2013-01-01
In this paper, we develop a quantitative comparison method for two arbitrary protein structures. This method uses a root-mean-square deviation (RMSD) characterization and employs a series expansion of the protein's shape function in terms of the Wigner-D functions to define a new criterion, which is called a "similarity value". We further demonstrate that the expansion coefficients for the shape function obtained with the help of the Wigner-D functions correspond to structure factors. Our method addresses the common problem of comparing two proteins with different numbers of atoms. We illustrate it with a worked example.
Stochastic dynamics of large-scale inflation in de Sitter space
Buryak, O. E.
1996-02-01
In this paper we derive exact quantum Langevin equations for stochastic dynamics of large-scale inflation in de Sitter space. These quantum Langevin equations are the equivalent of the Wigner equation and are described by a system of stochastic differential equations. We present a formula for the calculation of the expectation value of a quantum operator whose Weyl symbol is a function of the large-scale inflation scalar field and its time derivative. The quantum expectation value is calculated as a mathematical expectation value over a stochastic process in an extended phase space, where the additional coordinate plays the role of a stochastic phase. The unique solution is obtained for the Cauchy problem for the Wigner equation for large-scale inflation. The stationary solution for the Wigner equation is found for an arbitrary potential. It is shown that the large-scale inflation scalar field in de Sitter space behaves as a quantum one-dimensional dissipative system, which supports the earlier results of Graziani and of Nakao, Nambu, and Sasaki. But the analogy with a one-dimensional model of the quantum linearly damped anharmonic oscillator is not complete: the difference arises from the new time-dependent commutation relation for the large-scale field and its time derivative. It is found that, for the large-scale inflation scalar field, the large time asymptotics is equal to the ``classical limit.'' For the large time limit the quantum Langevin equations are just the classical stochastic Langevin equations (only the stationary state is defined by the quantum field theory).
Phase and Pupil Amplitude Recovery for JWST Space-Optics Control
Dean, B. H.; Zielinski, T. P.; Smith, J. S.; Bolcar, M. R.; Aronstein, D. L.; Fienup, J. R.
2010-01-01
This slide presentation reviews the phase and pupil amplitude recovery for the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam). It includes views of the Integrated Science Instrument Module (ISIM), the NIRCam, examples of Phase Retrieval Data, Ghost Irradiance, Pupil Amplitude Estimation, Amplitude Retrieval, Initial Plate Scale Estimation using the Modulation Transfer Function (MTF), Pupil Amplitude Estimation vs lambda, Pupil Amplitude Estimation vs. number of Images, Pupil Amplitude Estimation vs Rotation (clocking), and Typical Phase Retrieval Results Also included is information about the phase retrieval approach, Non-Linear Optimization (NLO) Optimized Diversity Functions, and Least Square Error vs. Starting Pupil Amplitude.
Phase Space Exploration of Acetylene at Energies up to 13,000 Cm-1
Perry, David S.; Martens, Jonathan; Herman, Michel; Amyay, Badr
2011-06-01
The rotation-vibration Hamiltonian of acetylene is known in detail up to 13,000 Cm-1 in the electronic ground state, allows the calculation of time-dependent dynamics for postulated excitations of certain bright states. Three different measures of phase space exploration are examined including the participation number, Gruebele's dispersion, and the Shannon entropy. The time scales for phase space exploration span the range from 20 fs to 10 ps. The volume of phase space explored by the dynamics increases with energy and the rotational quantum number, J reaching about 90% of the (GOE) statistical limit at 12,000 Cm-1 and J = 100. At low and intermediate J, the extent of phase space exploration is reduced for the local bender and counter-rotator bright states as compared to their normal mode counterparts. However, the phase space exploration of the local mode CH stretch state is similar to that of the corresponding normal mode vibration. These calculations shed light on the applicability of the energy randomization assumption that is at the heart of the Rice-Rampsberger-Kassel-Marcus (RRKM) theory of unimolecular reactions.
Extremal rotating black holes in the near-horizon limit: Phase space and symmetry algebra
Directory of Open Access Journals (Sweden)
G. Compère
2015-10-01
Full Text Available We construct the NHEG phase space, the classical phase space of Near-Horizon Extremal Geometries with fixed angular momenta and entropy, and with the largest symmetry algebra. We focus on vacuum solutions to d dimensional Einstein gravity. Each element in the phase space is a geometry with SL(2,R×U(1d−3 isometries which has vanishing SL(2,R and constant U(1 charges. We construct an on-shell vanishing symplectic structure, which leads to an infinite set of symplectic symmetries. In four spacetime dimensions, the phase space is unique and the symmetry algebra consists of the familiar Virasoro algebra, while in d>4 dimensions the symmetry algebra, the NHEG algebra, contains infinitely many Virasoro subalgebras. The nontrivial central term of the algebra is proportional to the black hole entropy. The conserved charges are given by the Fourier decomposition of a Liouville-type stress-tensor which depends upon a single periodic function of d−3 angular variables associated with the U(1 isometries. This phase space and in particular its symmetries can serve as a basis for a semiclassical description of extremal rotating black hole microstates.
Salecker-Wigner-Peres clock, Feynman paths, and a tunneling time that should not exist
Sokolovski, D.
2017-08-01
The Salecker-Wigner-Peres (SWP) clock is often used to determine the duration a quantum particle is supposed to spend in a specified region of space Ω . By construction, the result is a real positive number, and the method seems to avoid the difficulty of introducing complex time parameters, which arises in the Feynman paths approach. However, it tells little about the particle's motion. We investigate this matter further, and show that the SWP clock, like any other Larmor clock, correlates the rotation of its angular momentum with the durations τ , which the Feynman paths spend in Ω , thereby destroying interference between different durations. An inaccurate weakly coupled clock leaves the interference almost intact, and the need to resolve the resulting "which way?" problem is one of the main difficulties at the center of the "tunnelling time" controversy. In the absence of a probability distribution for the values of τ , the SWP results are expressed in terms of moduli of the "complex times," given by the weighted sums of the corresponding probability amplitudes. It is shown that overinterpretation of these results, by treating the SWP times as physical time intervals, leads to paradoxes and should be avoided. We also analyze various settings of the SWP clock, different calibration procedures, and the relation between the SWP results and the quantum dwell time. The cases of stationary tunneling and tunnel ionization are considered in some detail. Although our detailed analysis addresses only one particular definition of the duration of a tunneling process, it also points towards the impossibility of uniting various time parameters, which may occur in quantum theory, within the concept of a single tunnelling time.
Electron beam phase-space measurement using a high-precision tomography technique
Directory of Open Access Journals (Sweden)
V. Yakimenko
2003-12-01
Full Text Available We report a measurement of the multidimensional phase-space density distribution of an electron bunch. The measurement combines the techniques of picosecond slice-emittance measurement and high-resolution tomographic measurement of transverse phase space. This technique should have a significant impact on the development of low emittance beams and their many applications, such as short-wavelength free-electron lasers and laser accelerators. A diagnostic that provides detailed information on the density distribution of the electron bunch in multidimensional phase space is an essential tool for obtaining a small emittance at a reasonable charge and for understanding the physics of emittance growth. We previously reported a measurement of the slice emittance of a picosecond electron beam [J. S. Fraser, R. L. Sheffield, and E. R. Gray, Nucl. Instrum. Methods Phys. Res., Sect. A 250, 71 (1986.]. The tomographic reconstruction of the phase space was suggested [X. Qiu, K. Batchelor, I. Ben-Zvi, and X. J. Wang, Phys. Rev. Lett. 76, 3723 (1996.] and implemented [C. B. McKee, P. G. O’Shea, and J. M. J. Madey, Nucl. Instrum. Methods Phys. Res., Sect. A 358, 264 (1995; I. Ben-Zvi, J. X. Qiu, and X. J. Wang, in Proceedings of the Particle Accelerator Conference, Vancouver, 1997 (IEEE, Piscataway, NJ, 1997.] using a single quadrupole scan. In the present work we expand the tomographic reconstruction work and combine it with the slice-emittance method. Our present tomographic work pays special attention to the accuracy of the phase-space reconstruction. We use a transport line with nine focusing magnets, and present an analysis and technique aimed at the control of the optical functions and phases. This high-precision phase-space tomography together with the ability to modify the radial charge distribution of the electron beam presents an opportunity to improve the emittance and apply nonlinear radial emittance corrections. Combining the
Amateur Radio on the International Space Station - Phase 2 Hardware System
Bauer, F.; McFadin, L.; Bruninga, B.; Watarikawa, H.
2003-01-01
The International Space Station (ISS) ham radio system has been on-orbit for over 3 years. Since its first use in November 2000, the first seven expedition crews and three Soyuz taxi crews have utilized the amateur radio station in the Functional Cargo Block (also referred to as the FGB or Zarya module) to talk to thousands of students in schools, to their families on Earth, and to amateur radio operators around the world. Early on, the Amateur Radio on the International Space Station (ARISS) international team devised a multi-phased hardware development approach for the ISS ham radio station. Three internal development Phases. Initial Phase 1, Mobile Radio Phase 2 and Permanently Mounted Phase 3 plus an externally mounted system, were proposed and agreed to by the ARISS team. The Phase 1 system hardware development which was started in 1996 has since been delivered to ISS. It is currently operational on 2 meters. The 70 cm system is expected to be installed and operated later this year. Since 2001, the ARISS international team have worked to bring the second generation ham system, called Phase 2, to flight qualification status. At this time, major portions of the Phase 2 hardware system have been delivered to ISS and will soon be installed and checked out. This paper intends to provide an overview of the Phase 1 system for background and then describe the capabilities of the Phase 2 radio system. It will also describe the current plans to finalize the Phase 1 and Phase 2 testing in Russia and outlines the plans to bring the Phase 2 hardware system to full operation.
Tomographic reconstruction of transverse phase space from turn-by-turn profile data
Hancock, S; Lindroos, M
1999-01-01
Tomographic methods have the potential for useful application in beam diagnostics. The tomographic reconstruction of transverse phase space density from turn-by-turn profile data has been studied with particular attention to the effects of dispersion and chromaticity. It is shown that the modified Algebraic Reconstruction Technique (ART) that deals successfully with the problem of non-linear motion in the longitudinal plane cannot, in general, be extended to cover the transverse case. Instead, an approach is proposed in which the effect of dispersion is deconvoluted from the measured profiles before the phase space picture is reconstructed using either the modified ART algorithm or the inverse Radon Transform. This requires an accurate knowledge of the momentum distribution of the beam and the modified ART reconstruction of longitudinal phase space density yields just such information. The method has been tested extensively with simulated data.
Miksovsky, J.; Raidl, A.
Time delays phase space reconstruction represents one of useful tools of nonlinear time series analysis, enabling number of applications. Its utilization requires the value of time delay to be known, as well as the value of embedding dimension. There are sev- eral methods how to estimate both these parameters. Typically, time delay is computed first, followed by embedding dimension. Our presented approach is slightly different - we reconstructed phase space for various combinations of mentioned parameters and used it for prediction by means of the nearest neighbours in the phase space. Then some measure of prediction's success was computed (correlation or RMSE, e.g.). The position of its global maximum (minimum) should indicate the suitable combination of time delay and embedding dimension. Several meteorological (particularly clima- tological) time series were used for the computations. We have also created a MS- Windows based program in order to implement this approach - its basic features will be presented as well.
3D imaging in volumetric scattering media using phase-space measurements.
Liu, Hsiou-Yuan; Jonas, Eric; Tian, Lei; Zhong, Jingshan; Recht, Benjamin; Waller, Laura
2015-06-01
We demonstrate the use of phase-space imaging for 3D localization of multiple point sources inside scattering material. The effect of scattering is to spread angular (spatial frequency) information, which can be measured by phase space imaging. We derive a multi-slice forward model for homogenous volumetric scattering, then develop a reconstruction algorithm that exploits sparsity in order to further constrain the problem. By using 4D measurements for 3D reconstruction, the dimensionality mismatch provides significant robustness to multiple scattering, with either static or dynamic diffusers. Experimentally, our high-resolution 4D phase-space data is collected by a spectrogram setup, with results successfully recovering the 3D positions of multiple LEDs embedded in turbid scattering media.
Phase-space networks of the six-vertex model under different boundary conditions.
Han, Yilong
2010-04-01
The six-vertex model is mapped to three-dimensional sphere stacks and different boundary conditions corresponding to different containers. The shape of the container provides a qualitative visualization of the boundary effect. Based on the sphere-stacking picture, we map the phase spaces of the six-vertex models to discrete networks. A node in the network represents a state of the system, and an edge between two nodes represents a zero-energy spin flip, which corresponds to adding or removing a sphere. The network analysis shows that the phase spaces of systems with different boundary conditions share some common features. We derived a few formulas for the number and the sizes of the disconnected phase-space subnetworks under the periodic boundary conditions. The sphere stacking provides new challenges in combinatorics and may cast light on some two-dimensional models.
Formation and interaction of multiple coherent phase space structures in plasma
Kakad, Amar; Kakad, Bharati; Omura, Yoshiharu
2017-06-01
The head-on collision of multiple counter-propagating coherent phase space structures associated with the ion acoustic solitary waves (IASWs) in plasmas composed of hot electrons and cold ions is studied here by using one-dimensional Particle-in-Cell simulation. The chains of counter-propagating IASWs are generated in the plasma by injecting the Gaussian perturbations in the equilibrium electron and ion densities. The head-on collisions of the counter-propagating electron and ion phase space structures associated with IASWs are allowed by considering the periodic boundary condition in the simulation. Our simulation shows that the phase space structures are less significantly affected by their collision with each other. They emerge out from each other by retaining their characteristics, so that they follow soliton type behavior. We also find that the electrons trapped within these IASW potentials are accelerated, while the ions are decelerated during the course of their collisions.
Phase space analysis for a scalar-tensor model with kinetic and Gauss-Bonnet couplings
Granda, L N
2016-01-01
We study the phase space for an scalar-tensor string inspired model of dark energy with non minimal kinetic and Gauss Bonnet couplings. The form of the scalar potential and of the coupling terms is of the exponential type, which give rise to appealing cosmological solutions. The critical points describe a variety of cosmological scenarios that go from matter or radiation dominated universe to dark energy dominated universe. There were found trajectories in the phase space departing from unstable or saddle fixed points and arriving to the stable scalar field dominated point corresponding to late-time accelerated expansion.
The application of the phase space time evolution method to electron shielding
Cordaro, M. C.; Zucker, M. S.
1972-01-01
A computer technique for treating the motion of charged and neutral particles and called the phase space time evolution method was developed. This technique employs the computer's bookkeeping capacity to keep track of the time development of a phase space distribution of particles. This method was applied to a study of the penetration of electrons. A 1 MeV beam of electrons normally incident on a semi-infinite slab of aluminum was used. Results of the calculation were compared with Monte Carlo calculations and experimental results. Time-dependent PSTE electron penetration results for the same problem are presented.
Testorf, Markus
2006-01-01
Phase-space optics is used to relate the problem of designing diffractive optical elements for any first-order optical system to the corresponding design problem in the Fraunhofer diffraction regime. This, in particular, provides a novel approach for the fractional Fourier transform domain. For fractional Fourier transforms of arbitrary order, the diffractive element is determined as the optimum design computed for a generic Fourier transform system, scaled and modulated with a parabolic lens function. The phase-space description also identifies critical system parameters that limit the performance and applicability of this method. Numerical simulations of paraxial wave propagation are used to validate the method.
Hamiltonian reductions of the one-dimensional Vlasov equation using phase-space moments
Chandre, C.; Perin, M.
2016-03-01
We consider Hamiltonian closures of the Vlasov equation using the phase-space moments of the distribution function. We provide some conditions on the closures imposed by the Jacobi identity. We completely solve some families of examples. As a result, we show that imposing that the resulting reduced system preserves the Hamiltonian character of the parent model shapes its phase space by creating a set of Casimir invariants as a direct consequence of the Jacobi identity. We exhibit three main families of Hamiltonian models with two, three, and four degrees of freedom aiming at modeling the complexity of the bunch of particles in the Vlasov dynamics.
A note on the time decay of solutions for the linearized Wigner-Poisson system
Gamba, Irene
2009-01-01
We consider the one-dimensional Wigner-Poisson system of plasma physics, linearized around a (spatially homogeneous) Lorentzian distribution and prove that the solution of the corresponding linearized problem decays to zero in time. We also give an explicit algebraic decay rate.
Three-Nucleon Bound States and the Wigner-SU(4) Limit
Vanasse, Jared; Phillips, Daniel R.
2017-03-01
We examine the extent to which the properties of three-nucleon bound states are well-reproduced in the limit that nuclear forces satisfy Wigner's SU(4) (spin-isospin) symmetry. To do this we compute the charge radii up to next-to-leading order (NLO) in an effective field theory that is an expansion in powers of R/ a, with R the range of the nuclear force and a the nucleon-nucleon (N N) scattering lengths. In the Wigner-SU(4) limit, the triton and helium-3 point charge radii are equal. At NLO in the range expansion both are 1.66 fm. Adding the first-order corrections due to the breaking of Wigner symmetry in the N N scattering lengths gives a ^3{H} point charge radius of 1.58 fm, which is remarkably close to the experimental number, 1.5978± 0.040 fm (Angeli and Marinova in At Data Nucl Data Tables 99:69-95, 2013). For the ^3{He} point charge radius we find 1.70 fm, about 4% away from the experimental value of 1.77527± 0.0054 fm (Angeli and Marinova 2013). We also examine the Faddeev components that enter the tri-nucleon wave function and find that an expansion of them in powers of the symmetry-breaking parameter converges rapidly. Wigner's SU(4) symmetry is thus a useful starting point for understanding tri-nucleon bound-state properties.
1993-03-01
HIL.BERT SIOHN TRA NSFORM SMOHN TIME SAMPLED A N A L’YTIC DEPENDENT WDF PW SIGNAL SIGNAL CORRELATION FUNCTION D I G ITA L ] FILTER T] Fig. 2...Time-Frequency Representations, Kiuwer Academic Publishers, 1989. 6. Velez , E. and Absher, R., "Transient Analysis of Speech Signals using the Wigner
Optical implementations of the Radon-Wigner display for one-dimensional signals.
Zhang, Y; Gu, B Y; Dong, B Z; Yang, G Z
1998-07-15
New optical implementations of the Radon-Wigner display for a one-dimensional signal are proposed based on the fractional Fourier transform. The setups involve only one varifocal lens. Furthermore, the same magnification can be realized simultaneously for all the fractional transform orders, which is quite convenient for practical applications.
The Wigner method applied to the photodissociation of CH3I
DEFF Research Database (Denmark)
Henriksen, Niels Engholm
1985-01-01
The Wigner method is applied to the Shapiro-Bersohn model of the photodissociation of CH3I. The partial cross sections obtained by this semiclassical method are in very good agreement with results of exact quantum calculations. It is also shown that a harmonic approximation to the vibrational...
Eugene Wigner – A Gedanken Pioneer of the Second Quantum Revolution
Directory of Open Access Journals (Sweden)
Zeilinger Anton
2014-01-01
Full Text Available Eugene Wigner pointed out very interesting consequences of quantum physics in elegant gedanken experiments. As a result of technical progress, these gedanken experiments have become real experiments and contribute to the development of novel concepts in quantum information science, often called the second quantum revolution.
O'Donnell, Kane; Visser, Matt
2011-01-01
The purpose of this paper is to provide an elementary introduction to the qualitative and quantitative results of velocity combination in special relativity, including the Wigner rotation and Thomas precession. We utilize only the most familiar tools of special relativity, in arguments presented at three differing levels: (1) utterly elementary,…
Phase space interrogation of the empirical response modes for seismically excited structures
Paul, Bibhas; George, Riya C.; Mishra, Sudib K.
2017-07-01
Conventional Phase Space Interrogation (PSI) for structural damage assessment relies on exciting the structure with low dimensional chaotic waveform, thereby, significantly limiting their applicability to large structures. The PSI technique is presently extended for structure subjected to seismic excitations. The high dimensionality of the phase space for seismic response(s) are overcome by the Empirical Mode Decomposition (EMD), decomposing the responses to a number of intrinsic low dimensional oscillatory modes, referred as Intrinsic Mode Functions (IMFs). Along with their low dimensionality, a few IMFs, retain sufficient information of the system dynamics to reflect the damage induced changes. The mutually conflicting nature of low-dimensionality and the sufficiency of dynamic information are taken care by the optimal choice of the IMF(s), which is shown to be the third/fourth IMFs. The optimal IMF(s) are employed for the reconstruction of the Phase space attractor following Taken's embedding theorem. The widely referred Changes in Phase Space Topology (CPST) feature is then employed on these Phase portrait(s) to derive the damage sensitive feature, referred as the CPST of the IMFs (CPST-IMF). The legitimacy of the CPST-IMF is established as a damage sensitive feature by assessing its variation with a number of damage scenarios benchmarked in the IASC-ASCE building. The damage localization capability, remarkable tolerance to noise contamination and the robustness under different seismic excitations of the feature are demonstrated.
Phased array ultrasonic examination of space shuttle main engine nozzle weld
James, S.; Engel, J.; Kimbrough, D.; Suits, M.
2002-05-01
This paper describes a Phased Array Ultrasonic Examination that was developed for the examination of a limited access circumferential Inconel 718 fusion weld of a Space Shuttle Main Engine Nozzle-Cone. The paper discusses the selection and formation criteria used for the phased array focal laws, the reference standard that simulated hardware conditions, the examination concept, and results. Several unique constraints present during this examination included limited probe movement to a single axis and one-sided access to the weld.
Kinetics for Reduction of Iron Ore Based on the Phase Space Reconstruction
Guo-Feng Fan; Li-Ling Peng; Wei-Chiang Hong; Fan Sun
2014-01-01
A series of smelting reduction experiments has been carried out with high-phosphorus iron ore of the different bases and heating rates by thermogravimetric analyzer. The derivative thermo gravimetric (DTG) data have been obtained from the experiments. After analyzing its phase space reconstruction, it is found that DTG phase portrait contains with a clear double “ $\\infty $ ” attractor characteristic by one-order delay. The statistical properties of the attractor inside and outside the double...
Evidence of Wigner rotation phenomena in the beam splitting experiment at the LCLS
Energy Technology Data Exchange (ETDEWEB)
Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2016-07-15
A result from particle tracking states that, after a microbunched electron beam is kicked, its trajectory changes while the orientation of the microbunching wavefront remains as before. Experiments at the LCLS showed that radiation in the kicked direction is produced practically without suppression. This could be explained if the orientation of the microbunching wavefront is readjusted along the kicked direction. In previous papers we showed that when the evolution of the electron beam modulation is treated according to relativistic kinematics, the orientation of the microbunching wavefront in the ultrarelativistic asymptotic is always perpendicular to the electron beam velocity. There we refrained from using advanced theoretical concepts to explain or analyze the wavefront rotation. For example, we only hinted to the relation of this phenomenon with the concept of Wigner rotation. This more abstract view of wavefront rotation underlines its elementary nature. The Wigner rotation is known as a fundamental effect in elementary particle physics. The composition of non collinear boosts does not result in a simple boost but, rather, in a Lorentz transformation involving a boost and a rotation, the Wigner rotation. Here we show that during the LCLS experiments, a Wigner rotation was actually directly recorded for the first time with a ultrarelativistic, macroscopic object: an ultrarelativistic electron bunch in an XFEL modulated at nm-scale of the size of about 10 microns. Here we point out the role of Wigner rotation in the analysis and interpretation of experiments with ultrarelativistic, microbunched electron beams in FELs. After the beam splitting experiment at the LCLS it became clear that, in the ultrarelativistic asymptotic, the projection of the microbunching wave vector onto the beam velocity is a Lorentz invariant, similar to the helicity in particle physics.
Simulations of minor mergers - II. The phase-space structure of thick discs
Villalobos, Alvaro; Helmi, Amina
2009-01-01
We analyse the phase-space structure of simulated thick discs that are the result of a 5:1 mass-ratio merger between a disc galaxy and a satellite. Our main goal is to establish what would be the imprints of a merger origin for the Galactic thick disc. We find that the spatial distribution predicted
Phase-space diffusion in turbulent plasmas: The random acceleration problem revisited
DEFF Research Database (Denmark)
Pécseli, H.L.; Trulsen, J.
1991-01-01
Phase-space diffusion of test particles in turbulent plasmas is studied by an approach based on a conditional statistical analysis of fluctuating electrostatic fields. Analytical relations between relevant conditional averages and higher-order correlations,
On coherent-state representations of quantum mechanics: Wave mechanics in phase space
DEFF Research Database (Denmark)
Møller, Klaus Braagaard; Jørgensen, Thomas Godsk; Torres-Vega, Gabino
1997-01-01
In this article we argue that the state-vector phase-space representation recently proposed by Torres-Vega and co-workers [introduced in J. Chem. Phys. 98, 3103 (1993)] coincides with the totality of coherent-state representations for the Heisenberg-Weyl group. This fact leads to ambiguities when...
NOTE: A technique for generating phase-space-based Monte Carlo beamlets in radiotherapy applications
Bush, K.; Popescu, I. A.; Zavgorodni, S.
2008-09-01
As radiotherapy treatment planning moves toward Monte Carlo (MC) based dose calculation methods, the MC beamlet is becoming an increasingly common optimization entity. At present, methods used to produce MC beamlets have utilized a particle source model (PSM) approach. In this work we outline the implementation of a phase-space-based approach to MC beamlet generation that is expected to provide greater accuracy in beamlet dose distributions. In this approach a standard BEAMnrc phase space is sorted and divided into beamlets with particles labeled using the inheritable particle history variable. This is achieved with the use of an efficient sorting algorithm, capable of sorting a phase space of any size into the required number of beamlets in only two passes. Sorting a phase space of five million particles can be achieved in less than 8 s on a single-core 2.2 GHz CPU. The beamlets can then be transported separately into a patient CT dataset, producing separate dose distributions (doselets). Methods for doselet normalization and conversion of dose to absolute units of Gy for use in intensity modulated radiation therapy (IMRT) plan optimization are also described.
Numerical method for estimating the size of chaotic regions of phase space
Energy Technology Data Exchange (ETDEWEB)
Henyey, F.S.; Pomphrey, N.
1987-10-01
A numerical method for estimating irregular volumes of phase space is derived. The estimate weights the irregular area on a surface of section with the average return time to the section. We illustrate the method by application to the stadium and oval billiard systems and also apply the method to the continuous Henon-Heiles system. 15 refs., 10 figs. (LSP)
Endeve, Eirik; Hauck, Cory D.; Xing, Yulong; Mezzacappa, Anthony
2015-04-01
We extend the positivity-preserving method of Zhang and Shu [49] to simulate the advection of neutral particles in phase space using curvilinear coordinates. The ability to utilize these coordinates is important for non-equilibrium transport problems in general relativity and also in science and engineering applications with specific geometries. The method achieves high-order accuracy using Discontinuous Galerkin (DG) discretization of phase space and strong stability-preserving, Runge-Kutta (SSP-RK) time integration. Special care is taken to ensure that the method preserves strict bounds for the phase space distribution function f; i.e., f ∈ [ 0 , 1 ]. The combination of suitable CFL conditions and the use of the high-order limiter proposed in [49] is sufficient to ensure positivity of the distribution function. However, to ensure that the distribution function satisfies the upper bound, the discretization must, in addition, preserve the divergence-free property of the phase space flow. Proofs that highlight the necessary conditions are presented for general curvilinear coordinates, and the details of these conditions are worked out for some commonly used coordinate systems (i.e., spherical polar spatial coordinates in spherical symmetry and cylindrical spatial coordinates in axial symmetry, both with spherical momentum coordinates). Results from numerical experiments - including one example in spherical symmetry adopting the Schwarzschild metric - demonstrate that the method achieves high-order accuracy and that the distribution function satisfies the maximum principle.
Energy Technology Data Exchange (ETDEWEB)
Mezzacappa, Anthony [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Endeve, Eirik [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hauck, Cory D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Xing, Yulong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2015-02-01
We extend the positivity-preserving method of Zhang & Shu [49] to simulate the advection of neutral particles in phase space using curvilinear coordinates. The ability to utilize these coordinates is important for non-equilibrium transport problems in general relativity and also in science and engineering applications with specific geometries. The method achieves high-order accuracy using Discontinuous Galerkin (DG) discretization of phase space and strong stabilitypreserving, Runge-Kutta (SSP-RK) time integration. Special care in taken to ensure that the method preserves strict bounds for the phase space distribution function f; i.e., f ϵ [0, 1]. The combination of suitable CFL conditions and the use of the high-order limiter proposed in [49] is su cient to ensure positivity of the distribution function. However, to ensure that the distribution function satisfies the upper bound, the discretization must, in addition, preserve the divergencefree property of the phase space ow. Proofs that highlight the necessary conditions are presented for general curvilinear coordinates, and the details of these conditions are worked out for some commonly used coordinate systems (i.e., spherical polar spatial coordinates in spherical symmetry and cylindrical spatial coordinates in axial symmetry, both with spherical momentum coordinates). Results from numerical experiments - including one example in spherical symmetry adopting the Schwarzschild metric - demonstrate that the method achieves high-order accuracy and that the distribution function satisfies the maximum principle.
de Silva, Chamelle R.; Chigona, A.; Adendorff, S. A.
2016-01-01
Among its many affordances, the interactive whiteboard (IWB) as a digital space for children's dialogic engagement in the Foundation Phase classroom remains largely under-exploited. This paper emanates from a study which was undertaken in an attempt to understand how teachers acquire knowledge of emerging technologies and how this shapes their…
A High-Resolution Multi-Slit Phase Space Measurement Technique for Low-Emittance Beams
Energy Technology Data Exchange (ETDEWEB)
Thangaraj, J. C.T. [Fermilab; Piot, P. [Northern Illinois U.
2012-07-25
Precise measurement of transverse phase space of a high-brightness electron beamis of fundamental importance in modern accelerators and free-electron lasers. Often, the transverse phase space of a high-brightness, space-charge-dominated electron beam is measured using a multi-slit method. In this method, a transverse mask (slit/pepperpot) samples the beaminto a set of beamlets, which are then analyzed on to a screen downstream. The resolution in this method is limited by the type of screen used which is typically around 20 mum for a high-sensitivity Yttrium Aluminum Garnet screen. Accurate measurement of sub-micron transverse emittance using this method would require a long drift space between the multi-slit mask and observation screen. In this paper, we explore a variation of the technique that incorporates quadrupole magnets between the multi-slit mask and the screen. It is shown that this arrangement can improve the resolution of the transverse-phase-space measurement with in a short footprint.
Phase space simulation of collisionless stellar systems on the massively parallel processor
White, Richard L.
1987-01-01
A numerical technique for solving the collisionless Boltzmann equation describing the time evolution of a self gravitating fluid in phase space was implemented on the Massively Parallel Processor (MPP). The code performs calculations for a two dimensional phase space grid (with one space and one velocity dimension). Some results from calculations are presented. The execution speed of the code is comparable to the speed of a single processor of a Cray-XMP. Advantages and disadvantages of the MPP architecture for this type of problem are discussed. The nearest neighbor connectivity of the MPP array does not pose a significant obstacle. Future MPP-like machines should have much more local memory and easier access to staging memory and disks in order to be effective for this type of problem.
Extending the possibilities in phase space analysis of synchrotron radiation x-ray optics.
Ferrero, Claudio; Smilgies, Detlef-Matthias; Riekel, Christian; Gatta, Gilles; Daly, Peter
2008-08-01
A simple analytical approach to phase space analysis of the performance of x-ray optical setups (beamlines) combining several elements in position-angle-wavelength space is presented. The mathematical description of a large class of optical elements commonly used on synchrotron beamlines has been reviewed and extended with respect to the existing literature and is reported in a revised form. Novel features are introduced, in particular, the possibility to account for imperfections on mirror surfaces and to incorporate nanofocusing devices like refractive lenses in advanced beamline setups using the same analytical framework. Phase space analysis results of the simulation of an undulator beamline with focusing optics at the European Synchrotron Radiation Facility compare favorably with results obtained by geometric ray-tracing methods and, more importantly, with experimental measurements. This approach has been implemented into a simple and easy-to-use program toolkit for optical calculations based on the Mathematica software package.
Simulated response of top-hat electrostatic analysers - importance of phase-space resolution
De Marco, Rossana; Bruno, Roberto; D'Amicis, Raffaella; Federica Marcucci, Maria; Servidio, Sergio; Valentini, Francesco
2016-04-01
We use a numerical code able to reproduce the angular/energy response of a typical electrostatic analyzer of top-hat type starting from velocity distribution functions (VDFs) generated by numerical imulations.The simulations are based on the Hybrid Vlasov-Maxwell (HVM) numerical algorithm which integrates the Vlasov equation for the ion distribution function in multi-dimensional geometry in phase space, while the electrons are treated as a fluid. Virtual satellites launched through the simulation box measure the particle VDFs. Such VDFs are interpolated into a spacecraft reference frame and moved from the simulation Cartesian grid to energy-angular coordinates to mimic the response of a real electrostatic sensor in the solar wind and in the magnetosheath for different conditions. We discuss the results of this study with respect to the importance of phase-space resolution for a space plasma experiment meant to investigate kinetic plasma regime.
Ahn, Junyeong; Yang, Bohm-Jung
2017-04-14
We study a topological phase transition between a normal insulator and a quantum spin Hall insulator in two-dimensional (2D) systems with time-reversal and twofold rotation symmetries. Contrary to the case of ordinary time-reversal invariant systems, where a direct transition between two insulators is generally predicted, we find that the topological phase transition in systems with an additional twofold rotation symmetry is mediated by an emergent stable 2D Weyl semimetal phase between two insulators. Here the central role is played by the so-called space-time inversion symmetry, the combination of time-reversal and twofold rotation symmetries, which guarantees the quantization of the Berry phase around a 2D Weyl point even in the presence of strong spin-orbit coupling. Pair creation and pair annihilation of Weyl points accompanying partner exchange between different pairs induces a jump of a 2D Z_{2} topological invariant leading to a topological phase transition. According to our theory, the topological phase transition in HgTe/CdTe quantum well structure is mediated by a stable 2D Weyl semimetal phase because the quantum well, lacking inversion symmetry intrinsically, has twofold rotation about the growth direction. Namely, the HgTe/CdTe quantum well can show 2D Weyl semimetallic behavior within a small but finite interval in the thickness of HgTe layers between a normal insulator and a quantum spin Hall insulator. We also propose that few-layer black phosphorus under perpendicular electric field is another candidate system to observe the unconventional topological phase transition mechanism accompanied by the emerging 2D Weyl semimetal phase protected by space-time inversion symmetry.
Phase-space structures - I. A comparison of 6D density estimators
Maciejewski, M.; Colombi, S.; Alard, C.; Bouchet, F.; Pichon, C.
2009-03-01
In the framework of particle-based Vlasov systems, this paper reviews and analyses different methods recently proposed in the literature to identify neighbours in 6D space and estimate the corresponding phase-space density. Specifically, it compares smoothed particle hydrodynamics (SPH) methods based on tree partitioning to 6D Delaunay tessellation. This comparison is carried out on statistical and dynamical realizations of single halo profiles, paying particular attention to the unknown scaling, SG, used to relate the spatial dimensions to the velocity dimensions. It is found that, in practice, the methods with local adaptive metric provide the best phase-space estimators. They make use of a Shannon entropy criterion combined with a binary tree partitioning and with subsequent SPH interpolation using 10-40 nearest neighbours. We note that the local scaling SG implemented by such methods, which enforces local isotropy of the distribution function, can vary by about one order of magnitude in different regions within the system. It presents a bimodal distribution, in which one component is dominated by the main part of the halo and the other one is dominated by the substructures of the halo. While potentially better than SPH techniques, since it yields an optimal estimate of the local softening volume (and therefore the local number of neighbours required to perform the interpolation), the Delaunay tessellation in fact generally poorly estimates the phase-space distribution function. Indeed, it requires, prior to its implementation, the choice of a global scaling SG. We propose two simple but efficient methods to estimate SG that yield a good global compromise. However, the Delaunay interpolation still remains quite sensitive to local anisotropies in the distribution. To emphasize the advantages of 6D analysis versus traditional 3D analysis, we also compare realistic 6D phase-space density estimation with the proxy proposed earlier in the literature, Q = ρ/σ3
Stumpf, H.
2003-01-01
Generalized de Broglie-Bargmann-Wigner (BBW) equations are relativistically invariant quantum mechanical many body equations with nontrivial interaction, selfregularization and probability interpretation. Owing to these properties these equations are a suitable means for describing relativistic bound states of fermions. In accordance with de Broglie's fusion theory and modern assumptions about the partonic substructure of elementary fermions, i.e., leptons and quarks, the three-body generalized BBW-equations are investigated. The transformation properties and quantum numbers of the three-parton equations under the relevant group actions are elaborated in detail. Section 3 deals with the action of the isospin group SU(2), a U(1) global gauge group for the fermion number, the hypercharge and charge generators. The resulting quantum numbers of the composite partonic systems can be adapted to those of the phenomenological particles to be described. The space-time transformations and in particular rotations generated by angular momentum operators are considered in Section 4. Based on the compatibility of the BBW-equations and the group theoretical constraints, in Sect. 5 integral equations are formulated in a representation with diagonal energy and total angular momentum variables. The paper provides new insight into the solution space and quantum labels of resulting integral equations for three parton states and prepares the ground for representing leptons and quarks as composite systems.
Quantum effects in nanosystems: Good reasons to use phase-space Weyl symbols
Vaia, Ruggero
2016-12-01
Bogoliubov transformations have been successfully applied in several condensed-matter contexts, e.g., in the theory of superconductors, superfluids, and antiferromagnets. These applications are based on bulk models where translation symmetry can be assumed, so that few degrees of freedom in Fourier space can be "diagonalized" separately, and in this way it is easy to find the approximate ground state and its excitations. As translation symmetry cannot be invoked when it comes to nanoscopic systems, the corresponding multidimensional Bogoliubov transformations are more complicated. For bosonic systems it is much simpler to proceed using phase-space variables, i.e., coordinates and momenta. Interactions can be accounted for by the self-consistent harmonic approximation, which is naturally developed using phase-space Weyl symbols. The spin-flop transition in a short antiferromagnetic chain is illustrated as an example. This approach, rarely used in the past, is expected to be generally useful to estimate quantum effects, e.g., on phase diagrams of ordered vs disordered phases.
Penco, G; Danailov, M; Demidovich, A; Allaria, E; De Ninno, G; Di Mitri, S; Fawley, W M; Ferrari, E; Giannessi, L; Trovó, M
2014-01-31
Control of the electron-beam longitudinal-phase-space distribution is of crucial importance in a number of accelerator applications, such as linac-driven free-electron lasers, colliders and energy recovery linacs. Some longitudinal-phase-space features produced by nonlinear electron beam self- fields, such as a quadratic energy chirp introduced by geometric longitudinal wakefields in radio-frequency (rf) accelerator structures, cannot be compensated by ordinary tuning of the linac rf phases nor corrected by a single high harmonic accelerating cavity. In this Letter we report an experimental demonstration of the removal of the quadratic energy chirp by properly shaping the electron beam current at the photoinjector. Specifically, a longitudinal ramp in the current distribution at the cathode linearizes the longitudinal wakefields in the downstream linac, resulting in a flat electron current and energy distribution. We present longitudinal-phase-space measurements in this novel configuration compared to those typically obtained without longitudinal current shaping at the FERMI linac.
Maple procedures for the coupling of angular momenta. IX. Wigner D-functions and rotation matrices
Pagaran, J.; Fritzsche, S.; Gaigalas, G.
2006-04-01
The Wigner D-functions, Dpqj(α,β,γ), are known for their frequent use in quantum mechanics. Defined as the matrix elements of the rotation operator Rˆ(α,β,γ) in R and parametrized in terms of the three Euler angles α, β, and γ, these functions arise not only in the transformation of tensor components under the rotation of the coordinates, but also as the eigenfunctions of the spherical top. In practice, however, the use of the Wigner D-functions is not always that simple, in particular, if expressions in terms of these and other functions from the theory of angular momentum need to be simplified before some computations can be carried out in detail. To facilitate the manipulation of such Racah expressions, here we present an extension to the RACAH program [S. Fritzsche, Comput. Phys. Comm. 103 (1997) 51] in which the properties and the algebraic rules of the Wigner D-functions and reduced rotation matrices are implemented. Care has been taken to combine the standard knowledge about the rotation matrices with the previously implemented rules for the Clebsch-Gordan coefficients, Wigner n-j symbols, and the spherical harmonics. Moreover, the application of the program has been illustrated below by means of three examples. Program summaryTitle of program:RACAH Catalogue identifier:ADFv_9_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADFv_9_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Catalogue identifier of previous version: ADFW, ADHW, title RACAH Journal reference of previous version(s): S. Fritzsche, Comput. Phys. Comm. 103 (1997) 51; S. Fritzsche, S. Varga, D. Geschke, B. Fricke, Comput. Phys. Comm. 111 (1998) 167; S. Fritzsche, T. Inghoff, M. Tomaselli, Comput. Phys. Comm. 153 (2003) 424. Does the new version supersede the previous one: Yes, in addition to the spherical harmonics and recoupling coefficients, the program now supports also the occurrence of the Wigner rotation matrices in the algebraic
Energy Technology Data Exchange (ETDEWEB)
Casado, A [Departamento de Fisica Aplicada III, Escuela Superior de Ingenieros, Universidad de Sevilla, 41092 Sevilla (Spain); Guerra, S [Centro Asociado de la Universidad Nacional de Educacion a Distancia de Las Palmas de Gran Canaria (Spain); Placido, J [Departamento de Fisica, Universidad de Las Palmas de Gran Canaria (Spain)], E-mail: acasado@us.es
2008-02-28
In this paper, the theory of parametric down-conversion in the Wigner representation is applied to Ekert's quantum cryptography protocol. We analyse the relation between two-photon entanglement and (non-secure) quantum key distribution within the Wigner framework in the Heisenberg picture. Experiments using two-qubit polarization entanglement generated in nonlinear crystals are analysed in this formalism, along with the effects of eavesdropping attacks in the case of projective measurements.
Phase-space approach to lensless measurements of optical field correlations.
Sharma, Katelynn A; Brown, Thomas G; Alonso, Miguel A
2016-07-11
We analyze and test a general approach for efficiently measuring space-variant partially coherent quasi-monochromatic fields using only amplitude masks and free propagation. A phase-space description is presented to analyze approaches of this type and understand their limitations. Three variants of the method are discussed and compared, the first using an aperture mask, the second employing both an obstacle (the exact inverse of the aperture) and a clear mask, and the last combining the previous two. We discuss the advantages and disadvantages of each option.
James Webb Space Telescope segment phasing using differential optical transfer functions.
Codona, Johanan L; Doble, Nathan
2015-03-01
Differential optical transfer function (dOTF) is an image-based, noniterative wavefront sensing method that uses two star images with a single small change in the pupil. We describe two possible methods for introducing the required pupil modification to the James Webb Space Telescope, one using a small (telescope can be measured simultaneously. Also, since dOTF gives the pupil field amplitude as well as the phase, it could provide a first approximation or constraint to the planned iterative phase retrieval algorithms.
Demonstration of extended capture range for James Webb Space Telescope phase retrieval.
Carlisle, R Elizabeth; Acton, D Scott
2015-07-20
A geometrical phase retrieval (GPR) algorithm is applied to the problem of image stacking in order to extend the capture range of normal phase retrieval (PR) on the James Webb Space Telescope (JWST), and potentially eliminate a lengthy image-stacking process that is based on centroids. Computer simulations are used to establish the capture range of the existing PR algorithm for JWST and demonstrate that it is increased by more than a factor of 10 when combined with GPR, guaranteeing PR capture 95% of the time. An experiment using a scale optical model of JWST was conducted to demonstrate the effectiveness of the GPR algorithm in both coherent and incoherent imaging.
Directory of Open Access Journals (Sweden)
Mawardi Bahri
2017-01-01
Full Text Available The quaternion Wigner-Ville distribution associated with linear canonical transform (QWVD-LCT is a nontrivial generalization of the quaternion Wigner-Ville distribution to the linear canonical transform (LCT domain. In the present paper, we establish a fundamental relationship between the QWVD-LCT and the quaternion Fourier transform (QFT. Based on this fact, we provide alternative proof of the well-known properties of the QWVD-LCT such as inversion formula and Moyal formula. We also discuss in detail the relationship among the QWVD-LCT and other generalized transforms. Finally, based on the basic relation between the quaternion ambiguity function associated with the linear canonical transform (QAF-LCT and the QFT, we present some important properties of the QAF-LCT.
Entanglement and Wigner Function Negativity of Multimode Non-Gaussian States
Walschaers, Mattia; Fabre, Claude; Parigi, Valentina; Treps, Nicolas
2017-11-01
Non-Gaussian operations are essential to exploit the quantum advantages in optical continuous variable quantum information protocols. We focus on mode-selective photon addition and subtraction as experimentally promising processes to create multimode non-Gaussian states. Our approach is based on correlation functions, as is common in quantum statistical mechanics and condensed matter physics, mixed with quantum optics tools. We formulate an analytical expression of the Wigner function after the subtraction or addition of a single photon, for arbitrarily many modes. It is used to demonstrate entanglement properties specific to non-Gaussian states and also leads to a practical and elegant condition for Wigner function negativity. Finally, we analyze the potential of photon addition and subtraction for an experimentally generated multimode Gaussian state.
Entanglement Potential Versus Negativity of Wigner Function for SUP-Operated Quantum States
Chatterjee, Arpita
2017-10-01
We construct a distinct category of nonclassical quantum states by applying a superposition of products (SUP) of field annihilation ( \\hat {a}) and creation ( \\hat {a}^{\\dagger }) operators of the type ( s\\hat {a}\\hat {a}^{\\dagger }+t\\hat {a}^{\\dagger }\\hat {a}), with s2+t2=1, upon thermal and even coherent states. We allow these SUP operated states to undergo a decoherence process and then describe the nonclassical features of the resulted field by using the entanglement potential (EP) and the negativity of the Wigner distribution function. Our analysis reveals that both the measures are reduced in the linear loss process. The partial negativity of the Wigner function disappears when losses exceed 50% but EP exists always.
Migratory resonances and Wigner timers in the photoionization of fullerene class of molecules
Chakraborty, Himadri
2017-04-01
Empty fullerenes and atom-encaging endofullerenes are quintessential symmetric molecules exhibiting near stability in the room temperature. This property endows them with the quality to be tested for spectroscopic information otherwise inaccessible with regular atoms and molecules. Probing the response of fullerenes and endofullerenes to electromagnetic radiations is one classic way to accomplish this. Conventional spectroscopy of determining the photoelectron count and kinetic energy, as the frequency of the incoming photons varies, predicts varieties of resonances for such molecules. These resonances fundamentally originate from either the correlated electronic motions leading to plasmons or from the molecule's structural symmetry inducing diffractions or even from the mixing of both these effects in tandem. A particularly exotic class of these resonances, which will be emphasized in the talk, includes photoexcitation at one site of the molecule but its subsequent decay at a different location, as well as a coherent admixture of this mechanism with localized Auger processes. The other part of the talk will be devoted to connect to a more contemporary form of spectroscopy by evaluating the time-of-flight of the photoelectron, starting from its production at the molecule to the detector. This utilizes a Wigner clock based on the knowledge of energy-dependent photoelectron quantum phase. It will be shown that the information that can be obtained from the knowledge of this time is often consistent with the underlying electron correlative dynamics, both at the energy region of the giant plasmon resonance and at the generic Cooper-type minima (or anti-resonances). A selection of the results will be presented which are computed by the density functional approximation. The ground state of the molecule is described in a local density approximation (LDA) framework with accurate exchange correlation potential. And a linear-response variant of LDA (TDLDA) is utilized to
Response to Comment on "Observation of the Wigner-Huntington transition to metallic hydrogen".
Silvera, Isaac F; Dias, Ranga
2017-08-25
Liu et al present negative comments on our observation of the Wigner-Huntington transition to metallic hydrogen (MH). Earlier attempts to produce MH were unsuccessful due to diamond failure before the required pressures were achieved. We produced the highest static pressures (495 gigapascals) ever on hydrogen at low temperatures. Here, we respond to their objections. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.
Widjaja, Joewono; Dawprateep, Saowaros; Chuamchaitrakool, Porntip
2017-07-01
Extractions of particle positions from inline holograms using a single coefficient of Wigner-Ville distribution (WVD) are experimentally verified. WVD analysis of holograms gives local variation of fringe frequency. Regardless of an axial position of particles, one of the WVD coefficients has the unique characteristics of having the lowest amplitude and being located on a line with a slope inversely proportional to the particle position. Experimental results obtained using two image sensors with different resolutions verify the feasibility of the present method.
Chaos control in delayed phase space constructed by the Takens embedding theory
Hajiloo, R.; Salarieh, H.; Alasty, A.
2018-01-01
In this paper, the problem of chaos control in discrete-time chaotic systems with unknown governing equations and limited measurable states is investigated. Using the time-series of only one measurable state, an algorithm is proposed to stabilize unstable fixed points. The approach consists of three steps: first, using Takens embedding theory, a delayed phase space preserving the topological characteristics of the unknown system is reconstructed. Second, a dynamic model is identified by recursive least squares method to estimate the time-series data in the delayed phase space. Finally, based on the reconstructed model, an appropriate linear delayed feedback controller is obtained for stabilizing unstable fixed points of the system. Controller gains are computed using a systematic approach. The effectiveness of the proposed algorithm is examined by applying it to the generalized hyperchaotic Henon system, prey-predator population map, and the discrete-time Lorenz system.
New Thermodynamical Force in Plasma Phase Space that Controls Turbulence and Turbulent Transport
Itoh, Sanae-I.; Itoh, Kimitaka
2012-11-01
Physics of turbulence and turbulent transport has been developed on the central dogma that spatial gradients constitute the controlling parameters, such as Reynolds number and Rayleigh number. Recent experiments with the nonequilibrium plasmas in magnetic confinement devices, however, have shown that the turbulence and transport change much faster than global parameters, after an abrupt change of heating power. Here we propose a theory of turbulence in inhomogeneous magnetized plasmas, showing that the heating power directly influences the turbulence. New mechanism, that an external source couples with plasma fluctuations in phase space so as to affect turbulence, is investigated. A new thermodynamical force in phase-space, i.e., the derivative of heating power by plasma pressure, plays the role of new control parameter, in addition to spatial gradients. Following the change of turbulence, turbulent transport is modified accordingly. The condition under which this new effect can be observed is also evaluated.
Multiturn extraction and injection by means of adiabatic capture in stable islands of phase space
Cappi, R
2004-01-01
Recently a novel approach has been proposed for performing multiturn extraction from a circular machine. Such a technique consists of splitting the beam by means of stable islands created in transverse phase space by magnetic elements creating nonlinear fields, such as sextupoles and octupoles. Provided a slow time variation of the linear tune is applied, adiabatic with respect to the betatron motion, the islands can be moved in phase space and eventually charged particles may be trapped inside the stable structures. This generates a certain number of well-separated beamlets. Originally, this principle was successfully tested using a fourth-order resonance. In this paper the approach is generalized by considering other types of resonances as well as the possibility of performing multiple multiturn extractions. The results of numerical simulations are presented and described in detail. Of course, by time reversal, the proposed approach could be used also for multiturn injection.
Phase-space approach to solving the time-independent Schrödinger equation.
Shimshovitz, Asaf; Tannor, David J
2012-08-17
We propose a method for solving the time-independent Schrödinger equation based on the von Neumann (vN) lattice of phase space Gaussians. By incorporating periodic boundary conditions into the vN lattice [F. Dimler et al., New J. Phys. 11, 105052 (2009)], we solve a longstanding problem of convergence of the vN method. This opens the door to tailoring quantum calculations to the underlying classical phase space structure while retaining the accuracy of the Fourier grid basis. The method has the potential to provide enormous numerical savings as the dimensionality increases. In the classical limit, the method reaches the remarkable efficiency of one basis function per one eigenstate. We illustrate the method for a challenging two-dimensional potential where the Fourier grid method breaks down.
Pbar Beam Stacking in the Recycler by Longitudinal Phase-space Coating
Energy Technology Data Exchange (ETDEWEB)
Bhat, C. M. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
2013-08-06
Barrier rf buckets have brought about new challenges in longitudinal beam dynamics of charged particle beams in synchrotrons and at the same time led to many new remarkable prospects in beam handling. In this paper, I describe a novel beam stacking scheme for synchrotrons using barrier buckets without any emittance dilution to the beam. First I discuss the general principle of the method, called longitudinal phase-space coating. Multi-particle beam dynamics simulations of the scheme applied to the Recycler, convincingly validates the concepts and feasibility of the method. Then I demonstrate the technique experimentally in the Recycler and also use it in operation. A spin-off of this scheme is its usefulness in mapping the incoherent synchrotron tune spectrum of the beam particles in barrier buckets and producing a clean hollow beam in longitudinal phase space. Both of which are described here in detail with illustrations. The beam stacking scheme presented here is the first of its kind.
Subcritical Growth of Electron Phase-space Holes in Planetary Radiation Belts
Osmane, Adnane; Turner, Drew L.; Wilson, Lynn B.; Dimmock, Andrew P.; Pulkkinen, Tuija I.
2017-09-01
The discovery of long-lived electrostatic coherent structures with large-amplitude electric fields (1≤slant E ≤slant 500 mV/m) by the Van Allen Probes has revealed alternative routes through which planetary radiation belts’ acceleration can take place. Following previous reports showing that small phase-space holes, with qφ /{T}ec≃ {10}-2{--}{10}-3, could result from electron interaction with large-amplitude whistlers, we demonstrate one possible mechanism through which holes can grow nonlinearly (I.e., γ \\propto \\sqrt{φ }) and subcritically as a result of momentum exchange between hot and cold electron populations. Our results provide an explanation for the common occurrence and fast growth of large-amplitude electron phase-space holes in the Earth’s radiation belts.
Recent progress on phase-space turbulence and dynamical response in collisionless plasmas
Lesur, Maxime
2013-01-01
In the presence of wave dissipation, phase-space structures emerge in nonlinear Vlasov dynamics. Their dynamics can lead to a nonlinear continuous shifting of the wave frequency (chirping). This report summarizes my personal contribution to these topics in the fiscal year 2012. The effects of collisions on chirping characteristics were investigated, with a one-dimensional beam-plasma kinetic model. The long-time nonlinear evolution was systematically categorized as damped, steady-state, periodic, chaotic and chirping. The chirping regime was sub-categorized as periodic, chaotic, bursty, and intermittent. Existing analytic theory was extended to account for Krook-like collisions. Relaxation oscillations, associated with chirping bursts, were investigated in the presence of dynamical friction and velocity-diffusion. The period increases with decreasing drag, and weakly increases with decreasing diffusion. A new theory gives a simple relation between the growth of phase-space structures and that of the wave ener...
Halftone information hiding technology based on phase feature of space filling curves
Hu, Jianhua; Cao, Peng; Dong, Zhihong; Cao, Xiaohe
2017-08-01
To solve the problems of the production of interference fringes (namely moiré in printing) and improve the image quality in printing process of halftone screening for information hiding, a halftone screening security technique based on the phase feature of space filling curves is studied in this paper. This method effectively solves the problem of moire and optimizes the quality of the screening, so that the images presented after screening have achieved good visual effect. The pseudo-random scrambling encryption of the plaintext information and the halftone screening technique based on the phase feature of the space filling curves are carried out when screening,which not only eliminates the common moire in the screening but also improves the image quality and the security of information.
End-fire silicon optical phased array with half-wavelength spacing
Kossey, Michael R.; Rizk, Charbel; Foster, Amy C.
2018-01-01
We demonstrate an optical phased array with emitting elements spaced at half the operational wavelength. The device is a one-dimensional array fabricated on an integrated silicon platform for operation at a wavelength of 1.55 μm. Light is emitted end-fire from the chip edge where the waveguides are terminated. The innovative design and high confinement afforded by the silicon waveguides enables λ/2 spacing (775-nm pitch) at the output thereby eliminating grating lobes and maximizing the power in the main lobe. Steering is achieved by inducing a phase shift between the waveguide feeds via integrated thermo-optic heaters. The device forms a beam with a full-width half-maximum angular width of 17°, and we demonstrate beam steering over a 64° range limited only by the element factor.
Phase Space Analysis of a Gravitationally-Induced, Steady-State Nonequilibrium
Energy Technology Data Exchange (ETDEWEB)
Sheehan, D.P.; Tobe, R. [Univ. of San Diego, CA (United States). Dept. of Physics; Glick, J.; Langton, J.A.; Gagliardi, M. [Univ. of San Diego, CA (United States). Dept. of Mathematics and Computer Science; Duncan, T. [Portland State Univ., OR (United States). Center for Science Ed.
2002-04-01
Recently a new type of pressure gradient was introduced, a gravitationally-induced, dynamically-maintained, steady-state pressure gradient (GDSPG). In this paper, three dimensional numerical test particle simulations detail its phase space structure. These verify the underlying physical mechanism originally hypothesized for its operation and support key assumptions upon which it is based. The GDSPG appears to be a member of a more general class of steady-state nonequilibrium systems that arise under extreme thermodynamic conditions.
Generation of a novel phase-space-based cylindrical dose kernel for IMRT optimization.
Zhong, Hualiang; Chetty, Indrin J
2012-05-01
Improving dose calculation accuracy is crucial in intensity-modulated radiation therapy (IMRT). We have developed a method for generating a phase-space-based dose kernel for IMRT planning of lung cancer patients. Particle transport in the linear accelerator treatment head of a 21EX, 6 MV photon beam (Varian Medical Systems, Palo Alto, CA) was simulated using the EGSnrc/BEAMnrc code system. The phase space information was recorded under the secondary jaws. Each particle in the phase space file was associated with a beamlet whose index was calculated and saved in the particle's LATCH variable. The DOSXYZnrc code was modified to accumulate the energy deposited by each particle based on its beamlet index. Furthermore, the central axis of each beamlet was calculated from the orientation of all the particles in this beamlet. A cylinder was then defined around the central axis so that only the energy deposited within the cylinder was counted. A look-up table was established for each cylinder during the tallying process. The efficiency and accuracy of the cylindrical beamlet energy deposition approach was evaluated using a treatment plan developed on a simulated lung phantom. Profile and percentage depth doses computed in a water phantom for an open, square field size were within 1.5% of measurements. Dose optimized with the cylindrical dose kernel was found to be within 0.6% of that computed with the nontruncated 3D kernel. The cylindrical truncation reduced optimization time by approximately 80%. A method for generating a phase-space-based dose kernel, using a truncated cylinder for scoring dose, in beamlet-based optimization of lung treatment planning was developed and found to be in good agreement with the standard, nontruncated scoring approach. Compared to previous techniques, our method significantly reduces computational time and memory requirements, which may be useful for Monte-Carlo-based 4D IMRT or IMAT treatment planning.
Gilardoni, S S; Martini, M; Métral, E; Steerenberg, R; Müller, A-S
2006-01-01
Recently, a novel technique to perform multi-turn extraction from a circular particle accelerator was proposed. It is based on beam splitting and trapping, induced by a slow crossing of a nonlinear resonance, inside stable islands of transverse phase space. Experiments at the CERN Proton Synchrotron started in 2002 and evidence of beam splitting was obtained by summer 2004. In this paper the measurement results achieved with both a low- and a high-intensity, single-bunch proton beam are presented.
Bopp operators and phase-space spin dynamics: application to rotational quantum Brownian motion
Energy Technology Data Exchange (ETDEWEB)
Zueco, D [Departamento de Fisica de la Materia Condensada e, Instituto de Ciencia de Materiales de Aragon, C.S.I.C.-Universidad de Zaragoza, E-50009 Zaragoza (Spain); Calvo, I [Laboratorio Nacional de Fusion, Asociacion EURATOM-CIEMAT, E-28040 Madrid (Spain)
2007-04-27
For non-relativistic spinless particles, Bopp operators give an elegant and simple way to compute the dynamics of quasiprobability distributions in the phase-space formulation of Quantum Mechanics. In this work, we present a generalization of Bopp operators for spins and apply our results to the case of open spin systems. This approach allows to take the classical limit in a transparent way, recovering the corresponding Fokker-Planck equation.
Communication: phase space approach to laser-driven electronic wavepacket propagation.
Takemoto, Norio; Shimshovitz, Asaf; Tannor, David J
2012-07-07
We propose a phase space method to propagate a quantum wavepacket driven by a strong external field. The method employs the periodic von Neumann basis with biorthogonal exchange recently introduced for the calculation of the energy eigenstates of time-independent quantum systems [A. Shimshovitz and D. J. Tannor, Phys. Rev. Lett. (in press) [e-print arXiv:1201.2299v1
Entanglement with negative Wigner function of almost 3,000 atoms heralded by one photon
McConnell, Robert; Zhang, Hao; Hu, Jiazhong; Ćuk, Senka; Vuletić, Vladan
2015-03-01
Quantum-mechanically correlated (entangled) states of many particles are of interest in quantum information, quantum computing and quantum metrology. Metrologically useful entangled states of large atomic ensembles have been experimentally realized, but these states display Gaussian spin distribution functions with a non-negative Wigner quasiprobability distribution function. Non-Gaussian entangled states have been produced in small ensembles of ions, and very recently in large atomic ensembles. Here we generate entanglement in a large atomic ensemble via an interaction with a very weak laser pulse; remarkably, the detection of a single photon prepares several thousand atoms in an entangled state. We reconstruct a negative-valued Wigner function--an important hallmark of non-classicality--and verify an entanglement depth (the minimum number of mutually entangled atoms) of 2,910 +/- 190 out of 3,100 atoms. Attaining such a negative Wigner function and the mutual entanglement of virtually all atoms is unprecedented for an ensemble containing more than a few particles. Although the achieved purity of the state is slightly below the threshold for entanglement-induced metrological gain, further technical improvement should allow the generation of states that surpass this threshold, and of more complex Schrödinger cat states for quantum metrology and information processing. More generally, our results demonstrate the power of heralded methods for entanglement generation, and illustrate how the information contained in a single photon can drastically alter the quantum state of a large system.
Entanglement with negative Wigner function of three thousand atoms heralded by one photon
McConnell, Robert; Zhang, Hao; Hu, Jiazhong; Ćuk, Senka; Vuletić, Vladan
2016-06-01
Quantum-mechanically correlated (entangled) states of many particles are of interest in quantum information, quantum computing and quantum metrology. Metrologically useful entangled states of large atomic ensembles have been experimentally realized [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], but these states display Gaussian spin distribution functions with a non-negative Wigner function. Non-Gaussian entangled states have been produced in small ensembles of ions [11, 12], and very recently in large atomic ensembles [13, 14, 15]. Here, we generate entanglement in a large atomic ensemble via the interaction with a very weak laser pulse; remarkably, the detection of a single photon prepares several thousand atoms in an entangled state. We reconstruct a negative-valued Wigner function, an important hallmark of nonclassicality, and verify an entanglement depth (minimum number of mutually entangled atoms) of 2910 ± 190 out of 3100 atoms. Attaining such a negative Wigner function and the mutual entanglement of virtually all atoms is unprecedented for an ensemble containing more than a few particles. While the achieved purity of the state is slightly below the threshold for entanglement-induced metrological gain, further technical improvement should allow the generation of states that surpass this threshold, and of more complex Schrödinger cat states for quantum metrology and information processing.
Defending against Internet worms using a phase space method from chaos theory
Hu, Jing; Gao, Jianbo; Rao, Nageswara S.
2007-04-01
Enterprise networks are facing ever-increasing security threats from Distributed Denial of Service (DDoS) attacks, worms, viruses, intrusions, Trojans, port scans, and network misuses, and thus effective monitoring approaches to quickly detect these activities are greatly needed. In this paper, we employ chaos theory and propose an interesting phase space method to detect Internet worms. An Internet worm is a self-propagating program that automatically replicates itself to vulnerable systems and spreads across the Internet. Most deployed worm-detection systems are signature-based. They look for specific byte sequences (called attack signatures) that are known to appear in the attack traffic. Conventionally, the signatures are manually identified by human experts through careful analysis of the byte sequence from captured attack traffic. We propose to embed the traffic sequence to a high-dimensional phase space using chaos theory. We have observed that the signature sequence of a specific worm will occupy specific regions in the phase space, which may be appropriately called the invariant subspace of the worm. The invariant subspace of the worm separates itself widely from the subspace of the normal traffic. This separation allows us to construct three simple metrics, each of which completely separates 100 normal traffic streams from 200 worm traffic streams, without training in the conventional sense. Therefore, the method is at least as accurate as any existing methods. More importantly, our method is much faster than existing methods, such as based on expectation maximization and hidden Markov models.
Phase-space dynamics of opposition control in wall-bounded turbulent flows
Hwang, Yongyun; Ibrahim, Joseph; Yang, Qiang; Doohan, Patrick
2017-11-01
The phase-space dynamics of wall-bounded shear flow in the presence of opposition control is explored by examining the behaviours of a pair of nonlinear equilibrium solutions (exact coherent structures), edge state and life time of turbulence at low Reynolds numbers. While the control modifies statistics and phase-space location of the edge state and the lower-branch equilibrium solution very little, it is also found to regularise the periodic orbit on the edge state by reverting a period-doubling bifurcation. Only the upper-branch equilibrium solution and mean turbulent state are significantly modified by the control, and, in phase space, they gradually approach the edge state on increasing the control gain. It is found that this behaviour results in a significant reduction of the life time of turbulence, indicating that the opposition control significantly increases the probability that the turbulent solution trajectory passes through the edge state. Finally, it is shown that the opposition control increases the critical Reynolds number of the onset of the equilibrium solutions, indicating its capability of transition delay. This work is sponsored by the Engineering and Physical Sciences Research Council (EPSRC) in the UK (EP/N019342/1).
Subcritical Growth of Electron Phase-space Holes in Planetary Radiation Belts
Osmane, A.; Wilson, L. B., III; Turner, D. L.; Dimmock, A. P.; Pulkkinen, T. I.
2017-12-01
The discovery of self-sustained coherent structures with large-amplitude electric fields (E ˜ 10 - 100 mV/m) by the Van Allen Probes has revealed alternative routes through which energy-momentum exchange can take place in planetary radiation belts. When originating from energetic electrons in Landau resonance with large-amplitude whistlers, phase-space electron holes form with small amplitudes of the order of the hot to cold electron density, i.e., qφ/T_e≃ n_h/n_c ≃ 10^{-3}, and orders of magnitude smaller than observed values of the largest phase-space holes amplitude, i.e., qφ /T_e ≃ 1. In this report we present a mechanism through which electron holes can grow nonlinearly (i.e. γ ∝ √{φ}) and subcritically as a result of momentum exchange with passing (untrapped) electrons. Growth rates are computed analytically for plasma parameters consistent with those measured in the Earth's radiation belts under quiet and disturbed conditions. Our results provide an explanation for the fast growth of electron phase-space holes in the Earth's radiation belts from small initial values qφ/T_c ≃ 10^{-3}, to larger values of the order qφ /T_e ≃ 1.
Development of a coal fired pulse combustor for residential space heating. Phase I, Final report
Energy Technology Data Exchange (ETDEWEB)
NONE
1988-04-01
This report presents the results of the first phase of a program for the development of a coal-fired residential combustion system. This phase consisted of the design, fabrication, testing, and evaluation of an advanced pulse combustor sized for residential space heating requirements. The objective was to develop an advanced pulse coal combustor at the {approximately} 100,000 Btu/hr scale that can be integrated into a packaged space heating system for small residential applications. The strategy for the development effort included the scale down of the feasibility unit from 1-2 MMBtu/hr to 100,000 Btu/hr to establish a baseline for isolating the effect of scale-down and new chamber configurations separately. Initial focus at the residential scale was concentrated on methods of fuel injection and atomization in a bare metal unit. This was followed by incorporating changes to the advanced chamber designs and testing of refractory-lined units. Multi-fuel capability for firing oil or gas as a secondary fuel was also established. Upon completion of the configuration and component testing, an optimum configuration would be selected for integrated testing of the pulse combustor unit. The strategy also defined the use of Dry Ultrafine Coal (DUC) for Phases 1 and 2 of the development program with CWM firing to be a product improvement activity for a later phase of the program.
Energy Technology Data Exchange (ETDEWEB)
Milosic, Timo
2014-04-14
Accelerator facilities require access to many beam parameters during operation. The field of beam instrumentation serves this crucial role in commissioning, setup and optimisation of the facility. An important information is contained in the phase-space distribution of the accelerated particles. In case of GSI (Helmholtzzentrum fuer Schwerionenforschung) those are ions from protons to uranium. If established methods to access certain beam parameters do not exist, new approaches have to emerge. This is the case for the presented measurement setup which has been designed and realised by Forck et al. to support commissioning of the GSI high-current injector. It is aiming at an experimental method to access the longitudinal phase-space distribution at low energies of 1.4 AMeV. Established methods for higher energies and based on the measurement of the electric field distribution are not feasible at non-relativistic velocities. The presented method is based on a time-of-flight (TOF) measurement between two particle detectors. A modification allows, alternatively, the direct measurement of the kinetic energy using a mono-crystalline (MC) diamond detector. Currently, besides others, the focus of the optimisation of the injector is put on the longitudinal phase-space distribution. It allows for a systematic optimisation of the matching into the accelerator cavities and, thus, an improved transmission as well as lower emittance values. The new accelerator facility FAIR (Facility for Antiproton and Ion Research), a large-scale upgrade at GSI, requires an improved beam quality at the existing injector. In this work the experimental setup is investigated for its feasibility to measure the longitudinal phase-space distribution. To this end, the phase and momentum of the single ions along the beam axis have to be determined with high precision. Finally, the longitudinal phase-space distribution is identified with the measured ensemble. The setup is presented in detail
Directory of Open Access Journals (Sweden)
Yu-E Song
2014-01-01
Full Text Available The Wigner-Ville distribution (WVD based on the linear canonical transform (LCT (WDL not only has the advantages of the LCT but also has the good properties of WVD. In this paper, some new and important properties of the WDL are derived, and the relationships between WDL and some other time-frequency distributions are discussed, such as the ambiguity function based on LCT (LCTAF, the short-time Fourier transform (STFT, and the wavelet transform (WT. The WDLs of some signals are also deduced. A novel definition of the WVD based on the LCT and generalized instantaneous autocorrelation function (GWDL is proposed and its applications in the estimation of parameters for QFM signals are also discussed. The GWDL of the QFM signal generates an impulse and the third-order phase coefficient of QFM signal can be estimated in accordance with the position information of such impulse. The proposed algorithm is fast because it only requires 1-dimensional maximization. Also the new algorithm only has fourth-order nonlinearity thus it has accurate estimation and low signal-to-noise ratio (SNR threshold. The simulation results are provided to support the theoretical results.
Vogman, Genia
Plasmas are made up of charged particles whose short-range and long-range interactions give rise to complex behavior that can be difficult to fully characterize experimentally. One of the most complete theoretical descriptions of a plasma is that of kinetic theory, which treats each particle species as a probability distribution function in a six-dimensional position-velocity phase space. Drawing on statistical mechanics, these distribution functions mathematically represent a system of interacting particles without tracking individual ions and electrons. The evolution of the distribution function(s) is governed by the Boltzmann equation coupled to Maxwell's equations, which together describe the dynamics of the plasma and the associated electromagnetic fields. When collisions can be neglected, the Boltzmann equation is reduced to the Vlasov equation. High-fidelity simulation of the rich physics in even a subset of the full six-dimensional phase space calls for low-noise high-accuracy numerical methods. To that end, this dissertation investigates a fourth-order finite-volume discretization of the Vlasov-Maxwell equation system, and addresses some of the fundamental challenges associated with applying these types of computationally intensive enhanced-accuracy numerical methods to phase space simulations. The governing equations of kinetic theory are described in detail, and their conservation-law weak form is derived for Cartesian and cylindrical phase space coordinates. This formulation is well known when it comes to Cartesian geometries, as it is used in finite-volume and finite-element discretizations to guarantee local conservation for numerical solutions. By contrast, the conservation-law weak form of the Vlasov equation in cylindrical phase space coordinates is largely unexplored, and to the author's knowledge has never previously been solved numerically. Thereby the methods described in this dissertation for simulating plasmas in cylindrical phase space
Synchronization in area-preserving maps: Effects of mixed phase space and coherent structures.
Mahata, Sasibhusan; Das, Swetamber; Gupte, Neelima
2016-06-01
The problem of synchronization of coupled Hamiltonian systems presents interesting features due to the mixed nature (regular and chaotic) of the phase space. We study these features by examining the synchronization of unidirectionally coupled area-preserving maps coupled by the Pecora-Caroll method. The master stability function approach is used to study the stability of the synchronous state and to identify the percentage of synchronizing initial conditions. The transient to synchronization shows intermittency with an associated power law. The mixed nature of the phase space of the studied map has notable effects on the synchronization times as is seen in the case of the standard map. Using finite-time Lyapunov exponent analysis, we show that the synchronization of the maps occurs in the neighborhood of invariant curves in the phase space. The phase differences of the coevolving trajectories show intermittency effects, due to the existence of stable periodic orbits contributing locally stable directions in the synchronizing neighborhoods. Furthermore, the value of the nonlinearity parameter, as well as the location of the initial conditions play an important role in the distribution of synchronization times. We examine drive response combinations which are chaotic-chaotic, chaotic-regular, regular-chaotic, and regular-regular. A range of scaling behavior is seen for these cases, including situations where the distributions show a power-law tail, indicating long synchronization times for at least some of the synchronizing trajectories. The introduction of coherent structures in the system changes the situation drastically. The distribution of synchronization times crosses over to exponential behavior, indicating shorter synchronization times, and the number of initial conditions which synchronize increases significantly, indicating an enhancement in the basin of synchronization. We discuss the implications of our results.
Phase-space Analysis in the Group and Cluster Environment: Time Since Infall and Tidal Mass Loss
Rhee, Jinsu; Smith, Rory; Choi, Hoseung; Yi, Sukyoung K.; Jaffé, Yara; Candlish, Graeme; Sánchez-Jánssen, Ruben
2017-07-01
Using the latest cosmological hydrodynamic N-body simulations of groups and clusters, we study how location in phase-space coordinates at z = 0 can provide information on environmental effects acting in clusters. We confirm the results of previous authors showing that galaxies tend to follow a typical path in phase-space as they settle into the cluster potential. As such, different regions of phase-space can be associated with different times since first infalling into the cluster. However, in addition, we see a clear trend between total mass loss due to cluster tides and time since infall. Thus, we find location in phase-space provides information on both infall time and tidal mass loss. We find the predictive power of phase-space diagrams remains even when projected quantities are used (I.e., line of sight velocities, and projected distances from the cluster). We provide figures that can be directly compared with observed samples of cluster galaxies and we also provide the data used to make them as supplementary data to encourage the use of phase-space diagrams as a tool to understand cluster environmental effects. We find that our results depend very weakly on galaxy mass or host mass, so the predictions in our phase-space diagrams can be applied to groups or clusters alike, or to galaxy populations from dwarfs up to giants.
Rönsch, J R; Richter, R; Hartrott, M V; Abrahamyan, K; Asova, G; Bähr, J; Dimitrov, G; Grabosch, H J; Han, J H; Khodyachykh, S; Krasilnikov, M; Liu, S; Lüdecke, H L; Miltchev, V; Oppelt, A; Petrosian, B; Riemann, S; Staykov, L; Stephan, F
2005-01-01
PITZ generates electron bunches of about 5 MeV. To optimize the RF-gun and to fulfill the requirements of the bunch compressor for an efficient compression the longitudinal phase space behind the gun has to be studied. A measurement of the longitudinal phase space comprises a correlated measurement of momentum and temporal distribution. The momentum distribution is measured by deflecting the electron bunch using a spectrometer magnet. A subsequent Cherenkov radiator (silica aerogel) * transforms the electron bunch into a light pulse with equal temporal and spatial distribution, which is imaged onto a streak camera by an optical transmission line ** to measure the longitudinal distribution. The longitudinal phase space was measured for different temporal laser distributions, charges and phases between RF field and laser. Physical effects in the dipole, optical transmission line and streak camera, which influence the longitudinal phase space measurements are taken into account. The measurement results were comp...
Beisert, Susan; Rodriggs, Michael; Moreno, Francisco; Korth, David; Gibson, Stephen; Lee, Young H.; Eagles, Donald E.
2013-01-01
Now that major assembly of the International Space Station (ISS) is complete, NASA's focus has turned to using this high fidelity in-space research testbed to not only advance fundamental science research, but also demonstrate and mature technologies and develop operational concepts that will enable future human exploration missions beyond low Earth orbit. The ISS as a Testbed for Analog Research (ISTAR) project was established to reduce risks for manned missions to exploration destinations by utilizing ISS as a high fidelity micro-g laboratory to demonstrate technologies, operations concepts, and techniques associated with crew autonomous operations. One of these focus areas is the development and execution of ISS Testbed for Analog Research (ISTAR) autonomous flight crew procedures intended to increase crew autonomy that will be required for long duration human exploration missions. Due to increasing communications delays and reduced logistics resupply, autonomous procedures are expected to help reduce crew reliance on the ground flight control team, increase crew performance, and enable the crew to become more subject-matter experts on both the exploration space vehicle systems and the scientific investigation operations that will be conducted on a long duration human space exploration mission. These tests make use of previous or ongoing projects tested in ground analogs such as Research and Technology Studies (RATS) and NASA Extreme Environment Mission Operations (NEEMO). Since the latter half of 2012, selected non-critical ISS systems crew procedures have been used to develop techniques for building ISTAR autonomous procedures, and ISS flight crews have successfully executed them without flight controller involvement. Although the main focus has been preparing for exploration, the ISS has been a beneficiary of this synergistic effort and is considering modifying additional standard ISS procedures that may increase crew efficiency, reduce operational costs, and
Solving the inverse Ising problem by mean-field methods in a clustered phase space with many states.
Decelle, Aurélien; Ricci-Tersenghi, Federico
2016-07-01
In this work we explain how to properly use mean-field methods to solve the inverse Ising problem when the phase space is clustered, that is, many states are present. The clustering of the phase space can occur for many reasons, e.g., when a system undergoes a phase transition, but also when data are collected in different regimes (e.g., quiescent and spiking regimes in neural networks). Mean-field methods for the inverse Ising problem are typically used without taking into account the eventual clustered structure of the input configurations and may lead to very poor inference (e.g., in the low-temperature phase of the Curie-Weiss model). In this work we explain how to modify mean-field approaches when the phase space is clustered and we illustrate the effectiveness of our method on different clustered structures (low-temperature phases of Curie-Weiss and Hopfield models).
Singh, Bhim S.
2003-01-01
NASA is preparing to undertake science-driven exploration missions. The NASA Exploration Team's vision is a cascade of stepping stones. The stepping-stone will build the technical capabilities needed for each step with multi-use technologies and capabilities. An Agency-wide technology investment and development program is necessary to implement the vision. The NASA Exploration Team has identified a number of areas where significant advances are needed to overcome all engineering and medical barriers to the expansion of human space exploration beyond low-Earth orbit. Closed-loop life support systems and advanced propulsion and power technologies are among the areas requiring significant advances from the current state-of-the-art. Studies conducted by the National Academy of Science's National Research Council and Workshops organized by NASA have shown that multiphase flow and phase change play a crucial role in many of these advanced technology concepts. Lack of understanding of multiphase flow, phase change, and interfacial phenomena in the microgravity environment has been a major hurdle. An understanding of multiphase flow and phase change in microgravity is, therefore, critical to advancing many technologies needed. Recognizing this, the Office of Biological and Physical Research (OBPR) has initiated a strategic research thrust to augment the ongoing fundamental research in fluid physics and transport phenomena discipline with research especially aimed at understanding key multiphase flow related issues in propulsion, power, thermal control, and closed-loop advanced life support systems. A plan for integrated theoretical and experimental research that has the highest probability of providing data, predictive tools, and models needed by the systems developers to incorporate highly promising multiphase-based technologies is currently in preparation. This plan is being developed with inputs from scientific community, NASA mission planners and industry personnel
Detecting kinematic boundary surfaces in phase space: particle mass measurements in SUSY-like events
Debnath, Dipsikha; Gainer, James S.; Kilic, Can; Kim, Doojin; Matchev, Konstantin T.; Yang, Yuan-Pao
2017-06-01
We critically examine the classic endpoint method for particle mass determination, focusing on difficult corners of parameter space, where some of the measurements are not independent, while others are adversely affected by the experimental resolution. In such scenarios, mass differences can be measured relatively well, but the overall mass scale remains poorly constrained. Using the example of the standard SUSY decay chain \\tilde{q}\\to {\\tilde{χ}}_2^0\\to \\tilde{ℓ}\\to {\\tilde{χ}}_1^0 , we demonstrate that sensitivity to the remaining mass scale parameter can be recovered by measuring the two-dimensional kinematical boundary in the relevant three-dimensional phase space of invariant masses squared. We develop an algorithm for detecting this boundary, which uses the geometric properties of the Voronoi tessellation of the data, and in particular, the relative standard deviation (RSD) of the volumes of the neighbors for each Voronoi cell in the tessellation. We propose a new observable, \\overline{Σ} , which is the average RSD per unit area, calculated over the hypothesized boundary. We show that the location of the \\overline{Σ} maximum correlates very well with the true values of the new particle masses. Our approach represents the natural extension of the one-dimensional kinematic endpoint method to the relevant three dimensions of invariant mass phase space.
James Webb Space Telescope Optical Simulation Testbed: Segmented Mirror Phase Retrieval Testing
Laginja, Iva; Egron, Sylvain; Brady, Greg; Soummer, Remi; Lajoie, Charles-Philippe; Bonnefois, Aurélie; Long, Joseph; Michau, Vincent; Choquet, Elodie; Ferrari, Marc; Leboulleux, Lucie; Mazoyer, Johan; N’Diaye, Mamadou; Perrin, Marshall; Petrone, Peter; Pueyo, Laurent; Sivaramakrishnan, Anand
2018-01-01
The James Webb Space Telescope (JWST) Optical Simulation Testbed (JOST) is a hardware simulator designed to produce JWST-like images. A model of the JWST three mirror anastigmat is realized with three lenses in form of a Cooke Triplet, which provides JWST-like optical quality over a field equivalent to a NIRCam module, and an Iris AO segmented mirror with hexagonal elements is standing in for the JWST segmented primary. This setup successfully produces images extremely similar to NIRCam images from cryotesting in terms of the PSF morphology and sampling relative to the diffraction limit.The testbed is used for staff training of the wavefront sensing and control (WFS&C) team and for independent analysis of WFS&C scenarios of the JWST. Algorithms like geometric phase retrieval (GPR) that may be used in flight and potential upgrades to JWST WFS&C will be explored. We report on the current status of the testbed after alignment, implementation of the segmented mirror, and testing of phase retrieval techniques.This optical bench complements other work at the Makidon laboratory at the Space Telescope Science Institute, including the investigation of coronagraphy for segmented aperture telescopes. Beyond JWST we intend to use JOST for WFS&C studies for future large segmented space telescopes such as LUVOIR.
Non-singular Brans–Dicke collapse in deformed phase space
Energy Technology Data Exchange (ETDEWEB)
Rasouli, S.M.M., E-mail: mrasouli@ubi.pt [Departamento de Física, Universidade da Beira Interior, Rua Marquês d’Avila e Bolama, 6200 Covilhã (Portugal); Centro de Matemática e Aplicações (CMA - UBI), Universidade da Beira Interior, Rua Marquês d’Avila e Bolama, 6200 Covilhã (Portugal); Physics Group, Qazvin Branch, Islamic Azad University, Qazvin (Iran, Islamic Republic of); Ziaie, A.H., E-mail: ah_ziaie@sbu.ac.ir [Department of Physics, Shahid Beheshti University, G. C., Evin, 19839 Tehran (Iran, Islamic Republic of); Department of Physics, Shahid Bahonar University, PO Box 76175, Kerman (Iran, Islamic Republic of); Jalalzadeh, S., E-mail: shahram.jalalzadeh@unila.edu.br [Federal University of Latin-American Integration, Technological Park of Itaipu PO box 2123, Foz do Iguaçu-PR, 85867-670 (Brazil); Moniz, P.V., E-mail: pmoniz@ubi.pt [Departamento de Física, Universidade da Beira Interior, Rua Marquês d’Avila e Bolama, 6200 Covilhã (Portugal); Centro de Matemática e Aplicações (CMA - UBI), Universidade da Beira Interior, Rua Marquês d’Avila e Bolama, 6200 Covilhã (Portugal)
2016-12-15
We study the collapse process of a homogeneous perfect fluid (in FLRW background) with a barotropic equation of state in Brans–Dicke (BD) theory in the presence of phase space deformation effects. Such a deformation is introduced as a particular type of non-commutativity between phase space coordinates. For the commutative case, it has been shown in the literature (Scheel, 1995), that the dust collapse in BD theory leads to the formation of a spacetime singularity which is covered by an event horizon. In comparison to general relativity (GR), the authors concluded that the final state of black holes in BD theory is identical to the GR case but differs from GR during the dynamical evolution of the collapse process. However, the presence of non-commutative effects influences the dynamics of the collapse scenario and consequently a non-singular evolution is developed in the sense that a bounce emerges at a minimum radius, after which an expanding phase begins. Such a behavior is observed for positive values of the BD coupling parameter. For large positive values of the BD coupling parameter, when non-commutative effects are present, the dynamics of collapse process differs from the GR case. Finally, we show that for negative values of the BD coupling parameter, the singularity is replaced by an oscillatory bounce occurring at a finite time, with the frequency of oscillation and amplitude being damped at late times.
Interference effects in phased beam tracing using exact half-space solutions.
Boucher, Matthew A; Pluymers, Bert; Desmet, Wim
2016-12-01
Geometrical acoustics provides a correct solution to the wave equation for rectangular rooms with rigid boundaries and is an accurate approximation at high frequencies with nearly hard walls. When interference effects are important, phased geometrical acoustics is employed in order to account for phase shifts due to propagation and reflection. Error increases, however, with more absorption, complex impedance values, grazing incidence, smaller volumes and lower frequencies. Replacing the plane wave reflection coefficient with a spherical one reduces the error but results in slower convergence. Frequency-dependent stopping criteria are then applied to avoid calculating higher order reflections for frequencies that have already converged. Exact half-space solutions are used to derive two additional spherical wave reflection coefficients: (i) the Sommerfeld integral, consisting of a plane wave decomposition of a point source and (ii) a line of image sources located at complex coordinates. Phased beam tracing using exact half-space solutions agrees well with the finite element method for rectangular rooms with absorbing boundaries, at low frequencies and for rooms with different aspect ratios. Results are accurate even for long source-to-receiver distances. Finally, the crossover frequency between the plane and spherical wave reflection coefficients is discussed.
Wigner's infinite spin representations and inert matter
Energy Technology Data Exchange (ETDEWEB)
Schroer, Bert [CBPF, Rio de Janeiro (Brazil); Institut fuer Theoretische Physik FU-Berlin, Berlin (Germany)
2017-06-15
Positive energy ray representations of the Poincare group are naturally subdivided into three classes according to their mass and spin content: m > 0, m = 0 finite helicity and m = 0 infinite spin. For a long time the localization properties of the massless infinite spin class remained unknown, until it became clear that such matter does not permit compact spacetime localization and its generating covariant fields are localized on semi-infinite space-like strings. Using a new perturbation theory for higher spin fields we present arguments which support the idea that infinite spin matter cannot interact with normal matter and we formulate conditions under which this also could happen for finite spin s > 1 fields. This raises the question of a possible connection between inert matter and dark matter. (orig.)
Directory of Open Access Journals (Sweden)
F. Zhou
2006-11-01
Full Text Available Space charge and coherent synchrotron radiation may deteriorate electron beam quality when the beam passes through a magnetic bunch compressor. This paper presents the transverse phase-space tomographic measurements for a compressed beam at 60 MeV, around which energy the first stage of magnetic bunch compression takes place in most advanced linacs. Transverse phase-space bifurcation of a compressed beam is observed at that energy, but the degree of the space charge-induced bifurcation is appreciably lower than the one observed at 12 MeV.
Dust environment of an airless object: A phase space study with kinetic models
Kallio, E.; Dyadechkin, S.; Fatemi, S.; Holmström, M.; Futaana, Y.; Wurz, P.; Fernandes, V. A.; Álvarez, F.; Heilimo, J.; Jarvinen, R.; Schmidt, W.; Harri, A.-M.; Barabash, S.; Mäkelä, J.; Porjo, N.; Alho, M.
2016-01-01
The study of dust above the lunar surface is important for both science and technology. Dust particles are electrically charged due to impact of the solar radiation and the solar wind plasma and, therefore, they affect the plasma above the lunar surface. Dust is also a health hazard for crewed missions because micron and sub-micron sized dust particles can be toxic and harmful to the human body. Dust also causes malfunctions in mechanical devices and is therefore a risk for spacecraft and instruments on the lunar surface. Properties of dust particles above the lunar surface are not fully known. However, it can be stated that their large surface area to volume ratio due to their irregular shape, broken chemical bonds on the surface of each dust particle, together with the reduced lunar environment cause the dust particles to be chemically very reactive. One critical unknown factor is the electric field and the electric potential near the lunar surface. We have developed a modelling suite, Dusty Plasma Environments: near-surface characterisation and Modelling (DPEM), to study globally and locally dust environments of the Moon and other airless bodies. The DPEM model combines three independent kinetic models: (1) a 3D hybrid model, where ions are modelled as particles and electrons are modelled as a charged neutralising fluid, (2) a 2D electrostatic Particle-in-Cell (PIC) model where both ions and electrons are treated as particles, and (3) a 3D Monte Carlo (MC) model where dust particles are modelled as test particles. The three models are linked to each other unidirectionally; the hybrid model provides upstream plasma parameters to be used as boundary conditions for the PIC model which generates the surface potential for the MC model. We have used the DPEM model to study properties of dust particles injected from the surface of airless objects such as the Moon, the Martian moon Phobos and the asteroid RQ36. We have performed a (v0, m/q)-phase space study where the
Mid- and long-term runoff predictions by an improved phase-space reconstruction model.
Hong, Mei; Wang, Dong; Wang, Yuankun; Zeng, Xiankui; Ge, Shanshan; Yan, Hengqian; Singh, Vijay P
2016-07-01
In recent years, the phase-space reconstruction method has usually been used for mid- and long-term runoff predictions. However, the traditional phase-space reconstruction method is still needs to be improved. Using the genetic algorithm to improve the phase-space reconstruction method, a new nonlinear model of monthly runoff is constructed. The new model does not rely heavily on embedding dimensions. Recognizing that the rainfall-runoff process is complex, affected by a number of factors, more variables (e.g. temperature and rainfall) are incorporated in the model. In order to detect the possible presence of chaos in the runoff dynamics, chaotic characteristics of the model are also analyzed, which shows the model can represent the nonlinear and chaotic characteristics of the runoff. The model is tested for its forecasting performance in four types of experiments using data from six hydrological stations on the Yellow River and the Yangtze River. Results show that the medium-and long-term runoff is satisfactorily forecasted at the hydrological stations. Not only is the forecasting trend accurate, but also the mean absolute percentage error is no more than 15%. Moreover, the forecast results of wet years and dry years are both good, which means that the improved model can overcome the traditional ''wet years and dry years predictability barrier,'' to some extent. The model forecasts for different regions are all good, showing the universality of the approach. Compared with selected conceptual and empirical methods, the model exhibits greater reliability and stability in the long-term runoff prediction. Our study provides a new thinking for research on the association between the monthly runoff and other hydrological factors, and also provides a new method for the prediction of the monthly runoff. Copyright © 2015 Elsevier Inc. All rights reserved.
Nakhjiri, Navid
This research presents algorithms for the numerical phase space analysis of large sets of trajectories. These involve propagating sections of phase space and studying the evolution of orbital characteristics which can be viewed as mapping dynamical properties of the system. Generating these maps is tedious and computationally expensive. This research proposes using an efficient numerical integration method based on a modified Picard integration for generating these maps. This numerical integration method is selected based on its potential use for developing parallel integration algorithms for massively parallel hardware such as Graphic Processing Units (GPUs). A requirement for the modified Picard integration is a method to transform vector fields to polynomial form in astrodynamics problems. This thesis demonstrates the transformation to polynomial form for simple and complex vector fields encountered in astrodynamics. This research also discusses the improvements of using this method for both parallel and sequential integrations. The integration method additionally provides the possibility to study nonlinear uncertainty propagations for a system by offering an efficient method to calculate high order state transition tensors. In the case of uncertainty propagation for large sets of trajectories, unscented transformation can be used to enhance the grid generation for maps. Besides the difficulties involved in generating maps, they are not immediately usable in practice. This research proposes the use of image processing and clustering analysis algorithms to autonomously detect and extract dynamical features from these maps. To do so, image segmentation algorithms such as k-mean clustering, contrast segmentation, and texture segmentation have been used. Additionally, this thesis discuses representing these sections of phase space using sets of B-spline and Gaussian mixtures. Based on data clustering, an enhanced map generation method is also introduced, which
The phase-space structure of nearby dark matter as constrained by the SDSS
Leclercq, Florent; Jasche, Jens; Lavaux, Guilhem; Wandelt, Benjamin; Percival, Will
2017-06-01
Previous studies using numerical simulations have demonstrated that the shape of the cosmic web can be described by studying the Lagrangian displacement field. We extend these analyses, showing that it is now possible to perform a Lagrangian description of cosmic structure in the nearby Universe based on large-scale structure observations. Building upon recent Bayesian large-scale inference of initial conditions, we present a cosmographic analysis of the dark matter distribution and its evolution, referred to as the dark matter phase-space sheet, in the nearby universe as probed by the Sloan Digital Sky Survey main galaxy sample. We consider its stretchings and foldings using a tetrahedral tessellation of the Lagrangian lattice. The method provides extremely accurate estimates of nearby density and velocity fields, even in regions of low galaxy density. It also measures the number of matter streams, and the deformation and parity reversals of fluid elements, which were previously thought inaccessible using observations. We illustrate the approach by showing the phase-space structure of known objects of the nearby Universe such as the Sloan Great Wall, the Coma cluster and the Boötes void. We dissect cosmic structures into four distinct components (voids, sheets, filaments, and clusters), using the Lagrangian classifiers DIVA, ORIGAMI, and a new scheme which we introduce and call LICH. Because these classifiers use information other than the sheer local density, identified structures explicitly carry physical information about their formation history. Accessing the phase-space structure of dark matter in galaxy surveys opens the way for new confrontations of observational data and theoretical models. We have made our data products publicly available.
Exploring links between foundation phase teachers’ content knowledge and their example spaces
Directory of Open Access Journals (Sweden)
Samantha Morrison
2013-12-01
Full Text Available This paper explores two foundation phase teachers’ example spaces (a space in the mind where examples exist when teaching number-related topics in relation to snapshots of their content knowledge (CK. Data was collected during a pilot primary maths for teaching course that included assessments of teacher content knowledge (CK. An analysis of a content-knowledge focused pre-test developed for the larger study indicated a relatively high score for one teacher and a low score for the other. Using Rowland’s (2008 framework, an analysis of classroom practice showed associations between a higher CK and the extent of a teacher’s example space and more coherent connections between different representational forms. Although no hard claims or generalisations of the link between teachers’ example spaces and their level of mathematics content knowledge can be made here, this study reinforces evidence of the need to increase teachers’ CK from a pedagogic perspective in order to raise the level of mathematics teaching and learning in the South African landscape.
Space charge and beam stability issues of the Fermilab proton driver in Phase I
Energy Technology Data Exchange (ETDEWEB)
K. Y. Ng
2001-08-24
Issues concerning beam stability of the proposed Fermilab Proton Driver are studied in its Phase I. Although the betatron tune shifts are dominated by space charge, these shifts are less than 0.25 and will therefore not drive the symmetric and antisymmetric modes of the beam envelope into instability. The longitudinal space charge force is large and inductive inserts may be needed to compensate for the distortion of the rf potential. Although the longitudinal impedance is space charge dominated, it will not drive any microwave instability, unless the real part of the impedance coming from the inductive inserts and wall resistivity of the beam tube are large enough. The design of the beam tube is therefore very important in order to limit the flow of eddy current and keep wall resistivity low. The transverse impedance is also space charge dominated. With the Proton Driver operated at an imaginary transition gamma, however, Landau damping will never be canceled and beam stability can be maintained with negative chromaticities.
Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers.
Consolino, L; Taschin, A; Bartolini, P; Bartalini, S; Cancio, P; Tredicucci, A; Beere, H E; Ritchie, D A; Torre, R; Vitiello, M S; De Natale, P
2012-01-01
Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5 THz quantum cascade laser to a free-space comb, generated in a LiNbO(3) waveguide and covering the 0.1-6 THz frequency range. We show that even a small fraction (laser is sufficient to generate a beat note suitable for phase-locking to the comb, paving the way to novel metrological-grade terahertz applications, including high-resolution spectroscopy, manipulation of cold molecules, astronomy and telecommunications.
Kinetics for Reduction of Iron Ore Based on the Phase Space Reconstruction
Directory of Open Access Journals (Sweden)
Guo-Feng Fan
2014-01-01
Full Text Available A series of smelting reduction experiments has been carried out with high-phosphorus iron ore of the different bases and heating rates by thermogravimetric analyzer. The derivative thermo gravimetric (DTG data have been obtained from the experiments. After analyzing its phase space reconstruction, it is found that DTG phase portrait contains with a clear double “∞” attractor characteristic by one-order delay. The statistical properties of the attractor inside and outside the double “∞” structures are characterized with interface chemical reaction control and diffusion control stage in dynamic smelting process, respectively; the results are deserved to be a reference value on understanding of the mechanism and optimization and control of the process in smelting reduction of high-phosphorus iron ore.
Energy Technology Data Exchange (ETDEWEB)
Dabrowska, A. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Freier, P.S. [Minnesota Univ., Minneapolis, MN (United States). School of Physics and Astronomy; Holynski, R. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Jones, W.V. [Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Physics and Astronomy; Jurak, A. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Kudzia, D. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Olszewski, A. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Szarska, M. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Trzupek, A. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Waddington, C.J. [Minnesota Univ., Minneapolis, MN (United States). School of Physics and Astronomy; Wefel, J.P. [Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Physics and Astronomy; Wilczynska, B. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Wilczynski, H. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Wolter, W. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Wosiek, B. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); Wozniak, K. [Henryk Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland)
1995-08-01
The fluctuations of produced particles are investigated in central collisions of proton, oxygen and sulphur projectiles with (Ag,Br) target nuclei at 200 GeV per nucleon. The analysis is carried out in terms of factorial moments and correlation integrals in different pseudorapidity regions. Evidence is found for nonstatistical fluctuations. These fluctuations depend weakly on the phase space, although a slightly stronger effect is seen in the forward pseudorapidity region. The dependence of the observed effect on the mass of the projectile particle disagrees with the expectations of super-position models. The results of this analysis indicate that a self-similar cascade process is the origin of the fluctuations, even though the association of the observed effect with the occurrence of a second order phase transition cannot be definitely ruled out. (orig.)
Directory of Open Access Journals (Sweden)
S. Gilardoni
2006-10-01
Full Text Available Recently, a novel technique to perform multiturn extraction from a circular particle accelerator was proposed. It is based on beam splitting and trapping, induced by a slow crossing of a nonlinear resonance, inside stable islands of transverse phase space. Experiments at the CERN Proton Synchrotron started in 2002 and evidence of beam splitting was obtained by summer 2004. In this paper, the measurement results achieved with both a low- and a high-intensity, single-bunch proton beam are presented.
The Impact of Early Design Phase Risk Identification Biases on Space System Project Performance
Reeves, John D., Jr.; Eveleigh, Tim; Holzer, Thomas; Sarkani, Shahryar
2012-01-01
Risk identification during the early design phases of complex systems is commonly implemented but often fails to result in the identification of events and circumstances that truly challenge project performance. Inefficiencies in cost and schedule estimation are usually held accountable for cost and schedule overruns, but the true root cause is often the realization of programmatic risks. A deeper understanding of frequent risk identification trends and biases pervasive during space system design and development is needed, for it would lead to improved execution of existing identification processes and methods.
Interpretation of bent-crystal rocking curves using phase-space diagrams
Ren, B; Chapman, L D; Wu, X Y; Zhong, Z; Ivanov, I; Huang, X
2000-01-01
In developing a double bent-Laue crystal monochromator for synchrotron-based monochromatic computed tomography system, we applied a special projection of the phase-space diagram to interpret the shape of bent crystal rocking curves. Unlike the rigorous approach of the ray-tracing method, this graphical method provides direct pictures that allow checks of the physical significance of the shapes of the rocking curves, thereby providing quick guidelines for matching two bent crystals. The method's usefulness is demonstrated with our crexperimental results, and its limitations are discussed.
Superradiant emission from a cascade atomic ensemble by positive-P phase space method simulation
Jen, Hsiang-Hua
2012-06-01
We numerically simulate the superradiant emission properties from an atomic ensemble with cascade level configuration. The correlated spontaneous emissions (signal then idler fields) are initiated by quantum fluctuations of the ensemble. We apply the positive-P phase space method to investigate the dynamics of the atoms and counter-propagating emissions in the four-wave mixing condition. The light field intensities are calculated, and the signal-idler correlation function is studied for different optical depths of the atomic ensemble. Shorter correlation time scale for a denser atomic ensemble implies a broader spectral window required to store or retrieve the idler pulse.
New features of electron phase space holes observed by the THEMIS mission.
Andersson, L; Ergun, R E; Tao, J; Roux, A; Lecontel, O; Angelopoulos, V; Bonnell, J; McFadden, J P; Larson, D E; Eriksson, S; Johansson, T; Cully, C M; Newman, D L; Newman, D N; Goldman, M V; Glassmeier, K-H; Baumjohann, W
2009-06-05
Observations of electron phase-space holes (EHs) in Earth's plasma sheet by the THEMIS satellites include the first detection of a magnetic perturbation (deltaB_{ parallel}) parallel to the ambient magnetic field (B0). EHs with a detectable deltaB_{ parallel} have several distinguishing features including large electric field amplitudes, a magnetic perturbation perpendicular to B0, high speeds ( approximately 0.3c) along B0, and sizes along B0 of tens of Debye lengths. These EHs have a significant center potential (Phi approximately k_{B}T_{e}/e), suggesting strongly nonlinear behavior nearby such as double layers or magnetic reconnection.
Particle Control in Phase Space by Global K-Means Clustering
DEFF Research Database (Denmark)
Frederiksen, Jacob Trier; Lapenta, G.; Pessah, M. E.
2015-01-01
decreasing or increasing the entire particle population, based on k-means clustering of the data. In essence the procedure amounts to merging or splitting particles by statistical means, throughout the entire simulation volume in question, while minimizing a 6-dimensional total distance measure to preserve...... --- \\emph{i.e.}, Nf≲0.33Ni. Interestingly, we find that an accurate particle splitting step can be performed using k-means as well; this from an argument of symmetry. The split solution, using k-means, places splitted particles optimally, to obtain maximal spanning on the phase space manifold...
Hubble Space Telescope cycle 5. Phase 1: Proposal instructions, version 4.0
Madau, Piero (Editor)
1994-01-01
This document has the following purposes: it describes the information that must be submitted to the Space Telescope Science Institute by Phase 1 proposers, both electronically and on paper, and describes how to submit it; it describes how to fill out the proposal LATEX templates; it describes how to estimate the number of spacecraft orbits that the proposed observations will require; it provides detailed information about the parameters that are used in the forms to describe the requested observations; and it provides information about the preparation and electronic submission of proposal files. Examples of completed proposal forms are included.
Koulaouzidis, George; Cappiello, Grazia; Mazomenos, Evangelos B; Maharatna, Koushik; Morgan, John
2014-01-01
Ventricular arrhythmias comprise a group of disorders which manifest clinically in a variety of ways from ventricular premature beats (VPB) and no sustained ventricular tachycardia (in healthy subjects) to sudden cardiac death due to ventricular tachyarrhythmia in patients with and/or without structural heart disease. Ventricular fibrillation (VF) and ventricular tachycardia (VT) are the most common electrical mechanisms for cardiac arrest. Accurate and automatic recognition of these arrhythmias from electrocardiography (ECG) is a crucial task for medical professionals. The purpose of this research is to develop a new index for the differential diagnosis of normal sinus rhythm (SR) and ventricular arrhythmias, based on phase space reconstruction (PSR).
Solid Phase Characterization of Tank 241-AY-102 Annulus Space Particulate
Energy Technology Data Exchange (ETDEWEB)
Cooke, G. A.
2013-01-30
The Special Analytical Studies Group at the 222-S Laboratory (222-S) examined the particulate recovered from a series of samples from the annular space of tank 241-AY-102 (AY-102) using solid phase characterization (SPC) methods. These include scanning electron microscopy (SEM) using the ASPEX®1 scanning electron microscope, X-ray diffraction (XRD) using the Rigaku®2 MiniFlex X-ray diffractometer, and polarized light microscopy (PLM) using the Nikon®3 Eclipse Pol optical microscope. The SEM is equipped with an energy dispersive X-ray spectrometer (EDS) to provide chemical information.
GeneLab Phase 2: Integrated Search Data Federation of Space Biology Experimental Data
Tran, P. B.; Berrios, D. C.; Gurram, M. M.; Hashim, J. C. M.; Raghunandan, S.; Lin, S. Y.; Le, T. Q.; Heher, D. M.; Thai, H. T.; Welch, J. D.;
2016-01-01
The GeneLab project is a science initiative to maximize the scientific return of omics data collected from spaceflight and from ground simulations of microgravity and radiation experiments, supported by a data system for a public bioinformatics repository and collaborative analysis tools for these data. The mission of GeneLab is to maximize the utilization of the valuable biological research resources aboard the ISS by collecting genomic, transcriptomic, proteomic and metabolomic (so-called omics) data to enable the exploration of the molecular network responses of terrestrial biology to space environments using a systems biology approach. All GeneLab data are made available to a worldwide network of researchers through its open-access data system. GeneLab is currently being developed by NASA to support Open Science biomedical research in order to enable the human exploration of space and improve life on earth. Open access to Phase 1 of the GeneLab Data Systems (GLDS) was implemented in April 2015. Download volumes have grown steadily, mirroring the growth in curated space biology research data sets (61 as of June 2016), now exceeding 10 TB/month, with over 10,000 file downloads since the start of Phase 1. For the period April 2015 to May 2016, most frequently downloaded were data from studies of Mus musculus (39) followed closely by Arabidopsis thaliana (30), with the remaining downloads roughly equally split across 12 other organisms (each 10 of total downloads). GLDS Phase 2 is focusing on interoperability, supporting data federation, including integrated search capabilities, of GLDS-housed data sets with external data sources, such as gene expression data from NIHNCBIs Gene Expression Omnibus (GEO), proteomic data from EBIs PRIDE system, and metagenomic data from Argonne National Laboratory's MG-RAST. GEO and MG-RAST employ specifications for investigation metadata that are different from those used by the GLDS and PRIDE (e.g., ISA-Tab). The GLDS Phase 2 system
A space-time fractional phase-field model with tunable sharpness and decay behavior and its efficient numerical simulation
Li, Zheng; Wang, Hong; Yang, Danping
2017-10-01
We present a space-time fractional Allen-Cahn phase-field model that describes the transport of the fluid mixture of two immiscible fluid phases. The space and time fractional order parameters control the sharpness and the decay behavior of the interface via a seamless transition of the parameters. Although they are shown to provide more accurate description of anomalous diffusion processes and sharper interfaces than traditional integer-order phase-field models do, fractional models yield numerical methods with dense stiffness matrices. Consequently, the resulting numerical schemes have significantly increased computational work and memory requirement. We develop a lossless fast numerical method for the accurate and efficient numerical simulation of the space-time fractional phase-field model. Numerical experiments shows the utility of the fractional phase-field model and the corresponding fast numerical method.
Energy Technology Data Exchange (ETDEWEB)
Liu, Jian; Miller, William H.
2007-07-10
It is shown how quantum mechanical time correlation functions [defined, e.g., in Eq. (1.1)] can be expressed, without approximation, in the same form as the linearized approximation of the semiclassical initial value representation (LSC-IVR), or classical Wigner model, for the correlation function [cf. Eq. (2.1)], i.e., as a phase space average (over initial conditions for trajectories) of the Wigner functions corresponding to the two operators. The difference is that the trajectories involved in the LSC-IVR evolve classically, i.e., according to the classical equations of motion, while in the exact theory they evolve according to generalized equations of motion that are derived here. Approximations to the exact equations of motion are then introduced to achieve practical methods that are applicable to complex (i.e., large) molecular systems. Four such methods are proposed in the paper--the full Wigner dynamics (full WD) and the 2nd order WD based on 'Winger trajectories', and the full Donoso-Martens dynamics (full DMD) and the 2nd order DMD based on 'Donoso-Martens trajectories'--all of which can be viewed as generalizations of the original LSC-IVR method. Numerical tests of these four versions of this new approach are made for two anharmonic model problems, and for each the momentum autocorrelation function (i.e., operators linear in coordinate or momentum operators) and the force autocorrelation function (non-linear operators) have been calculated. These four new approximate treatments are indeed seen to be significant improvements to the original LSC-IVR approximation.
Warped Wigner-Hough Transform for Defect Reflection Enhancement in Ultrasonic Guided Wave Monitoring
Directory of Open Access Journals (Sweden)
Luca De Marchi
2012-01-01
Full Text Available To improve the defect detectability of Lamb wave inspection systems, the application of nonlinear signal processing was investigated. The approach is based on a Warped Frequency Transform (WFT to compensate the dispersive behavior of ultrasonic guided waves, followed by a Wigner-Ville time-frequency analysis and the Hough Transform to further improve localization accuracy. As a result, an automatic detection procedure to locate defect-induced reflections was demonstrated and successfully tested by analyzing numerically simulated Lamb waves propagating in an aluminum plate. The proposed method is suitable for defect detection and can be easily implemented for real-world structural health monitoring applications.
Uncertainty Principles for Wigner-Ville Distribution Associated with the Linear Canonical Transforms
Directory of Open Access Journals (Sweden)
Yong-Gang Li
2014-01-01
Full Text Available The Heisenberg uncertainty principle of harmonic analysis plays an important role in modern applied mathematical applications, signal processing and physics community. The generalizations and extensions of the classical uncertainty principle to the novel transforms are becoming one of the most hottest research topics recently. In this paper, we firstly obtain the uncertainty principle for Wigner-Ville distribution and ambiguity function associate with the linear canonical transform, and then the n-dimensional cases are investigated in detail based on the proposed Heisenberg uncertainty principle of the n-dimensional linear canonical transform.
The Collected Works of Eugene Paul Wigner Historical, Philosophical, and Socio-Political Papers
Wigner, Eugene Paul
2001-01-01
Not only was EP Wigner one of the most active creators of 20th century physics, he was also always interested in expressing his opinion in philosophical, political or sociological matters This volume of his collected works covers a wide selection of his essays about science and society, about himself and his colleagues Annotated by J Mehra, this volume will become an important source of reference for historians of science, and it will be pleasant reading for every physicist interested in forming ideas in modern physics
Comment on "Observation of the Wigner-Huntington transition to metallic hydrogen".
Goncharov, Alexander F; Struzhkin, Viktor V
2017-08-25
Dias and Silvera (Research Article, 17 February 2017, p. 715) report on the observation of the Wigner-Huntington transition to metallic hydrogen at 495 gigapascals at 5.5 and 83 kelvin. Here, we show that the claim of metallic behavior is not supported by the presented data, which are scarce, contradictory, and do not prove the presence of hydrogen in the high-pressure cavity. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.
Energy Technology Data Exchange (ETDEWEB)
O' Donnell, Kane; Visser, Matt, E-mail: kco61@uclive.ac.nz, E-mail: matt.visser@msor.vuw.ac.nz [School of Mathematics, Statistics, and Operations Research, Victoria University of Wellington, Wellington (New Zealand)
2011-07-15
The purpose of this paper is to provide an elementary introduction to the qualitative and quantitative results of velocity combination in special relativity, including the Wigner rotation and Thomas precession. We utilize only the most familiar tools of special relativity, in arguments presented at three differing levels: (1) utterly elementary, which will suit a first course in relativity; (2) intermediate, to suit a second course; and (3) advanced, to suit higher level students. We then give a summary of useful results and suggest further reading in this often obscure field.
General phase spaces: from discrete variables to rotor and continuum limits
Albert, Victor V.; Pascazio, Saverio; Devoret, Michel H.
2017-12-01
We provide a basic introduction to discrete-variable, rotor, and continuous-variable quantum phase spaces, explaining how the latter two can be understood as limiting cases of the first. We extend the limit-taking procedures used to travel between phase spaces to a general class of Hamiltonians (including many local stabilizer codes) and provide six examples: the Harper equation, the Baxter parafermionic spin chain, the Rabi model, the Kitaev toric code, the Haah cubic code (which we generalize to qudits), and the Kitaev honeycomb model. We obtain continuous-variable generalizations of all models, some of which are novel. The Baxter model is mapped to a chain of coupled oscillators and the Rabi model to the optomechanical radiation pressure Hamiltonian. The procedures also yield rotor versions of all models, five of which are novel many-body extensions of the almost Mathieu equation. The toric and cubic codes are mapped to lattice models of rotors, with the toric code case related to U(1) lattice gauge theory.
Exploring the data constrained phase space of the last Antarctic glacial cycle
Lecavalier, Benoit; Tarasov, Lev
2017-04-01
The evolution of the Antarctic Ice Sheet over the last two glacial cycles is studied using the Glacial Systems Model (GSM). Glaciological modelling is an effective tool to generate continental-scale reconstructions over glacial cycles, but the models depend on parameterizations to account for the deficiencies (e.g., missing physics, unresolved sub-grid processes, uncertain boundary conditions) inherent in any numerical model. These parameters, considered together, form a parameter phase space from which sets of parameters can be sampled; each set corresponds to an ice sheet reconstruction. The GSM has been updated with a number of recent developments: hybrid SIA-SSA physics, Schoof grounding line parameterization, broadened degrees of freedom in the climate forcing, sub-shelf melt explicitly dependent on ocean temperatures, improved hydrofracturing, cliff failure at the margins, basal topographic uncertainties, impact of basal drag roughness and subgrid statistics, and first order geoidal corrections in the coupled glacial isostatic adjustment component. Parametric uncertainties are defined in the GSM using >36 ensemble parameters. Prior to conducting a full Bayesian calibration, one must first validate the ability of the GSM to simulate a broad range of responses. We attempt this by latin hypercube sampling of the parameter phase space and comparing the model predictions against our constraint database consisting of past elevation, extent and relative sea level observations and the present day geometry. We document the capability of the GSM to envelope the observational constraints given the parametric uncertainties and discuss the implications for the evolution of the Antarctic Ice Sheet.
Transverse phase space mapping of relativistic electron beams using optical transition radiation
Directory of Open Access Journals (Sweden)
G. P. Le Sage
1999-12-01
Full Text Available Optical transition radiation (OTR has proven to be a versatile and effective diagnostic for measuring the profile, divergence, and emittance of relativistic electron beams with a wide range of parameters. Diagnosis of the divergence of modern high brightness beams is especially well suited to OTR interference (OTRI techniques, where multiple dielectric or metal foils are used to generate a spatially coherent interference pattern. Theoretical analysis of measured OTR and OTRI patterns allows precise measurement of electron beam emittance characteristics. Here we describe an extension of this technique to allow mapping of divergence characteristics as a function of transverse coordinates within a measured beam. We present the first experimental analysis of the transverse phase space of an electron beam using all optical techniques. Comparing an optically masked portion of the beam to the entire beam, we measure different angular spread and average direction of the particles. Direct measurement of the phase-space ellipse tilt angle has been demonstrated using this optical masking technique.
Su, Zhi-Yuan; Wu, Tzuyin; Yang, Po-Hua; Wang, Yeng-Tseng
2008-04-01
The heartbeat rate signal provides an invaluable means of assessing the sympathetic-parasympathetic balance of the human autonomic nervous system and thus represents an ideal diagnostic mechanism for detecting a variety of disorders such as epilepsy, cardiac disease and so forth. The current study analyses the dynamics of the heartbeat rate signal of known epilepsy sufferers in order to obtain a detailed understanding of the heart rate pattern during a seizure event. In the proposed approach, the ECG signals are converted into heartbeat rate signals and the embedology theorem is then used to construct the corresponding multidimensional phase space. The dynamics of the heartbeat rate signal are then analyzed before, during and after an epileptic seizure by examining the maximum Lyapunov exponent and the correlation dimension of the attractors in the reconstructed phase space. In general, the results reveal that the heartbeat rate signal transits from an aperiodic, highly-complex behaviour before an epileptic seizure to a low dimensional chaotic motion during the seizure event. Following the seizure, the signal trajectories return to a highly-complex state, and the complex signal patterns associated with normal physiological conditions reappear.
Non-singular Brans-Dicke collapse in deformed phase space
Rasouli, S M M; Jalalzadeh, S; Moniz, P V
2016-01-01
We study the collapse process of a homogeneous perfect fluid (in FLRW background) with a barotropic equation of state in Brans-Dicke (BD) theory in the presence of phase space deformation effects. Such a deformation is introduced as a particular type of non-commutativity between phase space coordinates. For the commutative case, it has been shown in the literature [M.A. Scheel, S.L. Shapiro and S.A. Teukolsky, Phys. Rev. D. 51, 4236 (1995)], that the dust collapse in BD theory leads to the formation of a spacetime singularity which is covered by an event horizon. In comparison to general relativity (GR), the authors concluded that the final state of black holes in BD theory is identical to the GR case but differs from GR during the dynamical evolution of the collapse process. However, the presence of non-commutative effects influences the dynamics of the collapse scenario and consequently a non-singular evolution is developed in the sense that a bounce emerges at a minimum radius, after which an expanding pha...
Theory of Superthermal, Wide, Electron Phase-Space Holes and Bipolar Fields*
Goldman, M. V.; Newman, D. L.
2008-12-01
Laboratory reconnection experiments [1] and recent magnetospheric spacecraft observations [2] are beginning to find bipolar fields with a spatial half-width equal to many Debye lengths (10 or more) traveling at high speeds (faster than the thermal velocity of the bulk of electrons). Electron phase-space hole solutions of the nonlinear Poisson-Vlasov equations (stationary in a frame co-moving with the hole) are constructed analytically with these properties by assuming there is secondary component of the electron distribution. This component can be a tail on the electron distribution or a beam. The hole velocity will be close to the velocity at the end of the tail or the velocity of the beam, provided the ions are moving with sufficient velocity in the frame of the hole. Vlasov simulations are used to study accessibility and stability of these solutions. * Work supported by DOE, NASA, and NSF [1]W. Fox, M. Porkolab, J. Egedal, N. Katz, A. Le, and A. Vrublevskis, "Observation of electron phase-space holes during magnetic reconnection in the Versatile Toroidal Facility," Abstract GP6.00029, 50th Annual Meeting of the Division of Plasma Physics, American Physical Society (Dallas, Nov.~2008). [2] R. E. Ergun and J. Tao, private communication.
On Dual Phase-Space Relativity, the Machian Principle and Modified Newtonian Dynamics
Directory of Open Access Journals (Sweden)
Castro C.
2005-04-01
Full Text Available We investigate the consequences of the Mach’s principle of inertia within the context of the Dual Phase Space Relativity which is compatible with the Eddington-Dirac large numbers coincidences and may provide with a physical reason behind the observed anomalous Pioneer acceleration and a solution to the riddle of the cosmological constant problem. The cosmological implications of Non-Archimedean Geometry by assigning an upper impossible scale in Nature and the cosmological variations of the fundamental constants are also discussed. We study the corrections to Newtonian dynamics resulting from the Dual Phase Space Relativity by analyzing the behavior of a test particle in a modified Schwarzschild geometry (due to the the effects of the maximal acceleration that leads in the weak-field approximation to essential modifications of the Newtonian dynamics and to violations of the equivalence principle. Finally we follow another avenue and find modified Newtonian dynamics induced by the Yang’s Noncommutative Spacetime algebra involving a lower and upper scale in Nature.
Phase space mass bound for fermionic dark matter from dwarf spheroidal galaxies
Paolo, Chiara Di; Nesti, Fabrizio; Villante, Francesco L.
2018-01-01
We reconsider the lower bound on the mass of a fermionic dark matter (DM) candidate resulting from the existence of known small Dwarf Spheroidal galaxies, in the hypothesis that their DM halo is constituted by degenerate fermions, with phase-space density limited by the Pauli exclusion principle. By relaxing the common assumption that the DM halo scale radius is tied to that of the luminous stellar component and by marginalizing on the unknown stellar velocity dispersion anisotropy, we prove that observations lead to rather weak constraints on the DM mass, that could be as low as tens of eV. In this scenario, however, the DM halos would be quite large and massive, so that a bound stems from the requirement that the time of orbital decay due to dynamical friction in the hosting Milky Way DM halo is longer than their lifetime. The smallest and nearest satellites Segue I and Willman I lead to a final lower bound of m ≳ 100 eV, still weaker than previous estimates but robust and independent on the model of DM formation and decoupling. We thus show that phase space constraints do not rule out the possibility of sub-keV fermionic DM.
An equivalent ground thermal test method for single-phase fluid loop space radiator
Directory of Open Access Journals (Sweden)
Xianwen Ning
2015-02-01
Full Text Available Thermal vacuum test is widely used for the ground validation of spacecraft thermal control system. However, the conduction and convection can be simulated in normal ground pressure environment completely. By the employment of pumped fluid loops’ thermal control technology on spacecraft, conduction and convection become the main heat transfer behavior between radiator and inside cabin. As long as the heat transfer behavior between radiator and outer space can be equivalently simulated in normal pressure, the thermal vacuum test can be substituted by the normal ground pressure thermal test. In this paper, an equivalent normal pressure thermal test method for the spacecraft single-phase fluid loop radiator is proposed. The heat radiation between radiator and outer space has been equivalently simulated by combination of a group of refrigerators and thermal electrical cooler (TEC array. By adjusting the heat rejection of each device, the relationship between heat flux and surface temperature of the radiator can be maintained. To verify this method, a validating system has been built up and the experiments have been carried out. The results indicate that the proposed equivalent ground thermal test method can simulate the heat rejection performance of radiator correctly and the temperature error between in-orbit theory value and experiment result of the radiator is less than 0.5 °C, except for the equipment startup period. This provides a potential method for the thermal test of space systems especially for extra-large spacecraft which employs single-phase fluid loop radiator as thermal control approach.
2014-03-27
regime, they were artifically seperated. Three product Møller states are placed on each of the adiabatic PES which are labeled as Π 1 2 , Π 3 2 , and Σ...previously, the channel packet method relies on intelligently choosing the expansion coefficients of the momentum representation of the reactant and...energy level in the asymptotic regime, they were artifically seperated in Fig. 6.1 in order to show which states leads to seperate adiabatic surfaces
Fedele, Micaela; Vernia, Cecilia
2017-10-01
In this paper we solve the inverse problem for the Curie-Weiss model and its multispecies version when multiple thermodynamic states are present as in the low temperature phase where the phase space is clustered. The inverse problem consists of reconstructing the model parameters starting from configuration data generated according to the distribution of the model. We demonstrate that, without taking into account the presence of many states, the application of the inversion procedure produces very poor inference results. To overcome this problem, we use the clustering algorithm. When the system has two symmetric states of positive and negative magnetizations, the parameter reconstruction can also be obtained with smaller computational effort simply by flipping the sign of the magnetizations from positive to negative (or vice versa). The parameter reconstruction fails when the system undergoes a phase transition: In that case we give the correct inversion formulas for the Curie-Weiss model and we show that they can be used to measure how close the system gets to being critical.
Yeh, Hsien-Chi; Yan, Qi-Zhong; Liang, Yu-Rong; Wang, Ying; Luo, Jun
2011-04-01
In this paper, we present the scheme and the preliminary results of an intersatellite laser ranging system that is designed for the Earth's gravity recovery mission proposed in China, called Space Advanced Gravity Measurements (SAGM). The proposed intersatellite distance is about 100 km and the precision of inter-satellite range monitoring is 10 nm/Hz(1/2) at 0.1 Hz. To meet the needs, we designed a transponder-type intersatellite laser ranging system by using a homodyne optical phase locking technique, which is different from the heterodyne optical phase-locked loop used in GRACE follow-on mission. Since an ultrastable oscillator is unnecessary in the homodyne phase-locked loop, the measurement error caused by the frequency instability of the ultrastable oscillator need not be taken into account. In the preliminary study, a heterodyne interferometer with 10-m baseline (measurement arm-length) was built up to demonstrate the validity of the measurement scheme. The measurement results show that a resolution of displacement measurement of about 3.2 nm had been achieved. © 2011 American Institute of Physics
PHASES: Opto-mechanical solutions to perform absolute spectrophotometry from space
Directory of Open Access Journals (Sweden)
Vather Dinesh
2013-04-01
Full Text Available This work provides an update of the current status of PHASES, which is a project aimed at developing a space-borne telescope to perform absolute flux calibrated spectroscopy of bright stars. PHASES will make it possible to measure micromagnitude photometric variations due to, e.g., exo-planet/moon transits. It is designed to obtain 1% RMS flux calibrated low resolution spectra in the wavelength range 370–960 nm with signal-to-noise ratios >100 for stars with V<10 in short integration times of ∼1 minute. The strategy to calibrate the system using A-type stars is outlined. PHASES will make possible a complete characterization of stars, some of them hosting planets. From the comparison of observed spectra with accurate model atmospheres stellar angular diameters will be determined with precisions of ∼0.5%. The light curves of transiting systems will be then used to extract the radius of the planet with similar precision. The demanding scientific requirements to be achieved under extreme observing conditions have shaped the optomechanical design. A computational model and a high-precision interferometric system have been developed to test the performance of the instrument.
The numerical solution of thawing process in phase change slab using variable space grid technique
Directory of Open Access Journals (Sweden)
Serttikul, C.
2007-09-01
Full Text Available This paper focuses on the numerical analysis of melting process in phase change material which considers the moving boundary as the main parameter. In this study, pure ice slab and saturated porous packed bed are considered as the phase change material. The formulation of partial differential equations is performed consisting heat conduction equations in each phase and moving boundary equation (Stefan equation. The variable space grid method is then applied to these equations. The transient heat conduction equations and the Stefan condition are solved by using the finite difference method. A one-dimensional melting model is then validated against the available analytical solution. The effect of constant temperature heat source on melting rate and location of melting front at various times is studied in detail.It is found that the nonlinearity of melting rate occurs for a short time. The successful comparison with numerical solution and analytical solution should give confidence in the proposed mathematical treatment, and encourage the acceptance of this method as useful tool for exploring practical problems such as forming materials process, ice melting process, food preservation process and tissue preservation process.
Wigner Research Centre for Physics, Hungary
2013-01-01
On 13 June 2013 CERN and the Wigner Research Centre for Physics inaugurated the Hungarian data centre in Budapest, marking the completion of the facility hosting the extension for CERN computing resources. About 500 servers, 20,000 computing cores, and 5.5 Petabytes of storage are already operational at the site. The dedicated and redundant 100 Gbit/s circuits connecting the two sites are functional since February 2013 and are among the first transnational links at this distance. The capacity at Wigner will be remotely managed from CERN, substantially extending the capabilities of the Worldwide LHC Computing Grid (WLCG) Tier-0 activities and bolstering CERN’s infrastructure business continuity.
Querlioz, Damien
2013-01-01
This book gives an overview of the quantum transport approaches for nanodevices and focuses on the Wigner formalism. It details the implementation of a particle-based Monte Carlo solution of the Wigner transport equation and how the technique is applied to typical devices exhibiting quantum phenomena, such as the resonant tunnelling diode, the ultra-short silicon MOSFET and the carbon nanotube transistor. In the final part, decoherence theory is used to explain the emergence of the semi-classical transport in nanodevices.
The universal Racah-Wigner symbol for U{sub q}(osp(1 vertical stroke 2))
Energy Technology Data Exchange (ETDEWEB)
Pawelkiewicz, Michal; Schomerus, Volker [DESY Hamburg (Germany). Theory Group; Suchanek, Paulina [DESY Hamburg (Germany). Theory Group; Wroclaw Univ. (Poland). Inst. for Theoretical Physics
2013-10-15
We propose a new and elegant formula for the Racah-Wigner symbol of self-dual continuous series of representations of U{sub q}(osp(1 vertical stroke 2)). It describes the entire fusing matrix for both NS and R sector of N=1 supersymmetric Liouville field theory. In the NS sector, our formula is related to an expression derived in an earlier paper (L. Hadaz, M. Pawelkiewicz, and V. Schomerus, arXiv:1305.4596[hep-th]). Through analytic continuation in the spin variables, our universal expression reproduces known formulas for the Racah-Wigner coefficients of finite dimensional representations.
Energy Technology Data Exchange (ETDEWEB)
Heiblum, Reuven H. [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Altaratz, Orit [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Koren, Ilan [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Feingold, Graham [Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder Colorado USA; Kostinski, Alexander B. [Department of Physics, Michigan Technological University, Houghton Michigan USA; Khain, Alexander P. [The Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem Israel; Ovchinnikov, Mikhail [Atmosphere Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Fredj, Erick [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Dagan, Guy [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Pinto, Lital [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Yaish, Ricki [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Chen, Qian [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel
2016-06-07
We study the evolution of warm convective cloud fields using large eddy simulations of continental and trade cumulus. Individual clouds are tracked a posteriori from formation to dissipation using a 3D cloud tracking algorithm and results are presented in the phase- space of center of gravity altitude versus cloud liquid water mass (CvM space). The CvM space is shown to contain rich information on cloud field characteristics, cloud morphology, and common cloud development pathways, together facilitating a comprehensive understanding of the cloud field. In this part we show how the meteorological (thermodynamic) conditions that determine the cloud properties are projected on the CvM phase space and how changes in the initial conditions affect the clouds' trajectories in this space. This part sets the stage for a detailed microphysical analysis that will be shown in part II.
NIAC Phase II Orbiting Rainbows: Future Space Imaging with Granular Systems
Quadrelli, Marco B.; Basinger, Scott; Arumugam, Darmindra; Swartzlander, Grover
2017-01-01
allow for unprecedented high resolution to discern continents and important features of other planets, hyperspectral imaging, adaptive systems, spectroscopy imaging through limb, and stable optical systems from Lagrange-points. Furthermore, future micro-miniaturization might hold promise of a further extension of our dust aperture concept to other more exciting smart dust concepts with other associated capabilities. Our objective in Phase II was to experimentally and numerically investigate how to optically manipulate and maintain the shape of an orbiting cloud of dust-like matter so that it can function as an adaptable ultra-lightweight surface. Our solution is based on the aperture being an engineered granular medium, instead of a conventional monolithic aperture. This allows building of apertures at a reduced cost, enables extremely fault-tolerant apertures that cannot otherwise be made, and directly enables classes of missions for exoplanet detection based on Fourier spectroscopy with tight angular resolution and innovative radar systems for remote sensing. In this task, we have examined the advanced feasibility of a crosscutting concept that contributes new technological approaches for space imaging systems, autonomous systems, and space applications of optical manipulation. The proposed investigation has matured the concept that we started in Phase I to TRL 3, identifying technology gaps and candidate system architectures for the space-borne cloud as an aperture.
Wu, Jiandong; Huang, Ruodong; Wan, Jiadong; Chen, Yading; Yin, Yi; Chen, George
2016-04-01
Data processing (i.e. phase identification) using the instantaneous phase φ‧(t) defined by the Hilbert transform is discussed to confirm the detecting phase of the space charge observed by the pulsed electroacoustic method under the periodic wave V a (t). The discrete voltage V a (i) of the periodic wave at the detecting phase φ(i) is used for phase identification, and φ(i) is equally distributed to obtain N p divisions for the phase within one period. The accuracy of the discrete instantaneous phase φ‧(i) is significantly determined by the number of samples N for the discrete voltage V a (i). The instantaneous phase is consistent with the real phase of pure sine and cosine waves, and this phase linearly varies with time. However, the instantaneous phase non-linearly varies with time under the periodic stress of arbitrary waveforms. This limitation can be resolved using the base wave component, i.e. sine or cosine wave of V a (t), which is acquired by the Fourier transform. Finally, the space charge behaviour in low-density polyethylene under square and sine waves with offset is detected to verify the accuracy and effectiveness of the proposed method.
Akkelin, S V; 10.1103/PhysRevC.70.064901
2004-01-01
A method allowing analysis of the overpopulation of phase space in heavy ion collisions in a model-independent way is proposed within the hydrodynamic approach. It makes it possible to extract a chemical potential of thermal pions at freeze-out, irrespective of the form of freeze-out (isothermal) hypersurface in Minkowski space and transverse flows on it. The contributions of resonance (with masses up to 2 GeV) decays to spectra, interferometry volumes, and phase- space densities are calculated and discussed in detail. The estimates of average phase-space densities and chemical potentials of thermal pions are obtained for SPS and RHIC energies. They demonstrate that multibosonic phenomena at those energies might be considered as a correction factor rather than as a significant physical effect. The analysis of the evolution of the pion average phase-space density in chemically frozen hadron systems shows that it is almost constant or slightly increases with time while the particle density and phase- space dens...
Phase separation, orbital ordering and magnetism in (La0.375Ca0.625)MnO3
Martinelli, A.; Ferretti, M.; Ritter, C.
2016-07-01
At 300 K (La0.375Ca0.625)MnO3 crystallizes in the orthorhombic Pnma space group; on cooling a Pnma → Pnma structural transition occurs due to charge-orbital ordering within the Mn sub-lattice, producing a superstructure consistent with a Wigner-crystal model with a tripling of the cell parameter a. The primary active mode yielding the observed ordered structure corresponds to the irreducible representation labelled Σ3, with wave vector (⅓,0,0). Nevertheless, the disordered polymorph stable at room temperature is retained at low temperature as a secondary phase, coexisting with the charge-orbital ordered structure. These two phases display different spin orderings; the antiferromagnetic structure associated to the charge-orbital ordered phase is characterized by a magnetic propagation wave vector k=(0,0,½), with a canted spin ordering in the ac plane, whereas a Cy-type arrangement develops within the disordered polymorph.
Prajapati, N.; Ankit, K.; Selzer, M.; Nestler, B.; Schmidt, C.; Hilgers, C.
2016-12-01
Prediction of cement volumes is an integral part of reservoir modeling. Quantitative determination of petrophysical charateristics such as permeability and water saturation are essential in order to assess the sufficiency of hydrocarbons in pore space. Conventional techniques such as well-logging provide only a qualitative understanding of the cementation history and future pore evolution. Diffused modeling approach such as the phase-field method is a viable alternative that can be used to numerically simulate pore cementation under different boundary conditions in a thermodynamically-consistent manner. Here, we use a multiphase-field model to investigate the dynamics of polycrystalline quartz precipitation from supersaturated solution in porous rock. To begin with, we validate the faceted-type anisotropy formulations of the interfacial energy function that corresponds to monocrystalline quartz using the volume-preservation technique. Next, we numerically simulate the unitaxial evolution of quartz in a 2D open space and investigate the role of misorientations and c/a ratios in the formation of quartz cement that is extensively observed in nature. Based on this sensitivity analysis, we choose a realistic c/a ratio to computationally mimic the anisotropic sealing of pore space in sandstone. We observe a large deviation of 3D sealing kinetics as compared to 2D. The decrease in 3D pore space volume during cementation is found to be inversely dependent (non-linear) on the inter-nuclei distance. Using CFD analysis, we then derive the temporal evolution of permeability in partially sealed microstructures. Finally, we highlight the capabilities of the present numerical approaches in numerically simulating 3D reactive flow during progressive sealing in porous rocks based on innovative post-processing analyses and visualization techniques.
The hyperbolic step potential: Anti-bound states, SUSY partners and Wigner time delays
Energy Technology Data Exchange (ETDEWEB)
Gadella, M. [Departamento de Física Teórica, Atómica y Óptica and IMUVA, Universidad de Valladolid, E-47011 Valladolid (Spain); Kuru, Ş. [Department of Physics, Faculty of Science, Ankara University, 06100 Ankara (Turkey); Negro, J., E-mail: jnegro@fta.uva.es [Departamento de Física Teórica, Atómica y Óptica and IMUVA, Universidad de Valladolid, E-47011 Valladolid (Spain)
2017-04-15
We study the scattering produced by a one dimensional hyperbolic step potential, which is exactly solvable and shows an unusual interest because of its asymmetric character. The analytic continuation of the scattering matrix in the momentum representation has a branch cut and an infinite number of simple poles on the negative imaginary axis which are related with the so called anti-bound states. This model does not show resonances. Using the wave functions of the anti-bound states, we obtain supersymmetric (SUSY) partners which are the series of Rosen–Morse II potentials. We have computed the Wigner reflection and transmission time delays for the hyperbolic step and such SUSY partners. Our results show that the more bound states a partner Hamiltonian has the smaller is the time delay. We also have evaluated time delays for the hyperbolic step potential in the classical case and have obtained striking similitudes with the quantum case. - Highlights: • The scattering matrix of hyperbolic step potential is studied. • The scattering matrix has a branch cut and an infinite number of poles. • The poles are associated to anti-bound states. • Susy partners using antibound states are computed. • Wigner time delays for the hyperbolic step and partner potentials are compared.
Sliding regime of conduction in 'one-dimensional Wigner crystal'
Energy Technology Data Exchange (ETDEWEB)
Artemenko, S.N., E-mail: art@cplire.ru [V.A. Kotel' nikov Institute for Radio-engineering and Electronics of Russian Academy of Sciences, Mokhovaya str. 11-7, Moscow 125009 (Russian Federation); Shapiro, D.S.; Vakhitov, R.R.; Remizov, S.V. [V.A. Kotel' nikov Institute for Radio-engineering and Electronics of Russian Academy of Sciences, Mokhovaya str. 11-7, Moscow 125009 (Russian Federation)
2012-06-01
We study theoretically transport properties of one-dimensional system of interacting electrons pinned by an impurity. Long-range Coulomb interaction in such a system is known to induce a 4k{sub F} electron density modulation characterized by extremely slow, slower than any power law, decay of the density correlations which can be described as a one-dimensional Wigner crystal. We study non-stationary regime of conduction corresponding to sliding of the 1D Wigner crystal depinned by the applied voltage. In this regime the dc current is accompanied by current oscillations with frequency f=I{sup Macron}/e. We calculate I-V curves and ac current generated by sliding. Our approach is based on the ideas of Luttinger liquid. We study also the case of magnetic impurity and show that applied voltage induces not only the electrical current, but also the spin current as well, in other words, the current becomes spin polarized. We find that a spin bias applied to the system contributes to electric current both in case of magnetic and non-magnetic impurity, and this is related to violation of the spin-charge separation at the impurity site.
Excitonic Wigner crystal and high T sub c ferromagnetism in RB sub 6
Kasuya, T
2000-01-01
The mechanisms for the high T sub c ferromagnetism in La-doped divalent hexaborides DB sub 6 are studied in detail comparing with similar family materials, in particular with YbB sub 6 , EuB sub 6 and Ce monopnictides. It is shown that in DB sub 6 the light-electron-heavy-hole paired excitonic states form the Wigner crystal, or Wigner glass in actual materials, in which the conventional intersite electron exchange interactions similar to that in Ni dominate the pair singlet formation due to the intra pair mixing causing a ferromagnetic spin glass-like ordering of electron spins. In the La-doped system La sub x D sub 1 sub - sub x B sub 6 , the population of molecular La impurity states with giant moments increases as x approaches the optimal value x sub 0 approx 0.005 for high T sub c providing vacant states for the roton-like fluctuations, which cause the high T sub c at the boundary of the delocalization of electron carriers. Therefore, the critical La concentration for delocalization coincides with the opt...
Phase-space geometry and reaction dynamics near index 2 saddles
Ezra, Gregory S.; Wiggins, Stephen
2009-05-01
We study the phase-space geometry associated with index 2 saddles of a potential energy surface and its influence on reaction dynamics for n degree-of-freedom (DoF) Hamiltonian systems. In recent years, similar studies have been carried out for index 1 saddles of potential energy surfaces, and the phase-space geometry associated with classical transition state theory has been elucidated. In this case, the existence of a normally hyperbolic invariant manifold (NHIM) of saddle stability type has been shown, where the NHIM serves as the 'anchor' for the construction of dividing surfaces having the no-recrossing property and minimal flux. For the index 1 saddle case, the stable and unstable manifolds of the NHIM are co-dimension 1 in the energy surface and have the structure of spherical cylinders, and thus act as the conduits for reacting trajectories in phase space. The situation for index 2 saddles is quite different, and their relevance for reaction dynamics has not previously been fully recognized. We show that NHIMs with their stable and unstable manifolds still exist, but that these manifolds by themselves lack sufficient dimension to act as barriers in the energy surface in order to constrain reactions. Rather, in the index 2 case there are different types of invariant manifolds, containing the NHIM and its stable and unstable manifolds, that act as co-dimension 1 barriers in the energy surface. These barriers divide the energy surface in the vicinity of the index 2 saddle into regions of qualitatively different trajectories exhibiting a wider variety of dynamical behavior than for the case of index 1 saddles. In particular, we can identify a class of trajectories, which we refer to as 'roaming trajectories', which are not associated with reaction along the classical minimum energy path (MEP). We illustrate the significance of our analysis of the index 2 saddle for reaction dynamics with two examples. The first involves isomerization on a potential energy
Exact phase boundaries and topological phase transitions of the X Y Z spin chain
Jafari, S. A.
2017-07-01
Within the block spin renormalization group, we give a very simple derivation of the exact phase boundaries of the X Y Z spin chain. First, we identify the Ising order along x ̂ or y ̂ as attractive renormalization group fixed points of the Kitaev chain. Then, in a global phase space composed of the anisotropy λ of the X Y interaction and the coupling Δ of the Δ σzσz interaction, we find that the above fixed points remain attractive in the two-dimesional parameter space. We therefore classify the gapped phases of the X Y Z spin chain as: (1) either attracted to the Ising limit of the Kitaev-chain, which in turn is characterized by winding number ±1 , depending on whether the Ising order parameter is along x ̂ or y ̂ directions; or (2) attracted to the charge density wave (CDW) phases of the underlying Jordan-Wigner fermions, which is characterized by zero winding number. We therefore establish that the exact phase boundaries of the X Y Z model in Baxter's solution indeed correspond to topological phase transitions. The topological nature of the phase transitions of the X Y Z model justifies why our analytical solution of the three-site problem that is at the core of the present renormalization group treatment is able to produce the exact phase boundaries of Baxter's solution. We argue that the distribution of the winding numbers between the three Ising phases is a matter of choice of the coordinate system, and therefore the CDW-Ising phase is entitled to host appropriate form of zero modes. We further observe that in the Kitaev-chain the renormalization group flow can be cast into a geometric progression of a properly identified parameter. We show that this new parameter is actually the size of the (Majorana) zero modes.
Dai, De-Chang; Stojkovic, Dejan
2012-10-01
We study a retarded potential solution of a massless scalar field in curved space-time. In a special ansatz for a particle at rest whose magnitude of the (scalar) charge is changing with time, we found an exact analytic solution. The solution indicates that the phase velocity of the retarded potential of a nonmoving scalar charge is position-dependent and may easily be greater than the speed of light at a given point. In the case of the Schwarzschild space-time, at the horizon, the phase velocity becomes infinitely faster than the coordinate speed of light at that point. Superluminal phase velocity is a relatively common phenomenon, with the phase velocity of the massive Klein-Gordon field as the best known example. We discuss why it is possible to have modes with superluminal phase velocity even for a massless field.
Critical phenomena in the extended phase space of Kerr-Newman-AdS black holes
Cheng, Peng; Liu, Yu-Xiao
2016-01-01
Treating the cosmological constant as a thermodynamic pressure, we investigate the critical behavior of a Kerr-Newman-AdS black hole system. The critical points for the van der Waals like phase transition are numerically solved. The highly accurate fitting formula for them is given and is found to be dependent of the charge $Q$ and angular momentum $J$. In the reduced parameter space, we find that the temperature, Gibbs free energy, and coexistence curve depend only on the dimensionless angular momentum-charge ratio $\\epsilon=J/Q^2$ rather than $Q$ and $J$. Moreover, when varying $\\epsilon$ from 0 to $\\infty$, the coexistence curve will continuously change from that of the Reissner-Nordstr\\"{o}m-AdS black hole to the Kerr-AdS black hole. These results may guide us to study the critical phenomena for other thermodynamic systems with two characteristic parameters.
Extended phase space analysis of interacting dark energy models in loop quantum cosmology
Zonunmawia, Hmar; Khyllep, Wompherdeiki; Roy, Nandan; Dutta, Jibitesh; Tamanini, Nicola
2017-10-01
The present work deals with the dynamical system investigation of interacting dark energy models (quintessence and phantom) in the framework of loop quantum cosmology by taking into account a broad class of self-interacting scalar field potentials. The main reason for studying potentials beyond the exponential type is to obtain additional critical points which can yield more interesting cosmological solutions. The stability of critical points and the asymptotic behavior of the phase space are analyzed using dynamical system tools and numerical techniques. We study two classes of interacting dark energy models and consider two specific potentials as examples: the hyperbolic potential and the inverse power-law potential. We find a rich and interesting phenomenology, including the avoidance of big rip singularities due to loop quantum effects, smooth and nonlinear transitions from matter domination to dark energy domination, and finite periods of phantom domination with dynamical crossing of the phantom barrier.
Longitudinal phase space manipulation in energy recovering linac-driven free-electron lasers
Directory of Open Access Journals (Sweden)
P. Piot
2003-03-01
Full Text Available Energy recovering an electron beam after it has participated in a free-electron laser (FEL interaction can be quite challenging because of the substantial FEL-induced energy spread and the energy antidamping that occurs during deceleration. In the Jefferson Lab infrared FEL driver accelerator, such an energy recovery scheme was implemented by properly matching the longitudinal phase space throughout the recirculation transport by employing the so-called energy compression scheme. In the present paper, after presenting a single-particle dynamics approach of the method used to energy recover the electron beam, we report on experimental validation of the method obtained by measurements of the so-called “compression efficiency” and “momentum compaction” lattice transfer maps at different locations in the recirculation transport line. We also compare these measurements with numerical tracking simulations.
APPLICATION OF VORONOI DIAGRAM TO MASK-BASED INTERCEPTING PHASE-SPACE MEASUREMENTS
Energy Technology Data Exchange (ETDEWEB)
Halavanau, A. [Fermilab; Ha, G. [POSTECH
2017-05-19
Intercepting multi-aperture masks (e.g. pepper pot or multislit mask) combined with a downstream transversedensity diagnostics (e.g. based on optical transition radiation or employing scintillating media) are commonly used for characterizing the phase space of charged particle beams and the associated emittances. The required data analysis relies on precise calculation of the RMS sizes and positions of the beamlets originated from the mask which drifted up to the analyzing diagnostics. Voronoi diagram is an efficient method for splitting a plane into subsets according to the distances between given vortices. The application of the method to analyze data from pepper pot and multislit mask based measurement is validated via numerical simulation and applied to experimental data acquired at the Argonne Wakefield Accelerator (AWA) facility. We also discuss the application of the Voronoi diagrams to quantify transverselymodulated beams distortion.
Transport of phase space densities through tetrahedral meshes using discrete flow mapping
Bajars, Janis; Sondergaard, Niels; Tanner, Gregor
2016-01-01
Discrete flow mapping was recently introduced as an efficient ray based method determining wave energy distributions in complex built up structures. Wave energy densities are transported along ray trajectories through polygonal mesh elements using a finite dimensional approximation of a ray transfer operator. In this way the method can be viewed as a smoothed ray tracing method defined over meshed surfaces. Many applications require the resolution of wave energy distributions in three-dimensional domains, such as in room acoustics, underwater acoustics and for electromagnetic cavity problems. In this work we extend discrete flow mapping to three-dimensional domains by propagating wave energy densities through tetrahedral meshes. The geometric simplicity of the tetrahedral mesh elements is utilised to efficiently compute the ray transfer operator using a mixture of analytic and spectrally accurate numerical integration. The important issue of how to choose a suitable basis approximation in phase space whilst m...
A new approach to the analysis of the phase space of f(R)-gravity
Carloni, Sante
2015-01-01
We propose a new dynamical system formalism for the analysis of f(R) cosmologies. The new approach eliminates the need for cumbersome inversions to close the dynamical system and allows the analysis of the phase space of f(R)-gravity models which cannot be investigated using the standard technique. Differently form previously proposed similar techniques, the new method is constructed in such a way to associate to the fixed points scale factors, which contain four integration constants (i.e. solutions of fourth order differential equations). In this way a new light is shed on the physical meaning of the fixed points. We apply this technique to some f(R) Lagrangians relevant for inflationary and dark energy models.
Multidimensional phase space methods for mass measurements and decay topology determination
Energy Technology Data Exchange (ETDEWEB)
Altunkaynak, Baris [Northeastern University, Department of Physics, Boston, MA (United States); Kilic, Can; Klimek, Matthew D. [The University of Texas at Austin, Theory Group, Department of Physics and Texas Cosmology Center, Austin, TX (United States)
2017-02-15
Collider events with multi-stage cascade decays fill out the kinematically allowed region in phase space with a density that is enhanced at the boundary. The boundary encodes all available information as regards the spectrum and is well populated even with moderate signal statistics due to this enhancement. In previous work, the improvement in the precision of mass measurements for cascade decays with three visible and one invisible particles was demonstrated when the full boundary information is used instead of endpoints of one-dimensional projections. We extend these results to cascade decays with four visible and one invisible particles. We also comment on how the topology of the cascade decay can be determined from the differential distribution of events in these scenarios. (orig.)
Phase space dynamics and control of the quantum particles associated to hypergraph states
Directory of Open Access Journals (Sweden)
Berec Vesna
2015-01-01
Full Text Available As today’s nanotechnology focus becomes primarily oriented toward production and manipulation of materials at the subatomic level, allowing the performance and complexity of interconnects where the device density accepts more than hundreds devices on a single chip, the manipulation of semiconductor nanostructures at the subatomic level sets its prime tasks on preserving and adequate transmission of information encoded in specified (quantum states. The presented study employs the quantum communication protocol based on the hypergraph network model where the numerical solutions of equations of motion of quantum particles are associated to vertices (assembled with device chip, which follow specific controllable paths in the phase space. We address these findings towards ultimate quest for prediction and selective control of quantum particle trajectories. In addition, presented protocols could represent valuable tool for reducing background noise and uncertainty in low-dimensional and operationally meaningful, scalable complex systems.
Laboratory observation of electron phase-space holes during magnetic reconnection.
Fox, W; Porkolab, M; Egedal, J; Katz, N; Le, A
2008-12-19
We report the observation of large-amplitude, nonlinear electrostatic structures, identified as electron phase-space holes, during magnetic reconnection experiments on the Versatile Toroidal Facility at MIT. The holes are positive electric potential spikes, observed on high-bandwidth ( approximately 2 GHz) Langmuir probes. Investigations with multiple probes establish that the holes travel at or above the electron thermal speed and have a three-dimensional, approximately spherical shape, with a scale size approximately 2 mm. This corresponds to a few electron gyroradii, or many tens of Debye lengths, which is large compared to holes considered in simulations and observed by satellites, whose length scale is typically only a few Debye lengths. Finally, a statistical study over many discharges confirms that the holes appear in conjunction with the large inductive electric fields and the creation of energetic electrons associated with the magnetic energy release.
Adequate bases of phase space master integrals for gg → h at NNLO and beyond
Höschele, Maik; Hoff, Jens; Ueda, Takahiro
2014-09-01
We study master integrals needed to compute the Higgs boson production cross section via gluon fusion in the infinite top quark mass limit, using a canonical form of differential equations for master integrals, recently identified by Henn, which makes their solution possible in a straightforward algebraic way. We apply the known criteria to derive such a suitable basis for all the phase space master integrals in afore mentioned process at next-to-next-to-leading order in QCD and demonstrate that the method is applicable to next-to-next-to-next-to-leading order as well by solving a non-planar topology. Furthermore, we discuss in great detail how to find an adequate basis using practical examples. Special emphasis is devoted to master integrals which are coupled by their differential equations.
Villar, V. Ashley; Berger, Edo; Metzger, Brian D.; Guillochon, James
2017-11-01
The duration-luminosity phase space (DLPS) of optical transients is used, mostly heuristically, to compare various classes of transient events, to explore the origin of new transients, and to influence optical survey observing strategies. For example, several observational searches have been guided by intriguing voids and gaps in this phase space. However, we should ask, do we expect to find transients in these voids given our understanding of the various heating sources operating in astrophysical transients? In this work, we explore a broad range of theoretical models and empirical relations to generate optical light curves and to populate the DLPS. We explore transients powered by adiabatic expansion, radioactive decay, magnetar spin-down, and circumstellar interaction. For each heating source, we provide a concise summary of the basic physical processes, a physically motivated choice of model parameter ranges, an overall summary of the resulting light curves and their occupied range in the DLPS, and how the various model input parameters affect the light curves. We specifically explore the key voids discussed in the literature: the intermediate-luminosity gap between classical novae and supernovae, and short-duration transients (≲ 10 days). We find that few physical models lead to transients that occupy these voids. Moreover, we find that only relativistic expansion can produce fast and luminous transients, while for all other heating sources events with durations ≲ 10 days are dim ({M}{{R}}≳ -15 mag). Finally, we explore the detection potential of optical surveys (e.g., Large Synoptic Survey Telescope) in the DLPS and quantify the notion that short-duration and dim transients are exponentially more difficult to discover in untargeted surveys.
Dechant, Andreas; Shafier, Shalom Tzvi; Kessler, David A; Barkai, Eli
2016-08-01
The Boltzmann-Gibbs density, a central result of equilibrium statistical mechanics, relates the energy of a system in contact with a thermal bath to its equilibrium statistics. This relation is lost for nonthermal systems such as cold atoms in optical lattices, where the heat bath is replaced with the laser beams of the lattice. We investigate in detail the stationary phase-space probability for Sisyphus cooling under harmonic confinement. In particular, we elucidate whether the total energy of the system still describes its stationary state statistics. We find that this is true for the center part of the phase-space density for deep lattices, where the Boltzmann-Gibbs density provides an approximate description. The relation between energy and statistics also persists for strong confinement and in the limit of high energies, where the system becomes underdamped. However, the phase-space density now exhibits heavy power-law tails. In all three cases we find expressions for the leading-order phase-space density and corrections which break the equivalence of probability and energy and violate energy equipartition. The nonequilibrium nature of the steady state is corroborated by explicit violations of detailed balance. We complement these analytical results with numerical simulations to map out the intricate structure of the phase-space density.
2016-01-01
We critically examine the classic endpoint method for particle mass determination, focusing on difficult corners of parameter space, where some of the measurements are not independent, while others are adversely affected by the experimental resolution. In such scenarios, mass differences can be measured relatively well, but the overall mass scale remains poorly constrained. Using the example of the standard SUSY decay chain $\\tilde q\\to \\tilde\\chi^0_2\\to \\tilde \\ell \\to \\tilde \\chi^0_1$, we demonstrate that sensitivity to the remaining mass scale parameter can be recovered by measuring the two-dimensional kinematical boundary in the relevant three-dimensional phase space of invariant masses squared. We develop an algorithm for detecting this boundary, which uses the geometric properties of the Voronoi tessellation of the data, and in particular, the relative standard deviation (RSD) of the volumes of the neighbors for each Voronoi cell in the tessellation. We propose a new observable, $\\bar\\Sigma$, which is ...
Electron holes in phase space: What they are and why they matter
Hutchinson, I. H.
2017-05-01
This is a tutorial and selective review explaining the fundamental concepts and some currently open questions concerning the plasma phenomenon of the electron hole. The widespread occurrence of electron holes in numerical simulations, space-craft observations, and laboratory experiments is illustrated. The elementary underlying theory is developed of a one-dimensional electron hole as a localized potential maximum, self-consistently sustained by a deficit of trapped electron phase-space density. The spatial extent of a hole is typically a few Debye lengths; what determines the minimum and maximum possible lengths is explained, addressing the key aspects of the as yet unsettled dispute between the integral and differential approaches to hole structure. In multiple dimensions, holes tend to form less readily; they generally require a magnetic field and distribution-function anisotropy. The mechanisms by which they break up are explained, noting that this transverse instability is not fully understood. Examples are given of plasma circumstances where holes play an important role, and of recent progress on understanding their holistic kinematics and self-acceleration.
Kinetic theory of phase space plateaux in a non-thermal energetic particle distribution
Energy Technology Data Exchange (ETDEWEB)
Eriksson, F., E-mail: frida.eriksson@chalmers.se; Nyqvist, R. M. [Department of Earth and Space Sciences, Chalmers University of Technology, 41296 Göteborg (Sweden); Lilley, M. K. [Physics Department, Imperial College, London SW7 2AZ (United Kingdom)
2015-09-15
The transformation of kinetically unstable plasma eigenmodes into hole-clump pairs with temporally evolving carrier frequencies was recently attributed to the emergence of an intermediate stage in the mode evolution cycle, that of an unmodulated plateau in the phase space distribution of fast particles. The role of the plateau as the hole-clump breeding ground is further substantiated in this article via consideration of its linear and nonlinear stability in the presence of fast particle collisions and sources, which are known to affect the production rates and subsequent frequency sweeping of holes and clumps. In particular, collisional relaxation, as mediated by e.g. velocity space diffusion or even simple Krook-type collisions, is found to inhibit hole-clump generation and detachment from the plateau, as it should. On the other hand, slowing down of the fast particles turns out to have an asymmetrically destabilizing/stabilizing effect, which explains the well-known result that collisional drag enhances holes and their sweeping rates but suppresses clumps. It is further demonstrated that relaxation of the plateau edge gradients has only a minor quantitative effect and does not change the plateau stability qualitatively, unless the edge region extends far into the plateau shelf and the corresponding Landau pole needs to be taken into account.
Robustness of double random phase encoding spread-space spread-spectrum image watermarking technique
Liu, Shi; Hennelly, Bryan M.; Sheridan, John T.
2013-09-01
In this paper the robustness of a recently proposed image watermarking scheme is investigated, namely the Double Random Phase Encoding spread-space spread-spectrum watermarking (DRPE SS-SS) technique. In the DRPE SS-SS method, the watermark is in the form of a digital barcode image which is numerically encrypted using a simulation of the optical DRPE process. This produces a random complex image, which is then processed to form a real valued random image with a low number of quantization levels. This signal is added to the host image. Extraction of the barcode, involves applying an inverse DRPE process to the watermarked image followed by a low pass filter. This algorithm is designed to utilize the capability of the DRPE to reversibly spread the energy of the watermarking information in both the space and spatial frequency domains, and the energy of the watermark in any spatial or spatial frequency bin is very small. The common geometric transformations and signal processing operations are performed using both the informed and the blind detections for different barcode widths and different quantization levels. The results presented indicate that the DRPE SS-SS method is robust to scaling, JPEG compression distortion, cropping, low pass and high pass filtering. It is also demonstrated that the bigger the barcode width is, the lower the false positive rate will be.
The ROCKSTAR Phase-space Temporal Halo Finder and the Velocity Offsets of Cluster Cores
Behroozi, Peter S.; Wechsler, Risa H.; Wu, Hao-Yi
2013-01-01
We present a new algorithm for identifying dark matter halos, substructure, and tidal features. The approach is based on adaptive hierarchical refinement of friends-of-friends groups in six phase-space dimensions and one time dimension, which allows for robust (grid-independent, shape-independent, and noise-resilient) tracking of substructure; as such, it is named ROCKSTAR (Robust Overdensity Calculation using K-Space Topologically Adaptive Refinement). Our method is massively parallel (up to 105 CPUs) and runs on the largest current simulations (>1010 particles) with high efficiency (10 CPU hours and 60 gigabytes of memory required per billion particles analyzed). A previous paper has shown ROCKSTAR to have excellent recovery of halo properties; we expand on these comparisons with more tests and higher-resolution simulations. We show a significant improvement in substructure recovery compared to several other halo finders and discuss the theoretical and practical limits of simulations in this regard. Finally, we present results that demonstrate conclusively that dark matter halo cores are not at rest relative to the halo bulk or substructure average velocities and have coherent velocity offsets across a wide range of halo masses and redshifts. For massive clusters, these offsets can be up to 350 km s-1 at z = 0 and even higher at high redshifts. Our implementation is publicly available at http://code.google.com/p/rockstar.
Detecting kinematic boundary surfaces in phase space: particle mass measurements in SUSY-like events
Debnath, Dipsikha; Kilic, Can; Kim, Doojin; Matchev, Konstantin T.; Yang, Yuan-Pao
2017-06-19
We critically examine the classic endpoint method for particle mass determination, focusing on difficult corners of parameter space, where some of the measurements are not independent, while others are adversely affected by the experimental resolution. In such scenarios, mass differences can be measured relatively well, but the overall mass scale remains poorly constrained. Using the example of the standard SUSY decay chain $\\tilde q\\to \\tilde\\chi^0_2\\to \\tilde \\ell \\to \\tilde \\chi^0_1$, we demonstrate that sensitivity to the remaining mass scale parameter can be recovered by measuring the two-dimensional kinematical boundary in the relevant three-dimensional phase space of invariant masses squared. We develop an algorithm for detecting this boundary, which uses the geometric properties of the Voronoi tessellation of the data, and in particular, the relative standard deviation (RSD) of the volumes of the neighbors for each Voronoi cell in the tessellation. We propose a new observable, $\\bar\\Sigma$, which is t...
Energy Technology Data Exchange (ETDEWEB)
Plesko, Catherine S [Los Alamos National Laboratory; Clement, R Ryan [Los Alamos National Laboratory; Weaver, Robert P [Los Alamos National Laboratory; Bradley, Paul A [Los Alamos National Laboratory; Huebner, Walter F [Los Alamos National Laboratory
2009-01-01
The mitigation of impact hazards resulting from Earth-approaching asteroids and comets has received much attention in the popular press. However, many questions remain about the near-term and long-term, feasibility and appropriate application of all proposed methods. Recent and ongoing ground- and space-based observations of small solar-system body composition and dynamics have revolutionized our understanding of these bodies (e.g., Ryan (2000), Fujiwara et al. (2006), and Jedicke et al. (2006)). Ongoing increases in computing power and algorithm sophistication make it possible to calculate the response of these inhomogeneous objects to proposed mitigation techniques. Here we present the first phase of a comprehensive hazard mitigation planning effort undertaken by Southwest Research Institute and Los Alamos National Laboratory. We begin by reviewing the parameter space of the object's physical and chemical composition and trajectory. We then use the radiation hydrocode RAGE (Gittings et al. 2008), Monte Carlo N-Particle (MCNP) radiation transport (see Clement et al., this conference), and N-body dynamics codes to explore the effects these variations in object properties have on the coupling of energy into the object from a variety of mitigation techniques, including deflection and disruption by nuclear and conventional munitions, and a kinetic impactor.
Insights into Inverse Materials Design from Phase Transitions in Shape Space
Cersonsky, Rose; van Anders, Greg; Dodd, Paul M.; Glotzer, Sharon C.
In designing new materials for synthesis, the inverse materials design approach posits that, given a structure, we can predict a building block optimized for self- assembly. How does that building block change as pressure is varied to maintain the same crystal structure? We address this question for entropically stabilized colloidal crystals by working in a generalized statistical thermodynamic ensemble where an alchemical potential variable is fixed and its conjugate variable, particle shape, is allowed to fluctuate. We show that there are multiple regions of shape behavior and phase transitions in shape space between these regions. Furthermore, while past literature has looked towards packing arguments for proposing shape-filling candidate building blocks for structure formation, we show that even at very high pressures, a structure will attain lowest free energy by modifying these space-filling shapes. U.S. Army Research Office under Grant Award No. W911NF-10-1-0518, Emerging Frontiers in Research and Innovation Award EFRI-1240264, National Science Foundation Grant Number ACI- 1053575, XSEDE award DMR 140129, Rackham Merit Fellowship Program.
Galactic Halo Stars in Phase Space: A Hint of Satellite Accretion?
Brook, Chris B.; Kawata, Daisuke; Gibson, Brad K.; Flynn, Chris
2003-03-01
The present-day chemical and dynamical properties of the Milky Way bear the imprint of the Galaxy's formation and evolutionary history. One of the most enduring and critical debates surrounding Galactic evolution is that regarding the competition between ``satellite accretion'' and ``monolithic collapse'' the apparent strong correlation between orbital eccentricity and metallicity of halo stars was originally used as supporting evidence for the latter. While modern-day unbiased samples no longer support the claims for a significant correlation, recent evidence has been presented by Chiba & Beers for the existence of a minor population of high-eccentricity metal-deficient halo stars. It has been suggested that these stars represent the signature of a rapid (if minor) collapse phase in the Galaxy's history. Employing velocity and integrals of motion phase-space projections of these stars, coupled with a series of N-body/smoothed particle hydrodynamic chemodynamical simulations, we suggest that an alternative mechanism for creating such stars may be the recent accretion of a polar orbit dwarf galaxy.
Trugenberger, Carlo A
2015-12-01
Recently I proposed a simple dynamical network model for discrete space-time that self-organizes as a graph with Hausdorff dimension d(H)=4. The model has a geometric quantum phase transition with disorder parameter (d(H)-d(s)), where d(s) is the spectral dimension of the dynamical graph. Self-organization in this network model is based on a competition between a ferromagnetic Ising model for vertices and an antiferromagnetic Ising model for edges. In this paper I solve a toy version of this model defined on a bipartite graph in the mean-field approximation. I show that the geometric phase transition corresponds exactly to the antiferromagnetic transition for edges, the dimensional disorder parameter of the former being mapped to the staggered magnetization order parameter of the latter. The model has a critical point with long-range correlations between edges, where a continuum random geometry can be defined, exactly as in Kazakov's famed 2D random lattice Ising model but now in any number of dimensions.
Jupiter's auroras during the Juno approach phase as observed by the Hubble Space Telescope
Nichols, J. D.; Clarke, J. T.; Orton, G. S.; Cowley, S. W. H.; Bunce, E. J.; Stallard, T.; Badman, S. V.; Grodent, D. C.; Bonfond, B.; Radioti, K.; Gerard, J. C. M. C.; Gladstone, R.; Bagenal, F.; Connerney, J. E. P.; Valek, P. W.; Ebert, R. W.; McComas, D. J.; Mauk, B.; Clark, G. B.; Kurth, W. S.; Yoshikawa, I.; Kimura, T.; Fujimoto, M.; Tao, C.; Bolton, S. J.
2016-12-01
We present movies of the Hubble Space Telescope (HST) observations of Jupiter's FUV auroras observed during the Juno approach phase and first capture orbit, and compare with Juno observations of the interplanetary medium near Jupiter and inside the magnetosphere. Jupiter's FUV auroras indicate the nature of the dynamic processes occurring in Jupiter's magnetosphere, and the approach phase provided a unique opportunity to obtain a full set of interplanetary data near to Jupiter at the time of a program of HST observations, along with the first simultaneous with Juno observations inside the magnetosphere. The overall goal was to determine the nature of the solar wind effect on Jupiter's magnetosphere. HST observations were obtained with typically 1 orbit per day over three intervals: 16 May - 7 June, 22-30 June and 11-18 July, i.e. while Juno was in the solar wind, around the bow shock and magnetosphere crossings, and in the mid-latitude middle-outer magnetospheres. We show that these intervals are characterised by particularly dynamic polar auroras, and significant variations in the auroral power output caused by e.g. dawn storms, intense main emission and poleward forms. We compare the variation of these features with Juno observations of interplanetary compression regions and the magnetospheric environment during the intervals of these observations.
Cancer as quasi-attractor in the gene expression phase space
Giuliani, A.
2017-09-01
It takes no more than 250 tissue types to build up a metazoan, and each tissue has a specific and largely invariant gene expression signature. This implies the `viable configurations' correspondent to a given activated/inactivated expression pattern over the entire genome are very few. This points to the presence of few `low energy deep valleys' correspondent to the allowed states of the system and is a direct consequence of the fact genes do not work by alone but embedded into genetic expression networks. Statistical thermodynamics formalism focusing on the changes in the degree of correlation of the studied systems allows to detect transition behavior in gene expression phase space resembling the phase transition of physical-chemistry studies. In this realm cancer can be intended as a sort of `parasite' sub-attractor of the corresponding healthy tissue that, in the case of disease, is `kinetically entrapped' into a sub-optimal solution. The consequences of such a state of affair for cancer therapies are potentially huge.
Phase space theory of evaporation in neon clusters: the role of quantum effects.
Calvo, F; Parneix, P
2009-12-31
Unimolecular evaporation of neon clusters containing between 14 and 148 atoms is theoretically investigated in the framework of phase space theory. Quantum effects are incorporated in the vibrational densities of states, which include both zero-point and anharmonic contributions, and in the possible tunneling through the centrifugal barrier. The evaporation rates, kinetic energy released, and product angular momentum are calculated as a function of excess energy or temperature in the parent cluster and compared to the classical results. Quantum fluctuations are found to generally increase both the kinetic energy released and the angular momentum of the product, but the effects on the rate constants depend nontrivially on the excess energy. These results are interpreted as due to the very few vibrational states available in the product cluster when described quantum mechanically. Because delocalization also leads to much narrower thermal energy distributions, the variations of evaporation observables as a function of canonical temperature appear much less marked than in the microcanonical ensemble. While quantum effects tend to smooth the caloric curve in the product cluster, the melting phase change clearly keeps a signature on these observables. The microcanonical temperature extracted from fitting the kinetic energy released distribution using an improved Arrhenius form further suggests a backbending in the quantum Ne(13) cluster that is absent in the classical system. Finally, in contrast to delocalization effects, quantum tunneling through the centrifugal barrier does not play any appreciable role on the evaporation kinetics of these rather heavy clusters.
Maximal vowel space method in analysis of vowels in prelingual speech phase
Directory of Open Access Journals (Sweden)
Vojnović Milan
2014-01-01
Full Text Available The main problems in the analysis of vowels which occur in prelingual speech phase are centralization of utterance and unknown dimension of vocal tract. Most researches in this field are based on the analysis of maximal vowel space (MVS because discrimination of vowels is very difficult in this early period. MVS analysis includes the estimation of vocal tract (VT physical dimensions. The aim of this research was to estimate and define changes in vowel pronunciation during prelingual speech phase. The analysis and voice recording were performed in a two month old child until he turned one. The recording was performed in 42 sessions, on average 4 sessions every month. Sound segments that look like vowel pronunciation were extracted from the recordings and were used for the formant frequencies estimation by PRAAT software. The Burg method was used for formant frequency estimation. Research results showed that MVS can be used in diagnostic procedure from a child's earliest age. MVS analysis is appropriate for a child's earliest age as a child needs to pronounce individual phonemes, and does not need to respond to speech stimuli. These results need to be confirmed on a larger sample when extended analysis should define criteria for discrimination of typical and atypical formant frequencies.
Longitudinal phase-space manipulation of ellipsoidal electron bunches in realistic fields
Directory of Open Access Journals (Sweden)
S. B. van der Geer
2006-04-01
Full Text Available Since the recent publication of a practical recipe to create “pancake” electron bunches which evolve into uniformly filled ellipsoids, a number of papers have addressed both an alternative method to create such ellipsoids as well as their behavior in realistic fields. So far, the focus has been on the possibilities to preserve the initial “thermal” transverse emittance. This paper addresses the linear longitudinal phase space of ellipsoidal bunches. It is shown that ellipsoidal bunches allow ballistic compression at subrelativistic energies, without the detrimental effects of nonlinear space-charge forces. This in turn eliminates the need for the large correlated energy spread normally required for longitudinal compression of relativistic particle beams, while simultaneously avoiding all problems related to magnetic compression. Furthermore, the linear space-charge forces of ellipsoidal bunches can be used to reduce the remaining energy spread even further, by carefully choosing the beam transverse size, in a process that is essentially the time-reversed process of the creation of an ellipsoid at the cathode. The feasibility of compression of ellipsoidal bunches is illustrated with a relatively simple setup, consisting of a half-cell S-band photogun and a two-cell booster compressor. Detailed GPT simulations in realistic fields predict that 100 pC ellipsoidal bunches can be ballistically compressed to 100 fs, at a transverse emittance of 0.7 μm, with a final energy of 3.7 MeV and an energy spread of only 50 keV.
The many-body Wigner Monte Carlo method for time-dependent ab-initio quantum simulations
Energy Technology Data Exchange (ETDEWEB)
Sellier, J.M., E-mail: jeanmichel.sellier@parallel.bas.bg; Dimov, I.
2014-09-15
The aim of ab-initio approaches is the simulation of many-body quantum systems from the first principles of quantum mechanics. These methods are traditionally based on the many-body Schrödinger equation which represents an incredible mathematical challenge. In this paper, we introduce the many-body Wigner Monte Carlo method in the context of distinguishable particles and in the absence of spin-dependent effects. Despite these restrictions, the method has several advantages. First of all, the Wigner formalism is intuitive, as it is based on the concept of a quasi-distribution function. Secondly, the Monte Carlo numerical approach allows scalability on parallel machines that is practically unachievable by means of other techniques based on finite difference or finite element methods. Finally, this method allows time-dependent ab-initio simulations of strongly correlated quantum systems. In order to validate our many-body Wigner Monte Carlo method, as a case study we simulate a relatively simple system consisting of two particles in several different situations. We first start from two non-interacting free Gaussian wave packets. We, then, proceed with the inclusion of an external potential barrier, and we conclude by simulating two entangled (i.e. correlated) particles. The results show how, in the case of negligible spin-dependent effects, the many-body Wigner Monte Carlo method provides an efficient and reliable tool to study the time-dependent evolution of quantum systems composed of distinguishable particles.
A Duty Cycle Space Vector Modulation Strategy for a Three-to-Five Phase Direct Matrix Converter
Directory of Open Access Journals (Sweden)
Rutian Wang
2018-02-01
Full Text Available The duty cycle space vector (DCSV modulation strategy is of universal significance, and the method can be utilized for different modulation approaches. In this paper, the vectors of input voltages and currents are equivalently represented by a complex two-dimensional space vector, and the vectors of output voltages and currents are equivalently represented by two two-dimensional space vectors. Then, input–output relationships in both the d1-q1 space and the d3-q3 space are obtained. Because the desired output voltages are only mapped onto a reference voltage space vector in the d1-q1 space, the reference in the d3-q3 space is regarded as zero, in order to reduce harmonics of output voltages to the greatest extent. Then, the duty cycle space vector modulation strategy of the three-to-five phase direct matrix converter (DMC is deduced. Considering the influence of the zero vector on system performance, the duty cycles are decomposed and recomposed to obtain the space vector pulse width modulation (SVPWM strategy based on the duty cycle space vector. Finally, the accuracy and feasibility of the theory are verified through experiments.
DEFF Research Database (Denmark)
Lu, Yong; Xiao, Guochun; Wang, Xiongfei
2016-01-01
The unified power quality conditioner (UPQC) is known as an effective compensation device to improve PQ for sensitive end-users. This paper investigates the operation and control of a single-phase three-leg UPQC (TL-UPQC), where a novel space vector modulation method is proposed for naturally...... solving the coupling problem introduced by the common switching leg. The modulation method is similar to the well-known space vector modulation widely used with three-phase voltage source converters, which thus brings extra flexibility to the TL-UPQC system. Two optimized modulation modes with either...
Bidari, Pooya Sobhe; Alirezaie, Javad; Tavakkoli, Jahan
2017-03-01
This paper presents a method for modeling and simulation of shear wave generation from a nonlinear Acoustic Radiation Force Impulse (ARFI) that is considered as a distributed force applied at the focal region of a HIFU transducer radiating in nonlinear regime. The shear wave propagation is simulated by solving the Navier's equation from the distributed nonlinear ARFI as the source of the shear wave. Then, the Wigner-Ville Distribution (WVD) as a time-frequency analysis method is used to detect the shear wave at different local points in the region of interest. The WVD results in an estimation of the shear wave time of arrival, its mean frequency and local attenuation which can be utilized to estimate medium's shear modulus and shear viscosity using the Voigt model.
Finite size effects in the averaged eigenvalue density of Wigner random-sign real symmetric matrices
Dhesi, G. S.; Ausloos, M.
2016-06-01
Nowadays, strict finite size effects must be taken into account in condensed matter problems when treated through models based on lattices or graphs. On the other hand, the cases of directed bonds or links are known to be highly relevant in topics ranging from ferroelectrics to quotation networks. Combining these two points leads us to examine finite size random matrices. To obtain basic materials properties, the Green's function associated with the matrix has to be calculated. To obtain the first finite size correction, a perturbative scheme is hereby developed within the framework of the replica method. The averaged eigenvalue spectrum and the corresponding Green's function of Wigner random sign real symmetric N ×N matrices to order 1 /N are finally obtained analytically. Related simulation results are also presented. The agreement is excellent between the analytical formulas and finite size matrix numerical diagonalization results, confirming the correctness of the first-order finite size expression.
Scale magnetic effect in quantum electrodynamics and the Wigner-Weyl formalism
Chernodub, M. N.; Zubkov, M. A.
2017-09-01
The scale magnetic effect (SME) is the generation of electric current due to a conformal anomaly in an external magnetic field in curved spacetime. The effect appears in a vacuum with electrically charged massless particles. Similarly to the Hall effect, the direction of the induced anomalous current is perpendicular to the direction of the external magnetic field B and to the gradient of the conformal factor τ , while the strength of the current is proportional to the beta function of the theory. In massive electrodynamics the SME remains valid, but the value of the induced current differs from the current generated in the system of massless fermions. In the present paper we use the Wigner-Weyl formalism to demonstrate that in accordance with the decoupling property of heavy fermions the corresponding anomalous conductivity vanishes in the large-mass limit with m2≫|e B | and m ≫|∇τ | .
Holon Wigner Crystal in a Lightly Doped Kagome Quantum Spin Liquid
Jiang, Hong-Chen; Devereaux, T.; Kivelson, S. A.
2017-08-01
We address the problem of a lightly doped spin liquid through a large-scale density-matrix renormalization group study of the t -J model on a kagome lattice with a small but nonzero concentration δ of doped holes. It is now widely accepted that the undoped (δ =0 ) spin-1 /2 Heisenberg antiferromagnet has a spin-liquid ground state. Theoretical arguments have been presented that light doping of such a spin liquid could give rise to a high temperature superconductor or an exotic topological Fermi liquid metal. Instead, we infer that the doped holes form an insulating charge-density wave state with one doped hole per unit cell, i.e., a Wigner crystal. Spin correlations remain short ranged, as in the spin-liquid parent state, from which we infer that the state is a crystal of spinless holons, rather than of holes. Our results may be relevant to kagome lattice herbertsmithite upon doping.
Partial Bell-State Analysis with Parametric down Conversion in the Wigner Function Formalism
Directory of Open Access Journals (Sweden)
A. Casado
2010-01-01
Full Text Available We apply the Wigner function formalism to partial Bell-state analysis using polarization entanglement produced in parametric down conversion. Two-photon statistics at a beam-splitter are reproduced by a wave-like description with zeropoint fluctuations of the electromagnetic field. In particular, the fermionic behaviour of two photons in the singlet state is explained from the invariance on the correlation properties of two light beams going through a balanced beam-splitter. Moreover, we show that a Bell-state measurement introduces some fundamental noise at the idle channels of the analyzers. As a consequence, the consideration of more independent sets of vacuum modes entering the crystal appears as a need for a complete Bell-state analysis.
Creation, Storage, and On-Demand Release of Optical Quantum States with a Negative Wigner Function
Directory of Open Access Journals (Sweden)
Jun-ichi Yoshikawa
2013-12-01
Full Text Available Highly nonclassical quantum states of light, characterized by Wigner functions with negative values, have been all-optically created so far only in a heralded fashion. In this case, the desired output emerges rarely and randomly from a quantum-state generator. An important example is the heralded production of high-purity single-photon states, typically based on some nonlinear optical interaction. In contrast, on-demand single-photon sources are also reported, exploiting the quantized level structure of matter systems. These sources, however, lead to highly impure output states, composed mostly of vacuum. While such impure states may still exhibit certain single-photon-like features such as antibunching, they are not nonclassical enough for advanced quantum-information processing. On the other hand, the intrinsic randomness of pure, heralded states can be circumvented by first storing and then releasing them on demand. Here, we propose such a controlled release, and we experimentally demonstrate it for heralded single photons. We employ two optical cavities, where the photons are both created and stored inside one cavity and finally released through a dynamical tuning of the other cavity. We demonstrate storage times of up to 300 ns while keeping the single-photon purity around 50% after storage. Our experiment is the first demonstration of a negative Wigner function at the output of an on-demand photon source or a quantum memory. In principle, our storage system is compatible with all kinds of nonclassical states, including those known to be essential for many advanced quantum-information protocols.
Beyond the continuum: a multi-dimensional phase space for neutral-niche community assembly.
Latombe, Guillaume; Hui, Cang; McGeoch, Melodie A
2015-12-22
Neutral and niche processes are generally considered to interact in natural communities along a continuum, exhibiting community patterns bounded by pure neutral and pure niche processes. The continuum concept uses niche separation, an attribute of the community, to test the hypothesis that communities are bounded by pure niche or pure neutral conditions. It does not accommodate interactions via feedback between processes and the environment. By contrast, we introduce the Community Assembly Phase Space (CAPS), a multi-dimensional space that uses community processes (such as dispersal and niche selection) to define the limiting neutral and niche conditions and to test the continuum hypothesis. We compare the outputs of modelled communities in a heterogeneous landscape, assembled by pure neutral, pure niche and composite processes. Differences in patterns under different combinations of processes in CAPS reveal hidden complexity in neutral-niche community dynamics. The neutral-niche continuum only holds for strong dispersal limitation and niche separation. For weaker dispersal limitation and niche separation, neutral and niche processes amplify each other via feedback with the environment. This generates patterns that lie well beyond those predicted by a continuum. Inferences drawn from patterns about community assembly processes can therefore be misguided when based on the continuum perspective. CAPS also demonstrates the complementary information value of different patterns for inferring community processes and captures the complexity of community assembly. It provides a general tool for studying the processes structuring communities and can be applied to address a range of questions in community and metacommunity ecology. © 2015 The Author(s).
Coupled bunch instability in Fermilab Booster: Longitudinal phase-space simulation
Energy Technology Data Exchange (ETDEWEB)
Bogacz, S.A.; Stahl, S.
1988-06-09
The physical presence of vacuum structures can be expressed in terms of a coupling impedance experienced by the beam. The beam environment considered here consist of parasitic higher order modes of the r.f. cavities. These resonances may have high enough Q's to allow consecutive bunches to interact through mutually induced fields. The cumulative effect of such fields as the particles pass through the cavity may be to induce a coherent buildup in synchrotron motion of the bunches, i.e., a longitudinal coupled-bunch instability. The colliding mode operation of the present generation of high energy synchrotrons and the accompanying r.f. manipulations, make considerations of individual bunch area of paramount importance. Thus, a longitudinal instability in one of a chain of accelerators, while not leading to any immediate reduction in the intensity of the beam in that accelerator, may cause such a reduction of beam quality that later operations are inhibited (resulting in a degradation performance). In this paper we employ a longitudinal phase-space tracking code (ESME) as an effective tool to simulate specific coupled bunch modes arising in a circular accelerator. One of the obvious advantages of the simulation compared to existing analytic formalisms, e.g., based on the Vlasov equation, is that it allows consideration of the instability in a self-consistent manner with respect to the changing accelerating conditions. Furthermore this scheme allows to model nonlinearities of the longitudinal beam dynamics, which are usually not tractable analytically. 5 refs., 3 figs.
An Overview of SBIR Phase 2 Physical Sciences and Biomedical Technologies in Space
Nguyen, Hung D.; Steele, Gynelle C.
2015-01-01
Technological innovation is the overall focus of NASA's Small Business Innovation Research (SBIR) program. The program invests in the development of innovative concepts and technologies to help NASA's mission directorates address critical research and development needs for agency projects. This report highlights innovative SBIR Phase II projects from 2007-2012 specifically addressing areas in physical sciences and biomedical technologies in space, which is one of six core competencies at NASA Glenn Research Center. There are twenty two technologies featured with emphasis on a wide spectrum of applications such as reusable handheld electrolyte, sensor for bone markers, wideband single crystal transducer, mini treadmill for musculoskeletal, and much more. Each article in this report describes an innovation, technical objective, and highlights NASA commercial and industrial applications. This report serves as an opportunity for NASA personnel including engineers, researchers, and program managers to learn of NASA SBIR's capabilities that might be crosscutting into this technology area. As the result, it would cause collaborations and partnerships between the small companies and NASA Programs and Projects resulting in benefit to both SBIR companies and NASA.
Zou, Longfang; Cryan, Martin; Klemm, Maciej
2014-10-06
The concept of phase change material (PCM) based optical antennas and antenna arrays is proposed for dynamic beam shaping and steering utilized in free-space optical inter/intra chip interconnects. The essence of this concept lies in the fact that the behaviour of PCM based optical antennas will change due to the different optical properties of the amorphous and crystalline state of the PCM. By engineering optical antennas or antenna arrays, it is feasible to design dynamic optical links in a desired manner. In order to illustrate this concept, a PCM based tunable reflectarray is proposed for a scenario of a dynamic optical link between a source and two receivers. The designed reflectarray is able to switch the optical link between two receivers by switching the two states of the PCM. Two types of antennas are employed in the proposed tunable reflectarray to achieve full control of the wavefront of the reflected beam. Numerical studies show the expected binary beam steering at the optical communication wavelength of 1.55 μm. This study suggests a new research area of PCM based optical antennas and antenna arrays for dynamic optical switching and routing.
Baker, D. N.; Jaynes, A. N.; Li, X.; Henderson, M. G.; Kanekal, S. G.; Reeves, G. D.; Spence, H. E.; Claudepierre, S. G.; Fennell, J. F.; Hudson, M. K.
2014-01-01
The dual-spacecraft Van Allen Probes mission has provided a new window into mega electron volt (MeV) particle dynamics in the Earth's radiation belts. Observations (up to E (is) approximately 10MeV) show clearly the behavior of the outer electron radiation belt at different timescales: months-long periods of gradual inward radial diffusive transport and weak loss being punctuated by dramatic flux changes driven by strong solar wind transient events. We present analysis of multi-MeV electron flux and phase space density (PSD) changes during March 2013 in the context of the first year of Van Allen Probes operation. This March period demonstrates the classic signatures both of inward radial diffusive energization and abrupt localized acceleration deep within the outer Van Allen zone (L (is) approximately 4.0 +/- 0.5). This reveals graphically that both 'competing' mechanisms of multi-MeV electron energization are at play in the radiation belts, often acting almost concurrently or at least in rapid succession.
Near equality of ion phase space densities at earth, Jupiter, and Saturn
Cheng, A. F.; Krimigis, S. M.; Armstrong, T. P.
1985-01-01
Energetic-ion phase-space density profiles are strikingly similar in the inner magnetospheres of earth, Jupiter, and Saturn for ions of first adiabatic invariant near 100 MeV/G and small mirror latitudes. Losses occur inside L approximately equal to 7 for Jupiter and Saturn and inside L approximately equal to 5 at earth. At these L values there exist steep plasma-density gradients at all three planets, associated with the Io plasma torus at Jupiter, the Rhea-Dione-Tethys torus at Saturn, and the plasmasphere at earth. Measurements of ion flux-tube contents at Jupiter and Saturn by the low-energy charged-particle experiment show that these are similar (for O ions at L = 5-9) to those at earth (for protons at L = 2-6). Furthermore, the thermal-ion flux-tube contents from Voyager plasma-science data at Jupiter and Saturn are also very nearly equal, and again similar to those at earth, differing by less than a factor of 3 at the respective L values. The near equality of energetic and thermal ion flux-tube contents at earth, Jupiter, and Saturn suggests the possibility of strong physical analogies in the interaction between plasma and energetic particles at the plasma tori/plasma sheets of Jupiter and Saturn and the plasmasphere of earth.
Qualitative phase space reconstruction analysis of supply-chain inventor time series
Directory of Open Access Journals (Sweden)
Jinliang Wu
2010-10-01
Full Text Available The economy systems are usually too complex to be analysed, but some advanced methods have been developed in order to do so, such as system dynamics modelling, multi-agent modelling, complex adaptive system modelling and qualitative modelling. In this paper, we considered a supply-chain (SC system including several kinds of products. Using historic suppliers’ demand data, we firstly applied the phase space analysis method and then used qualitative analysis to improve the complex system’s performance. Quantitative methods can forecast the quantitative SC demands, but they cannot indicate the qualitative aspects of SC, so when we apply quantitative methods to a SC system we get only numerous data of demand. By contrast, qualitative methods can show the qualitative change and trend of the SC demand. We therefore used qualitative methods to improve the quantitative forecasting results. Comparing the quantitative only method and the combined method used in this paper, we found that the combined method is far more accurate. Not only is the inventory cost lower, but the forecasting accuracy is also better.
Wigner’s phase-space function and atomic structure: II. Ground states for closed-shell atoms
DEFF Research Database (Denmark)
Springborg, Michael; Dahl, Jens Peder
1987-01-01
display and analyze the function for the closed-shell atoms helium, beryllium, neon, argon, and zinc in the Hartree-Fock approximation. The quantum-mechanical exact results are compared with those obtained with the approximate Thomas-Fermi description of electron densities in phase space....
Bowyer, J. M.
1977-01-01
The principal chemical species emitted and/or entrained by the rocket motors of the space shuttle vehicle during the launch phase of its trajectory are considered. Results are presented for two extreme trajectories, both of which were calculated in 1976.
Roman, Monsi C.; Mittelman, Marc W.
2010-01-01
This slide presentation summarizes the studies performed to assess the bulk phase microbial community during the Space Station Water Recover Tests (WRT) from 1990-1998. These tests show that it is possible to recycle water from different sources including urine, and produce water that can exceed the quality of municpally produced tap water.
Directory of Open Access Journals (Sweden)
H. Panahi
2017-01-01
Full Text Available We study the (2 + 1-dimensional Dirac oscillator in the noncommutative phase space and the energy eigenvalues and the corresponding wave functions of the system are obtained through the sl(2 algebraization. It is shown that the results are in good agreement with those obtained previously via a different method.
DEFF Research Database (Denmark)
Rasmussen, Tonny Wederberg
1999-01-01
The paper describes a full space vector control stradegy. The synchronisation used to improveboth the control speed of reactive power and reduce the sensitivity to large phase jumps in the grid caused by switching arge loads. The control stradegy is tested with a 5-level 10kvar laboratory model....
Yeh, Leehwa
1993-01-01
The phase-space-picture approach to quantum non-equilibrium statistical mechanics via the characteristic function of infinite-mode squeezed coherent states is introduced. We use quantum Brownian motion as an example to show how this approach provides an interesting geometrical interpretation of quantum non-equilibrium phenomena.
Pohner, John A.; Dempsey, Brian P.; Herold, Leroy M.
1990-01-01
Space Station elements and advanced military spacecraft will require rejection of tens of kilowatts of waste heat. Large space radiators and two-phase heat transport loops will be required. To minimize radiator size and weight, it is critical to minimize the temperature drop between the heat source and sink. Under an Air Force contract, a unique, high-performance heat exchanger is developed for coupling the radiator to the transport loop. Since fluid flow through the heat exchanger is driven by capillary forces which are easily dominated by gravity forces in ground testing, it is necessary to perform microgravity thermal testing to verify the design. This contract consists of an experiment definition phase leading to a preliminary design and cost estimate for a shuttle-based flight experiment of this heat exchanger design. This program will utilize modified hardware from a ground test program for the heat exchanger.
Wong, Sun; Del Genio, Anthony; Wang, Tao; Kahn, Brian; Fetzer, Eric J.; L'Ecuyer, Tristan S.
2015-01-01
Goals: Water budget-related dynamical phase space; Connect large-scale dynamical conditions to atmospheric water budget (including precipitation); Connect atmospheric water budget to cloud type distributions.
NIAC Phase I Study Final Report on Large Ultra-Lightweight Photonic Muscle Space Structures
Ritter, Joe
2016-01-01
The research goal is to develop new tools support NASA's mission of understanding of the Cosmos by developing cost effective solutions that yield a leap in performance and science data. 'Maikalani' in Hawaiian translates to, "knowledge we gain from the cosmos." Missions like Hubble have fundamentally changed humanity's view of the cosmos. Last year's Nobel prize in physics was a result of astronomical discoveries. $9B class JWST size (6.5 meter diameter) space telescopes, when launched are anticipated to rewrite our knowledge of physics. Here we report on a neoteric meta-material telescope mirror technology designed to enable a factor of 100 or more reduction in areal density, a factor of 100 reduction in telescope production and launch costs as well as other advantages; a leap to enable missions to image the cosmos in unprecedented detail, with the associated gain in knowledge. Whether terahertz, visible or X-ray, reflectors used for high quality electromagnetic imaging require shape accuracy (surface figure) to far better than 1 wavelength (lambda) of the incident photons, more typically lambda/10 or better. Imaging visible light therefore requires mirror surfaces that approximate a desired curve (e.g. a sphere or paraboloid) with smooth shape deviation of th less than approximately 1/1000 the diameter of a human hair. This requires either thick high modulus material like glass or metal, or actuators to control mirror shape. During Phase I our team studied a novel solution to this systems level design mass/shape tradespace requirement both to advance the innovative space technology concept and also to help NASA and other agencies meet current operational and future mission requirements. Extreme and revolutionary NASA imaging missions such as Terrestrial Planet Imager (TPI) require lightweight mirrors with minimum diameters of 20 to 40 meters. For reference, NASA's great achievement; the Hubble space telescope, is only 2.4 meters in diameter. What is required is a
Directory of Open Access Journals (Sweden)
Ronald C. Davidson
2002-08-01
Full Text Available The Vlasov-Maxwell equations are used to investigate the nonlinear evolution of an intense sheet beam with distribution function f_{b}\\(x,x^{′},s\\ propagating through a periodic focusing lattice κ_{x}\\(s+S\\=κ_{x}\\(s\\, where S=const is the lattice period. The analysis considers the special class of distribution functions with uniform phase-space density f_{b}\\(x,x^{′},s\\=A=const inside of the simply connected boundary curves, x_{+}^{′}\\(x,s\\ and x_{-}^{′}\\(x,s\\, in the two-dimensional phase space \\(x,x^{′}\\. Coupled nonlinear equations are derived describing the self-consistent evolution of the boundary curves, x_{+}^{′}\\(x,s\\ and x_{-}^{′}\\(x,s\\, and the self-field potential ψ\\(x,s\\=e_{b}φ\\(x,s\\/γ_{b}m_{b}β_{b}^{2}c^{2}. The resulting model is shown to be exactly equivalent to a (truncated warm-fluid description with zero heat flow and triple-adiabatic equation of state with scalar pressure P_{b}\\(x,s\\=const[n_{b}\\(x,s\\]^{3}. Such a fluid model is amenable to direct analysis by transforming to Lagrangian variables following the motion of a fluid element. Specific examples of periodically focused beam equilibria are presented, ranging from a finite-emittance beam in which the boundary curves in phase space \\(x,x^{′}\\ correspond to a pulsating parallelogram, to a cold beam in which the number density of beam particles, n_{b}\\(x,s\\, exhibits large-amplitude periodic oscillations. For the case of a sheet beam with uniform phase-space density, the present analysis clearly demonstrates the existence of periodically focused beam equilibria without the undesirable feature of an inverted population in phase space that is characteristic of the Kapchinskij-Vladimirskij beam distribution.
Renklioglu, B.; Yalabik, M. C.
2012-12-01
Phase transitions of the two-finite temperature Ising model on a square lattice are investigated by using a position space renormalization group (PSRG) transformation. Different finite temperatures, T x and T y , and also different time-scale constants, α x and α y for spin exchanges in the x and y directions define the dynamics of the non-equilibrium system. The critical surface of the system is determined by RG flows as a function of these exchange parameters. The Onsager critical point (when the two temperatures are equal) and the critical temperature for the limit when the other temperature is infinite, previously studied by the Monte Carlo method, are obtained. In addition, two steady-state fixed points which correspond to the non-equilibrium phase transition are presented. These fixed points yield the different universality class properties of the non-equilibrium phase transitions.
Experimental measurement of the 4-d transverse phase space map of a heavy ion beam
Energy Technology Data Exchange (ETDEWEB)
Hopkins, H S
1997-12-01
The development and employment of a new diagnostic instrument for characterizing intense, heavy ion beams is reported on. This instrument, the ''Gated Beam Imager'' or ''GBI'' was designed for use on Lawrence Livermore National Laboratory Heavy Ion Fusion Project's ''Small Recirculator'', an integrated, scaled physics experiment and engineering development project for studying the transport and control of intense heavy ion beams as inertial fusion drivers in the production of electric power. The GBI allows rapid measurement and calculation of a heavy ion beam's characteristics to include all the first and second moments of the transverse phase space distribution, transverse emittance, envelope parameters and beam centroid. The GBI, with appropriate gating produces a time history of the beam resulting in a 4-D phase-space and time ''map'' of the beam. A unique capability of the GBI over existing diagnostic instruments is its ability to measure the ''cross'' moments between the two transverse orthogonal directions. Non-zero ''cross'' moments in the alternating gradient lattice of the Small Recirculator are indicative of focusing element rotational misalignments contributing to beam emittance growth. This emittance growth, while having the same effect on the ability to focus a beam as emittance growth caused by non-linear effects, is in principle removable by an appropriate number of focusing elements. The instrument uses the pepperpot method of introducing a plate with many pinholes into the beam and observing the images of the resulting beamlets as they interact with a detector after an appropriate drift distance. In order to produce adequate optical signal and repeatability, the detector was chosen to be a microchannel plate (MCP) with a phosphor readout screen. The heavy ions in the pepperpot beamlets are stopped in the MCP's thin
On the identification of substructures in phase-space orbital frequencies
Gómez, Facundo A.; Helmi, Amina
2009-01-01
We study the evolution of satellite debris to establish the most suitable space to identify past merger events. We find that the space of orbital frequencies is very promising in this respect. In frequency space individual streams can be easily identified, and their separation provides a direct
On the identification of substructure in phase space using orbital frequencies
Gomez, Facundo A.; Helmi, Amina
2010-01-01
We study the evolution of satellite debris to establish the most suitable space to identify past merger events. We confirm that the space of orbital frequencies is very promising in this respect. In frequency space individual streams can be easily identified, and their separation provides a direct
On the apparent power law in CDM halo pseudo-phase space density profiles
Nadler, Ethan O.; Oh, S. Peng; Ji, Suoqing
2017-09-01
We investigate the apparent power-law scaling of the pseudo-phase space density (PPSD) in cold dark matter (CDM) haloes. We study fluid collapse, using the close analogy between the gas entropy and the PPSD in the fluid approximation. Our hydrodynamic calculations allow for a precise evaluation of logarithmic derivatives. For scale-free initial conditions, entropy is a power law in Lagrangian (mass) coordinates, but not in Eulerian (radial) coordinates. The deviation from a radial power law arises from incomplete hydrostatic equilibrium (HSE), linked to bulk inflow and mass accretion, and the convergence to the asymptotic central power-law slope is very slow. For more realistic collapse, entropy is not a power law with either radius or mass due to deviations from HSE and scale-dependent initial conditions. Instead, it is a slowly rolling power law that appears approximately linear on a log-log plot. Our fluid calculations recover PPSD power-law slopes and residual amplitudes similar to N-body simulations, indicating that deviations from a power law are not numerical artefacts. In addition, we find that realistic collapse is not self-similar; scalelengths such as the shock radius and the turnaround radius are not power-law functions of time. We therefore argue that the apparent power-law PPSD cannot be used to make detailed dynamical inferences or extrapolate halo profiles inwards, and that it does not indicate any hidden integrals of motion. We also suggest that the apparent agreement between the PPSD and the asymptotic Bertschinger slope is purely coincidental.
Chrysoulakis, Nektarios; Marconcini, Mattia; Gastellu-Etchegorry, Jean-Philippe; Grimmond, Sue; Feigenwinter, Christian; Lindberg, Fredrik; Del Frate, Fabio; Klostermann, Judith; Mitraka, Zina; Esch, Thomas; Landier, Lucas; Gabey, Andy; Parlow, Eberhard; Olofson, Frans
2017-04-01
The H2020-Space project URBANFLUXES (URBan ANthrpogenic heat FLUX from Earth observation Satellites) investigates the potential of Copernicus Sentinels to retrieve anthropogenic heat flux, as a key component of the Urban Energy Budget (UEB). URBANFLUXES advances the current knowledge of the impacts of UEB fluxes on urban heat island and consequently on energy consumption in cities. In URBANFLUXES, the anthropogenic heat flux is estimated as a residual of UEB. Therefore, the rest UEB components, namely, the net all-wave radiation, the net change in heat storage and the turbulent sensible and latent heat fluxes are independently estimated from Earth Observation (EO), whereas the advection term is included in the error of the anthropogenic heat flux estimation from the UEB closure. The Discrete Anisotropic Radiative Transfer (DART) model is employed to improve the estimation of the net all-wave radiation balance, whereas the Element Surface Temperature Method (ESTM), adjusted to satellite observations is used to improve the estimation the estimation of the net change in heat storage. Furthermore the estimation of the turbulent sensible and latent heat fluxes is based on the Aerodynamic Resistance Method (ARM). Based on these outcomes, QF is estimated by regressing the sum of the turbulent heat fluxes versus the available energy. In-situ flux measurements are used to evaluate URBANFLUXES outcomes, whereas uncertainties are specified and analyzed. URBANFLUXES is expected to prepare the ground for further innovative exploitation of EO in scientific activities (climate variability studies at local and regional scales) and future and emerging applications (sustainable urban planning, mitigation technologies) to benefit climate change mitigation/adaptation. This study presents the results of the second phase of the project and detailed information on URBANFLUXES is available at: http://urbanfluxes.eu
Magnetic field amplification in electron phase-space holes and related effects
Directory of Open Access Journals (Sweden)
R. A. Treumann
2012-04-01
Full Text Available Three-dimensional electron phase-space holes are shown to have positive charges on the plasma background, which produce a radial electric field and force the trapped electron component into an azimuthal drift. In this way electron holes generate magnetic fields in the hole. We solve the cylindrical hole model exactly for the hole charge, electric potential and magnetic field. In electron holes, the magnetic field is amplified on the flux tube of the hole; equivalently, in ion holes the field would be decreased. The flux tube adjacent to the electron hole is magnetically depleted by the external hole dipole field. This causes magnetic filamentation. It is also shown that holes are massive objects, each carrying a finite magnetic moment. Binary magnetic dipole interaction of these moments will cause alignment of the holes into chains along the magnetic field or, in the three-dimensional case, produce a magnetic fabric in the volume of hole formation. Since holes, in addition to being carriers of charges and magnetic moments, also have finite masses, they behave like quasi-particles, performing E × B, magnetic field, and diamagnetic drifts. In an inhomogeneous magnetic field, their magnetic moments experience torque, which causes nutation of the hole around the direction of the magnetic field, presumably giving rise to low frequency magnetic modulations like pulsations. A gas of many such holes may allow for a kinetic description, in which holes undergo binary dipole interactions. This resembles the polymeric behaviour. Both magnetic field generation and magnetic structure formation are of interest in auroral, solar coronal and shock physics, in particular in the problem of magnetic field filamentation in relativistic foreshocks and cosmic ray acceleration.
Iafrate, G. J.; Sokolov, V. N.; Krieger, J. B.
2017-10-01
The theory of Bloch electron dynamics for carriers in homogeneous electric and magnetic fields of arbitrary time dependence is developed in the framework of the Liouville equation. The Wigner distribution function (WDF) is determined from the single-particle density matrix in the ballistic regime, i.e., collision effects are excluded. In the theory, the single-particle transport equation is established with the electric field described in the vector potential gauge, and the magnetic field is treated in the symmetric gauge. No specific assumptions are made concerning the form of the initial distribution in momentum or configuration space. The general approach is to employ the accelerated Bloch state representation (ABR) as a basis so that the dependence upon the electric field, including multiband Zener tunneling, is treated exactly. Further, in the formulation of the WDF, we transform to a new set of variables so that the final WDF is gauge invariant and is expressed explicitly in terms of the position, kinetic momentum, and time. The methodology for developing the WDF is illustrated by deriving the exact WDF equation for free electrons in homogeneous electric and magnetic fields resulting in the same form as given by the collisionless Boltzmann transport equation (BTE). The methodology is then extended to the case of electrons described by an effective Hamiltonian corresponding to an arbitrary energy band function; the exact WDF equation results for the effective Hamiltonian case are shown to approximate the free electron results when taken to second order in the magnetic field. As a corollary, in these cases, it is shown that if the WDF is a wave packet, then the time rate of change of the electron quasimomentum is given by the Lorentz force. In treating the problem of Bloch electrons in a periodic potential in the presence of homogeneous electric and magnetic fields, the methodology for deriving the WDF reveals a multiband character due to the inherent nature of
Using Pre-Melted Phase Change Material to Keep Payloads in Space Warm for Hours without Power
Choi, Michael
2013-01-01
Adding phase change material (PCM) to a mission payload can maintain its temperature above the cold survival limit, without power, for several hours in space. For the International Space Station, PCM is melted by heaters just prior to the payload translation to the worksite when power is available. When power is cut off during the six-hour translation, the PCM releases its latent heat to make up the heat loss from the radiator(s) to space. For the interplanetary Probe, PCM is melted by heaters just prior to separation from the orbiter when power is available from the orbiter power system. After the Probe separates from the orbiter, the PCM releases its latent heat to make up the heat loss from the Probe exterior to space. Paraffin wax is a good PCM candidate.
Dolfo, Gilles
2016-01-01
When a discrete state is coupled to a continuum, the dynamics can be described either by the Weisskopf-Wigner exponential decay or by the Rabi oscillation, depending on the relative magnitudes of the continuum width and of the Rabi frequency. A continuous transition between these two regimes exists, as demonstrated in 1977 by C. Cohen-Tannoudji and P. Avan. Here, we describe a fully analogous transition in classical mechanics, by studying the dynamics of two coupled mechanical oscillators in the presence of damping. By varying the relative magnitudes of the damping and coupling terms, we observe a continuous transition between a regime analogous to the Rabi oscillation and a regime analogous to the Weisskopf-Wigner exponential decay.
DEFF Research Database (Denmark)
Padmanaban, Sanjeevi Kumar; Grandi, Gabriele; Ojo, Joseph Olorunfemi
2016-01-01
In this paper, a six-phase (asymmetrical) machine is investigated, 300 phase displacement is set between two three-phase stator windings keeping deliberately in open-end configuration. Power supply consists of four classical three-phase voltage inverters (VSIs), each one connected to the open......-winding terminals. An original synchronous field oriented control (FOC) algorithm with three variables as degree of freedom is proposed, allowing power sharing among the four VSIs in symmetric/asymmetric conditions. A standard three-level space vector pulse width modulation (SVPWM) by nearest three vector (NTV......) approach was adopted for each couple of VSIs to operate as multilevel output voltage generators. The proposed power sharing algorithm is verified for the ac drive system by observing the dynamic behaviours in different set conditions by complete simulation modelling in software (Matlab...
Shao, Yun; Yuan, Zongqiang; Ye, Difa; Fu, Libin; Liu, Ming-Ming; Sun, Xufei; Wu, Chengyin; Liu, Jie; Gong, Qihuang; Liu, Yunquan
2017-12-01
We measure the wavelength-dependent correlated-electron momentum (CEM) spectra of strong-field double ionization of Xe atoms, and observe a significant change from a roughly nonstructured (uncorrelated) pattern at 795 nm to an elongated distribution with V-shaped structure (correlated) at higher wavelengths of 1320 and 1810 nm, pointing to the transition of the ionization dynamics imprinted in the momentum distributions. These observations are well reproduced by a semiclassical model using Green–Sellin–Zachor potential to take into account the screening effect. We show that the momentum distribution of Xe2+ undergoes a bifurcation structure emerging from single-hump to double-hump structure as the laser wavelength increases, which is dramatically different from that of He2+, indicating the complex multi-electron effect. By back analyzing the double ionization trajectories in the phase space (the initial transverse momentum and the laser phase at the tunneling exit) of the first tunneled electrons, we provide deep insight into the physical origin for electron correlation dynamics. We find that a random distribution in phase-space is responsible for a less distinct structured CEM spectrum at shorter wavelength. While increasing the laser wavelength, a topology-invariant pattern in phase-space appears, leading to the clearly visible V-shaped structures.
Bencheikh, K.; Nieto, L. M.; Maamache, M.
2005-09-01
Using the Wigner transform, we present an alternative derivation of the partial differential equation satisfied by the Slater sum, which is the diagonal element of the canonical Bloch density matrix. This is done in one dimension for the case of a general confining potential and also for the case of N independent fermions harmonically confined in d dimensions. We also present a simple proof of the so-called differential virial theorem for each of these cases.
Energy Technology Data Exchange (ETDEWEB)
Bishop, R.F. (Manchester Univ. (United Kingdom). Inst. of Science and Technology); Buendia, E. (Granada Univ. (Spain). Dept. de Fisica Moderna); Flynn, M.F. (Kent State Univ., OH (United States). Dept. of Physics); Guardiola, R. (Valencia Univ. (Spain). Dept. de Fisica Atomica y Nuclear)
1992-02-01
The diffusion Monte Carlo method is used to integrate the four-body Schroedinger equation corresponding to the {sup 4}He nucleus for several model potentials of Wigner type. Good importance sampling trial functions are used, and the sampling is large enough to obtain the ground-state energy with an error of only 0.01 to 0.02 MeV. (author).
Application of radio phase modes to modification and remote sensing of the atmosphere and space
Isham, B.; Mohammadi, S.; Chau, J.; Hysell, D. L.; Daldorff, L. K.; Thide, B.; Bergman, J.
2009-12-01
Radio phase modes are a low-frequency electromagnetic wave (radio) manifestation of photon orbital angular momentum (OAM) modes. At optical (laser) wavelengths OAM is an active area of theoretical and experimental research. Theory and modelling of radio phase modes show they may also easily be generated and, under certain conditions, detected with modern radio antenna arrays. Transimission of radio phase modes has been attempted using the HAARP HF transmitter in Alaska and the Jicamarca VHF radar in Peru. The HAARP experiment was designed to search for ionospheric modification effects of phase modes, while the Jicamarca experiment explored the possibility of using phase modes for remote sensing. Further work at Jicamarca will be aimed at verifying phase mode transmission and detection capabilities by using the moon as a reflector. Other potential applications of phase modes include the detection of radio OAM generated by astrophysical sources and their use in communications as a way of transmitting multiple signals at a single frequency.
Eisner, M. (Editor)
1975-01-01
The importance of zero gravity environment in the development and production of new and improved materials is considered along with the gravitational effects on phase changes or critical behavior in a variety of materials. Specific experiments discussed include: fine scale phase separation in zero gravity; glass formation in zero gravity; effects of gravitational perturbations on determination of critical exponents; and light scattering from long wave fluctuations in liquids in zero gravity. It is concluded that the space shuttle/spacelab system is applicable to various fields of interest.
Ollendorf, S.; Fowle, A.; Almgren, D.
1981-01-01
A system utilizing a pumped, two-phase single component working fluid for heat exchange and transport services necessary to meet the temperature control requirements of typical orbiting instrument payloads on space platforms is described. The design characteristics of the system is presented, together with a presentation of a laboratory apparatus for demonstration of proof of concept. Results indicate that the pumped two-phase design concept can meet a wide range of thermal performance requirements with the only penalty being the requirement for a small liquid pump.
Real-space and reciprocal-space Berry phases in the Hall effect of Mn(1-x)Fe(x)Si.
Franz, C; Freimuth, F; Bauer, A; Ritz, R; Schnarr, C; Duvinage, C; Adams, T; Blügel, S; Rosch, A; Mokrousov, Y; Pfleiderer, C
2014-05-09
We report an experimental and computational study of the Hall effect in Mn(1-x)Fe(x)Si, as complemented by measurements in Mn(1-x)Co(x)Si, when helimagnetic order is suppressed under substitutional doping. For small x the anomalous Hall effect (AHE) and the topological Hall effect (THE) change sign. Under larger doping the AHE remains small and consistent with the magnetization, while the THE grows by over a factor of 10. Both the sign and the magnitude of the AHE and the THE are in excellent agreement with calculations based on density functional theory. Our study provides the long-sought material-specific microscopic justification that, while the AHE is due to the reciprocal-space Berry curvature, the THE originates in real-space Berry phases.
Analytical description of photon beam phase spaces in inverse Compton scattering sources
Curatolo, C.; Drebot, I.; Petrillo, V.; Serafini, L.
2017-08-01
We revisit the description of inverse Compton scattering sources and the photon beams generated therein, emphasizing the behavior of their phase space density distributions and how they depend upon those of the two colliding beams of electrons and photons. The main objective is to provide practical formulas for bandwidth, spectral density, brilliance, which are valid in general for any value of the recoil factor, i.e. both in the Thomson regime of negligible electron recoil, and in the deep Compton recoil dominated region, which is of interest for gamma-gamma colliders and Compton sources for the production of multi-GeV photon beams. We adopt a description based on the center of mass reference system of the electron-photon collision, in order to underline the role of the electron recoil and how it controls the relativistic Doppler/boost effect in various regimes. Using the center of mass reference frame greatly simplifies the treatment, allowing us to derive simple formulas expressed in terms of rms momenta of the two colliding beams (emittance, energy spread, etc.) and the collimation angle in the laboratory system. Comparisons with Monte Carlo simulations of inverse Compton scattering in various scenarios are presented, showing very good agreement with the analytical formulas: in particular we find that the bandwidth dependence on the electron beam emittance, of paramount importance in Thomson regime, as it limits the amount of focusing imparted to the electron beam, becomes much less sensitive in deep Compton regime, allowing a stronger focusing of the electron beam to enhance luminosity without loss of mono-chromaticity. A similar effect occurs concerning the bandwidth dependence on the frequency spread of the incident photons: in deep recoil regime the bandwidth comes out to be much less dependent on the frequency spread. The set of formulas here derived are very helpful in designing inverse Compton sources in diverse regimes, giving a quite accurate first
Analytical description of photon beam phase spaces in inverse Compton scattering sources
Directory of Open Access Journals (Sweden)
C. Curatolo
2017-08-01
Full Text Available We revisit the description of inverse Compton scattering sources and the photon beams generated therein, emphasizing the behavior of their phase space density distributions and how they depend upon those of the two colliding beams of electrons and photons. The main objective is to provide practical formulas for bandwidth, spectral density, brilliance, which are valid in general for any value of the recoil factor, i.e. both in the Thomson regime of negligible electron recoil, and in the deep Compton recoil dominated region, which is of interest for gamma-gamma colliders and Compton sources for the production of multi-GeV photon beams. We adopt a description based on the center of mass reference system of the electron-photon collision, in order to underline the role of the electron recoil and how it controls the relativistic Doppler/boost effect in various regimes. Using the center of mass reference frame greatly simplifies the treatment, allowing us to derive simple formulas expressed in terms of rms momenta of the two colliding beams (emittance, energy spread, etc. and the collimation angle in the laboratory system. Comparisons with Monte Carlo simulations of inverse Compton scattering in various scenarios are presented, showing very good agreement with the analytical formulas: in particular we find that the bandwidth dependence on the electron beam emittance, of paramount importance in Thomson regime, as it limits the amount of focusing imparted to the electron beam, becomes much less sensitive in deep Compton regime, allowing a stronger focusing of the electron beam to enhance luminosity without loss of mono-chromaticity. A similar effect occurs concerning the bandwidth dependence on the frequency spread of the incident photons: in deep recoil regime the bandwidth comes out to be much less dependent on the frequency spread. The set of formulas here derived are very helpful in designing inverse Compton sources in diverse regimes, giving a
Directory of Open Access Journals (Sweden)
Qisheng Yan
2014-01-01
Full Text Available A hybrid forecasting approach combining empirical mode decomposition (EMD, phase space reconstruction (PSR, and extreme learning machine (ELM for international uranium resource prices is proposed. In the first stage, the original uranium resource price series are first decomposed into a finite number of independent intrinsic mode functions (IMFs, with different frequencies. In the second stage, the IMFs are composed into three subseries based on the fine-to-coarse reconstruction rule. In the third stage, based on phase space reconstruction, different ELM models are used to model and forecast the three subseries, respectively, according to the intrinsic characteristic time scales. Finally, in the foruth stage, these forecasting results are combined to output the ultimate forecasting result. Experimental results from real uranium resource price data demonstrate that the proposed hybrid forecasting method outperforms RBF neural network (RBFNN and single ELM in terms of RMSE, MAE, and DS.
Multi-turn extraction and injection by means of adiabatic capture in stable islands of phase space
Cappi, R
2003-01-01
Recently a novel approach has been proposed aimed at performing multi-turn extraction from a circular machine. Such a technique consists of splitting the beam by means of stable islands created in transverse phase space by magnetic elements creating nonlinear fields, such as sextupoles and octupoles. Provided a slow time-variation of the linear tune is applied, adiabatic with respect to the betatron motion, the islands can be moved in phase space and eventually charged particles may be trapped inside the stable structures. This generates a certain number of well-separated beamlets. Originally, this principle was successfully tested using a fourth-order resonance. In this paper the approach is generalised by considering other type of resonances as well as the possibility of performing multiple multi-turn extractions. The results of numerical simulations are presented and described in detail. Of course, by time-reversal, the proposed approach could be used also for multi-turn injection.
Measuring the W-Boson mass at a hadron collider: a study of phase-space singularity methods
De Rújula, A
2011-01-01
The traditional method to measure the W-Boson mass at a hadron collider (more precisely, its ratio to the Z-mass) utilizes the distributions of three variables in events where the W decays into an electron or a muon: the charged-lepton transverse momentum, the missing transverse energy and the transverse mass of the lepton pair. We study the putative advantages of the additional measurement of a fourth variable: an improved phase-space singularity mass. This variable is statistically optimal, and simultaneously exploits the longitudinal- and transverse-momentum distributions of the charged lepton. Though the process we discuss is one of the simplest realistic ones involving just one unobservable particle, it is fairly non-trivial and constitutes a good "training" example for the scrutiny of phenomena involving invisible objects. Our graphical analysis of the phase space is akin to that of a Dalitz plot, extended to such processes.
Phase-space holes due to electron and ion beams accelerated by a current-driven potential ramp
Directory of Open Access Journals (Sweden)
M. V. Goldman
2003-01-01
Full Text Available One-dimensional open-boundary simulations have been carried out in a current-carrying plasma seeded with a neutral density depression and with no initial electric field. These simulations show the development of a variety of nonlinear localized electric field structures: double layers (unipolar localized fields, fast electron phase-space holes (bipolar fields moving in the direction of electrons accelerated by the double layer and trains of slow alternating electron and ion phase-space holes (wave-like fields moving in the direction of ions accelerated by the double layer. The principal new result in this paper is to show by means of a linear stability analysis that the slow-moving trains of electron and ion holes are likely to be the result of saturation via trapping of a kinetic-Buneman instability driven by the interaction of accelerated ions with unaccelerated electrons.
Near-field scanning magneto-optical spectroscopy of Wigner molecules
Energy Technology Data Exchange (ETDEWEB)
Mintairov, A. M., E-mail: amintair@nd.edu; Rouvimov, S. [University of Notre Dame, Notre Dame, IN 46556 (United States); Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Saint Petersburg, 194021 (Russian Federation); Kapaldo, J. [University of Notre Dame, Notre Dame, IN 46556 (United States); Merz, J. L.; Kalyygniy, N.; Mintairov, S. A.; Nekrasov, S.; Saly, R.; Vlasov, A. S. [Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Saint Petersburg, 194021 (Russian Federation); Blundell, S. [SPSMS, UMR-E CEA/UJF-Grenoble 1, INAC, Grenoble, FR-38054 (France)
2016-06-17
We study the emission spectra of single self-organized InP/GaInP QDs (size 100-220 nm) using high-spatial-resolution, low-temperature (5 K) near-field scanning optical microscope (NSOM) operating at magnetic field strength B=0-10 T. The dots contain up to twenty electrons and represent natural Wigner molecules (WM). We observed vibronic-type shake-up structure in single electron QDs manifesting formation of two electron (2e) WM in photo-excited state. We found that relative intensities of the shake-up components described well by vibronic Frank-Condon factors giving for dots having parabolic confinement energy ħω{sub 0}=1.2-4 meV molecule bond lengths 40-140 nm. We used measurements of magnetic-field-induced shifts to distinguish emission of 2e-WM and singly charged exciton (trion). We also observed magnetic-field-induced molecular-droplet transition for two electron dot, emitting through doubly charge exciton (tetron) at zero magnetic field.
Semiclassical Wigner theory of photodissociation in three dimensions: Shedding light on its basis
Energy Technology Data Exchange (ETDEWEB)
Arbelo-González, W. [Max Planck Institut für Kohlenforschung, Mülheim an der Ruhr (Germany); CNRS, Institut des Sciences Moléculaires, UMR 5255, 33405 Talence (France); Université Bordeaux, Institut des Sciences Moléculaires, UMR 5255, 33405 Talence (France); Bonnet, L., E-mail: claude-laurent.bonnet@u-bordeaux.fr [CNRS, Institut des Sciences Moléculaires, UMR 5255, 33405 Talence (France); Université Bordeaux, Institut des Sciences Moléculaires, UMR 5255, 33405 Talence (France); García-Vela, A. [Instituto de Física Fundamental, C.S.I.C., Serrano 123, 28006 Madrid (Spain)
2015-04-07
The semiclassical Wigner theory (SCWT) of photodissociation dynamics, initially proposed by Brown and Heller [J. Chem. Phys. 75, 186 (1981)] in order to describe state distributions in the products of direct collinear photodissociations, was recently extended to realistic three-dimensional triatomic processes of the same type [Arbelo-González et al., Phys. Chem. Chem. Phys. 15, 9994 (2013)]. The resulting approach, which takes into account rotational motions in addition to vibrational and translational ones, was applied to a triatomic-like model of methyl iodide photodissociation and its predictions were found to be in nearly quantitative agreement with rigorous quantum results, but at a much lower computational cost, making thereby SCWT a potential tool for the study of polyatomic reaction dynamics. Here, we analyse the main reasons for this agreement by means of an elementary model of fragmentation explicitly dealing with the rotational motion only. We show that our formulation of SCWT makes it a semiclassical approximation to an approximate planar quantum treatment of the dynamics, both of sufficient quality for the whole treatment to be satisfying.
Lee, Joon-Ho; Jeong, Woo Jin; Seo, Junbeom; Shin, Mincheol
2018-01-01
Gate-all-around silicon nanowire transistors (SNWTs) are recognized as promising candidates to reduce problems due to quantum effects in conventional nano-transistors. In this study we investigate whether structural modification of SNWTs leads to improved performance. A model calculation for a transistor with a channel length of several nanometers requires a quantum transport simulator, and we use a Wigner transport equation (WTE) discretized by a third-order upwind differential scheme (TDS) suggested by Yamada et al. (2009) for quantum transport simulations of gate-all-around silicon-shell nanowire transistors (SSNWTs), core gate SSNWTs (CG-SSNWTs), and independent CG-SSNWTs (ICG-SSNWTs). A WTE discretized by the TDS is known to produce highly accurate results. The SSNWT has a structure in which an insulator cylinder is inserted into the center axis of the SNWT, and the CG-SSNWT has a structure in which a core gate is inserted into the center axis of the SSNWT. The calculations show that the performances of the SSNWTs are improved by introducing the Si-shell structure and the core gate. The ICG-SSNWTs are identical in structure to the CG-SSNWTs, but the outer and core gates are independently biased. The calculations for the ICG-SSNWTs show that the threshold voltage can be controlled using the difference between the core and outer gate voltages.
Energy Technology Data Exchange (ETDEWEB)
Jahnel, Benedikt, E-mail: Benedikt.Jahnel@ruhr-uni-bochum.de; Külske, Christof, E-mail: Christof.Kuelske@ruhr-uni-bochum.de [Ruhr-Universität Bochum, Fakultät für Mathematik (Germany); Botirov, Golibjon I., E-mail: botirovg@yandex.ru [Bukhara State University, Faculty of Physics and Mathematics (Uzbekistan)
2014-12-15
We consider a ferromagnetic nearest-neighbor model on a Cayley tree of degree k2 with uncountable local state space [0,1] where the energy function depends on a parameter θ ∊[0, 1). We show that for 0θ(5/(3k)) the model has a unique translation-invariant Gibbs measure. If 5/(3k) <θ < 1, there is a phase transition, in particular there are three translation-invariant Gibbs measures.
Townson, Reid W.; Zavgorodni, Sergei
2014-12-01
In GPU-based Monte Carlo simulations for radiotherapy dose calculation, source modelling from a phase-space source can be an efficiency bottleneck. Previously, this has been addressed using phase-space-let (PSL) sources, which provided significant efficiency enhancement. We propose that additional speed-up can be achieved through the use of a hybrid primary photon point source model combined with a secondary PSL source. A novel phase-space derived and histogram-based implementation of this model has been integrated into gDPM v3.0. Additionally, a simple method for approximately deriving target photon source characteristics from a phase-space that does not contain inheritable particle history variables (LATCH) has been demonstrated to succeed in selecting over 99% of the true target photons with only ~0.3% contamination (for a Varian 21EX 18 MV machine). The hybrid source model was tested using an array of open fields for various Varian 21EX and TrueBeam energies, and all cases achieved greater than 97% chi-test agreement (the mean was 99%) above the 2% isodose with 1% / 1 mm criteria. The root mean square deviations (RMSDs) were less than 1%, with a mean of 0.5%, and the source generation time was 4-5 times faster. A seven-field intensity modulated radiation therapy patient treatment achieved 95% chi-test agreement above the 10% isodose with 1% / 1 mm criteria, 99.8% for 2% / 2 mm, a RMSD of 0.8%, and source generation speed-up factor of 2.5. Presented as part of the International Workshop on Monte Carlo Techniques in Medical Physics
Safie, Fayssal M.
1992-01-01
This paper presents a reliability evaluation process designed to improve the reliability of advanced launch systems. The work performed includes the development of a reliability prediction methodology to be used in the design phase of the Space Transportation Main Engine (STME). This includes prediction techniques which use historical data bases as well as deterministic and probabilistic engineering models for predicting design reliability. In summary, this paper describes a probabilistic design approach for the next-generation liquid rocket engine, the STME.
Space Vector Pulse Width Modulation Strategy for Single-Phase Three-Level CIC T-source Inverter
DEFF Research Database (Denmark)
Shults, Tatiana E.; Husev, Oleksandr O.; Blaabjerg, Frede
2016-01-01
This paper presents a novel space vector pulse-width modulation strategy for a single-phase three-level buck-boost inverter based on an impedance-source network. The case study system is based on T-source inverter with continuous input current. To demonstrate the improved performance...... of the inverter, the strategy was compared the traditional pulse-width modulation. It is shown that the approach proposed has fewer switching states and does not suffer from neutral point misbalance....
Gerber, C. R.
1972-01-01
The development of uniform computer program standards and conventions for the modular space station is discussed. The accomplishments analyzed are: (1) development of computer program specification hierarchy, (2) definition of computer program development plan, and (3) recommendations for utilization of all operating on-board space station related data processing facilities.