WorldWideScience

Sample records for stable ground states

  1. Soluble and stable heptazethrenebis(dicarboximide) with a singlet open-shell ground state

    KAUST Repository

    Sun, Zhe; Huang, Kuo-Wei; Wu, Jishan

    2011-01-01

    A soluble and stable heptazethrene derivative was synthesized and characterized for the first time. This molecule exhibits a singlet biradical character in the ground state, which is the first case among zethrene homologue series. Exceptional stability of this heptazethrenebis(dicarboximide) raises the likelihood of its practical applications in materials science. © 2011 American Chemical Society.

  2. Soluble and stable heptazethrenebis(dicarboximide) with a singlet open-shell ground state

    KAUST Repository

    Sun, Zhe

    2011-08-10

    A soluble and stable heptazethrene derivative was synthesized and characterized for the first time. This molecule exhibits a singlet biradical character in the ground state, which is the first case among zethrene homologue series. Exceptional stability of this heptazethrenebis(dicarboximide) raises the likelihood of its practical applications in materials science. © 2011 American Chemical Society.

  3. Stable π-Extended p -Quinodimethanes: Synthesis and Tunable Ground States

    KAUST Repository

    Zeng, Zebing

    2014-12-18

    © 2014 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. p-Quinodimethane (p-QDM) is a highly reactive hydrocarbon showing large biradical character in the ground state. It has been demonstrated that incorporation of the p-QDM moiety into an aromatic hydrocarbon framework could lead to new π-conjugated systems with significant biradical character and unique optical, electronic and magnetic properties. On the other hand, the extension of p-QDM is expected to result in molecules with even larger biradical character and higher reactivity. Therefore, the synthesis of stable π-extended p-QDMs is very challenging. In this Personal Account we will briefly discuss different stabilizing strategies and synthetic methods towards stable π-extended p-QDMs with tunable ground states and physical properties, including two types of polycyclic hydrocarbons: (1) tetrabenzo-Tschitschibabin\\'s hydrocarbons, and (2) tetracyano-rylenequinodimethanes. We will discuss how the aromaticity, substituents and steric hindrance play important roles in determining their ground states and properties. Incorporation of the p-quinodimethane moiety into aromatic hydrocarbon frameworks can lead to new π-conjugated systems with significant biradical character and unique optical, electronic and magnetic properties. Furthermore, the extension of p-QDM is expected to result in molecules with even larger biradical character and higher reactivity. In this Personal Account, different stabilizing strategies and synthetic methods towards stable π-extended p-QDMs with tunable ground states and physical properties are briefly discussed, including the roles of aromaticity, substituents and steric hindrance.

  4. Self-similar decay to the marginally stable ground state in a model for film flow over inclined wavy bottoms

    Directory of Open Access Journals (Sweden)

    Tobias Hacker

    2012-04-01

    Full Text Available The integral boundary layer system (IBL with spatially periodic coefficients arises as a long wave approximation for the flow of a viscous incompressible fluid down a wavy inclined plane. The Nusselt-like stationary solution of the IBL is linearly at best marginally stable; i.e., it has essential spectrum at least up to the imaginary axis. Nevertheless, in this stable case we show that localized perturbations of the ground state decay in a self-similar way. The proof uses the renormalization group method in Bloch variables and the fact that in the stable case the Burgers equation is the amplitude equation for long waves of small amplitude in the IBL. It is the first time that such a proof is given for a quasilinear PDE with spatially periodic coefficients.

  5. Realization of Multi-Stable Ground States in a Nematic Liquid Crystal by Surface and Electric Field Modification

    Science.gov (United States)

    Gwag, Jin Seog; Kim, Young-Ki; Lee, Chang Hoon; Kim, Jae-Hoon

    2015-06-01

    Owing to the significant price drop of liquid crystal displays (LCDs) and the efforts to save natural resources, LCDs are even replacing paper to display static images such as price tags and advertising boards. Because of a growing market demand on such devices, the LCD that can be of numerous surface alignments of directors as its ground state, the so-called multi-stable LCD, comes into the limelight due to the great potential for low power consumption. However, the multi-stable LCD with industrial feasibility has not yet been successfully performed. In this paper, we propose a simple and novel configuration for the multi-stable LCD. We demonstrate experimentally and theoretically that a battery of stable surface alignments can be achieved by the field-induced surface dragging effect on an aligning layer with a weak surface anchoring. The simplicity and stability of the proposed system suggest that it is suitable for the multi-stable LCDs to display static images with low power consumption and thus opens applications in various fields.

  6. Stable π-Extended p -Quinodimethanes: Synthesis and Tunable Ground States

    KAUST Repository

    Zeng, Zebing; Wu, Jishan

    2014-01-01

    in molecules with even larger biradical character and higher reactivity. Therefore, the synthesis of stable π-extended p-QDMs is very challenging. In this Personal Account we will briefly discuss different stabilizing strategies and synthetic methods towards

  7. Kinetically blocked stable heptazethrene and octazethrene: Closed-shell or open-shell in the ground state?

    KAUST Repository

    Li, Yuan

    2012-09-12

    Polycyclic aromatic hydrocarbons with an open-shell singlet biradical ground state are of fundamental interest and have potential applications in materials science. However, the inherent high reactivity makes their synthesis and characterization very challenging. In this work, a convenient synthetic route was developed to synthesize two kinetically blocked heptazethrene (HZ-TIPS) and octazethrene (OZ-TIPS) compounds with good stability. Their ground-state electronic structures were systematically investigated by a combination of different experimental methods, including steady-state and transient absorption spectroscopy, variable temperature NMR, electron spin resonance (ESR), superconducting quantum interfering device (SQUID), FT Raman, and X-ray crystallographic analysis, assisted by unrestricted symmetry-broken density functional theory (DFT) calculations. All these demonstrated that the heptazethrene derivative HZ-TIPS has a closed-shell ground state while its octazethrene analogue OZ-TIPS with a smaller energy gap exists as an open-shell singlet biradical with a large measured biradical character (y = 0.56). Large two-photon absorption (TPA) cross sections (σ(2)) were determined for HZ-TIPS (σ(2)max = 920 GM at 1250 nm) and OZ-TIPS (σ(2)max = 1200 GM at 1250 nm). In addition, HZ-TIPS and OZ-TIPS show a closely stacked 1D polymer chain in single crystals. © 2012 American Chemical Society.

  8. Stable tetrabenzo-Chichibabin's hydrocarbons: Tunable ground state and unusual transition between their closed-shell and open-shell resonance forms

    KAUST Repository

    Zeng, Zebing

    2012-09-05

    Stable open-shell polycyclic aromatic hydrocarbons (PAHs) are of fundamental interest due to their unique electronic, optical, and magnetic properties and promising applications in materials sciences. Chichibabin\\'s hydrocarbon as a classical open-shell PAH has been investigated for a long time. However, most of the studies are complicated by their inherent high reactivity. In this work, two new stable benzannulated Chichibabin\\'s hydrocarbons 1-CS and 2-OS were prepared, and their electronic structure and geometry in the ground state were studied by various experiments (steady-state and transient absorption spectra, NMR, electron spin resonance (ESR), superconducting quantum interference device (SQUID), FT Raman, X-ray crystallographic etc.) and density function theory (DFT) calculations. 1-CS and 2-OS exhibited tunable ground states, with a closed-shell quinoidal structure for 1-CS and an open-shell biradical form for 2-OS. Their corresponding excited-state forms 1-OS and 2-CS were also chemically approached and showed different decay processes. The biradical 1-OS displayed an unusually slow decay to the ground state (1-CS) due to a large energy barrier (95 ± 2.5 kJ/mol) arising from severe steric hindrance during the transition from an orthogonal biradical form to a butterfly-like quinoidal form. The quick transition from the quinoidal 2-CS (excited state) to the orthogonal biradicaloid 2-OS (ground state) happened during the attempted synthesis of 2-CS. Compounds 1-CS and 2-OS can be oxidized into stable dications by FeCl 3 and/or concentrated H 2SO 4. The open-shell 2-OS also exhibited a large two-photon absorption (TPA) cross section (760 GM at 1200 nm). © 2012 American Chemical Society.

  9. Kinetically blocked stable heptazethrene and octazethrene: Closed-shell or open-shell in the ground state?

    KAUST Repository

    Li, Yuan; Heng, WeeKuan; Lee, Byungsun; Aratani, Naoki; Zafra, José Luis; Bao, Nina; Lee, Richmond; Sung, Youngmo; Sun, Zhe; Huang, Kuo-Wei; Webster, Richard D.; Lõ pez Navarrete, Juan Teodomiro; Kim, Dongho; Osuka, Atsuhiro; Casado, Juan; Ding, Jun; Wu, Jishan

    2012-01-01

    systematically investigated by a combination of different experimental methods, including steady-state and transient absorption spectroscopy, variable temperature NMR, electron spin resonance (ESR), superconducting quantum interfering device (SQUID), FT Raman

  10. Graphene ground states

    Science.gov (United States)

    Friedrich, Manuel; Stefanelli, Ulisse

    2018-06-01

    Graphene is locally two-dimensional but not flat. Nanoscale ripples appear in suspended samples and rolling up often occurs when boundaries are not fixed. We address this variety of graphene geometries by classifying all ground-state deformations of the hexagonal lattice with respect to configurational energies including two- and three-body terms. As a consequence, we prove that all ground-state deformations are either periodic in one direction, as in the case of ripples, or rolled up, as in the case of nanotubes.

  11. Nuclear ground state

    International Nuclear Information System (INIS)

    Negele, J.W.

    1975-01-01

    The nuclear ground state is surveyed theoretically, and specific suggestions are given on how to critically test the theory experimentally. Detailed results on 208 Pb are discussed, isolating several features of the charge density distributions. Analyses of 208 Pb electron scattering and muonic data are also considered. 14 figures

  12. Singlet Ground State Magnetism:

    DEFF Research Database (Denmark)

    Loidl, A.; Knorr, K.; Kjems, Jørgen

    1979-01-01

    The magneticGamma 1 –Gamma 4 exciton of the singlet ground state system TbP has been studied by inelastic neutron scattering above the antiferromagnetic ordering temperature. Considerable dispersion and a pronounced splitting was found in the [100] and [110] directions. Both the band width...

  13. Crystalline beam ground state

    International Nuclear Information System (INIS)

    Wei, Jie; Li, Xiao-Ping; Sessler, A.M.

    1993-01-01

    In order to employ Molecular Dynamics method, commonly used in condensed matter physics, we have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. We include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations has been performed to obtain the equilibrium structure. The effects of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time-dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Rahman and Schiffer, depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing

  14. Crystalline beam ground state

    International Nuclear Information System (INIS)

    Wei, Jie; Li, Xiao-Ping

    1993-01-01

    In order to employ molecular dynamics (MD) methods, commonly used in condensed matter physics, we have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. We include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations using MD methods has been performed to obtain the equilibrium crystalline beam structure. The effect of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Schiffer et al. depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing

  15. Crystalline beam ground state

    International Nuclear Information System (INIS)

    Wei, J.; Li, X.P.

    1993-01-01

    In order to employ the Molecular Dynamics method, commonly used in condensed matter physics, the authors have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. They include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations has been performed to obtain the equilibrium structure. The effects of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time-dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Rahman and Schiffer, depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing

  16. Stable States of Biological Organisms

    Science.gov (United States)

    Yukalov, V. I.; Sornette, D.; Yukalova, E. P.; Henry, J.-Y.; Cobb, J. P.

    2009-04-01

    A novel model of biological organisms is advanced, treating an organism as a self-consistent system subject to a pathogen flux. The principal novelty of the model is that it describes not some parts, but a biological organism as a whole. The organism is modeled by a five-dimensional dynamical system. The organism homeostasis is described by the evolution equations for five interacting components: healthy cells, ill cells, innate immune cells, specific immune cells, and pathogens. The stability analysis demonstrates that, in a wide domain of the parameter space, the system exhibits robust structural stability. There always exist four stable stationary solutions characterizing four qualitatively differing states of the organism: alive state, boundary state, critical state, and dead state.

  17. Stable tetrabenzo-Chichibabin's hydrocarbons: Tunable ground state and unusual transition between their closed-shell and open-shell resonance forms

    KAUST Repository

    Zeng, Zebing; Sung, Youngmo; Bao, Nina; Tan, Davin; Lee, Richmond; Zafra, José Luis; Lee, Byungsun; Ishida, Masatoshi; Ding, Jun; Lõ pez Navarrete, Juan Teodomiro; Li, Yuan; Zeng, Wangdong; Kim, Dongho; Huang, Kuo-Wei; Webster, Richard D.; Casado, Juan; Wu, Jishan

    2012-01-01

    -shell PAH has been investigated for a long time. However, most of the studies are complicated by their inherent high reactivity. In this work, two new stable benzannulated Chichibabin's hydrocarbons 1-CS and 2-OS were prepared, and their electronic structure

  18. Ground state searches in fcc intermetallics

    International Nuclear Information System (INIS)

    Wolverton, C.; de Fontaine, D.; Ceder, G.; Dreysse, H.

    1991-12-01

    A cluster expansion is used to predict the fcc ground states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. The intermetallic structures are not assumed, but derived regorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearized-muffin-tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration

  19. Ground states of quantum spin systems

    International Nuclear Information System (INIS)

    Bratteli, Ola; Kishimoto, Akitaka; Robinson, D.W.

    1978-07-01

    The authors prove that ground states of quantum spin systems are characterized by a principle of minimum local energy and that translationally invariant ground states are characterized by the principle of minimum energy per unit volume

  20. Search for the QCD ground state

    International Nuclear Information System (INIS)

    Reuter, M.; Wetterich, C.

    1994-05-01

    Within the Euclidean effective action approach we propose criteria for the ground state of QCD. Despite a nonvanishing field strength the ground state should be invariant with respect to modified Poincare transformations consisting of a combination of translations and rotations with suitable gauge transformations. We have found candidate states for QCD with four or more colours. The formation of gluon condensates shows similarities with the Higgs phenomenon. (orig.)

  1. Cavity optomechanics -- beyond the ground state

    Science.gov (United States)

    Meystre, Pierre

    2011-05-01

    The coupling of coherent optical systems to micromechanical devices, combined with breakthroughs in nanofabrication and in ultracold science, has opened up the exciting new field of cavity optomechanics. Cooling of the vibrational motion of a broad range on oscillating cantilevers and mirrors near their ground state has been demonstrated, and the ground state of at least one such system has now been reached. Cavity optomechanics offers much promise in addressing fundamental physics questions and in applications such as the detection of feeble forces and fields, or the coherent control of AMO systems and of nanoscale electromechanical devices. However, these applications require taking cavity optomechanics ``beyond the ground state.'' This includes the generation and detection of squeezed and other non-classical states, the transfer of squeezing between electromagnetic fields and motional quadratures, and the development of measurement schemes for the characterization of nanomechanical structures. The talk will present recent ``beyond ground state'' developments in cavity optomechanics. We will show how the magnetic coupling between a mechanical membrane and a BEC - or between a mechanical tuning fork and a nanoscale cantilever - permits to control and monitor the center-of-mass position of the mechanical system, and will comment on the measurement back-action on the membrane motion. We will also discuss of state transfer between optical and microwave fields and micromechanical devices. Work done in collaboration with Dan Goldbaum, Greg Phelps, Keith Schwab, Swati Singh, Steve Steinke, Mehmet Tesgin, and Mukund Vengallatore and supported by ARO, DARPA, NSF, and ONR.

  2. Stability properties of nonlinear dynamical systems and evolutionary stable states

    Energy Technology Data Exchange (ETDEWEB)

    Gleria, Iram, E-mail: iram@fis.ufal.br [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió-AL (Brazil); Brenig, Leon [Faculté des Sciences, Université Libre de Bruxelles, 1050 Brussels (Belgium); Rocha Filho, Tarcísio M.; Figueiredo, Annibal [Instituto de Física and International Center for Condensed Matter Physics, Universidade de Brasília, 70919-970 Brasília-DF (Brazil)

    2017-03-18

    Highlights: • We address the problem of equilibrium stability in a general class of non-linear systems. • We link Evolutionary Stable States (ESS) to stable fixed points of square quasi-polynomial (QP) systems. • We show that an interior ES point may be related to stable interior fixed points of QP systems. - Abstract: In this paper we address the problem of stability in a general class of non-linear systems. We establish a link between the concepts of asymptotic stable interior fixed points of square Quasi-Polynomial systems and evolutionary stable states, a property of some payoff matrices arising from evolutionary games.

  3. Thermodynamic Ground States of Complex Oxide Heterointerfaces

    DEFF Research Database (Denmark)

    Gunkel, F.; Hoffmann-Eifert, S.; Heinen, R. A.

    2017-01-01

    The formation mechanism of 2-dimensional electron gases (2DEGs) at heterointerfaces between nominally insulating oxides is addressed with a thermodynamical approach. We provide a comprehensive analysis of the thermodynamic ground states of various 2DEG systems directly probed in high temperature...

  4. Rearrangements in ground and excited states

    CERN Document Server

    de Mayo, Paul

    1980-01-01

    Rearrangements in Ground and Excited States, Volume 3 presents essays on the chemical generation of excited states; the cis-trans isomerization of olefins; and the photochemical rearrangements in trienes. The book also includes essays on the zimmerman rearrangements; the photochemical rearrangements of enones; the photochemical rearrangements of conjugated cyclic dienones; and the rearrangements of the benzene ring. Essays on the photo rearrangements via biradicals of simple carbonyl compounds; the photochemical rearrangements involving three-membered rings or five-membered ring heterocycles;

  5. Magnetic properties of singlet ground state systems

    International Nuclear Information System (INIS)

    Diederix, K.M.

    1979-01-01

    Experiments are described determining the properties of a magnetic system consisting of a singlet ground state. Cu(NO 3 ) 2 .2 1/2H 2 O has been studied which is a system of S = 1/2 alternating antiferromagnetic Heisenberg chains. The static properties, spin lattice relaxation time and field-induced antiferromagnetically ordered state measurements are presented. Susceptibility and magnetic cooling measurements of other compounds are summarised. (Auth.)

  6. Trapping cold ground state argon atoms.

    Science.gov (United States)

    Edmunds, P D; Barker, P F

    2014-10-31

    We trap cold, ground state argon atoms in a deep optical dipole trap produced by a buildup cavity. The atoms, which are a general source for the sympathetic cooling of molecules, are loaded in the trap by quenching them from a cloud of laser-cooled metastable argon atoms. Although the ground state atoms cannot be directly probed, we detect them by observing the collisional loss of cotrapped metastable argon atoms and determine an elastic cross section. Using a type of parametric loss spectroscopy we also determine the polarizability of the metastable 4s[3/2](2) state to be (7.3±1.1)×10(-39)  C m(2)/V. Finally, Penning and associative losses of metastable atoms in the absence of light assisted collisions, are determined to be (3.3±0.8)×10(-10)  cm(3) s(-1).

  7. RPA ground state correlations in nuclei

    International Nuclear Information System (INIS)

    Lenske, H.

    1990-01-01

    Overcounting in the RPA theory of ground state correlations is shown to be avoided if exact rather than quasiboson commutators are used. Single particle occupation probabilities are formulated in a compact way by the RPA Green function. Calculations with large configuration spaces and realistic interactions are performed with 1p1h RPA and second RPA (SRPA) including 2p2h mixing in excited states. In 41 Ca valence hole states are found to be quenched by about 10% in RPA and up to 18% in SRPA. Contributions from low and high lying excitations and their relation to long and short range correlations in finite nuclei are investigated. (orig.)

  8. Floating plant dominance as a stable state

    NARCIS (Netherlands)

    Scheffer, M.; Szabo, S.; Gragnani, A.; Nes, van E.H.; Rinaldi, S.; Kautsky, N.; Norberg, J.; Roijackers, R.M.M.; Franken, R.J.M.

    2003-01-01

    The authors demonstrate that floating-plant dominance can be a self-stabilizing ecosystem state, which may explain its notorious persistence in many situations. Their results, based on experiments, field data, and models (in Dutch ditches and Lake Kariba, Zimbabwe), represent evidence for

  9. Rearrangements in ground and excited states

    CERN Document Server

    de Mayo, Paul

    1980-01-01

    Rearrangements in Ground and Excited States, Volume 2 covers essays on the theoretical approach of rearrangements; the rearrangements involving boron; and the molecular rearrangements of organosilicon compounds. The book also includes essays on the polytopal rearrangement at phosphorus; the rearrangement in coordination complexes; and the reversible thermal intramolecular rearrangements of metal carbonyls. Chemists and people involved in the study of rearrangements will find the book invaluable.

  10. 66Ga ground state β spectrum

    DEFF Research Database (Denmark)

    Severin, Gregory; Knutson, L. D.; Voytas, P. A.

    2014-01-01

    The ground state branch of the β decay of 66Ga is an allowed Fermi (0+ → 0+) transition with a relatively high f t value. The large f t and the isospin-forbidden nature of the transition indicates that the shape of the β spectrum of this branch may be sensitive to higher order contributions...... to the decay. Two previous measurements of the shape have revealed deviations from an allowed spectrum but disagree about whether the shape factor has a positive or negative slope. As a test of a new iron-free superconducting β spectrometer, we have measured the shape of the ground state branch of the 66Ga β...... spectrum above a positron energy of 1.9 MeV. The spectrum is consistent with an allowed shape, with the slope of the shape factor being zero to within ±3 × 10−3 per MeV. We have also determined the endpoint energy for the ground state branch to be 4.1535 ± 0.0003 (stat.) ±0.0007 (syst.) MeV, in good...

  11. Ground states of a spin-boson model

    International Nuclear Information System (INIS)

    Amann, A.

    1991-01-01

    Phase transition with respect to ground states of a spin-boson Hamiltonian are investigated. The spin-boson model under discussion consists of one spin and infinitely many bosons with a dipole-type coupling. It is shown that the order parameter of the model vanishes with respect to arbitrary ground states if it vanishes with respect to ground states obtained as (biased) temperature to zero limits of thermic equilibrium states. The ground states of the latter special type have been investigated by H. Spohn. Spohn's respective phase diagrams are therefore valid for arbitrary ground states. Furthermore, disjointness of ground states in the broken symmetry regime is examined

  12. A Model Ground State of Polyampholytes

    International Nuclear Information System (INIS)

    Wofling, S.; Kantor, Y.

    1998-01-01

    The ground state of randomly charged polyampholytes (polymers with positive and negatively charged groups along their backbone) is conjectured to have a structure similar to a necklace, made of weakly charged parts of the chain, compacting into globules, connected by highly charged stretched 'strings' attempted to quantify the qualitative necklace model, by suggesting a zero approximation model, in which the longest neutral segment of the polyampholyte forms a globule, while the remaining part will form a tail. Expanding this approximation, we suggest a specific necklace-type structure for the ground state of randomly charged polyampholyte's, where all the neutral parts of the chain compact into globules: The longest neutral segment compacts into a globule; in the remaining part of the chain, the longest neutral segment (the second longest neutral segment) compacts into a globule, then the third, and so on. A random sequence of charges is equivalent to a random walk, and a neutral segment is equivalent to a loop inside the random walk. We use analytical and Monte Carlo methods to investigate the size distribution of loops in a one-dimensional random walk. We show that the length of the nth longest neutral segment in a sequence of N monomers (or equivalently, the nth longest loop in a random walk of N steps) is proportional to N/n 2 , while the mean number of neutral segments increases as √N. The polyampholytes in the ground state within our model is found to have an average linear size proportional to dN, and an average surface area proportional to N 2/3

  13. Ground-state structures of Hafnium clusters

    Energy Technology Data Exchange (ETDEWEB)

    Ng, Wei Chun; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technoloty, Multimedia University, Melaca Campus, 75450 Melaka (Malaysia)

    2015-04-24

    Hafnium (Hf) is a very large tetra-valence d-block element which is able to form relatively long covalent bond. Researchers are interested to search for substitution to silicon in the semi-conductor industry. We attempt to obtain the ground-state structures of small Hf clusters at both empirical and density-functional theory (DFT) levels. For calculations at the empirical level, charge-optimized many-body functional potential (COMB) is used. The lowest-energy structures are obtained via a novel global-minimum search algorithm known as parallel tempering Monte-Carlo Basin-Hopping and Genetic Algorithm (PTMBHGA). The virtue of using COMB potential for Hf cluster calculation lies in the fact that by including the charge optimization at the valence shells, we can encourage the formation of proper bond hybridization, and thus getting the correct bond order. The obtained structures are further optimized using DFT to ensure a close proximity to the ground-state.

  14. Ground state of high-density matter

    Science.gov (United States)

    Copeland, ED; Kolb, Edward W.; Lee, Kimyeong

    1988-01-01

    It is shown that if an upper bound to the false vacuum energy of the electroweak Higgs potential is satisfied, the true ground state of high-density matter is not nuclear matter, or even strange-quark matter, but rather a non-topological soliton where the electroweak symmetry is exact and the fermions are massless. This possibility is examined in the standard SU(3) sub C tensor product SU(2) sub L tensor product U(1) sub Y model. The bound to the false vacuum energy is satisfied only for a narrow range of the Higgs boson masses in the minimal electroweak model (within about 10 eV of its minimum allowed value of 6.6 GeV) and a somewhat wider range for electroweak models with a non-minimal Higgs sector.

  15. Is the ground state of Yang-Mills theory Coulombic?

    OpenAIRE

    Heinzl, Thomas; Ilderton, Anton; Langfeld, Kurt; Lavelle, Martin; Lutz, Wolfgang; McMullan, David

    2008-01-01

    We study trial states modelling the heavy quark-antiquark ground state in SU(2) Yang-Mills theory. A state describing the flux tube between quarks as a thin string of glue is found to be a poor description of the continuum ground state; the infinitesimal thickness of the string leads to UV artifacts which suppress the overlap with the ground state. Contrastingly, a state which surrounds the quarks with non-abelian Coulomb fields is found to have a good overlap with the ground state for all ch...

  16. Magnetic ground states in nanocuboids of cubic magnetocrystalline anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Bonilla, F.J., E-mail: fbonilla@cicenergigune.com; Lacroix, L.-M.; Blon, T., E-mail: thomas.blon@insa-toulouse.fr

    2017-04-15

    Flower and easy-axis vortex states are well-known magnetic configurations that can be stabilized in small particles. However, <111> vortex (V<111>), i.e. a vortex state with its core axis along the hard-axis direction, has been recently evidenced as a stable configuration in Fe nanocubes of intermediate sizes in the flower/vortex transition. In this context, we present here extensive micromagnetic simulations to determine the different magnetic ground states in ferromagnetic nanocuboids exhibiting cubic magnetocrystalline anisotropy (MCA). Focusing our study in the single-domain/multidomain size range (10–50 nm), we showed that V<111> is only stable in nanocuboids exhibiting peculiar features, such as a specific size, shape and magnetic environment, contrarily to the classical flower and easy-axis vortex states. Thus, to track experimentally these V<111> states, one should focused on (i) nanocuboids exhibiting a nearly perfect cubic shape (size distorsion <12%) made of (ii) a material which combines a zero or positive MCA and a high saturation magnetization, such as Fe or FeCo; and (iii) a low magnetic field environment, V<111> being only observed in virgin or remanent states. - Highlights: • The <111> vortex is numerically determined in nanocubes of cubic anisotropy. • It constitutes an intermediate state in the single-domain limit. • Such a vortex can only be stabilized in perfect or slightly deformed nanocuboids. • It exists in nanocuboids made of materials with zero or positive cubic anisotropy. • The associated magnetization reversal is described by a rotation of the vortex axis.

  17. Robust chaos synchronization using input-to-state stable control

    Indian Academy of Sciences (India)

    In this paper, we propose a new input-to-state stable (ISS) synchronization method for a general class of chaotic systems with disturbances. Based on Lyapunov theory and linear matrix inequality (LMI) approach, for the first time, the ISS synchronization controller is presented not only to guarantee the asymptotic ...

  18. Is the ground state of Yang-Mills theory Coulombic?

    Science.gov (United States)

    Heinzl, T.; Ilderton, A.; Langfeld, K.; Lavelle, M.; Lutz, W.; McMullan, D.

    2008-08-01

    We study trial states modelling the heavy quark-antiquark ground state in SU(2) Yang-Mills theory. A state describing the flux tube between quarks as a thin string of glue is found to be a poor description of the continuum ground state; the infinitesimal thickness of the string leads to UV artifacts which suppress the overlap with the ground state. Contrastingly, a state which surrounds the quarks with non-Abelian Coulomb fields is found to have a good overlap with the ground state for all charge separations. In fact, the overlap increases as the lattice regulator is removed. This opens up the possibility that the Coulomb state is the true ground state in the continuum limit.

  19. Neutrino ground state in a dense star

    International Nuclear Information System (INIS)

    Kiers, K.; Tytgat, M.H.

    1998-01-01

    It has recently been argued that long range forces due to the exchange of massless neutrinos give rise to a very large self-energy in a dense, finite-ranged, weakly charged medium. Such an effect, if real, would destabilize a neutron star. To address this issue we have studied the related problem of a massless neutrino field in the presence of an external, static electroweak potential of finite range. To be precise, we have computed to one loop the exact vacuum energy for the case of a spherical square well potential of depth α and radius R. For small wells, the vacuum energy is reliably determined by a perturbative expansion in the external potential. For large wells, however, the perturbative expansion breaks down. A manifestation of this breakdown is that the vacuum carries a non-zero neutrino charge. The energy and neutrino charge of the ground state are, to a good approximation for large wells, those of a neutrino condensate with chemical potential μ=α. Our results demonstrate explicitly that long-range forces due to the exchange of massless neutrinos do not threaten the stability of neutron stars. copyright 1998 The American Physical Society

  20. Activated carbon derived from waste coffee grounds for stable methane storage

    International Nuclear Information System (INIS)

    Kemp, K Christian; Baek, Seung Bin; Lee, Wang-Geun; Kim, Kwang S; Meyyappan, M

    2015-01-01

    An activated carbon material derived from waste coffee grounds is shown to be an effective and stable medium for methane storage. The sample activated at 900 °C displays a surface area of 1040.3 m"2 g"−"1 and a micropore volume of 0.574 cm"3 g"−"1 and exhibits a stable CH_4 adsorption capacity of ∼4.2 mmol g"−"1 at 3.0 MPa and a temperature range of 298 ± 10 K. The same material exhibits an impressive hydrogen storage capacity of 1.75 wt% as well at 77 K and 100 kPa. Here, we also propose a mechanism for the formation of activated carbon from spent coffee grounds. At low temperatures, the material has two distinct types with low and high surface areas; however, activation at elevated temperatures drives off the low surface area carbon, leaving behind the porous high surface area activated carbon. (paper)

  1. On the ground state of Yang-Mills theory

    OpenAIRE

    Bakry, Ahmed S.; Leinweber, Derek B.; Williams, Anthony G.

    2011-01-01

    We investigate the overlap of the ground state meson potential with sets of mesonic-trial wave functions corresponding to different gluonic distributions. We probe the transverse structure of the flux tube through the creation of non-uniform smearing profiles for the string of glue connecting two color sources in Wilson loop operator. The non-uniformly UV-regulated flux-tube operators are found to optimize the overlap with the ground state and display interesting features in the ground state ...

  2. The stable nonequilibrium state of bicarbonate aqueous systems

    Science.gov (United States)

    Voeikov, V. L.; Vilenskaya, N. D.; Ha, Do Minh; Malyshenko, S. I.; Buravleva, E. V.; Yablonskaya, O. I.; Timofeev, K. N.

    2012-09-01

    Data obtained by electron paramagnetic resonance (EPR) and chemiluminescence analysis indicate that in aqueous solutions of bicarbonates, superoxide radical and other reactive oxygen species (ROS) are constantly produced. The stationary level of the superoxide radical is found to increase when a solution is illuminated. Reactions involving ROS are shown to be accompanied by the generation of electron excitation energy, keeping bicarbonate solutions in a stable nonequilibrium state. The system can emit part of this energy. Variations in emitting activity are found to correlate with variations in the cosmophysical factors. The emitting activity of solutions is found to vary in the presence of low and ultralow concentrations of hydrated fullerenes. It is noted that the phenomenon of spontaneous charge separation in aqueous systems (G. H. Pollack) could play a role in maintaining a stable nonequilibrium state in bicarbonate systems where the reactions with ROS participation are catalyzed by forms of carbonate. It is concluded that the abovementioned properties of bicarbonate aqueous systems most likely keep living matter whose structural basis is formed by these systems in a stable excited state, thereby making it highly sensitive to the action of external factors with low and ultralow intensities.

  3. Ground cover influence on evaporation and stable water isotopes in soil water

    Science.gov (United States)

    Magdalena Warter, Maria; Jiménez-Rodríguez, Cesar D.; Coenders-Gerrits, Miriam; Teuling, Adriaan J. Ryan

    2017-04-01

    Forest ecosystems are characterized by complex structures which influence hydrological processes such as evaporation. The vertical stratification of the forest modifies the effect of the evaporation process due to the composition and local distribution of species within the forest. The evaluation of it will improve the understanding of evaporation in forest ecosystems. To determine the influence of forest understory on the fractionation front, four ground cover types were selected from the Speulderbos forest in the Netherlands. The native species of Thamariskmoss (Thuidium thamariscinum), Rough Stalked Feathermoss (Brachythecium rutabulum), and Haircapmoss (Polytrichum commune) as well as one type of litter made up of Douglas-Fir needles (Pseudotsuga menziesii) were used to analyse the rate of evaporation and changes on the isotopic concentration of the soil water on an in-situ basis in a controlled environment. Over a period of 4 weeks soil water content and atmospheric conditions were continuously measured, while the rainfall simulations were performed with different amounts and timings. The reference water added to the boxes keeps a stable composition along the trial period with a δ ^2H value of -42.59±1.15 \\permil} and δ 18O of -6.01±0.21 \\permil}. The evaporation front in the four ground covers is located between 5 and 10 cm depth and deuterium excess values are bigger than 5 \\permil. The litter layer of Douglas-Fir needles is the cover with higher fractionation in respect to the added water at 10 cm depth (δ ^2H: -29.79 \\permil), while the Haircapmoss keeps the lower fractionation rate at 5 cm and 10 cm (δ ^2H: -33.62 and δ ^2H: -35.34 \\permil). The differences showed by the soil water beneath the different ground covers depict the influence of ground cover on fractionation rates of the soil water, underlining the importance of the spatial heterogeneity of the evaporation front in the first 15 cm of soil.

  4. STABLE STATIONARY STATES OF NON-LOCAL INTERACTION EQUATIONS

    KAUST Repository

    FELLNER, KLEMENS

    2010-12-01

    In this paper, we are interested in the large-time behaviour of a solution to a non-local interaction equation, where a density of particles/individuals evolves subject to an interaction potential and an external potential. It is known that for regular interaction potentials, stable stationary states of these equations are generically finite sums of Dirac masses. For a finite sum of Dirac masses, we give (i) a condition to be a stationary state, (ii) two necessary conditions of linear stability w.r.t. shifts and reallocations of individual Dirac masses, and (iii) show that these linear stability conditions imply local non-linear stability. Finally, we show that for regular repulsive interaction potential Wε converging to a singular repulsive interaction potential W, the Dirac-type stationary states ρ̄ ε approximate weakly a unique stationary state ρ̄ ∈ L∞. We illustrate our results with numerical examples. © 2010 World Scientific Publishing Company.

  5. On the ground state of Yang-Mills theory

    International Nuclear Information System (INIS)

    Bakry, Ahmed S.; Leinweber, Derek B.; Williams, Anthony G.

    2011-01-01

    Highlights: → The ground state overlap for sets of meson potential trial states is measured. → Non-uniform gluonic distributions are probed via Wilson loop operator. → The locally UV-regulated flux-tube operators can optimize the ground state overlap. - Abstract: We investigate the overlap of the ground state meson potential with sets of mesonic-trial wave functions corresponding to different gluonic distributions. We probe the transverse structure of the flux tube through the creation of non-uniform smearing profiles for the string of glue connecting two color sources in Wilson loop operator. The non-uniformly UV-regulated flux-tube operators are found to optimize the overlap with the ground state and display interesting features in the ground state overlap.

  6. On the ground state for fractional quantum hall effect

    International Nuclear Information System (INIS)

    Jellal, A.

    1998-09-01

    In the present letter, we investigate the ground state wave function for an explicit model of electrons in an external magnetic field with specific inter-particle interactions. The excitation states of this model are also given. (author)

  7. Solving satisfiability problems by the ground-state quantum computer

    International Nuclear Information System (INIS)

    Mao Wenjin

    2005-01-01

    A quantum algorithm is proposed to solve the satisfiability (SAT) problems by the ground-state quantum computer. The scale of the energy gap of the ground-state quantum computer is analyzed for the 3-bit exact cover problem. The time cost of this algorithm on the general SAT problems is discussed

  8. Ground state phase diagram of extended attractive Hubbard model

    International Nuclear Information System (INIS)

    Robaszkiewicz, S.; Chao, K.A.; Micnas, R.

    1980-08-01

    The ground state phase diagram of the extended Hubbard model with intraatomic attraction has been derived in the Hartree-Fock approximation formulated in terms of the Bogoliubov variational approach. For a given value of electron density, the nature of the ordered ground state depends essentially on the sign and the strength of the nearest neighbor coupling. (author)

  9. Classical many-particle systems with unique disordered ground states

    Science.gov (United States)

    Zhang, G.; Stillinger, F. H.; Torquato, S.

    2017-10-01

    Classical ground states (global energy-minimizing configurations) of many-particle systems are typically unique crystalline structures, implying zero enumeration entropy of distinct patterns (aside from trivial symmetry operations). By contrast, the few previously known disordered classical ground states of many-particle systems are all high-entropy (highly degenerate) states. Here we show computationally that our recently proposed "perfect-glass" many-particle model [Sci. Rep. 6, 36963 (2016), 10.1038/srep36963] possesses disordered classical ground states with a zero entropy: a highly counterintuitive situation . For all of the system sizes, parameters, and space dimensions that we have numerically investigated, the disordered ground states are unique such that they can always be superposed onto each other or their mirror image. At low energies, the density of states obtained from simulations matches those calculated from the harmonic approximation near a single ground state, further confirming ground-state uniqueness. Our discovery provides singular examples in which entropy and disorder are at odds with one another. The zero-entropy ground states provide a unique perspective on the celebrated Kauzmann-entropy crisis in which the extrapolated entropy of a supercooled liquid drops below that of the crystal. We expect that our disordered unique patterns to be of value in fields beyond glass physics, including applications in cryptography as pseudorandom functions with tunable computational complexity.

  10. Stable solid state reference electrodes for high temperature water chemistry

    International Nuclear Information System (INIS)

    Jayaweera, P.; Millett, P.J.

    1995-01-01

    A solid state electrode capable of providing a stable reference potential under a wide range of temperatures and chemical conditions has been demonstrated. The electrode consists of a zirconia or yttria-stabilized zirconia tube packed with an inorganic polymer electrolyte and a silver/silver chloride sensing element. The sensing element is maintained near room temperature by a passive cooling heat sink. The electrode stability was demonstrated by testing it in high temperature (280 C) aqueous solutions over extended periods of time. This reference electrode is useful in many applications, particularly for monitoring the chemistry in nuclear and fossil power plants

  11. Ferroelectric nanostructure having switchable multi-stable vortex states

    Science.gov (United States)

    Naumov, Ivan I [Fayetteville, AR; Bellaiche, Laurent M [Fayetteville, AR; Prosandeev, Sergey A [Fayetteville, AR; Ponomareva, Inna V [Fayetteville, AR; Kornev, Igor A [Fayetteville, AR

    2009-09-22

    A ferroelectric nanostructure formed as a low dimensional nano-scale ferroelectric material having at least one vortex ring of polarization generating an ordered toroid moment switchable between multi-stable states. A stress-free ferroelectric nanodot under open-circuit-like electrical boundary conditions maintains such a vortex structure for their local dipoles when subject to a transverse inhomogeneous static electric field controlling the direction of the macroscopic toroidal moment. Stress is also capable of controlling the vortex's chirality, because of the electromechanical coupling that exists in ferroelectric nanodots.

  12. α-decay half-lives of some nuclei from ground state to ground state using different nuclear potential

    Directory of Open Access Journals (Sweden)

    Akrawy Dashty T.

    2018-01-01

    Full Text Available Theoretical α-decay half-lives of some nuclei from ground state to ground state are calculated using different nuclear potential model including Coulomb proximity potential (CPPM, Royer proximity potential and Broglia and Winther 1991. The calculated values comparing with experimental data, it is observed that the CPPM model is in good agreement with the experimental data.

  13. Split degenerate states and stable p+ip phases from holography

    Energy Technology Data Exchange (ETDEWEB)

    Nie, Zhang-Yu; Zeng, Hui [Kunming University of Science and Technology, Kunming (China); Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing (China); Pan, Qiyuan [Hunan Normal Univ., Key Lab. of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, and Synergetic Innovation Center for Quantum Effects and Applications, Dept. of Physics, Changsha (China); Zeng, Hua-Bi [Yangzhou University, College of Physics Science and Technology, Yangzhou, Jiangsu (China); National Central University, Department of Physics, Chungli (China)

    2017-02-15

    In this paper, we investigate the p+ip superfluid phases in the complex vector field holographic p-wave model. We find that in the probe limit, the p+ip phase and the p-wave phase are equally stable, hence the p and ip orders can be mixed with an arbitrary ratio to form more general p+λip phases, which are also equally stable with the p-wave and p+ip phases. As a result, the system possesses a degenerate thermal state in the superfluid region. We further study the case on considering the back-reaction on the metric, and we find that the degenerate ground states will be separated into p-wave and p+ip phases, and the p-wave phase is more stable. Finally, due to the different critical temperature of the zeroth order phase transitions from p-wave and p+ip phases to the normal phase, there is a temperature region where the p+ip phase exists but the p-wave phase does not. In this region we find the stable holographic p+ip phase for the first time. (orig.)

  14. Fission barriers and asymmetric ground states in the relativistic mean-field theory

    International Nuclear Information System (INIS)

    Rutz, K.; Reinhard, P.G.; Greiner, W.

    1995-01-01

    The symmetric and asymmetric fission path for 240 Pu, 232 Th and 226 Ra is investigated within the relativistic mean-field model. Standard parametrizations which are well fitted to nuclear ground-state properties are found to deliver reasonable qualitative and quantitative features of fission, comparable to similar nonrelativistic calculations. Furthermore, stable octupole deformations in the ground states of radium isotopes are investigated. They are found in a series of isotopes, qualitatively in agreement with nonrelativistic models. But the quantitative details differ amongst the models and between the various relativistic parametrizations. (orig.)

  15. Ground state energy fluctuations in the nuclear shell model

    International Nuclear Information System (INIS)

    Velazquez, Victor; Hirsch, Jorge G.; Frank, Alejandro; Barea, Jose; Zuker, Andres P.

    2005-01-01

    Statistical fluctuations of the nuclear ground state energies are estimated using shell model calculations in which particles in the valence shells interact through well-defined forces, and are coupled to an upper shell governed by random 2-body interactions. Induced ground-state energy fluctuations are found to be one order of magnitude smaller than those previously associated with chaotic components, in close agreement with independent perturbative estimates based on the spreading widths of excited states

  16. On calculations of the ground state energy in quantum mechanics

    International Nuclear Information System (INIS)

    Efimov, G.V.

    1991-02-01

    In nonrelativistic quantum mechanics the Wick-ordering method called the oscillator representation suggested to calculate the ground-state energy for a wide class of potentials allowing the existence of a bound state. The following examples are considered: the orbital excitations of the ground-state in the Coulomb plus linear potential, the Schroedinger equation with a ''relativistic'' kinetic energy √p 2 +m 2 , the Coulomb three-body problem. (author). 22 refs, 2 tabs

  17. Entanglement of two ground state neutral atoms using Rydberg blockade

    DEFF Research Database (Denmark)

    Miroshnychenko, Yevhen; Browaeys, Antoine; Evellin, Charles

    2011-01-01

    We report on our recent progress in trapping and manipulation of internal states of single neutral rubidium atoms in optical tweezers. We demonstrate the creation of an entangled state between two ground state atoms trapped in separate tweezers using the effect of Rydberg blockade. The quality...... of the entanglement is measured using global rotations of the internal states of both atoms....

  18. On the ground state of Yang-Mills theory

    Science.gov (United States)

    Bakry, Ahmed S.; Leinweber, Derek B.; Williams, Anthony G.

    2011-08-01

    We investigate the overlap of the ground state meson potential with sets of mesonic-trial wave functions corresponding to different gluonic distributions. We probe the transverse structure of the flux tube through the creation of non-uniform smearing profiles for the string of glue connecting two color sources in Wilson loop operator. The non-uniformly UV-regulated flux-tube operators are found to optimize the overlap with the ground state and display interesting features in the ground state overlap.

  19. Vegetation engineers marsh morphology through multiple competing stable states

    Science.gov (United States)

    Marani, Marco; Da Lio, Cristina; D’Alpaos, Andrea

    2013-01-01

    Marshes display impressive biogeomorphic features, such as zonation, a mosaic of extensive vegetation patches of rather uniform composition, exhibiting sharp transitions in the presence of extremely small topographic gradients. Although generally associated with the accretion processes necessary for marshes to keep up with relative sea level rise, competing environmental constraints, and ecologic controls, zonation is still poorly understood in terms of the underlying biogeomorphic mechanisms. Here we find, through observations and modeling interpretation, that zonation is the result of coupled geomorphological–biological dynamics and that it stems from the ability of vegetation to actively engineer the landscape by tuning soil elevation within preferential ranges of optimal adaptation. We find multiple peaks in the frequency distribution of observed topographic elevation and identify them as the signature of biologic controls on geomorphodynamics through competing stable states modulated by the interplay of inorganic and organic deposition. Interestingly, the stable biogeomorphic equilibria correspond to suboptimal rates of biomass production, a result coherent with recent observations. The emerging biogeomorphic structures may display varying degrees of robustness to changes in the rate of sea level rise and sediment availability, with implications for the overall resilience of marsh ecosystems to climatic changes. PMID:23401529

  20. Ground State Energy of the Modified Nambu-Goto String

    Science.gov (United States)

    Hadasz, Leszek

    We calculate, using zeta function regularization method, semiclassical energy of the Nambu-Goto string supplemented with the boundary, Gauss-Bonnet term in the action and discuss the tachyonic ground state problem.

  1. Ground state energy of the modified Nambu-Goto string

    OpenAIRE

    Hadasz, Leszek

    1997-01-01

    We calculate, using zeta function regularization method, semiclassical energy of the Nambu-Goto string supplemented with the boundary, Gauss-Bonnet term in the action and discuss the tachyonic ground state problem.

  2. Approximating the ground state of gapped quantum spin systems

    Energy Technology Data Exchange (ETDEWEB)

    Michalakis, Spyridon [Los Alamos National Laboratory; Hamza, Eman [NON LANL; Nachtergaele, Bruno [NON LANL; Sims, Robert [NON LANL

    2009-01-01

    We consider quantum spin systems defined on finite sets V equipped with a metric. In typical examples, V is a large, but finite subset of Z{sup d}. For finite range Hamiltonians with uniformly bounded interaction terms and a unique, gapped ground state, we demonstrate a locality property of the corresponding ground state projector. In such systems, this ground state projector can be approximated by the product of observables with quantifiable supports. In fact, given any subset {chi} {contained_in} V the ground state projector can be approximated by the product of two projections, one supported on {chi} and one supported on {chi}{sup c}, and a bounded observable supported on a boundary region in such a way that as the boundary region increases, the approximation becomes better. Such an approximation was useful in proving an area law in one dimension, and this result corresponds to a multi-dimensional analogue.

  3. The ground state energy of a classical gas

    International Nuclear Information System (INIS)

    Conlon, J.G.

    1983-01-01

    The ground state energy of a classical gas is treated using a probability function for the position of the particles and a potential function. The lower boundary for the energy when the particle number is large is defined as ground state energy. The coulomb gas consisting of positive and negative particles is also treated (fixed and variable density case) the stability of the relativistic system is investigated as well. (H.B.)

  4. Theory of ground state factorization in quantum cooperative systems.

    Science.gov (United States)

    Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio

    2008-05-16

    We introduce a general analytic approach to the study of factorization points and factorized ground states in quantum cooperative systems. The method allows us to determine rigorously the existence, location, and exact form of separable ground states in a large variety of, generally nonexactly solvable, spin models belonging to different universality classes. The theory applies to translationally invariant systems, irrespective of spatial dimensionality, and for spin-spin interactions of arbitrary range.

  5. Ground state structure of U2Mo: static and lattice dynamics study

    International Nuclear Information System (INIS)

    Mukherjee, D.; Sahoo, B.D.; Joshi, K.D.; Kaushik, T.C.

    2016-01-01

    According to experimental reports, the ground state stable structure of U 2 Mo is tetragonal. However, various theoretical studies performed in past do not get tetragonal phase as the stable structure at ambient conditions. Therefore, the ground state structure of U 2 Mo is still unresolved. In an attempt to understand the ground state properties of this system, we have carried out first principle electronic band structure calculations. The structural stability analysis carried out using evolutionary structure search algorithm in conjunction with ab-inito method shows that a hexagonal structure (space group P6/mmm) is the lowest enthalpy structure at ambient condition and remains stable upto 200 GPa. The elastic and lattice dynamical stability further supports the stability of this phase at ambient condition. Further, using the 0 K calculations in conjunction with finite temperature corrections, we have derived the isotherm and shock adiabat (Hugoniot) of this material. Various equilibrium properties such as ambient pressure volume, bulk modulus, pressure derivative of bulk modulus etc. are derived from equation of state. (author)

  6. Study of Atomic Quasi-Stable States, Decoherence And Cooling of Mesoscale Particles

    Science.gov (United States)

    Zhong, Changchun

    Quantum mechanics, since its very beginning, has totally changed the way we understand nature. The past hundred years have seen great successes in the application of quantum physics, including atomic spectra, laser technology, condensed matter physics and the remarkable possibility for quantum computing, etc. This thesis is dedicated to a small regime of quantum physics. In the first part of the thesis, I present the studies of atomic quasi-stable states, which refer to those Rydberg states of an atom that are relatively stable in the presence of strong fields. Through spectrally probing the quasi-stable states, series of survival peaks are found. If the quasi-stable electrons were created by ultraviolet (UV) lasers with two different frequencies, the survival peaks could be modulated by continuously changing the phase difference between the UV and the IR laser. The quantum simulation, through directly solving the Schrodinger equation, matches the experimental results performed with microwave fields, and our studies should provide a guidance for future experiments. Despite the huge achievements in the application of quantum theory, there are still some fundamental problems that remain unresolved. One of them is the so-called quantum-to-classical transition, which refers to the expectation that the system behaves in a more classical manner when the system size increases. This basic question was not well answered until decoherence theory was proposed, which states that the coherence of a quantum system tends to be destroyed by environmental interruptions. Thus, if a system is well isolated from its environment, it is in principle possible to observe macroscopic quantum coherence. Quite recently, testing quantum principles in the macroscale has become a hot topic due to rapic technological developments. A very promising platform for testing macroscale quantum physics is a laser levitated nanoparticle, and cooling its mechanical motion to the ground state is the first

  7. Ground-Water Availability in the United States

    Science.gov (United States)

    Reilly, Thomas E.; Dennehy, Kevin F.; Alley, William M.; Cunningham, William L.

    2008-01-01

    Ground water is among the Nation's most important natural resources. It provides half our drinking water and is essential to the vitality of agriculture and industry, as well as to the health of rivers, wetlands, and estuaries throughout the country. Large-scale development of ground-water resources with accompanying declines in ground-water levels and other effects of pumping has led to concerns about the future availability of ground water to meet domestic, agricultural, industrial, and environmental needs. The challenges in determining ground-water availability are many. This report examines what is known about the Nation's ground-water availability and outlines a program of study by the U.S. Geological Survey Ground-Water Resources Program to improve our understanding of ground-water availability in major aquifers across the Nation. The approach is designed to provide useful regional information for State and local agencies who manage ground-water resources, while providing the building blocks for a national assessment. The report is written for a wide audience interested or involved in the management, protection, and sustainable use of the Nation's water resources.

  8. A stable isotopic view on lianas' and trees' below ground competition for water

    Science.gov (United States)

    De Deurwaerder, Hannes; Hervé-Fernández, Pedro; Stahl, Clément; Bonal, Damien; Burban, Benoît; Petronelli, Pascal; Boeckx, Pascal; Verbeeck, Hans

    2017-04-01

    Various studies highlight an increase in liana abundance and biomass in the neotropics in the last decades. To date, the reason why this growth form expresses this trend is still unclear. One of the proposed hypotheses ascribes tropical lianas, in comparison to tropical trees, of being able to adapt better to increased drought conditions resulting from climate change. Moreover, lianas presumably have a deeper root system, providing access to deeper soil layers less susceptible for dehydration during drought events. A dual stable water isotopic approach (δ18O and δ2H) enables studying vegetation below ground competition and in combination with Bayesian mixing models can provide insight in the fractional contribution of distinct soil layer depths. In this perspective, precipitation (bulk and through fall), bulk soil (at different depths), stream and xylem water of both lianas and trees were sampled between October 7-13, 2015. The study focusses on two distinct plots differing in soil texture (sand and clay), localized in close vicinity of the Guyana flux tower at Paracou (French Guyana). Our study highlights the erroneous of the deep tap root hypothesis and provides new insights in water and nutrient competition between tropical lianas and trees during dry season. Lianas isotopic signature is enriched compared to those of trees. This can be linked to water source depth and soil seasonal replenishment. Moreover, liana displaying a very active soil surface root activity, efficiently capturing the low amount of dry season precipitation, while trees show to tap the deeper and less drought susceptible soil layers. A strategy, which not only results in a spatial niche separation in the underground competition for water, but it also provides lianas with a definite advantage in nutrient competition.

  9. Ground state correlations and structure of odd spherical nuclei

    International Nuclear Information System (INIS)

    Mishev, S.; Voronov, V. V.

    2006-01-01

    It is well known that the Pauli principle plays a substantial role at low energies because the phonon operators are not ideal boson operators. Calculating the exact commutators between the quasiparticle and phonon operators one can take into account the Pauli principle corrections. Besides the ground state correlations due to the quasiparticle interaction in the ground state influence the single particle fragmentation as well. In this paper, we generalize the basic QPM equations to account for both mentioned effects. As an illustration of our approach, calculations on the structure of the low-lying states in "1"3"1Ba have been performed.

  10. Ground state correlations and structure of odd spherical nuclei

    International Nuclear Information System (INIS)

    Mishev, S.; Voronov, V.V.

    2008-01-01

    It is well known that the Pauli principle plays a substantial role at low energies because the phonon operators are not ideal boson operators. Calculating the exact commutators between the quasiparticle and phonon operators one can take into account the Pauli principle corrections. Besides, the ground state correlations due to the quasiparticle interaction in the ground state influence the single-particle fragmentation as well. In this paper, we generalize the basic equations of the quasiparticle-phonon nuclear model to account for both effects mentioned. As an illustration of our approach, calculations on the structure of the low-lying states in 133 Ba have been performed

  11. High-speed ground transportation development outside United States

    Energy Technology Data Exchange (ETDEWEB)

    Eastham, T.R. [Queen`s Univ., Kingston, Ontario (United Kingdom)

    1995-09-01

    This paper surveys the state of high-speed (in excess of 200 km/h) ground-transportation developments outside the United States. Both high-speed rail and Maglev systems are covered. Many vehicle systems capable of providing intercity service in the speed range 200--500 km/h are or will soon be available. The current state of various technologies, their implementation, and the near-term plans of countries that are most active in high-speed ground transportation development are reported.

  12. Probing quantum frustrated systems via factorization of the ground state.

    Science.gov (United States)

    Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio

    2010-05-21

    The existence of definite orders in frustrated quantum systems is related rigorously to the occurrence of fully factorized ground states below a threshold value of the frustration. Ground-state separability thus provides a natural measure of frustration: strongly frustrated systems are those that cannot accommodate for classical-like solutions. The exact form of the factorized ground states and the critical frustration are determined for various classes of nonexactly solvable spin models with different spatial ranges of the interactions. For weak frustration, the existence of disentangling transitions determines the range of applicability of mean-field descriptions in biological and physical problems such as stochastic gene expression and the stability of long-period modulated structures.

  13. Fast Preparation of Critical Ground States Using Superluminal Fronts

    Science.gov (United States)

    Agarwal, Kartiek; Bhatt, R. N.; Sondhi, S. L.

    2018-05-01

    We propose a spatiotemporal quench protocol that allows for the fast preparation of ground states of gapless models with Lorentz invariance. Assuming the system initially resides in the ground state of a corresponding massive model, we show that a superluminally moving "front" that locally quenches the mass, leaves behind it (in space) a state arbitrarily close to the ground state of the gapless model. Importantly, our protocol takes time O (L ) to produce the ground state of a system of size ˜Ld (d spatial dimensions), while a fully adiabatic protocol requires time ˜O (L2) to produce a state with exponential accuracy in L . The physics of the dynamical problem can be understood in terms of relativistic rarefaction of excitations generated by the mass front. We provide proof of concept by solving the proposed quench exactly for a system of free bosons in arbitrary dimensions, and for free fermions in d =1 . We discuss the role of interactions and UV effects on the free-theory idealization, before numerically illustrating the usefulness of the approach via simulations on the quantum Heisenberg spin chain.

  14. Ground-state fidelity in the BCS-BEC crossover

    International Nuclear Information System (INIS)

    Khan, Ayan; Pieri, Pierbiagio

    2009-01-01

    The ground-state fidelity has been introduced recently as a tool to investigate quantum phase transitions. Here, we apply this concept in the context of a crossover problem. Specifically, we calculate the fidelity susceptibility for the BCS ground-state wave function, when the intensity of the fermionic attraction is varied from weak to strong in an interacting Fermi system, through the BCS-Bose-Einstein Condensation crossover. Results are presented for contact and finite-range attractive potentials and for both continuum and lattice models. We conclude that the fidelity susceptibility can be useful also in the context of crossover problems.

  15. Measurement of the ground-state hyperfine splitting of antihydrogen

    CERN Document Server

    Juhász, B; Federmann, S

    2011-01-01

    The ASACUSA collaboration at the Antiproton Decelerator of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic beam line, consisting of a cusp trap as a source of partially polarized antihydrogen atoms, a radiofrequency spin-flip cavity, a superconducting sextupole magnet as spin analyser, and an antihydrogen detector. This will be a measurement of the antiproton magnetic moment, and also a test of the CPT invariance. Monte Carlo simulations predict that the antihydrogen ground-state hyperfine splitting can be determined with a relative precision of ~10−7. The first preliminary measurements of the hyperfine transitions will start in 2011.

  16. Coherent Control of Ground State NaK Molecules

    Science.gov (United States)

    Yan, Zoe; Park, Jee Woo; Loh, Huanqian; Will, Sebastian; Zwierlein, Martin

    2016-05-01

    Ultracold dipolar molecules exhibit anisotropic, tunable, long-range interactions, making them attractive for the study of novel states of matter and quantum information processing. We demonstrate the creation and control of 23 Na40 K molecules in their rovibronic and hyperfine ground state. By applying microwaves, we drive coherent Rabi oscillations of spin-polarized molecules between the rotational ground state (J=0) and J=1. The control afforded by microwave manipulation allows us to pursue engineered dipolar interactions via microwave dressing. By driving a two-photon transition, we are also able to observe Ramsey fringes between different J=0 hyperfine states, with coherence times as long as 0.5s. The realization of long coherence times between different molecular states is crucial for applications in quantum information processing. NSF, AFOSR- MURI, Alfred P. Sloan Foundation, DARPA-OLE

  17. Dissociation energy of the ground state of NaH

    International Nuclear Information System (INIS)

    Huang, Hsien-Yu; Lu, Tsai-Lien; Whang, Thou-Jen; Chang, Yung-Yung; Tsai, Chin-Chun

    2010-01-01

    The dissociation energy of the ground state of NaH was determined by analyzing the observed near dissociation rovibrational levels. These levels were reached by stimulated emission pumping and fluorescence depletion spectroscopy. A total of 114 rovibrational levels in the ranges 9≤v '' ≤21 and 1≤J '' ≤14 were assigned to the X 1 Σ + state of NaH. The highest vibrational level observed was only about 40 cm -1 from the dissociation limit in the ground state. One quasibound state, above the dissociation limit and confined by the centrifugal barrier, was observed. Determining the vibrational quantum number at dissociation v D from the highest four vibrational levels yielded the dissociation energy D e =15 815±5 cm -1 . Based on new observations and available data, a set of Dunham coefficients and the rotationless Rydberg-Klein-Rees curve were constructed. The effective potential curve and the quasibound states were discussed.

  18. Three-body problem in the ground-state representation

    International Nuclear Information System (INIS)

    Gonzalez, A.

    1993-01-01

    The ground-state probability density of a three-body system is used to construct a classical potential U whose minimum coincides exactly with the ground-state energy. The spectrum of excited states may approximately be obtained by imposing quasiclassical quantization conditions over the classical motion in U. We show nontrivial one-dimensional models in which either this quantization condition is exact or considerably improves the usual semiclassical quantization. For three-dimensional problems, the small-oscillation frequencies in states with total angular momentum L = 0 are computed. These frequencies could represent an improvement over the frequencies of triatomic molecules computed with the use of ordinary quasiclassics for the motion of the nuclei in the molecular term. By providing a semiclassical description of the first excited quantum states, the sketched approach rises some interesting questions such as, for example, the relevance (once again) of classical chaos to quantum mechanics

  19. Zero-Magnetic-Field Spin Splitting of Polaron's Ground State Energy Induced by Rashba Spin-Orbit Interaction

    International Nuclear Information System (INIS)

    Liu Jia; Xiao Jingling

    2006-01-01

    We study theoretically the ground state energy of a polaron near the interface of a polar-polar semiconductor by considering the Rashba spin-orbit (SO) coupling with the Lee-Low-Pines intermediate coupling method. Our numerical results show that the Rashba SO interaction originating from the inversion asymmetry in the heterostructure splits the ground state energy of the polaron. The electron areal density and vector dependence of the ratio of the SO interaction to the total ground state energy or other energy composition are obvious. One can see that even without any external magnetic field, the ground state energy can be split by the Rashba SO interaction, and this split is not a single but a complex one. Since the presents of the phonons, whose energy gives negative contribution to the polaron's, the spin-splitting states of the polaron are more stable than electron's.

  20. Ground state of the parallel double quantum dot system.

    Science.gov (United States)

    Zitko, Rok; Mravlje, Jernej; Haule, Kristjan

    2012-02-10

    We resolve the controversy regarding the ground state of the parallel double quantum dot system near half filling. The numerical renormalization group predicts an underscreened Kondo state with residual spin-1/2 magnetic moment, ln2 residual impurity entropy, and unitary conductance, while the Bethe ansatz solution predicts a fully screened impurity, regular Fermi-liquid ground state, and zero conductance. We calculate the impurity entropy of the system as a function of the temperature using the hybridization-expansion continuous-time quantum Monte Carlo technique, which is a numerically exact stochastic method, and find excellent agreement with the numerical renormalization group results. We show that the origin of the unconventional behavior in this model is the odd-symmetry "dark state" on the dots.

  1. Ground-state electronic structure of actinide monocarbides and mononitrides

    DEFF Research Database (Denmark)

    Petit, Leon; Svane, Axel; Szotek, Z.

    2009-01-01

    The self-interaction corrected local spin-density approximation is used to investigate the ground-state valency configuration of the actinide ions in the actinide monocarbides, AC (A=U,Np,Pu,Am,Cm), and the actinide mononitrides, AN. The electronic structure is characterized by a gradually increa...

  2. A Ground State Tri-pí-Methane Rearrangement

    Czech Academy of Sciences Publication Activity Database

    Zimmerman, H. E.; Církva, Vladimír; Jiang, L.

    2000-01-01

    Roč. 41, č. 49 (2000), s. 9585-9587 ISSN 0040-4039 Institutional research plan: CEZ:AV0Z4072921 Keywords : tri-pi-methane * ground state Subject RIV: CC - Organic Chemistry Impact factor: 2.558, year: 2000

  3. Calculations of the ground state of 16O

    International Nuclear Information System (INIS)

    Pieper, S.C.

    1989-01-01

    One of the central problems in nuclear physics is the description of nuclei as systems of nucleons interacting via realistic potentials. There are two main aspects of this problem: specification of the Hamiltonian, and calculation of the ground states of nuclei with the given interaction. Realistic interactions must contain both two- and three-nucleon potentials and these potentials have a complicated non-central operator structure consisting, for example, of spin, isospin and tensor dependences. This structure results in formidable many-body problems in the computation of the ground states of nuclei. At present, reliable solutions of the Faddeev equations for the A = 3 nuclei with such interactions are routine. Recently, Carlson has made an essentially exact GFMC calculation of the He ground state using just a two-nucleon interaction, and there are reliable variational calculations for more complete potential models. Nuclear matter calculations can also be made with reasonable reliability. However, there have been very few calculations of nuclei with A > 5 using realistic interactions, and none with a modern three-nucleon interaction. In the present paper I present a new technique for variational calculations for such nuclei and apply it to the ground state of 16 O. 15 refs., 2 figs., 3 tabs

  4. Ground state energy of a polaron in a superlattice

    International Nuclear Information System (INIS)

    Mensah, S.Y.; Allotey, F.K.A.; Nkrumah, G.; Mensah, N.G.

    2000-10-01

    The ground state energy of a polaron in a superlattice was calculated using the double-time Green functions. The effective mass of the polaron along the planes perpendicular to the superlattice axis was also calculated. The dependence of the ground state energy and the effective mass along the planes perpendicular to the superlattice axis on the electron-phonon coupling constant α and on the superlattice parameters (i.e. the superlattice period d and the bandwidth Δ) were studied. It was observed that if an infinite square well potential is assumed, the ground state energy of the polaron decreases (i.e. becomes more negative) with increasing α and d, but increases with increasing Δ. For small values of α, the polaron ground state energy varies slowly with Δ, becoming approximately constant for large Δ. The effective mass along the planes perpendicular to the superlattice axis was found to be approximately equal to the mass of an electron for all typical values of α, d and Δ. (author)

  5. Observation of Hyperfine Transitions in Trapped Ground-State Antihydrogen

    CERN Document Server

    Olin, Arthur

    2015-01-01

    This paper discusses the first observation of stimulated magnetic resonance transitions between the hyperfine levels of trapped ground state atomic antihydrogen, confirming its presence in the ALPHA apparatus. Our observations show that these transitions are consistent with the values in hydrogen to within 4~parts~in~$10^3$. Simulations of the trapped antiatoms in a microwave field are consistent with our measurements.

  6. Search for C+ C clustering in Mg ground state

    Indian Academy of Sciences (India)

    2017-01-04

    Jan 4, 2017 ... Finite-range knockout theory predictions were much larger for (12C,212C) reaction, indicating a very small 12C−12C clustering in 24Mg. (g.s.) . Our present results contradict most of the proposed heavy cluster (12C+12C) structure models for the ground state of 24Mg. Keywords. Direct nuclear reactions ...

  7. α-clustering in the ground state of 40Ca

    International Nuclear Information System (INIS)

    Michel, F.

    1976-01-01

    The anomalous large angle scattering observed in 40 Ca(α, α) is studied in the frame of a semi-microscopic model taking into account the presence of α-correlations in the ground state of 40 Ca. The calculations, performed between 18 and 29 MeV, assert the potential, non resonant nature of the phenomenon. (Auth.)

  8. Ground states of the massless Derezinski-Gerard model

    International Nuclear Information System (INIS)

    Ohkubo, Atsushi

    2009-01-01

    We consider the massless Derezinski-Gerard model introduced by Derezinski and Gerard in 1999. We give a sufficient condition for the existence of a ground state of the massless Derezinski-Gerard model without the assumption that the Hamiltonian of particles has compact resolvent.

  9. Magnetic excitons in singlet-ground-state ferromagnets

    DEFF Research Database (Denmark)

    Birgeneau, R.J.; Als-Nielsen, Jens Aage; Bucher, E.

    1971-01-01

    The authors report measurements of the dispersion of singlet-triplet magnetic excitons as a function of temperature in the singlet-ground-state ferromagnets fcc Pr and Pr3Tl. Well-defined excitons are observed in both the ferromagnetic and paramagnetic regions, but with energies which are nearly...

  10. Correlation induced paramagnetic ground state in FeAl

    Czech Academy of Sciences Publication Activity Database

    Mohn, P.; Persson, C.; Blaha, P.; Schwarz, K.; Novák, Pavel; Eschrig, H.

    2001-01-01

    Roč. 87, č. 19 (2001), s. 196401-1-196401-4 ISSN 0031-9007 Institutional research plan: CEZ:AV0Z1010914 Keywords : FeAl * paramagnetic ground state Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 6.668, year: 2001

  11. Observation of hyperfine transitions in trapped ground-state antihydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Collaboration: A. Olin for the ALPHA Collaboration

    2015-08-15

    This paper discusses the first observation of stimulated magnetic resonance transitions between the hyperfine levels of trapped ground state atomic antihydrogen, confirming its presence in the ALPHA apparatus. Our observations show that these transitions are consistent with the values in hydrogen to within 4 parts in 10{sup 3}. Simulations of the trapped antiatoms in a microwave field are consistent with our measurements.

  12. Antiferrodistortive phase transitions and ground state of PZT ceramics

    International Nuclear Information System (INIS)

    Pandey, Dhananjai

    2013-01-01

    The ground state of the technologically important Pb(Zr x Ti (1-x) )O 3 , commonly known as PZT, ceramics is currently under intense debate. The phase diagram of this material shows a morphotropic phase boundary (MPB) for x∼0.52 at 300K, across which a composition induced structural phase transition occurs leading to maximization of the piezoelectric properties. In search for the true ground state of the PZT in the MPB region, Beatrix Noheda and coworkers first discovered a phase transition from tetragonal (space group P4mm) to an M A type monoclinic phase (space group Cm) at low temperatures for x=0.52. Soon afterwards, we discovered yet another low temperature phase transition for the same composition in which the M A type (Cm) monoclinic phase transforms to another monoclinic phase with Cc space group. We have shown that the Cm to Cc phase transition is an antiferrodistortive (AFD) transition involving tilting of oxygen octahedra leading to unit cell doubling and causing appearance of superlattice reflections which are observable in the electron and neutron diffraction patterns only and not in the XRD patterns, as a result of which Noheda and coworkers missed the Cc phase in their synchrotron XRD studies at low temperatures. Our findings were confirmed by leading groups using neutron, TEM, Raman and high pressure diffraction studies. The first principles calculations also confirmed that the true ground state of PZT in the MPB region has Cc space group. However, in the last couple of years, the Cc space group of the ground state has become controversial with an alternative proposal of R3c as the space group of the ground state phase which is proposed to coexist with the metastable Cm phase. In order to resolve this controversy, we recently revisited the issue using pure PZT and 6% Sr 2+ substituted PZT, the latter samples show larger tilt angle on account of the reduction in the average cationic radius at the Pb 2+ site. Using high wavelength neutrons and high

  13. Coherent-state representation for the QCD ground state

    International Nuclear Information System (INIS)

    Celenza, L.S.; Ji, C.; Shakin, C.M.

    1987-01-01

    We make use of the temporal gauge to construct a coherent state which is meant to describe the gluon condensate in the QCD vacuum under the assumption that the condensate is in a zero-momentum mode. The state so constructed is a color singlet and will yield finite, nonperturbative vacuum expectation values such as . (This matrix element is found to have a value of about 0.012 GeV 4 in QCD sum-rule studies.)

  14. Regionalization of ground motion attenuation in the conterminous United States

    International Nuclear Information System (INIS)

    Chung, D.H.; Bernreuter, D.L.

    1979-01-01

    Attenuation results from geometric spreading and from absorption. The former is almost independent of crustal geology or physiographic region. The latter depends strongly on crustal geology and the state of the earth's upper mantle. Except for very high-frequency waves, absorption does not affect ground motion at distances less than 25 to 50 km. Thus, in the near-field zone, the attenuation in the eastern United States will be similar to that in the western United States. Most of the differences in ground motion can be accounted for by differences in attenuation caused by differences in absorption. The other important factor is that for some Western earthquakes the fault breaks the earth's surface, resulting in larger ground motion. No Eastern earthquakes are known to have broken the earth's surface by faulting. The stress drop of Eastern earthquakes may be higher than for Western earthquakes of the same seismic moment, which would affect the high-frequency spectral content. This factor is believed to be of much less significance than differences in absorption in explaining the differences in ground motion between the East and the West. 6 figures

  15. Guidelines for ground motion definition for the eastern United States

    International Nuclear Information System (INIS)

    Gwaltney, R.C.; Aramayo, G.A.; Williams, R.T.

    1985-06-01

    Guidelines for the determination of earthquake ground motion definition for the eastern United States are established here. Both far-field and near-field guidelines are given. The guidelines were based on an extensive review of the current procedures for specifying ground motion in the United States. Both empirical and theoretical procedures were used in establishing the guidelines because of the low seismicity in the eastern United States. Only a few large- to great-sized earthquakes (M/sub s/ > 7.5) have occurred in this region, no evidence of tectonic surface ruptures related to historic or Holocene earthquakes has been found, and no currently active plate boundaries of any kind are known in this region. Very little instrumented data have been gathered in the East. Theoretical procedures are proposed so that in regions of almost no data, a reasonable level of seismic ground motion activity can be assumed. The guidelines are to be used to develop the safe shutdown earthquake (SSE). A new procedure for establishing the operating basis earthquake (OBE) is proposed, in particular for the eastern United States. The OBE would be developed using a probabilistic assessment of the geological conditions and the recurrence of seismic events at a site. These guidelines should be useful in development of seismic design requirements for future reactors. 17 refs., figs., tabs

  16. Moulting and wintering grounds of Marsh Warblers Acrocephalus palustris: evidence from stable isotopes and ring recoveries

    Czech Academy of Sciences Publication Activity Database

    Procházka, Petr; Kralj, J.; Pearson, D. J.; Yohannes, E.

    2014-01-01

    Roč. 49, č. 2 (2014), s. 193-200 ISSN 0001-6454 R&D Projects: GA ČR GA13-06451S Institutional support: RVO:68081766 Keywords : bird migration * feather stable isotopes * ring recoveries * stopover * migratory connectivity * δ13C * δ15N Subject RIV: EG - Zoology Impact factor: 0.745, year: 2014

  17. Satellite tracking and stable isotope analysis link wintering and feeding grounds of North Atlantic baleen whales

    NARCIS (Netherlands)

    e Silva, Monica Almeida; Prieto, Rui; Gauffier, Pauline; Palsboll, Per; Bérubé, Martine; Colaco, Ana

    2017-01-01

    Knowledge of the distribution of baleen whales throughout their annual cycle is critical for understanding their ecology, life history and behavior, and for their effective conservation. We combined analysis of stable isotopes (δ15N and δ13C) and satellite tracking data of blue (Balaenoptera

  18. Switching behavior and novel stable states of magnetic hexagonal nanorings

    Energy Technology Data Exchange (ETDEWEB)

    Yasir Rafique, M., E-mail: myasir.rafique@ciitlahore.edu.pk [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Pan, Liqing; Guo, Zhengang [College of Science and Research Institute for New Energy, China Three Gorges University, Yichang 443002 (China)

    2017-06-15

    Micromagnetic simulations for Cobalt hexagonal shape nanorings show onion (O) and vortex state (V) along with new state named “tri-domain state”. The tri-domain state is observed in sufficiently large width of ring. The magnetic reversible mechanism and transition of states are explained with help of vector field display. The transitions from one state to other occur by propagation of domain wall. The vertical parts of hexagonal rings play important role in developing the new “tri-domain” state. The behaviors of switching fields from onion to tri-domain (HO-Tr), tri-domain to vortex state (HTr-V) and vortex to onion state and “states size” are discussed in term of geometrical parameter of ring.

  19. STABLE ISOTOPE ANALYSIS OF MTBE TO EVALUATE THE SOURCE OF TBA IN GROUND WATER

    Science.gov (United States)

    Although tert-butyl alcohol (TBA) has not been used as a fuel oxygenate in Orange County, California, the concentrations of TBA in ground water at gasoline spill sites are high compared those of the conventional fuel oxygenate methyl tert-butyl ether (MTBE). In the year 2002, th...

  20. Cluster expansion for ground states of local Hamiltonians

    Directory of Open Access Journals (Sweden)

    Alvise Bastianello

    2016-08-01

    Full Text Available A central problem in many-body quantum physics is the determination of the ground state of a thermodynamically large physical system. We construct a cluster expansion for ground states of local Hamiltonians, which naturally incorporates physical requirements inherited by locality as conditions on its cluster amplitudes. Applying a diagrammatic technique we derive the relation of these amplitudes to thermodynamic quantities and local observables. Moreover we derive a set of functional equations that determine the cluster amplitudes for a general Hamiltonian, verify the consistency with perturbation theory and discuss non-perturbative approaches. Lastly we verify the persistence of locality features of the cluster expansion under unitary evolution with a local Hamiltonian and provide applications to out-of-equilibrium problems: a simplified proof of equilibration to the GGE and a cumulant expansion for the statistics of work, for an interacting-to-free quantum quench.

  1. Nuclear quadrupole moment of the 99Tc ground state

    International Nuclear Information System (INIS)

    Errico, Leonardo; Darriba, German; Renteria, Mario; Tang Zhengning; Emmerich, Heike; Cottenier, Stefaan

    2008-01-01

    By combining first-principles calculations and existing nuclear magnetic resonance (NMR) experiments, we determine the quadrupole moment of the 9/2 + ground state of 99 Tc to be (-)0.14(3)b. This confirms the value of -0.129(20)b, which is currently believed to be the most reliable experimental determination, and disagrees with two earlier experimental values. We supply ab initio calculated electric-field gradients for Tc in YTc 2 and ZrTc 2 . If this calculated information would be combined with yet to be performed Tc-NMR experiments in these compounds, the error bar on the 99 Tc ground state quadrupole moment could be further reduced

  2. Ground-state properties of a supersymmetric fermion chain

    International Nuclear Information System (INIS)

    Fendley, Paul; Hagendorf, Christian

    2011-01-01

    We analyze the ground state of a strongly interacting fermion chain with a supersymmetry. We conjecture a number of exact results, such as a hidden duality between weak and strong couplings. By exploiting a scale-free property of the perturbative expansions, we find exact expressions for the order parameters, yielding the critical exponents. We show that the ground state of this fermion chain and another model in the same universality class, the XYZ chain along a line of couplings, are both written in terms of the same polynomials. We demonstrate this explicitly for up to N = 24 sites and provide consistency checks for large N. These polynomials satisfy a recursion relation related to the Painlevé VI differential equation and, using a scale-free property of these polynomials, we derive a simple and exact formula for their N→∞ limit

  3. Photoionization of furan from the ground and excited electronic states.

    Science.gov (United States)

    Ponzi, Aurora; Sapunar, Marin; Angeli, Celestino; Cimiraglia, Renzo; Došlić, Nađa; Decleva, Piero

    2016-02-28

    Here we present a comparative computational study of the photoionization of furan from the ground and the two lowest-lying excited electronic states. The study aims to assess the quality of the computational methods currently employed for treating bound and continuum states in photoionization. For the ionization from the ground electronic state, we show that the Dyson orbital approach combined with an accurate solution of the continuum one particle wave functions in a multicenter B-spline basis, at the density functional theory (DFT) level, provides cross sections and asymmetry parameters in excellent agreement with experimental data. On the contrary, when the Dyson orbitals approach is combined with the Coulomb and orthogonalized Coulomb treatments of the continuum, the results are qualitatively different. In excited electronic states, three electronic structure methods, TDDFT, ADC(2), and CASSCF, have been used for the computation of the Dyson orbitals, while the continuum was treated at the B-spline/DFT level. We show that photoionization observables are sensitive probes of the nature of the excited states as well as of the quality of excited state wave functions. This paves the way for applications in more complex situations such as time resolved photoionization spectroscopy.

  4. Variational calculation for the ground state of 12C

    International Nuclear Information System (INIS)

    Consoni, L.H.A.; Coelho, H.T.; Das, T.K.

    1983-01-01

    A variational calculation is done for the ground state of a 3α-particle system. Two simple trial wavefunctions are used and results are compared with an exact calculation done by the Hyperspherical Harmonic method. A modifed Ali-Bodmer potential for the α-α interaction is considered for all calculations. It is found that these simple wave functions can be very useful for phenomenological calculations. (Author) [pt

  5. Bethe ansatz study for ground state of Fateev Zamolodchikov model

    International Nuclear Information System (INIS)

    Ray, S.

    1997-01-01

    A Bethe ansatz study of a self-dual Z N spin lattice model, originally proposed by V. A. Fateev and A. B. Zamolodchikov, is undertaken. The connection of this model to the Chiral Potts model is established. Transcendental equations connecting the zeros of Fateev endash Zamolodchikov transfer matrix are derived. The free energies for the ferromagnetic and the anti-ferromagnetic ground states are found for both even and odd spins. copyright 1997 American Institute of Physics

  6. Ground-state correlations within a nonperturbative approach

    Czech Academy of Sciences Publication Activity Database

    De Gregorio, G.; Herko, J.; Knapp, F.; Lo Iudice, N.; Veselý, Petr

    2017-01-01

    Roč. 95, č. 2 (2017), č. článku 024306. ISSN 2469-9985 R&D Projects: GA ČR GA13-07117S Institutional support: RVO:61389005 Keywords : ground state * harmonic oscillator frequency * space dimensions Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 3.820, year: 2016

  7. Ground state solutions for non-local fractional Schrodinger equations

    Directory of Open Access Journals (Sweden)

    Yang Pu

    2015-08-01

    Full Text Available In this article, we study a time-independent fractional Schrodinger equation with non-local (regional diffusion $$ (-\\Delta^{\\alpha}_{\\rho}u + V(xu = f(x,u \\quad \\text{in }\\mathbb{R}^{N}, $$ where $\\alpha \\in (0,1$, $N > 2\\alpha$. We establish the existence of a non-negative ground state solution by variational methods.

  8. Electronic and ground state properties of ThTe

    Energy Technology Data Exchange (ETDEWEB)

    Bhardwaj, Purvee, E-mail: purveebhardwaj@gmail.com; Singh, Sadhna, E-mail: drsadhna100@gmail.com [High Pressure Research Lab. Department of Physics Barkatullah University, Bhopal (MP) 462026 (India)

    2016-05-06

    The electronic properties of ThTe in cesium chloride (CsCl, B2) structure are investigated in the present paper. To study the ground state properties of thorium chalcogenide, the first principle calculations have been calculated. The bulk properties, including lattice constant, bulk modulus and its pressure derivative are obtained. The calculated equilibrium structural parameters are in good agreement with the available experimental and theoretical results.

  9. Ground state energy values and moments of the anharmonic oscillator

    International Nuclear Information System (INIS)

    Seetharaman, M.; Raghavan, Sekhar; Subba Rao, G.

    1981-01-01

    It is shown that a very satisfactory estimate of the energy values (for all values of the anharmonicity) and moments of the ground state of the quartic anharmonic oscillator can be obtained in the variational method, by considering trial wavefunctions which have the correct asymptotic properties. The results derived with a single variational parameter are a considerable improvement over the recent results of C.A. Ginsburg and E.W. Montroll (1978). (author)

  10. Ground states for light and heavy quark hadrons

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, J T [Physics Dept., Philippines Univ., Manila (Philippines)

    1994-01-01

    According to de Rujula et al. if the degenerate multiplet masses are known then it is not necessary to parametrize the interactions. With degenerate multiplet masses calculated from the spinorial decomposition of the SU(2)xSU(2) part of the SU(6)xSU(6) symmetry, the ground states for 3, 4 and 5 quark hadrons are calculated in terms of the Cartan matrix integers n[sub [alpha

  11. Ground state solutions for diffusion system with superlinear nonlinearity

    Directory of Open Access Journals (Sweden)

    Zhiming Luo

    2015-03-01

    where $z=(u,v\\colon\\mathbb{R}\\times\\mathbb{R}^{N}\\rightarrow\\mathbb{R}^{2}$, $b\\in C^{1}(\\mathbb{R}\\times\\mathbb{R}^{N}, \\mathbb{R}^{N}$ and $V(x\\in C(\\mathbb{R}^{N},\\mathbb{R}$. Under suitable assumptions on the nonlinearity, we establish the existence of ground state solutions by the generalized Nehari manifold method developed recently by Szulkin and Weth.

  12. Highly twisted 1,2:8,9-dibenzozethrenes: Synthesis, ground state, and physical properties

    KAUST Repository

    Sun, Zhe; Zheng, Bin; Hu, Pan; Huang, Kuo-Wei; Wu, Jishan

    2014-01-01

    Two soluble and stable 1,2:8,9-dibenzozethrene derivatives (3a,b) are synthesized through a palladium-catalyzed cyclodimerization reaction. X-ray crystallographic analysis shows that these molecules are highly twisted owing to congestion at the cove region. Broken-symmetry DFT calculations predict that they have a singlet biradical ground state with a smaller biradical character and a large singlet-triplet energy gap; these predictions are supported by NMR and electronic absorption measurements. They have small energy gaps and exhibit farred/near-infrared absorption/emission and amphoteric redox behaviors.

  13. Highly twisted 1,2:8,9-dibenzozethrenes: Synthesis, ground state, and physical properties

    KAUST Repository

    Sun, Zhe

    2014-08-08

    Two soluble and stable 1,2:8,9-dibenzozethrene derivatives (3a,b) are synthesized through a palladium-catalyzed cyclodimerization reaction. X-ray crystallographic analysis shows that these molecules are highly twisted owing to congestion at the cove region. Broken-symmetry DFT calculations predict that they have a singlet biradical ground state with a smaller biradical character and a large singlet-triplet energy gap; these predictions are supported by NMR and electronic absorption measurements. They have small energy gaps and exhibit farred/near-infrared absorption/emission and amphoteric redox behaviors.

  14. Kohn-Sham Theory for Ground-State Ensembles

    International Nuclear Information System (INIS)

    Ullrich, C. A.; Kohn, W.

    2001-01-01

    An electron density distribution n(r) which can be represented by that of a single-determinant ground state of noninteracting electrons in an external potential v(r) is called pure-state v -representable (P-VR). Most physical electronic systems are P-VR. Systems which require a weighted sum of several such determinants to represent their density are called ensemble v -representable (E-VR). This paper develops formal Kohn-Sham equations for E-VR physical systems, using the appropriate coupling constant integration. It also derives local density- and generalized gradient approximations, and conditions and corrections specific to ensembles

  15. Sideband cooling of micromechanical motion to the quantum ground state.

    Science.gov (United States)

    Teufel, J D; Donner, T; Li, Dale; Harlow, J W; Allman, M S; Cicak, K; Sirois, A J; Whittaker, J D; Lehnert, K W; Simmonds, R W

    2011-07-06

    The advent of laser cooling techniques revolutionized the study of many atomic-scale systems, fuelling progress towards quantum computing with trapped ions and generating new states of matter with Bose-Einstein condensates. Analogous cooling techniques can provide a general and flexible method of preparing macroscopic objects in their motional ground state. Cavity optomechanical or electromechanical systems achieve sideband cooling through the strong interaction between light and motion. However, entering the quantum regime--in which a system has less than a single quantum of motion--has been difficult because sideband cooling has not sufficiently overwhelmed the coupling of low-frequency mechanical systems to their hot environments. Here we demonstrate sideband cooling of an approximately 10-MHz micromechanical oscillator to the quantum ground state. This achievement required a large electromechanical interaction, which was obtained by embedding a micromechanical membrane into a superconducting microwave resonant circuit. To verify the cooling of the membrane motion to a phonon occupation of 0.34 ± 0.05 phonons, we perform a near-Heisenberg-limited position measurement within (5.1 ± 0.4)h/2π, where h is Planck's constant. Furthermore, our device exhibits strong coupling, allowing coherent exchange of microwave photons and mechanical phonons. Simultaneously achieving strong coupling, ground state preparation and efficient measurement sets the stage for rapid advances in the control and detection of non-classical states of motion, possibly even testing quantum theory itself in the unexplored region of larger size and mass. Because mechanical oscillators can couple to light of any frequency, they could also serve as a unique intermediary for transferring quantum information between microwave and optical domains.

  16. Stable amplitude chimera states in a network of locally coupled Stuart-Landau oscillators

    Science.gov (United States)

    Premalatha, K.; Chandrasekar, V. K.; Senthilvelan, M.; Lakshmanan, M.

    2018-03-01

    We investigate the occurrence of collective dynamical states such as transient amplitude chimera, stable amplitude chimera, and imperfect breathing chimera states in a locally coupled network of Stuart-Landau oscillators. In an imperfect breathing chimera state, the synchronized group of oscillators exhibits oscillations with large amplitudes, while the desynchronized group of oscillators oscillates with small amplitudes, and this behavior of coexistence of synchronized and desynchronized oscillations fluctuates with time. Then, we analyze the stability of the amplitude chimera states under various circumstances, including variations in system parameters and coupling strength, and perturbations in the initial states of the oscillators. For an increase in the value of the system parameter, namely, the nonisochronicity parameter, the transient chimera state becomes a stable chimera state for a sufficiently large value of coupling strength. In addition, we also analyze the stability of these states by perturbing the initial states of the oscillators. We find that while a small perturbation allows one to perturb a large number of oscillators resulting in a stable amplitude chimera state, a large perturbation allows one to perturb a small number of oscillators to get a stable amplitude chimera state. We also find the stability of the transient and stable amplitude chimera states and traveling wave states for an appropriate number of oscillators using Floquet theory. In addition, we also find the stability of the incoherent oscillation death states.

  17. Study of ground state optical transfer for ultracold alkali dimers

    Science.gov (United States)

    Bouloufa-Maafa, Nadia; Londono, Beatriz; Borsalino, Dimitri; Vexiau, Romain; Mahecha, Jorge; Dulieu, Olivier; Luc-Koenig, Eliane

    2013-05-01

    Control of molecular states by laser pulses offer promising potential applications. The manipulation of molecules by external fields requires precise knowledge of the molecular structure. Our motivation is to perform a detailed analysis of the spectroscopic properties of alkali dimers, with the aim to determine efficient optical paths to form molecules in the absolute ground state and to determine the optimal parameters of the optical lattices where those molecules are manipulated to avoid losses by collisions. To this end, we use state of the art molecular potentials, R-dependent spin-orbit coupling and transition dipole moment to perform our calculations. R-dependent SO coupling are of crucial importance because the transitions occur at internuclear distances where they are affected by this R-dependence. Efficient schemes to transfer RbCs, KRb and KCs to the absolute ground state as well as the optimal parameters of the optical lattices will be presented. This work was supported in part by ``Triangle de la Physique'' under contract 2008-007T-QCCM (Quantum Control of Cold Molecules).

  18. Stable Isotopes Reveal Long-Term Fidelity to Foraging Grounds in the Galapagos Sea Lion (Zalophus wollebaeki.

    Directory of Open Access Journals (Sweden)

    Massimiliano Drago

    Full Text Available Most otariids have colony-specific foraging areas during the breeding season, when they behave as central place foragers. However, they may disperse over broad areas after the breeding season and individuals from different colonies may share foraging grounds at that time. Here, stable isotope ratios in the skull bone of adult Galapagos sea lions (Zalophus wollebaeki were used to assess the long-term fidelity of both sexes to foraging grounds across the different regions of the Galapagos archipelago. Results indicated that the stable isotope ratios (δ(13C and δ(15N of sea lion bone significantly differed among regions of the archipelago, without any significant difference between sexes and with a non significant interaction between sex and region. Moreover, standard ellipses, estimated by Bayesian inference and used as a measure of the isotopic resource use area at the population level, overlapped widely for the sea lions from the southern and central regions, whereas the overlap of the ellipses for sea lions from the central and western regions was small and non-existing for those from the western and southern regions. These results suggest that males and females from the same region within the archipelago use similar foraging grounds and have similar diets. Furthermore, they indicate that the exchange of adults between regions is limited, thus revealing a certain degree of foraging philopatry at a regional scale within the archipelago. The constraints imposed on males by an expanded reproductive season (~ 6 months, resulting from the weak reproductive synchrony among females, and those imposed on females by a very long lactation period (at least one year but up to three years, may explain the limited mobility of adult Galapagos sea lions of both sexes across the archipelago.

  19. On stable ground: Tackling soil erosion with nuclear techniques in Viet Nam

    International Nuclear Information System (INIS)

    Gaspar, Miklos

    2015-01-01

    Dao Thanh Canh never studied physics or chemistry in school, but he understands a thing or two about nuclear isotopes. Until a couple of years ago, much of his five acre farm on the hills of central Viet Nam was gradually sliding away. Thanks to nuclear techniques used in determining the exact cause and source of soil erosion, his land is now stable, and his coffee plantation profitable. “We were very worried as uncertainty loomed,” he said. “A few centimetres of the soil disappeared every year when we had big hail storms.” Thanh Canh is not alone. Soil degradation affects 1.9 billion hectares of land worldwide, close to two thirds of global soil resources.

  20. From the ground up: global nitrous oxide sources are constrained by stable isotope values.

    Directory of Open Access Journals (Sweden)

    David M Snider

    Full Text Available Rising concentrations of nitrous oxide (N2O in the atmosphere are causing widespread concern because this trace gas plays a key role in the destruction of stratospheric ozone and it is a strong greenhouse gas. The successful mitigation of N2O emissions requires a solid understanding of the relative importance of all N2O sources and sinks. Stable isotope ratio measurements (δ15N-N2O and δ18O-N2O, including the intramolecular distribution of 15N (site preference, are one way to track different sources if they are isotopically distinct. 'Top-down' isotope mass-balance studies have had limited success balancing the global N2O budget thus far because the isotopic signatures of soil, freshwater, and marine sources are poorly constrained and a comprehensive analysis of global N2O stable isotope measurements has not been done. Here we used a robust analysis of all available in situ measurements to define key global N2O sources. We showed that the marine source is isotopically distinct from soil and freshwater N2O (the continental source. Further, the global average source (sum of all natural and anthropogenic sources is largely controlled by soils and freshwaters. These findings substantiate past modelling studies that relied on several assumptions about the global N2O cycle. Finally, a two-box-model and a Bayesian isotope mixing model revealed marine and continental N2O sources have relative contributions of 24-26% and 74-76% to the total, respectively. Further, the Bayesian modeling exercise indicated the N2O flux from freshwaters may be much larger than currently thought.

  1. Energy of ground state of laminar electron-hole liquid

    International Nuclear Information System (INIS)

    Andryushin, E.A.

    1976-01-01

    The problem of a possible existence of metal electron-hole liquid in semiconductors is considered. The calculation has been carried out for the following model: two parallel planes are separated with the distance on one of the planes electrons moving, on the other holes doing. Transitions between the planes are forbidden. The density of particles for both planes is the same. The energy of the ground state and correlation functions for such electron-and hole system are calculated. It is shown that the state of a metal liquid is more advantageous against the exciton gas. For the mass ratio of electrons and holes, msub(e)/msub(h) → 0 a smooth rearrangement of the system into a state with ordered heavy particles is observed

  2. Symmetry Breakdown in Ground State Dissociation of HD+

    International Nuclear Information System (INIS)

    Ben-Itzhak, I.; Wells, E.; Carnes, K. D.; Krishnamurthi, Vidhya; Weaver, O. L.; Esry, B. D.

    2000-01-01

    Experimental studies of the dissociation of the electronic ground state of HD + following ionization of HD by fast proton impact indicate that the H + +D 1s dissociation channel is more likely than the H1s+D + dissociation channel by about 7% . This isotopic symmetry breakdown is due to the finite nuclear mass correction to the Born-Oppenheimer approximation which makes the 1sσ state 3.7 meV lower than the 2pσ state at the dissociation limit. The measured fractions of the two dissociation channels are in agreement with coupled-channels calculations of 1sσ to 2pσ transitions. (c) 2000 The American Physical Society

  3. Stable isotope study of ground water recharge and movement in the Shogawa Fan, Toyama

    International Nuclear Information System (INIS)

    Mizutani, Yoshihiko; Oda, Matsuhisa

    1983-01-01

    Deuterium and oxygen-18 measurements of ground and river waters of the Shogawa Fan, Toyama, have been used to identify sources of water in aquifers in the Fan. A significant difference exists in deltaD and delta 18 O values between two major rivers flowing onto the Fan. On the basis of this difference, it is indicated that aquifers in the eastern half of the Fan are recharged from the Sho River and those in the western half of the Fan are from the Oyabe River. Chloride measurements of the waters support this identification of water sources. Contributions of other water sources to the aquifers are also indicated. The flow rate of infiltration from the Sho River is estimated to be 10-13 m/day in the confined aquifers in the northern part of the Fan. (author)

  4. Robust chaos synchronization using input-to-state stable control

    Indian Academy of Sciences (India)

    ... be obtained by solving a convex optimization problem represented by the. LMI. Simulation studies are presented to demonstrate the effectiveness of the proposed ... one is the linear state feedback controller and the other is the nonlinear feedback controller. By the proposed control scheme, the closed-loop error system is ...

  5. Ground state energies from converging and diverging power series expansions

    International Nuclear Information System (INIS)

    Lisowski, C.; Norris, S.; Pelphrey, R.; Stefanovich, E.; Su, Q.; Grobe, R.

    2016-01-01

    It is often assumed that bound states of quantum mechanical systems are intrinsically non-perturbative in nature and therefore any power series expansion methods should be inapplicable to predict the energies for attractive potentials. However, if the spatial domain of the Schrödinger Hamiltonian for attractive one-dimensional potentials is confined to a finite length L, the usual Rayleigh–Schrödinger perturbation theory can converge rapidly and is perfectly accurate in the weak-binding region where the ground state’s spatial extension is comparable to L. Once the binding strength is so strong that the ground state’s extension is less than L, the power expansion becomes divergent, consistent with the expectation that bound states are non-perturbative. However, we propose a new truncated Borel-like summation technique that can recover the bound state energy from the diverging sum. We also show that perturbation theory becomes divergent in the vicinity of an avoided-level crossing. Here the same numerical summation technique can be applied to reproduce the energies from the diverging perturbative sums.

  6. Ground state energies from converging and diverging power series expansions

    Energy Technology Data Exchange (ETDEWEB)

    Lisowski, C.; Norris, S.; Pelphrey, R.; Stefanovich, E., E-mail: eugene-stefanovich@usa.net; Su, Q.; Grobe, R.

    2016-10-15

    It is often assumed that bound states of quantum mechanical systems are intrinsically non-perturbative in nature and therefore any power series expansion methods should be inapplicable to predict the energies for attractive potentials. However, if the spatial domain of the Schrödinger Hamiltonian for attractive one-dimensional potentials is confined to a finite length L, the usual Rayleigh–Schrödinger perturbation theory can converge rapidly and is perfectly accurate in the weak-binding region where the ground state’s spatial extension is comparable to L. Once the binding strength is so strong that the ground state’s extension is less than L, the power expansion becomes divergent, consistent with the expectation that bound states are non-perturbative. However, we propose a new truncated Borel-like summation technique that can recover the bound state energy from the diverging sum. We also show that perturbation theory becomes divergent in the vicinity of an avoided-level crossing. Here the same numerical summation technique can be applied to reproduce the energies from the diverging perturbative sums.

  7. Ground-State Structures of Ice at High-Pressures

    OpenAIRE

    McMahon, Jeffrey M.

    2011-01-01

    \\textit{Ab initio} random structure searching based on density functional theory is used to determine the ground-state structures of ice at high pressures. Including estimates of lattice zero-point energies, ice is found to adopt three novel crystal phases. The underlying sub-lattice of O atoms remains similar among them, and the transitions can be characterized by reorganizations of the hydrogen bonds. The symmetric hydrogen bonds of ice X and $Pbcm$ are initially lost as ice transforms to s...

  8. Spectroscopic factor of the 7He ground state

    International Nuclear Information System (INIS)

    Beck, F.; Frekers, D.; Neumann-Cosel, P. von; Richter, A.; Ryezayeva, N.; Thompson, I.J.

    2007-01-01

    The neutron spectroscopic factor S n of the 7 He ground state is extracted from an R-matrix analysis of a recent measurement of the 7 Li(d, 2 He) 7 He reaction with good energy resolution. The width extracted from a deconvolution of the spectrum is Γ=183(22) keV (full width at half maximum, FWHM). The result S n =0.64(9) is slightly larger than predictions of recent 'ab initio' Green's function Monte Carlo and fermionic molecular dynamics calculations

  9. Variational Monte Carlo calculations of nuclear ground states

    International Nuclear Information System (INIS)

    Wiringa, R.B.

    1990-01-01

    A major goal in nuclear physics is to understand how nuclear structure comes about from the underlying interactions between nucleons. This requires modelling nuclei as collections of strongly interacting nucleons. We start with realistic nucleon-nucleon potentials, supplemented with consistent three-nucleon potentials and two-body electroweak current operators, and try to predict nuclear ground properties, such as the binding energy, density and momentum distributions, and electromagnetic form factors. We also seek to predict other properties of nuclei such as excited states and low-energy reactions. 21 refs., 14 figs., 5 tabs

  10. Electron scattering from the ground state of mercury

    International Nuclear Information System (INIS)

    Fursa, D.; Bray, I.

    2000-01-01

    Full text: Close-coupling calculations have been performed for electron scattering from the ground state of mercury. We have used non-relativistic convergent close-coupling computer code with only minor modifications in order to account for the most prominent relativistic effects. These are the relativistic shift effect and singlet-triplet mixing. Very good agreement with measurements of differential cross sections for elastic scattering and excitation of 6s6p 1 P state at all energies is obtained. It is well recognised that a consistent approach to electron scattering from heavy atoms (like mercury, with nuclear charge Z=80) must be based on a fully relativistic Dirac equations based technique. While development of such technique is under progress in our group, the complexity of the problem ensures that results will not be available in the near future. On other hand, there is considerable interest in reliable theoretical results for electron scattering from heavy atoms from both applications and the need to interpret existing experimental data. This is particularly the case for mercury, which is the major component in fluorescent lighting devices and has been the subject of intense experimental study since nineteen thirties. Similarly to our approach for alkaline-earth atoms we use a model of two valence electrons above an inert Hartree-Fock core to describe the mercury atom. Note that this model does not account for any core excited states which are present in the mercury discrete spectrum. The major effect of missing core-excited states is substantial underestimation of the static dipole polarizability of the mercury ground state (34 a.u.) and consequent underestimation of the forward scattering elastic cross sections. We correct for this by adding in the scattering calculations a phenomenological polarization potential. In order to obtain correct ground state ionization energy for mercury one has to account for the relativistic shift effect. We model this

  11. Cluster decay of Ba isotopes from ground state and as an excited ...

    Indian Academy of Sciences (India)

    otherwise, inclusion of excitation energy decreases the T1/2 values. ... penetrates the nuclear barrier and reaches scission configuration after running .... between the ground-state energy levels of the parent nuclei and the ground-state energy.

  12. Stable hydrogen isotopes record the summering grounds of eastern red bats (Lasiurus borealis

    Directory of Open Access Journals (Sweden)

    Cortney L. Pylant

    2014-10-01

    Full Text Available Bats face numerous threats associated with global environmental change, including the rapid expansion of wind-energy facilities, emerging infectious disease, and habitat loss. An understanding of the movement and migration patterns of these highly dispersive animals would help reveal how spatially localized the impacts from these threats are likely to be on bat populations, thus aiding in their conservation. Stable hydrogen isotope ratios (δ2H can be used to infer regions where bats have foraged during the summer molt season, thus allowing an assessment of summering location and distance of movement of bats sampled during other times of year. However, a major impediment to the application of δ2H for inference of bat movements is that the relationship between δ2H of bat hair and precipitation tends to be species specific and is still unknown for some key species of conservation concern. We addressed this issue by using geo-referenced museum specimens to calibrate the relationship between δ2H of hair (δ2Hhair and long-term δ2H of growing-season precipitation (δ2HGSprecip at the site of collection for eastern red bats (Lasiurus borealis, one of the main species of bats experiencing large numbers of fatalities at wind-energy facilities in North America. Based on comparison of δ2Hhair and δ2HGSprecip values for males we estimated a period of molt of June 14–August 7. Within this period, male and female red bats exhibited a significant positive relationship between δ2Hhair and δ2HGSprecip. These results establish the relationship between δ2Hhair and δ2HGSprecip for red bats, which is necessary for the use of δ2Hhair to infer the movement and migration patterns of this important species. These results provide a critical resource to conservation biologists working to assess the impacts of environmental change on bat populations.

  13. Centrifugal stretching along the ground state band of 168Hf

    International Nuclear Information System (INIS)

    Costin, A.; Pietralla, N.; Reese, M.; Moeller, O.; Ai, H.; Casten, R. F.; Heinz, A.; McCutchan, E. A.; Meyer, D. A.; Qian, J.; Werner, V.; Dusling, K.; Fitzpatrick, C. R.; Guerdal, G.; Petkov, P.; Rainovski, G.

    2009-01-01

    The lifetimes of the J π =4 + , 6 + , 8 + , and 10 + levels along the ground state band in 168 Hf were measured by means of the recoil distance Doppler shift (RDDS) method using the New Yale Plunger Device (NYPD) and the SPEEDY detection array at Wright Nuclear Structure Laboratory of Yale University. Excited states in 168 Hf were populated using the 124 Sn( 48 Ti,4n) fusion evaporation reaction. The new lifetime values are sufficiently precise to clearly prove the increase of quadrupole deformation as a function of angular momentum in the deformed nucleus 168 Hf. The data agree with the predictions from the geometrical confined β-soft (CBS) rotor model that involves centrifugal stretching in a soft potential

  14. Line list for the ground state of CaF

    Science.gov (United States)

    Hou, Shilin; Bernath, Peter F.

    2018-05-01

    The molecular potential energy function and electronic dipole moment function for the ground state of CaF were studied with MRCI, ACPF, and RCCSD(T) ab initio calculations. The RCCSD(T) potential function reproduces the experimental vibrational intervals to within ∼2 cm-1. The RCCSD(T) dipole moment at the equilibrium internuclear separation agrees well with the experimental value. Over a wide range of internuclear separations, far beyond the range associated with the observed spectra, the ab initio dipole moment functions are similar and highly linear. An extended Morse oscillator (EMO) potential function was also obtained by fitting the observed lines of the laboratory vibration-rotation and pure rotation spectra of the 40CaF X2Σ+ ground state. The fitted potential reproduces the observed transitions (v ≤ 8, N ≤ 121, Δv = 0, 1) within their experimental uncertainties. With this EMO potential and the RCCSD(T) dipole moment function, line lists for 40CaF, 42CaF, 43CaF, 44CaF, 46CaF, and 48CaF were computed for v ≤ 10, N ≤ 121, Δv = 0-10. The calculated emission spectra are in good agreement with an observed laboratory spectrum of CaF at a sample temperature of 1873 K.

  15. A new representation for ground states and its Legendre transforms

    International Nuclear Information System (INIS)

    Cedillo, A.

    1994-01-01

    The ground-state energy of an electronic system is a functional of the number of electrons (N) and the external potential (v): E = E(N,V), this is the energy representation for ground states. In 1982, Nalewajski defined the Legendre transforms of this representation, taking advantage of the strict concavity of E with respect to their variables (concave respect v and convex respect N), and he also constructed a scheme for the reduction of derivatives of his representations. Unfortunately, N and the electronic density (p) were the independent variables of one of these representations, but p depends explicitly on N. In this work, this problem is avoided using the energy per particle (ε) as the basic variables, and the Legendre transformations can be defined. A procedure for the reduction of derivatives is generated for the new four representations and, in contrast to the Nalewajski's procedure, it only includes derivatives of the four representations. Finally, the reduction of derivatives is used to test some relationships between the hardness and softness kernels

  16. Characterization of design ground motion for the central and eastern United States: licensing implications

    International Nuclear Information System (INIS)

    Litehiser, J.; Carrato, P.

    2005-01-01

    For the first time in decades several US utilities are exploring the possibility of building new Nuclear Power Plant (NPP) generating capacity in the Central and Eastern United States (CEUS). Among the many topics that must be considered to license a nuclear plant (NPP) is appropriate design to mitigate the potential effects of vibratory ground motion from earthquakes. Agreement on seismic design ground motion was not always easy during licensing of the last generation of NPPs. Therefore, over the last few decades both industry and the United States Nuclear Regulatory Commission (USNRC) have worked to find ground motion criteria that recognize and overcome earlier licensing difficulties. Such criteria should be stable and easily implemented. Important and complementary programs under the direction of the Lawrence Livermore National Laboratory (LLNL) and the Electric Power Research Institute (EPRI) were part of this effort, and these studies resulted in probabilistic seismic hazard assessments (PSHAs) for a number of CEUS NPP sites. These results and the concepts underlying them are now incorporated into both USNRC regulation and regulatory guidance. Nevertheless, as the utilities and the NRC begin a renewed licensing dialog, issues of regulatory interpretation of earthquake ground motion design criteria have emerged. These issues are as fundamental as the shape and amplitude of ground motion design response spectra and as significant as the impact of these spectra on structural design. Successful and timely resolution of these issues will significantly impact the future of nuclear power in the US. The purpose of this paper is to briefly describe some of these issues and the approaches that have been proposed for their resolution. (authors)

  17. Hematopoietic differentiation: a coordinated dynamical process towards attractor stable states

    Directory of Open Access Journals (Sweden)

    Rossi Simona

    2010-06-01

    Full Text Available Abstract Background The differentiation process, proceeding from stem cells towards the different committed cell types, can be considered as a trajectory towards an attractor of a dynamical process. This view, taking into consideration the transcriptome and miRNome dynamics considered as a whole, instead of looking at few 'master genes' driving the system, offers a novel perspective on this phenomenon. We investigated the 'differentiation trajectories' of the hematopoietic system considering a genome-wide scenario. Results We developed serum-free liquid suspension unilineage cultures of cord blood (CB CD34+ hematopoietic progenitor cells through erythroid (E, megakaryocytic (MK, granulocytic (G and monocytic (Mo pathways. These cultures recapitulate physiological hematopoiesis, allowing the analysis of almost pure unilineage precursors starting from initial differentiation of HPCs until terminal maturation. By analyzing the expression profile of protein coding genes and microRNAs in unilineage CB E, MK, G and Mo cultures, at sequential stages of differentiation and maturation, we observed a coordinated, fully interconnected and scalable character of cell population behaviour in both transcriptome and miRNome spaces reminiscent of an attractor-like dynamics. MiRNome and transcriptome space differed for a still not terminally committed behaviour of microRNAs. Conclusions Consistent with their roles, the transcriptome system can be considered as the state space of a cell population, while the continuously evolving miRNA space corresponds to the tuning system necessary to reach the attractor. The behaviour of miRNA machinery could be of great relevance not only for the promise of reversing the differentiated state but even for tumor biology.

  18. Ground state analysis of magnetic nanographene molecules with modified edge

    International Nuclear Information System (INIS)

    Gorjizadeh, Narjes; Ota, Norio; Kawazoe, Yoshiyuki

    2013-01-01

    Highlights: ► Graphene molecules can become ferromagnetic by edge modifications. ► Dihydrogenation of one zigzag edge of rectangular flakes make them ferromagnetic. ► Triangular flakes become high-spin state by dehydrogenization of one zigzag edge. - Abstract: We study spin states of edge modified nanographene molecules with rectangular and triangular shapes by first principle calculations using density functional theory (DFT) and Hartree–Fock (HF) methods with Møller–Plesset (MP) correlation energy correction at different levels. Anthracene (C 14 H 10 ) and phenalenyl (C 13 H 9 ), which contain three benzene rings combined in two different ways, can be considered as fragments of a graphene sheet. Carbon-based ferromagnetic materials are of great interest both in fundamental science and technological potential in organic spintronics devices. We show that non-magnetic rectangular molecules such as C 14 H 10 can become ferromagnetic with high-spin state as the ground state by dihydrogenization of one of the zigzag edges, while triangular molecules such as C 13 H 9 become ferromagnetic with high-spin state by dehydrogenization of one of the zigzag edges

  19. The relation between the (N) and (N-1) electrons atomic ground state

    International Nuclear Information System (INIS)

    Briet, P.

    1984-05-01

    The relation between the ground state of an N and (N-1) electrons atomic system are studied. We show that in some directions of the configuration space, the ratio of the N electrons atomic ground state to the one particle density is asymptotically equivalent to the (N-1) electrons atomic ground state

  20. Ground state configurations in antiferromagnetic ultrathin films with dipolar anisotropy

    International Nuclear Information System (INIS)

    León, H.

    2013-01-01

    The formalism developed in a previous work to calculate the dipolar energy in quasi-two-dimensional crystals with ferromagnetic order is now extended to collinear antiferromagnetic order. Numerical calculations of the dipolar energy are carried out for systems with tetragonally distorted fcc [001] structures, the case of NiO and MnO ultrathin film grown in non-magnetic substrates, where the magnetic phase is a consequence of superexchange and dipolar interactions. The employed approximation allows to demonstrate that dipolar coupling between atomic layers is responsible for the orientation of the magnetization when it differs from the one in a single layer. The ground state energy of a given NiO or MnO film is found to depend not only on the strain, but also on how much the interlayer separation and the 2D lattice constant are changed with respect to the ideal values corresponding to the non-distorted cubic structure. Nevertheless, it is shown that the orientation of the magnetization in the magnetic phase of any of these films is determined by the strain exclusively. A striped phase with the magnetization along the [112 ¯ ] direction appears as the ground state configuration of NiO and MnO ultrathin films. In films with equally oriented stripes along the layers this magnetic phase is twofold degenerate, while in films with multidomain layers it is eightfold degenerate. These results are not in contradiction with experimentally observed out-of-plane or in-plane magnetization of striped phases in NiO and MnO ultrathin films. - Highlights: ► Dipolar energy in collinear antiferromagnetic ultrathin films is calculated. ► Numerical results are presented for distorted fcc [001] structures. ► The lowest energy of a system depends on how the tetragonal distortion is achieved. ► A striped phase with magnetization in the [112 ¯ ] direction is the ground state. ► In multidomain NiO and MnO films it is eightfold degenerate.

  1. Alternative stable states and the sustainability of forests, grasslands, and agriculture

    Science.gov (United States)

    Henderson, Kirsten A.; Bauch, Chris T.; Anand, Madhur

    2016-01-01

    Endangered forest–grassland mosaics interspersed with expanding agriculture and silviculture occur across many parts of the world, including the southern Brazilian highlands. This natural mosaic ecosystem is thought to reflect alternative stable states driven by threshold responses of recruitment to fire and moisture regimes. The role of adaptive human behavior in such systems remains understudied, despite its pervasiveness and the fact that such ecosystems can exhibit complex dynamics. We develop a nonlinear mathematical model of coupled human–environment dynamics in mosaic systems and social processes regarding conservation and economic land valuation. Our objective is to better understand how the coupled dynamics respond to changes in ecological and social conditions. The model is parameterized with southern Brazilian data on mosaic ecology, land-use profits, and questionnaire results concerning landowner preferences and conservation values. We find that the mosaic presently resides at a crucial juncture where relatively small changes in social conditions can generate a wide variety of possible outcomes, including complete loss of mosaics; large-amplitude, long-term oscillations between land states that preclude ecosystem stability; and conservation of the mosaic even to the exclusion of agriculture/silviculture. In general, increasing the time horizon used for conservation decision making is more likely to maintain mosaic stability. In contrast, increasing the inherent conservation value of either forests or grasslands is more likely to induce large oscillations—especially for forests—due to feedback from rarity-based conservation decisions. Given the potential for complex dynamics, empirically grounded nonlinear dynamical models should play a larger role in policy formulation for human–environment mosaic ecosystems. PMID:27956605

  2. Alternative stable states and the sustainability of forests, grasslands, and agriculture.

    Science.gov (United States)

    Henderson, Kirsten A; Bauch, Chris T; Anand, Madhur

    2016-12-20

    Endangered forest-grassland mosaics interspersed with expanding agriculture and silviculture occur across many parts of the world, including the southern Brazilian highlands. This natural mosaic ecosystem is thought to reflect alternative stable states driven by threshold responses of recruitment to fire and moisture regimes. The role of adaptive human behavior in such systems remains understudied, despite its pervasiveness and the fact that such ecosystems can exhibit complex dynamics. We develop a nonlinear mathematical model of coupled human-environment dynamics in mosaic systems and social processes regarding conservation and economic land valuation. Our objective is to better understand how the coupled dynamics respond to changes in ecological and social conditions. The model is parameterized with southern Brazilian data on mosaic ecology, land-use profits, and questionnaire results concerning landowner preferences and conservation values. We find that the mosaic presently resides at a crucial juncture where relatively small changes in social conditions can generate a wide variety of possible outcomes, including complete loss of mosaics; large-amplitude, long-term oscillations between land states that preclude ecosystem stability; and conservation of the mosaic even to the exclusion of agriculture/silviculture. In general, increasing the time horizon used for conservation decision making is more likely to maintain mosaic stability. In contrast, increasing the inherent conservation value of either forests or grasslands is more likely to induce large oscillations-especially for forests-due to feedback from rarity-based conservation decisions. Given the potential for complex dynamics, empirically grounded nonlinear dynamical models should play a larger role in policy formulation for human-environment mosaic ecosystems.

  3. Stability of quantum-dot excited-state laser emission under simultaneous ground-state perturbation

    Energy Technology Data Exchange (ETDEWEB)

    Kaptan, Y., E-mail: yuecel.kaptan@physik.tu-berlin.de; Herzog, B.; Schöps, O.; Kolarczik, M.; Woggon, U.; Owschimikow, N. [Institut für Optik und Atomare Physik, Technische Universität Berlin, Berlin (Germany); Röhm, A.; Lingnau, B.; Lüdge, K. [Institut für Theoretische Physik, Technische Universität Berlin, Berlin (Germany); Schmeckebier, H.; Arsenijević, D.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Berlin (Germany); Mikhelashvili, V.; Eisenstein, G. [Technion Institute of Technology, Faculty of Electrical Engineering, Haifa (Israel)

    2014-11-10

    The impact of ground state amplification on the laser emission of In(Ga)As quantum dot excited state lasers is studied in time-resolved experiments. We find that a depopulation of the quantum dot ground state is followed by a drop in excited state lasing intensity. The magnitude of the drop is strongly dependent on the wavelength of the depletion pulse and the applied injection current. Numerical simulations based on laser rate equations reproduce the experimental results and explain the wavelength dependence by the different dynamics in lasing and non-lasing sub-ensembles within the inhomogeneously broadened quantum dots. At high injection levels, the observed response even upon perturbation of the lasing sub-ensemble is small and followed by a fast recovery, thus supporting the capacity of fast modulation in dual-state devices.

  4. Liquid 4He: Modified LOCV ground-state energy calculations

    International Nuclear Information System (INIS)

    Skjetne, B.; Ostgaard, E.

    1996-01-01

    The ground-state energetics of liquid 4 He is studied in a constrained variational approach, where the significance of neglecting terms beyond second order in the cluster expansion is estimated in a crude way. An adjustment to the conditions of healing on the two-body correlation function excludes from the global average field the effects of pairwise clustering to higher orders. To this end, open-quotes virtualclose quotes particles beyond nearest neighbors are included in the average correlation volume. Results within the scope of such modifications are consistent with GFMC and QDMC calculations, falling within the range -7.25 ± 0.05 K when recent interaction models are used

  5. Ground-state properties of neutron magic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Saxena, G., E-mail: gauravphy@gmail.com [Govt. Women Engineering College, Department of Physics (India); Kaushik, M. [Shankara Institute of Technology, Department of Physics (India)

    2017-03-15

    A systematic study of the ground-state properties of the entire chains of even–even neutron magic nuclei represented by isotones of traditional neutron magic numbers N = 8, 20, 40, 50, 82, and 126 has been carried out using relativistic mean-field plus Bardeen–Cooper–Schrieffer approach. Our present investigation includes deformation, binding energy, two-proton separation energy, single-particle energy, rms radii along with proton and neutron density profiles, etc. Several of these results are compared with the results calculated using nonrelativistic approach (Skyrme–Hartree–Fock method) along with available experimental data and indeed they are found with excellent agreement. In addition, the possible locations of the proton and neutron drip-lines, the (Z, N) values for the new shell closures, disappearance of traditional shell closures as suggested by the detailed analyzes of results are also discussed in detail.

  6. Looking for chemical reaction networks exhibiting a drift along a manifold of marginally stable states.

    Science.gov (United States)

    Brogioli, Doriano

    2013-02-07

    I recently reported some examples of mass-action equations that have a continuous manifold of marginally stable stationary states [Brogioli, D., 2010. Marginally stable chemical systems as precursors of life. Phys. Rev. Lett. 105, 058102; Brogioli, D., 2011. Marginal stability in chemical systems and its relevance in the origin of life. Phys. Rev. E 84, 031931]. The corresponding chemical reaction networks show nonclassical effects, i.e. a violation of the mass-action equations, under the effect of the concentration fluctuations: the chemical system drifts along the marginally stable states. I proposed that this effect is potentially involved in abiogenesis. In the present paper, I analyze the mathematical properties of mass-action equations of marginally stable chemical reaction networks. The marginal stability implies that the mass-action equations obey some conservation law; I show that the mathematical properties of the conserved quantity characterize the motion along the marginally stable stationary state manifold, i.e. they allow to predict if the fluctuations give rise to a random walk or a drift under the effect of concentration fluctuations. Moreover, I show that the presence of the drift along the manifold of marginally stable stationary-states is a critical property, i.e. at least one of the reaction constants must be fine tuned in order to obtain the drift. Copyright © 2012 Elsevier Ltd. All rights reserved.

  7. Multi-Stable Conductance States in Metallic Double-Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Ci Lijie

    2009-01-01

    Full Text Available Abstract Electrical transport properties of individual metallic double-walled carbon nanotubes (DWCNTs were measured down to liquid helium temperature, and multi-stable conductance states were found in DWCNTs. At a certain temperature, DWCNTs can switch continuously between two or more electronic states, but below certain temperature, DWCNTs are stable only at one of them. The temperature for switching is always different from tube to tube, and even different from thermal cycle to cycle for the same tube. In addition to thermal activation, gate voltage scanning can also realize such switching among different electronic states. The multi-stable conductance states in metallic DWCNTs can be attributed to different Fermi level or occasional scattering centers induced by different configurations between their inner and outer tubes.

  8. On the locally stable states of the Sherrington-Kirkpatrick model

    International Nuclear Information System (INIS)

    Parga, N.; Parisi, G.

    1985-07-01

    By using a steepest descent algorithm we calculate the attraction basin of locally stable states of the Sherrington-Kirkpatrick model of spin glasses. Looking for correlations among these states we show the existence of clusters of spins and construct a cluster Hamiltonian. (author)

  9. Bio-geomorphic feedback causes alternative stable landscape states: insights from coastal marshes and tidal flats

    Science.gov (United States)

    Temmerman, Stijn; Wang, Chen

    2014-05-01

    Many bio-geomorphic systems, such as hill slopes, river floodplains, tidal floodplains and dune areas, seem to be vulnerable to shifts between alternative bare and vegetated landscape states, and these shifts seem to be driven by bio-geomorphic feedbacks. Here we search for empirical evidence for alternative stable state behavior in intertidal flats and marshes, where bio-geomorphic interactions are known to be intense. Large-scale transitions have been reported worldwide between high-elevation vegetated marshes and low-elevation bare flats in intertidal zones of deltas, estuaries, and coastal embayments. It is of significant importance to understand and predict such transitions, because vegetated marshes provide significant services to coastal societies. Previous modeling studies suggest that the ecological theory of catastrophic shifts between alternative stable ecosystem states potentially explains the transition between bare flats and vegetated marshes. However, up to now only few empirical evidence exists. In our study, the hypothesis is empirically tested that vegetated marshes and bare tidal flats can be considered as alternative stable landscape states with rapid shifts between them. We studied historical records (1930s - 2000s) of intertidal elevation surveys and aerial pictures from the Westerschelde estuary (SW Netherlands). Our results demonstrated the existence of: (1) bimodality in the intertidal elevation distribution, i.e., the presence of two peaks in the elevation frequency distribution corresponding to a completely bare state and a densely vegetated state; (2) the relatively rapid transition in elevation when intertidal flats evolve from bare to vegetated states, with sedimentation rates that are 2 to 8 times faster than during the stable states; (3) a threshold elevation above which the shift from bare to vegetated state has a high chance to occur. Our observations demonstrate the abrupt non-linear shift between low-elevation bare flats and high

  10. Increasing atmospheric CO2 overrides the historical legacy of multiple stable biome states in Africa.

    Science.gov (United States)

    Moncrieff, Glenn R; Scheiter, Simon; Bond, William J; Higgins, Steven I

    2014-02-01

    The dominant vegetation over much of the global land surface is not predetermined by contemporary climate, but also influenced by past environmental conditions. This confounds attempts to predict current and future biome distributions, because even a perfect model would project multiple possible biomes without knowledge of the historical vegetation state. Here we compare the distribution of tree- and grass-dominated biomes across Africa simulated using a dynamic global vegetation model (DGVM). We explicitly evaluate where and under what conditions multiple stable biome states are possible for current and projected future climates. Our simulation results show that multiple stable biomes states are possible for vast areas of tropical and subtropical Africa under current conditions. Widespread loss of the potential for multiple stable biomes states is projected in the 21st Century, driven by increasing atmospheric CO2 . Many sites where currently both tree-dominated and grass-dominated biomes are possible become deterministically tree-dominated. Regions with multiple stable biome states are widespread and require consideration when attempting to predict future vegetation changes. Testing for behaviour characteristic of systems with multiple stable equilibria, such as hysteresis and dependence on historical conditions, and the resulting uncertainty in simulated vegetation, will lead to improved projections of global change impacts. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  11. Ground state of charged Base and Fermi fluids in strong coupling

    International Nuclear Information System (INIS)

    Mazighi, R.

    1982-03-01

    The ground state and excited states of the charged Bose gas were studied (wave function, equation of state, thermodynamics, application of Feynman theory). The ground state of the charged Fermi gas was also investigated together with the miscibility of charged Bose and Fermi gases at 0 deg K (bosons-bosons, fermions-bosons and fermions-fermions) [fr

  12. Prediction of new ground-state crystal structure of T a2O5

    Science.gov (United States)

    Yang, Yong; Kawazoe, Yoshiyuki

    2018-03-01

    Tantalum pentoxide (T a2O5 ) is a wide-gap semiconductor which has important technological applications. Despite the enormous efforts from both experimental and theoretical studies, the ground-state crystal structure of T a2O5 is not yet uniquely determined. Based on first-principles calculations in combination with evolutionary algorithm, we identify a triclinic phase of T a2O5 , which is energetically much more stable than any phases or structural models reported previously. Characterization of the static and dynamical properties of the phase reveals the common features shared with previous metastable phases of T a2O5 . In particular, we show that the d spacing of ˜3.8 Å found in the x-ray diffraction patterns of many previous experimental works is actually the radius of the second Ta-Ta coordination shell as defined by radial distribution functions.

  13. Towards 6Li-40K ground state molecules

    International Nuclear Information System (INIS)

    Brachmann, Johannes Felix Simon

    2013-01-01

    The production of a quantum gas with strong long - range dipolar interactions is a major scientific goal in the research field of ultracold gases. In their ro - vibrational ground state Li-K dimers possess a large permanent dipole moment, which could possibly be exploited for the realization of such a quantum gas. A production of these molecules can be achieved by the association of Li and K at a Feshbach resonance, followed by a coherent state transfer. In this thesis, detailed theoretical an experimental preparations to achieve state transfer by means of Stimulated Raman Adiabatic Passage (STIRAP) are described. The theoretical preparations focus on the selection of an electronically excited molecular state that is suitable for STIRAP transfer. In this context, molecular transition dipole moments for both transitions involved in STIRAP transfer are predicted for the first time. This is achieved by the calculation of Franck-Condon factors and a determination of the state in which the 6 Li- 40 K Feshbach molecules are produced. The calculations show that state transfer by use of a single STIRAP sequence is experimentally very well feasible. Further, the optical wavelengths that are needed to address the selected states are calculated. The high accuracy of the data will allow to carry out the molecular spectroscopy in a fast and efficient manner. Further, only a comparatively narrow wavelength tuneability of the spectroscopy lasers is needed. The most suitable Feshbach resonance for the production of 6 Li- 40 K molecules at experimentally manageable magnetic field strengths is occurring at 155 G. Experimentally, this resonance is investigated by means of cross-dimensional relaxation. The application of the technique at various magnetic field strengths in the vicinity of the 155 G Feshbach resonance allows a determination of the resonance position and width with so far unreached precision. This reveals the production of molecules on the atomic side of the resonance

  14. Excited-state dynamics of pentacene derivatives with stable radical substituents.

    Science.gov (United States)

    Ito, Akitaka; Shimizu, Akihiro; Kishida, Noriaki; Kawanaka, Yusuke; Kosumi, Daisuke; Hashimoto, Hideki; Teki, Yoshio

    2014-06-23

    The excited-state dynamics of pentacene derivatives with stable radical substituents were evaluated in detail through transient absorption measurements. The derivatives showed ultrafast formation of triplet excited state(s) in the pentacene moiety from a photoexcited singlet state through the contributions of enhanced intersystem crossing and singlet fission. Detailed kinetic analyses for the transient absorption data were conducted to quantify the excited-state characteristics of the derivatives. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Electromagnetic properties of the three-nucleon ground state

    International Nuclear Information System (INIS)

    Strueve, W.

    1985-01-01

    The electromagnetic form factors of the three-nucleon ground state are calculated on the base of an exact solution of the Faddeev equations. In a Hilbert space of nucleons and a possible Δ-isobar the effects of a non-perturbative description of the Δ-isobar on the magnetic form factors are studied. Pure nucleonic current operators with two- and three-particle character can be described in the extended Hilbert space by simpler one-body operators. Additionally nonrelativistic meson-exchange corrections due to π and ρ exchange are calculated consistently with the requirements of current conservation. Further relativistic corrections are estimated on selected examples. The calculations yield a total magnetic contribution of the Δ-isobar which is smaller than hitherto assumed, a static approximation of the Δ propagation is proved as inadmissible and must be rejected. Together with the meson-exchange corrections a well agreement with the experimental data at low momentum transfers results. Especially the magnetic moments and magnetization radii can be explained. For higher momentum transfers the results show the importance of further corrections. The regard of selected relativistic corrections leads to a good description of the experimental magnetic form factors. Also by this way the position of the minimum and the height of the second maximum in the 3 He charge form factor can be explained. The comparison with the latest experimental results reveals furthermore unresolved problems in the description of the 3 H charge form factor. (orig.) [de

  16. Ground-state splitting of ultrashallow thermal donors with negative central-cell corrections in silicon

    Science.gov (United States)

    Hara, Akito; Awano, Teruyoshi

    2017-06-01

    Ultrashallow thermal donors (USTDs), which consist of light element impurities such as carbon, hydrogen, and oxygen, have been found in Czochralski silicon (CZ Si) crystals. To the best of our knowledge, these are the shallowest hydrogen-like donors with negative central-cell corrections in Si. We observed the ground-state splitting of USTDs by far-infrared optical absorption at different temperatures. The upper ground-state levels are approximately 4 meV higher than the ground-state levels. This energy level splitting is also consistent with that obtained by thermal excitation from the ground state to the upper ground state. This is direct evidence that the wave function of the USTD ground state is made up of a linear combination of conduction band minimums.

  17. Anomalous Ground State of the Electrons in Nano-confined Water

    Science.gov (United States)

    2016-06-13

    Anomalous ground state of the electrons in nano -confined water G. F. Reiter1*, Aniruddha Deb2*, Y. Sakurai3, M. Itou3, V. G. Krishnan4, S. J...electronic ground state of nano -confined water must be responsible for these anomalies but has so far not been investigated. We show here for the first time...using x-ray Compton scattering and a computational model, that the ground state configuration of the valence electrons in a particular nano

  18. Limiting stable states of high-Tc superconductors in the alternating current modes

    International Nuclear Information System (INIS)

    Romanovskii, V.R.; Watanabe, K.; Awaji, S.

    2014-01-01

    The limiting current-carrying capacity of high-T c superconductor and superconducting tape has been studied in the alternating current states. The features that are responsible for their stable formation have been investigated under the conduction-cooled conditions when the operating peak values of the electric field and the current may essentially exceed the corresponding critical values of superconductor. Besides, it has been proved that these peak values are higher than the values of the electric field and the current, which lead to the thermal runaway phenomenon when the current instability onset occurs in the operating modes with direct current. As a result, the stable extremely high heat generation exists in these operating states, which can be called as overloaded states. The limiting stable peak values of charged currents and stability conditions have been determined taking into account the flux creep states of superconductors. The analysis performed has revealed that there exist characteristic times defining the corresponding time windows in the stable development of overloaded states of the alternating current. In order to explain their existence, the basic thermo-electrodynamics mechanisms have been formulated, which have allowed to explain the high stable values of the temperature and the induced electric field before the onset of alternating current instability. In general, it has been shown that the high-T c superconductors may stably operate in the overloaded alternating current states even under the not intensive cooling conditions at a very high level of heat generation, which is not considered in the existing theory of losses. (authors)

  19. Derivation of novel human ground state naive pluripotent stem cells.

    Science.gov (United States)

    Gafni, Ohad; Weinberger, Leehee; Mansour, Abed AlFatah; Manor, Yair S; Chomsky, Elad; Ben-Yosef, Dalit; Kalma, Yael; Viukov, Sergey; Maza, Itay; Zviran, Asaf; Rais, Yoach; Shipony, Zohar; Mukamel, Zohar; Krupalnik, Vladislav; Zerbib, Mirie; Geula, Shay; Caspi, Inbal; Schneir, Dan; Shwartz, Tamar; Gilad, Shlomit; Amann-Zalcenstein, Daniela; Benjamin, Sima; Amit, Ido; Tanay, Amos; Massarwa, Rada; Novershtern, Noa; Hanna, Jacob H

    2013-12-12

    Mouse embryonic stem (ES) cells are isolated from the inner cell mass of blastocysts, and can be preserved in vitro in a naive inner-cell-mass-like configuration by providing exogenous stimulation with leukaemia inhibitory factor (LIF) and small molecule inhibition of ERK1/ERK2 and GSK3β signalling (termed 2i/LIF conditions). Hallmarks of naive pluripotency include driving Oct4 (also known as Pou5f1) transcription by its distal enhancer, retaining a pre-inactivation X chromosome state, and global reduction in DNA methylation and in H3K27me3 repressive chromatin mark deposition on developmental regulatory gene promoters. Upon withdrawal of 2i/LIF, naive mouse ES cells can drift towards a primed pluripotent state resembling that of the post-implantation epiblast. Although human ES cells share several molecular features with naive mouse ES cells, they also share a variety of epigenetic properties with primed murine epiblast stem cells (EpiSCs). These include predominant use of the proximal enhancer element to maintain OCT4 expression, pronounced tendency for X chromosome inactivation in most female human ES cells, increase in DNA methylation and prominent deposition of H3K27me3 and bivalent domain acquisition on lineage regulatory genes. The feasibility of establishing human ground state naive pluripotency in vitro with equivalent molecular and functional features to those characterized in mouse ES cells remains to be defined. Here we establish defined conditions that facilitate the derivation of genetically unmodified human naive pluripotent stem cells from already established primed human ES cells, from somatic cells through induced pluripotent stem (iPS) cell reprogramming or directly from blastocysts. The novel naive pluripotent cells validated herein retain molecular characteristics and functional properties that are highly similar to mouse naive ES cells, and distinct from conventional primed human pluripotent cells. This includes competence in the generation

  20. Ground state solutions for asymptotically periodic Schrodinger equations with critical growth

    Directory of Open Access Journals (Sweden)

    Hui Zhang

    2013-10-01

    Full Text Available Using the Nehari manifold and the concentration compactness principle, we study the existence of ground state solutions for asymptotically periodic Schrodinger equations with critical growth.

  1. Correlated ground state and E2 giant resonance built on it

    International Nuclear Information System (INIS)

    Tohyama, Mitsuru

    1995-01-01

    Taking 16 O as an example of realistic nuclei, we demonstrate that a correlated ground state can be obtained as a long time solution of a time-dependent density-matrix formalism (TDDM) when the residual interaction is adiabatically treated. We also study in TDDM the E2 giant resonance of 16 O built on the correlated ground state and compare it with that built on the Hartree-Fock ground state. It is found that a spurious mixing of low frequency components seen in the latter is eliminated by using the correlated ground state. (author)

  2. Optimized RVB states of the 2-d antiferromagnet: ground state and excitation spectrum

    Science.gov (United States)

    Chen, Yong-Cong; Xiu, Kai

    1993-10-01

    The Gutzwiller projection of the Schwinger-boson mean-field solution of the 2-d spin- {1}/{2} antiferromagnet in a square lattice is shown to produce the optimized, parameter-free RVB ground state. We get -0.6688 J/site and 0.311 for the energy and the staggered magnetization. The spectrum of the excited states is found to be linear and gapless near k≅0. Our calculation suggests, upon breaking of the rotational symmetry, ɛ k≅2JZ r1-γ 2k with Zr≅1.23.

  3. Mathematical aspects of ground state tunneling models in luminescence materials

    International Nuclear Information System (INIS)

    Pagonis, Vasilis; Kitis, George

    2015-01-01

    Luminescence signals from a variety of natural materials have been known to decrease with storage time at room temperature due to quantum tunneling, a phenomenon known as anomalous fading. This paper is a study of several mathematical aspects of two previously published luminescence models which describe tunneling phenomena from the ground state of a donor–acceptor system. It is shown that both models are described by the same type of integral equation, and two new analytical equations are presented. The first new analytical equation describes the effect of anomalous fading on the dose response curves (DRCs) of naturally irradiated samples. The DRCs in the model were previously expressed in the form of integral equations requiring numerical integration, while the new analytical equation can be used immediately as a tool for analyzing experimental data. The second analytical equation presented in this paper describes the anomalous fading rate (g-Value per decade) as a function of the charge density in the model. This new analytical expression for the g-Value is tested using experimental anomalous fading data for several apatite crystals which exhibit high rate of anomalous fading. The two new analytical results can be useful tools for analyzing anomalous fading data from luminescence materials. In addition to the two new analytical equations, an explanation is provided for the numerical value of a constant previously introduced in the models. - Highlights: • Comparative study of two luminescence models for feldspars. • Two new analytical equations for dose response curves and anomalous fading rate. • The numerical value z=1.8 of previously introduced constant in models explained.

  4. Tricriticality for dimeric Coulomb molecular crystals in ground state

    Science.gov (United States)

    Travěnec, Igor; Šamaj, Ladislav

    2017-12-01

    We study the ground-state properties of a system of dimers. Each dimer consists in a pair of equivalent charges at a fixed distance, immersed in a neutralizing homogeneous background. All charges interact pairwisely by Coulomb potential. The dimer centers form a two-dimensional rectangular lattice with the aspect ratio α\\in [0, 1] and each dimer is allowed to rotate around its center. The previous numerical simulations, made for the more general Yukawa interaction, indicate that only two basic dimer configurations can appear: either all dimers are parallel or they have two different angle orientations within alternating (checkerboard) sublattices. As the dimer size increases, two second-order phase transitions, related to two kinds of the symmetry breaking in dimer’s orientations, were reported. In this paper, we use a recent analytic method based on an expansion of the interaction energy in Misra functions which converges quickly and provides an analytic derivation of the critical behaviour. Our main result is that there exists a specific aspect ratio of the rectangular lattice α^*=0.714 106 840 000 71\\ldots which divides the space of model’s phases onto two distinct regions. If the lattice aspect ratio α>α* , we recover both types of the second-order phase transitions and find that they are of mean-field type with the critical exponent β = 1/2 . If 0.711 535≤slantα<α* , the phase transition associated with the discontinuity of dimer’s angles on alternating sublattices becomes of first order. For α=α* , the first- and second-order phase transitions meet at the tricritical point, characterized by the different critical index β = 1/4 . Such phenomenon is known from literature about the Landau theory of one-component fields, but in our two-component version the scenario is more complicated: the component which is already in the symmetry-broken state at the tricritical point also interferes and exhibits unexpectedly the mean-field singular

  5. Photophysics of trioxatriangulenium ion. Electrophilic reactivity in the ground state and excited singlet state

    DEFF Research Database (Denmark)

    Reynisson, J.; Wilbrandt, R.; Brinck, V.

    2002-01-01

    . The physical and chemical properties of the excited singlet state of the trioxatriangulenium (TOTA(+)) carbenium ion are investigated by experimental and Computational means. The degeneracy of the lowest excited states is counteracted by Jahn-Teller-type distortion, which leads to vibronic broadening...... of the long wavelength absorption band. A strong fluorescence is observed at 520 nm (tau(n) = 14.6 ns, phi(n) = 0.12 in deaerated acetonitrile). The fluorescence is quenched by 10 aromatic electron donors predominantly via a dynamic charge transfer mechanism, but ground state complexation is shown...... triphenylenes is studied separately. Phosphorescence spectra, triplet lifetimes, and triplet-triplet absorption spectra are provided. In the discussion, TOTA(+) is compared to the unsubstituted xanthenium ion and its 9-phenyl derivative with respect to the excited state properties....

  6. Experimental evidence and modelling of drought induced alternative stable soil moisture states

    Science.gov (United States)

    Robinson, David; Jones, Scott; Lebron, Inma; Reinsch, Sabine; Dominguez, Maria; Smith, Andrew; Marshal, Miles; Emmett, Bridget

    2017-04-01

    The theory of alternative stable states in ecosystems is well established in ecology; however, evidence from manipulation experiments supporting the theory is limited. Developing the evidence base is important because it has profound implications for ecosystem management. Here we show evidence of the existence of alternative stable soil moisture states induced by drought in an upland wet heath. We used a long-term (15 yrs) climate change manipulation experiment with moderate sustained drought, which reduced the ability of the soil to retain soil moisture by degrading the soil structure, reducing moisture retention. Moreover, natural intense droughts superimposed themselves on the experiment, causing an unexpected additional alternative soil moisture state to develop, both for the drought manipulation and control plots; this impaired the soil from rewetting in winter. Our results show the coexistence of three stable states. Using modelling with the Hydrus 1D software package we are able to show the circumstances under which shifts in soil moisture states are likely to occur. Given the new understanding it presents a challenge of how to incorporate feedbacks, particularly related to soil structure, into soil flow and transport models?

  7. Gaussian Plume Model Parameters for Ground-Level and Elevated Sources Derived from the Atmospheric Diffusion Equation in the Neutral and Stable Conditions

    International Nuclear Information System (INIS)

    Essa, K.S.M.

    2009-01-01

    The analytical solution of the atmospheric diffusion equation for a point source gives the ground-level concentration profiles. It depends on the wind speed ua nd vertical dispersion coefficient σ z expressed by Pasquill power laws. Both σ z and u are functions of downwind distance, stability and source elevation, while for the ground-level emission u is constant. In the neutral and stable conditions, the Gaussian plume model and finite difference numerical methods with wind speed in power law and the vertical dispersion coefficient in exponential law are estimated. This work shows that the estimated ground-level concentrations of the Gaussian model for high-level source and numerical finite difference method are very match fit to the observed ground-level concentrations of the Gaussian model

  8. Derivation of the RPA (Random Phase Approximation) Equation of ATDDFT (Adiabatic Time Dependent Density Functional Ground State Response Theory) from an Excited State Variational Approach Based on the Ground State Functional.

    Science.gov (United States)

    Ziegler, Tom; Krykunov, Mykhaylo; Autschbach, Jochen

    2014-09-09

    The random phase approximation (RPA) equation of adiabatic time dependent density functional ground state response theory (ATDDFT) has been used extensively in studies of excited states. It extracts information about excited states from frequency dependent ground state response properties and avoids, thus, in an elegant way, direct Kohn-Sham calculations on excited states in accordance with the status of DFT as a ground state theory. Thus, excitation energies can be found as resonance poles of frequency dependent ground state polarizability from the eigenvalues of the RPA equation. ATDDFT is approximate in that it makes use of a frequency independent energy kernel derived from the ground state functional. It is shown in this study that one can derive the RPA equation of ATDDFT from a purely variational approach in which stationary states above the ground state are located using our constricted variational DFT (CV-DFT) method and the ground state functional. Thus, locating stationary states above the ground state due to one-electron excitations with a ground state functional is completely equivalent to solving the RPA equation of TDDFT employing the same functional. The present study is an extension of a previous work in which we demonstrated the equivalence between ATDDFT and CV-DFT within the Tamm-Dancoff approximation.

  9. Exact ground and excited states of an antiferromagnetic quantum spin model

    International Nuclear Information System (INIS)

    Bose, I.

    1989-08-01

    A quasi-one-dimensional spin model which consists of a chain of octahedra of spins has been suggested for which a certain parameter regime of the Hamiltonian, the ground state, can be written down exactly. The ground state is highly degenerate and can be other than a singlet. Also, several excited states can be constructed exactly. The ground state is a local RVB state for which resonance is confined to rings of spins. Some exact numerical results for an octahedron of spins have also been reported. (author). 16 refs, 2 figs, 1 tab

  10. Construction and study of exact ground states for a class of quantum antiferromagnets

    International Nuclear Information System (INIS)

    Fannes, M.

    1989-01-01

    Techniques of quantum probability are used to construct the exact ground states for a class of quantum spin systems in one dimension. This class in particular contains the antiferromagnetic models introduced by various authors under the name of VBS-models. The construction permits a detailed study of these ground states. (A.C.A.S.) [pt

  11. Long range order in the ground state of two-dimensional antiferromagnets

    International Nuclear Information System (INIS)

    Neves, E.J.; Perez, J.F.

    1985-01-01

    The existence of long range order is shown in the ground state of the two-dimensional isotropic Heisenberg antiferromagnet for S >= 3/2. The method yields also long range order for the ground state of a larger class of anisotropic quantum antiferromagnetic spin systems with or without transverse magnetic fields. (Author) [pt

  12. Ab initio calculation atomics ground state wave function for interactions Ion- Atom

    International Nuclear Information System (INIS)

    Shojaee, F.; Bolori zadeh, M. A.

    2007-01-01

    Ab initio calculation atomics ground state wave function for interactions Ion- Atom Atomic wave function expressed in a Slater - type basis obtained within Roothaan- Hartree - Fock for the ground state of the atoms He through B. The total energy is given for each atom.

  13. Ground State Structure of a Coupled 2-Fermion System in Supersymmetric Quantum Mechanics

    Science.gov (United States)

    Finster, Felix

    1997-05-01

    We prove the uniqueness of the ground state for a supersymmetric quantum mechanical system of two fermions and two bosons, which is closely related to theN=1 WZ-model. The proof is constructive and gives detailed information on what the ground state looks like

  14. Ground state structure of a coupled 2-fermion system in supersymmetric quantum mechanics

    International Nuclear Information System (INIS)

    Finster, F.

    1997-01-01

    We prove the uniqueness of the ground state for a supersymmetric quantum mechanical system of two fermions and two bosons, which is closely related to the N=1 WZ-model. The proof is constructive and gives detailed information on what the ground state looks like. copyright 1997 Academic Press, Inc

  15. Continuous control of asymmetric forebody vortices in a bi-stable state

    Science.gov (United States)

    Wang, Qi-te; Cheng, Ke-ming; Gu, Yun-song; Li, Zhuo-qi

    2018-02-01

    Aiming at the problem of continuous control of asymmetric forebody vortices at a high angle of attack in a bi-stable regime, a dual synthetic jet actuator embedded in an ogive forebody was designed. Alternating unsteady disturbance with varying degree asymmetrical flow fields near the nozzles is generated by adjusting the duty cycle of the drive signal of the actuator, specifically embodying the asymmetric time-averaged pattern of jet velocity, vorticity, and turbulent kinetic energy. Experimental results show that within the range of relatively high angles of attack, including the angle-of-attack region in a bi-stable state, the lateral force of the ogive forebody is continuously controlled by adjusting the duty cycle of the drive signal; the position of the forebody vortices in space, the vorticity magnitude, the total pressure coefficient near the vortex core, and the vortex breakdown location are continuously changed with the duty cycle increased observed from the time-averaged flow field. Instantaneous flow field results indicate that although the forebody vortices are in an unsteady oscillation state, a continuous change in the forebody vortices' oscillation balance position as the duty cycle increases leads to a continuous change in the model's surface pressure distribution and time-averaged lateral force. Different from the traditional control principle, in this study, other different degree asymmetrical states of the forebody vortices except the bi-stable state are obtained using the dual synthetic jet control technology.

  16. Analysis of stable states in global savannas: is the CART pulling the horse?

    Science.gov (United States)

    Hanan, Niall P; Tredennick, Andrew T; Prihodko, Lara; Bucini, Gabriela; Dohn, Justin

    2014-03-01

    Multiple stable states, bifurcations and thresholds are fashionable concepts in the ecological literature, a recognition that complex ecosystems may at times exhibit the interesting dynamic behaviours predicted by relatively simple biomathematical models. Recently, several papers in Global Ecology and Biogeography , Proceedings of the National Academy of Sciences USA, Science and elsewhere have attempted to quantify the prevalence of alternate stable states in the savannas of Africa, Australia and South America, and the tundra-taiga-grassland transitions of the circum-boreal region using satellite-derived woody canopy cover. While we agree with the logic that basins of attraction can be inferred from the relative frequencies of ecosystem states observed in space and time, we caution that the statistical methodologies underlying the satellite product used in these studies may confound our ability to infer the presence of multiple stable states. We demonstrate this point using a uniformly distributed 'pseudo-tree cover' database for Africa that we use to retrace the steps involved in creation of the satellite tree-cover product and subsequent analysis. We show how classification and regression tree (CART)-based products may impose discontinuities in satellite tree-cover estimates even when such discontinuities are not present in reality. As regional and global remote sensing and geospatial data become more easily accessible for ecological studies, we recommend careful consideration of how error distributions in remote sensing products may interact with the data needs and theoretical expectations of the ecological process under study.

  17. Description of a stable scheme for steady-state coupled Monte Carlo–thermal–hydraulic calculations

    International Nuclear Information System (INIS)

    Dufek, Jan; Eduard Hoogenboom, J.

    2014-01-01

    Highlights: • A stable coupling scheme for steady-state MC–TH calculations is described. • The coupling scheme is based on the stochastic approximation method. • The neutron flux (or power) distribution is relaxed using a variable step-size. - Abstract: We provide a detailed description of a numerically stable and efficient coupling scheme for steady-state Monte Carlo neutronic calculations with thermal–hydraulic feedback. While we have previously derived and published the stochastic approximation based method for coupling the Monte Carlo criticality and thermal–hydraulic calculations, its possible implementation has not been described in a step-by-step manner. As the simple description of the coupling scheme was repeatedly requested from us, we have decided to make it available via this note

  18. On Nash Equilibrium and Evolutionarily Stable States That Are Not Characterised by the Folk Theorem.

    Directory of Open Access Journals (Sweden)

    Jiawei Li

    Full Text Available In evolutionary game theory, evolutionarily stable states are characterised by the folk theorem because exact solutions to the replicator equation are difficult to obtain. It is generally assumed that the folk theorem, which is the fundamental theory for non-cooperative games, defines all Nash equilibria in infinitely repeated games. Here, we prove that Nash equilibria that are not characterised by the folk theorem do exist. By adopting specific reactive strategies, a group of players can be better off by coordinating their actions in repeated games. We call it a type-k equilibrium when a group of k players coordinate their actions and they have no incentive to deviate from their strategies simultaneously. The existence and stability of the type-k equilibrium in general games is discussed. This study shows that the sets of Nash equilibria and evolutionarily stable states have greater cardinality than classic game theory has predicted in many repeated games.

  19. On Nash Equilibrium and Evolutionarily Stable States That Are Not Characterised by the Folk Theorem

    Science.gov (United States)

    Li, Jiawei; Kendall, Graham

    2015-01-01

    In evolutionary game theory, evolutionarily stable states are characterised by the folk theorem because exact solutions to the replicator equation are difficult to obtain. It is generally assumed that the folk theorem, which is the fundamental theory for non-cooperative games, defines all Nash equilibria in infinitely repeated games. Here, we prove that Nash equilibria that are not characterised by the folk theorem do exist. By adopting specific reactive strategies, a group of players can be better off by coordinating their actions in repeated games. We call it a type-k equilibrium when a group of k players coordinate their actions and they have no incentive to deviate from their strategies simultaneously. The existence and stability of the type-k equilibrium in general games is discussed. This study shows that the sets of Nash equilibria and evolutionarily stable states have greater cardinality than classic game theory has predicted in many repeated games. PMID:26288088

  20. Alternative Stable States, Coral Reefs, and Smooth Dynamics with a Kick.

    Science.gov (United States)

    Ippolito, Stephen; Naudot, Vincent; Noonburg, Erik G

    2016-03-01

    We consider a computer simulation, which was found to be faithful to time series data for Caribbean coral reefs, and an analytical model to help understand the dynamics of the simulation. The analytical model is a system of ordinary differential equations (ODE), and the authors claim this model demonstrates the existence of alternative stable states. The existence of an alternative stable state should consider a sudden shift in coral and macroalgae populations, while the grazing rate remains constant. The results of such shifts, however, are often confounded by changes in grazing rate. Although the ODE suggest alternative stable states, the ODE need modification to explicitly account for shifts or discrete events such as hurricanes. The goal of this paper will be to study the simulation dynamics through a simplified analytical representation. We proceed by modifying the original analytical model through incorporating discrete changes into the ODE. We then analyze the resulting dynamics and their bifurcations with respect to changes in grazing rate and hurricane frequency. In particular, a "kick" enabling the ODE to consider impulse events is added. Beyond adding a "kick" we employ the grazing function that is suggested by the simulation. The extended model was fit to the simulation data to support its use and predicts the existence cycles depending nonlinearly on grazing rates and hurricane frequency. These cycles may bring new insights into consideration for reef health, restoration and dynamics.

  1. Thermodynamics and dynamics of the hard-sphere system: From stable to metastable states

    Energy Technology Data Exchange (ETDEWEB)

    Bomont, Jean-Marc, E-mail: jean-marc.bomont@univ-lorraine.fr; Bretonnet, Jean-Louis

    2014-08-17

    Highlights: • Three different scaling laws, devoted to transport properties of hard-sphere system, are investigated over a wide range of packing fractions. • A new semiempirical relation linking the transport properties to the excess pressure is derived. • The present relation allows to better understand the link between the thermodynamic and the dynamic properties of the hard-sphere system. - Abstract: A set of three different scaling laws is investigated, which are devoted to link the transport properties, i.e. diffusion coefficient, shear viscosity, bulk viscosity and thermal conductivity, to the thermodynamic properties for the athermal hard-sphere system, over the wider range of packing fraction covering the stable and metastable regimes. Except for the thermal conductivity, the Rosenfeld (1999) [15] relation is found to be applicable to the stable states while the Adam and Gibbs (1965) [24] relation holds well for the metastable states. In contrast, the modified Cohen and Turnbull (1959) [25] relation proposed here gives sound support for a universal scaling law connecting the dynamic and thermodynamic properties, over the domain of packing fraction including the stable and metastable states. In particular, it is found that the most relevant control parameter is not the excess entropy, but the logarithm derivative of the excess entropy with respect to the packing fraction. In the same context, the Stokes–Einstein relation between the diffusion coefficient and the shear viscosity is also examined. The possible violation of the Stokes–Einstein relation is investigated over a large domain of packing fractions.

  2. Thermodynamics and dynamics of the hard-sphere system: From stable to metastable states

    International Nuclear Information System (INIS)

    Bomont, Jean-Marc; Bretonnet, Jean-Louis

    2014-01-01

    Highlights: • Three different scaling laws, devoted to transport properties of hard-sphere system, are investigated over a wide range of packing fractions. • A new semiempirical relation linking the transport properties to the excess pressure is derived. • The present relation allows to better understand the link between the thermodynamic and the dynamic properties of the hard-sphere system. - Abstract: A set of three different scaling laws is investigated, which are devoted to link the transport properties, i.e. diffusion coefficient, shear viscosity, bulk viscosity and thermal conductivity, to the thermodynamic properties for the athermal hard-sphere system, over the wider range of packing fraction covering the stable and metastable regimes. Except for the thermal conductivity, the Rosenfeld (1999) [15] relation is found to be applicable to the stable states while the Adam and Gibbs (1965) [24] relation holds well for the metastable states. In contrast, the modified Cohen and Turnbull (1959) [25] relation proposed here gives sound support for a universal scaling law connecting the dynamic and thermodynamic properties, over the domain of packing fraction including the stable and metastable states. In particular, it is found that the most relevant control parameter is not the excess entropy, but the logarithm derivative of the excess entropy with respect to the packing fraction. In the same context, the Stokes–Einstein relation between the diffusion coefficient and the shear viscosity is also examined. The possible violation of the Stokes–Einstein relation is investigated over a large domain of packing fractions

  3. The significant role of covalency in determining the ground state of cobalt phthalocyanines molecule

    Directory of Open Access Journals (Sweden)

    Jing Zhou

    2016-03-01

    Full Text Available To shed some light on the metal 3d ground state configuration of cobalt phthalocyanines system, so far in debate, we present an investigation by X-ray absorption spectroscopy (XAS at Co L2,3 edge and theoretical calculation. The density functional theory calculations reveal highly anisotropic covalent bond between central cobalt ion and nitrogen ligands, with the dominant σ donor accompanied by weak π-back acceptor interaction. Our combined experimental and theoretical study on the Co-L2,3 XAS spectra demonstrate a robust ground state of 2A1g symmetry that is built from 73% 3d7 character and 27% 3 d 8 L ¯ ( L ¯ denotes a ligand hole components, as the first excited-state with 2Eg symmetry lies about 158 meV higher in energy. The effect of anisotropic and isotropic covalency on the ground state was also calculated and the results indicate that the ground state with 2A1g symmetry is robust in a large range of anisotropic covalent strength while a transition of ground state from 2A1g to 2Eg configuration when isotropic covalent strength increases to a certain extent. Here, we address a significant anisotropic covalent effect of short Co(II-N bond on the ground state and suggest that it should be taken into account in determining the ground state of analogous cobalt complexes.

  4. Arsenic in Ground Water of the United States

    Science.gov (United States)

    ... Team More Information Arsenic in groundwater of the United States Arsenic in groundwater is largely the result of ... Gronberg (2011) for updated arsenic map. Featured publications United States Effects of human-induced alteration of groundwater flow ...

  5. A simple parameter-free wavefunction for the ground state of two-electron atoms

    International Nuclear Information System (INIS)

    Ancarani, L U; Rodriguez, K V; Gasaneo, G

    2007-01-01

    We propose a simple and pedagogical wavefunction for the ground state of two-electron atoms which (i) is parameter free (ii) satisfies all two-particle cusp conditions (iii) yields reasonable ground-state energies, including the prediction of a bound state for H - . The mean energy, and other mean physical quantities, is evaluated analytically. The simplicity of the result can be useful as an easy-to-use wavefunction when testing collision models

  6. Exact many-electron ground states on diamond and triangle Hubbard chains

    International Nuclear Information System (INIS)

    Gulacsi, Zsolt; Kampf, Arno; Vollhardt, Dieter

    2009-01-01

    We construct exact ground states of interacting electrons on triangle and diamond Hubbard chains. The construction requires (1) a rewriting of the Hamiltonian into positive semidefinite form, (2) the construction of a many-electron ground state of this Hamiltonian, and (3) the proof of the uniqueness of the ground state. This approach works in any dimension, requires no integrability of the model, and only demands sufficiently many microscopic parameters in the Hamiltonian which have to fulfill certain relations. The scheme is first employed to construct exact ground state for the diamond Hubbard chain in a magnetic field. These ground states are found to exhibit a wide range of properties such as flat-band ferromagnetism and correlation induced metallic, half-metallic or insulating behavior, which can be tuned by changing the magnetic flux, local potentials, or electron density. Detailed proofs of the uniqueness of the ground states are presented. By the same technique exact ground states are constructed for triangle Hubbard chains and a one-dimensional periodic Anderson model with nearest-neighbor hybridization. They permit direct comparison with results obtained by variational techniques for f-electron ferromagnetism due to a flat band in CeRh 3 B 2 . (author)

  7. Electromagnetically induced transparency and absorption due to optical and ground-state coherences in 6Li

    International Nuclear Information System (INIS)

    Fuchs, J; Duffy, G J; Rowlands, W J; Lezama, A; Hannaford, P; Akulshin, A M

    2007-01-01

    We present an experimental study of sub-natural width resonances in fluorescence from a collimated beam of 6 Li atoms excited on the D 1 and D 2 lines by a bichromatic laser field. We show that in addition to ground-state Zeeman coherence, coherent population oscillations between ground and excited states contribute to the sub-natural resonances. High-contrast resonances of electromagnetically induced transparency and electromagnetically induced absorption due to both effects, i.e., ground-state Zeeman coherence and coherent population oscillations, are observed

  8. A study of a stable Al-Cu-Fe quasicrystal in solid and liquid state

    International Nuclear Information System (INIS)

    Chen Lifan; Chen Xishen

    1992-01-01

    A stable Al 65 Cu 20 Fe 15 quasicrystal with an icosahedral structure is studied in solid and liquid state. It is found that the icosahedral phase in Al 65 Cu 20 Fe 15 alloy does not grow directly from the pure liquid state, but rather forms between monoclinic Al 13 Fe 4 and residual liquid state at 865degC. The melting point of the Al 65 Cu 20 Fe 15 icosahedral quasicrystal occurs at 865degC and that of the Al 65 Cu 20 Fe 15 alloy occurs at 1008degC. Moreover, the monoclinic Al 13 Fe 4 is transformed into the icosahedral phase easily at the temperature of 845degC. The icosahedral quasicrystal in Al 65 Cu 20 Fe 15 alloy has a high thermal stability even at 950degC. Above 950degC, the icosahedral structure tends to an amorphous structure. (orig.)

  9. Exact ground-state correlation functions of one-dimenisonal strongly correlated electron models with resonating-valence-bond ground state

    International Nuclear Information System (INIS)

    Yamanaka, Masanori; Honjo, Shinsuke; Kohmoto, Mahito

    1996-01-01

    We investigate one-dimensional strongly correlated electron models which have the resonating-valence-bond state as the exact ground state. The correlation functions are evaluated exactly using the transfer matrix method for the geometric representations of the valence-bond states. In this method, we only treat matrices with small dimensions. This enables us to give analytical results. It is shown that the correlation functions decay exponentially with distance. The result suggests that there is a finite excitation gap, and that the ground state is insulating. Since the corresponding noninteracting systems may be insulating or metallic, we can say that the gap originates from strong correlation. The persistent currents of the present models are also investigated and found to be exactly vanishing

  10. Nonspherical atomic ground-state densities and chemical deformation densities from x-ray scattering

    International Nuclear Information System (INIS)

    Ruedenberg, K.; Schwarz, W.H.E.

    1990-01-01

    Presuming that chemical insight can be gained from the difference between the molecular electron density and the superposition of the ground-state densities of the atoms in a molecule, it is pointed out that, for atoms with degenerate ground states, an unpromoted ''atom in a molecule'' is represented by a specific ensemble of the degenerate atomic ground-state wave functions and that this ensemble is determined by the anisotropic local surroundings. The resulting atomic density contributions are termed oriented ground state densities, and the corresponding density difference is called the chemical deformation density. The constraints implied by this conceptual approach for the atomic density contributions are formulated and a method is developed for determining them from x-ray scattering data. The electron density of the appropriate promolecule and its x-ray scattering are derived, the determination of the parameters of the promolecule is outlined, and the chemical deformation density is formulated

  11. Theoretical Grounds of Formation of the Efficient State Economic Policy

    Directory of Open Access Journals (Sweden)

    Semyrak Oksana S.

    2013-12-01

    Full Text Available The article conducts historical and analytical analysis of views on the role of state administration in the sphere of economic relations by various economic directions in order to allocate traditional and newest essential reference points of the modern theory of state regulation of economy. It identifies specific features of modern models of economic policy that envisage setting goals by the state, selection of relevant efficient tools and mathematic function, which would describe dependencies between them. It considers the concept of the basic theory of economic policy of Jan Tinbergen, its advantages and shortcomings. It studies prerequisites and conducts analysis of the modern concept of the role of state in economy as a subject of the market. It considers the modern concept of economic socio-dynamics, pursuant to which the main task of the state is maximisation of social usefulness and permanent improvement of the Pareto-optimal. It considers the “socio-dynamic multiplicator” notion, which envisages availability of three main components: social effect from activity of the state, yearning of individuals for creation of something new and availability of formal and informal institutions that united first two elements.

  12. Pade approximants for the ground-state energy of closed-shell quantum dots

    International Nuclear Information System (INIS)

    Gonzalez, A.; Partoens, B.; Peeters, F.M.

    1997-08-01

    Analytic approximations to the ground-state energy of closed-shell quantum dots (number of electrons from 2 to 210) are presented in the form of two-point Pade approximants. These Pade approximants are constructed from the small- and large-density limits of the energy. We estimated that the maximum error, reached for intermediate densities, is less than ≤ 3%. Within that present approximation the ground-state is found to be unpolarized. (author). 21 refs, 3 figs, 2 tabs

  13. Many electron variational ground state of the two dimensional Anderson lattice

    International Nuclear Information System (INIS)

    Zhou, Y.; Bowen, S.P.; Mancini, J.D.

    1991-02-01

    A variational upper bound of the ground state energy of two dimensional finite Anderson lattices is determined as a function of lattice size (up to 16 x 16). Two different sets of many-electron basis vectors are used to determine the ground state for all values of the coulomb integral U. This variational scheme has been successfully tested for one dimensional models and should give good estimates in two dimensions

  14. Ground-state energy for 1D (t,U,X)-model at low densities

    International Nuclear Information System (INIS)

    Buzatu, F.D.

    1992-09-01

    In describing the properties of quasi-1D materials with a highly-screened interelectronic potential, an attractive hopping term has to be added to the Hubbard Hamiltonian. The effective interaction and the ground-state energy in ladder approximation are analyzed. At low electronic densities, the attractive part of the interaction, initially smaller than the repulsive term, can become more effective, the ground-state energy decreasing below the unperturbed value. (author). 12 refs, 4 figs

  15. Examination of Below-Ground Structure and Soil Respiration Rates of Stable and Deteriorating Salt Marshes in Jamaica Bay (NY)

    Science.gov (United States)

    CAT scan imaging is currently being used to examine below-ground peat and root structure in cores collected from salt marshes of Jamaica Bay, part of the Gateway National Recreation Area (NY). CAT scans or Computer-Aided Tomography scans use X-ray equipment to produce multiple i...

  16. Relativistic configuration interaction calculation on the ground and excited states of iridium monoxide

    International Nuclear Information System (INIS)

    Suo, Bingbing; Yu, Yan-Mei; Han, Huixian

    2015-01-01

    We present the fully relativistic multi-reference configuration interaction calculations of the ground and low-lying excited electronic states of IrO for individual spin-orbit component. The lowest-lying state is calculated for Ω = 1/2, 3/2, 5/2, and 7/2 in order to clarify the ground state of IrO. Our calculation suggests that the ground state is of Ω = 1/2, which is highly mixed with 4 Σ − and 2 Π states in Λ − S notation. The two low-lying states 5/2 and 7/2 are nearly degenerate with the ground state and locate only 234 and 260 cm −1 above, respectively. The equilibrium bond length 1.712 Å and the harmonic vibrational frequency 903 cm −1 of the 5/2 state are close to the experimental measurement of 1.724 Å and 909 cm −1 , which suggests that the 5/2 state should be the low-lying state that contributes to the experimental spectra. Moreover, the electronic states that give rise to the observed transition bands are assigned for Ω = 5/2 and 7/2 in terms of the obtained excited energies and oscillator strengths

  17. Cooperation of CMEA member states in the field of the manufacture and use of stable isotopes and compounds thus labelled

    International Nuclear Information System (INIS)

    Ertel, G.; Ewald, G.

    1977-01-01

    The contribution presents a survey of scientific-technical cooperation of CMEA member states in the field of stable isotopes, it deals with the specialization of stable isotope production and compounds thus labelled, and gives the prospects for further development of this cooperation. (HK) [de

  18. Spatial variations in food web structures with alternative stable states: evidence from stable isotope analysis in a large eutrophic lake

    Science.gov (United States)

    Li, Yunkai; Zhang, Yuying; Xu, Jun; Zhang, Shuo

    2018-03-01

    Food web structures are well known to vary widely among ecosystems. Moreover, many food web studies of lakes have generally attempted to characterize the overall food web structure and have largely ignored internal spatial and environmental variations. In this study, we hypothesize that there is a high degree of spatial heterogeneity within an ecosystem and such heterogeneity may lead to strong variations in environmental conditions and resource availability, in turn resulting in different trophic pathways. Stable carbon and nitrogen isotopes were employed for the whole food web to describe the structure of the food web in different sub-basins within Taihu Lake. This lake is a large eutrophic freshwater lake that has been intensively managed and highly influenced by human activities for more than 50 years. The results show significant isotopic differences between basins with different environmental characteristics. Such differences likely result from isotopic baseline differences combining with a shift in food web structure. Both are related to local spatial heterogeneity in nutrient loading in waters. Such variation should be explicitly considered in future food web studies and ecosystem-based management in this lake ecosystem.

  19. Spatial variations in food web structures with alternative stable states: evidence from stable isotope analysis in a large eutrophic lake

    Science.gov (United States)

    Li, Yunkai; Zhang, Yuying; Xu, Jun; Zhang, Shuo

    2017-05-01

    Food web structures are well known to vary widely among ecosystems. Moreover, many food web studies of lakes have generally attempted to characterize the overall food web structure and have largely ignored internal spatial and environmental variations. In this study, we hypothesize that there is a high degree of spatial heterogeneity within an ecosystem and such heterogeneity may lead to strong variations in environmental conditions and resource availability, in turn resulting in different trophic pathways. Stable carbon and nitrogen isotopes were employed for the whole food web to describe the structure of the food web in different sub-basins within Taihu Lake. This lake is a large eutrophic freshwater lake that has been intensively managed and highly influenced by human activities for more than 50 years. The results show significant isotopic differences between basins with different environmental characteristics. Such differences likely result from isotopic baseline differences combining with a shift in food web structure. Both are related to local spatial heterogeneity in nutrient loading in waters. Such variation should be explicitly considered in future food web studies and ecosystem-based management in this lake ecosystem.

  20. Nonlinear behavior of multiple-helicity resistive interchange modes near marginally stable states

    International Nuclear Information System (INIS)

    Sugama, Hideo; Nakajima, Noriyoshi; Wakatani, Masahiro.

    1991-05-01

    Nonlinear behavior of resistive interchange modes near marginally stable states is theoretically studied under the multiple-helicity condition. Reduced fluid equations in the sheared slab configuration are used in order to treat a local transport problem. With the use of the invariance property of local reduced fluid model equations under a transformation between the modes with different rational surfaces, weakly nonlinear theories for single-helicity modes by Hamaguchi and Nakajima are extended to the multiple-helicity case and applied to the resistive interchange modes. We derive the nonlinear amplitude equations of the multiple-helicity modes, from which the convective transport in the saturated state is obtained. It is shown how the convective transport is enhanced by nonlinear interaction between modes with different rational surfaces compared with the single-helicity case. We confirm that theoretical results are in good agreement with direct numerical simulations. (author)

  1. Excited-state properties from ground-state DFT descriptors: A QSPR approach for dyes.

    Science.gov (United States)

    Fayet, Guillaume; Jacquemin, Denis; Wathelet, Valérie; Perpète, Eric A; Rotureau, Patricia; Adamo, Carlo

    2010-02-26

    This work presents a quantitative structure-property relationship (QSPR)-based approach allowing an accurate prediction of the excited-state properties of organic dyes (anthraquinones and azobenzenes) from ground-state molecular descriptors, obtained within the (conceptual) density functional theory (DFT) framework. The ab initio computation of the descriptors was achieved at several levels of theory, so that the influence of the basis set size as well as of the modeling of environmental effects could be statistically quantified. It turns out that, for the entire data set, a statistically-robust four-variable multiple linear regression based on PCM-PBE0/6-31G calculations delivers a R(adj)(2) of 0.93 associated to predictive errors allowing for rapid and efficient dye design. All the selected descriptors are independent of the dye's family, an advantage over previously designed QSPR schemes. On top of that, the obtained accuracy is comparable to the one of the today's reference methods while exceeding the one of hardness-based fittings. QSPR relationships specific to both families of dyes have also been built up. This work paves the way towards reliable and computationally affordable color design for organic dyes. Copyright 2009 Elsevier Inc. All rights reserved.

  2. Equilibrium states and ground state of two-dimensional fluid foams

    International Nuclear Information System (INIS)

    Graner, F.; Jiang, Y.; Janiaud, E.; Flament, C.

    2001-01-01

    We study the equilibrium energies of two-dimensional (2D) noncoarsening fluid foams, which consist of bubbles with fixed areas. The equilibrium states correspond to local minima of the total perimeter. We present a theoretical derivation of energy minima; experiments with ferrofluid foams, which can be either highly distorted, locally relaxed, or globally annealed; and Monte Carlo simulations using the extended large-Q Potts model. For a dry foam with small size variance we develop physical insight and an electrostatic analogy, which enables us to (i) find an approximate value of the global minimum perimeter, accounting for (small) area disorder, the topological distribution, and physical boundary conditions; (ii) conjecture the corresponding pattern and topology: small bubbles sort inward and large bubbles sort outward, topological charges of the same signs ''repel'' while charges of the opposite signs ''attract;'' (iii) define local and global markers to determine directly from an image how far a foam is from its ground state; (iv) conjecture that, in a local perimeter minimum at prescribed topology, the pressure distribution and thus the edge curvature are unique. Some results also apply to 3D foams

  3. Fermionic molecular dynamics for ground states and collisions of nuclei

    International Nuclear Information System (INIS)

    Feldmeier, H.; Bieler, K.; Schnack, J.

    1994-08-01

    The antisymmetric many-body trial state which describes a system of interacting fermions is parametrized in terms of localized wave packets. The equations of motion are derived from the time-dependent quantum variational principle. The resulting Fermionic Molecular Dynamics (FMD) equations include a wide range of semi-quantal to classical physics extending from deformed Hartree-Fock theory to Newtonian molecular dynamics. Conservation laws are discussed in connection with the choice of the trial state. The model is applied to heavy-ion collisions with which its basic features are illustrated. The results show a great variety of phenomena including deeply inelastic collisions, fusion, incomplete fusion, fragmentation, neck emission, promptly emitted nucleons and evaporation. (orig.)

  4. Magnetic excitations in intermediate valence semiconductors with singlet ground state

    International Nuclear Information System (INIS)

    Kikoin, K.A.; Mishchenko, A.S.

    1994-01-01

    The explanation of the origin inelastic peaks in magnetic neutron scattering spectra of the mixed-valent semiconductor SmB 6 is proposed. It is shown that the excitonic theory of intermediate valence state not only gives the value of the peak frequency but also explains the unusual angular dependence of intensity of inelastic magnetic scattering and describes the dispersion of magnetic excitations in good agreement with experiment

  5. Ground state magnetic properties of Fe nanoislands on Cu(111)

    International Nuclear Information System (INIS)

    Kishi, Tomoya; David, Melanie; Nakanishi, Hiroshi; Kasai, Hideaki; Dino, Wilson Agerico; Komori, Fumio

    2005-01-01

    We investigate magnetic properties of Fe nanoislands on Cu(111) in the relaxed structure within the density functional theory. We observe that the nanoislands exhibit the ferromagnetic properties with large magnetic moment. We find that the change in the magnetic moment of each Fe atom is induced by deposition on Cu(111) and structure relaxation of Fe nanoislands. Moreover, we examine the stability of ferromagnetic states of Fe nanoislands by performing the total energy calculations. (author)

  6. Gapless Spin-Liquid Ground State in the S =1 /2 Kagome Antiferromagnet

    Science.gov (United States)

    Liao, H. J.; Xie, Z. Y.; Chen, J.; Liu, Z. Y.; Xie, H. D.; Huang, R. Z.; Normand, B.; Xiang, T.

    2017-03-01

    The defining problem in frustrated quantum magnetism, the ground state of the nearest-neighbor S =1 /2 antiferromagnetic Heisenberg model on the kagome lattice, has defied all theoretical and numerical methods employed to date. We apply the formalism of tensor-network states, specifically the method of projected entangled simplex states, which combines infinite system size with a correct accounting for multipartite entanglement. By studying the ground-state energy, the finite magnetic order appearing at finite tensor bond dimensions, and the effects of a next-nearest-neighbor coupling, we demonstrate that the ground state is a gapless spin liquid. We discuss the comparison with other numerical studies and the physical interpretation of this result.

  7. Coexisting Kondo singlet state with antiferromagnetic long-range order: A possible ground state for Kondo insulators

    International Nuclear Information System (INIS)

    Zhang Guangming; Yu Lu

    2000-04-01

    The ground-state phase diagram of a half-filled anisotropic Kondo lattice model is calculated within a mean-field theory. For small transverse exchange coupling J perpendicular perpendicular c1 , the ground state shows an antiferromagnetic long-range order with finite staggered magnetizations of both localized spins and conduction electrons. When J perpendicular > J perpendicular c2 , the long-range order is destroyed and the system is in a disordered Kondo singlet state with a hybridization gap. Both ground states can describe the low-temperature phases of Kondo insulating compounds. Between these two distinct phases, there may be a coexistent regime as a result of the balance between local Kondo screening and magnetic interactions. (author)

  8. Degenerate ground states and multiple bifurcations in a two-dimensional q-state quantum Potts model.

    Science.gov (United States)

    Dai, Yan-Wei; Cho, Sam Young; Batchelor, Murray T; Zhou, Huan-Qiang

    2014-06-01

    We numerically investigate the two-dimensional q-state quantum Potts model on the infinite square lattice by using the infinite projected entangled-pair state (iPEPS) algorithm. We show that the quantum fidelity, defined as an overlap measurement between an arbitrary reference state and the iPEPS ground state of the system, can detect q-fold degenerate ground states for the Z_{q} broken-symmetry phase. Accordingly, a multiple bifurcation of the quantum ground-state fidelity is shown to occur as the transverse magnetic field varies from the symmetry phase to the broken-symmetry phase, which means that a multiple-bifurcation point corresponds to a critical point. A (dis)continuous behavior of quantum fidelity at phase transition points characterizes a (dis)continuous phase transition. Similar to the characteristic behavior of the quantum fidelity, the magnetizations, as order parameters, obtained from the degenerate ground states exhibit multiple bifurcation at critical points. Each order parameter is also explicitly demonstrated to transform under the Z_{q} subgroup of the symmetry group of the Hamiltonian. We find that the q-state quantum Potts model on the square lattice undergoes a discontinuous (first-order) phase transition for q=3 and q=4 and a continuous phase transition for q=2 (the two-dimensional quantum transverse Ising model).

  9. g-factor of the ground state of 73Se

    International Nuclear Information System (INIS)

    Nishimura, Katsuhiko; Ohya, Susumu; Mutsuro, Naoshi

    1987-01-01

    Nuclear magnetic resonance on oriented 73 Se in an iron host has been observed at about 7mK. From resonance-shift measurement, the magnetic hyperfine-splitting frequency μ M , g-factor and magnetic hyperfine field were derived as μ M =102.61(3)MH z , |g(9/2 + )|=0.188(16) and B HF ( 73 SeFe)=716(81)kG. The experimental values of the g-factors of the g 9/2 neutron states, in the neighborhood of the neutron number 40, are compared with the theoretical values based on the core-polarization model. (author)

  10. Engineering an all-optical route to ultracold molecules in their vibronic ground state

    OpenAIRE

    Koch, Christiane P.; Moszynski, Robert

    2008-01-01

    We propose an improved photoassociation scheme to produce ultracold molecules in their vibronic ground state for the generic case where non-adiabatic effects facilitating transfer to deeply bound levels are absent. Formation of molecules is achieved by short laser pulses in a Raman-like pump-dump process where an additional near-infrared laser field couples the excited state to an auxiliary state. The coupling due to the additional field effectively changes the shape of the excited state pote...

  11. Indolo[2,3-b]carbazoles with tunable ground states: How Clar's aromatic sextet determines the singlet biradical character

    KAUST Repository

    Luo, Ding

    2014-01-01

    Polycyclic hydrocarbons (PHs) with a singlet biradical ground state have recently attracted extensive interest in physical organic chemistry and materials science. Replacing the carbon radical center in the open-shell PHs with a more electronegative nitrogen atom is expected to result in the more stable aminyl radical. In this work, two kinetically blocked stable/persistent derivatives (1 and 2) of indolo[2,3-b]carbazole, an isoelectronic structure of the known indeno[2,1-b]fluorene, were synthesized and showed different ground states. Based on variable-temperature NMR/ESR measurements and density functional theory calculations, it was found that the indolo[2,3-b]carbazole derivative 1 is a persistent singlet biradical in the ground state with a moderate biradical character (y0 = 0.269) and a small singlet-triplet energy gap (ΔES-T ≅ -1.78 kcal mol-1), while the more extended dibenzo-indolo[2,3-b]carbazole 2 exhibits a quinoidal closed-shell ground state. The difference can be explained by considering the number of aromatic sextet rings gained from the closed-shell to the open-shell biradical resonance form, that is to say, two for compound 1 and one for compound 2, which determines their different biradical characters. The optical and electronic properties of 2 and the corresponding aromatic precursors were investigated by one-photon absorption, transient absorption and two-photon absorption (TPA) spectroscopies and electrochemistry. Amphoteric redox behaviour, a short excited lifetime and a moderate TPA cross section were observed for 2, which can be correlated to its antiaromaticity and small biradical character. Compound 2 showed high reactivity to protic solvents due to its extremely low-lying LUMO energy level. Unusual oxidative dimerization was also observed for the unblocked dihydro-indolo[2,3-b]carbazole precursors 6 and 11. Our studies shed light on the rational design of persistent aminyl biradicals with tunable properties in the future. This journal

  12. Exponentially Biased Ground-State Sampling of Quantum Annealing Machines with Transverse-Field Driving Hamiltonians.

    Science.gov (United States)

    Mandrà, Salvatore; Zhu, Zheng; Katzgraber, Helmut G

    2017-02-17

    We study the performance of the D-Wave 2X quantum annealing machine on systems with well-controlled ground-state degeneracy. While obtaining the ground state of a spin-glass benchmark instance represents a difficult task, the gold standard for any optimization algorithm or machine is to sample all solutions that minimize the Hamiltonian with more or less equal probability. Our results show that while naive transverse-field quantum annealing on the D-Wave 2X device can find the ground-state energy of the problems, it is not well suited in identifying all degenerate ground-state configurations associated with a particular instance. Even worse, some states are exponentially suppressed, in agreement with previous studies on toy model problems [New J. Phys. 11, 073021 (2009)NJOPFM1367-263010.1088/1367-2630/11/7/073021]. These results suggest that more complex driving Hamiltonians are needed in future quantum annealing machines to ensure a fair sampling of the ground-state manifold.

  13. Ground state energy and width of 7He from 8Li proton knockout

    International Nuclear Information System (INIS)

    Denby, D. H.; DeYoung, P. A.; Hall, C. C.; Baumann, T.; Bazin, D.; Spyrou, A.; Breitbach, E.; Howes, R.; Brown, J.; Frank, N.; Gade, A.; Mosby, S. M.; Peters, W. A.; Thoennessen, M.; Hinnefeld, J.; Hoffman, C. R.; Jenson, R. A.; Luther, B.; Olson, C. W.; Schiller, A.

    2008-01-01

    The ground state energy and width of 7 He has been measured with the Modular Neutron Array (MoNA) and superconducting dipole Sweeper magnet experimental setup at the National Superconducting Cyclotron Laboratory. 7 He was produced by proton knockout from a secondary 8 Li beam. The measured decay energy spectrum is compared to simulations based on Breit-Wigner line shape with an energy-dependent width for the resonant state. The energy of the ground state is found to be 400(10) keV with a full-width at half-maximum of 125( -15 +40 ) keV

  14. Extended random-phase approximation with three-body ground-state correlations

    International Nuclear Information System (INIS)

    Tohyama, M.; Schuck, P.

    2008-01-01

    An extended random-phase approximation (ERPA) which contains the effects of ground-state correlations up to a three-body level is applied to an extended Lipkin model which contains an additional particle-scattering term. Three-body correlations in the ground state are necessary to preserve the hermiticity of the Hamiltonian matrix of ERPA. Two approximate forms of ERPA which neglect the three-body correlations are also applied to investigate the importance of three-body correlations. It is found that the ground-state energy is little affected by the inclusion of the three-body correlations. On the contrary, three-body correlations for the excited states can become quite important. (orig.)

  15. Quantum ground state and single-phonon control of a mechanical resonator.

    Science.gov (United States)

    O'Connell, A D; Hofheinz, M; Ansmann, M; Bialczak, Radoslaw C; Lenander, M; Lucero, Erik; Neeley, M; Sank, D; Wang, H; Weides, M; Wenner, J; Martinis, John M; Cleland, A N

    2010-04-01

    Quantum mechanics provides a highly accurate description of a wide variety of physical systems. However, a demonstration that quantum mechanics applies equally to macroscopic mechanical systems has been a long-standing challenge, hindered by the difficulty of cooling a mechanical mode to its quantum ground state. The temperatures required are typically far below those attainable with standard cryogenic methods, so significant effort has been devoted to developing alternative cooling techniques. Once in the ground state, quantum-limited measurements must then be demonstrated. Here, using conventional cryogenic refrigeration, we show that we can cool a mechanical mode to its quantum ground state by using a microwave-frequency mechanical oscillator-a 'quantum drum'-coupled to a quantum bit, which is used to measure the quantum state of the resonator. We further show that we can controllably create single quantum excitations (phonons) in the resonator, thus taking the first steps to complete quantum control of a mechanical system.

  16. Learning Approach on the Ground State Energy Calculation of Helium Atom

    International Nuclear Information System (INIS)

    Shah, Syed Naseem Hussain

    2010-01-01

    This research investigated the role of learning approach on the ground state energy calculation of Helium atom in improving the concepts of science teachers at university level. As the exact solution of several particles is not possible here we used approximation methods. Using this method one can understand easily the calculation of ground state energy of any given function. Variation Method is one of the most useful approximation methods in estimating the energy eigen values of the ground state and the first few excited states of a system, which we only have a qualitative idea about the wave function.The objective of this approach is to introduce and involve university teacher in new research, to improve their class room practices and to enable teachers to foster critical thinking in students.

  17. Probing the 8He ground state via the 8He(p,t)6He reaction

    International Nuclear Information System (INIS)

    Keeley, N.; Skaza, F.; Lapoux, V.; Alamanos, N.; Auger, F.; Beaumel, D.; Becheva, E.; Blumenfeld, Y.; Delaunay, F.; Drouart, A.; Gillibert, A.; Giot, L.; Kemper, K.W.; Nalpas, L.; Pakou, A.; Pollacco, E.C.; Raabe, R.; Roussel-Chomaz, P.; Rusek, K.; Scarpaci, J.-A.; Sida, J.-L.; Stepantsov, S.; Wolski, R.

    2007-01-01

    The weakly-bound 8 He nucleus exhibits a neutron halo or thick neutron skin and is generally considered to have an α+4n structure in its ground state, with the four valence neutrons each occupying 1p 3/2 states outside the α core. The 8 He(p,t) 6 He reaction is a sensitive probe of the ground state structure of 8 He, and we present a consistent analysis of new and existing data for this reaction at incident energies of 15.7 and 61.3A MeV, respectively. Our results are incompatible with the usual assumption of a pure (1p 3/2 ) 4 structure and suggest that other configurations such as (1p 3/2 ) 2 (1p 1/2 ) 2 may be present with significant probability in the ground state wave function of 8 He

  18. Winter diets of immature green turtles (Chelonia mydas) on a northern feeding ground: integrating stomach contents and stable isotope analyses

    Science.gov (United States)

    Williams, Natalie C.; Bjorndal, Karen A.; Lamont, Margaret M.; Carthy, Raymond R.

    2015-01-01

    The foraging ecology and diet of the green turtle, Chelonia mydas, remain understudied, particularly in peripheral areas of its distribution. We assessed the diet of an aggregation of juvenile green turtles at the northern edge of its range during winter months using two approaches. Stomach content analyses provide a single time sample, and stable isotope analyses integrate diet over a several-month period. We evaluated diet consistency in prey choice over time by comparing the results of these two approaches. We examined stomach contents from 43 juvenile green turtles that died during cold stunning events in St. Joseph Bay, Florida, in 2008 and 2011. Stomach contents were evaluated for volume, dry mass, percent frequency of occurrence, and index of relative importance of individual diet items. Juvenile green turtles were omnivorous, feeding primarily on seagrasses and tunicates. Diet characterizations from stomach contents differed from those based on stable isotope analyses, indicating the turtles are not feeding consistently during winter months. Evaluation of diets during warm months is needed.

  19. Ground water share in supplying domestic water in Khartoum state

    International Nuclear Information System (INIS)

    Mohammed, M. E. A.

    2010-10-01

    In this research study of the sources of groundwater from wells and stations that rely on the national authority for urban water in the state of Khartoum, this study includes three areas, namely the Khartoum area, North Khartoum and Omdurman area. This research evaluate and identify the sources of groundwater from wells and stations and find out the productivity of wells and underground stations. The study period were identified from 2004 to 2008 during this commoners were Alabaralgeoffip Knowledge Production and stations from the water. The methods used in this study was to determine the sources of groundwater from wells and stations in the three areas with the knowledge of the percentage in each year and the total amount of water produced from wells and stations in Khartoum, North Khartoum and Omdurman it is clear from this study that the percentage of productivity in the annual increase to varying degrees in floater from 2004 to 2008 and also clear that the Omdurman area depends on groundwater wells over a maritime area of stations based on stations with more and more consumption of Khartoum and the sea. Also been identified on the tank top and bottom of the tank where the chemical properties and physical properties after the identification of these qualities and characteristics have been identified the quantity and quality of water produced from wells and stations. (Author)

  20. Ground state properties of MnB{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Winter, Jan Lennart; Steinki, Nico; Schulze Grachtrup, Dirk; Menzel, Dirk; Suellow, Stefan [Institut fuer Physik der Kondensierten Materie, TU Braunschweig (Germany); Knappschneider, Arno; Albert, Barbara [Eduard-Zintl-Institut fuer Anorganische und Physikalische Chemie, TU Darmstadt (Germany)

    2016-07-01

    Recently, single crystalline MnB{sub 4} was synthesized for the first time, yielding microscale crystals with dimensions of the order of 200 μm. Based on band structure calculations, it was argued that the material is semiconducting as result of a Peierls distortion. Conversely, in a study of polycrystalline material it was concluded that the material is a weakly ferromagnetic metal. To establish if MnB{sub 4} is a semiconductor we have carried out single crystal four point resistivity measurements. For this purpose a setup for measuring microscale samples was developed and characterized. Qualitatively, we find semiconducting behavior (increasing resistivity for decreasing temperature), although a band gap could not be derived because of a non-linear Arrhenius plot. Our data are consistent with MnB{sub 4} being a pseudogap/small gap material as proposed. A pronounced sample dependence of the transport properties points to the presence of impurity states. For the single crystals no ferromagnetic signatures could be obtained, suggesting an extrinsic cause of it in polycrystalline material.

  1. Stability and related properties of vacua and ground states

    International Nuclear Information System (INIS)

    Wreszinski, Walter F.; Jaekel, Christian D.

    2008-01-01

    We consider the formal non-relativistic limit (nrl) of the :φ 4 : s+1 relativistic quantum field theory (rqft), where s is the space dimension. Following the work of R. Jackiw [R. Jackiw, in: A. Ali, P. Hoodbhoy (Eds.), Beg Memorial Volume, World Scientific, Singapore, 1991], we show that, for s = 2 and a given value of the ultraviolet cutoff κ, there are two ways to perform the nrl: (i) fixing the renormalized mass m 2 equal to the bare mass m 0 2 ; (ii) keeping the renormalized mass fixed and different from the bare mass m 0 2 . In the (infinite-volume) two-particle sector the scattering amplitude tends to zero as κ → ∞ in case (i) and, in case (ii), there is a bound state, indicating that the interaction potential is attractive. As a consequence, stability of matter fails for our boson system. We discuss why both alternatives do not reproduce the low-energy behaviour of the full rqft. The singular nature of the nrl is also nicely illustrated for s = 1 by a rigorous stability/instability result of a different nature

  2. Democratic Republic of Congo A Fertile Ground for Instability in the Great Lakes Region States

    Science.gov (United States)

    2017-06-09

    ravaged by a brutal armed conflict. In comparison to the three past presidents, Joseph Kabila has managed to restore political stability and calm to much...DEMOCRATIC REPUBLIC OF CONGO-A FERTILE GROUND FOR INSTABILITY IN THE GREAT LAKES REGION STATES A thesis presented to the Faculty of...From - To) AUG 2016 – JUNE 2017 4. TITLE AND SUBTITLE Democratic Republic of Congo-A Fertile Ground for Instability in the Great Lakes Region

  3. Effects of marine protected areas on overfished fishing stocks with multiple stable states.

    Science.gov (United States)

    Takashina, Nao; Mougi, Akihiko

    2014-01-21

    Marine protected areas (MPAs) have attracted much attention as a tool for sustainable fisheries management, restoring depleted fisheries stocks and maintaining ecosystems. However, even with total exclusion of fishing effort, depleted stocks sometimes show little or no recovery over a long time period. Here, using a mathematical model, we show that multiple stable states may hold the key to understanding the tendency for fisheries stocks to recover because of MPAs. We find that MPAs can have either a positive effect or almost no effect on the recovery of depleted fishing stocks, depending on the fish migration patterns and the fishing policies. MPAs also reinforce ecological resilience, particularly for migratory species. In contrast to previous reports, our results show that MPAs have small or sometimes negative effects on the recovery of sedentary species. Unsuitable MPA planning might result in low effectiveness or even deterioration of the existing condition. © 2013 Elsevier Ltd. All rights reserved.

  4. Construction of ground-state preserving sparse lattice models for predictive materials simulations

    Science.gov (United States)

    Huang, Wenxuan; Urban, Alexander; Rong, Ziqin; Ding, Zhiwei; Luo, Chuan; Ceder, Gerbrand

    2017-08-01

    First-principles based cluster expansion models are the dominant approach in ab initio thermodynamics of crystalline mixtures enabling the prediction of phase diagrams and novel ground states. However, despite recent advances, the construction of accurate models still requires a careful and time-consuming manual parameter tuning process for ground-state preservation, since this property is not guaranteed by default. In this paper, we present a systematic and mathematically sound method to obtain cluster expansion models that are guaranteed to preserve the ground states of their reference data. The method builds on the recently introduced compressive sensing paradigm for cluster expansion and employs quadratic programming to impose constraints on the model parameters. The robustness of our methodology is illustrated for two lithium transition metal oxides with relevance for Li-ion battery cathodes, i.e., Li2xFe2(1-x)O2 and Li2xTi2(1-x)O2, for which the construction of cluster expansion models with compressive sensing alone has proven to be challenging. We demonstrate that our method not only guarantees ground-state preservation on the set of reference structures used for the model construction, but also show that out-of-sample ground-state preservation up to relatively large supercell size is achievable through a rapidly converging iterative refinement. This method provides a general tool for building robust, compressed and constrained physical models with predictive power.

  5. Mowing Submerged Macrophytes in Shallow Lakes with Alternative Stable States: Battling the Good Guys?

    Science.gov (United States)

    Kuiper, Jan J.; Verhofstad, Michiel J. J. M.; Louwers, Evelien L. M.; Bakker, Elisabeth S.; Brederveld, Robert J.; van Gerven, Luuk P. A.; Janssen, Annette B. G.; de Klein, Jeroen J. M.; Mooij, Wolf M.

    2017-04-01

    Submerged macrophytes play an important role in maintaining good water quality in shallow lakes. Yet extensive stands easily interfere with various services provided by these lakes, and harvesting is increasingly applied as a management measure. Because shallow lakes may possess alternative stable states over a wide range of environmental conditions, designing a successful mowing strategy is challenging, given the important role of macrophytes in stabilizing the clear water state. In this study, the integrated ecosystem model PCLake is used to explore the consequences of mowing, in terms of reducing nuisance and ecosystem stability, for a wide range of external nutrient loadings, mowing intensities and timings. Elodea is used as a model species. Additionally, we use PCLake to estimate how much phosphorus is removed with the harvested biomass, and evaluate the long-term effect of harvesting. Our model indicates that mowing can temporarily reduce nuisance caused by submerged plants in the first weeks after cutting, particularly when external nutrient loading is fairly low. The risk of instigating a regime shift can be tempered by mowing halfway the growing season when the resilience of the system is highest, as our model showed. Up to half of the phosphorus entering the system can potentially be removed along with the harvested biomass. As a result, prolonged mowing can prevent an oligo—to mesotrophic lake from becoming eutrophic to a certain extent, as our model shows that the critical nutrient loading, where the lake shifts to the turbid phytoplankton-dominated state, can be slightly increased.

  6. Modeling of the stress-strain state of the ground mass contaminated with peracetic acid

    Directory of Open Access Journals (Sweden)

    Levenko Anna

    2017-01-01

    Full Text Available None of the methods described previously provides a solution to the problem that deals with the SSS evaluation of the ground mass which is under the influence of chemically active substances and, in particular, under the influence of peracetic acid. The stress-strain state of the ground mass contaminated with peracetic acid was estimated. Stresses occurring in the ground mass in the natural state were determined after the entry of acid into it and after the chemical fixation of it with sodium silicate. All the parameters of the stress-strain state of the ground mass were obtained under a number of physical and mechanical conditions. It was determined that following the work on the silicatization of the ground mass contaminated with peracetic acid the quantity of strain decreased by 26.11 to 48.9%. The comparison of the results of stress calculations indicates the stress reduction in the ground mass in 1.8 – 2.6 times after its fixing.

  7. Stable isotopes of hydrogen and oxygen in surface water and ground water at selected sites on or near the Idaho National Engineering Laboratory, Idaho

    International Nuclear Information System (INIS)

    Ott, D.S.; Cecil, L.D.; Knobel, L.L.

    1994-01-01

    Relative stable isotopic ratios for hydrogen and oxygen compared to standard mean ocean water are presented for water from 4 surface-water sites and 38 ground-water sites on or near the Idaho National Engineering Laboratory (INEL). The surface-water samples were collected monthly from March 1991 through April 1992 and after a storm event on June 18, 1992. The ground-water samples either were collected during 1991 or 1992. These data were collected as part of the US Geological Survey's continuing hydrogeological investigations at the INEL. The relative isotopic ratios of hydrogen and oxygen are reported as delta 2 H (δ 2 H) and as delta 18 O (δ 18 O), respectively. The values of δ 2 H and δ 18 O in water from the four surface-water sites ranged from -143.0 to -122 and from -18.75 to -15.55, respectively. The values of δ 2 H and δ 18 O in water from the 38 ground-water sites ranged from -141.0 to -120.0 and from -18.55 to -14.95, respectively

  8. Structural Distortion Stabilizing the Antiferromagnetic and Semiconducting Ground State of BaMn2As2

    Directory of Open Access Journals (Sweden)

    Ekkehard Krüger

    2016-09-01

    Full Text Available We report evidence that the experimentally found antiferromagnetic structure as well as the semiconducting ground state of BaMn 2 As 2 are caused by optimally-localized Wannier states of special symmetry existing at the Fermi level of BaMn 2 As 2 . In addition, we find that a (small tetragonal distortion of the crystal is required to stabilize the antiferromagnetic semiconducting state. To our knowledge, this distortion has not yet been established experimentally.

  9. Van der Waals potential and vibrational energy levels of the ground state radon dimer

    Science.gov (United States)

    Sheng, Xiaowei; Qian, Shifeng; Hu, Fengfei

    2017-08-01

    In the present paper, the ground state van der Waals potential of the Radon dimer is described by the Tang-Toennies potential model, which requires five essential parameters. Among them, the two dispersion coefficients C6 and C8 are estimated from the well determined dispersion coefficients C6 and C8 of Xe2. C10 is estimated by using the approximation equation that C6C10/C82 has an average value of 1.221 for all the rare gas dimers. With these estimated dispersion coefficients and the well determined well depth De and Re the Born-Mayer parameters A and b are derived. Then the vibrational energy levels of the ground state radon dimer are calculated. 40 vibrational energy levels are observed in the ground state of Rn2 dimer. The last vibrational energy level is bound by only 0.0012 cm-1.

  10. Antibonding hole ground state in InAs quantum dot molecules

    Energy Technology Data Exchange (ETDEWEB)

    Planelles, Josep [Departament de Química Física i Analítica, Universitat Jaume I, E-12080, Castelló (Spain)

    2015-01-22

    Using four-band k⋅p Hamiltonians, we study how strain and position-dependent effective masses influence hole tunneling in vertically coupled InAs/GaAs quantum dots. Strain reduces the tunneling and hence the critical interdot distance required for the ground state to change from bonding to antibonding. Variable mass has the opposite effect and a rough compensation leaves little affected the critical bonding-to-antibonding ground state crossover. An alternative implementation of the magnetic field in the envelope function Hamiltonian is given which retrieves the experimental denial of possible after growth reversible magnetically induced bonding-to-antibonding ground state transition, predicted by the widely used Luttinger-Kohn Hamiltonian.

  11. Exact ground-state correlation functions of an atomic-molecular Bose–Einstein condensate model

    Science.gov (United States)

    Links, Jon; Shen, Yibing

    2018-05-01

    We study the ground-state properties of an atomic-molecular Bose–Einstein condensate model through an exact Bethe Ansatz solution. For a certain range of parameter choices, we prove that the ground-state Bethe roots lie on the positive real-axis. We then use a continuum limit approach to obtain a singular integral equation characterising the distribution of these Bethe roots. Solving this equation leads to an analytic expression for the ground-state energy. The form of the expression is consistent with the existence of a line of quantum phase transitions, which has been identified in earlier studies. This line demarcates a molecular phase from a mixed phase. Certain correlation functions, which characterise these phases, are then obtained through the Hellmann–Feynman theorem.

  12. Numerical simulations of oscillating soliton stars: Excited states in spherical symmetry and ground state evolutions in 3D

    International Nuclear Information System (INIS)

    Balakrishna, Jayashree; Bondarescu, Ruxandra; Daues, Gregory; Bondarescu, Mihai

    2008-01-01

    Excited state soliton stars are studied numerically for the first time. The stability of spherically symmetric S-branch excited state oscillatons under radial perturbations is investigated using a 1D code. We find that these stars are inherently unstable either migrating to the ground state or collapsing to black holes. Higher excited state configurations are observed to cascade through intermediate excited states during their migration to the ground state. This is similar to excited state boson stars [J. Balakrishna, E. Seidel, and W.-M. Suen, Phys. Rev. D 58, 104004 (1998).]. Ground state oscillatons are then studied in full 3D numerical relativity. Finding the appropriate gauge condition for the dynamic oscillatons is much more challenging than in the case of boson stars. Different slicing conditions are explored, and a customized gauge condition that approximates polar slicing in spherical symmetry is implemented. Comparisons with 1D results and convergence tests are performed. The behavior of these stars under small axisymmetric perturbations is studied and gravitational waveforms are extracted. We find that the gravitational waves damp out on a short time scale, enabling us to obtain the complete waveform. This work is a starting point for the evolution of real scalar field systems with arbitrary symmetries

  13. Non-degenerated Ground States and Low-degenerated Excited States in the Antiferromagnetic Ising Model on Triangulations

    Science.gov (United States)

    Jiménez, Andrea

    2014-02-01

    We study the unexpected asymptotic behavior of the degeneracy of the first few energy levels in the antiferromagnetic Ising model on triangulations of closed Riemann surfaces. There are strong mathematical and physical reasons to expect that the number of ground states (i.e., degeneracy) of the antiferromagnetic Ising model on the triangulations of a fixed closed Riemann surface is exponential in the number of vertices. In the set of plane triangulations, the degeneracy equals the number of perfect matchings of the geometric duals, and thus it is exponential by a recent result of Chudnovsky and Seymour. From the physics point of view, antiferromagnetic triangulations are geometrically frustrated systems, and in such systems exponential degeneracy is predicted. We present results that contradict these predictions. We prove that for each closed Riemann surface S of positive genus, there are sequences of triangulations of S with exactly one ground state. One possible explanation of this phenomenon is that exponential degeneracy would be found in the excited states with energy close to the ground state energy. However, as our second result, we show the existence of a sequence of triangulations of a closed Riemann surface of genus 10 with exactly one ground state such that the degeneracy of each of the 1st, 2nd, 3rd and 4th excited energy levels belongs to O( n), O( n 2), O( n 3) and O( n 4), respectively.

  14. Mechanical properties of ground state structures in substitutional ordered alloys: High strength, high ductility and high thermal stability

    International Nuclear Information System (INIS)

    Tawancy, H.M.; Aboelfotoh, M.O.

    2014-01-01

    We have studied the effect of atom arrangements in the ground state structures of substitutional ordered alloys on their mechanical properties using nickel–molybdenum-based alloys as model systems. Three alloys with nominal compositions of Ni–19.43 at% Mo, Ni–18.53 at% Mo–15.21 at% Cr and Ni–18.72 at% Mo–6.14 at% Nb are included in the study. In agreement with theoretical predictions, the closely related Pt 2 Mo-type, DO 22 and D1 a superlattices with similar energies are identified by electron diffraction of ground state structures, which can directly be derived from the parent disordered fcc structure by minor atom rearrangements on {420} fcc planes. The three superlattices are observed to coexist during the disorder–order transformation at 700 °C with the most stable superlattice being determined by the exact chemical composition. Although most of the slip systems in the parent disordered fcc structure are suppressed, many of the twinning systems remain operative in the superlattices favoring deformation by twinning, which leads to considerable strengthening while maintaining high ductility levels. Both the Pt 2 Mo-type and DO 22 superlattices are distinguished by high strength and high ductility due to their nanoscale microstructures, which have high thermal stability. However, the D1 a superlattice is found to exhibit poor thermal stability leading to considerable loss of ductility, which has been correlated with self-induced recrystallization by migration of grain boundaries

  15. Stability of the electroweak ground state in the Standard Model and its extensions

    International Nuclear Information System (INIS)

    Di Luzio, Luca; Isidori, Gino; Ridolfi, Giovanni

    2016-01-01

    We review the formalism by which the tunnelling probability of an unstable ground state can be computed in quantum field theory, with special reference to the Standard Model of electroweak interactions. We describe in some detail the approximations implicitly adopted in such calculation. Particular attention is devoted to the role of scale invariance, and to the different implications of scale-invariance violations due to quantum effects and possible new degrees of freedom. We show that new interactions characterized by a new energy scale, close to the Planck mass, do not invalidate the main conclusions about the stability of the Standard Model ground state derived in absence of such terms.

  16. Stability of the electroweak ground state in the Standard Model and its extensions

    Energy Technology Data Exchange (ETDEWEB)

    Di Luzio, Luca, E-mail: diluzio@ge.infn.it [Dipartimento di Fisica, Università di Genova and INFN, Sezione di Genova, Via Dodecaneso 33, I-16146 Genova (Italy); Isidori, Gino [Department of Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich (Switzerland); Ridolfi, Giovanni [Dipartimento di Fisica, Università di Genova and INFN, Sezione di Genova, Via Dodecaneso 33, I-16146 Genova (Italy)

    2016-02-10

    We review the formalism by which the tunnelling probability of an unstable ground state can be computed in quantum field theory, with special reference to the Standard Model of electroweak interactions. We describe in some detail the approximations implicitly adopted in such calculation. Particular attention is devoted to the role of scale invariance, and to the different implications of scale-invariance violations due to quantum effects and possible new degrees of freedom. We show that new interactions characterized by a new energy scale, close to the Planck mass, do not invalidate the main conclusions about the stability of the Standard Model ground state derived in absence of such terms.

  17. Stability of the electroweak ground state in the Standard Model and its extensions

    Directory of Open Access Journals (Sweden)

    Luca Di Luzio

    2016-02-01

    Full Text Available We review the formalism by which the tunnelling probability of an unstable ground state can be computed in quantum field theory, with special reference to the Standard Model of electroweak interactions. We describe in some detail the approximations implicitly adopted in such calculation. Particular attention is devoted to the role of scale invariance, and to the different implications of scale-invariance violations due to quantum effects and possible new degrees of freedom. We show that new interactions characterized by a new energy scale, close to the Planck mass, do not invalidate the main conclusions about the stability of the Standard Model ground state derived in absence of such terms.

  18. Ground State of Bosons in Bose-Fermi Mixture with Spin-Orbit Coupling

    Science.gov (United States)

    Sakamoto, Ryohei; Ono, Yosuke; Hatsuda, Rei; Shiina, Kenta; Arahata, Emiko; Mori, Hiroyuki

    2017-07-01

    We study an effect of spin-1/2 fermions on the ground state of a Bose system with equal Rashba and Dresselhaus spin-orbit coupling. By using mean-field and tight-binding approximations, we show the ground state phase diagram of the Bose system in the spin-orbit coupled Bose-Fermi mixture and find that the characteristic phase domain, where a spin current of fermions may be induced, can exist even in the presence of a significantly large number of fermions.

  19. Numerical study of the t-J model: Exact ground state and flux phases

    International Nuclear Information System (INIS)

    Hasegawa, Y.; Poilblanc, D.

    1990-01-01

    Strongly correlated 2D electrons described by the t-J model are investigated numerically. Exact ground state for one and two holes in a finite cluster with periodic boundary conditions are obtained by using the Lanczos algorithm. The effects of Coulomb repulsion of the holes on the nearest neighbor sites are taken into account. Commensurate flux phases are investigated for the same size of clusters. They are shown to be a good approximation for the ground state specially in the intermediate value of J/t. (author). 21 refs, 3 figs

  20. Numerical study of ground state and low lying excitations of quantum antiferromagnets

    International Nuclear Information System (INIS)

    Trivedi, N.; Ceperley, D.M.

    1989-01-01

    The authors have studied, via Green function Monte Carlo (GFMC), the S = 1/2 Heisenberg quantum antiferromagnet in two dimensions on a square lattice. They obtain the ground state energy with only statistical errors E 0 /J = -0.6692(2), the staggered magnetization m † = 0.31(2), and from the long wave length behavior of the structure factor, the spin wave velocity c/c o = 1.14(5). They show that the ground state wave function has long range pair correlations arising from the zero point motion of spin waves

  1. The ground-state phase diagrams of the spin-3/2 Ising model

    International Nuclear Information System (INIS)

    Canko, Osman; Keskin, Mustafa

    2003-01-01

    The ground-state spin configurations are obtained for the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic exchange interactions and a single-ion crystal field. The interactions are assumed to be only between nearest-neighbors. The calculated ground-state phase diagrams are presented on diatomic lattices, such as the square, honeycomb and sc lattices, and triangular lattice in the (Δ/z vertical bar J vertical bar ,K/ vertical bar J vertical bar) and (H/z vertical bar J vertical bar, K/ vertical bar J vertical bar) planes

  2. Singlet Ground State Magnetism: III Magnetic Excitons in Antiferromagnetic TbP

    DEFF Research Database (Denmark)

    Knorr, K.; Loidl, A.; Kjems, Jørgen

    1981-01-01

    The dispersion of the lowest magnetic excitations of the singlet ground state system TbP has been studied in the antiferromagnetic phase by inelastic neutron scattering. The magnetic exchange interaction and the magnetic and the rhombohedral molecular fields have been determined.......The dispersion of the lowest magnetic excitations of the singlet ground state system TbP has been studied in the antiferromagnetic phase by inelastic neutron scattering. The magnetic exchange interaction and the magnetic and the rhombohedral molecular fields have been determined....

  3. Ground-state properties of third-row elements with nonlocal density functionals

    International Nuclear Information System (INIS)

    Bagno, P.; Jepsen, O.; Gunnarsson, O.

    1989-01-01

    The cohesive energy, the lattice parameter, and the bulk modulus of third-row elements are calculated using the Langreth-Mehl-Hu (LMH), the Perdew-Wang (PW), and the gradient expansion functionals. The PW functional is found to give somewhat better results than the LMH functional and both are found to typically remove half the errors in the local-spin-density (LSD) approximation, while the gradient expansion gives worse results than the local-density approximation. For Fe both the LMH and PW functionals correctly predict a ferromagnetic bcc ground state, while the LSD approximation and the gradient expansion predict a nonmagnetic fcc ground state

  4. Traces of Lorentz symmetry breaking in a hydrogen atom at ground state

    Science.gov (United States)

    Borges, L. H. C.; Barone, F. A.

    2016-02-01

    Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schrödinger perturbation theory in order to obtain the corrections to the ground state energy and the wave function. It is shown that an induced four-pole moment arises, due to the Lorentz symmetry breaking. The model considered is the one studied in Borges et al. (Eur Phys J C 74:2937, 2014), where the Lorentz symmetry is broken in the electromagnetic sector.

  5. Traces of Lorentz symmetry breaking in a hydrogen atom at ground state

    Energy Technology Data Exchange (ETDEWEB)

    Borges, L.H.C. [Universidade Federal do ABC, Centro de Ciencias Naturais e Humanas, Santo Andre, SP (Brazil); Barone, F.A. [IFQ-Universidade Federal de Itajuba, Itajuba, MG (Brazil)

    2016-02-15

    Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schroedinger perturbation theory in order to obtain the corrections to the ground state energy and the wave function. It is shown that an induced four-pole moment arises, due to the Lorentz symmetry breaking. The model considered is the one studied in Borges et al. (Eur Phys J C 74:2937, 2014), where the Lorentz symmetry is broken in the electromagnetic sector. (orig.)

  6. Traces of Lorentz symmetry breaking in a hydrogen atom at ground state

    International Nuclear Information System (INIS)

    Borges, L.H.C.; Barone, F.A.

    2016-01-01

    Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schroedinger perturbation theory in order to obtain the corrections to the ground state energy and the wave function. It is shown that an induced four-pole moment arises, due to the Lorentz symmetry breaking. The model considered is the one studied in Borges et al. (Eur Phys J C 74:2937, 2014), where the Lorentz symmetry is broken in the electromagnetic sector. (orig.)

  7. On the ground state of the two-dimensional non-ideal Bose gas

    International Nuclear Information System (INIS)

    Lozovik, Yu.E.; Yudson, V.I.

    1978-01-01

    The theory of the ground state of the two-dimensional non-ideal Bose gas is presented. The conditions for the validity of the ladder and the Bogolubov approximations are derived. These conditions ensure the existence of a Bose condensate in the ground state of two-dimensional systems. These conditions are different from the corresponding conditions for the three-dimensional case. The connection between the effective interaction and the two-dimensional scattering amplitude at some characteristic energy kappa 2 /2m (not equal to 0) is obtained (f(kappa = 0) = infinity in the two-dimensional case). (Auth.)

  8. Ground-state configuration of neutron-rich Aluminum isotopes through Coulomb Breakup

    Directory of Open Access Journals (Sweden)

    Chakraborty S.

    2014-03-01

    Full Text Available Neutron-rich 34,35Al isotopes have been studied through Coulomb excitation using LAND-FRS setup at GSI, Darmstadt. The method of invariant mass analysis has been used to reconstruct the excitation energy of the nucleus prior to decay. Comparison of experimental CD cross-section with direct breakup model calculation with neutron in p3/2 orbital favours 34Al(g.s⊗νp3/2 as ground state configuration of 35Al. But ground state configuration of 34Al is complicated as evident from γ-ray spectra of 33Al after Coulomb breakup of 34Al.

  9. Trapping cold ground state argon atoms for sympathetic cooling of molecules

    OpenAIRE

    Edmunds, P. D.; Barker, P. F.

    2014-01-01

    We trap cold, ground-state, argon atoms in a deep optical dipole trap produced by a build-up cavity. The atoms, which are a general source for the sympathetic cooling of molecules, are loaded in the trap by quenching them from a cloud of laser-cooled metastable argon atoms. Although the ground state atoms cannot be directly probed, we detect them by observing the collisional loss of co-trapped metastable argon atoms using a new type of parametric loss spectroscopy. Using this technique we als...

  10. Study of ground-state configuration of neutron-rich aluminium isotopes through electromagnetic excitation

    International Nuclear Information System (INIS)

    Chakraborty, S.; Datta Pramanik, U.; Chatterjee, S.

    2013-01-01

    The region of the nuclear chart around neutron magic number, N∼20 and proton number (Z), 10≤ Z≤12 is known as the Island of Inversion. The valance neutron(s) of these nuclei, even in their ground state, are most likely occupying the upper pf orbitals which are normally lying above sd orbitals, N∼20 shell closure. Nuclei like 34,35 Al are lying at the boundary of this Island of Inversion. Little experimental information about their ground state configuration are available in literature

  11. Unambiguous assignment of the ground state of a nearly degenerate cluster

    International Nuclear Information System (INIS)

    Gutsev, G. L.; Khanna, S. N.; Jena, P.

    2000-01-01

    A synergistic approach that combines first-principles theory and electron photodetachment experiment is shown to be able to uniquely identify the ground state of a nearly degenerate cluster in the gas phase. Additionally, this approach can complement the Stern-Gerlach technique in determining the magnetic moment of small clusters unambiguously. The method, applied to a Fe 3 cluster, reveals its ground state to have a magnetic moment of 10μ B --in contrast with earlier predictions. (c) 2000 The American Physical Society

  12. Numerical analysis of Markov-perfect equilibria with multiple stable steady states : A duopoly application with innovative firms

    NARCIS (Netherlands)

    Dawid, H.; Keoula, M.Y.; Kort, Peter

    2017-01-01

    This paper presents a numerical method for the characterization of Markov-perfect equilibria of symmetric differential games exhibiting coexisting stable steady states. The method relying on the calculation of ‘local value functions’ through collocation in overlapping parts of the state space, is

  13. Ulva biomass as a co-substrate for stable anaerobic digestion of spent coffee grounds in continuous mode.

    Science.gov (United States)

    Kim, Jaai; Kim, Hakchan; Lee, Changsoo

    2017-10-01

    Ulva biomass was evaluated as a co-substrate for anaerobic digestion of spent coffee grounds at varying organic loads (0.7-1.6g chemical oxygen demand (COD)/Ld) and substrate compositions. Co-digestion with Ulva (25%, COD basis) proved beneficial for SCG biomethanation in both terms of process performance and stability. The beneficial effect is much more pronounced at higher organic and hydraulic loads, with the highest COD removal and methane yield being 51.8% and 0.19L/g COD fed, respectively. The reactor microbial community structure changed dynamically during the experiment, and a dominance shift from hydrogenotrophic to aceticlastic methanogens occurred with increase in organic loading rate. Network analysis provides a comprehensive view of the microbial interactions involved in the system and confirms a direct positive correlation between Ulva input and methane productivity. A group of populations, including Methanobacterium- and Methanoculleus-related methanogens, was identified as a possible indicator for monitoring the biomethanation performance. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. A Rigorous Investigation on the Ground State of the Penson-Kolb Model

    Science.gov (United States)

    Yang, Kai-Hua; Tian, Guang-Shan; Han, Ru-Qi

    2003-05-01

    By using either numerical calculations or analytical methods, such as the bosonization technique, the ground state of the Penson-Kolb model has been previously studied by several groups. Some physicists argued that, as far as the existence of superconductivity in this model is concerned, it is canonically equivalent to the negative-U Hubbard model. However, others did not agree. In the present paper, we shall investigate this model by an independent and rigorous approach. We show that the ground state of the Penson-Kolb model is nondegenerate and has a nonvanishing overlap with the ground state of the negative-U Hubbard model. Furthermore, we also show that the ground states of both the models have the same good quantum numbers and may have superconducting long-range order at the same momentum q = 0. Our results support the equivalence between these models. The project partially supported by the Special Funds for Major State Basic Research Projects (G20000365) and National Natural Science Foundation of China under Grant No. 10174002

  15. A projection gradient method for computing ground state of spin-2 Bose–Einstein condensates

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hanquan, E-mail: hanquan.wang@gmail.com [School of Statistics and Mathematics, Yunnan University of Finance and Economics, Kunming, Yunnan Province, 650221 (China); Yunnan Tongchang Scientific Computing and Data Mining Research Center, Kunming, Yunnan Province, 650221 (China)

    2014-10-01

    In this paper, a projection gradient method is presented for computing ground state of spin-2 Bose–Einstein condensates (BEC). We first propose the general projection gradient method for solving energy functional minimization problem under multiple constraints, in which the energy functional takes real functions as independent variables. We next extend the method to solve a similar problem, where the energy functional now takes complex functions as independent variables. We finally employ the method into finding the ground state of spin-2 BEC. The key of our method is: by constructing continuous gradient flows (CGFs), the ground state of spin-2 BEC can be computed as the steady state solution of such CGFs. We discretized the CGFs by a conservative finite difference method along with a proper way to deal with the nonlinear terms. We show that the numerical discretization is normalization and magnetization conservative and energy diminishing. Numerical results of the ground state and their energy of spin-2 BEC are reported to demonstrate the effectiveness of the numerical method.

  16. Reactive ground-state pathways are not ubiquitous in red/green cyanobacteriochromes.

    Science.gov (United States)

    Chang, Che-Wei; Gottlieb, Sean M; Kim, Peter W; Rockwell, Nathan C; Lagarias, J Clark; Larsen, Delmar S

    2013-09-26

    Recent characterization of the red/green cyanobacteriochrome (CBCR) NpR6012g4 revealed a high quantum yield for its forward photoreaction [J. Am. Chem. Soc. 2012, 134, 130-133] that was ascribed to the activity of hidden, productive ground-state intermediates. The dynamics of the pathways involving these ground-state intermediates was resolved with femtosecond dispersed pump-dump-probe spectroscopy, the first such study reported for any CBCR. To address the ubiquity of such second-chance initiation dynamics (SCID) in CBCRs, we examined the closely related red/green CBCR NpF2164g6 from Nostoc punctiforme. Both NpF2164g6 and NpR6012g4 use phycocyanobilin as the chromophore precursor and exhibit similar excited-state dynamics. However, NpF2164g6 exhibits a lower quantum yield of 32% for the generation of the isomerized Lumi-R primary photoproduct, compared to 40% for NpR6012g4. This difference arises from significantly different ground-state dynamics between the two proteins, with the SCID mechanism deactivated in NpF2164g6. We present an integrated inhomogeneous target model that self-consistently fits the pump-probe and pump-dump-probe signals for both forward and reverse photoreactions in both proteins. This work demonstrates that reactive ground-state intermediates are not ubiquitous phenomena in CBCRs.

  17. A projection gradient method for computing ground state of spin-2 Bose–Einstein condensates

    International Nuclear Information System (INIS)

    Wang, Hanquan

    2014-01-01

    In this paper, a projection gradient method is presented for computing ground state of spin-2 Bose–Einstein condensates (BEC). We first propose the general projection gradient method for solving energy functional minimization problem under multiple constraints, in which the energy functional takes real functions as independent variables. We next extend the method to solve a similar problem, where the energy functional now takes complex functions as independent variables. We finally employ the method into finding the ground state of spin-2 BEC. The key of our method is: by constructing continuous gradient flows (CGFs), the ground state of spin-2 BEC can be computed as the steady state solution of such CGFs. We discretized the CGFs by a conservative finite difference method along with a proper way to deal with the nonlinear terms. We show that the numerical discretization is normalization and magnetization conservative and energy diminishing. Numerical results of the ground state and their energy of spin-2 BEC are reported to demonstrate the effectiveness of the numerical method

  18. Liquid structure as a guide for phase stability in the solid state: Discovery of a stable compound in the Au-Si alloy system

    International Nuclear Information System (INIS)

    Tasci, Emre S.; Sluiter, Marcel H.F.; Pasturel, Alain; Villars, Pierre

    2010-01-01

    A new crystalline ground state was discovered in the Au-Si system through first-principles electronic structure calculations. The new structure was found using the experimentally and theoretically determined local atomic structure in the liquid as a guide for the solid state. Local atomic structure in the liquid was matched with that for all known crystal structures as compiled in the Pauling File structural database. The best matching crystalline structures were then explicitly calculated using first-principles methods. Most candidate crystal structures were found to be close, but above the enthalpy of a composition weighted average of the face-centered cubic Au and diamond structure Si terminal phases, but one crystal structure was more stable than the terminal phases by about 10 meV atom -1 at T = 0 K. As first-principles simulations of local structure are feasible for most liquid alloys, the present methodology is applicable to other alloys lying near a eutectic composition.

  19. Energies of the ground state and first excited 0 sup + state in an exactly solvable pairing model

    CERN Document Server

    Dinh Dang, N

    2003-01-01

    Several approximations are tested by calculating the ground-state energy and the energy of the first excited 0 sup + state using an exactly solvable model with two symmetric levels interacting via a pairing force. They are the BCS approximation (BCS), Lipkin-Nogami (LN) method, random-phase approximation (RPA), quasiparticle RPA (QRPA), the renormalized RPA (RRPA), and renormalized QRPA (RQRPA). It is shown that, in the strong-coupling regime, the QRPA which neglects the scattering term of the model Hamiltonian offers the best fit to the exact solutions. A recipe is proposed using the RRPA and RQRPA in combination with the pairing gap given by the LN method. Applying this recipe, it is shown that the superfluid-normal phase transition is avoided, and a reasonably good description for both of the ground-state energy and the energy of the first excited 0 sup + state is achieved. (orig.)

  20. Rayleigh approximation to ground state of the Bose and Coulomb glasses

    Science.gov (United States)

    Ryan, S. D.; Mityushev, V.; Vinokur, V. M.; Berlyand, L.

    2015-01-01

    Glasses are rigid systems in which competing interactions prevent simultaneous minimization of local energies. This leads to frustration and highly degenerate ground states the nature and properties of which are still far from being thoroughly understood. We report an analytical approach based on the method of functional equations that allows us to construct the Rayleigh approximation to the ground state of a two-dimensional (2D) random Coulomb system with logarithmic interactions. We realize a model for 2D Coulomb glass as a cylindrical type II superconductor containing randomly located columnar defects (CD) which trap superconducting vortices induced by applied magnetic field. Our findings break ground for analytical studies of glassy systems, marking an important step towards understanding their properties. PMID:25592417

  1. Multiple stable states of a periodically driven electron spin in a quantum dot using circularly polarized light

    Science.gov (United States)

    Korenev, V. L.

    2011-06-01

    The periodical modulation of circularly polarized light with a frequency close to the electron spin resonance frequency induces a sharp change of the single electron spin orientation. Hyperfine interaction provides a feedback, thus fixing the precession frequency of the electron spin in the external and the Overhauser field near the modulation frequency. The nuclear polarization is bidirectional and the electron-nuclear spin system (ENSS) possesses a few stable states. The same physics underlie the frequency-locking effect for two-color and mode-locked excitations. However, the pulsed excitation with mode-locked laser brings about the multitudes of stable states in ENSS in a quantum dot. The resulting precession frequencies of the electron spin differ in these states by the multiple of the modulation frequency. Under such conditions ENSS represents a digital frequency converter with more than 100 stable channels.

  2. Electron-impact excitation and ionization cross sections for ground state and excited helium atoms

    International Nuclear Information System (INIS)

    Ralchenko, Yu.; Janev, R.K.; Kato, T.; Fursa, D.V.; Bray, I.; Heer, F.J. de

    2008-01-01

    Comprehensive and critically assessed cross sections for the electron-impact excitation and ionization of ground state and excited helium atoms are presented. All states (atomic terms) with n≤4 are treated individually, while the states with n≥5 are considered degenerate. For the processes involving transitions to and from n≥5 levels, suitable cross section scaling relations are presented. For a large number of transitions, from both ground and excited states, convergent close coupling calculations were performed to achieve a high accuracy of the data. The evaluated/recommended cross section data are presented by analytic fit functions, which preserve the correct asymptotic behavior of the cross sections. The cross sections are also displayed in graphical form

  3. Determination of many-electron basis functions for a quantum Hall ground state using Schur polynomials

    Science.gov (United States)

    Mandal, Sudhansu S.; Mukherjee, Sutirtha; Ray, Koushik

    2018-03-01

    A method for determining the ground state of a planar interacting many-electron system in a magnetic field perpendicular to the plane is described. The ground state wave-function is expressed as a linear combination of a set of basis functions. Given only the flux and the number of electrons describing an incompressible state, we use the combinatorics of partitioning the flux among the electrons to derive the basis wave-functions as linear combinations of Schur polynomials. The procedure ensures that the basis wave-functions form representations of the angular momentum algebra. We exemplify the method by deriving the basis functions for the 5/2 quantum Hall state with a few particles. We find that one of the basis functions is precisely the Moore-Read Pfaffian wave function.

  4. Cluster expansion of the wavefunction. Calculation of electron correlations in ground and excited states by SAC and SAC CI theories

    International Nuclear Information System (INIS)

    Nakatsuji, H.

    1979-01-01

    The SAC and SAC CI theories are formulated for actual calculations of singlet ground states and their excited states of arbitrary spin multiplicity. Approximations are considered for the variational methods since time-consuming terms are involved. The results of test calculations for singlet states have shown, with much smaller numbers of variables (sizes of the matrices involved), excellent agreement with the full CI and close-to-full CI results. This shows the utility of the SAC theory for ground states and especially of the SAC CI theory for excited states, since the slow convergence of the CI theory is much more critical for excited states than for ground states. (Auth.)

  5. Ground state properties of exotic nuclei in deformed medium mass region

    International Nuclear Information System (INIS)

    Manju; Chatterjee, R.; Singh, Jagjit; Shubhchintak

    2017-01-01

    The dipole moment, size of the nucleus and other ground state properties of deformed nuclei 37 Mg and 31 Ne are presented. Furthermore with this deformed wave function the electric dipole strength distribution for deformed nuclei 37 Mg and 31 Ne is calculated. This will allow us to investigate the two dimensional scaling phenomenon with two parameters: quadrupole deformation and separation energy

  6. Some fundamental properties of the ground state of atoms and molecules

    International Nuclear Information System (INIS)

    Lieb, E.H.

    1986-01-01

    This paper studies the ground states of atoms and molecules in quantum mechanics and reports on some mathematically rigourous results pertaining to the matter. The non-relativistic Hamiltonian for a molecule in the static nucleus approximation is presented along with notations

  7. Search for 12 C+ 12 C clustering in 24 Mg ground state

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 88; Issue 2. Search for 12C+12C clustering in 24Mg ground state. B N JOSHI ARUN K JAIN D C BISWAS B V JOHN Y K GUPTA L S DANU R P VIND G K PRAJAPATI S MUKHOPADHYAY A SAXENA. Regular Volume 88 Issue 2 February 2017 Article ID 29 ...

  8. Lower bounds for the ground states of He-isoelectronic series

    International Nuclear Information System (INIS)

    Fraga, Serafin

    1981-01-01

    A formulation, based on the concept of null local kinetic energy regions, has been developed for the determination of lower bounds for the ground state of a two-electron atom. Numerical results, obtained from Hartree-Fock functions, are presented for the elements He through Kr of the two-electron series

  9. Ground states and formal duality relations in the Gaussian core model

    NARCIS (Netherlands)

    Cohn, H.; Kumar, A.; Schürmann, A.

    2009-01-01

    We study dimensional trends in ground states for soft-matter systems. Specifically, using a high-dimensional version of Parrinello-Rahman dynamics, we investigate the behavior of the Gaussian core model in up to eight dimensions. The results include unexpected geometric structures, with surprising

  10. Experimental Insights into Ground-State Selection of Quantum XY Pyrochlores

    Science.gov (United States)

    Hallas, Alannah M.; Gaudet, Jonathan; Gaulin, Bruce D.

    2018-03-01

    Extensive experimental investigations of the magnetic structures and excitations in the XY pyrochlores have been carried out over the past decade. Three families of XY pyrochlores have emerged: Yb2B2O7, Er2B2O7, and, most recently, [Formula: see text]Co2F7. In each case, the magnetic cation (either Yb, Er, or Co) exhibits XY anisotropy within the local pyrochlore coordinates, a consequence of crystal field effects. Materials in these families display rich phase behavior and are candidates for exotic ground states, such as quantum spin ice, and exotic ground-state selection via order-by-disorder mechanisms. In this review, we present an experimental summary of the ground-state properties of the XY pyrochlores, including evidence that they are strongly influenced by phase competition. We empirically demonstrate the signatures for phase competition in a frustrated magnet: multiple heat capacity anomalies, suppressed TN or TC, sample- and pressure-dependent ground states, and unconventional spin dynamics.

  11. On the topological ground state of E-infinity spacetime and the super string connection

    International Nuclear Information System (INIS)

    El Naschie, M.S.

    2007-01-01

    There are at present a huge number of valid super string ground states, making the one corresponding to our own universe extremely hard to determine. Therefore it may come as quite a surprise that it is a rather simple undertaking to determine the exact topological ground state of E-infinity Cantorian spacetime theory. Similar to the ground state of the Higgs for E-infinity, the expectation value of the topological ground state is non-zero and negative. Its value is given exactly by -bar o -∼ n(1/φ) n =-(4+φ 3 ) where φ=(5-1)/2 and n represents an integer Menger-Uhryson dimension running from n=0 to n=-∼. Recalling that the average dimension of ε (∼) is given by ∼ =4+φ 3 , one could interpret this result as saying that our E-infinity spacetime may be viewed as an in itself closed manifold given by the remarkable equation: + =zeroThus in a manner of speaking, the universe could have spontaneously tunnelled into existence from virtual nothingness

  12. Search for 12 C+ 12 C clustering in 24 Mg ground state

    Indian Academy of Sciences (India)

    In the backdrop of many models, the heavy cluster structure of the ground state of 24 Mg has been probed experimentally for the first time using the heavy cluster knockout reaction 24 Mg( 12 C, 212 C) 12 C in thequasifree scattering kinematic domain. In the ( 12 C, 212 C) reaction, the direct 12 C-knockout cross-section was ...

  13. Ground state properties of the bond alternating spin-1/2 anisotropic Heisenberg chain

    Directory of Open Access Journals (Sweden)

    S. Paul

    2017-06-01

    Full Text Available Ground state properties, dispersion relations and scaling behaviour of spin gap of a bond alternating spin-1/2 anisotropic Heisenberg chain have been studied where the exchange interactions on alternate bonds are ferromagnetic (FM and antiferromagnetic (AFM in two separate cases. The resulting models separately represent nearest neighbour (NN AFM-AFM and AFM-FM bond alternating chains. Ground state energy has been estimated analytically by using both bond operator and Jordan-Wigner representations and numerically by using exact diagonalization. Dispersion relations, spin gap and several ground state orders have been obtained. Dimer order and string orders are found to coexist in the ground state. Spin gap is found to develop as soon as the non-uniformity in alternating bond strength is introduced in the AFM-AFM chain which further remains non-zero for the AFM-FM chain. This spin gap along with the string orders attribute to the Haldane phase. The Haldane phase is found to exist in most of the anisotropic region similar to the isotropic point.

  14. Relativistic analysis of nuclear ground state densities at 135 to 200 ...

    Indian Academy of Sciences (India)

    fitting of differential cross-section and analyzing power, and the appearance of wine-bottle- ... So, the effect of different nuclear density distributions is quite conspicuous in the relativistic ap- proach. Hence, we have analyzed five different nuclear ground state .... The NEG and FNEG densities have been used to see the effect.

  15. Magnetostriction-driven ground-state stabilization in 2H perovskites

    International Nuclear Information System (INIS)

    Porter, D. G.; Senn, M. S.; University of Oxford; Khalyavin, D. D.; Cortese, A.

    2016-01-01

    In this paper, the magnetic ground state of Sr_3ARuO_6, with A =(Li,Na), is studied using neutron diffraction, resonant x-ray scattering, and laboratory characterization measurements of high-quality crystals. Combining these results allows us to observe the onset of long-range magnetic order and distinguish the symmetrically allowed magnetic models, identifying in-plane antiferromagnetic moments and a small ferromagnetic component along the c axis. While the existence of magnetic domains masks the particular in-plane direction of the moments, it has been possible to elucidate the ground state using symmetry considerations. We find that due to the lack of local anisotropy, antisymmetric exchange interactions control the magnetic order, first through structural distortions that couple to in-plane antiferromagnetic moments and second through a high-order magnetoelastic coupling that lifts the degeneracy of the in-plane moments. Finally, the symmetry considerations used to rationalize the magnetic ground state are very general and will apply to many systems in this family, such as Ca_3ARuO_6, with A = (Li,Na), and Ca_3LiOsO_6 whose magnetic ground states are still not completely understood.

  16. Patterns of the ground states in the presence of random interactions : Nucleon systems

    NARCIS (Netherlands)

    Zhao, YM; Arima, A; Shimizu, N; Ogawa, K; Yoshinaga, N; Scholten, O

    We present our results on properties of ground states for nucleonic systems in the presence of random two-body interactions. In particular, we calculate probability distributions for parity, seniority, spectroscopic (i.e., in the laboratory frame) quadrupole moments, and discuss a clustering in the

  17. Quantum double-well chain: Ground-state phases and applications to hydrogen-bonded materials

    International Nuclear Information System (INIS)

    Wang, X.; Campbell, D.K.; Gubernatis, J.E.

    1994-01-01

    Extrapolating the results of hybrid quantum Monte Carlo simulations to the zero temperature and infinite-chain-length limits, we calculate the ground-state phase diagram of a system of quantum particles on a chain of harmonically coupled, symmetric, quartic double-well potentials. We show that the ground state of this quantum chain depends on two parameters, formed from the ratios of the three natural energy scales in the problem. As a function of these two parameters, the quantum ground state can exhibit either broken symmetry, in which the expectation values of the particle's coordinate are all nonzero (as would be the case for a classical chain), or restored symmetry, in which the expectation values of the particle's coordinate are all zero (as would be the case for a single quantum particle). In addition to the phase diagram as a function of these two parameters, we calculate the ground-state energy, an order parameter related to the average position of the particle, and the susceptibility associated with this order parameter. Further, we present an approximate analytic estimate of the phase diagram and discuss possible physical applications of our results, emphasizing the behavior of hydrogen halides under pressure

  18. Ground state structures and properties of Si3Hn (n= 1–6) clusters

    Indian Academy of Sciences (India)

    The ground state structures and properties of Si3H (1 ≤ ≤ 6) clusters have been calculated using Car–Parrinello molecular dynamics with simulated annealing and steepest descent optimization methods. We have studied cohesive energy per particle and first excited electronic level gap of the clusters as a function of ...

  19. Long-range interactions of excited He atoms with ground-state noble-gas atoms

    KAUST Repository

    Zhang, J.-Y.; Qian, Ying; Schwingenschlö gl, Udo; Yan, Z.-C.

    2013-01-01

    The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition

  20. A nonlinear programming approach to lower bounds for the ground-state energy of helium

    International Nuclear Information System (INIS)

    Porras, I.; Feldmann, D.M.; King, F.W.

    1999-01-01

    Lower-bound estimates for the ground-state energy of the helium atom are determined using nonlinear programming techniques. Optimized lower bounds are determined for single-particle, radially correlated, and general correlated wave functions. The local nature of the method employed makes it a very severe test of the accuracy of the wave function

  1. Rabi Oscillations between Ground and Rydberg States with Dipole-Dipole Atomic Interactions

    International Nuclear Information System (INIS)

    Johnson, T. A.; Urban, E.; Henage, T.; Isenhower, L.; Yavuz, D. D.; Walker, T. G.; Saffman, M.

    2008-01-01

    We demonstrate Rabi oscillations of small numbers of 87 Rb atoms between ground and Rydberg states with n≤43. Coherent population oscillations are observed for single atoms, while the presence of two or more atoms decoheres the oscillations. We show that these observations are consistent with van der Waals interactions of Rydberg atoms

  2. Ground-state energy of an exciton-(LO) phonon system in a parabolic quantum well

    Science.gov (United States)

    Gerlach, B.; Wüsthoff, J.; Smondyrev, M. A.

    1999-12-01

    This paper presents a variational study of the ground-state energy of an exciton-(LO) phonon system, which is spatially confined to a quantum well. The exciton-phonon interaction is of Fröhlich type, the confinement potentials are assumed to be parabolic functions of the coordinates. Making use of functional integral techniques, the phonon part of the problem can be eliminated exactly, leading us to an effective two-particle system, which has the same spectral properties as the original one. Subsequently, Jensen's inequality is applied to obtain an upper bound on the ground-state energy. The main intention of this paper is to analyze the influence of the quantum-well-induced localization of the exciton on its ground-state energy (or its binding energy, respectively). To do so, we neglect any mismatch of the masses or the dielectric constants, but admit an arbitrary strength of the confinement potentials. Our approach allows for a smooth interpolation of the ultimate limits of vanishing and infinite confinement, corresponding to the cases of a free three-dimensional and a free two-dimensional exciton-phonon system. The interpolation formula for the ground-state energy bound corresponds to similar formulas for the free polaron or the free exciton-phonon system. These bounds in turn are known to compare favorably with all previous ones, which we are aware of.

  3. The magnetic structure on the ground state of the equilateral triangular spin tube

    International Nuclear Information System (INIS)

    Matsui, Kazuki; Goto, Takayuki; Manaka, Hirotaka; Miura, Yoko

    2016-01-01

    The ground state of the frustrated equilateral triangular spin tube CsCrF_4 is still hidden behind a veil though NMR spectrum broaden into 2 T at low temperature. In order to investigate the spin structure in an ordered state by "1"9F-NMR, we have determined the anisotropic hyperfine coupling tensors for each three fluorine sites in the paramagnetic state. The measurement field was raised up to 10 T to achieve highest resolution. The preliminary analysis using the obtained hyperfine tensors has shown that the archetypal 120°-type structure in ab-plane does not accord with the NMR spectra of ordered state.

  4. Global optimization of proteins using a dynamical lattice model: Ground states and energy landscapes

    OpenAIRE

    Dressel, F.; Kobe, S.

    2004-01-01

    A simple approach is proposed to investigate the protein structure. Using a low complexity model, a simple pairwise interaction and the concept of global optimization, we are able to calculate ground states of proteins, which are in agreement with experimental data. All possible model structures of small proteins are available below a certain energy threshold. The exact lowenergy landscapes for the trp cage protein (1L2Y) is presented showing the connectivity of all states and energy barriers.

  5. Relationship between atomically related core levels and ground state properties of solids: first-principles calculations

    Czech Academy of Sciences Publication Activity Database

    Vackář, Jiří; Šipr, Ondřej; Šimůnek, Antonín

    2008-01-01

    Roč. 77, č. 4 (2008), 045112/1-045112/6 ISSN 1098-0121 R&D Projects: GA AV ČR IAA100100514; GA AV ČR(CZ) IAA100100637 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z10100521 Keywords : core levels * ab-initio calculations * electronic states * ground state properties Subject RIV: BE - Theoretical Physics Impact factor: 3.322, year: 2008

  6. Present state and problems of the measures for securing stable supply of uranium resources

    International Nuclear Information System (INIS)

    Yoneda, Fumishige

    1982-01-01

    The long-term stable supply of uranium resources must be secured in order to accelerate the development and utilization of nuclear power in Japan. All uranium required in Japan is imported from foreign countries, and depends on small number of suppliers. On the use of uranium, various restrictions have been imposed by bilateral agreements from the viewpoint of nuclear non-proliferation policy. At present, the demand-supply relation in uranium market is not stringent, but in the latter half of 1980s, it is feared that it will be stringent. The prospect of the demand and supply of uranium resources, the state of securing uranium resources, the present policy on uranium resources, the necessity of establishing the new policy, and the active promotion of uranium resource measures are described. The measures to be taken are the promotion of exploration and development of mines, the participation in the management of such foreign projects, the promotion of diversifying the supply sources, the establishment of the structure to accept uranium resources, the promotion of the storage of uranium, and the rearrangement of general coordination and promotion functions for uranium resource procurement. (Kako, I.)

  7. Alternative stable states generated by ontogenetic niche shift in the presence of multiple resource use.

    Directory of Open Access Journals (Sweden)

    Takefumi Nakazawa

    2011-02-01

    Full Text Available It has been suggested that when juveniles and adults use different resources or habitats, alternative stable states (ASS may exist in systems coupled by an ontogenetic niche shift. However, mainly the simplest system, i.e., the one-consumer-two-resource system, has been studied previously, and little is known about the development of ASS existing in more complex systems. Here, I theoretically investigated the development of ASS caused by an ontogenetic niche shift in the presence of multiple resource use. I considered three independent scenarios; (i additional resources, (ii multiple habitats, and (iii interstage resource sharing. The model analyses illustrate that relative balance between the total resource availability in the juvenile and adult habitats is crucial for the development of ASS. This balance is determined by factors such as local habitat productivity, subsidy inputs, colonization area, and foraging mobility. Furthermore, it is also shown that interstage resource sharing generally suppresses ASS. These results suggest that the anthropogenic impacts of habitat modifications (e.g., fragmentation and destruction or interaction modifications (e.g., changes in ontogeny and foraging behavior propagate through space and may cause or prevent regime shifts in the regional community structure.

  8. Steady-state pharmacokinetics of sirolimus in stable adult Chinese renal transplant patients.

    Science.gov (United States)

    Wang, Huifen Faye; Qiu, Feng; Wu, Xiongfe; Fang, Juanzhi; Crownover, Penelope; Korth-Bradley, Joan; Schulman, Seth

    2014-05-01

    This open-label, nonrandomized study was conducted to evaluate the steady-state pharmacokinetics of sirolimus in 24 stable Chinese renal transplant patients receiving daily oral maintenance doses of sirolimus (1-4 mg). Repeated trough and serial whole blood sirolimus concentrations over a 24-hour dosing interval were collected and assayed using high-performance liquid chromatography with tandem mass spectrometry (HPLC/MS/MS). Non-compartmental analysis (NCA) was employed to calculate sirolimus pharmacokinetic parameters. Cytochrome P450 (CYP) 3A5 genotyping was performed. Cyclosporine (CsA) levels were determined for patients who took concomitant CsA. Mean (±SD) sirolimus maximum concentration (Cmax ), area under the concentration-time curve within a dosing interval of τ (AUCτ ), oral clearance (CL/F), and trough concentration (Ctrough ) at steady state were: 14.1 ± 13.4 ng/mL, 199 ± 210 ng · h/mL, 10.1 ± 4.4 L/h, and 5.9 ± 6.3 ng/mL, respectively. Median tmax (range) was 2.49 hours (1-12 hours). A strong correlation was observed between Ctrough and AUCτ . Pharmacokinetics of sirolimus in patients with and without concomitant CsA were comparable. Allele frequency of CYP3A5*3 was 70.9% and a trend of higher oral clearance was observed in CYP3A5 expressers compared with non-expressers although the number of subjects in each genotype was small. © 2014, The American College of Clinical Pharmacology.

  9. Ground-state kinetics of bistable redox-active donor-acceptor mechanically interlocked molecules.

    Science.gov (United States)

    Fahrenbach, Albert C; Bruns, Carson J; Li, Hao; Trabolsi, Ali; Coskun, Ali; Stoddart, J Fraser

    2014-02-18

    The ability to design and confer control over the kinetics of theprocesses involved in the mechanisms of artificial molecular machines is at the heart of the challenge to create ones that can carry out useful work on their environment, just as Nature is wont to do. As one of the more promising forerunners of prototypical artificial molecular machines, chemists have developed bistable redox-active donor-acceptor mechanically interlocked molecules (MIMs) over the past couple of decades. These bistable MIMs generally come in the form of [2]rotaxanes, molecular compounds that constitute a ring mechanically interlocked around a dumbbell-shaped component, or [2]catenanes, which are composed of two mechanically interlocked rings. As a result of their interlocked nature, bistable MIMs possess the inherent propensity to express controllable intramolecular, large-amplitude, and reversible motions in response to redox stimuli. In this Account, we rationalize the kinetic behavior in the ground state for a large assortment of these types of bistable MIMs, including both rotaxanes and catenanes. These structures have proven useful in a variety of applications ranging from drug delivery to molecular electronic devices. These bistable donor-acceptor MIMs can switch between two different isomeric states. The favored isomer, known as the ground-state co-conformation (GSCC) is in equilibrium with the less favored metastable state co-conformation (MSCC). The forward (kf) and backward (kb) rate constants associated with this ground-state equilibrium are intimately connected to each other through the ground-state distribution constant, KGS. Knowing the rate constants that govern the kinetics and bring about the equilibration between the MSCC and GSCC, allows researchers to understand the operation of these bistable MIMs in a device setting and apply them toward the construction of artificial molecular machines. The three biggest influences on the ground-state rate constants arise from

  10. Ground state shape and crossing of near spherical and deformed bands in 182Hg

    International Nuclear Information System (INIS)

    Ma, W.C.; Ramayya, A.V.; Hamilton, J.H.; Robinson, S.J.; Barclay, M.E.; Zhao, K.; Cole, J.D.; Zganjar, E.F.; Spejewski, E.H.

    1983-01-01

    The energy levels of 182 Hg have been identified for the first time through comparison of in-beam studies of the reactions 156 154 Gd( 32 S,4n) 184 182 Hg. Levels up to 12 + in 182 Hg were established from γ-γ coincidence and singles measurement. The data establish that the ground state shape is near spherical, and that the ground band is crossed by a well deformed band at 4 + . In contrast to IBA model predictions that the deformed band will rise in energy in 182 Hg compared to 184 Hg, the energies of the deformed levels in 182 Hg continue to drop. 7 references

  11. Radon concentrations in ground and drinking water in the state of Chihuahua, Mexico

    International Nuclear Information System (INIS)

    Villalba, L.; Colmenero Sujo, L.; Montero Cabrera, M.E.; Cano Jimenez, A.; Renteria Villalobos, M.; Delgado Mendoza, C.J.; Jurado Tenorio, L.A.; Davila Rangel, I.; Herrera Peraza, E.F.

    2005-01-01

    This paper reports 222 Rn concentrations in ground and drinking water of nine cities of Chihuahua State, Mexico. Fifty percent of the 114 sampled wells exhibited 222 Rn concentrations exceeding 11 Bq/L, the maximum contaminant level (MCL) recommended by the USEPA. Furthermore, around 48% (123 samples) of the tap-water samples taken from 255 dwellings showed radon concentrations over the MCL. There is an apparent correlation between total dissolved solids and radon concentration in ground-water. The high levels of 222 Rn found may be entirely attributed to the nature of aquifer rocks

  12. Radon concentrations in ground and drinking water in the state of Chihuahua, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Villalba, L. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico); Colmenero Sujo, L. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico); Instituto Tecnologico de Chihuahua II, Ave. de las Industrias 11101, Chihuahua, Chih. (Mexico); Montero Cabrera, M.E. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico)]. E-mail: elena.montero@cimav.edu.mx; Cano Jimenez, A. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico); Renteria Villalobos, M. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico); Delgado Mendoza, C.J. [Facultad de Ciencias Quimicas, Universidad Autonoma de Chihuahua, Ciudad Universitaria S/N, Chihuahua, Chih. (Mexico); Jurado Tenorio, L.A. [Facultad de Ciencias Quimicas, Universidad Autonoma de Chihuahua, Ciudad Universitaria S/N, Chihuahua, Chih. (Mexico); Davila Rangel, I. [Centro Regional de Estudios Nucleares, Universidad Autonoma de Zacatecas, Cipres 20, Zacatecas, Zac. (Mexico); Herrera Peraza, E.F. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico)

    2005-07-01

    This paper reports {sup 222}Rn concentrations in ground and drinking water of nine cities of Chihuahua State, Mexico. Fifty percent of the 114 sampled wells exhibited {sup 222}Rn concentrations exceeding 11 Bq/L, the maximum contaminant level (MCL) recommended by the USEPA. Furthermore, around 48% (123 samples) of the tap-water samples taken from 255 dwellings showed radon concentrations over the MCL. There is an apparent correlation between total dissolved solids and radon concentration in ground-water. The high levels of {sup 222}Rn found may be entirely attributed to the nature of aquifer rocks.

  13. Radon concentrations in ground and drinking water in the state of Chihuahua, Mexico.

    Science.gov (United States)

    Villalba, L; Colmenero Sujo, L; Montero Cabrera, M E; Cano Jiménez, A; Rentería Villalobos, M; Delgado Mendoza, C J; Jurado Tenorio, L A; Dávila Rangel, I; Herrera Peraza, E F

    2005-01-01

    This paper reports (222)Rn concentrations in ground and drinking water of nine cities of Chihuahua State, Mexico. Fifty percent of the 114 sampled wells exhibited (222)Rn concentrations exceeding 11Bq/L, the maximum contaminant level (MCL) recommended by the USEPA. Furthermore, around 48% (123 samples) of the tap-water samples taken from 255 dwellings showed radon concentrations over the MCL. There is an apparent correlation between total dissolved solids and radon concentration in ground-water. The high levels of (222)Rn found may be entirely attributed to the nature of aquifer rocks.

  14. Thermal and electrodynamical formation mechanisms of overloaded AC states and charging rate influence on their stable dynamics

    International Nuclear Information System (INIS)

    Romanovskii, V.; Watanabe, K.; Awaji, S.

    2013-01-01

    Highlights: •Overloaded AC states are investigated to understand the mechanisms of there formation. •There exist characteristic time windows defining the existence of stable overloaded AC states. •Limiting values of the electric field, current and temperature are higher than the quench ones. -- Abstract: The macroscopic thermal and electrodynamical phenomena occurring in high-T c superconductors during overloaded AC states are theoretically investigated to understand the basic physical mechanisms, which are characteristic for the stable formation of the operating modes when the peak current exceeds the critical current of a superconductor during AC modes. It is shown that there exist characteristic time windows defining the existence of stable overloaded AC states. They identify the stability boundary of the overloaded AC states. Therefore, there is the maximum allowable value of a peak current of stable overloaded AC regimes at the given charging rate, cooling conditions and properties of a superconductor and a matrix. The results obtained prove that the limiting peak current is higher than the corresponding quench current defining the stability margin of DC states. It monotonically increases with the charging rate. Besides, in the stable overloaded AC states, the peak values of the electric field and temperature may be also noticeably higher than the corresponding quench values. They depend on the peak current and charging rate at the given cooling conditions. As a result, high-T c superconducting tapes can stably work under intensive AC modes without instability onset when the peak of applied currents may significantly exceed not only the critical current but also the corresponding values of DC-quench currents

  15. Theory of Nonlinear Dispersive Waves and Selection of the Ground State

    International Nuclear Information System (INIS)

    Soffer, A.; Weinstein, M.I.

    2005-01-01

    A theory of time-dependent nonlinear dispersive equations of the Schroedinger or Gross-Pitaevskii and Hartree type is developed. The short, intermediate and large time behavior is found, by deriving nonlinear master equations (NLME), governing the evolution of the mode powers, and by a novel multitime scale analysis of these equations. The scattering theory is developed and coherent resonance phenomena and associated lifetimes are derived. Applications include Bose-Einstein condensate large time dynamics and nonlinear optical systems. The theory reveals a nonlinear transition phenomenon, 'selection of the ground state', and NLME predicts the decay of excited state, with half its energy transferred to the ground state and half to radiation modes. Our results predict the recent experimental observations of Mandelik et al. in nonlinear optical waveguides

  16. Magnetic ground and remanent states of synthetic metamagnets with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Kiselev, N S; Roessler, U K; Bogdanov, A N; Hellwig, O

    2011-01-01

    In this work, we summarize our theoretical results within a phenomenological micromagnetic approach for magnetic ground state and nonequilibrium states as topological magnetic defects in multilayers with strong perpendicular anisotropy and antiferromagnetic (AF) interlayer exchange coupling (IEC), e.g. [Co/Pt(Pd)]/Ru(Ir, NiO). We give detailed analysis of our model together with the most representative results which elucidate common features of such systems. We discuss phase diagrams of the magnetic ground state, and compare solutions of our model with experimental data. A model to assess the stability of so-called tiger tail patterns is presented. It is found that these modulated topological defect cannot be stabilized by an interplay between magnetostatic and IEC energies only. It is argued that tiger tail patterns arise as nuclei of ferro-stripe structure in AF domain walls and that they are stabilized by domain wall pinning.

  17. The ground state energy of 3He droplet in the LOCV framework

    International Nuclear Information System (INIS)

    Modarres, M.; Motahari, S.; Rajabi, A.

    2012-01-01

    The (extended) lowest order constrained variational method was used to calculate the ground state energy of liquid helium 3 ( 3 He) droplets at zero temperature. Different types of density distribution profiles, such as the Gaussian, the Quasi-Gaussian and the Woods-Saxon were used. It was shown that at least, on average, near 20 3 He atoms are needed to get the bound state for 3 He liquid droplet. Depending on the choice of the density profiles and the atomic radius of 3 He, the above estimate can increase to 300. Our calculated ground state energy and the number of atoms in liquid 3 He droplet were compared with those of Variational Monte Carlo method, Diffusion Monte Carlo method and Density Functional Theory, for which a reasonable agreement was found.

  18. Non-Gaussian ground-state deformations near a black-hole singularity

    Science.gov (United States)

    Hofmann, Stefan; Schneider, Marc

    2017-03-01

    The singularity theorem by Hawking and Penrose qualifies Schwarzschild black holes as geodesic incomplete space-times. Albeit this is a mathematically rigorous statement, it requires an operational framework that allows us to probe the spacelike singularity via a measurement process. Any such framework necessarily has to be based on quantum theory. As a consequence, the notion of classical completeness needs to be adapted to situations where the only adequate description is in terms of quantum fields in dynamical space-times. It is shown that Schwarzschild black holes turn out to be complete when probed by self-interacting quantum fields in the ground state and in excited states. The measure for populating quantum fields on hypersurfaces in the vicinity of the black-hole singularity goes to zero towards the singularity. This statement is robust under non-Gaussian deformations of and excitations relative to the ground state. The physical relevance of different completeness concepts for black holes is discussed.

  19. 2D XXZ model ground state properties using an analytic Lanczos expansion

    International Nuclear Information System (INIS)

    Witte, N.S.; Hollenberg, L.C.L.; Weihong Zheng

    1997-01-01

    A formalism was developed for calculating arbitrary expectation values for any extensive lattice Hamiltonian system using a new analytic Lanczos expansion, or plaquette expansion, and a recently proved exact theorem for ground state energies. The ground state energy, staggered magnetisation and the excited state gap of the 2D anisotropic antiferromagnetic Heisenberg Model are then calculated using this expansion for a range of anisotropy parameters and compared to other moment based techniques, such as the t-expansion, and spin-wave theory and series expansion methods. It was found that far from the isotropic point all moment methods give essentially very similar results, but near the isotopic point the plaquette expansion is generally better than the others. 20 refs., 6 tabs

  20. Hylleraas-Configuration Interaction study of the 1S ground state of the negative Li ion.

    Science.gov (United States)

    Sims, James S

    2017-12-28

    In a previous work Sims and Hagstrom [J. Chem. Phys. 140, 224312 (2014)] reported Hylleraas-Configuration Interaction (Hy-CI) method variational calculations for the neutral atom and positive ion 1 S ground states of the beryllium isoelectronic sequence. The Li - ion, nominally the first member of this series, has a decidedly different electronic structure. This paper reports the results of a large, comparable calculation for the Li - ground state to explore how well the Hy-CI method can represent the more diffuse L shell of Li - which is representative of the Be(2sns) excited states as well. The best non-relativistic energy obtained was -7.500 776 596 hartree, indicating that 10 - 20 nh accuracy is attainable in Hy-CI and that convergence of the r 12 r 34 double cusp is fast and that this correlation type can be accurately represented within the Hy-CI model.

  1. Influence of mass-asymmetry and ground state spin on fission fragment angular distributions

    International Nuclear Information System (INIS)

    Thomas, R.G.; Biswas, D.C.; Saxena, A.; Pant, L.M.; Nayak, B.K.; Vind, R.P.; Sahu, P.K.; Sinha, Shrabani; Choudhury, R.K.

    2001-01-01

    The strong influence of the target or/and projectile ground state spin on the anomalously large anisotropies of fission fragments produced in the heavy-ion induced fission of actinide targets were reported earlier. Interestingly, all those systems studied were having a mass asymmetry greater than the Businaro-Gallone critical asymmetry and hence the presence of pre-equilibrium fission was unambiguously ruled out. The observed anisotropies were successfully explained using the ECD-K-States model. It is of interest to know the influence of the target/projectile ground state spin on systems having an entrance channel mass asymmetry less than the critical value where pre-equilibrium fission cannot be ignored. With this motivation we performed measurements of fission fragment angular distributions of the 16 O+ 235 U (spin=7/2) system

  2. Ground-state properties of K-isotopes from laser and $\\beta$-NMR spectroscopy

    CERN Multimedia

    Lievens, P; Rajabali, M M; Krieger, A R

    By combining high-resolution laser spectroscopy with $\\beta$-NMR spectroscopy on polarized K-beams we aim to establish the ground-state spins and magnetic moments of the neutron-rich $^{48,49,50,51}$K isotopes from N=29 to N=32. Spins and magnetic moments of the odd-K isotopes up to N=28 reveal an inversion of the ground-state, from the normal $\\,{I}$=3/2 ($\\pi{d}_{3/2}^{-1}$) in $^{41-45}$K$\\to\\,{I}$=1/2 ($\\pi{s}_{1/2}^{-1}$) in $^{47}$K. This inversion of the proton single particle levels is related to the strong proton $d_{3/2}$ - neutron $f_{7/2}$ interaction which lowers the energy of the $\\pi{d}_{3/2}$ single particle state when filling the $\

  3. Study of polonium isotopes ground state properties by simultaneous atomic- and nuclear-spectroscopy

    CERN Multimedia

    Koester, U H; Kalaninova, Z; Imai, N

    2007-01-01

    We propose to systematically study the ground state properties of neutron deficient $^{192-200}$Po isotopes by means of in-source laser spectroscopy using the ISOLDE laser ion source coupled with nuclear spectroscopy at the detection setup as successfully done before by this collaboration with neutron deficient lead isotopes. The study of the change in mean square charge radii along the polonium isotope chain will give an insight into shape coexistence above the mid-shell N = 104 and above the closed shell Z = 82. The hyperfine structure of the odd isotopes will also allow determination of the nuclear spin and the magnetic moment of the ground state and of any identifiable isomer state. For this study, a standard UC$_{x}$ target with the ISOLDE RILIS is required for 38 shifts.

  4. Classification of matrix-product ground states corresponding to one-dimensional chains of two-state sites of nearest neighbor interactions

    International Nuclear Information System (INIS)

    Fatollahi, Amir H.; Khorrami, Mohammad; Shariati, Ahmad; Aghamohammadi, Amir

    2011-01-01

    A complete classification is given for one-dimensional chains with nearest-neighbor interactions having two states in each site, for which a matrix product ground state exists. The Hamiltonians and their corresponding matrix product ground states are explicitly obtained.

  5. Normal ground state of dense relativistic matter in a magnetic field

    International Nuclear Information System (INIS)

    Gorbar, E. V.; Miransky, V. A.; Shovkovy, I. A.

    2011-01-01

    The properties of the ground state of relativistic matter in a magnetic field are examined within the framework of a Nambu-Jona-Lasinio model. The main emphasis of this study is the normal ground state, which is realized at sufficiently high temperatures and/or sufficiently large chemical potentials. In contrast to the vacuum state, which is characterized by the magnetic catalysis of chiral symmetry breaking, the normal state is accompanied by the dynamical generation of the chiral shift parameter Δ. In the chiral limit, the value of Δ determines a relative shift of the longitudinal momenta (along the direction of the magnetic field) in the dispersion relations of opposite chirality fermions. We argue that the chirality remains a good approximate quantum number even for massive fermions in the vicinity of the Fermi surface and, therefore, the chiral shift is expected to play an important role in many types of cold dense relativistic matter, relevant for applications in compact stars. The qualitative implications of the revealed structure of the normal ground state on the physics of protoneutron stars are discussed. A noticeable feature of the Δ parameter is that it is insensitive to temperature when T 0 , where μ 0 is the chemical potential, and increases with temperature for T>μ 0 . The latter implies that the chiral shift parameter is also generated in the regime relevant for heavy ion collisions.

  6. Experimental and theoretical dipole moments of purines in their ground and lowest excited singlet states

    Science.gov (United States)

    Aaron, Jean-Jacques; Diabou Gaye, Mame; Párkányi, Cyril; Cho, Nam Sook; Von Szentpály, László

    1987-01-01

    The ground-state dipole moments of seven biologically important purines (purine, 6-chloropurine, 6-mercaptopurine, hypoxanthine, theobromine, theophylline and caffeine) were determined at 25°C in acetic acid (all the above compounds with the exception of purine) and in ethyl acetate (purine, theophylline and caffeine). Because of its low solubility, it was not possible to measure the dipole moment of uric acid. The first excited singlet-state dipole moments were obtained on the basis of the Bakhshiev and Chamma—Viallet equations using the variation of the Stokes shift with the solvent dielectric constant-refractive index term. The theoretical dipole moments for all the purines listed above and including uric acid were calculated by combining the use of the PPP (π-LCI-SCF-MO) method for the π-contribution to the overall dipole moment with the σ-contribution obtained as a vector sum of the σbond moments and group moments. The experimental and theoretical values were compared with the data available in the literature for some of the purines under study. For several purines, the calculations were carried out for different tautomeric forms. Excited singlet-state dipole moments are smaller than the ground-state values by 0.8 to 2.2 Debye units for all purines under study with the exception of 6-chloropurine. The effects of the structure upon the ground- and excited-state dipole moments of the purines are discussed.

  7. Ground state properties of a spin chain within Heisenberg model with a single lacking spin site

    International Nuclear Information System (INIS)

    Mebrouki, M.

    2011-01-01

    The ground state and first excited state energies of an antiferromagnetic spin-1/2 chain with and without a single lacking spin site are computed using exact diagonalization method, within the Heisenberg model. In order to keep both parts of a spin chain with a lacking site connected, next nearest neighbors interactions are then introduced. Also, the Density Matrix Renormalization Group (DMRG) method is used, to investigate ground state energies of large system sizes; which permits us to inquire about the effect of large system sizes on energies. Other quantum quantities such as fidelity and correlation functions are also studied and compared in both cases. - Research highlights: → In this paper we compute ground state and first excited state energies of a spin chain with and without a lacking spin site. The next nearest neighbors are introduced with the antiferromagnetic Heisenberg spin-half. → Exact diagonalization is used for small systems, where DMRG method is used to compute energies for large systems. Other quantities like quantum fidelity and correlation are also computed. → Results are presented in figures with comments. → E 0 /N is computed in a function of N for several values of J 2 and for both systems. First excited energies are also investigated.

  8. Alternative stable states and alternative endstates of community assembly through intra- and interspecific positive and negative interactions.

    Science.gov (United States)

    Gerla, Daan J; Mooij, Wolf M

    2014-09-01

    Positive and negative interactions within and between species may occur simultaneously, with the net effect depending on population densities. For instance, at low densities plants may ameliorate stress, while competition for resources dominates at higher densities. Here, we propose a simple two-species model in which con- and heterospecifics have a positive effect on per capita growth rate at low densities, while negative interactions dominate at high densities. The model thus includes both Allee effects (intraspecific positive effects) and mutualism (interspecific positive effects), as well as intra- and interspecific competition. Using graphical methods we derive conditions for alternative stable states and species coexistence. We show that mutual non-invasibility (i.e. the inability of each species to invade a population of the other) is more likely when species have a strong positive effect on the own species or a strong negative effect on the other species. Mutual non-invasibility implies alternative stable states, however, there may also be alternative stable states at which species coexist. In the case of species symmetry (i.e. when species are indistinguishable), such alternative coexistence states require that if the positive effect exerted at low densities at the own species is stronger than on the other species, the negative effect at higher densities is also stronger on the own species than on the other species, or, vice versa, if the interspecific positive effects at low densities are stronger than the intraspecific effects, the negative effects at higher densities are also stronger between species than within species. However, the reachability of alternative stable states is restricted by the frequency and density at which species are introduced during community assembly, so that alternative stable states do not always represent alternative endstates of community assembly. Copyright © 2014 Elsevier Inc. All rights reserved.

  9. Ground-state candidate for the classical dipolar kagome Ising antiferromagnet

    Science.gov (United States)

    Chioar, I. A.; Rougemaille, N.; Canals, B.

    2016-06-01

    We have investigated the low-temperature thermodynamic properties of the classical dipolar kagome Ising antiferromagnet using Monte Carlo simulations, in the quest for the ground-state manifold. In spite of the limitations of a single-spin-flip approach, we managed to identify certain ordering patterns in the low-temperature regime and we propose a candidate for this unknown state. This configuration presents some intriguing features and is fully compatible with the extrapolations of the at-equilibrium thermodynamic behavior sampled so far, making it a very likely choice for the dipolar long-range ordered state of the classical kagome Ising antiferromagnet.

  10. Mapping Precipitation Patterns from the Stable Isotopic Composition of Surface Waters: Olympic Peninsula, Washington State

    Science.gov (United States)

    Anders, A. M.; Brandon, M. T.

    2008-12-01

    Available data indicate that large and persistent precipitation gradients are tied to topography at scales down to a few kilometers, but precipitation patterns in the majority of mountain ranges are poorly constrained at scales less than tens of kilometers. A lack of knowledge of precipitation patterns hampers efforts to understand the processes of orographic precipitation and identify the relationships between geomorphic evolution and climate. A new method for mapping precipitation using the stable isotopic composition of surface waters is tested in the Olympic Mountains of Washington State. Measured δD and δ18O of 97 samples of surface water are linearly related and nearly inseparable from the global meteoric water line. A linear orographic precipitation model extended to include in effects of isotopic fractionation via Rayleigh distillation predicts precipitation patterns and isotopic composition of surface water. Seven parameters relating to the climate and isotopic composition of source water are used. A constrained random search identifies the best-fitting parameter set. Confidence intervals for parameter values are defined and precipitation patterns are determined. Average errors for the best-fitting model are 4.8 permil in δD. The difference between the best fitting model and other models within the 95% confidence interval was less than 20%. An independent high-resolution precipitation climatology documents precipitation gradients similar in shape and magnitude to the model derived from surface water isotopic composition. This technique could be extended to other mountain ranges, providing an economical and fast assessment of precipitation patterns requiring minimal field work.

  11. Water uptake in woody riparian phreatophytes of the southwestern United States: a stable isotope study

    International Nuclear Information System (INIS)

    Busch, D.E.; Ingraham, N.L.; Smith, S.D.

    1992-01-01

    Alluvial forest associations are often dominated by woody phreatophytes, plants that are tightly linked to aquifers for water uptake. Anthropogenic hydrological alterations (e.g., water impoundment or diversion) are of clear importance to riparian ecosystem function. Because decreased frequency of flooding and depression of water tables may, in effect, sever riparian plants from their natural water sources, research was undertaken to determine water uptake patterns for the dominant native and introduced woody taxa of riparian plant communities of the southwestern United States. At floodplain study sites along the Bill Williams and lower Colorado Rivers (Arizona, USA), naturally occurring D and 18 O were used to distinguish among potential water sources. Isotopic ratios from potential uptake locations were compared to water extracted from the dominant woody taxa of the study area (Populus fremontii, Salix gooddingii, and Tamarix ramosissima) to elucidate patterns of water absorption. Isotopic composition of water obtained from sapwood cores did not differ significantly from heartwood or branch water, suggesting that heartwood water exchange, stem capacitance, and phloem sap mixing may be inconsequential in actively transpiring Salix and Populus. There was evidence for close hydrologic linkage of river, ground, and soil water during the early part of the growing season. Surface soils exhibited D enrichment due to cumulative exposure to evaporation as the growing season progressed. Isotopic ratios of water extracted from Populus and Salix did not exhibit isotopic enrichment and were not significantly different from groundwater or saturated soil water sources, indicating a phreatophytic uptake pattern. Associations of isotopic ratios with water relations parameters indicated high levels of canopy evaporation and possible use of moisture from unsaturated alluvial soils in addition to groundwater in Tamarix. (author)

  12. Structural instability and ground state of the U{sub 2}Mo compound

    Energy Technology Data Exchange (ETDEWEB)

    Losada, E.L., E-mail: losada@cab.cnea.gov.ar [SIM" 3, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (Argentina); Garcés, J.E. [Gerencia de Investigación y Aplicaciones Nucleares, Comisión Nacional de Energía Atómica (Argentina)

    2015-11-15

    This work reports on the structural instability at T = 0 °K of the U{sub 2}Mo compound in the C11{sub b} structure under the distortion related to the C{sub 66} elastic constant. The electronic properties of U{sub 2}Mo such as density of states (DOS), bands and Fermi surface (FS) are studied to understand the source of the instability. The C11{sub b} structure can be interpreted as formed by parallel linear chains along the z-directions each one composed of successive U–Mo–U blocks. Hybridization due to electronic interactions inside the U–Mo–U blocks is slightly modified under the D{sub 6} distortion. The change in distance between chains modifies the U–U interaction and produces a split of f-states. The distorted structure is stabilized by a decrease in energy of the hybridized states, mainly between d-Mo and f-U states, together with the f-band split. Consequently, an induced Peierls distortion is produced in U{sub 2}Mo due to the D{sub 6} distortion. It is important to note that the results of this work indicate that the structure of the ground state of the U{sub 2}Mo compound is not the assumed C11{sub b} structure. It is suggested for the ground state a structure with hexagonal symmetry (P6 #168), ∼0.1 mRy below the energy of the recently proposed Pmmn structure. - Highlights: • Structural instability of the C11b compound due to the D6 deformation. • Induced Peierls distortion due to the D6 deformation. • Distorted structure is stabilized by hybridization and split of f-Uranium state. • P6 (#168) suggested ground state for the U{sub 2}Mo compound.

  13. Structural instability and ground state of the U_2Mo compound

    International Nuclear Information System (INIS)

    Losada, E.L.; Garcés, J.E.

    2015-01-01

    This work reports on the structural instability at T = 0 °K of the U_2Mo compound in the C11_b structure under the distortion related to the C_6_6 elastic constant. The electronic properties of U_2Mo such as density of states (DOS), bands and Fermi surface (FS) are studied to understand the source of the instability. The C11_b structure can be interpreted as formed by parallel linear chains along the z-directions each one composed of successive U–Mo–U blocks. Hybridization due to electronic interactions inside the U–Mo–U blocks is slightly modified under the D_6 distortion. The change in distance between chains modifies the U–U interaction and produces a split of f-states. The distorted structure is stabilized by a decrease in energy of the hybridized states, mainly between d-Mo and f-U states, together with the f-band split. Consequently, an induced Peierls distortion is produced in U_2Mo due to the D_6 distortion. It is important to note that the results of this work indicate that the structure of the ground state of the U_2Mo compound is not the assumed C11_b structure. It is suggested for the ground state a structure with hexagonal symmetry (P6 #168), ∼0.1 mRy below the energy of the recently proposed Pmmn structure. - Highlights: • Structural instability of the C11b compound due to the D6 deformation. • Induced Peierls distortion due to the D6 deformation. • Distorted structure is stabilized by hybridization and split of f-Uranium state. • P6 (#168) suggested ground state for the U_2Mo compound.

  14. Guidelines for earthquake ground motion definition for the eastern United States

    International Nuclear Information System (INIS)

    Gwaltney, R.C.; Aramayo, G.A.; Williams, R.T.

    1985-01-01

    Guidelines for the determination of earthquake ground-motion definition for the eastern United States are established in this paper. Both far-field and near-field guidelines are given. The guidelines were based on an extensive review of the current procedures for specifying ground motion in the United States. Both empirical and theoretical procedures were used in establishing the guidelines because of the low seismicity in the eastern United States. Only a few large to great (M > 7.5) sized earthquakes have occurred in this region, no evidence of tectonic surface ruptures related to historic or Holocene earthquakes have been found, and no currently active plate boundaries of any kind are known in this region. Very little instrumented data has been gathered in the East. Theoretical procedures are proposed so that in regions of almost no data a reasonable level of seismic ground motion activity can be assumed. The guidelines are to be used to develop the Safe Shutdown Earthquake, SSE. A new procedure for establishing the Operating Basis Earthquake, OBE, is proposed, in particular for the eastern United States. The OBE would be developed using a probabilistic assessment of the geological conditions and the recurrence of seismic events at a site. These guidelines should be useful in development of seismic design requirements for future reactors. 17 refs., 2 figs., 1 tab

  15. Effect of the ground state correlations in the density distribution and zero point fluctuations

    International Nuclear Information System (INIS)

    Barranco, F.; Broglia, R.A.

    1985-01-01

    The existence of collective vibrations in the spectrum implies that the description of the ground state in an independent particle model must be corrected. This is because of the zero point fluctuations induced by the collective vibrations, so that ground state correlations have to be included. These are taken into account via the diagrammatic expansion of the Nuclear Field Theory, giving place to a renormalization in the different properties of the ground state. As far as the density distribution is concerned, in a NFT consistent calculation, the largest contributions arise from diagrams that cannot be expressed in terms of backward going amplitudes of the phonon RPA wave function. For a given multipolarity the main correction comes from the low lying state. The giant resonance is of smaller relevance since it lies at larger energies in the response function. The octupole modes give the dominant contribution, and the effect in average becomes smaller as the multipolarity increases. These results agree quite well with those obtained taking into account the zero point fluctuations of the nuclear surface in the collective model with the Esbensen and Bertsch prescription, which the authors use to explain the anomalous behaviour of the mean square radii of the Calcium isotopes

  16. Determination of ground and excited state dipole moments of dipolar laser dyes by solvatochromic shift method.

    Science.gov (United States)

    Patil, S K; Wari, M N; Panicker, C Yohannan; Inamdar, S R

    2014-04-05

    The absorption and fluorescence spectra of three medium sized dipolar laser dyes: coumarin 478 (C478), coumarin 519 (C519) and coumarin 523 (C523) have been recorded and studied comprehensively in various solvents at room temperature. The absorption and fluorescence spectra of C478, C519 and C523 show a bathochromic and hypsochromic shifts with increasing solvent polarity indicate that the transitions involved are π→π(∗) and n→π(∗). Onsager radii determined from ab initio calculations were used in the determination of dipole moments. The ground and excited state dipole moments were evaluated by using solvatochromic correlations. It is observed that the dipole moment values of excited states (μe) are higher than corresponding ground state values (μg) for the solvents studied. The ground and excited state dipole moments of these probes computed from ab initio calculations and those determined experimentally are compared and the results are discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Random interactions, isospin, and the ground states of odd-A and odd-odd nuclei

    International Nuclear Information System (INIS)

    Horoi, Mihai; Volya, Alexander; Zelevinsky, Vladimir

    2002-01-01

    It was recently shown that the ground state quantum numbers of even-even nuclei have a high probability to be reproduced by an ensemble of random but rotationally invariant two-body interactions. In the present work we extend these investigations to odd-A and odd-odd nuclei, considering in particular the isospin effects. Studying the realistic shell model as well as the single-j model, we show that random interactions have a tendency to assign the lowest possible total angular momentum and isospin to the ground state. In the sd shell model this reproduces correctly the isospin but not the spin quantum numbers of actual odd-odd nuclei. An odd-even staggering effect in probability of various ground state quantum numbers is present for even-even and odd-odd nuclei, while it is smeared out for odd-A nuclei. The observed regularities suggest the underlying mechanism of bosonlike pairing of fermionic pairs in T=0 and T=1 states generated by the off-diagonal matrix elements of random interactions. The relation to the models of random spin interactions is briefly discussed

  18. Accurate adiabatic energy surfaces for the ground and first excited states of He2+

    International Nuclear Information System (INIS)

    Lee, E.P.F.

    1993-01-01

    Different factors affecting the accuracy of the computed energy surfaces of the ground and first excited state of He 2 + have been examined, including the choice of the one-and many-particle bases, the configurational space in the MRCI (multi-reference configuration interaction) calculations and other corrections such as the Davidson and the full counterpoise (CP) correction. From basis-variation studies, it was concluded that multi-reference direct-CI calculations (MRDCI) using CASSCF MOs and/or natural orbitals (NOs) from a smaller CISD calculation, gave results close to full CI. The computed dissociation energies, D e , for the ground and first excited state of He 2 + were 2.4670 (2.4659) eV and 17.2 (17.1) cm -1 , respectively, at the highest level [without and with CP correction for basis-set superposition errors (BSSE)] of calculation with an [11s8p3d1f] GTO contraction, in reasonably good agreement with previous calculations, and estimated correct values, where available. It is believed that the computed D e , and the energy surface for the first excited state should be reasonably accurate. However, for the ground state, the effects of multiple f functions and/or functions of higher angular momentum have not been investigated owing to limitation of the available computing resources. This is probably the only weakness is the present study. (Author)

  19. Guidelines for earthquake ground motion definition for the Eastern United States

    International Nuclear Information System (INIS)

    Gwaltney, R.C.; Aramayo, G.A.; Williams, R.T.

    1985-01-01

    Guidelines for the determination of earthquake ground-motion definition for the eastern United States are established in this paper. Both far-field and near-field guidelines are given. The guidelines were based on an extensive review of the current procedures for specifying ground motion in the United States. Both empirical and theoretical procedures were used in establishing the guidelines because of the low seismicity in the eastern United States. Only a few large to great (M > 7.5) sized earthquakes have occurred in this region, no evidence of tectonic surface ruptures related to historic or Holocene earthquakes have been found, and no currently active plate boundaries of any kind are known in this region. Very little instrumented data has been gathered in the East. Theoretical procedures are proposed so that in regions of almost no data a reasonable level of seismic ground motion activity can be assumed. The guidelines are to be used to develop the Safe Shutdown Earthquake, SSE. A new procedure for establishing the Operating Basis Earthquake, OBE, is proposed, in particular for the eastern United States. The OBE would be developed using a probabilistic assessment of the geological conditions and the recurrence of seismic events at a site. These guidelines should be useful in development of seismic design requirements for future reactors

  20. Induced quadrupolar singlet ground state of praseodymium in a modulated pyrochlore

    Science.gov (United States)

    van Duijn, J.; Kim, K. H.; Hur, N.; Ruiz-Bustos, R.; Adroja, D. T.; Bridges, F.; Daoud-Aladine, A.; Fernandez-Alonso, F.; Wen, J. J.; Kearney, V.; Huang, Q. Z.; Cheong, S.-W.; Perring, T. G.; Broholm, C.

    2017-09-01

    The complex structure and magnetism of Pr2 -xBixRu2O7 was investigated by neutron scattering and extended x-ray absorption fine structure. Pr has an approximate doublet ground state and the first excited state is a singlet. While the B -site (Ru) is well ordered throughout, this is not the case for the A -site (Pr/Bi). A broadened distribution for the Pr-O2 bond length at low temperature indicates the Pr environment varies from site to site even for x =0 . The environment about the Bi site is highly disordered ostensibly due to the 6 s lone pairs on Bi3 +. Correspondingly, we find that the non-Kramers doublet ground-state degeneracy, otherwise anticipated for Pr in the pyrochlore structure, is lifted so as to produce a quadrupolar singlet ground state with a spatially varying energy gap. For x =0 , below TN, the Ru sublattice orders antiferromagnetically, with propagation vector k =(0 ,0 ,0 ) as for Y2Ru2O7 . No ordering associated with the Pr sublattice is observed down to 100 mK. The low-energy magnetic response of Pr2 -xBixRu2O7 features a broad spectrum of magnetic excitations associated with inhomogeneous splitting of the Pr quasidoublet ground state. For x =0 (x =0.97 ), the spectrum is temperature dependent (independent). It appears disorder associated with Bi alloying enhances the inhomogeneous Pr crystal-field level splitting so that intersite interactions become irrelevant for x =0.97 . The structural complexity for the A -site may be reflected in the hysteretic uniform magnetization of B -site ruthenium in the Néel phase.

  1. Influence of ground state correlations on the properties of the first 2+ and 3- states in some Sm isotopes

    International Nuclear Information System (INIS)

    Navrotskaya-Rybarska, V.; Stoyanova, O.; Stoyanov, Ch.

    1980-01-01

    The influence of ground state correlations and of their coupling with the phonon amplitudes on the properties of the first collective states is investigated in some Sm isotopes. Equations for the eXcited state energies are derived using the variational principle. Formulae for the gap and quasiparticle energies are given. The numerical calculations are performed for sup(144-150)Sm. The energies of the 2 + - and 3 - - states and the B(E2) and B(E3) electric transition probability values are presented. The effects studied are shown to be small for sup(144-146)Sm but the collectivity of the 2sub(1)sup(+) and 3sub(1)sup(-) states decreases strongly for 150 Sm [ru

  2. Ground-state densities from the Rayleigh-Ritz variation principle and from density-functional theory.

    Science.gov (United States)

    Kvaal, Simen; Helgaker, Trygve

    2015-11-14

    The relationship between the densities of ground-state wave functions (i.e., the minimizers of the Rayleigh-Ritz variation principle) and the ground-state densities in density-functional theory (i.e., the minimizers of the Hohenberg-Kohn variation principle) is studied within the framework of convex conjugation, in a generic setting covering molecular systems, solid-state systems, and more. Having introduced admissible density functionals as functionals that produce the exact ground-state energy for a given external potential by minimizing over densities in the Hohenberg-Kohn variation principle, necessary and sufficient conditions on such functionals are established to ensure that the Rayleigh-Ritz ground-state densities and the Hohenberg-Kohn ground-state densities are identical. We apply the results to molecular systems in the Born-Oppenheimer approximation. For any given potential v ∈ L(3/2)(ℝ(3)) + L(∞)(ℝ(3)), we establish a one-to-one correspondence between the mixed ground-state densities of the Rayleigh-Ritz variation principle and the mixed ground-state densities of the Hohenberg-Kohn variation principle when the Lieb density-matrix constrained-search universal density functional is taken as the admissible functional. A similar one-to-one correspondence is established between the pure ground-state densities of the Rayleigh-Ritz variation principle and the pure ground-state densities obtained using the Hohenberg-Kohn variation principle with the Levy-Lieb pure-state constrained-search functional. In other words, all physical ground-state densities (pure or mixed) are recovered with these functionals and no false densities (i.e., minimizing densities that are not physical) exist. The importance of topology (i.e., choice of Banach space of densities and potentials) is emphasized and illustrated. The relevance of these results for current-density-functional theory is examined.

  3. Selective excitation of a vibrational level within the electronic ground state of a polyatomic molecule with ultra pulses

    CSIR Research Space (South Africa)

    de Clercq, L

    2010-09-01

    Full Text Available Coherent control of the upper vibrational level populations in the electronic ground state of a polyatomic molecule was simulated. Results indicate that selective excitation of a specific upper state level is possible...

  4. Ground state energy of an hydrogen atom confined in carbon nano-structures: a diffusion quantum Monte Carlo study

    International Nuclear Information System (INIS)

    Molayem, M.; Tayebi-Rad, Gh.; Esmaeli, L.; Namiranian, A.; Fouladvand, M. E.; Neek-Amal, M.

    2006-01-01

    Using the diffusion quantum monte Carlo method, the ground state energy of an Hydrogen atom confined in a carbon nano tube and a C60 molecule is calculated. For Hydrogen atom confined in small diameter tubes, the ground state energy shows significant deviation from a free Hydrogen atom, while with increasing the diameter this deviation tends to zero.

  5. Indolo[2,3-b]carbazoles with tunable ground states: How Clar's aromatic sextet determines the singlet biradical character

    KAUST Repository

    Luo, Ding; Lee, Sangsu; Zheng, Bin; Sun, Zhe; Zeng, Wangdong; Huang, Kuo-Wei; Furukawa, Ko; Kim, Dongho; Webster, Richard D.; Wu, Jishan

    2014-01-01

    and showed different ground states. Based on variable-temperature NMR/ESR measurements and density functional theory calculations, it was found that the indolo[2,3-b]carbazole derivative 1 is a persistent singlet biradical in the ground state with a moderate

  6. Spin-polarized ground state and exact quantization at ν=5/2

    Science.gov (United States)

    Pan, Wei

    2002-03-01

    The nature of the even-denominator fractional quantum Hall effect at ν=5/2 remains elusive, in particular, its ground state spin-polarization. An earlier, so-called "hollow core" model arrived at a spin-unpolarized wave function. The more recent calculations based on a model of BCS-like pairing of composite fermions, however, suggest that its ground state is spin-polarized. In this talk, I will first review the earlier experiments and then present our recent experimental results showing evidence for a spin-polarized state at ν=5/2. Our ultra-low temperature experiments on a high quality sample established the fully developed FQHE state at ν=5/2 as well as at ν=7/3 and 8/3, manifested by a vanishing R_xx and exact quantization of the Hall plateau. The tilted field experiments showed that the added in-plane magnetic fields not only destroyed the FQHE at ν=5/2, as seen before, but also induced an electrical anisotropy, which is now interpreted as a phase transition from a paired, spin-polarized ν=5/2 state to a stripe phase, not unlike the ones at ν=9/2, 11/2, etc in the N > 1 higher Landau levels. Furthermore, in the experiments on the heterojunction insulated-gate field-effect transistors (HIGFET) at dilution refrigerator temperatures, a strong R_xx minimum and a concomitant developing Hall plateau were observed at ν=5/2 in a magnetic field as high as 12.6 Tesla. This and the subsequent density dependent studies of its energy gap largely rule out a spin-singlet state and point quite convincingly towards a spin-polarized ground state at ν=5/2.

  7. The influence of nonlocal hybridization on ground-state properties of the Falicov-Kimball model

    International Nuclear Information System (INIS)

    Farkasovsky, Pavol

    2005-01-01

    The density matrix renormalization group is used to examine effects of nonlocal hybridization on ground-state properties of the Falicov-Kimball model (FKM) in one dimension. Special attention is devoted to the problem of hybridization-induced insulator-metal transition. It is shown that the picture of insulator-metal transitions found for the FKM with nonlocal hybridization strongly differs from one found for the FKM without hybridization (as well as with local hybridization). The effect of nonlocal hybridization is so strong that it can induce the insulator-metal transition, even in the half-filled band case where the ground states of the FKM without hybridization are insulating for all finite Coulomb interactions. Outside the half-filled band case the metal-insulator transition driven by pressure is found for finite values of nonlocal hybridization

  8. The Ground State Energy of a Dilute Bose Gas in Dimension $n\\geq 3$

    DEFF Research Database (Denmark)

    Aaen, Anders Gottfred

    We consider a Bose gas in spatial dimension n≥3 with a repulsive, radially symmetric two-body potential V. In the limit of low density ρ, the ground state energy per particle in the thermodynamic limit is shown to be (n−2)|Sn−1|an−2ρ, where |Sn−1| denotes the surface measure of the unit sphere...... in Rn, and a is the scattering length of V. Furthermore, for smooth and compactly supported two-body potentials, we derive an upper bound to the ground state energy with a correction term (1+γ)8π4a6ρ2|ln(a4ρ)| in 4 dimensions, where 0... dimensions. Finally, we use a grand canonical construction to give a simplified proof of the second order upper bound to the Lee-Huang-Yang formula, a result first obtained by Yau and Yin. We also test this method in 4 dimensions, but with a negative outcome....

  9. Ground state properties of new element Z=113 and its alpha decay chain

    International Nuclear Information System (INIS)

    Tai Fei; Chen Dinghan; Xu Chang; Ren Zhongzhou

    2005-01-01

    The authors investigate the ground state properties of the new element 278 113 and of the α-decay chain with different models, where the new element Z=113 has been produced at RIKEN in Japan by cold-fusion reaction. The experimental decay energies are reproduced by the deformed relativistic mean-field model, by the Skyrme-Hartree-Fock (SHF) model, and by the macroscopic-microscopic model. Theoretical half-lives also reasonably agree with the data. Calculations further show that prolate deformation is important for the ground states of the nuclei in the α-decay chain of 278 113. The common points and differences among different models are compared and discussed. (author)

  10. The resonating group method three cluster approach to the ground state 9 Li nucleus structure

    International Nuclear Information System (INIS)

    Filippov, G.F.; Pozdnyakov, Yu.A.; Terenetsky, K.O.; Verbitsky, V.P.

    1994-01-01

    The three-cluster approach for light atomic nuclei is formulated in frame of the algebraic version of resonating group method. Overlap integral and Hamiltonian matrix elements on generating functions are obtained for 9 Li nucleus. All permissible by Pauli principle 9 Li different cluster nucleon permutations were taken into account in the calculations. The results obtained can be easily generalised on any three-cluster system up to 12 C. Matrix elements obtained in the work were used in the variational calculations of the ground state energetic and geometric 9 Li characteristics. It is shown that 9 Li ground state is not adequate to the shell model limit and has pronounced three-cluster structure. (author). 16 refs., 4 tab., 2 figs

  11. Towards the measurement of the ground-state hyperfine splitting of antihydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Juhasz, Bertalan, E-mail: bertalan.juhasz@oeaw.ac.at [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics (Austria)

    2012-12-15

    The ASACUSA collaboration at the Antiproton Decelerator of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic beam line, which will consist of a superconducting cusp trap as a source of partially polarized antihydrogen atoms, a radiofrequency spin-flip cavity, a superconducting sextupole magnet as spin analyser, and an antihydrogen detector. This will be a measurement of the antiproton magnetic moment, and also a test of the CPT invariance. Monte Carlo simulations predict that the antihydrogen ground-state hyperfine splitting can be determined with a relative precision of better than {approx} 10{sup - 6}. The first preliminary measurements of the hyperfine transitions will start in 2011.

  12. Ground state of a hydrogen ion molecule immersed in an inhomogeneous electron gas

    International Nuclear Information System (INIS)

    Diaz-Valdes, J.; Gutierrez, F.A.; Matamala, A.R.; Denton, C.D.; Vargas, P.; Valdes, J.E.

    2007-01-01

    In this work we have calculated the ground state energy of the hydrogen molecule, H 2 + , immersed in the highly inhomogeneous electron gas around a metallic surface within the local density approximation. The molecule is perturbed by the electron density of a crystalline surface of Au with the internuclear axis parallel to the surface. The surface spatial electron density is calculated through a linearized band structure method (LMTO-DFT). The ground state of the molecule-ion was calculated using the Born-Oppenheimer approximation for a fixed-ion while the screening effects of the inhomogeneous electron gas are depicted by a Thomas-Fermi like electrostatic potential. We found that within our model the molecular ion dissociates at the critical distance of 2.35a.u. from the first atomic layer of the solid

  13. Green function iterative solution of ground state wave function for Yukawa potential

    International Nuclear Information System (INIS)

    Zhang Zhao

    2003-01-01

    The newly developed single trajectory quadrature method is applied to solve central potentials. First, based on the series expansion method an exact analytic solution of the ground state for Hulthen potential and an approximate solution for Yukawa potential are obtained respectively. Second, the newly developed iterative method based on Green function defined by quadratures along the single trajectory is applied to solve Yukawa potential using the Coulomb solution and Hulthen solution as the trial functions respectively. The results show that a more proper choice of the trial function will give a better convergence. To further improve the convergence the iterative method is combined with the variational method to solve the ground state wave function for Yukawa potential, using variational solutions of the Coulomb and Hulthen potentials as the trial functions. The results give much better convergence. Finally, the obtained critical screen coefficient is applied to discuss the dissociate temperature of J/ψ in high temperature QGP

  14. Electron momentum spectroscopy of aniline taking account of nuclear dynamics in the initial electronic ground state

    International Nuclear Information System (INIS)

    Farasat, M; Golzan, M M; Shojaei, S H R; Morini, F; Deleuze, M S

    2016-01-01

    The electronic structure, electron binding energy spectrum and (e, 2e) momentum distributions of aniline have been theoretically predicted at an electron impact energy of 1.500 keV on the basis of Born–Oppenheimer molecular dynamical simulations, in order to account for thermally induced nuclear motions in the initial electronic ground state. Most computed momentum profiles are rather insensitive to thermally induced alterations of the molecular structure, with the exception of the profiles corresponding to two ionization bands at electron binding energies comprised between ∼10.0 and ∼12.0 eV (band C) and between ∼16.5 and ∼20.0 eV (band G). These profiles are found to be strongly influenced by nuclear dynamics in the electronic ground state, especially in the low momentum region. The obtained results show that thermal averaging smears out most generally the spectral fingerprints that are induced by nitrogen inversion. (paper)

  15. Is it also possible to describe a system of correlated nucleons in its ground state by an independent particle state

    International Nuclear Information System (INIS)

    Desplanques, B.

    1989-12-01

    The concept of nucleon in nuclei has often been referred to in recent literature. What it is used for is rarely precised however. In this paper, it is shown (or reminded) that the nucleon in nuclei is a model dependent object. As an illustration, it is shown that nuclear matter in its ground state may be described to a good approximation, if not exactly, by an independent particle state and that the on-shell G-matrix used in calculating its binding energy gets its effective character from that of those particles. The expression of these particles in terms of free nucleon operators is given

  16. Application of Stochastic variational method with correlated Ground States to coulombic systems

    Energy Technology Data Exchange (ETDEWEB)

    Usukura, Junko; Suzuki, Yasuyuki [Niigata Univ. (Japan); Varga, K.

    1998-07-01

    Positronium molecule, Ps{sub 2} has not been found experimentally yet, and it has been believed theoretically that Ps{sub 2} has only one bound state with L = 0. We predicted the existence of new bound state of Ps{sub 2}, which is the excited state with L = 1 and comes from Pauli principle, by Stochastic variational method. There are two decay mode with respect to Ps{sub 2}(P); one is pair annihilation and another is electric dipole (E1) transition to the ground state. While it is difficult to tell {gamma}-ray caused by annihilation of Ps{sub 2} from that of Ps since both of them have same energy, Energy (4.94 eV) of the photon emitted in E1 transition is specific enough to distinguish from other spectra. Then the excited state is one of clues to observe Ps{sub 2}. (author)

  17. The properties of 4'-N,N-dimethylaminoflavonol in the ground and excited states

    Science.gov (United States)

    Moroz, V. V.; Chalyi, A. G.; Roshal, A. D.

    2008-09-01

    The mechanism of protonation of 4-N,N-dimethylaminoflavonol and the structure of its protolytic forms in the ground and excited states were studied by electron absorption and fluorescence (steady-state and time-resolved) spectroscopy and with the use of the RM1 quantum-chemical method. A comparison of equilibrium constants and the theoretical enthalpies of formation showed that excitation should be accompanied by the inversion of the basicity of the electron acceptor groups of this compound and, as a consequence, changes in the structure of its monocationic form. An analysis of the spectral parameters of the protolytic 4-N,N-dimethylaminoflavonol forms, however, showed that their structure and the sequence of protonation in the excited state were the same as in the ground state. Changes in the structure of the monocation in the excited state were not observed because of the fast radiationless deactivation of this form and the occurrence of excited state intramolecular proton transfer in aprotic solvents.

  18. Prospects for studies of ground-state proton decays with the Holifield Radioactive Ion Beam Facility

    International Nuclear Information System (INIS)

    Toth, K.S.

    1994-01-01

    By using radioactive ions from the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory it should be possible to identify many new ground-state proton emitters in the mass region from Sn to Pb. During this production and search process the limits of stability on the proton-rich side of the nuclidic chart will be delineated for a significant fraction of medium-weight elements and our understanding of the proton-emission process will be expanded and improved

  19. Ground-state triply and doubly heavy baryons in a relativistic three-quark model

    International Nuclear Information System (INIS)

    Martynenko, A.P.

    2008-01-01

    Mass spectra of the ground-state baryons consisting of three or two heavy (b or c) and one light (u,d,s) quarks are calculated in the framework of the relativistic quark model and the hyperspherical expansion. The predictions of masses of the triply and doubly heavy baryons are obtained by employing the perturbation theory for the spin-independent and spin-dependent parts of the three-quark Hamiltonian

  20. On the ground state and infrared divergences of Goldstone bosons in two dimensions

    International Nuclear Information System (INIS)

    Jevicki, A.

    1977-01-01

    The O(N) invariant Goldstone field theory is studied in two dimensions where rigorous theorems forbid the occurrence of spontaneous symmetry breaking. It is agreed that for computation of the ground state energy at weak coupling it is still the standard Goldstone perturbation expansion that is applicable. This happens due to cancellation of infrared divergences and this fact is demonstrated explicitly at the two-loop level. (Auth.)

  1. Ground state representation of the infinite one-dimensional Heisenberg ferromagnet. Pt. 2

    International Nuclear Information System (INIS)

    Babbitt, D.; Thomas, L.

    1977-01-01

    In its ground state representation, the infinite, spin 1/2 Heisenberg chain provides a model for spin wave scattering, which entails many features of the quantum mechanical N-body problem. Here, we give a complete eigenfunction expansion for the Hamiltonian of the chain in this representation, for all numbers of spin waves. Our results resolve the questions of completeness and orthogonality of the eigenfunctions given by Bethe for finite chains, in the infinite volume limit. (orig.) [de

  2. Potential energy curve of Be2 in its ground electronic state

    Czech Academy of Sciences Publication Activity Database

    Špirko, Vladimír

    2006-01-01

    Roč. 235, č. 2 (2006), s. 268-270 ISSN 0022-2852 R&D Projects: GA AV ČR(CZ) IAA400550511 Institutional research plan: CEZ:AV0Z40550506 Keywords : ground electronic state of Be2 * MR-CI ab initio potentials * reduced potential curves Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.260, year: 2006

  3. Hydrogen-like atom in laser field: Invariant atomic parameters in the ground state

    International Nuclear Information System (INIS)

    Bondarev, I.V.; Kuten, S.A.

    1994-07-01

    The invariant atomic parameters (dynamical vector and tensor polarizabilities) of hydrogen-like atom in the ground 1S 1/2 state are calculated analytically by means of the Laplace transform of the radial Schroedinger equation. The obtained analytical expressions have been written in the compact form as a sum of linear and squared combinations of Gauss hypergeometric functions 2 F 1 . The frequency dependence of the invariant atomic parameters is analyzed. (author). 24 refs, 1 fig

  4. The electromagnetic virtual cloud of the ground-state hydrogen atom - a quantum field theory approach

    International Nuclear Information System (INIS)

    Radozycki, T.

    1990-01-01

    The properties of the virtual cloud around the hydrogen atom in the ground state are studied with the use of quantum field theory methods. The relativistic expression for the electromagnetic energy density around the atom, with the electron spin taken into account, is obtained. The distribution of the angular momentum contained in the cloud and the self-interaction kernel for the electrons bound in atom are also investigated. (author)

  5. Ground-state projection multigrid for propagators in 4-dimensional SU(2) gauge fields

    International Nuclear Information System (INIS)

    Kalkreuter, T.

    1991-09-01

    The ground-state projection multigrid method is studied for computations of slowly decaying bosonic propagators in 4-dimensional SU(2) lattice gauge theory. The defining eigenvalue equation for the restriction operator is solved exactly. Although the critical exponent z is not reduced in nontrivial gauge fields, multigrid still yields considerable speedup compared with conventional relaxation. Multigrid is also able to outperform the conjugate gradient algorithm. (orig.)

  6. Penn State University ground software support for X-ray missions.

    Science.gov (United States)

    Townsley, L. K.; Nousek, J. A.; Corbet, R. H. D.

    1995-03-01

    The X-ray group at Penn State is charged with two software development efforts in support of X-ray satellite missions. As part of the ACIS instrument team for AXAF, the authors are developing part of the ground software to support the instrument's calibration. They are also designing a translation program for Ginga data, to change it from the non-standard FRF format, which closely parallels the original telemetry format, to FITS.

  7. Ground State of the Universe and the Cosmological Constant. A Nonperturbative Analysis.

    Science.gov (United States)

    Husain, Viqar; Qureshi, Babar

    2016-02-12

    The physical Hamiltonian of a gravity-matter system depends on the choice of time, with the vacuum naturally identified as its ground state. We study the expanding Universe with scalar field in the volume time gauge. We show that the vacuum energy density computed from the resulting Hamiltonian is a nonlinear function of the cosmological constant and time. This result provides a new perspective on the relation between time, the cosmological constant, and vacuum energy.

  8. Exact ground state of finite Bose-Einstein condensates on a ring

    International Nuclear Information System (INIS)

    Sakmann, Kaspar; Streltsov, Alexej I.; Alon, Ofir E.; Cederbaum, Lorenz S.

    2005-01-01

    The exact ground state of the many-body Schroedinger equation for N bosons on a one-dimensional ring interacting via a pairwise δ-function interaction is presented for up to 50 particles. The solutions are obtained by solving Lieb and Liniger's system of coupled transcendental equations numerically for finite N. The ground-state energies for repulsive and attractive interactions are shown to be smoothly connected at the point of zero interaction strength, implying that the Bethe ansatz can be used also for attractive interactions for all cases studied. For repulsive interactions the exact energies are compared to (i) Lieb and Liniger's thermodynamic limit solution and (ii) the Tonks-Girardeau gas limit. It is found that the energy of the thermodynamic limit solution can differ substantially from that of the exact solution for finite N when the interaction is weak or when N is small. A simple relation between the Tonks-Girardeau gas limit and the solution for finite interaction strength is revealed. For attractive interactions we find that the true ground-state energy is given to a good approximation by the energy of the system of N attractive bosons on an infinite line, provided the interaction is stronger than the critical interaction strength of mean-field theory

  9. Density-matrix-functional calculations for matter in strong magnetic fields: Ground states of heavy atoms

    DEFF Research Database (Denmark)

    Johnsen, Kristinn; Yngvason, Jakob

    1996-01-01

    We report on a numerical study of the density matrix functional introduced by Lieb, Solovej, and Yngvason for the investigation of heavy atoms in high magnetic fields. This functional describes exactly the quantum mechanical ground state of atoms and ions in the limit when the nuclear charge Z...... and the electron number N tend to infinity with N/Z fixed, and the magnetic field B tends to infinity in such a way that B/Z4/3→∞. We have calculated electronic density profiles and ground-state energies for values of the parameters that prevail on neutron star surfaces and compared them with results obtained...... by other methods. For iron at B=1012 G the ground-state energy differs by less than 2% from the Hartree-Fock value. We have also studied the maximal negative ionization of heavy atoms in this model at various field strengths. In contrast to Thomas-Fermi type theories atoms can bind excess negative charge...

  10. Ground beetles (Coleoptera, Carabidae of the Hanford Nuclear Site in south-central Washington State

    Directory of Open Access Journals (Sweden)

    Chris Looney

    2014-04-01

    Full Text Available In this paper we report on ground beetles (Coleoptera: Carabidae collected from the Hanford Nuclear Reservation and Hanford National Monument (together the Hanford Site, which is located in south-central Washington State. The Site is a relatively undisturbed relict of the shrub-steppe habitat present throughout much of the western Columbia Basin before the westward expansion of the United States. Species, localities, months of capture, and capture method are reported for field work conducted between 1994 and 2002. Most species were collected using pitfall traps, although other capture methods were employed. Trapping results indicate the Hanford Site supports a diverse ground beetle community, with over 90% of the 92 species captured native to North America. Four species collected during the study period are newly recorded for Washington State: Bembidion diligens Casey, Calosoma obsoletum Say, Pseudaptinus rufulus (LeConte, and Stenolophus lineola (Fabricius. Based on these data, the Site maintains a diverse ground beetle fauna and, due to its size and diversity of habitats, is an important repository of shrub-steppe biodiversity.

  11. Emergent Ising degrees of freedom above a double-stripe magnetic ground state

    Science.gov (United States)

    Zhang, Guanghua; Flint, Rebecca

    2017-12-01

    Double-stripe magnetism [Q =(π /2 ,π /2 )] has been proposed as the magnetic ground state for both the iron-telluride and BaTi2Sb2O families of superconductors. Double-stripe order is captured within a J1-J2-J3 Heisenberg model in the regime J3≫J2≫J1 . Intriguingly, besides breaking spin-rotational symmetry, the ground-state manifold has three additional Ising degrees of freedom associated with bond ordering. Via their coupling to the lattice, they give rise to an orthorhombic distortion and to two nonuniform lattice distortions with wave vector (π ,π ) . Because the ground state is fourfold degenerate, modulo rotations in spin space, only two of these Ising bond order parameters are independent. Here, we introduce an effective field theory to treat all Ising order parameters, as well as magnetic order, and solve it within a large-N limit. All three transitions, corresponding to the condensations of two Ising bond order parameters and one magnetic order parameter are simultaneous and first order in three dimensions, but lower dimensionality, or equivalently weaker interlayer coupling, and weaker magnetoelastic coupling can split the three transitions, and in some cases allows for two separate Ising phase transitions above the magnetic one.

  12. High spin polarization and the origin of unique ferromagnetic ground state in CuFeSb

    International Nuclear Information System (INIS)

    Sirohi, Anshu; Saha, Preetha; Gayen, Sirshendu; Gaurav, Abhishek; Jyotsna, Shubhra; Sheet, Goutam; Singh, Chandan K.; Kabir, Mukul; Thakur, Gohil S.; Haque, Zeba; Gupta, L. C.; Ganguli, Ashok K.

    2016-01-01

    CuFeSb is isostructural to the ferro-pnictide and chalcogenide superconductors and it is one of the few materials in the family that are known to stabilize in a ferromagnetic ground state. Majority of the members of this family are either superconductors or antiferromagnets. Therefore, CuFeSb may be used as an ideal source of spin polarized current in spin-transport devices involving pnictide and the chalcogenide superconductors. However, for that the Fermi surface of CuFeSb needs to be sufficiently spin polarized. In this paper we report direct measurement of transport spin polarization in CuFeSb by spin-resolved Andreev reflection spectroscopy. From a number of measurements using multiple superconducting tips we found that the intrinsic transport spin polarization in CuFeSb is high (∼47%). In order to understand the unique ground state of CuFeSb and the origin of large spin polarization at the Fermi level, we have evaluated the spin-polarized band structure of CuFeSb through first principles calculations. Apart from supporting the observed 47% transport spin polarization, such calculations also indicate that the Sb-Fe-Sb angles and the height of Sb from the Fe plane are strikingly different for CuFeSb than the equivalent parameters in other members of the same family thereby explaining the origin of the unique ground state of CuFeSb.

  13. High spin polarization and the origin of unique ferromagnetic ground state in CuFeSb

    Energy Technology Data Exchange (ETDEWEB)

    Sirohi, Anshu; Saha, Preetha; Gayen, Sirshendu; Gaurav, Abhishek; Jyotsna, Shubhra; Sheet, Goutam, E-mail: goutam@iisermohali.ac.in [Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S. A. S. Nagar, Manauli PO 140306 (India); Singh, Chandan K.; Kabir, Mukul [Department of Physics, Indian Institute of Science Education and Research, Pune 411008 (India); Thakur, Gohil S.; Haque, Zeba; Gupta, L. C. [Department of Chemistry, Indian Institute of Technology, New Delhi 110016 (India); Ganguli, Ashok K. [Department of Chemistry, Indian Institute of Technology, New Delhi 110016 (India); Institute of Nano Science & Technology, Mohali 160064 (India)

    2016-06-13

    CuFeSb is isostructural to the ferro-pnictide and chalcogenide superconductors and it is one of the few materials in the family that are known to stabilize in a ferromagnetic ground state. Majority of the members of this family are either superconductors or antiferromagnets. Therefore, CuFeSb may be used as an ideal source of spin polarized current in spin-transport devices involving pnictide and the chalcogenide superconductors. However, for that the Fermi surface of CuFeSb needs to be sufficiently spin polarized. In this paper we report direct measurement of transport spin polarization in CuFeSb by spin-resolved Andreev reflection spectroscopy. From a number of measurements using multiple superconducting tips we found that the intrinsic transport spin polarization in CuFeSb is high (∼47%). In order to understand the unique ground state of CuFeSb and the origin of large spin polarization at the Fermi level, we have evaluated the spin-polarized band structure of CuFeSb through first principles calculations. Apart from supporting the observed 47% transport spin polarization, such calculations also indicate that the Sb-Fe-Sb angles and the height of Sb from the Fe plane are strikingly different for CuFeSb than the equivalent parameters in other members of the same family thereby explaining the origin of the unique ground state of CuFeSb.

  14. Mechanical properties of ground state structures in substitutional ordered alloys: High strength, high ductility and high thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Tawancy, H.M., E-mail: tawancy@kfupm.edu.sa [Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, KFUPM Box 1639, Dhahran 31261 (Saudi Arabia); Aboelfotoh, M.O., E-mail: oaboelfotoh@gmail.com [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27606 (United States)

    2014-05-01

    We have studied the effect of atom arrangements in the ground state structures of substitutional ordered alloys on their mechanical properties using nickel–molybdenum-based alloys as model systems. Three alloys with nominal compositions of Ni–19.43 at% Mo, Ni–18.53 at% Mo–15.21 at% Cr and Ni–18.72 at% Mo–6.14 at% Nb are included in the study. In agreement with theoretical predictions, the closely related Pt{sub 2}Mo-type, DO{sub 22} and D1{sub a} superlattices with similar energies are identified by electron diffraction of ground state structures, which can directly be derived from the parent disordered fcc structure by minor atom rearrangements on {420}{sub fcc} planes. The three superlattices are observed to coexist during the disorder–order transformation at 700 °C with the most stable superlattice being determined by the exact chemical composition. Although most of the slip systems in the parent disordered fcc structure are suppressed, many of the twinning systems remain operative in the superlattices favoring deformation by twinning, which leads to considerable strengthening while maintaining high ductility levels. Both the Pt{sub 2}Mo-type and DO{sub 22} superlattices are distinguished by high strength and high ductility due to their nanoscale microstructures, which have high thermal stability. However, the D1{sub a} superlattice is found to exhibit poor thermal stability leading to considerable loss of ductility, which has been correlated with self-induced recrystallization by migration of grain boundaries.

  15. Electrochemical and spectroscopic studies of some less stable oxidation states of selected lanthanide and actinide elements

    International Nuclear Information System (INIS)

    Hobart, D.E.

    1981-06-01

    Simultaneous observation of electrochemical and spectroscopic properties (spectroelectrochemistry) at optically transparent electrodes (OTE's) was used to study some less stable oxidation states of selected lanthanide and actinide elements. Cyclic voltammetry at microelectrodes was used in conjunction with spectroelectrochemistry for the study of redox couples. Additional analytical techniques were used. The formal reduction potential (E 0 ') values of the M(III)/M(II) redox couples in 1 M KCl at pH 6 were -0.34 +- 0.01 V for Eu, -1.18 +- 0.01 V for Yb, and -1.50 +- 0.01 V for Sm. Spectropotentiostatic determination of E 0 ' for the Eu(III)/Eu(II) redox couple yielded a value of -0.391 +- 0.005 V. Spectropotentiostatic measurement of the Ce(IV)/Ce(III) redox couple in concentrated carbonate solution gave E 0 ' equal to 0.051 +- 0.005 V, which is about 1.7 V less positive than the E 0 ' value in noncomplexing solution. This same difference in potential was observed for the E 0 ' values of the Pr(IV)/Pr(III) and Tb(IV)/Tb(III) redox couples in carbonate solution, and thus Pr(IV) and Tb(IV) were stabilized in this medium. The U(VI)/U(V)/U(IV) and U(IV)/U(III) redox couples were studied in 1 M KCl at OTE's. Spectropotentiostatic measurement of the Np(VI)/Np(V) redox couple in 1 M HClO 4 gave an E 0 ' value of 1.140 +- 0.005 V. An E 0 ' value of 0.46 +- 0.01 V for the Np(VII)/Np(VI) couple was found by voltammetry. Oxidation of Am(III) was studied in concentrated carbonate solution, and a reversible cyclic voltammogram for the Am(IV)/Am(III) couple yielded E 0 ' = 0.92 +- 0.01 V in this medium; this value was used to estimate the standard reduction potential (E 0 ) of the couple as 2.62 +- 0.01 V. Attempts to oxidize Cm(III) in concentrated carbonate solution were not successful which suggests that the predicted E 0 value for the Cm(IV)/Cm(III) redox couple may be in error

  16. Application of the random phase approximation to some atoms with ns2 ground state configurations

    International Nuclear Information System (INIS)

    Wright, L.A.

    1975-01-01

    Atomic bound state properties such as excitation energies and oscillator strengths were calculated by the Random Phase Approximation (RPA), also known as the Time Dependent Hartree-Fock Approximation (TDHFA). The RPA is equivalent to describing excited states as the creation of particle-hole pairs and the application to atoms is important for two reasons: the wide range of densities in an atom will cause the physical interpretation and mathematical approximations to be much different than with a uniform density system, such as an electron gas; this method could detect the existence of collective states in atoms similar to those responsible for the giant dipole resonances in nuclei. The method is shown to be superior to the H-F method in three basic ways: (1) The RPA contains explicit correlations between the excited and ground states. These are not included in the H-F theory. One can apply this method to large atoms since only these correlations are explicitly included. (2) The RPA calculates excitation energies directly without recourse to highly correlated ground state wavefunctions. This is in contrast to the method of configuration mixing which is known to have slow convergence properties. (3) Oscillator strengths and photoionization cross sections can be calculated by finding the eigenvectors corresponding excitation energy eigenvalues. The strength of the RPA is that the excitation energies and oscillator strengths, which are relative quantities, are calculated directly. The results for the oscillator strengths show an improvement of up to 45 percent over the H-F values and an improvement over the RPA done with Hartree wavefunctions by as much as 65 percent. The work was limited to atoms with an ns 2 ground state configuration. These atoms were He, Be, Mg and Ca

  17. Frequency dependent polarizabilities for the ground state of H2, HD, and D2

    International Nuclear Information System (INIS)

    Rychlewski, J.

    1983-01-01

    A variation-perturbation method has been employed to calculate the dynamic dipole polarizability for the ground state of the hydrogen molecule. The explicit correlated electronic wave functions were used. The averaged values of α(#betta#) and #betta#(#betta#) for several vibration-rotation states of HD and D 2 are presented. Similar values for H 2 have also been calculated and were used to test the efficiency of the method and the validity of the assumption applied in the present calculation. The agreement of the present theoretical results with the existing experimental data is found to be satisfactory

  18. Trophic ecology of Atlantic Bluefin Tuna (Thunnus thynnus [corrected] larvae from the Gulf of Mexico and NW Mediterranean spawning grounds: A Comparative Stable Isotope Study.

    Directory of Open Access Journals (Sweden)

    Raúl Laiz-Carrión

    Full Text Available The present study uses stable isotopes of nitrogen and carbon (δ15Nandδ13C as trophic indicators for Atlantic bluefin tuna larvae (BFT (6-10 mm standard length in the highly contrasting environmental conditions of the Gulf of Mexico (GOM and the Balearic Sea (MED. These regions are differentiated by their temperature regime and relative productivity, with the GOM being significantly warmer and more productive. MED BFT larvae showed the highest δ15N signatures, implying an elevated trophic position above the underlying microzooplankton baseline. Ontogenetic dietary shifts were observed in the BFT larvae from the GOM and MED which indicates early life trophodynamics differences between these spawning habitats. Significant trophic differences between the GOM and MED larvae were observed in relation to δ15N signatures in favour of the MED larvae, which may have important implications in their growth during their early life stages.These low δ15N levels in the zooplankton from the GOM may be an indication of a shifting isotopic baseline in pelagic food webs due to diatrophic inputs by cyanobacteria. Lack of enrichment for δ15N in BFT larvae compared to zooplankton implies an alternative grazing pathway from the traditional food chain of phytoplankton-zooplankton-larval fish. Results provide insight for a comparative characterization of the trophic pathways variability of the two main spawning grounds for BFT larvae.

  19. Alteration of the ground state by external magnetic fields. [External field, coupling constant ratio, static tree level approximation

    Energy Technology Data Exchange (ETDEWEB)

    Harrington, B J; Shepard, H K [New Hampshire Univ., Durham (USA). Dept. of Physics

    1976-03-22

    By fully exploiting the mathematical and physical analogy to the Ginzburg-Landau theory of superconductivity, a complete discussion of the ground state behavior of the four-dimensional Abelian Higgs model in the static tree level approximation is presented. It is shown that a sufficiently strong external magnetic field can alter the ground state of the theory by restoring a spontaneously broken symmetry, or by creating a qualitatively different 'vortex' state. The energetically favored ground state is explicitly determined as a function of the external field and the ratio between coupling constants of the theory.

  20. Studies of photoionization processes from ground-state and excited-state atoms and molecules

    International Nuclear Information System (INIS)

    Ederer, D.L.; Parr, A.C.; West, J.B.

    1982-01-01

    Recent triply-differential photoelectron spectroscopy experiments designed for the study of correlation effects in atoms and molecules are described. Final-state symmetry of the n=2 state of helium has been determined. The non-Franck-Condon behavior of vibrational branching ratios and large variations of the angular asymmetry parameter has been observed for shape resonances and autoionizing resonances in CO and other molecules. Recent observations of the photoionization of excited sodium atoms are also described

  1. Input-to-State Stabilizing MPC for Neutrally Stable Linear Systems subject to Input Constraints

    NARCIS (Netherlands)

    Kim, Jung-Su; Yoon, Tae-Woong; Jadbabaie, Ali; Persis, Claudio De

    2004-01-01

    MPC(Model Predictive Control) is representative of control methods which are able to handle physical constraints. Closed-loop stability can therefore be ensured only locally in the presence of constraints of this type. However, if the system is neutrally stable, and if the constraints are imposed

  2. Quantifying confidence in density functional theory predictions of magnetic ground states

    Science.gov (United States)

    Houchins, Gregory; Viswanathan, Venkatasubramanian

    2017-10-01

    Density functional theory (DFT) simulations, at the generalized gradient approximation (GGA) level, are being routinely used for material discovery based on high-throughput descriptor-based searches. The success of descriptor-based material design relies on eliminating bad candidates and keeping good candidates for further investigation. While DFT has been widely successfully for the former, oftentimes good candidates are lost due to the uncertainty associated with the DFT-predicted material properties. Uncertainty associated with DFT predictions has gained prominence and has led to the development of exchange correlation functionals that have built-in error estimation capability. In this work, we demonstrate the use of built-in error estimation capabilities within the BEEF-vdW exchange correlation functional for quantifying the uncertainty associated with the magnetic ground state of solids. We demonstrate this approach by calculating the uncertainty estimate for the energy difference between the different magnetic states of solids and compare them against a range of GGA exchange correlation functionals as is done in many first-principles calculations of materials. We show that this estimate reasonably bounds the range of values obtained with the different GGA functionals. The estimate is determined as a postprocessing step and thus provides a computationally robust and systematic approach to estimating uncertainty associated with predictions of magnetic ground states. We define a confidence value (c-value) that incorporates all calculated magnetic states in order to quantify the concurrence of the prediction at the GGA level and argue that predictions of magnetic ground states from GGA level DFT is incomplete without an accompanying c-value. We demonstrate the utility of this method using a case study of Li-ion and Na-ion cathode materials and the c-value metric correctly identifies that GGA-level DFT will have low predictability for NaFePO4F . Further, there

  3. Ground-state thermodynamics of bistable redox-active donor-acceptor mechanically interlocked molecules.

    Science.gov (United States)

    Fahrenbach, Albert C; Bruns, Carson J; Cao, Dennis; Stoddart, J Fraser

    2012-09-18

    Fashioned through billions of years of evolution, biological molecular machines, such as ATP synthase, myosin, and kinesin, use the intricate relative motions of their components to drive some of life's most essential processes. Having control over the motions in molecules is imperative for life to function, and many chemists have designed, synthesized, and investigated artificial molecular systems that also express controllable motions within molecules. Using bistable mechanically interlocked molecules (MIMs), based on donor-acceptor recognition motifs, we have sought to imitate the sophisticated nanoscale machines present in living systems. In this Account, we analyze the thermodynamic characteristics of a series of redox-switchable [2]rotaxanes and [2]catenanes. Control and understanding of the relative intramolecular movements of components in MIMs have been vital in the development of a variety of applications of these compounds ranging from molecular electronic devices to drug delivery systems. These bistable donor-acceptor MIMs undergo redox-activated switching between two isomeric states. Under ambient conditions, the dominant translational isomer, the ground-state coconformation (GSCC), is in equilibrium with the less favored translational isomer, the metastable-state coconformation (MSCC). By manipulating the redox state of the recognition site associated with the GSCC, we can stimulate the relative movements of the components in these bistable MIMs. The thermodynamic parameters of model host-guest complexes provide a good starting point to rationalize the ratio of GSCC to MSCC at equilibrium. The bistable [2]rotaxanes show a strong correlation between the relative free energies of model complexes and the ground-state distribution constants (K(GS)). This relationship does not always hold for bistable [2]catenanes, most likely because of the additional steric and electronic constraints present when the two rings are mechanically interlocked with each other

  4. Stable Tetraquarks

    Energy Technology Data Exchange (ETDEWEB)

    Quigg, Chris [Fermilab

    2018-04-13

    For very heavy quarks, relations derived from heavy-quark symmetry imply novel narrow doubly heavy tetraquark states containing two heavy quarks and two light antiquarks. We predict that double-beauty states will be stable against strong decays, whereas the double-charm states and mixed beauty+charm states will dissociate into pairs of heavy-light mesons. Observing a new double-beauty state through its weak decays would establish the existence of tetraquarks and illuminate the role of heavy color-antitriplet diquarks as hadron constituents.

  5. An unusual high-spin ground state of Co3+ in octahedral coordination in brownmillerite-type cobalt oxide.

    Science.gov (United States)

    Istomin, S Ya; Tyablikov, O A; Kazakov, S M; Antipov, E V; Kurbakov, A I; Tsirlin, A A; Hollmann, N; Chin, Y Y; Lin, H-J; Chen, C T; Tanaka, A; Tjeng, L H; Hu, Z

    2015-06-21

    The crystal and magnetic structures of brownmillerite-like Sr(2)Co(1.2)Ga(0.8)O(5) with a stable Co(3+) oxidation state at both octahedral and tetrahedral sites are refined using neutron powder diffraction data collected at 2 K (S.G. Icmm, a = 5.6148(6) Å, b = 15.702(2) Å, c = 5.4543(6) Å; R(wp) = 0.0339, R(p) = 0.0443, χ(2) = 0.775). The very large tetragonal distortion of CoO(6) octahedra (1.9591(4) Å for Co-O(eq) and 2.257(6) Å for Co-O(ax)) could be beneficial for the stabilization of the long-sought intermediate-spin state of Co(3+) in perovskite-type oxides. However, the large magnetic moment of octahedral Co(3+) (3.82(7)μ(B)) indicates the conventional high-spin state of Co(3+) ions, which is further supported by the results of a combined theoretical and experimental soft X-ray absorption spectroscopy study at the Co-L(2,3) edges on Sr(2)Co(1.2)Ga(0.8)O(5). A high-spin ground state of Co(3+) in Sr(2)Co(1.2)Ga(0.8)O(5) resulted in much lower in comparison with a LaCoO(3) linear thermal expansion coefficient of 13.1 ppm K(-1) (298-1073 K) determined from high-temperature X-ray powder diffraction data collected in air.

  6. Ab initio optimization principle for the ground states of translationally invariant strongly correlated quantum lattice models.

    Science.gov (United States)

    Ran, Shi-Ju

    2016-05-01

    In this work, a simple and fundamental numeric scheme dubbed as ab initio optimization principle (AOP) is proposed for the ground states of translational invariant strongly correlated quantum lattice models. The idea is to transform a nondeterministic-polynomial-hard ground-state simulation with infinite degrees of freedom into a single optimization problem of a local function with finite number of physical and ancillary degrees of freedom. This work contributes mainly in the following aspects: (1) AOP provides a simple and efficient scheme to simulate the ground state by solving a local optimization problem. Its solution contains two kinds of boundary states, one of which play the role of the entanglement bath that mimics the interactions between a supercell and the infinite environment, and the other gives the ground state in a tensor network (TN) form. (2) In the sense of TN, a novel decomposition named as tensor ring decomposition (TRD) is proposed to implement AOP. Instead of following the contraction-truncation scheme used by many existing TN-based algorithms, TRD solves the contraction of a uniform TN in an opposite way by encoding the contraction in a set of self-consistent equations that automatically reconstruct the whole TN, making the simulation simple and unified; (3) AOP inherits and develops the ideas of different well-established methods, including the density matrix renormalization group (DMRG), infinite time-evolving block decimation (iTEBD), network contractor dynamics, density matrix embedding theory, etc., providing a unified perspective that is previously missing in this fields. (4) AOP as well as TRD give novel implications to existing TN-based algorithms: A modified iTEBD is suggested and the two-dimensional (2D) AOP is argued to be an intrinsic 2D extension of DMRG that is based on infinite projected entangled pair state. This paper is focused on one-dimensional quantum models to present AOP. The benchmark is given on a transverse Ising

  7. Kelp Forests versus Urchin Barrens: Alternate Stable States and Their Effect on Sea Otter Prey Quality in the Aleutian Islands

    Directory of Open Access Journals (Sweden)

    Nathan L. Stewart

    2012-01-01

    Full Text Available Macroalgal and urchin barren communities are alternately stable and persist in the Aleutians due to sea otter presence and absence. In the early 1990s a rapid otter population decline released urchins from predation and caused a shift to the urchin-dominated state. Despite increases in urchin abundance, otter numbers continued to decline. Although debated, prey quality changes have been implicated in current otter population status. This study examined otter prey abundance, size, biomass, and potential energy density in remnant kelp forest and urchin-dominated communities to determine if alternate stable states affect prey quality. Findings suggest that although urchin barrens provide more abundant urchin prey, individual urchins are smaller and provide lower biomass and potential energy density compared to kelp forests. Shifts to urchin barrens do affect prey quality but changes are likely compensated by increased prey densities and are insufficient in explaining current otter population status in the Aleutians.

  8. Hydrochemical and isotopic study of the Botucatu aquifer ground waters in Sao Paulo State

    International Nuclear Information System (INIS)

    Silva, R.B.G. da.

    1983-01-01

    The process controlling chemical composition of ground water,its origin and apparent age as well as, the natural flow rate of the water in Botucatu aquifer in state of Sao Paulo, Brazil, have been investigated using hydrochemical and environmental isotopic ( 18 O, 2 H, 13 C, 14 C) Technics. The main recharge process is assumed to be the infiltration of rain water in the aquifer outcrop area. The progressive confining conditions with the increasing depth of the top of the aquifer layer makes the ground water temperature slowly greater. The recent magnesium and sodium bicarbonated waters changes first to sodium bicarbonated and then to sodium chloride-sulfated waters which are oldest found out in the research area(around 30.000 years ago). The mean Darcy permeability estimated on basis of 14 C and hydraulic gradient data is 2.6x10 -5 m/s. 9 maps (author) [pt

  9. Ab initio investigation of ground-states and ionic motion in particular in zirconia-based solid-oxide electrolytes

    International Nuclear Information System (INIS)

    Hirschfeld, Julian Arndt

    2012-01-01

    transport the ionic conductivity in SOFC electrolytes is required to be high. Using a layering of zirconium and yttrium in the fluorite structure and applying DFT and NEB again, a high vacancy concentration and a very low migration barrier in two dimensions is observed, while the mobility in the third direction is sacrificed. The ionic conductivity of this new structure at 500 C surpasses that of the state of the art electrolyte Yttrium Stabilized Zirconia (YSZ) at 800 C. Throughout the process of searching for augmented ionic conductivity, the NEB method has particularly been used extensively and has been examined in detail. This method has been applied to quite different systems to gain a better understanding of it. While NEB has been applied, it has been found that a certain modification of the NEB, the Minimum search Nudged Elastic Band (MsNEB), is able to find global minima in a complex phase space. Furthermore, the MsNEB turns out to be complementary to simulated annealing and the genetic algorithm. This new scheme has not been applied to electrolyte materials, yet. However, its capabilities have been demonstrated by detecting the most stable isomers of the phosphorus P 4 , P 8 molecules and the corresponding molecules of As n , Sb n , Bi n , (n=4,8). In the case of P 8 , the new MsNEB has led to a hitherto unknown configuration, being more stable than the previously assumed ground state.

  10. Ab initio investigation of ground-states and ionic motion in particular in zirconia-based solid-oxide electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Hirschfeld, Julian Arndt

    2012-12-11

    transport the ionic conductivity in SOFC electrolytes is required to be high. Using a layering of zirconium and yttrium in the fluorite structure and applying DFT and NEB again, a high vacancy concentration and a very low migration barrier in two dimensions is observed, while the mobility in the third direction is sacrificed. The ionic conductivity of this new structure at 500 C surpasses that of the state of the art electrolyte Yttrium Stabilized Zirconia (YSZ) at 800 C. Throughout the process of searching for augmented ionic conductivity, the NEB method has particularly been used extensively and has been examined in detail. This method has been applied to quite different systems to gain a better understanding of it. While NEB has been applied, it has been found that a certain modification of the NEB, the Minimum search Nudged Elastic Band (MsNEB), is able to find global minima in a complex phase space. Furthermore, the MsNEB turns out to be complementary to simulated annealing and the genetic algorithm. This new scheme has not been applied to electrolyte materials, yet. However, its capabilities have been demonstrated by detecting the most stable isomers of the phosphorus P{sub 4}, P{sub 8} molecules and the corresponding molecules of As{sub n}, Sb{sub n}, Bi{sub n}, (n=4,8). In the case of P{sub 8}, the new MsNEB has led to a hitherto unknown configuration, being more stable than the previously assumed ground state.

  11. Multitudes of Stable States in a Periodically Driven Electron-Nuclear Spin System in a Quantum Dot

    OpenAIRE

    Korenev, V. L.

    2010-01-01

    The periodical modulation of circularly polarized light with a frequency close to the electron spin resonance frequency induces a sharp change of the single electron spin orientation. Hyperfine interaction provides a feedback, thus fixing the precession frequency of the electron spin in the external and the Overhauser field near the modulation frequency. The nuclear polarization is bidirectional and the electron-nuclear spin system (ENSS) possesses a few stable states. A similar frequency-loc...

  12. Inhomogeneous quantum diffusion and decay of a meta-stable state

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Pulak Kumar [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Barik, Debashis [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Ray, Deb Shankar [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

    2007-01-29

    We consider the quantum stochastic dynamics of a system whose interaction with the reservoir is considered to be linear in bath co-ordinates but nonlinear in system co-ordinates. The role of the space-dependent friction and diffusion has been examined in the decay rate of a particle from a meta-stable well. We show how the decay rate can be hindered by inhomogeneous dissipation due to nonlinear system-bath coupling strength.

  13. Inhomogeneous quantum diffusion and decay of a meta-stable state

    International Nuclear Information System (INIS)

    Ghosh, Pulak Kumar; Barik, Debashis; Ray, Deb Shankar

    2007-01-01

    We consider the quantum stochastic dynamics of a system whose interaction with the reservoir is considered to be linear in bath co-ordinates but nonlinear in system co-ordinates. The role of the space-dependent friction and diffusion has been examined in the decay rate of a particle from a meta-stable well. We show how the decay rate can be hindered by inhomogeneous dissipation due to nonlinear system-bath coupling strength

  14. Inhomogeneous quantum diffusion and decay of a meta-stable state

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Pulak Kumar [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Barik, Debashis [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Ray, Deb Shankar [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

    2006-12-18

    We consider the quantum stochastic dynamics of a system whose interaction with the reservoir is considered to be linear in bath co-ordinates but nonlinear in system co-ordinates. The role of the space-dependent friction and diffusion has been examined in the decay rate of a particle from a meta-stable well. We show how the decay rate can be hindered by inhomogeneous dissipation due to nonlinear system-bath coupling strength.

  15. Inhomogeneous quantum diffusion and decay of a meta-stable state

    International Nuclear Information System (INIS)

    Ghosh, Pulak Kumar; Barik, Debashis; Ray, Deb Shankar

    2006-01-01

    We consider the quantum stochastic dynamics of a system whose interaction with the reservoir is considered to be linear in bath co-ordinates but nonlinear in system co-ordinates. The role of the space-dependent friction and diffusion has been examined in the decay rate of a particle from a meta-stable well. We show how the decay rate can be hindered by inhomogeneous dissipation due to nonlinear system-bath coupling strength

  16. Using narrowband excitation to confirm that the S∗ state in carotenoids is not a vibrationally-excited ground state species

    Science.gov (United States)

    Jailaubekov, Askat E.; Song, Sang-Hun; Vengris, Mikas; Cogdell, Richard J.; Larsen, Delmar S.

    2010-02-01

    The hypothesis that S∗ is a vibrationally-excited ground-state population is tested and discarded for two carotenoid samples: β-carotene in solution and rhodopin glucoside embedded in the light harvesting 2 protein from Rhodopseudomonas acidophila. By demonstrating that the transient absorption signals measured in both systems that are induced by broadband (1000 cm -1) and narrowband (50 cm -1) excitation pulses are near identical and hence bandwidth independent, the impulsive stimulated Raman scattering mechanism proposed as the primary source for S∗ generation is discarded. To support this conclusion, previously published multi-pulse pump-dump-probe signals [17] are revisited to discard secondary mechanisms for S∗ formation.

  17. Thermodynamic consideration and ground-state search of icosahedral boron subselenide B12(B1-xSex) 2 from a first-principles cluster expansion

    Science.gov (United States)

    Ektarawong, A.

    2018-05-01

    The phase stability of icosahedral boron subselenide B12(B1-xSex) 2 , where 0.5 ≤x ≤1 , is explored using a first-principles cluster expansion. The results shows that, instead of a continuous solid solution, B12(B1-xSex) 2 is thermodynamically stable as an individual line compound at the composition of B9.5Se . The ground-state configuration of B9.5Se is represented by a mixture of B12(Se-Se), B12(B-Se), and B12(Se-B) with a ratio of 1:1:1, where they form a periodic A B C A B C ⋯ stacking sequence of B12(Se-Se), B12(B-Se), and B12(Se-B) layers along the c axis of the hexagonal conventional unit cell. The structural and electronic properties of the ground-state B9.5Se are also derived and discussed. By comparing the derived ground-state properties of B9.5Se to the existing experimental data of boron subselenide B˜13Se , I proposed that the as-synthesized boron subselenide B˜13Se , as reported in the literature, has the actual composition of B9.5Se .

  18. Symmetry Breaking Ground States of Bose-Einstein Condensates in 1D Double Square Well and Optical Lattice Well

    International Nuclear Information System (INIS)

    Yuan Qingxin; Ding Guohui

    2005-01-01

    We investigate the phenomena of symmetry breaking and phase transition in the ground state of Bose-Einstein condensates (BECs) trapped in a double square well and in an optical lattice well, respectively. By using standing-wave expansion method, we present symmetric and asymmetric ground state solutions of nonlinear Schroedinger equation (NLSE) with a symmetric double square well potential for attractive nonlinearity. In particular, we study the ground state wave function's properties by changing the depth of potential and atomic interactions (here we restrict ourselves to the attractive regime). By using the Fourier grid Hamiltonian method, we also reveal a phase transition of BECs trapped in one-dimensional optical lattice potential.

  19. Perturbative correction to the ground-state properties of one-dimensional strongly interacting bosons in a harmonic trap

    International Nuclear Information System (INIS)

    Paraan, Francis N. C.; Korepin, Vladimir E.

    2010-01-01

    We calculate the first-order perturbation correction to the ground-state energy and chemical potential of a harmonically trapped boson gas with contact interactions about the infinite repulsion Tonks-Girardeau limit. With c denoting the interaction strength, we find that, for a large number of particles N, the 1/c correction to the ground-state energy increases as N 5/2 , in contrast to the unperturbed Tonks-Girardeau value that is proportional to N 2 . We describe a thermodynamic scaling limit for the trapping frequency that yields an extensive ground-state energy and reproduces the zero temperature thermodynamics obtained by a local-density approximation.

  20. The ground-state energy of the ± J sping glass. A comparison of various biologically motivated algorithms

    Science.gov (United States)

    Gropengiesser, Uwe

    1995-06-01

    We compare various evlutionary strategies to determine the ground-state energy of the ± J spin glass. We show that the choice of different evolution laws is less important than a suitable treatment of the "free spins" of the system At least one combination of these strategies does not give the correct results, but the ground states of the other different strategies coincide. Therefore we are able to extrapolate the infinit-size ground-state energy for the square lattice to -1.401±0.0015 and for the simple cubic lattice to -1.786±0.004.

  1. The ground state hydrogen conformations and vibrational analysis of 2-, 3-, 4- and 5- dihydroxybenzaldehyde: A DFT study

    International Nuclear Information System (INIS)

    Cirak, C.; Saglam, A.; Ucun, F.

    2010-01-01

    The ground state hydrogen conformations of 2-, 3-, 4- and 5-dihydroxybenzaldehyde have been investigated using density functional theory (B3LYP) methods with 6-31G (d,p) basis set. The calculations have indicated that the compounds in the ground state exist with the carbonyl group O atom linked intra molecularly by the two hydrogen bonds of the two hydroxyl groups. The vibrational analyses of the ground state conformers of all the compounds were done and their optimized geometry parameters were given.

  2. Exact ground-state phase diagrams for the spin-3/2 Blume-Emery-Griffiths model

    International Nuclear Information System (INIS)

    Canko, Osman; Keskin, Mustafa; Deviren, Bayram

    2008-01-01

    We have calculated the exact ground-state phase diagrams of the spin-3/2 Ising model using the method that was proposed and applied to the spin-1 Ising model by Dublenych (2005 Phys. Rev. B 71 012411). The calculated, exact ground-state phase diagrams on the diatomic and triangular lattices with the nearest-neighbor (NN) interaction have been presented in this paper. We have obtained seven and 15 topologically different ground-state phase diagrams for J>0 and J 0 and J<0, respectively, the conditions for the existence of uniform and intermediate phases have also been found

  3. Coherence and entanglement in the ground state of a bosonic Josephson junction: From macroscopic Schroedinger cat states to separable Fock states

    International Nuclear Information System (INIS)

    Mazzarella, G.; Toigo, F.; Salasnich, L.; Parola, A.

    2011-01-01

    We consider a bosonic Josephson junction made of N ultracold and dilute atoms confined by a quasi-one-dimensional double-well potential within the two-site Bose-Hubbard model framework. The behavior of the system is investigated at zero temperature by varying the interatomic interaction from the strongly attractive regime to the repulsive one. We show that the ground state exhibits a crossover from a macroscopic Schroedinger-cat state to a separable Fock state through an atomic coherent regime. By diagonalizing the Bose-Hubbard Hamiltonian we characterize the emergence of the macroscopic cat states by calculating the Fisher information F, the coherence by means of the visibility α of the interference fringes in the momentum distribution, and the quantum correlations by using the entanglement entropy S. Both Fisher information and visibility are shown to be related to the ground-state energy by employing the Hellmann-Feynman theorem. This result, together with a perturbative calculation of the ground-state energy, allows simple analytical formulas for F and α to be obtained over a range of interactions, in excellent agreement with the exact diagonalization of the Bose-Hubbard Hamiltonian. In the attractive regime the entanglement entropy attains values very close to its upper limit for a specific interaction strength lying in the region where coherence is lost and self-trapping sets in.

  4. Ground-state and pairing-vibrational bands with equal quadrupole collectivity in 124Xe

    Science.gov (United States)

    Radich, A. J.; Garrett, P. E.; Allmond, J. M.; Andreoiu, C.; Ball, G. C.; Bianco, L.; Bildstein, V.; Chagnon-Lessard, S.; Cross, D. S.; Demand, G. A.; Diaz Varela, A.; Dunlop, R.; Finlay, P.; Garnsworthy, A. B.; Hackman, G.; Hadinia, B.; Jigmeddorj, B.; Laffoley, A. T.; Leach, K. G.; Michetti-Wilson, J.; Orce, J. N.; Rajabali, M. M.; Rand, E. T.; Starosta, K.; Sumithrarachchi, C. S.; Svensson, C. E.; Triambak, S.; Wang, Z. M.; Wood, J. L.; Wong, J.; Williams, S. J.; Yates, S. W.

    2015-04-01

    The nuclear structure of 124Xe has been investigated via measurements of the β+/EC decay of 124Cs with the 8 π γ -ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled branching ratio measurements of weak, low-energy transitions from highly excited states, and the 2+→0+ in-band transitions have been observed. Combining these results with those from a previous Coulomb excitation study, B (E 2 ;23+→02+) =78 (13 ) W.u. and B (E 2 ;24+→03+) =53 (12 ) W.u. were determined. The 03+ state, in particular, is interpreted as the main fragment of the proton-pairing vibrational band identified in a previous 122Te (3He,n )124Xe measurement, and has quadrupole collectivity equal to, within uncertainty, that of the ground-state band.

  5. A grounded theory of young tennis players use of music to manipulate emotional state.

    Science.gov (United States)

    Bishop, Daniel T; Karageorghis, Costas I; Loizou, Georgios

    2007-10-01

    The main objectives of this study were (a) to elucidate young tennis players' use of music to manipulate emotional states, and (b) to present a model grounded in present data to illustrate this phenomenon and to stimulate further research. Anecdotal evidence suggests that music listening is used regularly by elite athletes as a preperformance strategy, but only limited empirical evidence corroborates such use. Young tennis players (N = 14) were selected purposively for interview and diary data collection. Results indicated that participants consciously selected music to elicit various emotional states; frequently reported consequences of music listening included improved mood, increased arousal, and visual and auditory imagery. The choice of music tracks and the impact of music listening were mediated by a number of factors, including extramusical associations, inspirational lyrics, music properties, and desired emotional state. Implications for the future investigation of preperformance music are discussed.

  6. Carotenoid deactivation in an artificial light-harvesting complex via a vibrationally hot ground state

    International Nuclear Information System (INIS)

    Savolainen, Janne; Buckup, Tiago; Hauer, Juergen; Jafarpour, Aliakbar; Serrat, Carles; Motzkus, Marcus; Herek, Jennifer L.

    2009-01-01

    Ultrafast relaxation of a carotenoid in an artificial light-harvesting complex has been studied by transient absorption spectroscopy. The transient signal amplitudes at several wavelengths as well as the amplitudes of the underlying species associated spectra (SAS) are analysed for several excitation energies ranging over more than two orders of magnitude (10 nJ/pulse up to 3000 nJ/pulse). Our analysis shows that the contribution from the so-called S* signal on the long-wavelength side of the first allowed S 0 → S 2 transition has a markedly different excitation energy dependence and saturation behaviour than the electronic excited state S 1 . These observations are modelled and explained in terms of a two-photon excitation of a vibrationally hot ground state via an impulsive stimulated Raman scattering (ISRS). The experimental observations of the varying pulse energy dependencies of different excited state species are supported by an analysis based on a density-matrix formalism

  7. Ground-water recharge in the arid and semiarid southwestern United States

    Science.gov (United States)

    Stonestrom, David A.; Constantz, Jim; Ferré, Ty P.A.; Leake, Stanley A.

    2007-01-01

    Ground-water recharge in the arid and semiarid southwestern United States results from the complex interplay of climate, geology, and vegetation across widely ranging spatial and temporal scales. Present-day recharge tends to be narrowly focused in time and space. Widespread water-table declines accompanied agricultural development during the twentieth century, demonstrating that sustainable ground-water supplies are not guaranteed when part of the extracted resource represents paleorecharge. Climatic controls on ground-water recharge range from seasonal cycles of summer monsoonal and winter frontal storms to multimillennial cycles of glacial and interglacial periods. Precipitation patterns reflect global-scale interactions among the oceans, atmosphere, and continents. Large-scale climatic influences associated with El Niño and Pacific Decadal Oscillations strongly, but irregularly, control weather in the study area, so that year-to-year variations in precipitation and ground-water recharge are large and difficult to predict. Proxy data indicate geologically recent periods of naturally occurring multidecadal droughts unlike any in the modern instrumental record. Any anthropogenically induced climate change will likely reduce ground-water recharge through diminished snowpack at higher elevations. Future changes in El Niño and monsoonal patterns, both crucial to precipitation in the study area, are highly uncertain in current models. Current land-use modifications influence ground-water recharge through vegetation, irrigation, and impermeable area. High mountain ranges bounding the study area—the San Bernadino Mountains and Sierra Nevada to the west, and the Wasatch and southern Colorado Rocky Mountains to the east—provide external geologic controls on ground-water recharge. Internal geologic controls stem from tectonic processes that led to numerous, variably connected alluvial-filled basins, exposure of extensive Paleozoic aquifers in mountainous recharge

  8. High Fidelity Preparation of a Single Atom in Its 2D Center of Mass Ground State

    Science.gov (United States)

    Sompet, Pimonpan; Fung, Yin Hsien; Schwartz, Eyal; Hunter, Matthew D. J.; Phrompao, Jindaratsamee; Andersen, Mikkel F.

    2017-04-01

    Complete control over quantum states of individual atoms is important for the study of the microscopic world. Here, we present a push button method for high fidelity preparation of a single 85Rb atom in the vibrational ground state of tightly focused optical tweezers. The method combines near-deterministic preparation of a single atom with magnetically-insensitive Raman sideband cooling. We achieve 2D cooling in the radial plane with a ground state population of 0.85, which provides a fidelity of 0.7 for the entire procedure (loading and cooling). The Raman beams couple two sublevels (| F = 3 , m = 0 〉 and | F = 2 , m = 0 〉) that are indifferent to magnetic noise to first order. This leads to long atomic coherence times, and allows us to implement the cooling in an environment where magnetic field fluctuations prohibit previously demonstrated variations. Additionally, we implement the trapping and manipulation of two atoms confined in separate dynamically reconfigurable optical tweezers, to study few-body dynamics.

  9. Ground-state energy of the interacting Bose gas in two dimensions: An explicit construction

    International Nuclear Information System (INIS)

    Beane, Silas R.

    2010-01-01

    The isotropic scattering phase shift is calculated for nonrelativistic bosons interacting at low energies via an arbitrary finite-range potential in d space-time dimensions. Scattering on a (d-1)-dimensional torus is then considered, and the eigenvalue equation relating the energy levels on the torus to the scattering phase shift is derived. With this technology in hand, and focusing on the case of two spatial dimensions, a perturbative expansion is developed for the ground-state energy of N identical bosons which interact via an arbitrary finite-range potential in a finite area. The leading nonuniversal effects due to range corrections and three-body forces are included. It is then shown that the thermodynamic limit of the ground-state energy in a finite area can be taken in closed form to obtain the energy per particle in the low-density expansion by explicitly summing the parts of the finite-area energy that diverge with powers of N. The leading and subleading finite-size corrections to the thermodynamic limit equation of state are also computed. Closed-form results--some well known, others perhaps not--for two-dimensional lattice sums are included in an Appendix.

  10. Ground beetles (Coleoptera, Carabidae) of the Hanford Nuclear Site in south-central Washington State.

    Science.gov (United States)

    Looney, Chris; Zack, Richard S; Labonte, James R

    2014-01-01

    Carabidae) collected from the Hanford Nuclear Reservation and Hanford National Monument (together the Hanford Site), which is located in south-central Washington State. The Site is a relatively undisturbed relict of the shrub-steppe habitat present throughout much of the western Columbia Basin before the westward expansion of the United States. Species, localities, months of capture, and capture method are reported for field work conducted between 1994 and 2002. Most species were collected using pitfall traps, although other capture methods were employed. Trapping results indicate the Hanford Site supports a diverse ground beetle community, with over 90% of the 92 species captured native to North America. Four species collected during the study period are newly recorded for Washington State: Bembidion diligens Casey, Calosoma obsoletum Say, Pseudaptinus rufulus (LeConte), and Stenolophus lineola (Fabricius). Based on these data, the Site maintains a diverse ground beetle fauna and, due to its size and diversity of habitats, is an important repository of shrub-steppe biodiversity.

  11. Structure and magnetic ground states of spin-orbit coupled compound alpha-RuCl3

    Science.gov (United States)

    Banerjee, Arnab; Bridges, Craig; Yan, Jiaqiang; Mandrus, David; Stone, Matthew; Aczel, Adam; Li, Ling; Yiu, Yuen; Lumsden, Mark; Chakoumakos, Bryan; Tennant, Alan; Nagler, Stephen

    2015-03-01

    The layered material alpha-RuCl3 is composed of stacks of weakly coupled honeycomb lattices of octahedrally coordinated Ru3 + ions. The Ru ion ground state has 5 d electrons in the low spin state, with spin-orbit coupling very strong compared to other terms in the single ion Hamiltonian. The material is therefore an excellent candidate for investigating possible Heisenberg-Kitaev physics. In addition, this compound is very amenable to investigation by neutron scattering to explore the magnetic ground state and excitations in detail. In this talk, we discuss the synthesis of phase-pure alpha-RuCl3 and the characterization of the magnetization, susceptibility, and heat-capacity. We also report neutron diffraction on both powder and single crystal alpha-RuCl3, identifying the low temperature magnetic order observed in the material. The results, when compared to theoretical calculations, shed light on the relative importance of Kitaev and Heisenberg terms in the Hamiltonian. The research is supported by the DOE BES Scientific User Facility Division.

  12. Quantum electrodynamics at strong electric fields. The ground state Lamb shift in hydrogenlike uranium

    Energy Technology Data Exchange (ETDEWEB)

    Gumberidze, A.; Stoehlker, T. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany)]|[Frankfurt Univ. (Germany). Inst. fuer Kernphysik; Banas, D. [Pedagogical Univ., Kielce (PL). Inst. of Phys.] [and others

    2005-05-01

    X-ray spectra following radiative recombination of free electrons with bare uranium ions (U{sup 92+}) were measured at the electron cooler of the ESR storage ring. The most intense lines observed in the spectra can be attributed to the characteristic Lyman ground-state transitions and to the recombination of free electrons into the K-shell of the ions. Our experiment was carried out by utilizing the deceleration technique which leads to a considerable reduction of the uncertainties associated with Doppler corrections. This, in combination with the 0 observation geometry, allowed us to determine the ground-state Lamb shift in hydrogen-like uranium (U{sup 91+}) from the observed X-ray lines with an accuracy of 1%. The present result is about 3 times more precise than the most accurate value available up to now and provides the most stringent test of bound-state quantum electrodynamics for one-electron systems in the strong-field regime. (orig.)

  13. Isospin mixing in the ground state of sup 5 sup 2 Mn

    CERN Document Server

    Schuurmans, P; Phalet, T; Severijns, N; Vereecke, B; Versyck, S

    2000-01-01

    The presence of isospin mixing into the ground state of sup 5 sup 2 Mn was studied via anisotropic positron emission from nuclei. With this method the isospin forbidden Fermi-component in the Gamow-Teller dominated beta decay was determined. It is shown that sample purity and the control of positron scattering is of vital importance. Comparison between theory and experiment shows that shell model calculations of the isospin mixing probability deviate by a factor three to seven from experiment. For more recent Hartree-Fock-RPA based calculations the difference is over two orders of magnitude.

  14. Ground State Solutions for a Class of Fractional Differential Equations with Dirichlet Boundary Value Condition

    Directory of Open Access Journals (Sweden)

    Zhigang Hu

    2014-01-01

    Full Text Available In this paper, we apply the method of the Nehari manifold to study the fractional differential equation (d/dt((1/2 0Dt-β(u′(t+(1/2 tDT-β(u′(t=  f(t,u(t, a.e. t∈[0,T], and u0=uT=0, where  0Dt-β, tDT-β are the left and right Riemann-Liouville fractional integrals of order 0≤β<1, respectively. We prove the existence of a ground state solution of the boundary value problem.

  15. Ground-state properties of trapped Bose-Fermi mixtures: Role of exchange correlation

    International Nuclear Information System (INIS)

    Albus, Alexander P.; Wilkens, Martin; Illuminati, Fabrizio

    2003-01-01

    We introduce density-functional theory for inhomogeneous Bose-Fermi mixtures, derive the associated Kohn-Sham equations, and determine the exchange-correlation energy in local-density approximation. We solve numerically the Kohn-Sham system, and determine the boson and fermion density distributions and the ground-state energy of a trapped, dilute mixture beyond mean-field approximation. The importance of the corrections due to exchange correlation is discussed by a comparison with current experiments; in particular, we investigate the effect of the repulsive potential-energy contribution due to exchange correlation on the stability of the mixture against collapse

  16. Composite model approach to the 2He4 nucleus ground state

    International Nuclear Information System (INIS)

    Mehrotra, I.; Agarwal, B.K.

    1986-12-01

    Assuming that the nucleons are (πμ) composite systems the helium nucleus is compared to a molecule consisting of four hydrogen-like atoms where pions are like nuclei and muons are like electrons. Ground state energy of 2 He 4 nucleus has been estimated in the framework of valence-bond method. Good agreement with the experimental value can be obtained if it is assumed that μ + μ - coupling is 3% stronger than the μ ± μ ± coupling. (author). 11 refs, 1 tab

  17. Relativistic Quadrupole Polarizability for the Ground State of Hydrogen-Like Ions

    International Nuclear Information System (INIS)

    Zhang Yong-Hu; Zhang Xian-Zhou; Tang Li-Yan; Shi Ting-Yun; Mitroy Jim

    2012-01-01

    The static quadrupole polarizabilities for hydrogen-like ions from Z = 1 to Z = 100 in the 1S 1/2 ground state are calculated to high precision by solving the Dirac equation using the B-spline Galerkin method. The results are consistent with the expression of Kaneko [J. Phys. B 10 (1977) 3347] at low Z. The quadrupole oscillator strength sum Σ n f (2) gn is computed to be zero to a very high degree of precision. (atomic and molecular physics)

  18. Existence of a ground state for the confined hydrogen atom in non-relativistic QED

    International Nuclear Information System (INIS)

    Amour, Laurent; Faupin, Jeremy

    2008-01-01

    We consider a system of a hydrogen atom interacting with the quantized electromagnetic field. Instead of fixing the nucleus, we assume that the system is confined by its center of mass. This model is used in theoretical physics to explain the Lamb-Dicke effect. After a brief review of the literature, we explain how to verify some properly chosen binding conditions which lead to the existence of a ground state for our model, and for all values of the fine-structure constant

  19. Ground-state properties of a dilute homogeneous Bose gas of hard disks in two dimensions

    International Nuclear Information System (INIS)

    Mazzanti, F.; Polls, A.; Fabrocini, A.

    2005-01-01

    The energy and structure of a dilute hard-disks Bose gas are studied in the framework of a variational many-body approach based on a Jastrow correlated ground-state wave function. The asymptotic behaviors of the radial distribution function and the one-body density matrix are analyzed after solving the Euler equation obtained by a free minimization of the hypernetted chain energy functional. Our results show important deviations from those of the available low density expansions, already at gas parameter values x∼0.001. The condensate fraction in 2D is also computed and found generally lower than the 3D one at the same x

  20. Topological Invariants and Ground-State Wave functions of Topological Insulators on a Torus

    Directory of Open Access Journals (Sweden)

    Zhong Wang

    2014-01-01

    Full Text Available We define topological invariants in terms of the ground-state wave functions on a torus. This approach leads to precisely defined formulas for the Hall conductance in four dimensions and the topological magnetoelectric θ term in three dimensions, and their generalizations in higher dimensions. They are valid in the presence of arbitrary many-body interactions and disorder. These topological invariants systematically generalize the two-dimensional Niu-Thouless-Wu formula and will be useful in numerical calculations of disordered topological insulators and strongly correlated topological insulators, especially fractional topological insulators.

  1. Resonant Ion Pair Formation in Electron Collisions with Ground State Molecular Ions

    International Nuclear Information System (INIS)

    Zong, W.; Dunn, G.H.; Djuric, N.; Greene, C.H.; Neau, A.; Zong, W.; Larsson, M.; Al-Khalili, A.; Neau, A.; Derkatch, A.M.; Vikor, L.; Shi, W.; Rosen, S.; Le Padellec, A.; Danared, H.; Ugglas, M. af

    1999-01-01

    Resonant ion pair formation from collisions of electrons with ground state diatomic molecular ions has been observed and absolute cross sections measured. The cross section for HD + is characterized by an abrupt threshold at 1.9thinspthinspeV and 14 resolved peaks in the range of energies 0≤E≤14 eV . The dominant mechanism responsible for the structures appears to be resonant capture and stabilization, modified by two-channel quantum interference. Data on HF + show structure correlated with photoionization of HF and with dissociative recombination of electrons with this ion. copyright 1999 The American Physical Society

  2. Light-cone distribution amplitudes of the ground state bottom baryons in HQET

    Energy Technology Data Exchange (ETDEWEB)

    Ali, A.; Wang, W. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hambrock, C. [Technische Univ. Dortmund (Germany); Parkhomenko, A.Ya. [P.G. Demidov Yaroslavl State Univ., Yaroslavl (Russian Federation)

    2012-12-15

    We provide the definition of the complete set of light-cone distribution amplitudes (LCDAs) for the ground state heavy bottom baryons with the spin-parities J{sup P}=1/2{sup +} and J{sup P}=3/2{sup +} in the heavy quark limit. We present the renormalization effects on the twist-2 light-cone distribution amplitudes and use the QCD sum rules to compute the moments of twist-2, twist-3, and twist-4 LCDAs. Simple models for the heavy baryon distribution amplitudes are analyzed with account of their scale dependence.

  3. The ground state energy of a bound polaron in the presence of a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zorkani, I [International Centre for Theoretical Physics, Trieste (Italy); Belhissi, R [Faculte des Sciences Dhar Mahraz, Fes (Morocco). Dept. de Physique

    1995-09-01

    A theoretical calculation for the ground state energy of a bound polaron as a function of the magnetic field is presented. The theory is based on a variational approach using a trial wave function proposed by Devreese et al. in the absence of the magnetic field. It was shown that his function is adequate for all electron - phonon coupling {alpha} and all parameter {gamma}{sub 0} which is the ratio between the L.O. phonon energy and the Colombian one. Analytical results are obtained in the weak coupling limit. (author). 27 refs, 4 figs, 1 tab.

  4. Positive ground state solutions to Schrodinger-Poisson systems with a negative non-local term

    Directory of Open Access Journals (Sweden)

    Yan-Ping Gao

    2015-04-01

    Full Text Available In this article, we study the Schrodinger-Poisson system $$\\displaylines{ -\\Delta u+u-\\lambda K(x\\phi(xu=a(x|u|^{p-1}u, \\quad x\\in\\mathbb{R}^3, \\cr -\\Delta\\phi=K(xu^{2},\\quad x\\in\\mathbb{R}^3, }$$ with $p\\in(1,5$. Assume that $a:\\mathbb{R}^3\\to \\mathbb{R^{+}}$ and $K:\\mathbb{R}^3\\to \\mathbb{R^{+}}$ are nonnegative functions and satisfy suitable assumptions, but not requiring any symmetry property on them, we prove the existence of a positive ground state solution resolved by the variational methods.

  5. Simulations of ground state fluctuations in mean-field Ising spin glasses

    International Nuclear Information System (INIS)

    Boettcher, Stefan

    2010-01-01

    The scaling of fluctuations in the distribution of ground state energies or costs with the system size N for Ising spin glasses is considered using an extensive set of simulations with the extremal optimization heuristic across a range of different models on sparse and dense graphs. These models exhibit very diverse behaviors, and an asymptotic extrapolation is often complicated by higher-order corrections in size. The clearest picture, in fact, emerges from the study of graph bipartitioning, a combinatorial optimization problem closely related to spin glasses. Asides from two-spin interactions with discrete bonds, we also consider problems with Gaussian bonds and three-spin interactions, which behave quite differently

  6. Ground state solutions for Choquard type equations with a singular potential

    Directory of Open Access Journals (Sweden)

    Tao Wang

    2017-02-01

    Full Text Available This article concerns the Choquard type equation $$ -\\Delta u+V(xu=\\Big(\\int_{\\mathbb{R}^N}\\frac{|u(y|^p}{|x-y|^{N-\\alpha}}dy\\Big |u|^{p-2}u,\\quad x\\in \\mathbb{R}^N, $$ where $N\\geq3$, $\\alpha\\in ((N-4_+,N$, $2\\leq p <(N+\\alpha/(N-2$ and V(x is a possibly singular potential and may be unbounded below. Applying a variant of the Lions' concentration-compactness principle, we prove the existence of ground state solution of the above equations.

  7. Ground-State Band and Deformation of the Z = 102 Isotope N 254

    International Nuclear Information System (INIS)

    Reiter, P.; Khoo, T.L.; Lister, C.J.; Seweryniak, D.; Ahmad, I.; Alcorta, M.; Carpenter, M.P.; Cizewski, J.A.; Davids, C.N.; Gervais, G.; Greene, J.P.; Henning, W.F.; Janssens, R.V.; Lauritsen, T.; Siem, S.; Sonzogni, A.A.; Sullivan, D.; Uusitalo, J.; Wiedenhoever, I.; Amzal, N.; Butler, P.A.; Chewter, A.J.; Greenlees, P.T.; Herzberg, R.; Jones, G.D.; Cizewski, J.A.; Ding, K.Y.; Fotiades, N.; Fox, J.D.; Korten, W.; Leino, M.; Vetter, K.; Siem, S.

    1999-01-01

    The ground-state band of the Z=102 isotope 254 No has been identified up to spin 14, indicating that the nucleus is deformed. The deduced quadrupole deformation, β=0.27 , is in agreement with theoretical predictions. These observations confirm that the shell-correction energy responsible for the stability of transfermium nuclei is partly derived from deformation. The survival of 254 No up to spin 14 means that its fission barrier persists at least up to that spin. copyright 1999 The American Physical Society

  8. Fast Ground State Manipulation of Neutral Atoms in Microscopic Optical Traps

    International Nuclear Information System (INIS)

    Yavuz, D.D.; Kulatunga, P.B.; Urban, E.; Johnson, T.A.; Proite, N.; Henage, T.; Walker, T.G.; Saffman, M.

    2006-01-01

    We demonstrate Rabi flopping at MHz rates between ground hyperfine states of neutral 87 Rb atoms that are trapped in two micron sized optical traps. Using tightly focused laser beams we demonstrate high fidelity, site specific Rabi rotations with cross talk on neighboring sites separated by 8 μm at the level of 10 -3 . Ramsey spectroscopy is used to measure a dephasing time of 870 μs, which is ≅5000 times longer than the time for a π/2 pulse

  9. Ground States of Ultracold Spin-1 Atoms in a Deep Double-Well Optical Superlattice in a Weak Magnetic Field

    International Nuclear Information System (INIS)

    Zheng Gong-Ping; Qin Shuai-Feng; Wang Shou-Yang; Jian Wen-Tian

    2013-01-01

    The ground states of the ultracold spin-1 atoms trapped in a deep one-dimensional double-well optical superlattice in a weak magnetic field are obtained. It is shown that the ground-state diagrams of the reduced double-well model are remarkably different for the antiferromagnetic and ferromagnetic condensates. The transition between the singlet state and nematic state is observed for the antiferromagnetic interaction atoms, which can be realized by modulating the tunneling parameter or the quadratic Zeeman energy. An experiment to distinguish the different spin states is suggested. (general)

  10. Correlations of zero-entropy critical states in the XXZ model: integrability and Luttinger theory far from the ground state

    Directory of Open Access Journals (Sweden)

    R. Vlijm, I. S. Eliëns, J. -S. Caux

    2016-10-01

    Full Text Available Pumping a finite energy density into a quantum system typically leads to `melted' states characterized by exponentially-decaying correlations, as is the case for finite-temperature equilibrium situations. An important exception to this rule are states which, while being at high energy, maintain a low entropy. Such states can interestingly still display features of quantum criticality, especially in one dimension. Here, we consider high-energy states in anisotropic Heisenberg quantum spin chains obtained by splitting the ground state's magnon Fermi sea into separate pieces. Using methods based on integrability, we provide a detailed study of static and dynamical spin-spin correlations. These carry distinctive signatures of the Fermi sea splittings, which would be observable in eventual experimental realizations. Going further, we employ a multi-component Tomonaga-Luttinger model in order to predict the asymptotics of static correlations. For this effective field theory, we fix all universal exponents from energetics, and all non-universal correlation prefactors using finite-size scaling of matrix elements. The correlations obtained directly from integrability and those emerging from the Luttinger field theory description are shown to be in extremely good correspondence, as expected, for the large distance asymptotics, but surprisingly also for the short distance behavior. Finally, we discuss the description of dynamical correlations from a mobile impurity model, and clarify the relation of the effective field theory parameters to the Bethe Ansatz solution.

  11. Exact ground-state phase diagrams for the spin-3/2 Blume-Emery-Griffiths model

    Energy Technology Data Exchange (ETDEWEB)

    Canko, Osman; Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Deviren, Bayram [Institute of Science, Erciyes University, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr

    2008-05-15

    We have calculated the exact ground-state phase diagrams of the spin-3/2 Ising model using the method that was proposed and applied to the spin-1 Ising model by Dublenych (2005 Phys. Rev. B 71 012411). The calculated, exact ground-state phase diagrams on the diatomic and triangular lattices with the nearest-neighbor (NN) interaction have been presented in this paper. We have obtained seven and 15 topologically different ground-state phase diagrams for J>0 and J<0, respectively, on the diatomic lattice and have found the conditions for the existence of uniform and intermediate or non-uniform phases. We have also constructed the exact ground-state phase diagrams of the model on the triangular lattice and found 20 and 59 fundamental phase diagrams for J>0 and J<0, respectively, the conditions for the existence of uniform and intermediate phases have also been found.

  12. Accurate Ground-State Energies of Solids and Molecules from Time-Dependent Density-Functional Theory

    DEFF Research Database (Denmark)

    Olsen, Thomas; Thygesen, Kristian Sommer

    2014-01-01

    We demonstrate that ground-state energies approaching chemical accuracy can be obtained by combining the adiabatic-connection fluctuation-dissipation theorem with time-dependent densityfunctional theory. The key ingredient is a renormalization scheme, which eliminates the divergence...

  13. State-to-state quantum dynamics of the F + HCl (vi = 0, ji = 0) → HF(vf, jf) + Cl reaction on the ground state potential energy surface.

    Science.gov (United States)

    Li, Anyang; Guo, Hua; Sun, Zhigang; Kłos, Jacek; Alexander, Millard H

    2013-10-07

    The state-to-state reaction dynamics of the title reaction is investigated on the ground electronic state potential energy surface using two quantum dynamical methods. The results obtained using the Chebyshev real wave packet method are in excellent agreement with those obtained using the time-independent method, except at low translational energies. It is shown that this exothermic hydrogen abstraction reaction is direct, resulting in a strong back-scattered bias in the product angular distribution. The HF product is highly excited internally. Agreement with available experimental data is only qualitative. We discuss several possible causes of disagreement with experiment.

  14. Calculation of the ground and excited states of the Ne2 molecule by the variational cellular method

    International Nuclear Information System (INIS)

    Dias, A.M.; Rosato, A.

    1981-07-01

    The potential curves for the ground state 1 Σ + sub(g) and for the first singlet excited state 1 Σ + sub (u) of the Ne 2 molecule are determined by the Variational Cellular Method. From these curves some spectroscopical constants are obtained. Ionization energies of the excited state 1 Σ + sub (u) are calculated. (Author) [pt

  15. Rich Ground State Chemical Ordering in Nanoparticles: Exact Solution of a Model for Ag-Au Clusters

    DEFF Research Database (Denmark)

    Larsen, Peter Mahler; Jacobsen, Karsten Wedel; Schiøtz, Jakob

    2018-01-01

    We show that nanoparticles can have very rich ground state chemical order. This is illustrated by determining the chemical ordering of Ag-Au 309-atom Mackay icosahedral nanoparticles. The energy of the nanoparticles is described using a cluster expansion model, and a Mixed Integer Programming (MIP......) approach is used to find the exact ground state configurations for all stoichiometries. The chemical ordering varies widely between the different stoichiometries, and display a rich zoo of structures with non-trivial ordering....

  16. Convergence of Ground and Excited State Properties of Divacancy Defects in 4H-SiC with Computational Cell Size

    Science.gov (United States)

    2018-03-01

    SiC with Computational Cell Size by Ariana Beste and DeCarlos E Taylor Approved for public release; distribution is unlimited...Laboratory Convergence of Ground and Excited State Properties of Divacancy Defects in 4H-SiC with Computational Cell Size by Ariana Beste...Ground and Excited State Properties of Divacancy Defects in 4H-SiC with Computational Cell Size 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM

  17. State-selective electron capture in collisions of ground and metastable O2+ ions with H(1s)

    International Nuclear Information System (INIS)

    Cabello, C N; Errea, L F; Fernandez, L; Mendez, L; Macias, A; Rabadan, I; Riera, A

    2003-01-01

    An ab initio calculation of the electron capture cross sections for collisions of ground and metastable states of O 2+ with H(1s) is presented. For impact energies between 0.125 and 3.4 keV amu -1 , we find good agreement between the cross sections from the ground state ion with the mixed beam experimental data of Phaneuf et al (Phaneuf A, Alvarez I, Meyer F W and Crandall D H 1982 Phys. Rev. A 26 1892)

  18. Zethrenes, Extended p -Quinodimethanes, and Periacenes with a Singlet Biradical Ground State

    KAUST Repository

    Sun, Zhe

    2014-08-19

    ConspectusResearchers have studied polycyclic aromatic hydrocarbons (PAHs) for more than 100 years, and most PAHs in the neutral state reported so far have a closed-shell electronic configuration in the ground state. However, recent studies have revealed that specific types of polycyclic hydrocarbons (PHs) could have a singlet biradical ground state and exhibit unique electronic, optical, and magnetic activities. With the appropriate stabilization, these new compounds could prove useful as molecular materials for organic electronics, nonlinear optics, organic spintronics, organic photovoltaics, and energy storage devices. However, before researchers can use these materials to design new devices, they need better methods to synthesize these molecules and a better understanding of the fundamental relationship between the structure and biradical character of these compounds and their physical properties. Their biradical character makes these compounds difficult to synthesize. These compounds are also challenging to physically characterize and require the use of various experimental techniques and theoretic methods to comprehensively describe their unique properties.In this Account, we will discuss the chemistry and physics of three types of PHs with a significant singlet biradical character, primarily developed in our group. These structures are zethrenes, Z-shaped quinoidal hydrocarbons; hydrocarbons that include a proaromatic extended p-quinodimethane unit; and periacenes, acenes fused in a peri-Arrangement. We used a variety of synthetic methods to prepare these compounds and stabilized them using both thermodynamic and kinetic approaches. We probed their ground-state structures by electronic absorption, NMR, ESR, SQUID, Raman spectroscopy, and X-ray crystallography and also performed density functional theory calculations. We investigated the physical properties of these PHs using various experimental methods such as one-photon absorption, two-photon absorption

  19. Systematics of ground state multiplets of atomic nuclei in the delta-interaction approach

    Energy Technology Data Exchange (ETDEWEB)

    Imasheva, L. T.; Ishkhanov, B. S.; Stepanov, M. E., E-mail: stepanov@depni.sinp.msu.ru [Moscow State University, Faculty of Physics (Russian Federation); Tretyakova, T. Yu. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)

    2015-12-15

    Pairing forces between nucleons in an atomic nucleus strongly influence its structure. One of the manifestations of pair interaction is the ground state multiplet (GSM) formation in the spectrum of low-lying excited states of even–even nuclei. The value of GSM splitting is determined by the value of pair interaction of nucleons; for each isotope, it can be estimated on the basis of experimental nuclear masses. The quality of this estimate is characterized by the degree of reproduction of GSM levels in the nucleus. The GSM systematics in even–even nuclei with a pair of identical nucleons in addition to the filled nuclear core is considered on the basis of delta interaction.

  20. A comparative icMRCI study of some NO+, NO and NO- electronic ground state properties

    International Nuclear Information System (INIS)

    Polak, R.; Fiser, J.

    2004-01-01

    Potential energy, electric field gradient (EFG) at both nuclei, and electric dipole moment functions for the electronic ground states of NO + , NO and NO - were calculated at the internally contracted multireference configuration interaction (icMRCI) level using augmented correlation-consistent basis sets. The changes in the EFG's with internuclear separation R were used to interpret the character of bonding in the triad of NO species. The vibrational dependences of the electric properties were estimated and the EFG's were employed to determine the 14 N nuclear quadrupole coupling constants. The effects of the choice of the basis set and reference configuration space were investigated. While the results obtained for NO + and NO served primarily to assess the quality of calculations by comparison with available experimental and theoretical data, new information was obtained on NO - , including electric property functions and some notions about the existence of metastable states

  1. Electronic and structural ground state of heavy alkali metals at high pressure

    Science.gov (United States)

    Fabbris, G.; Lim, J.; Veiga, L. S. I.; Haskel, D.; Schilling, J. S.

    2015-02-01

    Alkali metals display unexpected properties at high pressure, including emergence of low-symmetry crystal structures, which appear to occur due to enhanced electronic correlations among the otherwise nearly free conduction electrons. We investigate the high-pressure electronic and structural ground state of K, Rb, and Cs using x-ray absorption spectroscopy and x-ray diffraction measurements together with a b i n i t i o theoretical calculations. The sequence of phase transitions under pressure observed at low temperature is similar in all three heavy alkalis except for the absence of the o C 84 phase in Cs. Both the experimental and theoretical results point to pressure-enhanced localization of the valence electrons characterized by pseudogap formation near the Fermi level and strong s p d hybridization. Although the crystal structures predicted to host magnetic order in K are not observed, the localization process appears to drive these alkalis closer to a strongly correlated electron state.

  2. Effects of ground state correlations on the structure of odd-mass spherical nuclei

    International Nuclear Information System (INIS)

    Mishev, S.; Voronov, V. V.

    2008-01-01

    It is well known that the Pauli principle plays a substantial role at low energies because the quasiparticle and phonon operators, used to describe them, are built of fermions and as a consequence they are not ideal bosons. The correct treatment of this problem requires calculation of the exact commutators between the quasiparticle and phonon operators and in this way to take into account the Pauli principle corrections. In addition to the correlations due to the quasiparticle interaction in the ground-state influence the single-particle fragmentation as well. In this article, we generalize the basic equations of the quasiparticle-phonon nuclear model to account for both effects mentioned above. As an illustration of our approach, calculations of the structure of the low-lying states in the odd-mass nuclei 131-137 Ba have been performed

  3. Ground state and elementary excitations of a model valence-fluctuation system

    International Nuclear Information System (INIS)

    Brandow, B.H.

    1979-01-01

    The nature of the valence fluctuation problem is described, and motivations are given for an Anderson-lattice model Hamiltonian. A simple trial wave function is posed for the ground state, and the variational problem is solved. This demonstrates clearly that there is no Kondo-like divergence; the present concentrated Kondo problem is thus more simple mathematically than the sngle-impurity problem. Elementary excitations are studies by the Green's function techniques of Zubarev and Hubbard. Quenching of local moments and a large specific heat are found at low temperatures. The quasi-particle spectrum exhibits a gap, but epsilon/sub F/ does not lie in this gap. The insulation-like feature of SmB 6 , SmS, and TmSe at very low temperatures is explained in terms of a strongly reduced mobility for states near the gap, and reasons are given why this feature is not observed in other valence-fluctuation compounds. 73 references

  4. Does the ground-state resonance of 10Li overlap neutron threshold

    International Nuclear Information System (INIS)

    McVoy, K.W.; Van Isacker, P.

    1994-01-01

    Recent measurements suggest that the ground state of 10 Li is a resonance which may well be wide enough to overlap the (n + 9 Li) threshold. In this context we recall some of the curious properties of resonances located near threshold and entered from a non-decay channel, including their asymmetry and the fact that the peak observed in the cross section occurs at neither the R-matrix nor the S-matrix energy, but rather between the two. Because of these and other complications, it does not seem likely that either the l-value of the resonance or the energy of the corresponding state can accurately be determined form the shape of the resonance peak alone. (authors). 5 refs., 4 figs., 2 tabs

  5. Carboxamide Spleen Tyrosine Kinase (Syk) Inhibitors: Leveraging Ground State Interactions To Accelerate Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, J. Michael; Altman, Michael D.; Cash, Brandon; Haidle, Andrew M.; Kubiak, Rachel L.; Maddess, Matthew L.; Yan, Youwei; Northrup, Alan B. (Merck)

    2016-12-08

    Optimization of a series of highly potent and kinome selective carbon-linked carboxamide spleen tyrosine kinase (Syk) inhibitors with favorable drug-like properties is described. A pervasive Ames liability in an analogous nitrogen-linked carboxamide series was obviated by replacement with a carbon-linked moiety. Initial efforts lacked on-target potency, likely due to strain induced between the hinge binding amide and solvent front heterocycle. Consideration of ground state and bound state energetics allowed rapid realization of improved solvent front substituents affording subnanomolar Syk potency and high kinome selectivity. These molecules were also devoid of mutagenicity risk as assessed via the Ames test using the TA97a Salmonella strain.

  6. Dynamic Electron Correlation Effects on the Ground State Potential Energy Surface of a Retinal Chromophore Model.

    Science.gov (United States)

    Gozem, Samer; Huntress, Mark; Schapiro, Igor; Lindh, Roland; Granovsky, Alexander A; Angeli, Celestino; Olivucci, Massimo

    2012-11-13

    The ground state potential energy surface of the retinal chromophore of visual pigments (e.g., bovine rhodopsin) features a low-lying conical intersection surrounded by regions with variable charge-transfer and diradical electronic structures. This implies that dynamic electron correlation may have a large effect on the shape of the force fields driving its reactivity. To investigate this effect, we focus on mapping the potential energy for three paths located along the ground state CASSCF potential energy surface of the penta-2,4-dieniminium cation taken as a minimal model of the retinal chromophore. The first path spans the bond length alternation coordinate and intercepts a conical intersection point. The other two are minimum energy paths along two distinct but kinetically competitive thermal isomerization coordinates. We show that the effect of introducing the missing dynamic electron correlation variationally (with MRCISD) and perturbatively (with the CASPT2, NEVPT2, and XMCQDPT2 methods) leads, invariably, to a stabilization of the regions with charge transfer character and to a significant reshaping of the reference CASSCF potential energy surface and suggesting a change in the dominating isomerization mechanism. The possible impact of such a correction on the photoisomerization of the retinal chromophore is discussed.

  7. Ground-state and dynamical properties of two-dimensional dipolar Fermi liquids

    International Nuclear Information System (INIS)

    Abedinpour, Saeed H.; Asgari, Reza; Tanatar, B.; Polini, Marco

    2014-01-01

    We study the ground-state properties of a two-dimensional spin-polarized fluid of dipolar fermions within the Euler–Lagrange Fermi-hypernetted-chain approximation. Our method is based on the solution of a scattering Schrödinger equation for the “pair amplitude” √(g(r)), where g(r) is the pair distribution function. A key ingredient in our theory is the effective pair potential, which includes a bosonic term from Jastrow–Feenberg correlations and a fermionic contribution from kinetic energy and exchange, which is tailored to reproduce the Hartree–Fock limit at weak coupling. Very good agreement with recent results based on quantum Monte Carlo simulations is achieved over a wide range of coupling constants up to the liquid-to-crystal quantum phase transition. Using the fluctuation–dissipation theorem and a static approximation for the effective inter-particle interactions, we calculate the dynamical density–density response function, and furthermore demonstrate that an undamped zero-sound mode exists for any value of the interaction strength, down to infinitesimally weak couplings. -- Highlights: •We have studied the ground state properties of a strongly correlated two-dimensional fluid of dipolar fermions. •We have calculated the effective inter-particle interaction and the dynamical density–density response function. •We have shown that an undamped zero sound mode exists at any value of the interaction strength

  8. The use of quadratic forms in the calculation of ground state electronic structures

    International Nuclear Information System (INIS)

    Keller, Jaime; Weinberger, Peter

    2006-01-01

    There are many examples in theoretical physics where a fundamental quantity can be considered a quadratic form ρ=Σ i ρ i =vertical bar Ψ vertical bar 2 and the corresponding linear form Ψ=Σ i ψ i is highly relevant for the physical problem under study. This, in particular, is the case of the density and the wave function in quantum mechanics. In the study of N-identical-fermion systems we have the additional feature that Ψ is a function of the 3N configuration space coordinates and ρ is defined in three-dimensional real space. For many-electron systems in the ground state the wave function and the Hamiltonian are to be expressed in terms of the configuration space (CS), a replica of real space for each electron. Here we present a geometric formulation of the CS, of the wave function, of the density, and of the Hamiltonian to compute the electronic structure of the system. Then, using the new geometric notation and the indistinguishability and equivalence of the electrons, we obtain an alternative computational method for the ground state of the system. We present the method and discuss its usefulness and relation to other approaches

  9. Hartree–Fock many-body perturbation theory for nuclear ground-states

    Directory of Open Access Journals (Sweden)

    Alexander Tichai

    2016-05-01

    Full Text Available We investigate the order-by-order convergence behavior of many-body perturbation theory (MBPT as a simple and efficient tool to approximate the ground-state energy of closed-shell nuclei. To address the convergence properties directly, we explore perturbative corrections up to 30th order and highlight the role of the partitioning for convergence. The use of a simple Hartree–Fock solution for the unperturbed basis leads to a convergent MBPT series for soft interactions, in contrast to the divergent MBPT series obtained with a harmonic oscillator basis. For larger model spaces and heavier nuclei, where a direct high-order MBPT calculation is not feasible, we perform third-order calculations and compare to advanced ab initio coupled-cluster results for the same interactions and model spaces. We demonstrate that third-order MBPT provides ground-state energies for nuclei up into the tin isotopic chain in excellent agreement with the best available coupled-cluster calculations at a fraction of the computational cost.

  10. Hartree–Fock many-body perturbation theory for nuclear ground-states

    Energy Technology Data Exchange (ETDEWEB)

    Tichai, Alexander, E-mail: alexander.tichai@physik.tu-darmstadt.de [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany); Langhammer, Joachim [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany); Binder, Sven [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 (United States); Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Roth, Robert, E-mail: robert.roth@physik.tu-darmstadt.de [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany)

    2016-05-10

    We investigate the order-by-order convergence behavior of many-body perturbation theory (MBPT) as a simple and efficient tool to approximate the ground-state energy of closed-shell nuclei. To address the convergence properties directly, we explore perturbative corrections up to 30th order and highlight the role of the partitioning for convergence. The use of a simple Hartree–Fock solution for the unperturbed basis leads to a convergent MBPT series for soft interactions, in contrast to the divergent MBPT series obtained with a harmonic oscillator basis. For larger model spaces and heavier nuclei, where a direct high-order MBPT calculation is not feasible, we perform third-order calculations and compare to advanced ab initio coupled-cluster results for the same interactions and model spaces. We demonstrate that third-order MBPT provides ground-state energies for nuclei up into the tin isotopic chain in excellent agreement with the best available coupled-cluster calculations at a fraction of the computational cost.

  11. Electron pumping of the ground state of 21Ne. Transfers and multiple diffusion processes

    International Nuclear Information System (INIS)

    Stoeckel, F.; Lombardi, M.

    1978-01-01

    The electron-pumping process of the ground state of 21 Ne has been studied. It is demonstrated how in a neon cell at a pressure of 10 -4 to 10 -2 torr, a high frequency discharge can create a nuclear spin alignment in the fundamental level (I=3/2) when the excited levels are themselves aligned. The nuclear alignment is observed by monitoring the change of the linear polarization of several optical transitions during the magnetic resonance of the fundamental level. Various transfers of the alignments are investigated and a detailed study of the influence of the multiple diffusion is carried out. The multiple diffusion produces a depolarization and a relaxation of the nuclear spin. A theoretical calculation has been made for a two-level system with a J=1 radiative level and a J=0 ground state. Experimentally a relaxation time of the nuclear alignment varying from 37 ms to 240 ms is observed when the neon pressure decreases from 10 -2 to 10 -4 torr [fr

  12. Climate-driven ground-level ozone extreme in the fall over the Southeast United States.

    Science.gov (United States)

    Zhang, Yuzhong; Wang, Yuhang

    2016-09-06

    Ground-level ozone is adverse to human and vegetation health. High ground-level ozone concentrations usually occur over the United States in the summer, often referred to as the ozone season. However, observed monthly mean ozone concentrations in the southeastern United States were higher in October than July in 2010. The October ozone average in 2010 reached that of July in the past three decades (1980-2010). Our analysis shows that this extreme October ozone in 2010 over the Southeast is due in part to a dry and warm weather condition, which enhances photochemical production, air stagnation, and fire emissions. Observational evidence and modeling analysis also indicate that another significant contributor is enhanced emissions of biogenic isoprene, a major ozone precursor, from water-stressed plants under a dry and warm condition. The latter finding is corroborated by recent laboratory and field studies. This climate-induced biogenic control also explains the puzzling fact that the two extremes of high October ozone both occurred in the 2000s when anthropogenic emissions were lower than the 1980s and 1990s, in contrast to the observed decreasing trend of July ozone in the region. The occurrences of a drying and warming fall, projected by climate models, will likely lead to more active photochemistry, enhanced biogenic isoprene and fire emissions, an extension of the ozone season from summer to fall, and an increase of secondary organic aerosols in the Southeast, posing challenges to regional air quality management.

  13. The magnetic ground state and relationship to Kitaev physics in α-RuCl3

    Science.gov (United States)

    Banerjee, Arnab

    The 2D Kitaev candidate alpha-RuCl3 consists of stacked honeycomb layers weakly coupled by Van der Waals interactions. Here we report the measurements of bulk properties and neutron diffraction in both powder and single crystal samples. Our results show that the full three dimensional magnetic ground state is highly pliable with at least two dominant phases corresponding to two different out-of-plane magnetic orders. They have different Neel temperatures dependent on the stacking of the 2D layers, such as a broad magnetic transition at TN = 14 K as observed in phase-pure powder samples, or a sharp magnetic transition at a lower TN = 7 K as observed in homogeneous single crystals with no evidence for stacking faults. The magnetic refinements of the neutron scattering data will be discussed, which in all cases shows the in-plane magnetic ground state is the zigzag phase common in Kitaev related materials including the honeycomb lattice Iridates. Inelastic neutron scattering in all cases shows that this material consistently exhibit strong two-dimensional magnetic fluctuations leading to a break-down of the classical spin-wave picture. Work performed at ORNL is supported by U.S. Dept. of Energy, Office of Basic Energy Sciences and Office of User Facilities Division.

  14. Electron momentum spectroscopy of dimethyl ether taking account of nuclear dynamics in the electronic ground state

    International Nuclear Information System (INIS)

    Morini, Filippo; Deleuze, Michael Simon; Watanabe, Noboru; Kojima, Masataka; Takahashi, Masahiko

    2015-01-01

    The influence of nuclear dynamics in the electronic ground state on the (e,2e) momentum profiles of dimethyl ether has been analyzed using the harmonic analytical quantum mechanical and Born-Oppenheimer molecular dynamics approaches. In spite of fundamental methodological differences, results obtained with both approaches consistently demonstrate that molecular vibrations in the electronic ground state have a most appreciable influence on the momentum profiles associated to the 2b 1 , 6a 1 , 4b 2 , and 1a 2 orbitals. Taking this influence into account considerably improves the agreement between theoretical and newly obtained experimental momentum profiles, with improved statistical accuracy. Both approaches point out in particular the most appreciable role which is played by a few specific molecular vibrations of A 1 , B 1 , and B 2 symmetries, which correspond to C–H stretching and H–C–H bending modes. In line with the Herzberg-Teller principle, the influence of these molecular vibrations on the computed momentum profiles can be unraveled from considerations on the symmetry characteristics of orbitals and their energy spacing

  15. Quantum communication for satellite-to-ground networks with partially entangled states

    International Nuclear Information System (INIS)

    Chen Na; Quan Dong-Xiao; Pei Chang-Xing; Yang-Hong

    2015-01-01

    To realize practical wide-area quantum communication, a satellite-to-ground network with partially entangled states is developed in this paper. For efficiency and security reasons, the existing method of quantum communication in distributed wireless quantum networks with partially entangled states cannot be applied directly to the proposed quantum network. Based on this point, an efficient and secure quantum communication scheme with partially entangled states is presented. In our scheme, the source node performs teleportation only after an end-to-end entangled state has been established by entanglement swapping with partially entangled states. Thus, the security of quantum communication is guaranteed. The destination node recovers the transmitted quantum bit with the help of an auxiliary quantum bit and specially defined unitary matrices. Detailed calculations and simulation analyses show that the probability of successfully transferring a quantum bit in the presented scheme is high. In addition, the auxiliary quantum bit provides a heralded mechanism for successful communication. Based on the critical components that are presented in this article an efficient, secure, and practical wide-area quantum communication can be achieved. (paper)

  16. Towards long-term stable solid state electrolyzers with infiltrated catalysts

    DEFF Research Database (Denmark)

    Ovtar, Simona; Chen, Ming; Brodersen, Karen

    conventional power plants or fuel cells. Key challenges for a successful commercialization of solid oxide electrolyzers are up scale it, reduce cost and improve durability. Therefore, large efforts are allocated to improve cell performance. As a relatively novel method to introduce electro......Renewable energy sources like wind and solar are widely considered as the key technologies to cover our growing demands. However, the fluctuating nature of these sources requires a flexible energy system and storage technologies to ensure that energy supply can be covered in a stable and affordable......-catalysts into the porous structure of the electrodes, infiltration has shown very efficient. Solid oxide cells with infiltrated electrodes have been reported to show improved performance compared to conventional cells [1]. In this study, the development of infiltration procedures to improve the stability and catalytic...

  17. Lifetime measurements of the first 2+ states in 104,106Zr: Evolution of ground-state deformations

    Directory of Open Access Journals (Sweden)

    F. Browne

    2015-11-01

    Full Text Available The first fast-timing measurements from nuclides produced via the in-flight fission mechanism are reported. The lifetimes of the first 2+ states in 104,106Zr nuclei have been measured via β-delayed γ-ray timing of stopped radioactive isotope beams. An improved precision for the lifetime of the 21+ state in 104Zr was obtained, τ(21+=2.90−20+25 ns, as well as a first measurement of the 21+ state in 106Zr, τ(21+=2.60−15+20 ns, with corresponding reduced transition probabilities of B(E2;21+→0g.s.+=0.39(2 e2b2 and 0.31(1 e2b2, respectively. Comparisons of the extracted ground-state deformations, β2=0.39(1 (104Zr and β2=0.36(1 (106Zr with model calculations indicate a persistence of prolate deformation. The data show that 104Zr is the most deformed of the neutron-rich Zr isotopes measured so far.

  18. Transition of Facilities at Hanford to a Stable and Low Cost State

    International Nuclear Information System (INIS)

    BAILEY, R.W.

    2000-01-01

    This paper will discuss the implications of focusing on end states and interim end points in the deactivation planning process and managing the budget and personnel to achieve these end points as a ''project,'' not another phase of operations

  19. Top-down influences on ambiguous perception: the role of stable and transient states of the observer

    Science.gov (United States)

    Scocchia, Lisa; Valsecchi, Matteo; Triesch, Jochen

    2014-01-01

    The world as it appears to the viewer is the result of a complex process of inference performed by the brain. The validity of this apparently counter-intuitive assertion becomes evident whenever we face noisy, feeble or ambiguous visual stimulation: in these conditions, the state of the observer may play a decisive role in determining what is currently perceived. On this background, ambiguous perception and its amenability to top-down influences can be employed as an empirical paradigm to explore the principles of perception. Here we offer an overview of both classical and recent contributions on how stable and transient states of the observer can impact ambiguous perception. As to the influence of the stable states of the observer, we show that what is currently perceived can be influenced (1) by cognitive and affective aspects, such as meaning, prior knowledge, motivation, and emotional content and (2) by individual differences, such as gender, handedness, genetic inheritance, clinical conditions, and personality traits and by (3) learning and conditioning. As to the impact of transient states of the observer, we outline the effects of (4) attention and (5) voluntary control, which have attracted much empirical work along the history of ambiguous perception. In the huge literature on the topic we trace a difference between the observer's ability to control dominance (i.e., the maintenance of a specific percept in visual awareness) and reversal rate (i.e., the switching between two alternative percepts). Other transient states of the observer that have more recently drawn researchers' attention regard (6) the effects of imagery and visual working memory. (7) Furthermore, we describe the transient effects of prior history of perceptual dominance. (8) Finally, we address the currently available computational models of ambiguous perception and how they can take into account the crucial share played by the state of the observer in perceiving ambiguous displays. PMID

  20. Self-similarly evolving and minimally dissipated stable states of plasmas realized after relaxation and self-organization processes

    International Nuclear Information System (INIS)

    Kondoh, Yoshiomi; Hakoiwa, Toru; Okada, Akihito; Kobayashi, Naohiro; Takahashi, Toshiki

    2006-01-01

    A novel set of simultaneous eigenvalue equations having dissipative terms are derived to find self-similarly evolving and minimally dissipated stable states of plasmas realized after relaxation and self-organization processes. By numerically solving the set of eigenvalue equations in a cylindrical model, typical spatial profiles of plasma parameters, electric and magnetic fields and diffusion factors are presented, all of which determine self-consistently with each other by physical laws and mutual relations among them, just as in experimental plasmas. (author)

  1. Possibility of Q>5 stable, steady-state operation in ITER with moderate βN and H-factor

    International Nuclear Information System (INIS)

    Polevoi, A.R.; Mukhovatov, V.S.; Shimada, M.; Medvedev, S.Yu.; Ivanov, A.A.; Poshekhonov, Yu.Yu.; Pustovitov, V.D.; Chu, M.S.

    2003-01-01

    A possibility of steady state stable operation in ITER with Q>5 and moderate requirements for plasma confinement is investigated. It is shown that there is some parametrical space for such operation where the ideal kink modes could be stabilised by the first wall. It is found that operational space where the ideal kink modes can be stabilised by the conducting wall could be noticeably extended by a relatively small reduction of the pressure peaking factor. The resistive wall mode stabilisation in ITER is discussed. (author)

  2. Electron impact excitation cross sections and rates from the ground state of atomic calcium

    CERN Document Server

    Samson, A M

    2001-01-01

    New R-matrix calculations are presented for electron excitation of atomic calcium. The target state expansion includes 22 states: 4s sup 2 sup 1 S; 4snl sup 1 sup , sup 3 L, where nl is 3d, 4p, 5s, 5p, 4d and 4f; 3d4p sup 1 sup , sup 3 P,D,F; and 4p sup 2 sup 3 P, sup 1 D, sup 1 S terms. The calculation is in LS coupling, and configuration interaction involving 3p subshell correlation is included. Electron impact excitation cross sections from the 4s sup 2 ground state to the next 10 states are tabulated for low energies, and thermally averaged effective collision strengths are tabulated over a range of electron temperatures from 1000 to 10,000 K. Comparisons are made with previous cross sections calculations for the 4s sup 2 -4s4p sup 3 P deg. transition; excellent agreement is found with experimentally derived rates for 4s sup 2 -4s4p sup 1 P deg

  3. Scattering Properties of Ground-State 23Na Vapor Using Generalized Scattering Theory

    Science.gov (United States)

    Al-Harazneh, A. A.; Sandouqa, A. S.; Joudeh, B. R.; Ghassib, H. B.

    2018-04-01

    The scattering properties of ground-state 23Na vapor are investigated within the framework of the Galitskii-Migdal-Feynman formalism. Viewed as a generalized scattering theory, this formalism is used to calculate the medium phase shifts. The scattering properties of the system—the total, viscosity, spin-exchange, and average cross sections—are then computed using these phase shifts according to standard recipes. The total cross section is found to exhibit the Ramsauer-Townsend effect as well as resonance peaks. These peaks are caused by the large difference between the potentials for electronic spin-singlet and spin-triplet states. They represent quasi-bound states in the system. The results obtained for the complex spin-exchange cross sections are particularly highlighted because of their importance in the spectroscopy of the Na2 dimer. So are the results for the scattering lengths pertaining to both singlet and triplet states. Wherever possible, comparison is made with other published results.

  4. Properties of the {sup 7}He ground state from {sup 8}He neutron knockout

    Energy Technology Data Exchange (ETDEWEB)

    Aksyutina, Yu. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Fundamental Fysik, Chalmers Tekniska Hoegskola, S-412 96 Goeteborg (Sweden); Johansson, H.T. [Fundamental Fysik, Chalmers Tekniska Hoegskola, S-412 96 Goeteborg (Sweden); Aumann, T.; Boretzky, K. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Borge, M.J.G. [Instituto Estructura de la Materia, CSIC, E-28006 Madrid (Spain); Chatillon, A. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Chulkov, L.V. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Kurchatov Institute, RU-123182 Moscow (Russian Federation); Cortina-Gil, D. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); University of Santiago de Compostela, 15706 Santiago de Compostela (Spain); Pramanik, U. Datta [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Emling, H. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Forssen, C. [Fundamental Fysik, Chalmers Tekniska Hoegskola, S-412 96 Goeteborg (Sweden); Fynbo, H.O.U. [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark); Geissel, H.; Ickert, G. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Jonson, B. [Fundamental Fysik, Chalmers Tekniska Hoegskola, S-412 96 Goeteborg (Sweden)], E-mail: bjn@fy.chalmers.se; Kulessa, R. [Instytut Fizyki, Universytet Jagiellonski, PL-30-059 Krakow (Poland); Langer, C. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Lantz, M. [Fundamental Fysik, Chalmers Tekniska Hoegskola, S-412 96 Goeteborg (Sweden); LeBleis, T. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Lindahl, A.O. [Institutionen foer Fysik, University of Gothenburg, S-412 96 Goeteborg (Sweden)] (and others)

    2009-08-24

    The unbound nucleus {sup 7}He, produced in neutron-knockout reactions with a 240 MeV/u {sup 8}He beam in a liquid-hydrogen target, has been studied in an experiment at the ALADIN-LAND setup at GSI. From an R-matrix analysis the resonance parameters for {sup 7}He as well as the spectroscopic factor for the {sup 6}He(0{sup +}) + n configuration in its ground-state have been obtained. The spectroscopic factor is 0.61 confirming that {sup 7}He is not a pure single-particle state. An analysis of {sup 5}He data from neutron-knockout reactions of {sup 6}He in a carbon target reveals the presence of an s-wave component at low energies in the {alpha}+n relative energy spectrum. A possible low-lying exited state in {sup 7}He observed in neutron knockout data from {sup 8}He in a carbon target and tentatively interpreted as a I{sup {pi}}=1/2{sup -} state, could not be observed in the present experiment. Possible explanations of the shape difference between the {sup 7}He resonance obtained in the two knockout reactions are discussed in terms of target-dependence or different reaction mechanisms at relativistic energies.

  5. High-field magnetoconductance in La-Sr manganites of FM and AFM ground states

    Science.gov (United States)

    Jirák, Zdeněk; Kaman, Ondřej; Knížek, Karel; Levinský, Petr; Míšek, Martin; Veverka, Pavel; Hejtmánek, Jiří

    2018-06-01

    Large-grain La1-xSrxMnO3 ceramic samples of compositions x = 0.45 and 0.55, representing the ferromagnetic (FM) and A-type antiferromagnetic (AFM) ground states, were produced via classical sintering at 1500 °C of cold-pressed sol-gel prepared single-phase nanoparticles. Using the same precursors, nanogranular forms of both manganite ceramics were prepared by fast spark plasma sintering at low temperature of 900 °C, which limits the growth of crystal grains. The magnetotransport of both the bulk and nanogranular forms was investigated in a broad range of magnetic fields up to 130 kOe and analyzed on the basis of detailed magnetic measurements. Both the large-grain and nanogranular systems with x = 0.45, possessing a pure FM state with similar Curie tempereature TC ≈ 345 K), show nearly the same conductivity enhancement in external fields when expressed relatively to the zero-field values. This positive magnetoconductance (MC) can be separated into two terms: (i) the hysteretic low-field MC that reflects the field-induced orientation of magnetic moments of individual grains, and (ii) the high-field MC that depends linearly on external field. In the case of large-grain ceramics with x = 0.55, a partially ordered FM state formed below TC = 264 K is replaced by pure A-type AFM ground state below 204 K. This A-type AFM state is characterized by positive magnetoconductance that is essentially of quadratic dependence on external field in the investigated range up to 130 kOe. On contrary, the nanogranular product with x = 0.55 exhibits a mixed FM/AFM state at low temperatures, and, as a consequence, its magnetotransport combines the features of FM and A-type AFM systems, in which the quadratic term is much enhanced and clearly dominates at high fields. For interpretation of observed behaviors, the theory of grain-boundary tunneling is revisited.

  6. Hydrogen and oxygen stable isotope ratios of milk in the United States.

    Science.gov (United States)

    Chesson, Lesley A; Valenzuela, Luciano O; O'Grady, Shannon P; Cerling, Thure E; Ehleringer, James R

    2010-02-24

    Models of hydrogen and oxygen incorporation in human tissues recognize the impact of geographic location on the isotopic composition of fluid intake, but inputs can include nonlocal beverages, such as milk. Milk and cow drinking water were collected from dairies, and commercially available milk was purchased from supermarkets and fast food restaurants. It was hypothesized that milk water delta(2)H and delta(18)O values record geographic location information. Correlations between milk water isotope ratios and purchase location tap water were significant. However, the amount of variation in milk delta(2)H and delta(18)O values explained by tap water was low, suggesting a single estimation of fluid input isotope ratios may not always be adequate in studies. The delta(2)H and delta(18)O values of paired milk and cow drinking water were related, suggesting potential for geographical origin assignment using stable isotope analysis. As an application example, milk water delta(18)O values were used to predict possible regions of origin for restaurant samples.

  7. Decadal-scale changes of pesticides in ground water of the United States, 1993-2003

    Science.gov (United States)

    Bexfield, L.M.

    2008-01-01

    Pesticide data for ground water sampled across the United States between 1993-1995 and 2001-2003 by the U.S. Geological Survey National Water-Quality Assessment Program were evaluated for trends in detection frequency and concentration. The data analysis evaluated samples collected from a total of 362 wells located in 12 local well networks characterizing shallow ground water in agricultural areas and six local well networks characterizing the drinking water resource in areas of variable land use. Each well network was sampled once during 1993-1995 and once during 2001-2003. The networks provide an overview of conditions across a wide range of hydrogeologic settings and in major agricultural areas that vary in dominant crop type and pesticide use. Of about 80 pesticide compounds analyzed, only six compounds were detected in ground water from at least 10 wells during both sampling events. These compounds were the triazine herbicides atrazine, simazine, and prometon; the acetanilide herbicide metolachlor; the urea herbicide tebuthiuron; and an atrazine degradate, deethylatrazine (DEA). Observed concentrations of these compounds generally were spikes. In wells yielding detectable concentrations of atrazine, DEA, and prometon, concentrations were significantly lower (?? = 0.1) in 2001-2003 than in 1993-1995, whereas detection frequency of these compounds did not change significantly. Trends in atrazine concentrations at shallow wells in agricultural areas were found to be consistent overall with recent atrazine use data. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

  8. Solid state magnetic field sensors for micro unattended ground networks using spin dependent tunneling

    Science.gov (United States)

    Tondra, Mark; Nordman, Catherine A.; Lange, Erik H.; Reed, Daniel; Jander, Albrect; Akou, Seraphin; Daughton, James

    2001-09-01

    Micro Unattended Ground Sensor Networks will likely employ magnetic sensors, primarily for discrimination of objects as opposed to initial detection. These magnetic sensors, then, must fit within very small cost, size, and power budgets to be compatible with the envisioned sensor suites. Also, a high degree of sensitivity is required to minimize the number of sensor cells required to survey a given area in the field. Solid state magnetoresistive sensors, with their low cost, small size, and ease of integration, are excellent candidates for these applications assuming that their power and sensitivity performance are acceptable. SDT devices have been fabricated into prototype magnetic field sensors suitable for use in micro unattended ground sensor networks. They are housed in tiny SOIC 8-pin packages and mounted on a circuit board with required voltage regulation, signal amplification and conditioning, and sensor control and communications functions. The best sensitivity results to date are 289 pT/rt. Hz at 1 Hz, and and 7 pT/rt. Hz at f > 10 kHz. Expected near term improvements in performance would bring these levels to approximately 10 pT/rt Hz at 1 Hz and approximately 1 pT/rt. Hz at > 1 kHz.

  9. Ground Motion Prediction Equations for the Central and Eastern United States

    Science.gov (United States)

    Seber, D.; Graizer, V.

    2015-12-01

    New ground motion prediction equations (GMPE) G15 model for the Central and Eastern United States (CEUS) is presented. It is based on the modular filter based approach developed by Graizer and Kalkan (2007, 2009) for active tectonic environment in the Western US (WUS). The G15 model is based on the NGA-East database for the horizontal peak ground acceleration and 5%-damped pseudo spectral acceleration RotD50 component (Goulet et al., 2014). In contrast to active tectonic environment the database for the CEUS is not sufficient for creating purely empirical GMPE covering the range of magnitudes and distances required for seismic hazard assessments. Recordings in NGA-East database are sparse and cover mostly range of Mindustry (Vs=2800 m/s). The number of model predictors is limited to a few measurable parameters: moment magnitude M, closest distance to fault rupture plane R, average shear-wave velocity in the upper 30 m of the geological profile VS30, and anelastic attenuation factor Q0. Incorporating anelastic attenuation Q0 as an input parameter allows adjustments based on the regional crustal properties. The model covers the range of magnitudes 4.010 Hz) and is within the range of other models for frequencies lower than 2.5 Hz

  10. Characterising flow regime and interrelation between surface-water and ground-water in the Fuente de Piedra salt lake basin by means of stable isotopes, hydrogeochemical and hydraulic data

    Science.gov (United States)

    Kohfahl, Claus; Rodriguez, Miguel; Fenk, Cord; Menz, Christian; Benavente, Jose; Hubberten, Hans; Meyer, Hanno; Paul, Liisa; Knappe, Andrea; López-Geta, Juan Antonio; Pekdeger, Asaf

    2008-03-01

    SummaryThis research reports the characterisation of ground- and surface-water interaction in the Fuente de Piedra Salt lake basin in southern Spain by a combined approach using hydraulic, hydrogeochemical and stable isotope data. During three sampling campaigns (February 2004, 2005 and October 2005) ground- and surface-water samples were collected for stable isotope studies ( 18O, D) and for major and minor ion analysis. Hydraulic measurements at multilevel piezometers were carried out at four different locations around the lake edge. Conductivity logs were performed at four piezometers located along a profile at the northern lake border and at two deeper piezometers in the Miocene basin at a greater distance from the lake. To describe processes that control the brine evolution different hydrogeochemical simulations were performed. Hydrogeochemical data show a variety of brines related to thickness variations of lacustrine evaporites around the lake. Salinity profiles in combination with stable isotope and hydraulic data indicate the existence of convection cells and recycled brines. Furthermore restricted ground-water inflow into the lake was detected. Dedolomitisation processes were identified by hydrogeochemical simulations and different brine origins were reproduced by inverse modelling approaches.

  11. [The sanitary and hygienic state of solid garbage burial grounds in the stages of a life cycle].

    Science.gov (United States)

    Zomarev, A M; Vaĭsman, Ia I; Zaĭtseva, T A; Glushankova, I S

    2010-01-01

    The purpose of the study was to assess the sanitary-and-hygienic state of solid garbage (SG) burial grounds in the Perm Territory in different stage of a life cycle. This paper presents the results of the study of deposited waste, forming dump soil, and SG ground emissions by general sanitary and sanitary-microbiological parameters and their effect on environmental objects. The performed studies of the sanitary-and-hygienic situation on some grounds of the Perm Territory suggest that there is a need for setting up a system for sanitary-and-monitoring of SG ground and for elaborating engineering, organizational, and prophylactic measures to assure the sanitary-and-hygienic safety of objects and to control the quality and quantity of waste to be buried and the currents of emissions (ground body degassing, filtrating sewage drainage and purification).

  12. Analysis spectral shapes from California and central United States ground motion

    International Nuclear Information System (INIS)

    1994-01-01

    The objective of this study is to analyze the spectral shapes from earthquake records with magnitudes and distances comparable to those that dominate seismic hazard at Oak Ridge, in order to provide guidance for the selection of site-specific design-spectrum shapes for use in Oak Ridge. The authors rely heavily on California records because the number of relevant records from the central and eastern United States (CEUS) is not large enough for drawing statistically significant conclusions. They focus on the 0.5 to 10-Hz frequency range for two reasons: (1) this is the frequency range of most engineering interest, and (2) they avoid the effect of well-known differences in the high-frequency energy content between California and CEUS ground motions

  13. Classical ground states of Heisenberg and X Y antiferromagnets on the windmill lattice

    Science.gov (United States)

    Jeevanesan, Bhilahari; Orth, Peter P.

    2014-10-01

    We investigate the classical Heisenberg and planar (X Y ) spin models on the windmill lattice. The windmill lattice is formed out of two widely occurring lattice geometries: a triangular lattice is coupled to its dual honeycomb lattice. Using a combination of iterative minimization, heat-bath Monte Carlo simulations, and analytical calculations, we determine the complete ground-state phase diagram of both models and find the exact energies of the phases. The phase diagram shows a rich phenomenology due to competing interactions and hosts, in addition to collinear and various coplanar phases, also intricate noncoplanar phases. We briefly outline different paths to an experimental realization of these spin models. Our extensive study provides a starting point for the investigation of quantum and thermal fluctuation effects.

  14. Untangling complex networks: risk minimization in financial markets through accessible spin glass ground states.

    Science.gov (United States)

    Lisewski, Andreas Martin; Lichtarge, Olivier

    2010-08-15

    Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the relative margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network's Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.

  15. Nuclear level densities with pairing and self-consistent ground-state shell effects

    CERN Document Server

    Arnould, M

    1981-01-01

    Nuclear level density calculations are performed using a model of fermions interacting via the pairing force, and a realistic single particle potential. The pairing interaction is treated within the BCS approximation with different pairing strength values. The single particle potentials are derived in the framework of an energy-density formalism which describes self-consistently the ground states of spherical nuclei. These calculations are extended to statistically deformed nuclei, whose estimated level densities include rotational band contributions. The theoretical results are compared with various experimental data. In addition, the level densities for several nuclei far from stability are compared with the predictions of a back-shifted Fermi gas model. Such a comparison emphasizes the possible danger of extrapolating to unknown nuclei classical level density formulae whose parameter values are tailored for known nuclei. (41 refs).

  16. Ground state magnetization of conduction electrons in graphene with Zeeman effect

    Energy Technology Data Exchange (ETDEWEB)

    Escudero, F., E-mail: federico.escudero@uns.edu.ar [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Ardenghi, J.S., E-mail: jsardenhi@gmail.com [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Sourrouille, L., E-mail: lsourrouille@yahoo.es [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Jasen, P., E-mail: pvjasen@uns.edu.ar [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina)

    2017-05-01

    In this work we address the ground state magnetization in graphene, considering the Zeeman effect and taking into account the conduction electrons in the long wavelength approximation. We obtain analytical expressions for the magnetization at T=0 K, where the oscillations given by the de Haas van Alphen (dHvA) effect are present. We find that the Zeeman effect modifies the magnetization by introducing new peaks associated with the spin splitting of the Landau levels. These peaks are very small for typical carrier densities in graphene, but become more important for higher densities. The obtained results provide insight of the way in which the Zeeman effect modifies the magnetization, which can be useful to control and manipulate the spin degrees of freedom. - Highlights: • The magnetization has peaks whenever the last energy level changes discontinuously. • The peaks amplitude depends on the electron density. • The Zeeman effect introduces new peaks in the magnetization.

  17. Ground state depletion – A step towards mid-IR lasing of doped silver halides

    Energy Technology Data Exchange (ETDEWEB)

    Tsur, Yuval, E-mail: yuvaltsu@post.tau.ac.il [Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 6997801 (Israel); Goldring, Sharone [Applied Physics Division, Soreq NRC, Yavne 81800 (Israel); Galun, Ehud [DDR& D, Ministry of Defense (Israel); Katzir, Abraham [Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 6997801 (Israel)

    2016-07-15

    We show for the first time ground state absorption saturation in a doped silver halide crystal (AgCl{sub x}Br{sub 1−x}), specifically with cobalt. Spectroscopic studies showed absorption bands in the 1.4–2.5 μm region and emission bands in the 3.8–5.0 μm region, with a 1.5 ms lifetime at low temperatures. Absorption saturation indicates a good low and room temperature lasing feasibility at 4.1 μm. In addition, a comparison of cobalt, nickel and iron as dopants is presented. These doped silver halide crystals can be extruded to form optical fibers, possibly introducing a new family of fiber lasers for the middle infrared.

  18. Ground states of linear rotor chains via the density matrix renormalization group

    Science.gov (United States)

    Iouchtchenko, Dmitri; Roy, Pierre-Nicholas

    2018-04-01

    In recent years, experimental techniques have enabled the creation of ultracold optical lattices of molecules and endofullerene peapod nanomolecular assemblies. It was previously suggested that the rotor model resulting from the placement of dipolar linear rotors in one-dimensional lattices at low temperature has a transition between ordered and disordered phases. We use the density matrix renormalization group (DMRG) to compute ground states of chains of up to 100 rotors and provide further evidence of the phase transition in the form of a diverging entanglement entropy. We also propose two methods and present some first steps toward rotational spectra of such molecular assemblies using DMRG. The present work showcases the power of DMRG in this new context of interacting molecular rotors and opens the door to the study of fundamental questions regarding criticality in systems with continuous degrees of freedom.

  19. A Continuous Family of Equilibria in Ferromagnetic Media are Ground States

    Science.gov (United States)

    Su, Xifeng; de la Llave, Rafael

    2017-09-01

    We show that a foliation of equilibria (a continuous family of equilibria whose graph covers all the configuration space) in ferromagnetic transitive models are ground states. The result we prove is very general, and it applies to models with long range and many-body interactions. As an application, we consider several models of networks of interacting particles including models of Frenkel-Kontorova type on Z^d and one-dimensional quasi-periodic media. The result above is an analogue of several results in the calculus of variations (fields of extremals) and in PDE's. Since the models we consider are discrete and long range, new proofs need to be given. We also note that the main hypothesis of our result (the existence of foliations of equilibria) is the conclusion (using KAM theory) of several recent papers. Hence, we obtain that the KAM solutions recently established are minimizers when the interaction is ferromagnetic and transitive (these concepts are defined later).

  20. Orbital physics in sulfur spinels: ordered, liquid and glassy ground states

    International Nuclear Information System (INIS)

    Buettgen, N; Hemberger, J; Fritsch, V; Krimmel, A; Muecksch, M; Nidda, H-A Krug von; Lunkenheimer, P; Fichtl, R; Tsurkan, V; Loidl, A

    2004-01-01

    Measurements of magnetization M(T, H), heat capacity C(T), NMR lineshift K(T) and linewidth Δ(T), neutron scattering S(Q, ω, T) and broadband dielectric spectroscopy ε(ω, T) provide experimental evidence of the different orbital ground states in the cubic sulfur spinels under investigation. In all compounds, the tetrahedrally coordinated Jahn-Teller ions Fe 2+ are characterized by a degeneracy of the orbital degrees of freedom. Particularly, we found a long-range orbital ordering in polycrystalline (PC) FeCr 2 S 4 , and a glassy freezing of the orbital degrees of freedom in FeCr 2 S 4 (single crystals) (SCs). In contrast, FeSc 2 S 4 belongs to the rare class of spin-orbital liquids, where quantum fluctuations accompanying the glassy freezing of the orbitals suppress long-range magnetic order

  1. Uniqueness of non-linear ground states for fractional Laplacians in R

    DEFF Research Database (Denmark)

    Frank, Rupert L.; Lenzmann, Enno

    2013-01-01

    We prove uniqueness of ground state solutions Q = Q(|x|) ≥ 0 of the non-linear equation (−Δ)sQ+Q−Qα+1=0inR,where 0 fractional Laplacian in one dimension. In particular, we answer affirmatively an open question...... recently raised by Kenig–Martel–Robbiano and we generalize (by completely different techniques) the specific uniqueness result obtained by Amick and Toland for s=12 and α = 1 in [5] for the Benjamin–Ono equation. As a technical key result in this paper, we show that the associated linearized operator L...... + = (−Δ) s +1−(α+1)Q α is non-degenerate; i.e., its kernel satisfies ker L + = span{Q′}. This result about L + proves a spectral assumption, which plays a central role for the stability of solitary waves and blowup analysis for non-linear dispersive PDEs with fractional Laplacians, such as the generalized...

  2. Semiempirical Quantum-Chemical Orthogonalization-Corrected Methods: Benchmarks for Ground-State Properties.

    Science.gov (United States)

    Dral, Pavlo O; Wu, Xin; Spörkel, Lasse; Koslowski, Axel; Thiel, Walter

    2016-03-08

    The semiempirical orthogonalization-corrected OMx methods (OM1, OM2, and OM3) go beyond the standard MNDO model by including additional interactions in the electronic structure calculation. When augmented with empirical dispersion corrections, the resulting OMx-Dn approaches offer a fast and robust treatment of noncovalent interactions. Here we evaluate the performance of the OMx and OMx-Dn methods for a variety of ground-state properties using a large and diverse collection of benchmark sets from the literature, with a total of 13035 original and derived reference data. Extensive comparisons are made with the results from established semiempirical methods (MNDO, AM1, PM3, PM6, and PM7) that also use the NDDO (neglect of diatomic differential overlap) integral approximation. Statistical evaluations show that the OMx and OMx-Dn methods outperform the other methods for most of the benchmark sets.

  3. Search of molecular ground state via genetic algorithm: Implementation on a hybrid SIMD-MIMD platform

    International Nuclear Information System (INIS)

    Pucello, N.; D'Agostino, G.; Pisacane, F.

    1997-01-01

    A genetic algorithm for the optimization of the ground-state structure of a metallic cluster has been developed and ported on a SIMD-MIMD parallel platform. The SIMD part of the parallel platform is represented by a Quadrics/APE100 consisting of 512 floating point units, while the MIMD part is formed by a cluster of workstations. The proposed algorithm is composed by a part where the genetic operators are applied to the elements of the population and a part which performs a further local relaxation and the fitness calculation via Molecular Dynamics. These parts have been implemented on the MIMD and on the SIMD part, respectively. Results have been compared to those generated by using Simulated Annealing

  4. Spectroscopic study on deuterated benzenes. I. Microwave spectra and molecular structure in the ground state

    Energy Technology Data Exchange (ETDEWEB)

    Kunishige, Sachi; Katori, Toshiharu; Baba, Masaaki, E-mail: baba@kuchem.kyoto-u.ac.jp [Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Nakajima, Masakazu; Endo, Yasuki [Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902 (Japan)

    2015-12-28

    We observed microwave absorption spectra of some deuterated benzenes and accurately determined the rotational constants of all H/D isotopomers in the ground vibrational state. Using synthetic analysis assuming that all bond angles are 120°, the mean bond lengths were obtained to be r{sub 0}(C–C) = 1.3971 Å and r{sub 0}(C–H) = r{sub 0}(C–D) = 1.0805 Å. It has been concluded that the effect of deuterium substitution on the molecular structure is negligibly small and that the mean bond lengths of C–H and C–D are identical unlike small aliphatic hydrocarbons, in which r{sub 0}(C–D) is about 5 mÅ shorter than r{sub 0}(C–H). It is considered that anharmonicity is very small in the C–H stretching vibration of aromatic hydrocarbons.

  5. Measurement of the ground state spectroscopic quadrupole moments of 191Os and 193Os

    International Nuclear Information System (INIS)

    Ernst, H.; Hagn, E.; Zech, E.

    1979-01-01

    Radioactive 191 Os and 193 Os nuclei have been aligned in an Os single crystal at temperatures down to 4 mK. From the temperature dependence of the γ-anisotropy the quadrupole frequencies vsub(Q) = e 2 qQ/h have been determined as vsub(Q)( 191 OsOs) = -278+-9 MHz and vsub(Q)( 193 OsOs) = -96+-15 MHz. With the known electric field gradient for OsOs of eq = (-4.54+-0.24) x 10 17 V/cm 2 the ground state spectroscopic quadrupole moments are deduced to be Q( 191 Os) = +2.53+-0.16 b and Q( 193 Os) = +0.87+-0.15 b. (orig.)

  6. Long-range interactions of excited He atoms with ground-state noble-gas atoms

    KAUST Repository

    Zhang, J.-Y.

    2013-10-09

    The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition operators. The large-n expansions for the sums over the He oscillator strength divided by the corresponding transition energy are presented for these series. Using the expansions, the C6 coefficients for the systems involving He(131,3S) and He(131,3P) are calculated and found to be in good agreement with directly calculated values.

  7. The ground state magnetic moment and susceptibility of a two electron Gaussian quantum dot

    Science.gov (United States)

    Boda, Aalu; Chatterjee, Ashok

    2018-04-01

    The problem of two interacting electrons moving in a two-dimensional semiconductor quantum dot with Gaussian confinement under the influence of an external magnetic field is studied by using a method of numerical diagonalization of the Hamiltonian matrix with in the effective-mass approximation. The energy spectrum is calculated as a function of the magnetic field. We find the ground state magnetic moment and the magnetic susceptibility show zero temperature diamagnetic peaks due to exchange induced singlet-triplet oscillations. The position and the number of these peaks depend on the size of the quantum dot and also strength of the electro-electron interaction. The theory is applied to a GaAs quantum dot.

  8. Degenerate Ground State in a Mesoscopic YBa2Cu3O

    International Nuclear Information System (INIS)

    Il'ichev, E.; Grajcar, M.; Hlubina, R.; IJsselsteijn, R. P. J.; Hoenig, H. E.; Meyer, H.-G.; Golubov, A.; Amin, M. H. S.; Zagoskin, A. M.; Omelyanchouk, A. N.

    2001-01-01

    We have measured the current-phase relationship I (var-phi) of symmetric 45 degree YBa 2 Cu 3 O 7-x grain boundary Josephson junctions. Substantial deviations of the Josephson current from conventional tunnel-junction behavior have been observed: (i) The critical current exhibits, as a function of temperature T , a local minimum at a temperature T * . (ii) At T∼T * , the first harmonic of I(var-phi) changes sign. (iii) For T * , the second harmonic of I(var-phi) is comparable to the first harmonic, and (iv) the ground state of the junction becomes degenerate. The results are in good agreement with a microscopic model of Josephson junctions between d -wave superconductors

  9. Strongly correlated quasi-one-dimensional bands: Ground states, optical absorption, and phonons

    International Nuclear Information System (INIS)

    Campbell, D.K.; Gammel, J.T.; Loh, E.Y. Jr.

    1989-01-01

    Using the Lanczos method for exact diagonalization on systems up to 14 sites, combined with a novel ''phase randomization'' technique for extracting more information from these small systems, we investigate several aspects of the one-dimensional Peierls-Hubbard Hamiltonian, in the context of trans-polyacetylene: the dependence of the ground state dimerization on the strength of the electron-electron interactions, including the effects of ''off-diagonal'' Coulomb terms generally ignored in the Hubbard model; the phonon vibrational frequencies and dispersion relations, and the optical absorption properties, including the spectrum of absorptions as a function of photon energy. These three different observables provide considerable insight into the effects of electron-electron interactions on the properties of real materials and thus into the nature of strongly correlated electron systems. 29 refs., 11 figs

  10. Atomic mass and characteristic constant of nuclear ground state (CENPL.MCC). Pt. 1

    International Nuclear Information System (INIS)

    Su Zongdi; Ma Lizhen; Zhou Chunmei; Ge Zhigang

    1994-01-01

    Atomic mass and characteristic constants for nuclear ground states are basic data for nuclear physics, and necessary ones for basic researches, theoretical calculations, as well as many applied researches. The atomic mass of exotic nuclei quite far from the valley stability are also very important for astrophysics researches. The above-requirement is paid attention to in our setting up this file. The recent and as many as possible data (such as the half-lives of the new nuclides 202 Pt, 208 Hg and 185 Hf and the mass excess of 199 Ir, which were produced and distinguished by Chinese scientists) have been collected, and put into the computer-based data file in brief table format. (1 fig.)

  11. Analytical model of ground-state lasing phenomenon in broadband semiconductor quantum dot lasers

    Science.gov (United States)

    Korenev, Vladimir V.; Savelyev, Artem V.; Zhukov, Alexey E.; Omelchenko, Alexander V.; Maximov, Mikhail V.

    2013-05-01

    We introduce an analytical approach to the description of broadband lasing spectra of semiconductor quantum dot lasers emitting via ground-state optical transitions of quantum dots. The explicit analytical expressions describing the shape and the width of lasing spectra as well as their temperature and injection current dependences are obtained in the case of low homogeneous broadening. It is shown that in this case these dependences are determined by only two dimensionless parameters, which are the dispersion of the distribution of QDs over the energy normalized to the temperature and loss-to-maximum gain ratio. The possibility of optimization of laser's active region size and structure by using the intentionally introduced disorder is also carefully considered.

  12. Ground-state hyperfine splitting for Rb, Cs, Fr, Ba+, and Ra+

    Science.gov (United States)

    Ginges, J. S. M.; Volotka, A. V.; Fritzsche, S.

    2017-12-01

    We have systematically investigated the ground-state hyperfine structure for alkali-metal atoms 87Rb,133Cs, and 211Fr and alkali-metal-like ions +135Ba and +225Ra, which are of particular interest for parity violation studies. The quantum electrodynamic one-loop radiative corrections have been rigorously evaluated within an extended Furry picture employing core-Hartree and Kohn-Sham atomic potentials. Moreover, the effect of the nuclear magnetization distribution on the hyperfine structure intervals has been studied in detail and its uncertainty has been estimated. Finally, the theoretical description of the hyperfine structure has been completed with full many-body calculations performed in the all-orders correlation potential method.

  13. Untangling complex networks: Risk minimization in financial markets through accessible spin glass ground states

    Science.gov (United States)

    Lisewski, Andreas Martin; Lichtarge, Olivier

    2010-08-01

    Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network’s Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.

  14. Role of entropy in the ground state formation of frustrated systems

    Science.gov (United States)

    Sereni, Julian G.

    2018-05-01

    The absence of magnetic order in Rare Earth-based frustrated compounds allows to recognize the action of the third law of thermodynamics in the low temperature behavior of those systems. One of the most relevant findings is the appearance of a coincident specific heat Cm / T|T→0 ≈ 7 J /molK2 'plateau' in six Yb systems. This characteristic feature occurs after a systematic modification of the thermal trajectory of their entropies Sm (T) in the range of a few hundred milikelvin degrees. Such behavior is explained by the formation of an entropy-bottleneck imposed by the third law constraint (Sm|T→0 ≥ 0), that drives the system into alternative ground states. Based in these finding, three possible approaches to the Sm|T→0 limit observed in real systems are analyzed in terms of the ∂2Sm / ∂T2 dependencies.

  15. Ground state oxygen holes and the metal-insulator transition in rare earth nickelates

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, Thorsten; Bisogni, Valentina; Huang, Yaobo; Strocov, Vladimir [Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Catalano, Sara; Gibert, Marta; Scherwitzl, Raoul; Zubko, Pavlo; Triscone, Jean-Marc [Departement de Physique de la Matiere Condensee, University of Geneva (Switzerland); Green, Robert J.; Balandeh, Shadi; Sawatzky, George [Department of Physics and Astronomy, University of British Columbia, Vancouver (Canada)

    2015-07-01

    Perovskite rare-earth (Re) nickelates ReNiO{sub 3} continue to attract a lot of interest owing to their intriguing properties like a sharp metal to insulator transition (MIT), unusual magnetic order and expected superconductivity in specifically tuned super-lattices. Full understanding of these materials, however, is hampered by the difficulties in describing their electronic ground state (GS). From X-ray absorption (XAS) at the Ni 2p{sub 3/2} edge of thin films of NdNiO{sub 3} and corresponding RIXS maps vs. incident and transferred photon energies we reveal that the electronic GS configuration of NdNiO{sub 3} is composed of delocalized and localized components. Our study conveys that a Ni 3d{sup 8}-like configuration with holes at oxygen takes on the leading role in the GS and the MIT of ReNiO{sub 3} as proposed by recent model theories.

  16. Population of Metastable States in Stable Hafnium and Ytterbium Nuclei via Beam Break-up

    International Nuclear Information System (INIS)

    Malwela, T.; Ntshangase, S.S.; Shirinda, O.; Bark, R.A.; Gueorguieva, E.; Lawrie, J.J.; Mullins, S.M.; Murray, S.H.T.; Sharpey-Schafer, J.F.; Gal, J.; Kalinka, G.; Krasznahorkay, A.; Molnar, J.; Nyako, B.M.; Timar, J.; Zolnai, L.; Hlatshwayo, T.; Juhasz, K.; Komati, F.S.; Scheurer, J.N.

    2005-01-01

    The ''Chessboard'' section of the DIAMANT charged-particle array has been coupled with the AFRODITE γ-ray spectrometer at the iThemba Laboratory for Accelerator Based Sciences. Charged-particle-γ-ray coincidence data were recorded during the bombardment of a 176Yb target with a 13C beam at an energy of 90 MeV. The purpose of the investigation was to study the population of metastable states in hafium nuclei via incomplete fusion reactions in which the beam breaks up due to its α-cluster character. Of note was the observation of the band based on the Kπ = 16+, T1/2 = 31 year isomer in 178Hf to its 19+ member. Also, decays from the high-K isomeric states in 174Yb and 176Yb. which were populated via 3αxn channels, indicative of complete break-up of the 13C beam

  17. A novel thermosetting gel electrolyte for stable quasi-solid-state dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Z.; Lin, J.M.; Huang, M.L.; Hao, S.C. [Institute of Materials Physical Chemistry, Huaqiao University, Quanzhou, 362021 (China); Sato, T.; Yin, S. [Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 1-1 Katahira 2-Chome, Aoba-ku, Sendai 980-8577 (Japan); Wu, J.H.

    2007-11-19

    Using poly(acrylic acid)-poly(ethylene glycol) hybrid-absorbing liquid electrolyte, we prepare a novel thermosetting gel electrolyte (TSGE) with ionic conductivity of 6.12 mS cm{sup -1}. Based on the TSGE, a quasi-solid-state dye-sensitized solar cell with a good long-term stability and light-to-electricity conversion efficiency of 6.10 % is attained under AM 1.5 irradiation. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  18. Family, state, class and solidarity: re-conceptualising intergenerational solidarity through the grounded theory approach.

    Science.gov (United States)

    Timonen, Virpi; Conlon, Catherine; Scharf, Thomas; Carney, Gemma

    2013-09-01

    The relationship between class and intergenerational solidarities in the public and private spheres calls for further conceptual and theoretical development. This article discusses the findings from the first wave of a qualitative longitudinal study entitled Changing Generations , conducted in Ireland in 2011-2012, comprising 100 in-depth interviews with men and women across the age and socioeconomic spectrums. Constructivist grounded theory analysis of the data gives rise to the following postulates: (1) intergenerational solidarity at the family level is strongly contoured by socioeconomic status (SES); (2) intergenerational solidarity evolves as family generations observe each others' practices and adjust their expectations accordingly; (3) intergenerational solidarity within families is also shaped by the public sphere (the welfare state) that generates varying expectations and levels of solidarity regarding State supports for different age groups, again largely dependent on SES; (4) the liberal welfare state context, especially at a time of economic crisis, enhances the significance of intergenerational solidarity within families. We conclude by calling for research that is attuned to age/generation, gender and class, and how these operate across the family and societal levels.

  19. Photoisomerization around a fulvene double bond: coherent population transfer to the electronic ground state?

    Science.gov (United States)

    Ioffe, Ilya; Dobryakov, Alexander L; Granovsky, Alexander A; Ernsting, Nikolaus P; Lustres, J Luis Pérez

    2011-07-11

    Photoisomerization around a central fulvene-type double bond is known to proceed through a conical intersection at the perpendicular geometry. The process is studied with an indenylidene-dihydropyridine model compound, allowing the use of visible excitation pulses. Transient absorption shows that 1) stimulated emission shifts to the red and loses oscillator strength on a 50 fs timescale, and 2) bleach recovery is highly nonexponential and not affected by solvent viscosity or methyl substitution at the dihydropyridine ring. Quantum-chemical calculations are used to explain point 1 as a result of initial elongation of the central C=C bond with mixing of S(2) and S(1) states. From point 2 it is concluded that internal conversion of S(1)→S(0) does not require torsional motion to the fully perpendicular state. The S(1) population appears to encounter a sink on the torsional coordinate before the conical intersection is reached. Rate equations cannot model the observed ground-state recovery adequately. Instead the dynamics are best described with a strongly damped oscillatory contribution, which could indicate coherent S(1)-S(0) population transfer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Competition of ground states in URu2Si2 and UCoGe

    International Nuclear Information System (INIS)

    Hassinger, E.

    2010-10-01

    In this thesis, two uranium based heavy fermion compounds are studied under pressure. URu2Si2 has a mysterious ground state below T0 = 17.5 K at ambient pressure. The order parameter has not been identified yet which led to the name 'hidden order' (HO). In addition, below 1.5 K the system becomes superconducting. With pressure, the ground state switches from the HO phase to an antiferromagnetic (AF) phase at a critical pressure and superconductivity is concomitantly suppressed. Shubnikov-de Haas measurements under pressure show that the Fermi surface doesn't change between the two phases. The folding of the Fermi surface which occurs in the high pressure AF phase therefore already happens in the HO phase, indicating a unit cell doubling. Our measurements of the complete angular dependence of the oscillation frequencies test the electronic structure and support new theoretical band structure calculations with rather itinerant 5f electrons. The second part of my research focuses on another uranium compound, UCoGe. It is one of the few known materials where superconductivity (Tsc = 0.6 K) coexists with ferromagnetism (T Curie = 2.8 K). Precise studies of the pressure phase diagram by resistivity, ac calorimetry and ac susceptibility show that the ferromagnetic phase is suppressed at a pressure of about 1 GPa and the superconducting phase extends into the paramagnetic phase induced by pressure. When ferromagnetism is suppressed to the superconducting transition no further distinct ferromagnetic anomalies are observed. Thus, the pressure phase diagram of UCoGe is unique in the class of ferromagnetic superconductors. (author)

  1. Ground state properties of neutron-rich Mg isotopes the "island of inversion" studied with laser and $\\beta$-NMR spectroscopy

    CERN Document Server

    Kowalska, M

    2006-01-01

    Studies in regions of the nuclear chart in which the model predictions of properties of nuclei fail can bring a better understanding of the strong interaction in the nuclear medium. To such regions belongs the so called "island of inversion" centered around Ne, Na and Mg isotopes with 20 neutrons in which unexpected ground-state spins, large deformations and dense low-energy spectra appear. This is a strong argument that the magic N=20 is not a closed shell in this area. In this thesis investigations of isotope shifts of stable $^{24-26}$Mg, as well as spins and magnetic moments of short-lived $^{29,31}$Mg are presented. The successful studies were performed at the ISOLDE facility at CERN using collinear laser and $\\beta$-NMR spectroscopy techniques. The isotopes were investigated as single-charged ions in the 280 nm transition from the atomic ground state $^2\\!$S$_{1/2}$ to one of the two lowest excited states $^2\\!$P$_{1/2 ,\\,3/2}$ using continuous wave laser beams. The isotope-shift measurements with fluor...

  2. Study of some electronics properties of new superconductor Sr2VO3FeAs in ground state

    Directory of Open Access Journals (Sweden)

    M Majidiyan

    2010-09-01

    Full Text Available In this paper, some electronics properties of new superconductor Sr2VO3FeAs, such as density of states, band structure, density of electron cloud and bound lengths in the ground state have been calculated. According to N(Ef in ground state CV/T value has been estimated. The calculations were performed in the framework of density functional theory (DFT, using the full potential linearized augmented plane wave (FP-LAPW method with the general gradient approximation (GGA.

  3. Femtosecond stimulated Raman spectroscopy as a tool to detect molecular vibrations in ground and excited electronic states

    Energy Technology Data Exchange (ETDEWEB)

    Gelin, Maxim F.; Domcke, Wolfgang [Department of Chemistry, Technische Universität München, D-85747 Garching (Germany); Rao, B. Jayachander [Departamento de Química and Centro de Química, Universidade de Coimbra, 3004-535 Coimbra (Portugal)

    2016-05-14

    We give a detailed theoretical analysis of the simplest variant of femtosecond stimulated Raman spectroscopy, where a picosecond Raman pump pulse and a femtosecond Raman probe pulse are applied resonantly to a chromophore in thermal equilibrium in the ground electronic state. We demonstrate that this technique is capable of the detection of dephasing-free Raman-like lines revealing vibrational modes not only in the electronic ground state but also in the excited electronic state of the chromophore. The analytical results obtained with simplifying assumptions for the shape of the laser pulses are substantiated by numerical simulations with realistic laser pulses, employing the equation-of-motion phase-matching approach.

  4. Sub-Doppler spectroscopy of thioformaldehyde: Excited state perturbations and evidence for rotation-induced vibrational mixing in the ground state

    International Nuclear Information System (INIS)

    Clouthier, D.J.; Huang, G.; Adam, A.G.; Merer, A.J.

    1994-01-01

    High-resolution intracavity dye laser spectroscopy has been used to obtain sub-Doppler spectra of transitions to 350 rotational levels in the 4 1 0 band of the A 1 A 2 --X 1 A 1 electronic transition of thioformaldehyde. Ground state combination differences from the sub-Doppler spectra, combined with microwave and infrared data, have been used to improve the ground state rotational and centrifugal distortion constants of H 2 CS. The upper state shows a remarkable number of perturbations. The largest of these are caused by nearby triplet levels, with matrix elements of 0.05--0.15 cm -1 . A particularly clear singlet--triplet avoided crossing in K a ' = 7 has been shown to be caused by interaction with the F 1 component of the 3 1 6 2 vibrational level of the a 3 A 2 state. At least 53% of the S 1 levels show evidence of very small perturbations by high rovibronic levels of the ground state. The number of such perturbations is small at low J, but increases rapidly beyond J=5 such that 40%--80% of the observed S 1 levels of any given J are perturbed by ground state levels. Model calculations show that the density and J dependence of the number of perturbed levels can be explained if there is extensive rotation-induced mixing of the vibrational levels in the ground state

  5. Basic equations of quasiparticle-phonon model of nucleus with account of Pauli principle and phonons interactions in ground state

    International Nuclear Information System (INIS)

    Voronov, V.V.; Dang, N.D.

    1984-01-01

    the system of equations, enabling to calculate the energy and the structure of excited states, described by the wave function, containing one- and two-phon components was obtained in the framework of quasiparticlephonon model. The requirements of Pauli principle for two-phonon components and phonon correlation in the ground nucleus state are taken into account

  6. Calculation of the ground and excited states of the Ne2 molecule by the Variational Cellular Method

    International Nuclear Information System (INIS)

    Dias, A.M.; Rosato, A.

    1982-01-01

    The potential curves for the ground 1 μ + sub(g) and for the first singlet excited state 1 μ + sub(u) of the Ne 2 molecule are determined by the Variational Cellular Method. From these curves some spectroscopical constants are obtained. Ionization energies of the excited state 1 μ + sub(u) are calculated. (Author) [pt

  7. Atomic hydrogen and argon ground state density determination in a recombining plasma using visible light absorption spectroscopy

    NARCIS (Netherlands)

    Otorbaev, D.K.; Buuron, A.J.M.; Sanden, van de M.C.M.; Meulenbroeks, R.F.G.; Schram, D.C.

    1995-01-01

    The atomic radical density in the first excited state, obtained by the technique of optical absorption spectroscopy, and a simple kinetic model are used to determine the radical ground state density in a recombining expanding plasma. The kinetic model used does not require knowledge of the shape of

  8. Three-body problem in d-dimensional space: Ground state, (quasi)-exact-solvability

    Science.gov (United States)

    Turbiner, Alexander V.; Miller, Willard; Escobar-Ruiz, M. A.

    2018-02-01

    As a straightforward generalization and extension of our previous paper [A. V. Turbiner et al., "Three-body problem in 3D space: Ground state, (quasi)-exact-solvability," J. Phys. A: Math. Theor. 50, 215201 (2017)], we study the aspects of the quantum and classical dynamics of a 3-body system with equal masses, each body with d degrees of freedom, with interaction depending only on mutual (relative) distances. The study is restricted to solutions in the space of relative motion which are functions of mutual (relative) distances only. It is shown that the ground state (and some other states) in the quantum case and the planar trajectories (which are in the interaction plane) in the classical case are of this type. The quantum (and classical) Hamiltonian for which these states are eigenfunctions is derived. It corresponds to a three-dimensional quantum particle moving in a curved space with special d-dimension-independent metric in a certain d-dependent singular potential, while at d = 1, it elegantly degenerates to a two-dimensional particle moving in flat space. It admits a description in terms of pure geometrical characteristics of the interaction triangle which is defined by the three relative distances. The kinetic energy of the system is d-independent; it has a hidden sl(4, R) Lie (Poisson) algebra structure, alternatively, the hidden algebra h(3) typical for the H3 Calogero model as in the d = 3 case. We find an exactly solvable three-body S3-permutationally invariant, generalized harmonic oscillator-type potential as well as a quasi-exactly solvable three-body sextic polynomial type potential with singular terms. For both models, an extra first order integral exists. For d = 1, the whole family of 3-body (two-dimensional) Calogero-Moser-Sutherland systems as well as the Tremblay-Turbiner-Winternitz model is reproduced. It is shown that a straightforward generalization of the 3-body (rational) Calogero model to d > 1 leads to two primitive quasi

  9. Stable Weyl points, trivial surface states, and particle-hole compensation in WP2

    Science.gov (United States)

    Razzoli, E.; Zwartsenberg, B.; Michiardi, M.; Boschini, F.; Day, R. P.; Elfimov, I. S.; Denlinger, J. D.; Süss, V.; Felser, C.; Damascelli, A.

    2018-05-01

    A possible connection between extremely large magnetoresistance and the presence of Weyl points has garnered much attention in the study of topological semimetals. Exploration of these concepts in transition-metal diphosphides WP2 has been complicated by conflicting experimental reports. Here we combine angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations to disentangle surface and bulk contributions to the ARPES intensity, the superposition of which has plagued the determination of the band structure in WP2. Our results show that while the hole- and electronlike Fermi surface sheets originating from surface states have different areas, the bulk-band structure of WP2 is electron-hole compensated in agreement with DFT. Furthermore, the ARPES band structure is compatible with the presence of at least four temperature-independent Weyl points, confirming the topological nature of WP2 and its stability against lattice distortions.

  10. Dipole-resonance assisted isomerization in the electronic ground state using few-cycle infrared pulses.

    Science.gov (United States)

    Skocek, Oliver; Uiberacker, Christoph; Jakubetz, Werner

    2011-06-30

    A computational investigation of HCN → HNC isomerization in the electronic ground state by one- and few-cycle infrared pulses is presented. Starting from a vibrationally pre-excited reagent state, isomerization yields of more than 50% are obtained using single one- to five-cycle pulses. The principal mechanism includes two steps of population transfer by dipole-resonance (DR), and hence, the success of the method is closely linked to the polarity of the system and, in particular, the stepwise change of the dipole moment from reactant to transition state and on to products. The yield drops massively if the diagonal dipole matrix elements are artificially set to zero. In detail, the mechanism includes DR-induced preparation of a delocalized vibrational wavepacket, which traverses the barrier region and is finally trapped in the product well by DR-dominated de-excitation. The excitation and de-excitation steps are triggered by pulse lobes of opposite field direction. As the number of optical cycles is increased, the leading field lobes prepare a vibrational superposition state by off-resonant ladder climbing, which is then subjected to the three steps of the principal isomerization mechanism. DR excitation is more efficient from a preformed vibrational wavepacket than from a molecular eigenstate. The entire process can be loosely described as Tannor-Kosloff-Rice type transfer mechanism on a single potential surface effected by a single pulse, individual field lobes assuming the roles of pump- and dump-pulses. Pre-excitation to a transient wavepacket can be enhanced by applying a separate, comparatively weak few-cycle prepulse, in which the prepulse prepares a vibrational wavepacket. The two-pulse setup corresponds to a double Tannor-Kosloff-Rice control scheme on a single potential surface.

  11. Experimental apparatus for overlapping a ground-state cooled ion with ultracold atoms

    Science.gov (United States)

    Meir, Ziv; Sikorsky, Tomas; Ben-shlomi, Ruti; Akerman, Nitzan; Pinkas, Meirav; Dallal, Yehonatan; Ozeri, Roee

    2018-03-01

    Experimental realizations of charged ions and neutral atoms in overlapping traps are gaining increasing interest due to their wide research application ranging from chemistry at the quantum level to quantum simulations of solid state systems. In this paper, we describe our experimental system in which we overlap a single ground-state cooled ion trapped in a linear Paul trap with a cloud of ultracold atoms such that both constituents are in the ?K regime. Excess micromotion (EMM) currently limits atom-ion interaction energy to the mK energy scale and above. We demonstrate spectroscopy methods and compensation techniques which characterize and reduce the ion's parasitic EMM energy to the ?K regime even for ion crystals of several ions. We further give a substantial review on the non-equilibrium dynamics which governs atom-ion systems. The non-equilibrium dynamics is manifested by a power law distribution of the ion's energy. We also give an overview on the coherent and non-coherent thermometry tools which can be used to characterize the ion's energy distribution after single to many atom-ion collisions.

  12. Ground state entropy of the Potts antiferromagnet on triangular lattice strips

    International Nuclear Information System (INIS)

    Chang Shuchiuan; Shrock, Robert

    2001-01-01

    We present exact calculations of the zero-temperature partition function (chromatic polynomial) P for the q-state Potts antiferromagnet on triangular lattice strips of arbitrarily great length L x vertices and of width L y vertices and, in the L x →∞ limit, the exponent of the ground state entropy, W=e S 0 /k B . The strips considered, with their boundary conditions (BC), are (a) (FBC y , PBC x ) = cyclic for L y =3, 4, (b) (FBC y , TPBC x ) = Moebius, L y =3, (c) (PBC y , PBC x ) = toroidal, L y =3, (d) (PBC y , TPBC x ) = Klein bottle, L y =3, (e) (PBC y , FBC x ) = cylindrical, L y =5, 6, and (f) (FBC y , FBC x ) = free, L y =5, where F, P, and TP denote free, periodic, and twisted periodic. Several interesting features are found, including the presence of terms in P proportional to cos(2πL x /3) for case (c). The continuous locus of points B where W is nonanalytic in the q plane is discussed for each case and a comparative discussion is given of the respective loci B for families with different boundary conditions. Numerical values of W are given for infinite-length strips of various widths and are shown to approach values for the 2D lattice rapidly. A remark is also made concerning a zero-free region for chromatic zeros. Some results are given for strips of other lattices

  13. Ground-state magneto-optical resonances in cesium vapor confined in an extremely thin cell

    International Nuclear Information System (INIS)

    Andreeva, C.; Cartaleva, S.; Petrov, L.; Slavov, D.; Atvars, A.; Auzinsh, M.; Blush, K.

    2007-01-01

    Experimental and theoretical studies are presented related to the ground-state magneto-optical resonance observed in cesium vapor confined in an extremely thin cell (ETC), with thickness equal to the wavelength of the irradiating light. It is shown that utilization of the ETC allows one to examine the formation of a magneto-optical resonance on the individual hyperfine transitions, thus distinguishing processes resulting in dark (reduced absorption) or bright (enhanced absorption) resonance formation. We report experimental evidence of bright magneto-optical resonance sign reversal in Cs atoms confined in an ETC. A theoretical model is proposed based on the optical Bloch equations that involves the elastic interaction processes of atoms in the ETC with its walls, resulting in depolarization of the Cs excited state, which is polarized by the exciting radiation. This depolarization leads to the sign reversal of the bright resonance. Using the proposed model, the magneto-optical resonance amplitude and width as a function of laser power are calculated and compared with the experimental ones. The numerical results are in good agreement with those of experiment

  14. Global potential energy surface of ground state singlet spin O4

    Science.gov (United States)

    Mankodi, Tapan K.; Bhandarkar, Upendra V.; Puranik, Bhalchandra P.

    2018-02-01

    A new global potential energy for the singlet spin state O4 system is reported using CASPT2/aug-cc-pVTZ ab initio calculations. The geometries for the six-dimensional surface are constructed using a novel point generation scheme that employs randomly generated configurations based on the beta distribution. The advantage of this scheme is apparent in the reduction of the number of required geometries for a reasonably accurate potential energy surface (PES) and the consequent decrease in the overall computational effort. The reported surface matches well with the recently published singlet surface by Paukku et al. [J. Chem. Phys. 147, 034301 (2017)]. In addition to the O4 PES, the ground state N4 PES is also constructed using the point generation scheme and compared with the existing PES [Y. Paukku et al., J. Chem. Phys. 139, 044309 (2013)]. The singlet surface is constructed with the aim of studying high energy O2-O2 collisions and predicting collision induced dissociation cross section to be used in simulating non-equilibrium aerothermodynamic flows.

  15. Ground-state properties of anyons in a one-dimensional lattice

    Science.gov (United States)

    Tang, Guixin; Eggert, Sebastian; Pelster, Axel

    2015-12-01

    Using the Anyon-Hubbard Hamiltonian, we analyze the ground-state properties of anyons in a one-dimensional lattice. To this end we map the hopping dynamics of correlated anyons to an occupation-dependent hopping Bose-Hubbard model using the fractional Jordan-Wigner transformation. In particular, we calculate the quasi-momentum distribution of anyons, which interpolates between Bose-Einstein and Fermi-Dirac statistics. Analytically, we apply a modified Gutzwiller mean-field approach, which goes beyond a classical one by including the influence of the fractional phase of anyons within the many-body wavefunction. Numerically, we use the density-matrix renormalization group by relying on the ansatz of matrix product states. As a result it turns out that the anyonic quasi-momentum distribution reveals both a peak-shift and an asymmetry which mainly originates from the nonlocal string property. In addition, we determine the corresponding quasi-momentum distribution of the Jordan-Wigner transformed bosons, where, in contrast to the hard-core case, we also observe an asymmetry for the soft-core case, which strongly depends on the particle number density.

  16. Low energy collisions of spin-polarized metastable argon atoms with ground state argon atoms

    Science.gov (United States)

    Taillandier-Loize, T.; Perales, F.; Baudon, J.; Hamamda, M.; Bocvarski, V.; Ducloy, M.; Correia, F.; Fabre, N.; Dutier, G.

    2018-04-01

    The collision between a spin-polarized metastable argon atom in Ar* (3p54s, 3P2, M = +2) state slightly decelerated by the Zeeman slower-laser technique and a co-propagating thermal ground state argon atom Ar (3p6, 1S0), both merged from the same supersonic beam, but coming through adjacent slots of a rotating disk, is investigated at the center of mass energies ranging from 1 to 10 meV. The duration of the laser pulse synchronised with the disk allows the tuning of the relative velocity and thus the collision energy. At these sub-thermal energies, the ‘resonant metastability transfer’ signal is too small to be evidenced. The explored energy range requires using indiscernibility amplitudes for identical isotopes to have a correct interpretation of the experimental results. Nevertheless, excitation transfers are expected to increase significantly at much lower energies as suggested by previous theoretical predictions of potentials 2g(3P2) and 2u(3P2). Limits at ultra-low collisional energies of the order of 1 mK (0.086 μeV) or less, where gigantic elastic cross sections are expected, will also be discussed. The experimental method is versatile and could be applied using different isotopes of Argon like 36Ar combined with 40Ar, as well as other rare gases among which Krypton should be of great interest thanks to the available numerous isotopes present in a natural gas mixture.

  17. Proton capture to the ground and excited states in light nuclei

    International Nuclear Information System (INIS)

    Anghinolfi, M.; Corvisiero, P.; Guarnone, M.; Ricco, G.; Sanzone, M.; Taiuti, M.; Zucchiatti, A.

    1984-01-01

    Proton capture experiments, when performed with good resolution, generally provide two different kinds of physical information; the ground-state pγ/sub o/ cross section, which is related, through the detailed balance, to the inverse photonuclear γp/sub o/ reaction; the advantage of capture experiments is the definite kinematics, corresponding to monochromatic photons in γp reactions, and a more precise beam monitoring. The pγ/sub x/ cross section to the various excited states of the final nucleus; this information is typical of capture experiments, since excited nuclear targets are not available. Many laboratories performed extensive capture experiments at excitation energies up to the GDR region, but only recently few groups (Ohio, Triangle and Genova Universities) extended the investigation to energies above the GDR. In fact more severe experimental problems arise at higher energies: since the pγ differential cross sections range in this energy region between 0.1 and 1Γb/sr, while competitive reactions have two or three order of magnitude higher cross sections, the signal-to-background ratio is very low. The data analysis strongly depends on the detector line shape, scarsely known at photon energies above 20 MeV; a very accurate knowledge of the detector response function is therefore necessary

  18. On the Calculation of Quantum Mechanical Ground States from Classical Geodesic Motion on Certain Spaces of Constant Negative Curvature

    CERN Document Server

    Tomaschitz, R

    1989-01-01

    We consider geodesic motion on three-dimensional Riemannian manifolds of constant negative curvature, topologically equivalent to S x ]0,1[, S a compact surface of genus two. To those trajectories which are bounded and recurrent in both directions of the time evolution a fractal limit set is associated whose Hausdorff dimension is intimately connected with the quantum mechanical energy ground state, determined by the Schrodinger operator on the manifold. We give a rather detailed and pictorial description of the hyperbolic spaces we have in mind, discuss various aspects of classical and quantum mechanical motion on them as far as they are needed to establish the connection between energy ground state and Hausdorff dimension and give finally some examples of ground state calculations in terms of Hausdorff dimensions of limit sets of classical trajectories.

  19. Highly macroscopically degenerated single-point ground states as source of specific heat capacity anomalies in magnetic frustrated systems

    Science.gov (United States)

    Jurčišinová, E.; Jurčišin, M.

    2018-04-01

    Anomalies of the specific heat capacity are investigated in the framework of the exactly solvable antiferromagnetic spin- 1 / 2 Ising model in the external magnetic field on the geometrically frustrated tetrahedron recursive lattice. It is shown that the Schottky-type anomaly in the behavior of the specific heat capacity is related to the existence of unique highly macroscopically degenerated single-point ground states which are formed on the borders between neighboring plateau-like ground states. It is also shown that the very existence of these single-point ground states with large residual entropies predicts the appearance of another anomaly in the behavior of the specific heat capacity for low temperatures, namely, the field-induced double-peak structure, which exists, and should be observed experimentally, along with the Schottky-type anomaly in various frustrated magnetic system.

  20. On the calculation of quantum mechanical ground states from classical geodesic motion on certain spaces of constant negative curvature

    International Nuclear Information System (INIS)

    Tomaschitz, R.

    1989-01-01

    We consider geodesic motion on three-dimensional Riemannian manifolds of constant negative curvature, topologically equivalent to S x ]0,1[, S a compact surface of genus two. To those trajectories which are recurrent in both directions of the time evolution t → +∞, t → -∞ a fractal limit set is associated whose Hausdorff dimension is intimately connected with the quantum mechanical energy ground state, determined by the Schroedinger operator on the manifold. We give a rather detailed and pictorial description of the hyperbolic spaces we have in mind, discuss various aspects of classical and quantum mechanical motion on them as far as they are needed to establish the connection between energy ground state and Hausdorff dimension and give finally some examples of ground state calculations in terms of Hausdorff dimensions of limit sets of classical trajectories. (orig.)