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Lee-Yang zeros and two-time spin correlation function

PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS 2018年 509卷 1095-1101页

作者： Gnatenko, Kh. P. Kargol, A. Tkachuk, V. M. Ivan Franko Natl Univ Lviv Dept Theoret Phys 12 Drahomanov St UA-79005 Lvov Ukraine Uniwersytet Marii Curie Sklodowskiej Inst Matemat PL-20031 Lublin Poland

The two-time correlation function for probe spin interacting with spin system (bath) is studied. We show that zeros of this function correspond to zeros of partition function of spin system in complex magnetic field. The obtained relation gives new possibility to observe the Lee-Yang zeros experimentally. Namely, we show that measuring of the time dependence of correlation function allows direct experimental observation of the Lee-Yang zeros. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Lee-Yang zeros two-time correlation function Spin system

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two-time correlation functions of a two-level system influenced by a composite environment

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QUANTUM INFORMATION PROCESSING 2018年第11期17卷 1-21页

作者： Ban, Masashi Ochanomizu Univ Grad Sch Humanities & Sci Bunkyo Ku 2-1-1 Otsuka Tokyo 1128610 Japan

To study the quantum regression theorem and the Leggett-Garg inequality, two-time correlation functions are calculated for a two-level system which is placed under the influence of a composite environment consisting of two subsystems. two different configurations, I and II, are considered. In the configuration I, a two-level system of interest interacts with a thermal reservoir via another two-level system. In the configuration II, a relevant two-level system is influenced independently by another two-level system and a thermal reservoir. In both configurations, the thermal reservoir is assumed to have a sufficiently short correlation time. When an interacting nuclear-spin and electron-spin system is considered, the relevant system is a nuclear-spin (electron-spin) in the configuration I (II). It is shown that the quantum regression theorem for the relevant two-level system is always valid in the configuration II while it is not in the configuration I, regardless of whether the reduced time evolution is Markovian or not. Furthermore, it is found that the Leggett-Garg inequality can be violated in both configurations. The dependence of the violation on the parameters characterizing the open two-level system is investigated.

关键词： two-time correlation function Composite environment Quantum regression theorem The Leggett-Garg inequality

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Speckle correlation as a monitor of X-ray free-electron laser induced crystal lattice deformation

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JOURNAL OF SYNCHROTRON RADIATION 2020年第6期27卷 1470-1476页

作者： Plumley, Rajan Sun, Yanwen Teitelbaum, Samuel Song, Sanghoon Sato, Takahiro Chollet, Matthieu Nelson, Silke Wang, Nan Sun, Peihao Robert, Aymeric Fuoss, Paul Sutton, Mark Zhu, Diling SLAC Natl Accelerator Lab Linac Coherent Light Source 2575 Sand Hill Rd Menlo Pk CA 94025 USA Stanford Univ Dept Phys 450 Serra Mall Stanford CA 94305 USA McGill Univ Phys Dept 845 Sherbrooke St W Montreal PQ Canada SLAC Natl Accelerator Lab PULSE Inst 2575 Sand Hill Rd Menlo Pk CA 94025 USA

X-ray free-electron lasers (X-FELs) present new opportunities to study ultrafast lattice dynamics in complex materials. While the unprecedented source brilliance enables high fidelity measurement of structural dynamics, it also raises experimental challenges related to the understanding and control of beam-induced irreversible structural changes in samples that can ultimately impact the interpretation of experimental results. This is also important for designing reliable high performance X-ray optical components. In this work, X-FEL beam-induced lattice alterations are investigated by measuring the shot-to-shot evolution of near-Bragg coherent scattering from a single crystalline germanium sample. It is shown that X-ray photon correlation analysis of sequential speckle patterns measurements can be used to monitor the nature and extent of lattice rearrangements. Abrupt, irreversible changes are observed following intermittent high-fluence monochromatic X-ray pulses, thus revealing the existence of a threshold response to X-FEL pulse intensity.

关键词： X-ray damage two-time correlation function free-electron laser

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An investigation into the statistical properties of TB episodes in a South African community with high HIV prevalence

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JOURNAL OF THEORETICAL BIOLOGY 2011年第1期270卷 154-163页

作者： Pretorius, Carel Dodd, Peter Wood, Robin Univ Stellenbosch DST NRF Ctr Excellence Epidemiol Modelling & Anal StIAS SACEMA ZA-7600 Stellenbosch South Africa London Sch Hyg & Trop Med Ctr Math Modelling Infect Dis London WC1 England Univ Cape Town Inst Infect Dis & Mol Med Desmond Tutu HIV Ctr ZA-7700 Rondebosch South Africa

Continuous differential equations are often applied to small populations with little time spent on understanding uncertainty brought about by small-population effects. Despite large numbers of individuals being latently infected with Mycobacterium tuberculosis (TB), progression from latent infection to observable disease is a relatively rare event. For small communities, this means case counts are subject to stochasticity, and deterministic models may not be appropriate tools for interpreting transmission trends. Furthermore, the nonlinear nature of the underlying dynamics means that fluctuations are autocorrelated, which can invalidate standard statistical analyses which assume independent fluctuations. Here we extend recent work using a system of differential equations to study the HIV-TB epidemic in Masiphumelele, a community near Cape Town in South Africa [Bacaer, et al., J. Mol. Biol. 57(4), 557-593] by studying the statistical properties of active TB events. We apply van Kampen's system-size (or population-size) expansion technique to obtain an approximation to a master equation describing the dynamics. We use the resulting Fokker-Planck equation and point-process theory to derive two-time correlation functions for active TB events. This method can be used to gain insight into the temporal aspect of cluster identification, which currently relies on DNA classification only. (C) 2010 Published by Elsevier Ltd.

关键词： Dynamical model Master equation Point process two-time correlation function

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Momentum flux in Rayleigh-Benard convection II

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PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS 2005年第3-4期345卷 448-456页

作者： Shibata, H Sojo Univ Fac Engn Dept Gen Educ Kumamoto 8600082 Japan

We showed that the turbulent viscosity coefficient defined as the molecular viscosity coefficient diverges in the transition region from soft turbulence to hard turbulence in the Rayleigh-Benard convection in the last paper (Physica A 333(2004)71). In the present paper, we measure the strength of the divergence in the viscosity coefficient. The strongest point of the divergence is in the middle of the transition region. In addition, we show how the strength of the divergence depends on the temperature difference between two plates. (C) 2004 Elsevier B.V. All rights reserved.

关键词： Rayleigh-Benard convection Yanagita-Kaneko model two-time correlation function momentum flux turbulent viscosity

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Heat flux in Rayleigh-Benard convection

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PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS 2005年第2-4期352卷 335-346页

作者： Shibata, H Sojo Univ Fac Engn Dept Gen Educ Kumamoto 8600082 Japan

We calculate the heat conductivity of the turbulence induced in the Rayleigh-Benard convection. We show that the heat conductivity becomes large as we increase the temperature difference between the top and the bottom plates, i.e., the strength of the turbulence. We can easily see that the heat conductivity diverges in the transition regime from soft turbulence to hard turbulence as we can see in the viscosity coefficient in the same system. (c) 2005 Elsevier B.V. All rights reserved.

关键词： Rayleigh-Benard convection Yanagita-Kaneko model two-time correlation function heat flux heat conductivity

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A method for calculating two-time correlation functions in the quantum trajectory approach

A method for calculating two-time correlation functions in t...

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10th Central European Workshop on Quantum Optics

作者： Karpati, A Adam, P Janszky, J Hungarian Acad Sci Dept Nonlinear & Quantum Opt Res Inst Solid State Phys & Opt H-1525 Budapest Hungary Univ Pecs Res Grp Nonlinear & Quantum Opt H-7624 Pecs Hungary Univ Pecs Inst Phys H-7624 Pecs Hungary

We developed a technique for calculating two-time correlation functions based on a quantum trajectory approach. Our method requires the simulation of the evolution of a given set of density matrices only once. The evaluation can be carried out from the density matrix data obtained for any quantities, time arguments and initial conditions. The computational efficiency of the method is estimated and an example of application is presented.

关键词： two-time correlation function quantum trajectory

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Momentum flux in Rayleigh-Benard convection

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PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS 2004年第1-4期333卷 71-86页

作者： Shibata, H Sojo Univ Dept Gen Educ Fac Engn Kumamoto 8600082 Japan

The statistical quantities concerning the momentum flux in the Rayleigh-Benard convection are investigated in detail. The transition from soft turbulence to hard turbulence is captured through the momentum flux. The time series of the momentum flux is studied and its power spectrum shows the sign of the transition. The two-time correlation function does not saturate its value in the range of the transition. Except for the transition regime the two-time correlation function for the momentum flux converges to 0 and we estimate the viscosity by the turbulence. We confirm that the viscosity coefficient increases as we increase the temperature difference between the top and bottom plates. (C) 2003 Elsevier B.V. All rights reserved.

关键词： Rayleigh-Benard convection Yanagita-Kaneko model two-time correlation function momentum flux large deviation statistics turbulent viscosity

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A method for calculating two-time correlation functions in the quantum trajectory approach

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JOURNAL OF OPTICS B-QUANTUM AND SEMICLASSICAL OPTICS 2004年第3期6卷 S79-S83页

关键词： two-time correlation function quantum trajectory

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Atomic emission and cavity field spectra of the Jaynes-Cummings model

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CHINESE PHYSICS 2003年第8期12卷 872-878页

作者： Li, FL Gao, SY Zhao, YT Xian Jiaotong Univ Dept Appl Phys Xian 710049 Peoples R China

Atomic emission and cavity field spectra of the Jaynes-Cummings model are analytically compared. We show that the two spectra are in general different, except for the special case where the interaction is resonant, the cavity is initially empty and the retarded time of one-photon emission is considered in calculations of the spectra. In this case, the two spectra are the same. We also show that this result comes from the fact that the two-time autocorrelation function of the cavity field is not directly proportional to that of the atom.

关键词： resonance fluorescence spectrum two-time correlation function

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