On the derivation of quantum kinetic equations. II. Nonlocal Uehling-Uhlenbeck equation

The binary and triple collision terms of the quantum kinetic equation derived previously are analyzed in the weak coupling approximation. In this approximation the equation appears to be a nonlocal Markovian extension of the kinetic equation due to Uehling and Uhlenbeck. After linearization, its relationship with non-Markovian formulations found in the literature is studied.This investigation is part of the research program of the Stichting voor Fundamenteel Onderzoek der Materie (FOM), which is financially supported by the Nederlandse Organisatie voor Zuiver Wetenschappelijk Onderzoek (ZWO).     

On quantum kinetic equation for hierarchic systems

The energy dissipation in a gas of structured objects, e.g. molecules, is considered. It is shown that the macroscopic irreversibility of the kinetic processes can be considered as a consequence of the microscopic operator ordering. Our approach is free of any special assumptions on the space-time geometry, except for the general region causality assumptions [J.C. Christensen, L. Crane, J. Math. Phys. 46 (2005) 122502], it can be applied to a wide variety of processes, from the cosmological processes at Big Bang stage till the energy dissipation in molecular gases.     

Tuning the dipolar interaction in quantum gases

We have studied the tunability of the interaction between permanent dipoles in Bose-Einstein condensates. Based on time-dependent control of the anisotropy of the dipolar interaction, we show that even the very weak magnetic dipole coupling in alkali gases can be used to excite collective modes. Furthermore, we discuss how the effective dipolar coupling in a Bose-Einstein condensate can be tuned from positive to negative values and even switched off completely by fast rotation of the orientation of the dipoles.     

A relativistic quantum kinetic equation for nucleus-nucleus collisions

A relativistic quantum kinetic equation is derived corresponding to the non-equilibrium extension of the Dirac-Brueckner approach for nuclear matter. The equation is of the VUU-type with a self-consistent mean field and collision term.     

Generalized quantum kinetic equation for conducting disordered media

A quantum kinetic equation for disordered structures is derived using the Kadanoff-Baym technique. The nonlocal nature of the collision integral and the influence of the external field are taken into account by the generalized Kadanoff-Baym ansatz (GKB ansatz). The collision integral is explicitly constructed for the substitional A_xB_1–x binary alloy system.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 14–20, May, 1989.     

Linear quantum enskog equation II. Inhomogeneous quantum fluids

This is the second part of a work concerned with the quantum-statistical generalization of classical Enskog theory, whereby the first part is extended to spatially inhomogeneous fluids. In particular, working with Liouville operators and using cluster expansions and projection operators, we derive the inhomogeneous linear quantum Enskog equation and express the dynamic structure factor and the nonlocal mobility tensor in terms of the corresponding quantum Enskog collision operator. Thereby static correlations due to excluded volume effects and quantum-statistical correlations due to the fermionic (bosonic) character of the pairwise strongly interacting particles are treated exactly. When static correlations are neglected, this Enskog equation reduces to the inhomogeneous linear quantum Boltzmann equation (containing an exchange-modifiedt-matrix). In the classical limit, the well-known linear revised Enskog theory is recovered for hard spheres.     

Hilbert-Enskog-Chapman expansion in the turbulent kinetic theory of gases. II

This is a continuation of the article (I) with the same title. [Tian-quan Chen, preceding articleJ. Stat. Phys. 25, 491 (1981).] We carry on with the Enskog-Chapman expansion here.     

Dark resonances for ground-state transfer of molecular quantum gases

One possible way to produce ultra-cold, high-phase-space-density quantum gases of molecules in the rovibronic ground state is given by molecule association from quantum-degenerate atomic gases on a Feshbach resonance and subsequent coherent optical multi-photon transfer into the rovibronic ground state. In ultra-cold samples of Cs₂ molecules, we observe two-photon dark resonances that connect the intermediate rovibrational level |v=73,J=2〉 with the rovibrational ground state |v=0,J=0〉 of the singlet X ¹ Σ _g ⁺ ground-state potential. For precise dark resonance spectroscopy we exploit the fact that it is possible to efficiently populate the level |v=73,J=2〉 by two-photon transfer from the dissociation threshold with the stimulated Raman adiabatic passage (STIRAP) technique. We find that at least one of the two-photon resonances is sufficiently strong to allow future implementation of coherent STIRAP transfer of a molecular quantum gas to the rovibrational ground state |v=0,J=0〉.     

Relativistic kinetic theory of quantum systems: III. Transport equation for a neutrino system

On the basis of the quantum-mechanical equations of motion and the statistical assumption that dynamical correlations present in the initial state may be ignored, a kinetic equation for a dilute neutrino system is derived. If the system is sufficiently uniform in space this equation reduces to the relativistic Boltzmann equation for massless particles with a quantum-mechanical transition probability.     

On the solution to the Boltzmann kinetic equation in calculating the heat flux in polyatomic gases

The solution of the linearized Wang Chang-Uhlenbeck equation using the Hanson-Morse model for calculating the heat flux in a plane molecular gas layer has been considered. General expressions (independent of the form and method for solving the kinetic equation) of the dependence of heat flux on the energy accommodation coefficients have been derived. The values of the temperature jump coefficient for specific gases have been obtained.     

Nonlocal form of quantum off-shell kinetic equation

A new nonlocal form of the off-shell kinetic equation is derived. While being equivalent to the Kadanoff-Baym and Botermans-Malfliet formulations in the range of formal applicability, it has certain advantages beyond this range. It possessesmore accurate conservation laws for Noether quantities than those in the Botermans-Malfliet formulation. At the same time the nonlocal form, similarly to the Botermans-Malfliet one, allows application of the test-particle method for its numerical solution, which makes it practical for simulations of heavy-ion collisions. The physical meaning of the time-space nonlocality is clarified. The text was submitted by the authors in English.     

Relativistic kinetic theory of quantum systems: II. Neutrino-antineutrino system

It is shown that the macroscopic current density and energy-momentum density of a neutrino-antineutrino system may be expressed in terms of moments of two scalar Wigner functions, provided that the system is homogeneous on the scale of the de Broglie wavelength of the particles. The equilibrium form of these Wigner functions is established.     

On the quantum langevin equation

The quantum Langevin equation is the Heisenberg equation of motion for the (operator) coordinate of a Brownian particle coupled to a heat bath. We give an elementary derivation of this equation for a simple coupled-oscillator model of the heat bath.Deceased.     

A generalized quantum kinetic equation for models of relativistic nuclear dynamics

Zubarev’s method of non-equilibrium statistical operator is applied to problems of relativistic kinetic theory. Within this method, a generalized relativistic quantum kinetic equation for the relativistic Wigner function is derived with taking into account the drift term of the Vlasov type and the collision integral of the second order in particle interaction. It is shown that this result holds as well for gauge invariant theories in the case of slowly changing fields. An advantage of the developed approach is exemplified by the consideration of relativistic nuclear matter within the Walecka and Nambu-Jona-Lasinio models. Typical relativistic effects like retardation, spin degrees of freedom and antiparticle evolution are taken into consideration.