Non-Markovian electron-phonon relaxation

Kinetic equations describing short-time evolution of the electron-phonon system are derived in non-Markovian Born approximation by the density matrix method. The approach presented in the paper differs from earlier schemes in that the interaction energy is treated as an independent state parameter on the same footing as the electron and phonon distribution functions. This introduces new correlation terms into the kinetic equations, which ensure the energy conservation and the existence of the correct equilibrium solution. An explicit expression for the time-dependent correlation energy is obtained.За допомогою методу матриці густини в немарковському борнівському наближенні отримано кінетичні рівняння, що описують короткочасову еволюцію електрон-фононної системи. Запропонований у цій статті підхід відрізняється від попередніх схем тим, що енергія взаємодії вважається незалежним параметром стану нарівні з електронною та фононною функціями розподілу. За рахунок цього у кінетичних рівняннях виникають нові кореляційні члени, що забезпечують збереження енергії та існування правильного рівноважного розв’язку. Отримано явний вираз для залежної від часу кореляційної енергії

CARS diagnostics of near-critical fluid in small mesopores

Due to the high spacial resolution and theinterference nature, coherent anti-Stokes Ramanscattering (CARS) spectroscopy is well suited forthe diagnostics of composites based on transparentnanoporous hosts. In particular, the adsorption of afluid on the walls of nanopores and the formation ofa condensed phase in their volume leads to obvioustransformation of the CARS spectra. Recently wehave developed a model which describes thebehavior of molecular spectra at isothermalcompression in cylindrical nanopores. Calculationsbased on the model have shown a good agreementwith the experimental results for carbon dioxide innanoporous glass with pores of diameter of severalnanometers. Here we use the developed approach toinvestigate the phase behavior of carbon dioxide inglass nanopores at near-critical temperatures. It hasbeen experimentally shown that condensation innanopores occurs at relatively low pressures atsubcritical and even at supercritical temperatures.The analysis based on the developed model allowsto reveal some qualitative and quantitativecharacterizations of the shift of critical point

Covariant Linear Response Theory of Relativistic QED Plasmas

We start from the QED Lagrangian to describe a charged many-particle system coupled to the radiation field. A covariant density matrix approach to kinetic theory of QED plasmas, subjected to a strong external electro-magnetic field has recently been developed [1,2]. We use the hyperplane formalism in order to perform a manifest covariant quantization and to implement initial correlations to the solution of the Liouville-von Neumann equation. A perturbative expansion in orders of the fine structure constant for the correlation functions as well as the statistical operator is applied. The non-equilibrium state of the system is given within generalized linear response theory. Expressions for the susceptibility tensor, describing the plasma response, are calculated within different approximations, like the RPA approximation or considering collisions within the Born-approximation. In particular, the process of relativistic inverse bremsstrahlung in a plasma is discussed.Comment: Latex 39 pages, 4 figure

Effects of Concentration Titanium on Threshold Character of Deuterium Desorption Temperature Range from Mg-based Composites

The plasma evaporation-sputtering method was applied to make composite materials of the Mg-Ti system. The ion-implanted deuterium desorption temperature variations as a function of the component concentration were studied. It has been established that, by introducing titanium into magnesium, the deuterium desorption temperature can be appreciably decreased (to 400-450 K) in comparison with the case of deuterium desorption from magnesium ( 800 K). A step-like shape of the curve of deuterium desorption temperature evidences on the presence of two different structure states of the Mg-Ti system depending on the ratio of components. The deuterium temperature decrease can be caused by filamentary inclusions of insoluble component (titanium) atoms formed in the process of composite making and annealing, providing the deuterium diffusion from the sample at a lower temperature (channels for deuterium diffusion through the surface barrier). The deuterium desorption data obtained on the example of Mg-Ti, Mg-V and Mg-Zr composites provide support for further research into hydrogen storage materials containing low-soluble chemical elements in the alloy component. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3550

The ``Mixed'' Green's Function Approach to Quantum Kinetics with Initial Correlations

A method for deriving quantum kinetic equations with initial correlations is developed on the basis of the nonequilibrium Green's function formalism. The method is applicable to a wide range of correlated initial states described by nonequilibrium statistical thermodynamics. Initial correlations and the real-time evolution are treated by a unified technique employing many-component ``mixed'' Green's functions. The Dyson equation for the mixed Green's function leads to a set of equations for real-time Green's functions and new (cross) components linking initial correlations with dynamical processes. These equations are used to formulate a generalized Kadanoff-Baym ansatz for correlated initial states. A non-Markovian short-time kinetic equation is derived within the T-matrix approximation for the self-energies. The properties of the memory kernels in this equation are considered in detail in Born approximation for the T-matrices. The kinetic equation is demonstrated to conserve the total energy of the system. An explicit expression for the time-dependent correlation energy is obtained.Comment: 50 pages, 3 figure

Structural Relaxation and Frequency Dependent Specific Heat in a Supercooled Liquid

We have studied the relation between the structural relaxation and the frequency dependent thermal response or the specific heat, $c_p(\omega)$, in a supercooled liquid. The Mode Coupling Theory (MCT) results are used to obtain $c_p(\omega)$ corresponding to different wavevectors. Due to the two-step relaxation process present in the MCT, an extra peak, in addition to the low frequency peak, is predicted in specific heat at high frequency.Comment: 14 pages, 13 Figure

Enskog-Landau kinetic equation. Calculation of the transport coefficients for charged hard spheres

Using charged hard spheres model as an example, the dense one-component plasma is considered. For this model the Enskog-Landau kinetic equation is obtained and its normal solution is found using the Chapman-Enskog method. Transport coefficients are obtained numerically and analytically and compared with the experimental data available.Comment: 13 LaTeX209 pages, 4 figures (emline-format for LaTeX

Revised data on γ-families observed in X-ray emulsion chambers of the Experiment PAMIR

Recently essential efforts were made to improve measurement routine with X-ray films exposed in the X-ray emulsion chambers at the Pamirs. Analysis of X-ray emulsion response upon recorded events show that γ-family energy and intensity in early publications were over estimated. The main physical results of the new analysis are presented