A simple derivation of the Galitskii–Yakimets distribution function over momentum is presented. For dense plasmas it contains the law ∼p−8 as a quantum correction to the classical Maxwellian distribution function at large momenta. The integral equation for the width of the spectral...

The BCH formula of Rezek and Kosloff (2006) [10] is a convenient tool to handle a family of density matrices, which occurs in the study of quantum heat engines. We prove the formula using a known argument from Lie theory.

In this work we reexamine quantum electrodynamics of atomic electrons in the Coulomb gauge in the dipole approximation and calculate the shift of atomic energy levels in the context of Dalibard, Dupont-Roc and Cohen-Tannoudji formalism by considering the variation rates of physical observable....

We consider mixed states and coherent states with the same (Poissonian) statistics. By analyzing various properties connected with off-diagonal elements of the density matrix for both states, we find which of them are able (or not) to distinguish these states.

We study the adiabatic limit in the density matrix approach for a quantum system coupled to a weakly dissipative medium. The energy spectrum of the quantum model is supposed to be non-degenerate. In the absence of dissipation, the geometric phases for periodic Hamiltonians obtained previously by...

Göhmann, Klümper and Seel derived the multiple integral formula of the density matrix of the XXZ Heisenberg chain at finite temperatures. We have applied the high temperature expansion (HTE) method to isotropic case of their formula in a finite magnetic field and obtained coefficients for...