Formation of correlations and energy-conservation at short time scales

The formation of correlations due to collisions in an interacting nucleonic system is investigated. Results from one-time kinetic equations are compared with the Kadanoff and Baym two-time equation with collisions included in Born approximation. A reasonable agreement is found for a proposed approximation of the memory effects by a finite duration of collisions. This form of collision integral is in agreement with intuitive estimates from Fermi's golden rule. The formation of correlations and the build up time is calculated analytically for the high temperature and the low temperature limit. Different approximate expressions are compared with the numerical results. We present analytically the time dependent interaction energy and the formation time for Gau\ss{}- and Yukawa type of potentials.Comment: Europ. Lournal Physics A accepte

Correlations in Many-Body Systems with Two-time Green's Functions

The Kadanoff-Baym (KB) equations are solved numerically for infinite nuclear matter. In particular we calculate correlation energies and correlation times. Approximating the Green's functions in the KB collision kernel by the free Green's functions the Levinson equation is obtained. This approximation is valid for weak interactions and/or low densities. It relates to the extended quasi-classical approximation for the spectral function. Comparing the Levinson, Born and KB calculations allows for an estimate of higher order spectral corrections to the correlations. A decrease in binding energy is reported due to spectral correlations and off-shell parts in the reduced density matrix

An optical linewidth study of a chromoprotein-C-phycocyanin in a low-temperature glass

The temperature dependence of spectral holes burnt into a phycocyanin-doped ethylene glycol/water glass is investigated in the temperature range between 1.5 and 15 K. The data are well described by a power law with an exponent of 1.16 ± 0.1. Chromoproteins thus behave very much the same as glasses doped with small impurity molecules