To fluctuation theory in statistical mechanics of nonextensive systems

A. K. Rajagopal

Rinat G. Zaripov

Luca Salasnich

We discuss the Bose-Einstein condensation (BEC) for an ideal gas of bosons in the framework of Tsallis’s nonextensive statistical mechanics. We study the corrections to the standard BEC formulas due to a weak nonextensivity of the system. In particular, we consider three cases in the D-dimensional space: the homogeneous gas, the gas in a harmonic trap and the relativistic homogenous gas. The results show that small deviations from the extensive Bose statistics produce remarkably large changes in the BEC transition temperature. PACS numbers: 05.30-d; 03.75.Fi 1 A decade ago, Tsallis introduced a nonextensive statistical mechanics (NSM) to describe systems for which the additivity property of entropy does not hold. 1 The NSM can describe systems for which long-range microscopic memory, fractal space-time constraints or long-range interactions affect the thermalization process. 2 The NSM is characterized by a parameter q such

B. Tanatar

We study the Bose-Einstein condensation (BEC) phenomenon in an interacting trapped Bose gas using the semiclassical two-fluid model and nonextensive statistical mechanics. The effects of nonextensivity characterized by a parameter are explored by calculating the temperature dependent thermodynamic properties, fraction of condensed particles, and density distributions of condensed and thermal components of the system. It is found that nonextensivity in the underlying statistical mechanics may have large effects on the BEC transition temperature.

Sergei Vladimirovich Tyablikov

А. В. Колесниченко

Abstract A dynamic theory of the linear reaction from nonextensive quasi-equilibrium multibody systems to an external time-dependent perturbation is developed in quantum statistical mechanics based on the Tsallis parametric nonadditive entropy associated with the density matrix. For nonextensive quantum systems, a modification of the Kubo theory developed in quantum mechanics is proposed. The linear reaction theory is constructed based on a generalized canonical form of the density matrix obtained by maximizing the Tsallis quantum entropy by averaging the observed values over the escort distribution. Generalized expressions for admittance and response functions are presented that describe the linear response of the system to a weak external mechanical impact. The paper discusses the symmetry property for the relaxation function under time reversal and the Onsager reciprocity relation for generalized susceptibility. It is shown that these properties known in classical quantum statistics remain valid for anomalous systems.