Nonextensive quasiparticle description of QCD matter

The dynamics of QCD matter is often described using effective mean field (MF) models based on Boltzmann-Gibbs (BG) extensive statistics. However, such matter is normally produced in small packets and in violent collisions where the usual conditions justifying the use of BG statistics are not fulfilled and the systems produced are not extensive. This can be accounted for either by enriching the original dynamics or by replacing the BG statistics by its nonextensive counterpart described by a nonextensivity parameter $q\neq 1$ (for $q \to 1$ one returns to the extensive situation). In this work we investigate the interplay between the effects of dynamics and nonextensivity. Since the complexity of the nonextensive MF models prevents their simple visualization, we instead use some simple quasi-particle description of QCD matter in which the interaction is modelled phenomenologically by some effective fugacities, $z$. Embedding such a model in a nonextensive environment allows for a well-defined separation of the dynamics (represented by $z$) and the nonextensivity (represented by $q$) and a better understanding of their relationship.Comment: Thorougly reworked version published in Symmetry 2019, 11(3), 401, as contribution to the Special Issue Nambu--Jona-Lassinio model and its applications; 22 pages, 7 figure

Nonextensive statistical effects in the hadron to quark-gluon phase transition

We investigate the relativistic equation of state of hadronic matter and quark-gluon plasma at finite temperature and baryon density in the framework of the nonextensive statistical mechanics, characterized by power-law quantum distributions. We study the phase transition from hadronic matter to quark-gluon plasma by requiring the Gibbs conditions on the global conservation of baryon number and electric charge fraction. We show that nonextensive statistical effects play a crucial role in the equation of state and in the formation of mixed phase also for small deviations from the standard Boltzmann-Gibbs statistics.Comment: 13 pages, 10 figure

Nonextensive Nambu Jona-Lasinio model of QCD matter revisited

We present a revisited version of the nonextensive QCD-based Nambu - Jona-Lasinio (NJL) model describing the behavior of strongly interacting matter proposed by us some time ago. As before, it is based on the nonextensive generalization of the Boltzmann-Gibbs (BG) statistical mechanics used in the NJL model to its nonextensive version based on Tsallis statistics, but this time it fulfils the basic requirements of thermodynamical consistency. Different ways in which this can be done, connected with different possible choices of the form of the corresponding nonextensive entropies, are presented and discussed in detail. The corresponding results are compared, discussed and confronted with previous findings.Comment: 16 pages, 18 figures minor revision, to be published in EPJ

Many-body q-exponential distribution prescribed by factorization hypothesis

The factorization problem of $q$-exponential distribution within nonextensive statistical mechanics is discussed on the basis of Abe's general pseudoadditivity for equilibrium systems. it is argued that the factorization of compound probability into product of the probabilities of subsystems is nothing but the consequence of existence of thermodynamic equilibrium in the interacting systems having Tsallis entropy. So the factorization does not needs independent noninteracting systems and should be respected in all exact calculations concerning interacting nonextensive subsystems. This consideration makes it legitimate to use $q$-exponential distribution either for composite system or for single body in many-body systems. Some known results of ideal gases obtained with additive energy are reviewed.Comment: 13 pages, no figure, RevTe

Quasicanonical Gibbs distribution and Tsallis nonextensive statistics

We derive and study quasicanonical Gibbs distribution function which is characterized by the thermostat with finite number of particles (quasithermostat). We show that this naturally leads to Tsallis nonextensive statistics and thermodynamics, with Tsallis parameter q is found to be related to the number of particles in the quasithermostat. We show that the chi-square distribution of fluctuating temperature used recently by Beck can be partially understood in terms of normal random momenta of particles in the quasithermostat. Also, we discuss on the importance of the time scale hierarchy and fluctuating probability distribution functions in understanding of Tsallis distribution, within the framework of kinetics of dilute gas and weakly inhomogeneous systems.Comment: 22 pages, 1 eps-figur

Nonextensive statistics: Theoretical, experimental and computational evidences and connections

The domain of validity of standard thermodynamics and Boltzmann-Gibbs statistical mechanics is discussed and then formally enlarged in order to hopefully cover a variety of anomalous systems. The generalization concerns {\it nonextensive} systems, where nonextensivity is understood in the thermodynamical sense. This generalization was first proposed in 1988 inspired by the probabilistic description of multifractal geometries, and has been intensively studied during this decade. In the present effort, after introducing some historical background, we briefly describe the formalism, and then exhibit the present status in what concerns theoretical, experimental and computational evidences and connections, as well as some perspectives for the future. In addition to these, here and there we point out various (possibly) relevant questions, whose answer would certainly clarify our current understanding of the foundations of statistical mechanics and its thermodynamical implicationsComment: 15 figure

Tsallis Ensemble as an Exact Orthode

We show that Tsallis ensemble of power-law distributions provides a mechanical model of nonextensive equilibrium thermodynamics for small interacting Hamiltonian systems, i.e., using Boltzmann's original nomenclature, we prove that it is an exact orthode. This means that the heat differential admits the inverse average kinetic energy as an integrating factor. One immediate consequence is that the logarithm of the normalization function can be identified with the entropy, instead of the q-deformed logarithm. It has been noted that such entropy coincides with Renyi entropy rather than Tsallis entropy, it is non-additive, tends to the standard canonical entropy as the power index tends to infinity and is consistent with the free energy formula proposed in [S. Abe et. al. Phys. Lett. A 281, 126 (2001)]. It is also shown that the heat differential admits the Lagrange multiplier used in non-extensive thermodynamics as an integrating factor too, and that the associated entropy is given by ordinary nonextensive entropy. The mechanical approach proposed in this work is fully consistent with an information-theoretic approach based on the maximization of Renyi entropy.Comment: 5 pages. Added connection with Renyi entrop

Nonlinear statistical effects in relativistic mean field theory

We investigate the relativistic mean field theory of nuclear matter at finite temperature and baryon density taking into account of nonlinear statistical effects, characterized by power-law quantum distributions. The analysis is performed by requiring the Gibbs conditions on the global conservation of baryon number and electric charge fraction. We show that such nonlinear statistical effects play a crucial role in the equation of state and in the formation of mixed phase also for small deviations from the standard Boltzmann-Gibbs statistics.Comment: 9 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:1005.4643 and arXiv:0912.460