Fluctuations, correlations and non-extensivity

The present status of investigations on fluctuations and correlations seen in high energy multiparticle production processes made using the notion of nonextensivity is reviewed.Comment: Minireview presented at XXXVI International Symposium on Multiparticle Dynamica, September 2-8, 2006, Paraty (RJ), Brazil; to be published in Braz. J. Phys. (2007). Some misprints correcte

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/dissipative correspondence in relativistic hydrodynamics

We argue that there is profound correspondence (the nonextensive/dissipative correspondence - NexDC) between the perfect nonextensive hydrodynamics and the usual dissipative hydrodynamics which leads to simple expression for dissipative entropy current.Comment: 4 pages, presented at Symposium NFQCD08 at Kyoto; will be published in Progress of Theoretical Physics (PTP) Supplemen

Self-similarity in jet events following from p-p collisions at LHC

Using a Tsallis nonextensive approach, we simultaneously analyze recent data obtained by the LHC ATLAS experiment on distributions of transverse momenta of jets, p_T^{jet}, together with distributions of transverse momenta of particles produced within these jets (defined relative to the jet's axis), p_T^{rel}, and their multiplicity distributions, P(N). The respective nonextensivity parameters for distributions of jets, q_{jet}, for distributions of particles in jets, q_{rel} and the global nonextensivity parameter obtained from P(N), q_N, were then compared with nonextensivity parameters q obtained from minimum bias pp collisions at energies corresponding to the energies of these jets. The values of the corresponding nonextensivity parameters were found to be similar, strongly indicating the existence of a common mechanism behind all these processes. We tentatively identify this as a self-similarity property known to be present there and resulting in Tsallis type distributions. If confirmed, this would considerably strengthen the nonextensive Tsallis approach.Comment: 7 pages, 5 figures; to be published in Phys. Lett.

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