Quark matter revisited with non-extensive MIT bag model

Abstract

In this work we revisit the MIT bag model to describe quark matter within both the usual Fermi-Dirac and the Tsallis statistics. We verify the effects of the non-additivity of the latter by analysing two different pictures: the first order phase transition of the QCD phase diagram and stellar matter properties. While, the QCD phase diagram is visually affected by the Tsallis statistics, the resulting effects on quark star macroscopic properties are barely noticed.

Fractal Structure of Hadrons: Experimental and Theoretical Signatures

“…Applications of such theory have already been made in astrophysics, where the stability of neutron stars has been studied under the light of the non-extensive thermodynamics [68], showing effects that help to understand recent observation of more massive objects of this kind. Recently, the MIT Bag Model has been extended to include the thermofractal structure described here by introducing the non-extensive distributions [69].…”

Generalized statistical mechanics of cosmic rays: Application to positron-electron spectral indices

“…QCD scattering and selfsimilar hadronic fragmentation processes have been previously successfully described by q = 1 theories [9,[16][17][18][19], and applied to data taken at LHC [23][24][25]. It is precisely these types of scattering processes that we postulate as main ingredients to imprint on the momentum spectrum of primary cosmic rays, an initial spectrum set by QCD that in its main features is basically conserved, while other important processes then only yield small perturbations of the initial spectrum set by QCD, at least in a statistical sense.…”

“…Among phenomenological approaches to understand high energy cascading scattering processes, power laws associated with Tsallis statistics are by now widely used by many groups [9,[16][17][18][19][20][21]. In fact they yield surprisingly good fits of a variety of data sets for different systems.…”

“…Recent models are now going much more in-depth on which specific type of formalism is appropriate, and relate the entropic index to QCD scattering processes in the perturbative regime [9,18]. But also the nonperturbative regime is accessible, where the generalized statistical mechanics formalism arises out of the self-similarity of the fragmentation process and can be related to the fractal-like structure of hadrons within the MIT bag model for hadron structure [16,17]. Moreover, Tsallis statistics is generally well-known to be highly relevant for velocity distributions in astrophysical plasmas (here these distributions come under the name Kappa-distributions, see, e.g., [41] for a recent review).…”

“…Probably the most popular one of these generalizations is based on q-entropy (or Tsallis entropy), which leads to power law distributions (the so-called q-exponentials), but other generalized entropic approaches are possible as well [1][2][3][4][5][6][7][8]. In high energy physics, a recent success of the q-generalized approach is that excellent fits of measured transverse momentum spectra in high energy scattering experiments have been obtained [9], based on an extension of Hagedorn's theory [10][11][12] to a q-generalized version and a generalized thermodynamic theory [13][14][15][16][17][18][19]. This includes recent experiments in the TeV region for pp and pp collisions [9,[20][21][22][23][24][25], but there is also early work on cosmic ray spectra [26,27] and e + e − annihilation [15,28,29].…”