Nonextensive effects on QCD chiral phase diagram and baryon-number fluctuations within Polyakov-Nambu-Jona-Lasinio model

In this paper,a version of the Polyakov-Nambu-Jona-Lasinio(PNJL)model based on nonextensive statistical mechanics is presented.This new statistics summarizes all possible factors that violate the assumptions of the Boltzmann-Gibbs(BG)statistics to a dimensionless nonextensivity parameter q.Thus,when q tends to 1,it returns to the BG case.Within the nonextensive PNJL model,we found that as q increases,the location of the critical end point(CEP)exhibits non-monotonic behavior.That is,for q<1.15,CEP moves in the direction of lower temperature and larger quark chemical potential.However,for q>1.15,CEP turns to move in the direction of lower temperature and lower quark chemical potential.In addition,we studied the moments of the net-baryon number distribution,that is,variance(σ^(2)),skewness(S),and kurtosis(k).Our results are generally consistent with the latest experimental data reported,especially for√SNN>19.6 GeV,when q is set to 1.07.

QCD chiral phase transition and critical exponents within the nonextensive Polyakov-Nambu-Jona-Lasinio model

We present a nonextensive version of the Polyakov-Nambu-Jona-Lasinio model that is based on nonextentive statistical mechanics.This new statistics model is characterized by a dimensionless nonextensivity parameter q that accounts for all possible effects violating the assumptions of the Boltzmann-Gibbs(BG) statistics(for q→ 1,it returns to the BG case).Based on the nonextensive Polyakov-Nambu-Jona-Lasinio model,we discussed the influence of nonextensive effects on the curvature of the phase diagram at μ=0 and especially on the location of the critical end point(CEP).A new and interesting phenomenon we found is that with an increase in q,the CEP position initially shifts toward the direction of larger chemical potential and lower temperature.However,when q is larger than a critical value qc,the CEP position moves in the opposite direction.In other words,as q increases,the CEP position moves in the direction of smaller chemical potential and higher temperature.This U-turn phenomenon may be important for the search of CEP in relativistic heavy-ion collisions,in which the validity of BG statistics is questionable due to strong fluctuations and long-range correlations,and nonextensive effects begin to manifest themselves.In addition,we calculated the influence of the nonextensive effects on the critical exponents and found that they remain almost constant with q.

Nonextensive effects on QCD chiral phase transition with a chiral chemical potential

In this study,we investigate the QCD chiral phase diagram in the presence of a chiral chemical potential μ based on nonextensive statistical mechanics.A feature of this new statistic is a dimensionless nonextensivity parameter q,which summarizes all possible effects violating the assumptions of Boltzmann-Gibbs(BG)statistics(when q→1,it returns to the BG case).Within the nonextensive Polyakov-Nambu-Jona-Lasinio model,we find that as μ increases,the critical end point(CEP)in the T-μ plane continues to CEP_(5)in the T-μ plane,and nonextensive effects have a significant impact on the evolution from the CEP to CEP_(5).Generally,with an increase in q,both the CEP and CEP_(5)move in the direction of a lower temperature T and larger chemical potentialμ(μ_(5)).In addition,we find that chiral charge density ngenerally increases with T,μ,μ_(5),and q.Our study may provide useful hints about lattice QCD and relativistic heavy-ion collision experiments.