Pion quasiparticles and QCD phase transitions at finite temperature and isospin density from holography

Abstract

Spectra of pions, which are known as the pseudo-Goldstone bosons of spontaneous chiral symmetry breaking, as well as their relationship with chiral phase transition and pion superfluidity phase transition, have been investigated in the framework of softwall AdS/QCD. In chiral limit, it is proved both numerically and analytically that pions are massless Goldstone bosons even at finite temperature, which was usually considered as an assumption in soft-wall models. Above T c , at which chiral condensate qq vanishes, the spectra of pions and scalar mesons merge together, showing the evidence of the restored chiral symmetry in hadronic spectrum level. Extending to finite quark mass, pion masses increase with quark mass. Further, it is more interesting to observe that the pole masses of pions decrease with temperature below T c , which agrees with the analysis in Phys.Rev. Lett.88(2002)202302. Meanwhile, symmetry restoration above T c could be seen in the spectra of scalar and pseudoscalar mesons. With finite temperature and isospin chemical potential µ I , it is shown that the masses of charged pions would split. The mass of positive charged pion π + decreases almost linearly to zero when µ I grows to µ c I , where pion condensation starts to form. This reveals the Goldstone nature of π + after pion superfluidity transition, which are closely related to the experimental observation.

Fluctuation and dissipation within a deformed holographic model with backreaction

“…Making use of this correspondence many works were done in order to study hot dense QGP [19][20][21][22][23][24], considering finite chemical potentials (or some related topics as for instance, QCD phase transition, chiral symmetry breaking, critical exponents, etc. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]) and quantum or thermal fluctuations such as the Brownian motion [40][41][42][43][44][45][46], fluctuation and dissipation [47][48][49][50][51][52][53][54][55], drag forces [56][57][58][59][60], or related topics [61][62][63][64][65][66].…”

Running coupling constant at finite chemical potential and magnetic field from holography *

“…The unique advantage of holography makes it possible for us to study the various properties of the QGP through weaklycoupled gravitational theory. With the development of holographic QCD, the QCD phase transition [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45], glueball and meson spectra [46][47][48][49][50][51][52][53][54], heavy quark potential [55][56][57][58][59][60], jet quenching [61][62][63][64][65][66][67] and many aspects of QCD have been studied both from top-down and bottom-up models in the last 20 years.…”

Running coupling constant at finite chemical potential and magnetic field from holography

“…The unique advantage of holography make it possible for us to study the various properties of the quark-gluon plasma(QGP) through weakly coupled gravitational theory. With the development of holo-graphic QCD, the QCD phase transition [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44], glueball and meson spectra [45][46][47][48][49][50][51][52][53], heavy quark potential [54][55][56][57][58][59], jet quenching [60][61][62][63][64][65][66] and many aspects of QCD have been studied both from top-down and bottom-up models in recent 20 years.…”