QCD phase diagram at finite isospin chemical potential and temperature in an IR-improved soft-wall AdS/QCD model

Abstract

We study the phase transition between pion condensed phase and normal phase, as well as chiral phase transition in a two flavor(${\mathcal{N}}_f=2$) IR- improved soft-wall AdS/QCD model at finite isospin chemical potential ${\mu }_I$ and temperature $T$. By self-consistently solving the equations of motion, we obtain the phase diagram in the plane of ${\mu }_I$ and $T$. The pion condensation appears together with a massless Nambu-Goldstone boson $m_{{\pi }_1}(T_c,{\mu }_I^c)=0$, which is very likely to be a second-order phase transition with mean-field critical exponents in small ${\mu }_I$ region. When $T=0$, the critical isospin chemical potential approximates to vacuum pion mass ${\mu }_I^c\approx m_0$. The pion condensed phase exists in an arched area and the boundary of the chiral crossover intersects the pion condensed phase at a tri-critical point. Qualitatively, the results are in good agreement with previous studies from Lattice simulations and model calculations.

Comments: 11 pages, 6 figures