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 the pion condensed phase and normal phase, as well as chiral phase transition in a two flavor ( ${\cal{N}}_f=2$ ) 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 the 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 on lattice simulations and model calculations.