Effects of Born-Infeld Electrodynamics on Chiral Symmetry Restoration and Meson Susceptibilities in Holographic QCD

Abstract

Within a holographic QCD framework, we numerically investigate chiral symmetry breaking and the associated phase transition at finite temperature and chemical potential. The model is constructed on a nonlinear charged Born-Infeld black hole background. The chiral condensate, extracted from the asymptotic behavior of the bulk scalar field, serves as the primary order parameter. At zero chemical potential, we find a chiral crossover transition for physical quark masses with a pseudocritical temperature of $T_{pc}=0.1477$ GeV. In the chiral limit, the transition becomes first-order with a critical temperature of $T_{c}=0.1337$ GeV. A critical strange quark mass of $m_s=37$ MeV, at zero light quark mass, separates first- and second-order transition regions. For finite chemical potential ($\mu$) and a physical strange mass ($m_s=95$ MeV) with massless light quarks, the transition remains second-order, with $T_c$ decreasing as $\mu$ increases. These results are further supported by the behavior of meson susceptibilities $(\chi_{\pi}-\chi_{\sigma})$, which exhibit a rapid thermal decay and convergence across the phase boundary. Introducing the Born-Infeld parameter $\beta$ shifts the second-order phase boundary to higher temperatures for smaller $\beta$ (stabilizing the chirally broken phase) but does not alter the transition order or introduce a critical endpoint within the studied range. Our findings are consistent with previous soft-wall model studies and highlight the significant role of nonlinear bulk electrodynamics in modifying the chiral phase diagram.