Effects of equilibrium coexisting phases in the first-order chiral transition within the linear σ model with quarks

The first order chiral phase transition for quark matter with flavor imbalance is studied using the Linear σ model with quarks, also known as quark-meson model. Special attention is paid to the role of the scalar isovector meson. The general consensus presently is that the chiral transition changes from a smooth crossover to first-order at low temperatures. This transition is assumed to be discontinuous with unstable or metastable intermediate states. However, if multiple charges are simultaneously conserved the system could undergo a continuous change through a coexistence of equilibrium states. Under such assumption the bulk properties are analyzed and several remarkable effects for the speed of sound and the susceptibilities are stressed.