Speaker
Description
Understanding the thermodynamic evolution of strongly interacting matter requires an equation of state connecting hadronic and partonic degrees of freedom. The transition between hadronic and partonic phases at very small baryon chemical potential is known to be smooth crossover. To map this region we construct a hybrid equation of state by pressure interpolation between an ideal hadron resonance gas and an ideal parton gas. The framework is generalized to finite baryon chemical potential, a 2+1-flavor QGP, and finite magnetic field, with thermodynamic observables derived consistently from the interpolated pressure. We construct the coupled evolution of temperature and baryon chemical potential in an ideal longitudinal expansion by imposing conservation of entropy and net baryon number, and obtain the corresponding isentropic trajectories using a fourth-order Runge-Kutta method. The modification of these trajectories and of the crossover thermodynamics by a finite magnetic field is investigated. Multiple isentropic trajectories are used to characterize the thermodynamic crossover region in the $T-\mu_B$ plane through the behavior of the equation of state and its response functions. The framework provides a unified description of equilibrium thermodynamics and isentropic evolution of QCD matter, allowing the interplay of baryon density and magnetic field to be explored across the crossover region.