Spin Potential and Thermal Regularization in the Two‐Flavor Nambu–Jona‐Lasinio Model

ABSTRACT Recently, the spin potential has been proposed as a new thermodynamic quantity that quantifies the degree of spin alignment of quark matter along a preferred direction in lattice quantum chromodynamics (LQCD). By using this quantity, one can explore the behavior of different aspects of the QCD phase diagram and connect them with future LQCD and experimental results. Since it is a natural quantity to investigate within effective models, in this work we introduce the spin potential in the context of the two‐flavor Nambu–Jona‐Lasinio model at finite temperature and study its dependence on whether or not one regularizes the thermal contributions, an issue that has been discussed over the years in connection with the behavior of thermodynamic observables and the recovery of the Stefan–Boltzmann limit at high temperatures. To investigate these effects, we evaluate the effective quark masses as well as the pressure of the model for different spin potential values using two different prescriptions for the regularization of the thermal contributions.