Delta isobars in relativistic mean-field models with $\sigma$-scaled hadron masses and couplings

Abstract

We extend the relativistic mean-field models with hadron masses and meson-baryon coupling constants dependent on the scalar $\sigma$ field, studied previously to incorporate $\Delta(1232)$ baryons. Available empirical information is analyzed to put constraints on the couplings of $\Delta$s with meson fields. Conditions for the appearance of $\Delta$s are studied. We demonstrate that with inclusion of the $\Delta$s our equations of state continue to fulfill majority of known empirical constraints including the pressure-density constraint from heavy-ion collisions, the constraint on the maximum mass of the neutron stars, the direct Urca and the gravitational-baryon mass ratio constraints.