In this work we obtained the equation of state to be used to study the structure of neutron protostars. To this end, we adopt the nonlinear Walecka model in the mean field approximation. In this model the equation of state is the octet of baryons of spin 1/2 (n, p, Λ0, Σ−, Σ0, Σ+, Ξ−, Ξ0) and baryonic resonances of spin 3/2, represented by the delta matter (∆−, ∆0, ∆+, ∆++ ) and Ω− in the baryonic sector. In the leptonic sector we consider the electrons, muons and the corresponding trapped neutrinos. Thus, we studied the effects of neutrinos on the equation of state in the initial instants of the formation of a neutron star. We discussed the structure of the neutron
protostar including the delta resonances in its composition, and compared the results in the phase of cooling induced by the escape of neutrinos. Coupling constants between hiperons Λ, Σ, and Ξ and mesons ω and ρ are determined using the SU(6) and the coupling constants hiperons-σ are determined by the consistency of the hipernuclear potential in the nuclear matter. In addition, we use the possible values of the coupling constants through the delta-meson QCD sum rules to finite density. Using the equation of state obtained with this model, we solve numerically the equation TOV (Tolman-Oppenheimer-Volkoff) and so we obtained the values of the maximum mass of the star before and after cooling.
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