Narrow Results

We estimate in this work the contribution of the nucleon weak magnetism on the neutrino absorption mean free path inside high density nuclear matter. Our main contribution to this subject involves basically, in the mean field approach, three different ingredients: (a) a relativistic generalization of the approach developed by Sanjay and collaborators; (b) the inclusion of the nucleon weak-magnetism; (c) the inclusion of the pseudo-scalar interaction involving the nucleons. Our preliminary results indicate the consistency of our approach. The novel results we have obtained, considering similar physical conditions as the ones assumed by Sanjay and collaborators, is that the neutrino absorption mean free path is three times the corresponding result obtained by those authors.

The diffusion coefficients that are related to the neutrino opacities are calculated in such a way that the formation of nuclear pasta and homogeneous matter at low densities are taken into account. Two methods are developed to build the pasta phase and their differences are outlined. One of them is chosen as part of a complete equation of state used in the calculation of the diffusion coefficients. Our results show that the mean free paths are significantly altered by the presence of nuclear pasta in stellar matter when compared with the results obtained with pure homogeneous matter. These differences in neutrino opacities will have consequences in the calculation of the Kelvin-Helmholtz phase of protoneutron stars.