MG14 - Talk detail

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Abstract

A large variety of astrophysical systems can be described in terms of fermionic matter, and some of the most important examples are represented by white dwarfs, neutron stars and galactic dark halos. Nevertheless the presence of anisotropies, in the distribution of the motion of the particles, could explain some particular features (e.g. the super Chandrasekhar white dwarfs). In this talk, a spherical system composed by a semidegenerate Fermi gas in the General Relativistic framework is discussed. To avoid infinite solutions in masses and radii (astrophysical objects are limited), the Fermi - Dirac distribution function is modified by the presence of a cutoff term. Moreover, in order to study the effects of the anisotropy due to the prevalence of tangential motion, a term depending on the angular momentum is included in the distribution function. Once solved the equations of the gravitational equilibrium, it is possible to describe a lot of different physical situations, by changing the values of the parameters characterizing the model. The analysis is further extended to the classical and the fully degenerate regimes. The problem of the dynamical stability is also considered by advancing a general criterion, for the anisotropic systems, in terms of the polytropic exponent. Finally, some applications of this criterion are showed.

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