The semidegenerate equilibrium configurations of a self-gravitating system of fermions have usually been treated by an expansion of the thermodynamical quantities around the fully degenerate values. It is shown that such an expansion is invalid in the low density regimes where, in general, a distribution function far from the degenerate one applies. This point is explicitly illustrated by comparing and contrasting the results based on first- and second-order expansion from the fully degenerate values with the exact ones. These exact values have been obtained by a direct computation of the Fermi integrals. It is found that, for any value of the temperature T different from 0, a system of self-gravitating fermions leads to a configuration of equilibrium with a density decreasing at large distances as rho is about 1/r^2, quite independently of the value of its central density, and, therefore, always infinite both in mass and radius.
The semidegenerate configurations of a selfgravitating system of fermions / Gao, J. G.; Merafina, Marco; Ruffini, Remo. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - STAMPA. - 235:(1990), pp. 1-7.
The semidegenerate configurations of a selfgravitating system of fermions.
MERAFINA, Marco;RUFFINI, Remo
1990
Abstract
The semidegenerate equilibrium configurations of a self-gravitating system of fermions have usually been treated by an expansion of the thermodynamical quantities around the fully degenerate values. It is shown that such an expansion is invalid in the low density regimes where, in general, a distribution function far from the degenerate one applies. This point is explicitly illustrated by comparing and contrasting the results based on first- and second-order expansion from the fully degenerate values with the exact ones. These exact values have been obtained by a direct computation of the Fermi integrals. It is found that, for any value of the temperature T different from 0, a system of self-gravitating fermions leads to a configuration of equilibrium with a density decreasing at large distances as rho is about 1/r^2, quite independently of the value of its central density, and, therefore, always infinite both in mass and radius.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.