FERMION CONDENSATION IN A RELATIVISTIC DEGENERATE STAR: ARRESTED COLLAPSE AND MACROSCOPIC EQUILIBRIUM

Abstract

Fermionic Cooper pairing leading to the BCS-type hadronic superfluidity is believed to account for periodic variations ("glitches") and subsequent slow relaxation in spin rates of neutron stars. Under appropriate conditions, however, fermions can also form a Bose–Einstein condensate of composite bosons. Both types of behavior have recently been observed in tabletop experiments with ultra-cold fermionic atomic gases. Since the behavior is universal (i.e., independent of atomic potential) when the modulus of the scattering length greatly exceeds the separation between particles, one can expect analogous processes to occur within the supradense matter of neutron stars. In this paper, I show how neutron condensation to a Bose–Einstein condensate, in conjunction with relativistically exact expressions for fermion energy and degeneracy pressure and the relations for thermodynamic equilibrium in a spherically symmetric space–time with Schwarzschild metric, leads to stable macroscopic equilibrium states of stars of finite density, irrespective of mass.