Condensates in the Cosmos: Quantum Stabilization of Degenerate Stars

Abstract

Stars that have exhausted their nuclear fuel are believed to end up as white dwarfs, neutron (or hybrid neutron-quark) stars, or black holes depending on their mass. In general relativity, which is a classical theory, a black hole is a singularity in space detectable only through its gravitational field, where the laws of physics break down. The author discusses various quantum processes whose intervention in stellar collapse would avoid this nonphysical fate and lead to an equilibrium state of macroscopic size and finite density. One possibility is the condensation of neutrons (which are fermions) into a coherent ground-state system of composite bosons. Another possibility entails a neutron ferromagnetic transition under the influence of an ultra-strong magnetic field, such as is known to occur in neutron stars. In a third possibility, the author shows how gravitationally-induced resorption of neutrons into the quantum vacuum, a process complementary to Hawking radiation, can lead to stable equilibrium. If any of these processes occurs, then stellar black holes either do not exist or exist as a finitely extended body within their Schwarzschild surface.