Gravitational Condensate Stars: An Alternative to Black Holes

TL;DR

To address black hole singularities and the information paradox, the paper proposes gravitational condensate stars (gravastars) as horizonless endpoints of collapse. It constructs a static, spherically symmetric solution with a de Sitter interior, a thin p=ρ shell, and an exterior Schwarzschild region, ensuring metric continuity at the interfaces and a non-vanishing but tiny boundary layer. The interior vacuum energy replaces the would-be horizon, yielding no singularity or horizon, while the shell carries entropy S ∼ a k_B M ℓ/ħ and the total entropy is far below the Bekenstein-Hawking bound. The authors prove thermodynamic stability (and thus dynamical stability) and discuss observational implications, including possible surface excitations and gravitational-wave echoes, with extensions to rotating configurations and a dynamical EFT framework for vacuum energy.

Abstract

A new solution for the endpoint of gravitational collapse is proposed. By extending the concept of Bose-Einstein condensation to gravitational systems, a cold, compact object with an interior de Sitter condensate phase and an exterior Schwarzschild geometry of arbitrary total mass M is constructed. These are separated by a phase boundary with a small but finite thickness of fluid with eq. of state p= +rho, replacing both the Schwarzschild and de Sitter classical horizons. The new solution has no singularities, no event horizons, and a global time. Its entropy is maximized under small fluctuations and is given by the standard hydrodynamic entropy of the thin shell, instead of the Bekenstein-Hawking entropy. Unlike black holes, a collapsed star of this kind is thermodynamically stable and has no information paradox.