Thermal gravity, black holes and cosmological entropy

TL;DR

This paper explores the possibility that thermal gravitons can undergo a phase transition into a black hole condensate, which could explain the universe's low entropy state and relate to Penrose's observations.

Contribution

It proposes a new phase transition mechanism for thermal gravitons into black hole condensates, linking thermodynamics, quantum gravity, and cosmology.

Findings

Black hole nucleation rate is governed by saddlepoint free energy.

The universe's entropy state depends on its thermal history.

Potential explanation for the universe's low entropy state.

Abstract

Taking seriously the interpretation of black hole entropy as the logarithm of the number of microstates, we argue that thermal gravitons may undergo a phase transition to a kind of black hole condensate. The phase transition proceeds via nucleation of black holes at a rate governed by a saddlepoint configuration whose free energy is of order the inverse temperature in Planck units. Whether the universe remains in a low entropy state as opposed to the high entropy black hole condensate depends sensitively on its thermal history. Our results may clarify an old observation of Penrose regarding the very low entropy state of the universe.