Backreaction of Hawking Radiation on a Gravitationally Collapsing Star I: Black Holes?

TL;DR

This paper explores how Hawking radiation's negative energy flux can halt a collapsing star's formation of a black hole, causing it to bounce before an event horizon or singularity develop.

Contribution

It demonstrates that Hawking radiation can induce a bounce in collapsing stars, preventing black hole formation under certain initial vacuum conditions.

Findings

Collapse stops at finite radius due to negative energy Hawking radiation.

Star bounces instead of forming a singularity or event horizon.

A temporary trapped surface may form during the bounce.

Abstract

Particle creation leading to Hawking radiation is produced by the changing gravitational field of the collapsing star. The two main initial conditions in the far past placed on the quantum field from which particles arise, are the Hartle Hawking vacuum and the Unruh vacuum. The former leads to a time symmetric thermal bath of radiation, while the latter to a flux of radiation coming out of the collapsing star. The energy of Hawking radiation in the interior of the collapsing star is negative and equal in magnitude to its value at future infinity. This work investigates the backreaction of Hawking radiation on the interior of a gravitationally collapsing star, in a Hartle-Hawking initial vacuum. It shows that due to the negative energy Hawking radiation in the interior, the collapse of the star stops at a finite radius, before the singularity and the event horizon of a black hole have a chance to form. That is, the star bounces instead of collapsing to a black hole. A trapped surface near the last stage of the star's collapse to its minimum size may still exist temporarily. Its formation depends on the details of collapse. Results for the case of Hawking flux of radiation with the Unruh initial state, will be given in a companion paper II.