Unitarity restoring graviton radiation in the collapse regime of scattering

TL;DR

This paper explores how graviton radiation at high energies and small impact parameters can restore unitarity in gravitational scattering, potentially indicating quantum black hole signals through energy emission and damping effects.

Contribution

It demonstrates that graviton radiation outside the trapped region can compensate for energy loss, suggesting a unitarity-preserving mechanism in high-energy gravitational scattering.

Findings

Gravitons can be efficiently produced in the untrapped region.

Energy radiation compensates for trapped energy, avoiding suppression.

Radiation develops an exponential frequency damping related to Hawking radiation.

Abstract

We investigate graviton radiation in gravitational scattering at small impact parameters $b<R\equiv 2G\sqrt{s}$ and extreme energies $s\gg M_P^2$, a regime in which classical collapse is thought to occur, and thus radiation may be suppressed also. Here however, by analyzing the soft-based representation of radiation recently proposed in the semiclassical ACV framework, we argue that gravitons can be efficiently produced in the untrapped region $|\boldsymbol{x}|\gtrsim R>b$, so as to suggest a possible completion of the unitarity sum. In fact, such energy radiation at large distances turns out to compensate and to gradually reduce to nothing the amount of energy $E'$ being trapped at small-$b$'s, by thus avoiding the quantum tunneling suppression of the elastic scattering and suggesting a unitary evolution. We finally look at the coherent radiation sample so obtained and we find that, by energy conservation, it develops an exponential frequency damping corresponding to a "quasi-temperature" of order $\hbar/R$, which is naturally related to a Hawking radiation and is suggestive of a black-hole signal at quantum level.