Glimpses of black hole formation/evaporation in highly inelastic, ultra-planckian string collisions

TL;DR

This paper investigates black hole formation and evaporation signatures in ultra-planckian string collisions, comparing different theoretical approaches and suggesting that final states resemble black hole evaporation without clear thermalization evidence.

Contribution

It reconciles previous theoretical methods and proposes that ultra-planckian string collisions produce final states similar to black hole evaporation, clarifying earlier apparent discrepancies.

Findings

Final states in ultra-planckian collisions resemble black hole evaporation.

Reinterpretation of results resolves tension between different theoretical approaches.

No clear evidence of thermalization at current approximation levels.

Abstract

We revisit possible glimpses of black-hole formation by looking at ultra-planckian string-string collisions at very high final-state multiplicity. We compare, in particular, previous results using the optical theorem, the resummation of ladder diagrams at arbitrary loop order, and the AGK cutting rules, with the more recent study of $2 \rightarrow N$ scattering at $N \sim s M_P^{-2} \gg 1$. We argue that some apparent tension between the two approaches disappears once a reinterpretation of the latter's results in terms of suitably defined infrared-safe cross sections is adopted. Under that assumption, the typical final state produced in an ultra-planckian collision does indeed appear to share some properties with those expected from the evaporation of a black hole of mass $\sqrt{s}$, although no sign of thermalization is seen to emerge at this level of approximation.