Classicalization of Gravitons and Goldstones

TL;DR

This paper draws a parallel between graviton and scalar classicalization, showing that high-energy scattering leads to classical configurations with entropy-like properties, suggesting classicalization as a universal unitarization mechanism.

Contribution

It demonstrates that scalar theories can classicalize similarly to gravitons, providing a unified perspective on unitarization and the role of entropy in classicalization processes.

Findings

Black hole formation corresponds to classicalization with radius equal to Schwarzschild radius.

Scalar classicalons exhibit entropy-like properties suppressing decay into few particles.

Classicalization is the primary mechanism for unitarization, preceding entropy and thermality.

Abstract

We establish a close parallel between classicalization of gravitons and derivatively-coupled Nambu-Goldstone-type scalars. We show, that black hole formation in high energy scattering process represents classicalization with the classicalization radius given by Schwarzschild radius of center of mass energy, and with the precursor of black hole entropy being given by number of soft quanta composing this classical configuration. Such an entropy-equivalent is defined for scalar classicalons also and is responsible for exponential suppression of their decay into small number of final particles. This parallel works in both ways. For optimists that are willing to hypothesize that gravity may indeed self-unitarize at high energies via black hole formation, it illustrates that the Goldstones may not be much different in this respect, and they classicalize essentially by similar dynamics as gravitons. In the other direction, it may serve as an useful de-mystifier of via-black-hole-unitarization process and of the role of entropy in it, as it illustrates, that much more prosaic scalar theories essentially do the same. Finally, it illustrates that in both cases classicalization is the defining property for unitarization, and that it sets-in before one can talk about accompanying properties, such as entropy and thermality of static classicalons (black holes). These properties are by-products of classicalization, and their equivalents can be defined for non-gravitational cases of classicalization.