# On Non-Perturbative Unitarity in Gravitational Scattering

## TL;DR

This paper proposes that non-perturbative effects in General Relativity unitarize graviton-scalar scattering at high energies, with the background geometry's back reaction softening UV behavior and connecting low-energy perturbative results to classical plane wave scattering.

## Contribution

It introduces a non-perturbative mechanism within General Relativity that unitarizes high-energy graviton-scalar scattering by accounting for background back reaction effects.

## Key findings

- Non-perturbative plane wave backgrounds emerge at Planckian energies.
- The scattering amplitude smoothly interpolates between perturbative and classical regimes.
- Back reaction effects soften the ultraviolet behavior of the scattering amplitude.

## Abstract

We argue that the tree-level graviton-scalar scattering in the Regge limit is unitarized by non-perturbative effects within General Relativity. At Planckian energy the back reaction of the incoming graviton on the background geometry produces a non-perturbative plane wave which, in turn, softens the UV-behavior. Our amplitude then interpolates between the perturbative graviton-scalar scattering at low energy and scattering on a classical plane wave in the Regge limit.