# Spacetime has a `thickness'

## TL;DR

This paper proposes that spacetime has an intrinsic 'thickness' related to quantum gravity effects, which prevents horizon formation and preserves causality in black hole physics.

## Contribution

It introduces the concept of spacetime 'thickness' as an additional attribute, providing a new perspective on black hole information and horizon formation.

## Key findings

- Spacetime's 'thickness' affects high-energy processes near black holes.
- Low energy particles perceive an effective manifold without thickness.
- Finite thickness prevents horizon formation, preserving causality.

## Abstract

Suppose we assume that (a) information about a black hole is encoded in its Hawking radiation and (b) causality is not violated to leading order in gently curved spacetime. Then we argue that spacetime cannot just be described as a manifold with a shape; it must be given an additional attribute which we call `thickness'. This thickness characterizes the spread of the quantum gravity wavefunctional in superspace -- the space of all 3-geometries. Low energy particles travel on spacetime without noticing the thickness parameter, so they just see an effective manifold. Objects with energy large enough to create a horizon do notice the finite thickness; this modifies the semiclassical evolution in such a way that we avoid horizon formation and the consequent violation of causality.