Exotic Smoothness in Four Dimensions and Euclidean Quantum Gravity

TL;DR

This paper investigates how exotic smooth structures in four-dimensional Euclidean quantum gravity influence observable quantities, revealing significant effects that are consistent across different actions and include one-loop corrections.

Contribution

It provides the first analysis of exotic smoothness effects in four-dimensional Euclidean quantum gravity, including semiclassical and one-loop results, demonstrating their physical significance.

Findings

Exotic smooth structures affect key observables in quantum gravity.

Results are consistent across various gravitational actions.

Topological features can have physically significant effects without new physics.

Abstract

In this paper we calculate the effect of the inclusion of exotic smooth structures on typical observables in Euclidean quantum gravity. We do this in the semiclassical regime for several gravitational free-field actions and find that the results are similar, independent of the particular action that is chosen. These are the first results of their kind in dimension four, which we extend to include one-loop contributions as well. We find these topological features can have physically significant results without the need for additional exotic physics.