# T-duality equivalences beyond string theory

## TL;DR

This paper explores a family of gravitational actions with higher-derivative terms that are invariant under corrected T-duality, showing that black hole entropy and temperature are T-duality invariant, suggesting broader physical equivalences beyond string theory.

## Contribution

It derives explicit corrected T-duality rules for a two-parameter family of gravitational actions and demonstrates T-duality invariance of black hole thermodynamics within this framework.

## Key findings

- Black hole entropy is T-duality invariant.
- Black hole temperature is T-duality invariant.
- The action's invariance extends beyond string theory contexts.

## Abstract

We examine a two parameter family of gravitational actions which contains higher-derivative terms. These are such that the entire action is invariant under corrected T-duality rules, which we derive explicitly. Generically this action does not describe low energy string backgrounds except for isolated choices for the parameters. Nevertheless, we demonstrate that in this theory the entropy and the temperature of generic black hole solutions are T-duality invariant. This further supports the idea put forward in our previous work that T-duality might provide physical equivalences beyond the realm of string theory.