# Axion-Dilaton Destabilization and the Hubble Tension

## TL;DR

This paper proposes a string theory-inspired model where axion-dilaton interactions lead to early dark energy, potentially addressing the Hubble tension by dynamically destabilizing the dilaton during the early universe.

## Contribution

It introduces a novel axion-dilaton interaction mechanism that naturally realizes early dark energy and explains its transient nature in cosmology.

## Key findings

- Dilaton contributes to dark energy in the early universe.
- Destabilization occurs when the Hubble constant drops below the axion mass.
- Dilaton's equation of state reaches w=1 during fast-roll phase.

## Abstract

The discrepancy in measurements of the Hubble constant indicates new physics in dark energy, dark matter, or both. Drawing inspiration from string theory, where axions interact with the other moduli fields, including the dilaton, here we demonstrate that the dynamics of an interacting dilaton and axion naturally realizes the proposal of Early Dark Energy. In this setup, stabilization of the the dilaton is in part due to the axion, and in the early universe the dilaton contributes to dark energy. The combined axion-dilaton system is destabilized when the Hubble constant falls below the mass of the axion, triggering a phase of fast-roll evolution of the dilaton wherein its equation of state is $w=1$, and the early dark energy redshifts away as $a^{-6}$.