The dilaton as a candidate for dark matter

TL;DR

This paper explores the potential of the dilaton, stabilized via the axion, as a dark matter candidate by analyzing its mass relations and cosmological implications.

Contribution

It provides a theoretical estimate linking the dilaton potential to axion parameters and predicts the dilaton mass relative to the axion mass, suggesting its viability as dark matter.

Findings

Dilaton mass is related to axion parameters and instanton effects.

The dilaton must be strongly aligned to avoid overclosing the universe.

Predicted dilaton properties are consistent with dark matter constraints.

Abstract

We examine consequences of the stabilization of the dilaton through the axion. An estimate of the resulting dilaton potential yields a relation between the axion parameter $m_a f_{PQ}$ and the average instanton radius, and predicts the ratio between the dilaton mass $m_\phi$ and the axion mass $m_a$. If we identify the string axion with a Peccei--Quinn axion, then $m_\phi m_{Pl} \sim m_a f_{PQ}$, and the dilaton should be strongly aligned $\sqrt{<\phi^2>}\leq 10^{-4}m_{Pl}$ at the QCD scale, in order not to overclose the universe.