Relic Abundance of Neutralinos in Heterotic String Theory: Weak Coupling vs. Strong Coupling

TL;DR

This paper compares neutralino relic abundance predictions in weak and strong coupling regimes of heterotic string theory, showing that strong coupling models align better with cosmological data due to comparable scalar and gaugino masses.

Contribution

It demonstrates that strong coupling heterotic models naturally produce acceptable neutralino relic abundances, unlike weak coupling models with large scalar masses.

Findings

Weak coupling models predict too high relic abundance due to large scalar masses.

Strong coupling models (heterotic M-theory) yield relic abundances compatible with observations.

Scalar and gaugino masses are of similar magnitude in strong coupling regimes.

Abstract

The relic abundance of stable neutralinos is investigated in $E_8 \times E_8'$ heterotic string theory when supersymmetry is spontaneously broken by hidden-sector gaugino condensates. In the weak coupling regime, very large scalar masses (compared to gaugino masses) are shown to lead to a too large relic abundance of the neutralinos, incompatible with cosmological observations in most of parameter space. The problem does not arise in the strong coupling regime (heterotic M-theory) because there scalar and gaugino masses are generically of the same order of magnitude.