Dark Radiation and Dark Matter in Large Volume Compactifications

TL;DR

This paper explores how large volume string compactifications naturally produce dark radiation and dark matter through modulus decay, with implications for axions and supersymmetric particles.

Contribution

It demonstrates that modulus decay in LARGE volume scenarios can account for observed dark radiation and dark matter, depending on sequestering conditions.

Findings

Axionic superpartners from modulus decay can explain dark radiation.

Sequestered case: lightest supersymmetric particles match dark matter density.

Non-sequestered case: QCD axion is a plausible dark matter candidate.

Abstract

We argue that dark radiation is naturally generated from the decay of the overall volume modulus in the LARGE volume scenario. We consider both sequestered and non-sequestered cases, and find that the axionic superpartner of the modulus is produced by the modulus decay and it can account for the dark radiation suggested by observations, while the modulus decay through the Giudice-Masiero term gives the dominant contribution to the total decay rate. In the sequestered case, the lightest supersymmetric particles produced by the modulus decay can naturally account for the observed dark matter density. In the non-sequestered case, on the other hand, the supersymmetric particles are not produced by the modulus decay, since the soft masses are of order the heavy gravitino mass. The QCD axion will then be a plausible dark matter candidate.