Non-thermal Dark Matter in String Compactifications

TL;DR

The paper investigates non-thermal dark matter in string theory, focusing on sequestered LARGE Volume Scenario (LVS) constructions where late-decaying moduli govern DM production. It shows that the lightest modulus can reheat the universe and generate the observed DM abundance via two regimes: a high-$T_{rh}$ annihilation scenario and a low-$T_{rh}$ branching scenario, each with distinct implications for neutralino DM and axion DM. In the annihilation regime, Wino/Higgsino-like DM can be viable and axion DM can contribute in a controlled, multi-component setup depending on the QCD axion origin (open vs closed string); in the branching regime, axions are diluted and DM is produced predominantly from modulus decay, allowing a broad range of DM masses. The results demonstrate that non-thermal DM in LVS can solve the moduli-induced gravitino problem and axionic DR overproduction while preserving TeV-scale SUSY, broadening DM model-building in UV-complete theories.

Abstract

Non-thermal cosmological histories are capable of greatly increasing the available parameter space of different particle physics dark matter (DM) models and are well-motivated by the ubiquity of late-decaying gravitationally coupled scalars in UV theories like string theory. A non-thermal DM model is presented in the context of LARGE Volume Scenarios in type IIB string theory. The model is capable of addressing both the moduli-induced gravitino problem as well as the problem of overproduction of axionic dark radiation and/or DM. We show that the right abundance of neutralino DM can be obtained in both thermal under and overproduction cases for DM masses between O(GeV) to O(TeV). In the latter case the contribution of the QCD axion to the relic density is totally negligible, while in the former case it can be comparable to that of the neutralino thus resulting in a multi-component DM scenario.