Cosmology of F-theory GUTs

TL;DR

This paper explores how F-theory GUT models naturally satisfy cosmological constraints, with a focus on axion supermultiplet dynamics, dark matter production, and baryogenesis, all within a consistent early universe scenario.

Contribution

It demonstrates that F-theory GUTs can inherently produce a viable cosmological history, including dark matter and baryon asymmetry, without requiring fine-tuning of initial conditions.

Findings

Saxion decay reheats the universe to ~1 GeV, diluting relics and enabling dark matter production.

The scenario is independent of the initial reheating temperature due to the saxion oscillation timing.

Gravitino mass range (10-100 MeV) aligns with solutions to Li(7) over-production.

Abstract

In this paper we study the interplay between the recently proposed F-theory GUTs and cosmology. Despite the fact that the parameter range for F-theory GUT models is very narrow, we find that F-theory GUTs beautifully satisfy most cosmological constraints without any further restrictions. The viability of the scenario hinges on the interplay between various components of the axion supermultiplet, which in F-theory GUTs is also responsible for breaking supersymmetry. In these models, the gravitino is the LSP and develops a mass by eating the axino mode. The radial component of the axion supermultiplet known as the saxion typically begins to oscillate in the early Universe, eventually coming to dominate the energy density. Its decay reheats the Universe to a temperature of ~ 1 GeV, igniting BBN and diluting all thermal relics such as the gravitino by a factor of ~ 10^(-4) - 10^(-5) such that gravitinos contribute a sizable component of the dark matter. In certain cases, non-thermally produced relics such as the axion, or gravitinos generated from the decay of the saxion can also contribute to the abundance of dark matter. Remarkably enough, this cosmological scenario turns out to be independent of the initial reheating temperature of the Universe. This is due to the fact that the initial oscillation temperature of the saxion coincides with the freeze out temperature for gravitinos in F-theory GUTs. We also find that saxion dilution is compatible with generating the desired baryon asymmetry from standard leptogenesis. Finally, the gravitino mass range in F-theory GUTs is 10-100 MeV, which interestingly coincides with the window of values required for the decay of the NLSP to solve the problem of Li(7) over-production.