LARGE Volume String Compactifications at Finite Temperature

TL;DR

This paper investigates the finite-temperature behavior of LARGE Volume flux compactifications in type IIB string theory, revealing constraints on internal volume and implications for cosmology and particle physics.

Contribution

It provides a detailed analysis of thermal effects in LARGE Volume compactifications, deriving bounds on internal volume and implications for inflation and supersymmetry.

Findings

High-temperature moduli can thermalize but have negligible effect on potential.

Allowed internal volume is constrained to around 10^{15}l_s^6, favoring TeV-scale SUSY.

Heavy moduli decay early, not diluting relics, and thermal inflation requires physics beyond current EFT.

Abstract

We present a detailed study of the finite-temperature behaviour of the LARGE Volume type IIB flux compactifications. We show that certain moduli can thermalise at high temperatures. Despite that, their contribution to the finite-temperature effective potential is always negligible and the latter has a runaway behaviour. We compute the maximal temperature $T_{max}$, above which the internal space decompactifies, as well as the temperature $T_*$, that is reached after the decay of the heaviest moduli. The natural constraint $T_*<T_{max}$ implies a lower bound on the allowed values of the internal volume $\mathcal{V}$. We find that this restriction rules out a significant range of values corresponding to smaller volumes of the order $\mathcal{V}\sim 10^{4}l_s^6$, which lead to standard GUT theories. Instead, the bound favours values of the order $\mathcal{V}\sim 10^{15}l_s^6$, which lead to TeV scale SUSY desirable for solving the hierarchy problem. Moreover, our result favours low-energy inflationary scenarios with density perturbations generated by a field, which is not the inflaton. In such a scenario, one could achieve both inflation and TeV-scale SUSY, although gravity waves would not be observable. Finally, we pose a two-fold challenge for the solution of the cosmological moduli problem. First, we show that the heavy moduli decay before they can begin to dominate the energy density of the Universe. Hence they are not able to dilute any unwanted relics. And second, we argue that, in order to obtain thermal inflation in the closed string moduli sector, one needs to go beyond the present EFT description.