Reheating for Closed String Inflation
Michele Cicoli, Anupam Mazumdar
TL;DR
This work investigates reheating for closed-string inflation within the LARGE Volume Scenario, focusing on two inflaton realizations (Blow-up Inflation and Fibre Inflation) and the unavoidable presence of hidden sectors. By computing the canonical moduli normalisations and their couplings to both visible MSSM-like sectors and hidden gauge sectors, the authors show that inflaton energy is typically dumped into hidden dof, placing stringent constraints on hidden-sector model-building and gauge-topology choices. A key result is that a viable reheating channel to the visible sector exists mainly in the Blow-up Inflation scenario when the inflaton 4-cycle is wrapped by the visible sector or at the quiver locus, where a pure $N=1$ SYM hidden sector can suppress unwanted decays; other setups face tensions with TeV-scale SUSY, DM overproduction, or insufficient reheating. Finite-temperature considerations and the LVS decompactification limit yield upper bounds on reheating temperatures, guiding model-building and suggesting curvaton- or modulating-field mechanisms as potential ways to reconcile inflationary predictions with low-scale SUSY. Collectively, the paper provides concrete criteria and quantitative benchmarks for constructing string-theoretic, reheated cosmologies compatible with MSSM phenomenology.
Abstract
We point out some of the outstanding challenges for embedding inflationary cosmology within string theory studying the process of reheating for models where the inflaton is a closed string mode parameterising the size of an internal cycle of the compactification manifold. A realistic model of inflation must explain the tiny perturbations in the cosmic microwave background radiation and also how to excite the ordinary matter degrees of freedom after inflation, required for the success of Big Bang Nucleosynthesis. We study these issues focusing on two promising inflationary models embedded in LARGE volume type IIB flux compactifications. We show that phenomenological requirements and consistency of the effective field theory treatment imply the presence at low energies of a hidden sector together with a visible sector, where the Minimal Supersymmetric Standard Model fields are residing. A detailed calculation of the inflaton coupling to the fields of the hidden sector, visible sector, and moduli sector, reveals that the inflaton fails to excite primarily the visible sector fields, instead hidden sector fields are excited copiously after the end of inflation. This sets severe constraints on hidden sector model building where the most promising scenario emerges as a pure N=1 SYM theory, forbidding the kinematical decay of the inflaton to the hidden sector. In this case it is possible to reheat the Universe with the visible degrees of freedom even though in some cases we discover a new tension between TeV scale SUSY and reheating on top of the well-known tension between TeV scale SUSY and inflation.