Inflation in string theory: a graceful exit to the real world

TL;DR

This work presents a UV-complete closed-string inflation model within Type IIB LARGE Volume Scenarios, where the inflaton is a Kähler modulus (the blow-up cycle $ au_2$) with calculable couplings to hidden, moduli, and visible sectors. The volume ${\cal V}$ is stabilised at a very large value, yielding controlled effective field theory and hierarchies such as $M_{GUT} \\sim M_P/\\cal V^{1/3}$ and $M_s \\sim M_P/\\cal V^{1/2}$, while the visible sector remains sequestered. Inflation is a small-field, single-field dynamics with a potential that gives $r \\ll 1$ and $n_s$ in the observed range for ${\\cal V} \\sim 10^{6-7}$; reheating proceeds predominantly through decays of the inflaton to visible gauge bosons after a sequence that avoids overproduction of hidden states. The model yields a reheating temperature above $T_{BBN}$, suppresses the cosmological moduli problem, and realizes GUT-scale physics with TeV-scale SUSY, all without fine-tuning, illustrating a concrete bridge between string cosmology and low-energy phenomenology.

Abstract

The most important criteria for a successful inflation are to explain the observed temperature anisotropy in the cosmic microwave background radiation, and exiting inflation in a vacuum where it can excite the Standard Model quarks and leptons required for the success of Big Bang Nucleosynthesis. In this paper we provide the first ever closed string model of inflation where the inflaton couplings to hidden sector, moduli sector, and visible sector fields can be computed, showing that inflation can lead to reheating the Standard Model degrees of freedom before the electro-weak scale.