Racetrack inflation and assisted moduli stabilisation
Zygmunt Lalak, Graham G. Ross, Subir Sarkar
TL;DR
The paper addresses moduli stabilization and inflation in a flux-free string-inspired setting by leveraging a racetrack model with two gaugino condensates. Threshold effects induce moduli dependence in the nonperturbative superpotential, and the authors show how a frozen volume modulus T allows focus on inflation driven by the dilaton S and a modulus χ, with topological inflation providing natural initial conditions. The analysis demonstrates slow-roll inflation can occur along the moduli direction without fine-tuning, yielding density perturbations compatible with observations and an inflation scale near the GUT scale. It also clarifies the challenges in both weak and strong coupling regimes and outlines mechanisms to mitigate overshoot and rapid-roll problems, arguing for the broader applicability of this approach beyond the weakly coupled heterotic scenario.
Abstract
We present a model of inflation based on a racetrack model without flux stabilization. The initial conditions are set automatically through topological inflation. This ensures that the dilaton is not swept to weak coupling through either thermal effects or fast roll. Including the effect of non-dilaton fields we find that moduli provide natural candidates for the inflaton. The resulting potential generates slow-roll inflation without the need to fine tune parameters. The energy scale of inflation must be near the GUT scale and the scalar density perturbation generated has a spectrum consistent with WMAP data.