Poly-instanton Inflation

TL;DR

This paper introduces a new inflationary model within type IIB Calabi-Yau compactifications where poly-instanton effects generate a flat potential for the Kähler modulus, aligning with observational data and predicting a low tensor-to-scalar ratio.

Contribution

The paper presents a novel inflation scenario driven by poly-instanton corrections, ensuring a naturally flat potential and negligible higher-dimensional operator effects during inflation.

Findings

Spectral index n_s ≈ 0.96

Tensor-to-scalar ratio r ≈ 10^{-5}

Reheating temperature around 10^6 GeV

Abstract

We propose a new inflationary scenario in type IIB Calabi-Yau compactifications, where the inflaton is a K\"ahler modulus parameterising the volume of an internal four-cycle. The inflaton potential is generated via poly-instanton corrections to the superpotential which give rise to a naturally flat direction due to their double exponential suppression. Given that the volume mode is kept stable during inflation, all the inflaton-dependent higher dimensional operators are suppressed. Moreover, string loop effects can be shown to be negligible throughout all the inflationary dynamics for natural values of the underlying parameters. The model is characterised by a reheating temperature of the order $T_{\rm rh}\simeq 10^6$ GeV which requires $N_e \simeq 54$ e-foldings of inflation. All the inflationary observables are compatible with current observations since the spectral index is $n_s \simeq 0.96$, while the tensor-to-scalar ratio is $r\simeq 10^{-5}$. The volume of the Calabi-Yau is of order $10^3$ in string units, corresponding to an inflationary scale around $10^{15}$ GeV