Inflationary Cosmology with Quantum Gravitational Effects and the Swampland Conjectures

TL;DR

This paper investigates whether quantum gravitational effects, modeled via nonlinear dispersion relations, can reconcile single-field inflation models with swampland conjectures and observational data by modifying perturbation spectra.

Contribution

It demonstrates that quantum gravitational effects can alter perturbation amplitudes, potentially reducing the tensor-to-scalar ratio and easing conflicts with swampland criteria.

Findings

Quantum gravitational effects significantly modify scalar and tensor spectra.

Modifications can either increase or decrease perturbation amplitudes.

These effects help reconcile inflation models with swampland conjectures and observations.

Abstract

Recently proposed two swampland criteria that arising from string theory landscape lead to the important challenge of the realization of single-field inflationary models. Especially one of swampland criteria which implies a large tensor-to-scalar ratio is strongly in tension with recent observational results. In this paper, we explore the possibility if the swampland conjectures could be compatible with single-field inflationary scenarios if the effects due to the quantum theory of gravity are considered. We show that the quantum gravitational effects due to the nonlinear dispersion relation provides significant modifications on the amplitude of both the scalar and tensor perturbation spectra. Such modifications could be either raise or reduce the perturbation spectra depending on the values of the parameters in the nonlinear terms of the dispersion relations. Therefore, these effects can reduce the tensor-to-scalar ratio to a smaller value which helps to relax the tension between the swampland conjecture and observational data.