CMB constraints on monodromy inflation at strong coupling

TL;DR

This paper conducts a detailed numerical analysis of monodromy inflation models at strong coupling using CMB data, revealing constraints on model parameters and the impact of vacuum energy sequestering on their viability.

Contribution

It provides the first comprehensive MCMC analysis of monodromy inflation at strong coupling, exploring parameter space and the effects of vacuum energy sequestering.

Findings

Models with positive Wilson coefficients are ruled out.

Cancellation effects in models with sign-variable coefficients can satisfy current CMB constraints.

Vacuum energy sequestering does not significantly alter Bayesian evidence for these models.

Abstract

We carry out a thorough numerical examination of field theory monodromy inflation at strong coupling. We perform an MCMC analysis using a Gaussian likelihood, fitting multiparameter models using CMB constraints on the spectral index and the tensor to scalar ratio. We show that models with uniquely positive Wilson coefficients are ruled out. If there are coefficients that can take on both signs, there can be a cancellation of terms that flattens the potentials and allows one to satisfy current data, and forecasts with strong constraints on the tensor to scalar ratio. Models of field theory monodromy are naturally enhanced to include a mechanism for canceling off radiative corrections to vacuum energy, via vacuum energy sequestering (VES). Although they include a much larger parameter space, we find that a similar numerical examination yields no significant change in the Bayesian evidence for VES enhanced models, with naturalness considerations making them more attractive from a theoretical perspective.