Multifield Dynamics in Higgs-otic Inflation

TL;DR

This paper analyzes the full two-field dynamics of Higgs-otic inflation, revealing that isocurvature perturbations are damped and the model's predictions align with current observational data.

Contribution

It provides a comprehensive analysis of adiabatic and isocurvature perturbations in Higgs-otic inflation, improving the understanding of its observational signatures.

Findings

Isocurvature perturbations are exponentially damped by the end of inflation.

Tensor-to-scalar ratio is in the range 0.08-0.12, consistent with Planck/BICEP.

Full two-field analysis increases the model's predictivity.

Abstract

In Higgs-otic inflation a complex neutral scalar combination of the $h^0$ and $H^0$ MSSM Higgs fields plays the role of inflaton in a chaotic fashion. The potential is protected from large trans-Planckian corrections at large inflaton if the system is embedded in string theory so that the Higgs fields parametrize a D-brane position. The inflaton potential is then given by a DBI+CS D-brane action yielding an approximate linear behaviour at large field. The inflaton scalar potential is a 2-field model with specific non-canonical kinetic terms. Previous computations of the cosmological parameters (i.e. scalar and tensor perturbations) did not take into account the full 2-field character of the model, ignoring in particular the presence of isocurvature perturbations and their coupling to the adiabatic modes. It is well known that for generic 2-field potentials such effects may significantly alter the observational signatures of a given model. We perform a full analysis of adiabatic and isocurvature perturbations in the Higgs-otic 2-field model. We show that the predictivity of the model is increased compared to the adiabatic approximation. Isocurvature perturbations moderately feed back into adiabatic fluctuations. However, the isocurvature component is exponentially damped by the end of inflation. The tensor to scalar ratio varies in a region $r=0.08-0.12$, consistent with combined Planck/BICEP results.