Cosmological perturbations from vector inflation

TL;DR

This paper investigates linear perturbations in vector inflation, revealing mode couplings, decay of vector perturbations, and potential correlations in the CMB, with implications for observable signatures.

Contribution

It provides a detailed analysis of perturbation behavior in vector inflation, highlighting mode couplings and their effects on CMB correlations, which was not previously well understood.

Findings

Vector perturbations decay exponentially.

Scalar and tensor modes remain weakly coupled.

Potential for observable correlations in the CMB.

Abstract

We analyze the behavior of linear perturbations in vector inflation. In contrast to the scalar field inflation, the linearized theory with vector fields contains couplings between scalar, vector and tensor modes. The perturbations decouple only in the ultraviolet limit, which allows us to carry out the canonical quantization. Superhorizon perturbations can be approximately analyzed due to suppressed mixing between different modes in the small fields models. We find that the vector perturbations of the metric decay exponentially, but the scalar and tensor modes could remain weakly coupled throughout the evolution. As a result, the vector inflation can produce significant correlations of the scalar and tensor modes in the CMB. For the realistic models the effect is rather small, but not negligible.