Anisotropic tensor modes from icosahedral inflation

TL;DR

This paper investigates anisotropic tensor modes in icosahedral inflation, revealing small anisotropies aligned with the icosahedral symmetry and identifying leading contributions to mixed correlators, with implications for cosmological observations.

Contribution

It provides the first detailed calculation of anisotropic tensor modes in icosahedral inflation, including higher derivative corrections and their effects on correlators.

Findings

Anisotropies in tensor modes are aligned with icosahedral symmetry.

Leading contributions to mixed helicity correlators are identified.

The effect size is small within the effective theory regime.

Abstract

For icosahedral inflation, we compute the tensor modes' two-point function in the presence of higher derivative corrections, and show that in general this features anisotropies that are aligned with the underlying icosahedral structure. The effect is small within the regime of validity of the effective theory, but it is the leading contribution to a mixed correlator between the two different helicities. We also estimate the magnitude of a similar effect for a mixed scalar-tensor correlator, whose detailed computation we leave for future work. Along the way, we clarify a number of aspects of the spin decomposition of generic icosahedral-invariant physical quantities.