Desensitizing Inflation from the Planck Scale

TL;DR

This paper introduces a mechanism where coupling the inflaton to a conformal sector suppresses Planck-scale corrections, effectively solving the eta problem in inflationary models without requiring unbroken shift symmetry.

Contribution

It proposes a novel approach to mitigate the eta problem by using conformal sector interactions to sequester high-energy corrections in inflation.

Findings

The mechanism suppresses Planck-scale corrections to the eta parameter.

Exact anomalous dimensions are computed via a-maximization.

The eta problem can be addressed with weakly-coupled physics.

Abstract

A new mechanism to control Planck-scale corrections to the inflationary eta parameter is proposed. A common approach to the eta problem is to impose a shift symmetry on the inflaton field. However, this symmetry has to remain unbroken by Planck-scale effects, which is a rather strong requirement on possible ultraviolet completions of the theory. In this paper, we show that the breaking of the shift symmetry by Planck-scale corrections can be systematically suppressed if the inflaton field interacts with a conformal sector. The inflaton then receives an anomalous dimension in the conformal field theory, which leads to sequestering of all dangerous high-energy corrections. We analyze a number of models where the mechanism can be seen in action. In our most detailed example we compute the exact anomalous dimensions via a-maximization and show that the eta problem can be solved using only weakly-coupled physics.