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Desensitizing Inflation from the Planck Scale

Daniel Baumann, Daniel Green

TL;DR

This work addresses the eta problem in inflation by introducing conformal sequestering: coupling the inflaton to a conformal sector generates a calculable anomalous dimension that suppresses dangerous Planck-suppressed operators through RG flow. The authors provide a concrete weakly-coupled SUSY model in which $a$-maximization yields explicit anomalous dimensions, and they extend the discussion to non-SUSY contexts and gauged-model comparisons. The key contribution is a low-energy, radiatively natural mechanism to keep $\\\eta$ small despite UV symmetry breaking, enabling robust inflationary dynamics without requiring UV-complete protection. The results offer a framework for designing inflation models with controlled UV corrections and highlight the conditions under which sequestering succeeds or fails, guiding future UV-completion considerations.

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.

Desensitizing Inflation from the Planck Scale

TL;DR

This work addresses the eta problem in inflation by introducing conformal sequestering: coupling the inflaton to a conformal sector generates a calculable anomalous dimension that suppresses dangerous Planck-suppressed operators through RG flow. The authors provide a concrete weakly-coupled SUSY model in which -maximization yields explicit anomalous dimensions, and they extend the discussion to non-SUSY contexts and gauged-model comparisons. The key contribution is a low-energy, radiatively natural mechanism to keep small despite UV symmetry breaking, enabling robust inflationary dynamics without requiring UV-complete protection. The results offer a framework for designing inflation models with controlled UV corrections and highlight the conditions under which sequestering succeeds or fails, guiding future UV-completion considerations.

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.

Paper Structure

This paper contains 28 sections, 65 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Outline of the Basic Idea
  3. A New Solution to the Eta Problem
  4. General Remarks
  5. A Representative SUSY Model
  6. The Eta Problem in Supergravity
  7. Review of Pseudonatural Inflation
  8. The Original Model
  9. Generic Kähler Corrections
  10. A Minimal Extension of the Model
  11. Discrete $\mathbb{Z}_2$ Symmetry
  12. Coupling to a Conformal Sector
  13. Non-Renormalization
  14. Conformal Sequestering
  15. Anomalous Dimensions via $a$-Maximization
  16. ...and 13 more sections

Figures (1)

  • Figure 1: Scales and Dynamics. In general, $M_{\rm pl}$-suppressed corrections to the action do not decouple from the inflationary dynamics at $\Lambda_{\rm inf}$. In this paper we show that this problem can be solved if the inflaton field couples to a conformal sector. In that case, RG flow in the conformal window, $m < \mu < \Lambda$, can suppress the dangerous corrections.