Fat Gravitons, the Cosmological Constant and Sub-millimeter Tests

TL;DR

This paper explores the idea that resolving the Cosmological Constant Problem may involve a breakdown of the point-particle approximation for gravitons at sub-millimeter scales, proposing a soft graviton effective theory consistent with known physics.

Contribution

It introduces a Soft Graviton Effective Theory that addresses the self-consistency of sub-millimeter modifications to gravity while preserving the equivalence principle and quantum naturalness.

Findings

Naturalness bounds suggest deviations above ~20 microns

The theory preserves the macroscopic equivalence principle

Proposes a distinct experimental signature for short-distance gravity tests

Abstract

We revisit the proposal that the resolution of the Cosmological Constant Problem involves a sub-millimeter breakdown of the point-particle approximation for gravitons. No fundamental description of such a breakdown, which simultaneously preserves the point-particle nature of matter particles, is yet known. However, basic aspects of the self-consistency of the idea, such as preservation of the macroscopic Equivalence Principle while satisfying quantum naturalness of the cosmological constant, are addressed in this paper within a Soft Graviton Effective Theory. It builds on Weinberg's analysis of soft graviton couplings and standard heavy particle effective theory, and minimally encompasses the experimental regime of soft gravity coupled to hard matter. A qualitatively distinct signature for short-distance tests of gravity is discussed, bounded by naturalness to appear above approximately 20 microns.