Authors: Clifford Cheung Grant N Remmen
Publish Date: 2014/12/11
Volume: 2014, Issue: 12, Pages: 87-
Abstract
The weak gravity conjecture WGC asserts that an Abelian gauge theory coupled to gravity is inconsistent unless it contains a particle of charge q and mass m such that q≥m/m Pl This criterion is obeyed by all known ultraviolet completions and is needed to evade pathologies from stable black hole remnants In this paper we explore the WGC from the perspective of lowenergy effective field theory Below the charged particle threshold the effective action describes a photon and graviton interacting via higherdimension operators We derive infrared consistency conditions on the parameters of the effective action using i analyticity of lightbylight scattering ii unitarity of the dynamics of an arbitrary ultraviolet completion and iii absence of superluminality and causality violation in certain nontrivial backgrounds For convenience we begin our analysis in three spacetime dimensions where gravity is nondynamical but has a physical effect on photonphoton interactions We then consider four dimensions where propagating gravity substantially complicates all of our arguments but bounds can still be derived Operators in the effective action arise from two types of diagrams those that involve electromagnetic interactions parameterized by a chargetomass ratio q/m and those that do not parameterized by a coefficient γ Infrared consistency implies that q/m is bounded from below for small γThis article is published under an open access license Please check the Copyright Information section for details of this license and what reuse is permitted If your intended use exceeds what is permitted by the license or if you are unable to locate the licence and reuse information please contact the Rights and Permissions team
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