An Introduction to the Weak Gravity Conjecture

TL;DR

The paper introduces the Weak Gravity Conjecture, proposing that gravity is the weakest force in all consistent quantum theories, and discusses its implications for string theory, particle physics, and cosmology.

Contribution

It provides an accessible overview of the Weak Gravity Conjecture, its evidence, and its potential role in connecting string theory with observable physics.

Findings

The Weak Gravity Conjecture is supported by various theoretical arguments.

It suggests gravity's relative weakness is a universal feature in quantum gravity theories.

Implications for unifying string theory with particle physics and cosmology are explored.

Abstract

The Weak Gravity Conjecture holds that gravity must be the weakest force. This is true of the familiar forces in our own universe -- electromagnetism, for instance, is many orders of magnitude stronger than gravity. But the bold claim of the Weak Gravity Conjecture is that this statement is true, not only for electromagnetism in our universe, but for any similar force in any consistent universe governed by quantum mechanics. In this brief introduction, aimed at advanced undergraduates or beginning graduate students, we elaborate on the precise definition of the Weak Gravity Conjecture, the evidence for it, and some of the remarkable implications of it. We explain how the Weak Gravity Conjecture may play a role in bridging the gulf between the formal mathematics of string theory and the real-world observations of particle physics and cosmology.