Lessons from Classical Gravity about the Quantum Structure of Spacetime

TL;DR

This paper argues that gravity is an emergent thermodynamic phenomenon arising from the statistical mechanics of spacetime 'atoms', supported by classical features and the quantum Unruh temperature of horizons.

Contribution

It proposes a paradigm where gravitational field equations are akin to fluid dynamics, viewing gravity as emergent from underlying microscopic degrees of freedom.

Findings

Gravity can be derived as a thermodynamic limit of spacetime microstructure

Classical features of gravity support the emergent paradigm

Quantum Unruh temperature plays a key role in this framework

Abstract

I present the theoretical evidence which suggests that gravity is an emergent phenomenon like gas dynamics or elasticity with the gravitational field equations having the same status as, say, the equations of fluid dynamics/elasticity. This paradigm views a wide class of gravitational theories - including Einstein's theory - as describing the thermodynamic limit of the statistical mechanics of "atoms of spacetime". The evidence for this paradigm is hidden in several classical features of the gravitational theories and depends on just one quantum mechanical input, viz. the existence of Davies-Unruh temperature of horizons. I discuss several conceptual ingredients of this approach.