Cosmology at the end of the world

Abstract

In the last two decades the anti-de Sitter/conformal field theory (AdS/CFT) correspondence has emerged as a focal point of many research interests. In particular, it functions as a stepping stone to a still-missing full quantum theory of gravity. In this context, a pivotal question is if and how cosmological physics can be studied using AdS/CFT. Motivated by string theory, braneworld cosmologies propose that our universe is a four-dimensional membrane embedded in a bulk five-dimensional AdS spacetime. We show how such a scenario can be microscopically realized in AdS/CFT using special field theory states dual to an ‘end-of-the-world brane’ moving in a charged black hole spacetime. Observers on the brane experience cosmological physics and approximately four-dimensional gravity, at least locally in spacetime. This result opens a path towards a description of quantum cosmology and the simulation of cosmology on quantum machines. Braneworld cosmologies describe our universe as a four-dimensional membrane embedded in a bulk five-dimensional anti-de Sitter spacetime. In a possible holographic realization, observers on the brane experience cosmology, and gravity is localized.