Do we live on the End of the World?

TL;DR

This paper explores a cosmological scenario where a de Sitter universe exists on an 'End-of-the-World' brane, using holographic renormalization to resolve tension issues and suggesting new approaches to quantum gravity cosmology.

Contribution

It introduces a novel interpretation of de Sitter branes within a holographic framework, connecting the Swampland conjectures with bubble nucleation and boundary spacetime concepts.

Findings

Finite positive brane tension after holographic renormalization

Equivalent interpretation as up-tunneling from AdS with diverging negative cosmological constant

Applicability to any number of dimensions and metric perturbations

Abstract

We propose a scenario of a de Sitter universe living on an End-of-the-World brane. Motivated by the Swampland programme and in particular the Cobordism Conjecture, we consider a compact region of AdS$_5$ nucleating from nothing, with a dS$_4$ living on its boundary. We show that it can equivalently be interpreted as an up-tunnelling from AdS$_5$ with cosmological constant $\Lambda\to -\infty$, following Brown and Dahlen's proposal for 'nothing'. Their picture naively leads to the conclusion that the brane has infinite negative tension. But we show that it becomes finite and positive once we employ holographic renormalization, recovering the Bubble of Something where the domain wall becomes a boundary of spacetime. The same holds true in any number of dimensions and, moreover, at the level of metric perturbations. This provides motivation for alternative routes of obtaining cosmology from quantum gravity or string theory using domain walls, departing from conventional vacuum approaches.