Emergent de Sitter Cosmology from Decaying AdS

TL;DR

This paper proposes a string theory model where a 4D observer experiences an effective positive cosmological constant through brane-mediated decay from a false AdS vacuum, addressing challenges in embedding de Sitter space in quantum gravity.

Contribution

It introduces a novel embedding of positive energy cosmology within string theory using brane decay, bypassing the need for fundamental de Sitter vacua.

Findings

Demonstrates a consistent string theory setup for emergent de Sitter cosmology.

Shows how brane decay from false AdS vacuum leads to effective positive cosmological constant.

Addresses the UV/IR puzzle in embedding cosmological vacua in quantum gravity.

Abstract

Recent developments in string compactifications demonstrate obstructions to the simplest constructions of low energy cosmologies with positive vacuum energy. The existence of obstacles to creating scale-separated de Sitter solutions indicates a UV/IR puzzle for embedding cosmological vacua in a unitary theory of quantum gravity. Motivated by this puzzle, we propose an embedding of positive energy Friedmann-Lemaitre-Robertson-Walker cosmology within string theory. Our proposal involves confining 4D gravity on a brane which mediates the decay from a non-supersymmetric false AdS5 vacuum to a true vacuum. In this way, it is natural for a 4D observer to experience an effective positive cosmological constant coupled to matter and radiation, avoiding the need for scale separation or a fundamental de Sitter vacuum.