De Sitter and Anti-de Sitter branes in self-tuning models

TL;DR

This paper investigates conditions under which curved-brane solutions, like de Sitter or anti-de Sitter geometries, can exist in self-tuning dilatonic braneworld models, revealing that modifications are needed for such solutions to appear.

Contribution

It demonstrates that standard self-tuning models do not admit de Sitter or anti-de Sitter branes without altering bulk boundary conditions, and explores the existence of stabilized curved solutions with potential implications for string theory.

Findings

No de Sitter or anti-de Sitter vacua without modifying boundary asymptotics.

Existence of stabilized curved solutions with large hierarchy between brane and UV CFT curvature.

Potential for alternative realization of de Sitter space in string theory.

Abstract

Maximally symmetric curved-brane solutions are studied in dilatonic braneworld models which realise the self-tuning of the effective four-dimensional cosmological constant. It is found that no vacua in which the brane has de Sitter or anti-de Sitter geometry exist, unless one modifies the near-boundary asymptotics of the bulk fields. In the holographic dual picture, this corresponds to coupling the UV CFT to a curved metric (possibly with a defect). Alternatively, the same may be achieved in a flat-space QFT with suitable variable scalar sources. With these ingredients, it is found that maximally symmetric, positive and negative curvature solutions with a stabilised brane position generically exist. The space of such solutions is studied in two different types of realisations of the self-tuning framework. In some regimes we observe a large hierarchy between the curvature on the brane and the boundary UV CFT curvature. This is a dynamical effect due to the self-stabilisation mechanism. This setup provides an alternative route to realising de Sitter space in string theory.