Low Energy Effective Action for Dilatonic Braneworld --A Formalism for Inflationary Braneworld--

TL;DR

This paper derives the low energy effective action for dilatonic braneworlds, revealing how dark radiation and Kaluza-Klein corrections influence the dynamics, and explores implications for inflation and the AdS/CFT correspondence.

Contribution

It provides a formalism for the effective action in dilatonic braneworlds, including KK corrections and the role of the bulk scalar field, extending previous models.

Findings

Effective theory described by Einstein-scalar coupled to dark radiation

Dark radiation is generally non-conserved due to bulk scalar coupling

In two-brane models, the effective theory becomes a scalar-tensor theory with radion-scalar coupling

Abstract

We derive the low energy effective action for the dilatonic braneworld. In the case of the single-brane model, we find the effective theory is described by the Einstein-scalar theory coupled to the dark radiation. Remarkably, the dark radiation is not conserved in general due to a coupling to the bulk scalar field. The effective action incorporating Kaluza-Klein (KK) corrections is obtained and the role of the AdS/CFT correspondence in the dilatonic braneworld is revealed. In particular, it is shown that CFT matter would not be confined to the braneworld in the presence of the bulk scalar field. The relation between our analysis and the geometrical projection method is also clarified. In the case of the two-brane model, the effective theory reduces to a scalar-tensor theory with a non-trivial coupling between the radion and the bulk scalar field.