Continuity, Localization, and Cosmology in Warped Geometry

TL;DR

This paper investigates the localization of massive bulk fields in warped 5D anti-de Sitter spacetime, revealing conditions for localized modes and their cosmological implications, especially in de Sitter brane scenarios.

Contribution

It introduces a boundary term that enables a massless localized mode in the massive scalar theory and analyzes localization in de Sitter branes, connecting bulk field behavior to cosmology.

Findings

Massive 5D scalar lacks localized mode without boundary modifications.

A boundary term can induce a localized massless mode.

Localized massive modes exist in de Sitter brane scenarios.

Abstract

This is the first of two papers studying localization of massive bulk fields on a bane in 5D anti-de Sitter spacetime, and some of their cosmological consequences. Here we focus on a massive 5D scalar, which is known to lack a localized mode, and discuss how a seeming discontinuity between this theory and the massless theory - known to support a localized zero mode - is resolved thanks to peculiar analytic properties of the massive two-point amplitude. Furthermore, we propose a boundary term that leads to the emergence of a massless localized mode in the massive theory. Last but not least, we consider the case when the brane world-volume is de Sitter spacetime, and prove the existence of a localized massive mode. We discuss how these results, taken collectively, can be used to describe the accelerated expansion due to the massive 5D scalar field in an early, or in a late-time universe.