Synergistic Gravity and the Role of Resonances in GRS-Inspired Braneworlds

TL;DR

This paper investigates how zero modes and resonant graviton modes influence the emergence of four-dimensional gravity in various 5D braneworld models inspired by GRS, highlighting the effects of model asymmetry and scalar fields.

Contribution

It analyzes the interplay between zero modes and resonant modes in GRS-inspired models, introducing new insights into quasi-localized gravity and the impact of asymmetry and scalar fields.

Findings

Resonance and zero mode both significantly contribute at a specific scale.

Asymmetry weakens the resonance, shortening the 4D gravity scale.

Scalar field configurations can replace the central brane for localization.

Abstract

We consider 5D braneworld models of quasi-localized gravity in which 4D gravity is reproduced at intermediate scales while the extra dimension opens up at both the very short and the very long distances, where the geometry is flat. Our main interest is the interplay between the zero mode of these models, whenever a normalizable zero mode exists, and the effects of zero energy graviton resonant modes coming from the contributions of massive KK modes. We first consider a compactified version of the GRS model and find that quasi-localized gravity is characterized by a scale for which both the resonance and the zero mode have significant contribution to 4D gravity. Above this scale, gravity is primarily mediated by the zero mode, while the resonance gives only minor corrections. Next, we consider an asymmetric version of the standard non-compact GRS model, characterized by different cosmological constants on each AdS side. We show that a resonance is present but the asymmetry, through the form of the localizing potential, can weaken it, resulting in a shorter lifetime and, thus, in a shorter distance scale for 4D gravity. As a third model exhibiting quasi-localization, we consider a version of the GRS model in which the central positive tension brane has been replaced by a configuration of a scalar field propagating in the bulk.