Multigravity in six dimensions: Generating bounces with flat positive tension branes

TL;DR

This work extends multigravity to six dimensions to realize flat, positive-tension branes without ghosts by exploiting a nontrivial internal space that allows warp-factor bounces. It develops minimal and generalized single-brane solutions, then builds bigravity models (conifold and non-singular) and extends to quasi-localized and crystalline multigravity scenarios, all without moving negative tension branes. The analysis provides explicit warp-factor forms, graviton zero modes, and spectra (discrete vs continuum) along with tunings that maintain flat branes, enabling viable large-distance modifications of gravity. The results offer theoretically consistent, phenomenologically relevant frameworks for modified gravity, with distinctive KK structures and potential cosmological implications.

Abstract

We present a generalization of the five dimensional multigravity models to six dimensions. The key characteristic of these constructions is that that we obtain solutions which do not have any negative tension branes while at the same time the branes are kept flat. This is due to the fact that in six dimensions the internal space is not trivial and its curvature allows bounce configurations with the above feature. These constructions give for the first time a theoretically and phenomenologically viable realization of multigravity.

Figures (13)

• Figure 1: The minimal single four-brane model warp factors $\sigma(\rho)$ and $\gamma(\rho)$.
• Figure 2: The form of the effective potential $V_{eff}$ for different angular quantum numbers $l$ for the minimal single four-brane model. The $\delta$-function in the origin is omitted.
• Figure 3: The generalized single four-brane warp factors $\sigma(\rho)$ and $\gamma(\rho)$ for different values of the parameter $\alpha$.
• Figure 4: The form of the effective potential $V_{eff}$ for $\alpha>2$ for different angular quantum numbers $l$. The $\delta$-function in the origin is omitted.
• Figure 5: The form of the effective potential $V_{eff}$ for $\alpha<2$ for different angular quantum numbers $l$. The $\delta$-function in the origin is omitted.