Self-accelerating solutions in the cascading DGP braneworld

TL;DR

This paper explores higher-dimensional generalizations of the DGP braneworld model, deriving solutions that include a new self-accelerating branch with potentially less fine-tuning, expanding understanding of cosmic acceleration mechanisms.

Contribution

It introduces a cascading DGP model with higher-dimensional branes, deriving solutions that extend the original DGP self-accelerating branch and proposing a new solution with reduced expansion rate.

Findings

Derived solutions in six-dimensional cascading DGP model.

Identified two solution branches, including a new self-accelerating branch.

New branch has lower expansion rate, potentially reducing fine-tuning.

Abstract

The self-accelerating branch of the Dvali-Gabadadze-Porrati (DGP) five-dimensional braneworld has provided a compelling model for the current cosmic acceleration. Recent observations, however, have not favored it so much. We discuss the solutions which contain a de Sitter 3-brane in the cascading DGP braneworld model, which is a kind of higher-dimensional generalizations of the DGP model,where a $p$-dimensional brane is placed on a $(p+1)$-dimensional one and the $p$-brane action contains the $(p+1)$-dimensional induced scalar curvature term. In the simplest six-dimensional model, we derive the solutions. Our solutions can be classified into two branches, which reduce to the self-accelerating and normal solutions in the limit of the original five-dimensional DGP model. In the presence of the six-dimensional bulk gravity, the `normal' branch provides a new self-accelerating solution. The expansion rate of this new branch is generically lower than that of the original one, which may alleviate the fine-tuning problem.