# Degravitation and the Cascading DGP Model

## Abstract

**:**

## 1. Introduction

^{−3}eV, to the value inferred by observations, it is not expected to remain small when we consider higher energy descriptions where new particles enter in the effective Lagrangian. In other words, the smallness of the Cosmological Constant is not technically natural (in a Wilsonian sense) [3].

## 2. The 6D Cascading DGP Model

## 3. De Sitter Solutions

#### 3.1. Symmetry Properties and Gauge Choice

- The bulk can be foliated into 4D leaves, whose (pseudo-Riemannian) induced metric is spatially homogeneous and isotropic.
- The translations along the 3D spatial dimensions are a symmetry of the bulk metric.
- There exists a smooth hypersurface $\Sigma $ with respect to which the bulk is ${\mathbb{Z}}_{2}$-symmetric. The codimension-2 brane coincides with the intersection of $\Sigma $ and the codimension-1 brane.
- The ${\mathbb{Z}}_{2}$-symmetry and the foliation into spatially homogeneous and isotropic leaves are compatible.

#### 3.1.1. The Bulk

#### 3.1.2. The Branes

#### 3.2. Degrees of Freedom and Flat Bulk Configurations

## 4. The Role of the Bulk Equations

#### 4.1. Initial Value Analysis

#### 4.2. Diagonal Solutions

#### 4.3. De Sitter Solutions Again

## 5. Conclusions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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1. | The codimension of a brane is defined as the difference between the dimension of the ambient spacetime and the dimension of the brane. |

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Sbisà, F.
Degravitation and the Cascading DGP Model. *Universe* **2018**, *4*, 136.
https://doi.org/10.3390/universe4120136

**AMA Style**

Sbisà F.
Degravitation and the Cascading DGP Model. *Universe*. 2018; 4(12):136.
https://doi.org/10.3390/universe4120136

**Chicago/Turabian Style**

Sbisà, Fulvio.
2018. "Degravitation and the Cascading DGP Model" *Universe* 4, no. 12: 136.
https://doi.org/10.3390/universe4120136