Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Cascading Gravity and Degravitation

Claudia de Rham, Stefan Hofmann, Justin Khoury, Andrew J. Tolley

TL;DR

The paper develops a Cascading DGP framework where gravity transitions from higher-dimensional behavior at large scales to four-dimensional gravity at short scales by embedding our 3-brane in a sequence of higher-dimensional branes with their own induced gravity terms. It identifies and cures ghost instabilities inherent in higher-codimension setups by introducing gauge-invariant brane regularizations (Stückelberg, spherical, and medium approaches) and demonstrates, both in a decoupling-limit analysis and through effective field theory, that a ghost-free, ghost-eliminated propagator with the correct tensor structure can persist across scales. The result is a consistent IR modification of gravity capable of effectuating degravitation of vacuum energy while preserving phenomenology via Vainshtein screening and scale-dependent gravity. This work thus provides a concrete nonlinear realisation of degravitation and lays the groundwork for further cosmological investigations into dynamical, degravitating solutions of the cosmological constant problem.

Abstract

We construct a cascading brane model of gravity in which the behavior of the gravitational force law interpolates from (n+4)-dimensional to (n+3)-dimensional all the way down to 4-dimensional from longer to shorter length scales. We show that at the linearized level, this model exhibits the features necessary for degravitation of the cosmological constant. The model is shown to be ghost free with the addition of suitable brane kinetic operators, and we demonstrate this using a number of independent procedures. Consequently this is a consistent IR modification of gravity, providing a promising framework for a dynamical, degravitating solution of the cosmological constant problem.

Cascading Gravity and Degravitation

TL;DR

The paper develops a Cascading DGP framework where gravity transitions from higher-dimensional behavior at large scales to four-dimensional gravity at short scales by embedding our 3-brane in a sequence of higher-dimensional branes with their own induced gravity terms. It identifies and cures ghost instabilities inherent in higher-codimension setups by introducing gauge-invariant brane regularizations (Stückelberg, spherical, and medium approaches) and demonstrates, both in a decoupling-limit analysis and through effective field theory, that a ghost-free, ghost-eliminated propagator with the correct tensor structure can persist across scales. The result is a consistent IR modification of gravity capable of effectuating degravitation of vacuum energy while preserving phenomenology via Vainshtein screening and scale-dependent gravity. This work thus provides a concrete nonlinear realisation of degravitation and lays the groundwork for further cosmological investigations into dynamical, degravitating solutions of the cosmological constant problem.

Abstract

We construct a cascading brane model of gravity in which the behavior of the gravitational force law interpolates from (n+4)-dimensional to (n+3)-dimensional all the way down to 4-dimensional from longer to shorter length scales. We show that at the linearized level, this model exhibits the features necessary for degravitation of the cosmological constant. The model is shown to be ghost free with the addition of suitable brane kinetic operators, and we demonstrate this using a number of independent procedures. Consequently this is a consistent IR modification of gravity, providing a promising framework for a dynamical, degravitating solution of the cosmological constant problem.

Paper Structure

This paper contains 22 sections, 118 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Review of the Degravitation Phenomenon
  3. Spectral Representations
  4. Cascading Scalars
  5. Codimension-two case
  6. General Codimension-$n$
  7. Cascading Gravity
  8. Brane Regularizations
  9. Stückelberg Approach
  10. Spherical Regularization
  11. Medium Model
  12. Effective Theory Approach
  13. Ghost-free Cascading Gravity
  14. Curing the Ghost in the Decoupling Limit
  15. Strong Coupling Phenomenon
  16. ...and 7 more sections

Figures (1)

  • Figure 1: Coupling corrections to the two-point function. The Green's function on the codimension-$m$ brane is related to that on the codimension-$(m-1)$, $\mathcal{G}_{m-1}(p)$. $\lambda_m$ is the coupling associated with $\mathcal{L}_{\rm{coupling}}^{\rm{cod-m}}$: $\lambda_m=-M_{4+n-m}^{2+n-m}$p^2+q_1^2+⋯+q_n-m^2$$.