Abstract
We consider the 6D Cascading DGP model, a braneworld model which is a promising candidate to realize the phenomenon of the degravitation of vacuum energy. Focusing on a recently proposed thin limit description of the model, we study solutions where the induced metric on the codimension-2 brane is of the de Sitter form. While these solutions have already been recovered in the literature imposing by hand the bulk to be flat, we show that it is possible to derive them without making this assumption, by solving a suitably chosen subset of the bulk equations.
Highlights
The Cosmological Constant (CC) problem [1,2] is one of the most striking puzzle in contemporary physics
In a very basic sense, it stems from the fact that in General Relativity (GR) the gravitational field is sensitive to energy and momentum themselves, and not just to the energy difference with respect to a reference (“zero”) configuration
At semi-classical level, where the spacetime is held classical while the matter fields are quantized, the geometry is expected to be sourced by the quantum expectation value of the energy momentum operator, which is badly divergent
Summary
The Cosmological Constant (CC) problem [1,2] is one of the most striking puzzle in contemporary physics. At semi-classical level, where the spacetime is held classical while the matter fields are quantized, the geometry is expected to be sourced by the quantum expectation value of the energy momentum operator, which is badly (quadratically) divergent While this vacuum energy could be renormalized, at the cosmological energy scale 10 ́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. The possible existence of extra dimensions opens a new avenue in this direction, allowing vacuum energy being huge while producing substantial effects only in the extra dimensions [4] Compelling in this sense are the braneworld models [5,6], where our universe is a surface (brane) embedded in a higher dimensional spacetime. To reproduce the successes of GR, a “high-pass filter” behaviour is invoked, in such a way that only sources smooth on cosmological scales, such as vacuum energy, get degravitated
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