Low energy effective theory on a regularized brane in 6D gauged chiral supergravity

TL;DR

This paper derives a low energy effective theory for a 6D brane in chiral supergravity, revealing a Brans-Dicke type scalar-tensor gravity with potential implications for cosmology and the cosmological constant problem.

Contribution

It introduces a regularized brane setup in 6D supergravity and derives the effective Brans-Dicke theory with a specific parameter, linking moduli stabilization to cosmological applications.

Findings

Effective theory is Brans-Dicke with ω=1/2.

Time-dependent solutions can be lifted to 6D exact solutions.

Potential for modulus stabilization to recover standard cosmology.

Abstract

We derive the low energy effective theory on a brane in six-dimensional chiral supergravity. The conical 3-brane singularities are resolved by introducing cylindrical codimension one 4-branes whose interiors are capped by a regular spacetime. The effective theory is described by the Brans-Dicke (BD) theory with the BD parameter given by $\omega_{\rm BD}=1/2$. The BD field is originated from a modulus which is associated with the scaling symmetry of the system. If the dilaton potentials on the branes preserve the scaling symmetry, the scalar field has an exponential potential in the Einstein frame. We show that the time dependent solutions driven by the modulus in the four-dimensional effective theory can be lifted up to the six-dimensional exact solutions found in the literature. Based on the effective theory, we discuss a possible way to stabilize the modulus to recover standard cosmology and also study the implication for the cosmological constant problem.