Effective Lagrangian and stability analysis in warped space

TL;DR

This paper derives the effective Lagrangian for radion stabilization in warped space models, clarifying the dynamical degrees of freedom and generalizing the Goldberger-Wise mechanism to N-brane setups.

Contribution

It provides a complete quadratic-order effective Lagrangian derivation for N-brane warped models, extending the Goldberger-Wise stabilization method.

Findings

Only one radion degree of freedom is dynamical in N-brane models.

The derived Lagrangian matches linearized Einstein equation analysis.

The stabilization mechanism can be generalized to N-brane setups.

Abstract

In the warped space model, the inter-brane distance can be stabilized by the Goldberger-Wise mechanism. Of particular importance, the stabilization potential calls for a proper identification of the dynamical degree of freedom. In this paper, we provided a complete calculation of the effective Lagrangian till the quadratic order that is generic for the Randall-Sundrum model and its $N$-brane $(N \geq 4)$ extensions. By applying the variation principle to a specific perturbation field, we derived the equations of motion and orthogonal conditions for decoupling the graviton. This approach is demonstrated to be equivalent to the analysis using the linearized Einstein equation. Our derivation clarifies that in the $N$-brane set up, just one degree of freedom for the radion field is dynamical, with the other modes eliminated by the gauge fixings. Thus we can directly generalize the GW stabilization to the $N$-brane model in a way similar to the RS1 scenario.