Brane Stabilization and Regionality of Extra Dimensions

TL;DR

This paper investigates how the Casimir effect and geometric factors influence the stabilization of branes within extra-dimensional spaces, highlighting the importance of bulk structure and boundary conditions in braneworld models.

Contribution

It generalizes previous work by analyzing additional bulk and brane dimensions, boundary conditions, and toy models, emphasizing the role of Casimir energy in brane stabilization.

Findings

Stable minima of the effective potential can arise from competing energy contributions.

Casimir energy plays a significant role in stabilizing branes in complex bulk geometries.

Different boundary conditions and geometries affect the stabilization mechanism.

Abstract

Extra dimensions are a common feature of beyond the Standard Model physics. In a braneworld scenario, local physics on the brane can depend strongly on the brane's location within the bulk. Generically, the relevant properties of the bulk manifold for the physics on/of the brane are neither local nor global, but depend on the structure of finite regions of the bulk, even for locally homogeneous and isotropic bulk geometries. In a recent work, various mechanisms (in a braneworld context) were considered to stabilize the location of a brane within bulk spaces of non-trivial topology. In this work we elaborate on and generalize that work by considering additional bulk and brane dimensionalities as well as different boundary conditions on the bulk scalar field that provides a Casimir force on the brane, providing further insight on this effect. In D=2+1 (D=5+1) we consider both local and global contributions to the effective potential of a 1-brane (4-brane) wrapped around both the 2-dimensional hyperbolic horn and Euclidean cone, which are used as toy models of an extra-dimensional manifold. We calculate the total energy due to brane tension and elastic energy (extrinsic curvature) as well as that due to the Casimir energy of a bulk scalar satisfying both Dirchlet and Neumann boundary conditions on the brane. In some cases stable minima of the potential are found that result from the competition of at least two of the contributions. Generically, any one of these effects may be sufficient when the bulk space has less symmetry than the manifolds considered here. We highlight the importance of the Casimir effect for the purpose of brane stabilization.