Notes on the Two-brane Model with Variable Tension

TL;DR

This paper explores the implications of variable brane tensions in two-brane models, revealing constraints, effects on fine-tuning, and potential early universe bouncing behavior, with discussions on anisotropy and branons.

Contribution

It introduces modified sum rules for variable brane tensions and analyzes their effects on brane dynamics and fine-tuning issues in braneworld models.

Findings

Tensions obeying Eotvos law aggravate fine-tuning problems.

Hidden brane tension influences visible brane behavior, allowing bouncing phases.

Qualitative features include anisotropic backgrounds and branons production.

Abstract

Motivated by possible extensions of the braneworld models with two branes, we investigate some consequences of a variable brane tension using the well established results on consistency conditions. By a slight modification of the usual stress-tensor used in order to derive the braneworld sum rules, we find out some important constraints obeyed by time dependent brane tensions. In particular it is shown that the tensions of two Randall-Sundrum like branes obeying, at the same time, an Eotvos law, aggravate the fine tuning problem. Also, it is shown that if the hidden brane tension obeys an Eotvos law, then the visible brane has a mixed behavior allowing a bouncing-like period at early times while it is dominated by an Eotvos law nowadays. To finalize, we discuss some qualitative characteristics which may arise in the scope of dynamical brane tensions, as anisotropic background and branons production.