A Slant on Warped Extra Dimensions

TL;DR

This paper explores a warped extra dimension model with tilted branes, leading to Lorentz violation in our universe, and examines observational constraints from astrophysical measurements on the model's parameters.

Contribution

It introduces a novel brane tilting scenario in warped extra dimensions that naturally causes Lorentz violation and analyzes its observational constraints.

Findings

Lorentz violation depends on brane tilt parameter

Electron-proton mass ratio measurements constrain tilt

Future radio source observations could tighten constraints

Abstract

We propose an orbifolded, warped, extra dimension scenario in which the visible brane is not parallel to the hidden brane. This leads automatically to Lorentz violation in the visible, four dimensional world. The background solution to the Einstein equations is a function of a parameter that can be identified with the amount of 'tilting' of the brane. The cosmological constant is found to coincide with the classic Randall-Sundrum value to first order in this tilt. Lorentz violating effects induced in the Standard Model are considered. We find that the strongest constraint on the tilt comes from determinations of the electron-proton mass ratio in six quasar spectra (four optical and two radio). Measurements of a third radio source could improve this by an order of magnitude.