A Slant on Warped Extra Dimensions
  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.
