We investigate spacetimes in which the speed of light along flat 4D sections
varies over the extra dimensions due to different warp factors for the space
and the time coordinates (``asymmetrically warped'' spacetimes). The main
property of such spaces is that while the induced metric is flat, implying
Lorentz invariant particle physics on a brane, bulk gravitational effects will
cause apparent violations of Lorentz invariance and of causality from the brane
observer's point of view. An important experimentally verifiable consequence of
this is that gravitational waves may travel with a speed different from the
speed of light on the brane, and possibly even faster. We find the most general
spacetimes of this sort, which are given by certain types of black hole
spacetimes characterized by the mass and the charge of the black hole. We show
how to satisfy the junction conditions and analyze the properties of these
space-times.Comment: 5 pages, LaTeX, JHEP3.cls. To appear in the Proceedings of the EPS
2001 International Europhysics Conference on HEP, Budapest, July 12-18, 200
