Superluminal anisotropic propagation and wavefront splitting on tilted and boosted braneworlds

Abstract

Braneworlds winding and spinning around an extra compact dimension manifest superluminal propagation for fields penetrating the bulk. This propagation is either irreducibly anisotropic or one that becomes isotropic in a special frame, depending on the brane's motion and orientation in the bulk. For a class of boosted observers on the brane the wavefront of such fields will split into two hyperboloid components, one propagating forward and the other backward in time at superluminal speeds. In spite of these effects, there is no violation of causality and no tachyons. Detection of astrophysical anisotropic superluminal propagation velocities would offer a sign for the existence of extra compactified dimensions and information on the state of our braneworld in the bulk.