"Faster Than Light" Photons in Dilaton Black Hole Spacetimes

TL;DR

This paper explores how photons can appear to travel faster than light in dilaton black hole spacetimes, revealing modifications to light propagation due to dilatonic effects near the horizon.

Contribution

It demonstrates the impact of dilaton fields on photon light-cone conditions and extends Shore's theorems to these black hole solutions.

Findings

Radial photons have modified light-cone conditions.

Dilatonic effects dominate near the horizon in extremal cases.

Photon behavior aligns with Shore's horizon theorem and polarization sum rule.

Abstract

We investigate the phenomenon of "faster than light" photons in a family of dilaton black hole spacetimes. For radially directed photons, we find that their light-cone condition is modified even though the spacetimes are spherically symmetric. They also satisfy the "horizon theorem" and the "polarization sum rule" of Shore. For orbital photons, the dilatonic effect on the modification of the light-cone condition can become more dominant than the electromagnetic and the gravitational ones as the orbit gets closer to the event horizon in the extremal or near-extremal cases.