Superluminal propagation of light in gravitational field and non-causal signals

TL;DR

This paper explores how quantum corrections can cause light to travel faster than light in gravitational fields, potentially enabling closed time-like trajectories and challenging previous claims about causality.

Contribution

It demonstrates that superluminal light propagation could lead to closed time-like curves, contradicting earlier assertions that such effects do not violate causality.

Findings

Superluminal light propagation can enable closed time-like trajectories.

Photons could theoretically return to their source before emission.

This challenges previous claims about causality preservation.

Abstract

It has been found in several papers that, because of quantum corrections, light front can propagate with superluminal velocity in gravitational fields and even in flat space-time across two conducting plates. We show that, if this is the case, closed time-like trajectories would be possible and, in particular, in certain reference frames photons could return to their source of origin before they were produced there, in contrast to the opposite claim made in the literature.