Wave Fronts in a Causality-Violating Gödel-Type Metric

Figure 2

(a) A plot of the spatial path in the plane of a light ray with , , and initial positive for where the light ray starts at the origin and moves counterclockwise. (b) A plot of the time coordinate for this null geodesic as a function of the affine parameter. According to an observer at the origin, at the point labeled , a “blue sky” appearance of a pair of light pulses appears, moving along the closed curve in opposite directions. At the point labeled , one part of the pair meets up with the original pulse from the origin and the pair disappears.

(a)

(b)