CALLING MR. PEABODY: Time Travel Could Be Enabled by Circulating Lasers. “Ron Mallet has found the exterior gravitational field contains closed timelike lines. The strong gravitational field can be produced by a circulating cylinder of light.”

I looked at the actual paper and it says closed timelike curved lines, meaning that they eventually loop back to the same time and place. The author summarizes: “The presence of closed timelike lines indicates the possibility of time travel into the past. This creates the foundation for a time machine based on a circulating cylinder of light.”