I was thinking of stable wormholes, held open by exotic matter--this is the most common scenario when discussing time travel in GR. Travelling through a ring singularity might take you some unknown region of spacetime, but there's no reason to think it would be your own past...time-reversal invariance has nothing to do with time travel (after all, Newtonian laws are time-reversible too), and I'm not familiar with the term "split event horizons". (a google search only turns up 19 hits, are you sure you have the term right?)Danger said:While I'm somewhat familiar with the concept from the perspective of ring singularities, split event horizons, antimatter time-reversal invariance and whatnot
But when you were talking about paradoxes and the impossibility of time travel, it seemed like you were using "impossible" in the sense of what's allowed by the laws of nature, not in terms of practical engineering issues. If something leads to a genuine paradox, it must be logically impossible, not just impossible in practice.Danger said:I don't believe that it will ever be technologically possible to transfer anything macroscopic into the past in any condition to affect causality. I'm not sure about that, of course, but it seems extremely unlikely to me.