As often portrayed in science fiction, with a time machine, nothing is permanent anymore — you can always go back and change it. But is time travel really possible in our Universe, or is it just science fiction? Shoshany et al. define and analyze a new model of time travel paradoxes, which is fully compatible with all known physics; the model consists of a wormhole time machine in 3+1 spacetime dimensions, which can be either permanent (existing...
