There is no empirical evidence for multiple universes, but some paradigms suggest otherwise. A logical question to ask in such cases is: how is time correlated between universes, if they can interact in some way? There is an implicit exophysical architecture that is necessary in those conjectured models to coordinate each universe with the others, so as to account for quantum interference for instance: such a process is asserted to occur in the Multiverse paradigm [Deutsch, 1997]. Such models are invariably contextually incomplete in their architecture and are therefore metaphysical.
Time travel stories invariably require some form of postulated architecture that departs from the linear time Block Universe model. As with the Multiverse paradigm, lack of detail prevents counterarguments to be presented. Novel forms of temporal architectures such as wormholes, ansibles, and hyperspace are posited with no details. A century earlier, such stories would have been classified as fairy stories.
There is one reputable scenario where the architecture of time travel can be discussed in a meaningful way, and that is in general relativity. There we find spacetimes that allow for closed timelike curves (CTCs), or loops in spacetime that an endophysical observer could follow. An important paper on this topic was given by the logician Godel in 1949: we discuss that paper in Chapter 20.
-  Devices that permit instantaneous communication across vast distances.