I have already contradicted David Deutsch and his 'Multiverse' in print, many years ago as well as various other dumbassery. Still, he is an Oxford professor and I am a farmer – which surely means something….oh yes…that I am smarter than he.
His theory postulates that every possible outcome or variation of any event OR POTENTIAL EVENT – even down to the random decay of a particle – must ALL occur simultaneously in different universes.
I impolitely pointed out that if everything happened at once – even in different universes – time could not exist between universes – and that every possible outcome of every event in any OTHER universe would also have to occur in ours. Nothing in any multiverse theory states that our universe must be the 'trigger' universe and that all other universes are created instantly every time something happens – OR DOES NOT HAPPEN – in our universe. That is not a physical theory. It is a God theory and it makes no sense.
But because no one understands multiverse theory (because it cannot be understood), no one contradicts Deutsch because they don't want to appear not to understand something that they think someone else understands. It is very like string theory which has never made a testable prediction because ALL of the variables are arbitrary.
It seems rather inescapable to me that following Deutsch's own theory, every possible outcome of every event would have to happen at once in all of the universes. Universes would therefore not be able to exist past the point of singularity – and even that would be unable to exist.
Without time, nothing exists because, of course, it doesn't have time to exist. I believe Discovery or Science printed that some years ago. Deutsch failed to respond.
I may have also pointed out that exceeding the speed of light neither exceeds nor negates the speed of time.