I don't argue multiverse theory. I just don't think the movie is successful in communicating that the time travel in this instance created a parallel universe.
I honestly don't mean to be frank, but how else could they communicate it any more successfully than the characters blatantly (and rather clumsily) stating it in the middle of the movie?
...
You mean:"An alternate reality"? Not conclusive IMO, especially when the rest of the movie is either compatible with a single timeline or seems to imply it. I have answered your question of how they could have better indicated what was going on here. Basically you show a shotgun* hanging on the wall then later you have someone take it down and use it. Simple.

* In this case (perhaps an academy discussion etc of ) multiverse theory.
PS. I guess technically it isn't the time travel that inherently creates the alternative universe but the arrival of Nero in the past. On the other hand, while it may or may not have been possible for him to fall into a black hole (depending on how bad the plot is!


