Originally Posted by omegaman
As I understand it Nero and Spock are thrown back in time of their own timeline where events then create the alternate timeline. This event occurs in the current Universe NOT a parallel one. Therefore single Universe, alternate timeline. NOT Parallel Universe, parallel timeline.
Travelling back in time creates
the alternate universe from that poin on, in accordance with Quantum Physics.
This is according to the writers, and is supported by brief dialog in the movie.