Parallel Universe - Multiverse do they exist and where?

For the multiverse is a set of coexisting and alternative universes outside of our spacetime, often referred to as parallel dimensions, which can arise as a result of some scientific theories. The concept of a multiverse is also taken as the setting for many novels of science fiction or fantasy fiction. The multiverse concept of fantasy and science fiction inspired by the cosmologico.Livello III (Interpretation Multimondo Hugh Everett III): This is an interpretation of quantum mechanics that suggests the existence of multiple universes all having the same physical constants but are differ in what happens to them: for example, if an elementary particle in a universe undergoes the tunnel effect, in another it does not, in the same way, again by way of example, a man could be killed in a universe but not in another and so on. Many believe that Everett's interpretation is conservative extension of standard quantum mechanics, which means that if you are unable to express his results in the language of ordinary quantum mechanics, it does not lead to new universes with different physical laws and constants , that is covered by the new non-physical results without interpretation  , what makes it unnecessary from the point of view of Ockham's Razor. This, according Tegmar,  "is an ironic, since this level has been historically the most controversial." In September 2007, David Deutsch has presented what is considered a test of many-worlds interpretation.