When we die, do we cease to exist in ALL parallel universes?

First I would want to know about "Reality" of the Parallel Universes itself. Have they not arisen out of the mathematical solutions to the equations only and not necessarily out of easily demonstrable experiments? When I say experimental demonstration, I mean this: Lets suppose you conducted an experiment in which you wanted to study an event; Like, trying to find the constituents of the neutrino for instance. Being such a short lived particle whose existence to manifest in an experiment itself is a one in a trillion-trillion possibility! You study whatever scraps of evidence of the activity, that had happened, and the detectable trace left behind, and formulate a "mathematical equation" to describe the situation- In the process of analysing one such equation you come up with the idea of giving "reality" to all of your solutions to the equation, unlike in the case of Classical Physics where you simply dismiss out of hand the several other possibilities as unconnected with reality. IMO Parallel Universes is one such exercise. If there are n-solutions possible for a personality like me to exist then there are 'n' such Universes in which n-sequences of possible events describe me and my parallels taken together. But what relation has the reality of the 'other universe' of the 'other me' has for me of this Universe, unless I can "visit" the "other" Universe and see for myself, that there are sequences of events which might interest me happening there? IOW if there is no journey to enter the "other" Universe of what use is knowing that they even exist?