I meant more along the lines of when the assumptions aren't met, e.g. P(B) == 0.
Or, where unitarity in physics isn't met:
http://en.wikipedia.org/wiki/Unitarity_(physics)
I meant more along the lines of when the assumptions aren't met, e.g. P(B) == 0.
Or, where unitarity in physics isn't met:
http://en.wikipedia.org/wiki/Unitarity_(physics)