If the Universe is flat and the total energy of the universe can be zero (we don't know if it is, but many theorists support the idea, i.e. at BB initial conditions: t = 0, V = 0, E = 0) then is it possible that all matter in the universe could have emerged from nothing? If so, that what is the total energy of the matter compensated by?
Edit: Yes, I've watched the lecture by Lawrence Krauss, and I know about his book. Haven't read it though (I guess it's too difficult for me).