[Profpat]

Hi JAK;

I hope you don't mind me butting in here, but Dirac tried unsuccessfully to discover anti-matter in our universe. He gave up on his theory lacking any evidence. He never considered an anti-parallel universe, that I'm aware of however.

You are correct that two photons are created when a particle annihilates with an anti-particle. Since the photon has no charge it is it's own anti-particle. If the photons have enough energy they will create a particle and anti-particle.

Best to all,

Pat