I was reading some texts explaining that since our region of the world is overwhelmingly dominated by matter, and not by anti-particles, this suggests that in some region of the universe, there will be a region dominated by anti-matter.
Why must there exist a region dominated by anti-matter?
I could guess at an answer, but can't say it mathematically:
Is it an issue of symmetry, that is, for each matter particle, we have an antimatter one? In other words, if my universe has two protons, does it need to have two antiprotons too?