Far out cosmology: why matter more than antimatter? (Introduction)

by David Turell , Tuesday, April 28, 2020, 23:22 (1668 days ago) @ David Turell

The answer is we do not know. Sabine Hossenfelder has a different view of the entire issue:

http://backreaction.blogspot.com/2020/04/no-physicists-have-not-explained-why.html

"every couple of months I have to endure yet another media blast about physicists who may have solved a problem that does not exist in the first place.

"The most recent installation of this phenomenon are loads of articles about the recent T2K results that hint at CP violation in the neutrino sector. Yes, this is an interesting result and deserves to be written about. The problem is not the result itself, the problem is scientists and science writers who try to make this result more important than it is.

"You can see for yourself what the problem is by reading the reports in the media. Not a single one of them explains why anyone should think there ever were equal amounts of matter and anti-matter to begin with. Leah Crane, for example, writes for New Scientist: “Our leading theories tell us that, in the moments after the big bang, there was an equal amount of matter and antimatter.”

"But, no, they do not. They cannot. You don’t even need to know what these “leading theories” look like in detail, except that, as all current theories in physics, they work by applying differential equations to initial values. Theories of this type can never explain the initial values themselves. It’s not possible. The theories therefore do not tell us there was an equal amount of matter and antimatter. This amount is a postulate. The initial conditions are always assumptions that the theory does not justify.

"Instead, physicists think for purely aesthetic reasons it would have been nicer if there was an equal amount of matter and antimatter in the early universe. Trouble is, this does not agree with observation. So then they cook up theories for how you can start with an equal amount of matter and anti-matter and still end up with a universe like the one we see. You find a good illustration for this in a paper by Steigman and Scherrer with the title “Is The Universal Matter - Antimatter Asymmetry Fine Tuned?” (arXiv:1801.10059) They write:

“'One possibility is that the Universe actually began in an asymmetric state, with more baryons and antibaryons. This is, however, a very unsatisfying explanation. Furthermore, if the Universe underwent a period of inflation (i.e., very rapid expansion followed by reheating), then any preexisting net baryon number would have been erased. A more natural explanation is that the Universe began in an initally [sic] symmetric state, with equal numbers of baryons and antibaryons, and that it evolved later to produce a net baryon asymmetry.'”

Comment: Hossenfelder's point is simple. There is no proof there were equal amounts of matter and antimatter in the beginning. The asymmetry may have been there at the start.