AntiMatter/Matter balance in the Universe

GammaBurst

Why does the amount of antimatter equal the amount of matter in the universe. If they go in pairs and are opposites one must exist for the other to exist. Why is matter more abundant in our universe and what has happend to the antimatter?

mjsd

the true origin of the matter and antimatter asymmetry is still an open question. but there are some proposed models that attempts to explain this:
GUT baryogenesis
SUSY EW baryogenesis
(non-)thermal Leptogenesis
etc.
In all these models the asymmetry is generated dynamically as the universe expands and assume that
somehow baryon/lepton numbers are violated, C/CP is violated and if CPT is exact then these violating processes must also be out of equilibrium.

CompuChip

And if anyone knows the "real" answer, they can probably submit for a Nobel prize.

ranger

Well thats the key word there - our universe. For the latter part of your question, we can speculate things such as an anitimatter universe, where everything is made of antiparticles

http://physicsworld.com/cws/article/print/61

SpitfireAce

well.... if you believe in the grand unification theory... the SU(5) group predicts 2 never observed bosons, the X and Y bosons. These bosons can change quarks into leptons and vise versa... which overthrows the notion of baryon number conservation. In the OP you were probably referring to particle-antiparticle pair production.. But these proposed mediators open up the possibility of essentially making matter without simultaneously making antimatter. The problem is that these bosons are so massive and weak that it would take 10^30 years for a neutral pion and a positron to turn into a proton via the X-boson. But at the energies just after the big bang, the X-boson was massless and interacted as often as any photon... thus protons were constantly being created. You might be thinking... well the protons would decay just as rapidly and there would be an equilibrium, or anti-protons would be created at the same rate... but... the existence of CP violation (symmetry by charge and parity reversal) opens up the possibility that the production of matter might have a slight edge over antimatter production and matter decay. Personally, I think that this gives the existence of CP violation meaning... if it were not for this violation the universe would be pure, free of matter.

filegraphy

First welcome to Physics Forum. Also the muon and the anitmuon (heavy version of the electron) were created unequally. Of course there is much more, but that is how much I know. The muon quantity was larger than the quantity of the antimuon. Like I said this could apply to many other particles, but this is what I know.

rcgldr

Why should it be expected that matter and anti-matter (oppositely charged electrons and protons) should be created equally?

Also anti-matter is really mis-named, since it only refers to the charged state of particles. True "anti-matter" should have properties like "anti-gravity".

filegraphy

I would assume that it would be the balance of nature. Energy creates matter and it's opposite in equal quantities. It is not that way though.

mathman

If one is concerned only with numbers, it is possible that the number of antileptons (antineutrinoes?) is larger than the number of leptons, keeping the total number of antimatter particles equal to the total number of matter particles.

ZapperZ

Please note that until it was resurrected today, the last post in this thread was from 2007!

There are already many threads in the High energy physics forums that discussed the matter-antimatter imbalance, including the recent results of CP-violation. Please continue this there.

lazypast

i wonder if we can answer a question like this with anymore insight than we could in 2007 :)

cubzar

Since antimatter has negative mass, it seems likely that gravity attracts matter to matter and antimatter to antimatter, but repels matter away from antimatter. Gravity could therefore cause matter and anti-matter to accumulate in different regions of the universe, although gravity is comparatively weak so most of the matter would be annihilated.

CompuChip

Since when is that?

filegraphy

I thought that I read in a science news article about a test they did with muons and how more matter was produced than antimatter. And I agree with CompuChip. Any thoughts or comments?

filegraphy

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