# Why not an equal amount of matter and antimatter in the universe?

1. May 20, 2013

### Mpcahn

Couldn't there be an equal amount of matter and antimatter in the universe. While from what I've read there is little antimatter in the universe as we see it. Isn't it a leap to assume that the universe at the Big Bang had slightly more matter than antimatter? Isn't it just as likely that there still is the same amount of antimatter and matter in the universe, but the reason were here is the lumpy nature of the early universe had it so our little observable corner of it had more matter than antimatter and now matter is just about all we can see? Couldn't there be another corner of the universe beyond our observable horizon where there are galaxies made of antimatter and living beings who call it matter and wonder why there isn't more antimatter?

Just some food for thought.

2. May 20, 2013

### kurros

For this to be possible there would need to be significant anisotropies in the matter/anti-matter distribution pretty early on during inflation I believe, which I don't think is the case in most models. I don't know enough about inflation to say much more though.

3. May 20, 2013

### Mpcahn

Isn't "anisotropy" a property not a thing. Anisotropy being not uniform, isotropy being uniform? The microwave background looks quite anisotropic. Thanks for a more scientific sounding word for "lumpy." I'll do the math when I learn it. I'm about 3/4 of the way through Khan Academies maths sequence. What else do I need to learn to attempt to make a proof?

4. May 20, 2013

### Mpcahn

5. May 21, 2013

### kurros

Not sure what you are getting at. Yes I mean "not uniform". As for the microwave background, it only looks anisotropic in the pretty pictures people show of it because it has had the much larger isotropic component subtracted off. The temperature fluctuations are around 18 microKelvin, while the average temperature is 2.7 Kelvin. So the anisotropies are very very small (see https://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation#Features).

A proof of how CMB anisotropies constrain your proposal? Really a very large amount I'm afraid. You'll probably need at least a masters in cosmology.

6. May 21, 2013

### Mpcahn

Yeah, sounds like a topic for a Ph.D. thesis. My guess would be a full time investment of about 4 years. And I guess "proof" wouldn't be the right word either. I'll keep chipping away at it in my spare time. I have too many idea's like this and my guess is most of them are wrong. But I'll get wiser learning which is and which isn't.

7. May 21, 2013

### Mpcahn

Actually could the mod's move this thread to the cosmology subforum? Didn't realize you had one until now.

8. May 22, 2013

### Mordred

What you are after in the matter antimatter question in regards to the universe is described by the particke physics term baryogenesis.

http://en.m.wikipedia.org/wiki/Baryogenesis

During the first moments of of the early universe matter and anti matter were balanced. For reasons covered on the wiki page an imbalance occurs favouring matter.

Coincidentally there is another related new thread.

Last edited: May 22, 2013
9. May 22, 2013

### Mordred

Isotrophy is no preferred direction. Anistrophy is the opposite.

Homogeneous is no preferred location one spot is the same as another.

both combined signify uniformity at needed size scales.

10. May 22, 2013

### kurros

Ahh yes, thanks, the homogeneity is important, I should have mentioned it.

11. May 22, 2013

### Mordred

12. May 22, 2013

### Mpcahn

Thanks Mordred! I'll have to take some time to do the necessary research to understand this paper.

13. May 22, 2013

### Mordred

Well if your looking for info on understanding that look at CP violations. Early particle QFT articles.

This resource may help it covers all the needed maths but it requires good math skills and some previous knowledge.

be forwarned it 889 pages long but it covers classical and quantum fields of a large variety.

CP violations is included.

http://arxiv.org/abs/hepth/9912205

14. May 22, 2013

### Just Steve

By anti-matter I assume you mean 'dark matter" which is not quantifiable by observation, but should be present by mathematical calculation. This could be due to the fact that we as humans can only perceive reality in three dimensions. What if the universe is not as it appears? If there are more (such as the multi-verse theory) dimensions, we would need a way to perceive and interpret those other dimensions...

15. May 22, 2013

### Hypersphere

I'm pretty sure he actually meant antimatter, i.e. matter in the form of antiparticles. You might want to take a look at http://en.wikipedia.org/wiki/Antiparticle

16. May 24, 2013

### DrChinese

If there had ever (after the appearance of the CMB) been a region of space dominated by antimatter, I believe there would also have been a boundary between that region and the one we occupy (which is matter dominated). At that boundary, I would expect there to be ongoing matter-antimatter annihilation which should leave a detectable signature in the form of gamma radiation. Since we see no such signature, I would conclude that there is no such boundary and therefore no antimatter region. (Although I could be wrong about this.)