Anti Dark Matter?

[Earl]

As Matter has Anti matter does Dark Matter have Anti Dark Matter?

[Earl]

Or is the term Dark Anti matter?

[Stephen]

Anti dark matter is perfectly feasible IF dark matter is actually slow moving particles.

Not knowing what it is .... makes things a little difficult

Of course if we conclude this, then it has to be explained why there is so much more dark matter than anti dark matter .... and it took a long time to explain why there is so much more matter than anti matter

[JulianO]

The view is that dark matter particles are their own anti-particle (like the Z), so if two happen to collide they will annihilate each other. This is one of the ways people have tried detecting them, as large concentrations of DM particles, such as in the Sun or in galactic centres should give off a radiation signature. Unfortunately the flux is not going to be very high, and there is a lot of other causes of radiation so its difficult to pick out from the background of other sources.

E.g., http://arxiv.org/abs/1002.0197

[Stephen]

Don't electrically neutral (Z bosons) annihilations virtually never occur though?

Seems as pointless a task as waiting for a proton to decay

[JulianO]

Z particles decay anyway in pretty short order (~10^-25s) so the chance of two coming together is pretty remote!

Dark Matter particles have to be stable, otherwise they'd be no use as a source of gravity, so they've been around since the beginning of the universe. They do have a very small cross section of interaction though (being WIMPS and all ).

[ollypenrice]

Anti dark matter is perfectly feasible IF dark matter is actually slow moving particles.

Not knowing what it is .... makes things a little difficult

Of course if we conclude this, then it has to be explained why there is so much more dark matter than anti dark matter .... and it took a long time to explain why there is so much more matter than anti matter

:icon_scratch::)

Olly

[sologuitarist61]

I have just read the 'Talking Point' page in AN by Alan Longstaff and according to that dark matter is not doing what it should (or rather doesn't appear to be where it should be) in collisions between Galaxy clusters in Abell520.

Another study of 400 nearby stars in our neighbourhood, appears to show that there is no eveidence for dark matter at all. (For more info, read page 15 June AN)

So it maybe Earl that your question is academic anyway! :)

[JulianO]

I have just read the 'Talking Point' page in AN by Alan Longstaff and according to that dark matter is not doing what it should (or rather doesn't appear to be where it should be) in collisions between Galaxy clusters in Abell520.

Another study of 400 nearby stars in our neighbourhood, appears to show that there is no eveidence for dark matter at all. (For more info, read page 15 June AN)

So it maybe Earl that your question is academic anyway! :)

The paper showing no evidence is this one http://arxiv.org/abs/1204.3924

Just yesterday - a paper came out claiming that the analysis is wrong and that there is evidence of dark matter and at the expected amount, and the reason is the original paper did its sums wrong!

http://arxiv.org/abs/1205.4033

[sologuitarist61]

Thanks Julian will give that a read

[toml42]

I saw a paper a while back that actually proposed a starship engine under the assumption that dark matter was its own antiparticle.

It was a fun piece of speculation, a gigantic dark matter scoop would gather up the particles and force them together, similar in concept to the old bussard ramjet.

[JulianO]

I wonder how they made the scoop - it would be a bit like trying to catch clouds with a net!

[toml42]

Oh yes, they didn't explain that part of course :/ It was pretty interesting to see that in principle the energy density to do some work was there though - although not enough to get up to relativistic speeds.

http://arxiv.org/abs/0908.1429v1

[Ronnie67]

Good question.

Physicists in the US and Canada have proposed a new particle that could solve two important mysteries of modern physics: what is dark matter and why is there much more matter than antimatter in the universe?

The yet-to-be-discovered "X" particle is expected to decay mostly to normal matter, whereas its antiparticle is expected decay mostly to "hidden" antimatter. The team claims that its existence in the early universe could explain why there is more matter than antimatter in the universe – and that dark matter is in fact hidden antimatter.

Dark matter is a mysterious substance that appears to make up about 80% of the material universe. Although its existence can be inferred from its gravitational pull on normal matter, physicists have yet to detect it directly and therefore don't know what it is made of. Antimatter, on the other hand, is easy to create and study in the lab. However, the Standard Model of particle physics cannot explain why antimatter is so rare in a universe that is dominated by matter – a mystery called baryon asymmetry.

[JulianO]

Good question.

Physicists in the US and Canada have proposed a new particle that could solve two important mysteries of modern physics: what is dark matter and why is there much more matter than antimatter in the universe?

The yet-to-be-discovered "X" particle is expected to decay mostly to normal matter, whereas its antiparticle is expected decay mostly to "hidden" antimatter. The team claims that its existence in the early universe could explain why there is more matter than antimatter in the universe – and that dark matter is in fact hidden antimatter.

Dark matter is a mysterious substance that appears to make up about 80% of the material universe. Although its existence can be inferred from its gravitational pull on normal matter, physicists have yet to detect it directly and therefore don't know what it is made of. Antimatter, on the other hand, is easy to create and study in the lab. However, the Standard Model of particle physics cannot explain why antimatter is so rare in a universe that is dominated by matter – a mystery called baryon asymmetry.

Sounds a bit dubious, if dark matter were anti matter we would

1) be able to see it

2) it would collide and annihilate with regular matter.

[Ronnie67]

The baryon asymmetry problem in physics refers to the apparent fact that there is an imbalance in baryonic matter and antibaryonic matter in the universe. Neither the standard model of particle physics, nor the theory of general relativity provide an obvious explanation for why this should be so; and it is a natural assumption that the universe be neutral with all conserved charges.^[1] The Big Bang should have produced equal amounts of matter and antimatter, as such, there should have been total cancellation of both. In other words, protons should have cancelled with antiprotons,electrons with antielectrons (positrons), neutrons with antineutrons, and so on for all elementary particles. This would have resulted in a sea of photons in the universe with no matter. Since this is evidently not the case, after the Big Bang, some physical laws must have acted differently formatter and antimatter.

There are competing hypotheses to explain the matter-antimatter imbalance that resulted in baryogenesis, but there is as yet no one consensus theory to explain the phenomenon. check out Wikipedia, this is where this info came from

[Ronnie67]

The baryon asymmetry problem in physics refers to the apparent fact that there is an imbalance in baryonic matter and antibaryonic matter in the universe. Neither the standard model of particle physics, nor the theory of general relativity provide an obvious explanation for why this should be so; and it is a natural assumption that the universe be neutral with all conserved charges. The Big Bang should have produced equal amounts of matter and antimatter, as such, there should have been total cancellation of both. In other words, protons should have cancelled with antiprotons,electrons with antielectrons (positrons), neutrons with antineutrons, and so on for all elementary particles. This would have resulted in a sea of photons in the universe with no matter. Since this is evidently not the case, after the Big Bang, some physical laws must have acted differently formatter and antimatter.

There are competing hypotheses to explain the matter-antimatter imbalance that resulted in baryogenesis, but there is as yet no one consensus theory to explain the phenomenon.

[cgarry]

That choice of colours makes the text pretty much unreadable to me.

[Ronnie67]

Sorry have not got use to the key links correctly. will try better in future, I think I have the text sorted

[cgarry]

Sorry have not got use to the key links correctly. will try better in future, I think I have the text sorted

Many thanks for that. I appreciate anything that makes it easier for my brain to follow threads like these!

Cheers,

Chris