|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
interesting dark-matter candidate
I'm now at a cosmology conference:
https://indico.cern.ch/event/736594/overview One reason to go to a conference is to hear about interesting things one might have missed. For me, probably the most interesting talk was the penultimate one, an update on these publications concerning a novel dark-matter candidate: https://arxiv.org/abs/1202.0560 https://arxiv.org/abs/1311.1627 http://iopscience.iop.org/article/10...6/496/1/012023 https://arxiv.org/abs/1801.04206 There are many connections between particle physics and astronomy, but this is closer than most, is a really novel idea, makes clear predictions, explains very many (otherwise not closely related) things with a simple idea, and has already had some predictions confirmed. While I've been to other conferences which covered a wide range of topics, at this one there were intentionally no sessions on specific topics, but, say, a talk on observational astronomy could be followed by one on theoretical particle physics. I can't write a summary here, of course, but one general theme is that while large-scale cosmology is more or less solved, it is becoming even more clear that many things about galaxies, particularly dwarf galaxies, are not understood, and it is unclear which of many options is the way forward. One aspect of this is dark matter, and both the lack of direct (or indirect) detections as well as the discovery of a light Higgs seems to be swinging the pendulum away from WIMPs as dark matter to other ideas. Also, it might turn out that more than one of the alternatives to WIMPs is correct. |
#2
|
|||
|
|||
interesting dark-matter candidate
Le 27/10/2018 à 18:50, Phillip Helbig (undress to reply) a écrit :
I'm now at a cosmology conference: https://indico.cern.ch/event/736594/overview One reason to go to a conference is to hear about interesting things one might have missed. For me, probably the most interesting talk was the penultimate one, an update on these publications concerning a novel dark-matter candidate: https://arxiv.org/abs/1202.0560 https://arxiv.org/abs/1311.1627 http://iopscience.iop.org/article/10...6/496/1/012023 https://arxiv.org/abs/1801.04206 Those papers do not show any physical evidence. The common author in all papers is Jarah Evslin, working in Peking. https://arxiv.org/abs/1202.0560 says: We propose a model of dark matter: galaxy-sized 't Hooft-Polyakov magnetic monopoles OK. The only evidence is presented in: https://arxiv.org/abs/1801.04206. This paper shows a simulation for "Spiked monopoles" done in some computer. According to the authors: quote Dark matter halos grow by merging. This merging requires them to be attractive, but the simplest manifestation of monopole dark matter is repulsive. end quote !!! quote If the magnetic repulsion is sufficiently weak, then it can be overcome by gravity. However fitting parameters in the simplest model [1] one finds that v â¼ 1014 GeV and so the magnetic repulsion is stronger than gravitational attraction by nearly 10 orders of magnitude. In the spiked monopole model, the gravitational repulsion is reduced. The crudeness of our numerical simulations and initial conditions makes it difficult to quantify the repulsion, however it clearly is not reduced by the required 10 orders of magnitude. end quote ------------------------------------------------------------------ http://iopscience.iop.org/article/10...6/496/1/012023 https://arxiv.org/abs/1311.1627 Same author, slightly different presentation, similar arguments. Both papers are almost the same. quote Unfortunately these monopoles repel and so the charge Q 1 halos are unstable. This may rule out our model. Then again, protons repel but visible matter is mostly made of protons, as the repulsion at small distances is canceled by neutrons and at large distances is screened by electrons. The monopoles only repel at long distances. So what are the analogs of the electrons? Electrons carry the opposite charge from protons but cannot annihilate with protons as they carry a flavor quantum number and the lightest state for a decay product, the neutron, is too massive for the decay to be kinematically allowed. Similarly such a flavor quantum number for the monopoles is an automatic consequence of our fermionic couplings. The masses of the various flavors of monopoles can be adjusted by choosing the Yukawa couplings. We propose to include light antimonopoles of a different flavor which screen the long distance repulsion of our monopoles. If such a screening cannot be made to work, our proposal will be excluded. end quote Let's see then... They have to first find out the "electrons" that would screen out the repulsion between those galaxy sized monopoles. All this is interesting, yes, but it is very difficult to gauge if there is any connection with reality at this stage. Mathematics is an infinite forest, and it is very easy to lose your way in the equation undergrowth... Obviously too, I am in NO WAY able to follow precisely those papers, and can only look at the conclusions. jacob |
#3
|
|||
|
|||
interesting dark-matter candidate
In article , jacobnavia
writes: Those papers do not show any physical evidence. Right. If they did, they would be reporting a dark-matter detection, not discussing a candidate. So, to first order, this is another candidate like many others: WIMPs, MACHOs, PBHs, fuzzy dark matter, self-interacting dark matter, superfluid dark matter, etc. The common author in all papers is Jarah Evslin, Right. working in Peking. Not any more, though still in China. While there might be some examples of people from the West working in China because they couldn't get any academic job elsewhere (I have met some), Evslin is definitely not one of those. He is extremely knowledgeable about both astronomy and particle physics. This is also a rare combination (not counting people who work on BBN, inflation, etc, which is mainly particle physics applied to an astrophysical problem). quote Dark matter halos grow by merging. This merging requires them to be attractive, but the simplest manifestation of monopole dark matter is repulsive. end quote !!! Don't let this throw you off. Unfortunately these monopoles repel and so the charge Q 1 halos are unstable. This may rule out our model. Then again, protons repel but visible matter is mostly made of protons, as the repulsion at small distances is canceled by neutrons and at large distances is screened by electrons. The monopoles only repel at long distances. So what are the analogs of the electrons? Electrons carry the opposite charge from protons but cannot annihilate with protons as they carry a flavor quantum number and the lightest state for a decay product, the neutron, is too massive for the decay to be kinematically allowed. Similarly such= a flavor quantum number for the monopoles is an automatic consequence of= our fermionic couplings. The masses of the various flavors of monopoles can be adjusted by choosing the Yukawa couplings. We propose to include light antimonopoles of a different flavor which screen the long distance= repulsion of our monopoles. If such a screening cannot be made to work, our proposal will be excluded. end quote Let's see then... They have to first find out the "electrons" that would screen out the repulsion between those galaxy sized monopoles. All this is interesting, yes, but it is very difficult to gauge if there= is any connection with reality at this stage. Mathematics is an infinite= forest, and it is very easy to lose your way in the equation undergrowth.= ... Obviously too, I am in NO WAY able to follow precisely those papers, and= can only look at the conclusions. The thing which makes this idea interesting is that it explains, at one fell swoop, many of the most pressing problems at the border between cosmology and astrophysics, in particular the observed properties of low-mass galaxies, satellite galaxies, the matter distribution within galaxies, and so on. Yes, the theory itself is one of many, but this it has in common with other candidates. What makes it interesting is that it explains much more and makes robust testable predictions. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Another candidate for Dark Matter in spiral galaxies, weighs in... | dlzc | Astronomy Misc | 3 | March 9th 12 08:42 PM |
Complete dark matter theory opens door to weight/energy potential(Dark matter is considered to be the top mystery in science today, solved,really.) And more finding on dark matter ebergy science from the 1930's. | [email protected] | Astronomy Misc | 0 | September 14th 08 03:03 AM |
Dark matter means ebergy (ebergy known since the 1930's to makeenergy from 'dark matter'). Dark matter is solved for the first time (100pages) | gb[_3_] | Astronomy Misc | 0 | August 5th 08 05:24 PM |
An interesting article in the NYtimes: Dark matter, Dark Energy, will we ever know? | Jan Panteltje | Astronomy Misc | 5 | March 13th 07 09:35 AM |