I'm interested in theories of dark matter where dark matter is an equivalent copy (or copies) of ordinary matter. Each equivalent sector is hidden from the others would see the others as 'dark' and their sector own as ordinary. So who is dark and who is ordinary is a relative situation of what sector you happen to be observing from.

I'd like to look at the question of under what conditions (size of the dark matter star, and it's velocity and the density of the nebula) would a star made of dark matter that passed through a nebula made of ordinary matter be able to trigger a collapse that nebula and form a star.

I'm imagining a situation like how the particle passing through a cloud chamber would cause condensation along the path of that particle.

This seems like a fairly obvious place to look for signs of dark matter, but I haven't been able to find a reference of anyone looking into this.

Is anyone aware of any leads, or if this idea has been developed already?

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    $\begingroup$ But the evidence is that dark matter is not in the form of compact objects like stars. e g. The MACHO search. $\endgroup$ – Rob Jeffries Jul 15 at 20:02
  • $\begingroup$ I know, but it seems like the hunt for the identity of dark matter is coming up with so few solid candidates that it's not too absurd to explore the various models. The history of physics has enough twists and turns that it probably pays to not err of the side of being too narrow. $\endgroup$ – David Elm Jul 15 at 20:09
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    $\begingroup$ There is the Lisa Randall model, in which the dark sector has two components, a weakly interacting particle which produces the usual halo, and a strongly self-interacting component which produces a "dark disk" of compact objects (whose size depends on the details of the new interactions). $\endgroup$ – Mitchell Porter Jul 15 at 22:42

The closest thing I know is Bekki's notion that a "dark matter clump" may have collided with a gas cloud of ordinary (baryonic) matter, creating an expanding ring shockwave, throughout which stars are forming. The ring is real and about 30 million years old and called the Gould Belt.

Apart from that, presumably you could get somewhere by finding a model of how an ordinary star passing through a nebula might stimulate star formation, and then subtracting from the model, any electromagnetic pressure from the star, and any nongravitational influence of material outflow from the star. (Though depending on the details of dark matter physics, there could still be some effect of collisions between baryonic nuclei and the dark solar wind.)

  • $\begingroup$ Thanks for the lead on the Gould Belt. I think it might have some important input into this model I'm working on. Even if it doesn't it's very interesting. $\endgroup$ – David Elm Jul 18 at 18:40

You seem to be confusing dark matter with antimatter, which is excusable seeing that when the first particles were created just after the Bi Bang, for every matter particle created there should have been an antimatter particle, for every proton an antiproton and for every electron a positron. It has baffled astronomers and physicists for a hundred years as to what happened to all this antimatter. Theories have been proposed, but they are not very satisfactory, to put it mildly. We are still waiting for a satisfactory explanation. Part of the difficulty is that we can never deal with antimatter in bulk to explore its properties: it can only be manufactured in ultra-minute, sub-microscopic quantities. One day perhaps the mystery of the missing antimatter will be solved.

As for dark matter, we don't know what that is either. We know it is there because of its gravitational effect on galaxies, but it can't be in the form of stars, because comparatively few stars are dark. Probably the leading theory at the moment is that dark matter is composed of exotic particles called WIMPS, which rarely interact with anything except through gravity, but I don't find the WIMP theory convincing. My guess is that dark matter will turn out to be ordinary matter, but in a form we can't see. If you happen to be a youngish man, you might live long enough to see both of these mysteries solved.


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