SIMPle Darkish Matter | by Brian Koberlein



2 November 2014

A visualization of dark matter distribution 800 milion years after the Big Bang.
The Marenostrum Numerical Cosmology Challenge
A visualization of darkish matter distribution 800 milion years after the Massive Bang.

Darkish matter stays an enigma of recent cosmology. We’ve got oblique proof of its existence, and even some proof of its traits, however we have now but to detect darkish matter straight. This places us in a form of center floor the place there’s sufficient proof to help darkish matter, however not sufficient to outline it, which is the proper playground for theorists to strive new concepts. This week in Bodily Evaluation Letters, simply such a brand new concept has been introduced.

The preferred mannequin for darkish matter is the WIMP mannequin, or Weakly Interacting Huge Particles. They’re so-named as a result of they might have a a lot bigger mass than protons, however would solely work together by means of the weak nuclear pressure. This implies they wouldn’t work together with gentle a lot (therefore they might be “darkish”), they usually wouldn’t work together with one another so strongly that they will’t create a halo of darkish matter round galaxies. However even weakly interacting particles would sometimes work together with common matter. Given present observations, there must be about 5 occasions extra darkish matter than common matter within the universe, so we must always be capable of detect some interactions straight. Nonetheless regardless of a number of ongoing searches, there’s been no clear proof of it.

So this new paper proposes a brand new mannequin, often known as Strongly Interacting Huge Particles, or SIMPs. On this mannequin, darkish matter particles have a couple of tenth the mass of a proton, however they strongly work together with each common matter and themselves. That may appear contradictory to the character of darkish matter, however as long as they work together in the precise means, it may all work out. Mainly, SIMPs would are likely to clump to imitate extra large WIMPs, and they might work together weakly with gentle, as darkish matter ought to. However due to their smaller mass, they might work together with electrons extra strongly than nuclei. Since darkish matter searches have centered on nuclei interactions, this is able to clarify why we haven’t detected them.

Within the paper the authors present that the SIMP mannequin agrees with present observations of darkish matter, and it exhibits the place future experiments may help or invalidate the thought. However based mostly upon present proof it’s no extra compelling than the favored WIMP fashions. Nonetheless, at this level we’d like new concepts like this one. Darkish matter has been frustratingly tough to pin down.

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