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Stealth dark matter?

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Sounds like science fiction. But from ScienceDaily:

New theory of stealth dark matter may explain universe’s missing mass

A group of national particle physicists known as the Lattice Strong Dynamics Collaboration, led by a Lawrence Livermore National Laboratory team, has combined theoretical and computational physics techniques and used the Laboratory’s massively parallel 2-petaflop Vulcan supercomputer to devise a new model of dark matter. It identifies it as naturally “stealthy” (i.e. like its namesake aircraft, difficult to detect) today, but would have been easy to see via interactions with ordinary matter in the extremely high-temperature plasma conditions that pervaded the early universe.

“These interactions in the early universe are important because ordinary and dark matter abundances today are strikingly similar in size, suggesting this occurred because of a balancing act performed between the two before the universe cooled,” said Pavlos Vranas of LLNL, and one of the authors of the paper, “Direct Detection of Stealth Dark Matter through Electromagnetic Polarizability.” The paper appears in an upcoming edition of the journal Physical Review Letters and is an “Editor’s Choice.”


Rob Sheldon kindly writes to say,

There are several options for explaining the extra gravity:

a) small, exotic subatomic particles that have not yet been discovered

b) small baryonic (ordinary) mass objects bigger than a pea but smaller than the Moon.

c) non-Newtonian gravity (MOND) that at long distances is stronger than expected

No one has attempted to change Newton’s constant, G, with time. For one thing, we can see distant galaxies that are 1/10 the age of our Milky Way, and they exhibit the same dark matter problem as our Milky Way does now–there’s no evidence that G has changed over the age of the universe.

This is not to say that other features, such as the vacuum pressure = cosmological constant (Lambda)*Volume, haven’t changed, but we move the change into the size of the universe and claim that the Lambda is a static number.

I’ve written a proposal and a paper on option (b), but it remains a very unpopular option due to the investment in COBE/WMAP/Planck “precision” cosmology. That is, if (b) is true, most of the previous precision is lost. So (a) is the most popular, followed by a vocal minority of (c).

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So not only is it dark, it's also stealthy? But our best science treats it as if it actually exists in reality. Mung

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