Dark matter might connect galaxies through wormholes

Tl;dr: A new paper shows that one of the most popular types of dark matter – the axion – could make wormholes possible if strong electromagnetic fields, like those found around supermassive black holes, are present. Unclear remains how such wormholes would be formed and whether they would be stable.

Wormhole dress.
Source: Shenova.

Wouldn’t you sometimes like to vanish into a hole and crawl out in another galaxy? It might not be as impossible as it seems. General relativity has long been known to allow for “wormholes” that are short connections between seemingly very distant places. Unfortunately, these wormholes are unstable and cannot be traversed unless filled by “exotic matter,” which must have negative energy density to keep the hole from closing. And no matter that we have ever seen has this property.

The universe, however, contains a lot of matter that we have never seen, which might give you hope. We observe this “dark matter” only through its gravitational pull, but this is enough to tell that it behaves pretty much like regular matter. Dark matter too is thus not exotic enough to help with stabilizing wormholes. Or so we thought.

In a recent paper, Konstantinos Dimopoulos from the “Consortium for Fundamental Physics” at Lancaster University points out that dark matter might be able to mimic the behavior of exotic matter when caught in strong electromagnetic fields:

Active galaxies may harbour wormholes if dark matter is axionic
By Konstantinos Dimopoulos
arXiv:1603.04671 [astro-ph.HE]

Axions are one of the most popular candidates for dark matter. The particles themselves are very light, but they form a condensate in the early universe that should still be around today, giving rise to the observed dark matter distribution. Like all other dark matter candidates, axions have been searched for but so far not been detected.

In his paper, Dimopoulos points out that, due to their peculiar coupling to electromagnetic fields, axions can acquire an apparent mass which makes a negative contribution to their energy. This effect isn’t so unusual – it is similar to the way that fermions obtain masses by coupling to the Higgs or that scalar fields can obtain effective masses by coupling to electromagnetic fields. In other words, it’s not totally unheard of.

Dimopoulos then estimates how strong an electromagnetic field is necessary to turn axions into exotic matter and finds that around supermassive black holes the conditions would just be right. Hence, he concludes, axionic dark matter might keep wormholes open and traversable.

In his present work, Dimopoulos has however not done a fully relativistic computation. He considers the axions in the background of the black hole, but not the coupled solution of axions plus black hole. The analysis so far also does not check whether the wormhole would indeed be stable, or if it would instead blow off the matter that is supposed to stabilize it. And finally, it leaves open the question how the wormhole would form. It is one thing to discuss configurations that are mathematically possible, but it’s another thing entirely to demonstrate that they can actually come into being in our universe.

So it’s an interesting idea, but it will take a little more to convince me that this is possible.

And in case you warmed up to the idea of getting out of this galaxy, let me remind you that the closest supermassive black hole is still 26,000 light years away.

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Note added: As mentioned by a commenter (see below) the argument in the paper might be incorrect. I asked the author for comment, but no reply so far.
Another note: The author says he has revised and replaced the paper, and that the conclusions are not affected.