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posted by janrinok on Sunday June 01 2014, @02:59PM   Printer-friendly
from the it-keeps-getting-more-complicated dept.

Zilong Li and Cosimo Bambi with Fudan University in Shanghai have come up with a very novel idea--those black holes that are believed to exist at the center of a lot of galaxies, may instead by wormholes. They've written a paper [abstract], uploaded to the preprint server arXiv, describing their idea and how what they've imagined could be proved right (or wrong) by a new instrument soon to be added to an observatory in Chile.

From the article:

Back in 1974, space scientists discovered Sagittarius A* (SgrA*) - bright source of radio waves emanating from what appeared to be near the center of the Milky Way galaxy. Subsequent study of the object led scientists to believe that it was (and is) a black hole - the behavior of stars nearby, for example, suggested it was something massive and extremely dense.

What we're able to see when we look at SgrA* are plasma gasses near the event horizon, not the object itself as light cannot escape. That should be true for wormholes too, of course, which have also been theorized to exist by the Theory of General Relativity. Einstein even noted the possibility of their existence. Unfortunately, no one has ever come close to proving the existence of wormholes, which are believed to be channels between different parts of the universe, or even between two universes in multi-universe theories. In their paper, Li and Bambi suggest that there is compelling evidence suggesting that many of the objects we believe to be black holes at the center of galaxies, may in fact be wormholes.

Plasma gases orbiting a black hole versus a wormhole should look different to us, the pair suggest, because wormholes should be a lot smaller. Plus, the presence of wormholes would help explain how it is that even new galaxies have what are now believed to be black holes - such large black holes would presumably take a long time to become so large, so how can they exist in a new galaxy? They can't Li and Bambi conclude, instead those objects are actually wormholes, which theory suggests could spring up in an instant, and would have, following the Big Bang.

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  • (Score: 4, Interesting) by maxwell demon on Sunday June 01 2014, @06:03PM

    by maxwell demon (1608) on Sunday June 01 2014, @06:03PM (#49948) Journal

    A stable wormhole needs negative gravitation to prevent it from collapsing, and negative mass allows you to do all sorts of silly causality-breaking things.

    Given that wormholes by themselves allow you to do all sorts of silly causality breaking things, the fact that you need something else allowing such things is not that bad. Indeed, one could even consider it consistent: To enable something you can use to break causality (wormholes), you need something you can use to break causality (a material with negative energy density).

    BTW, doesn't dark energy give negative gravitation (as it accelerates the expansion, I'd say it does)? Has anyone ever calculated the effect of dark energy on potential wormholes?

    The Tao of math: The numbers you can count are not the real numbers.
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  • (Score: 2, Interesting) by Anonymous Coward on Sunday June 01 2014, @06:28PM

    by Anonymous Coward on Sunday June 01 2014, @06:28PM (#49959)

    Yes. The statement that you need negative mass is not, strictly speaking, accurate. You need a negative gravitational charge, which is mass + 3 * pressure * c^2. So to get something that has a negative gravitational effect, you have to violate the "weak energy condition", which is rho + 3*p*c^2 >= 0. Violating this gives you p -rho, and once you start violating *this* then you end up riddled with problems of causality the likes of which make wormholes' own violations pale into insignificance. A dark energy like this is known as "phantom" and would lead to a "big rip", at which point you're more or less concerned about the rate at which the universe is accelerating its expansion and not so concerned about throwing yourself into a black hole in the hopes that it contains a wormhole.

    • (Score: 3, Interesting) by maxwell demon on Sunday June 01 2014, @06:55PM

      by maxwell demon (1608) on Sunday June 01 2014, @06:55PM (#49966) Journal

      But I think that assumes a dark energy density which is constant throughout the universe (cosmological-constant like). But given that we have no clue what dark energy actually is we can't be sure about that (sure, in the universe at large it seems to be evenly distributed, but then, the universe at large is itself quite homogeneous; we don't know what happens with it under extreme conditions, for example in wormholes).

      BTW, how does the Higgs field react to wormhole curvature? I seem to remember that it is or was considered as a candidate for early inflation, so it obviously has the potential to generate negative gravitation under the right conditions.

      The Tao of math: The numbers you can count are not the real numbers.
      • (Score: 2, Interesting) by Anonymous Coward on Sunday June 01 2014, @07:27PM

        by Anonymous Coward on Sunday June 01 2014, @07:27PM (#49971)

        Slow-roll does, certainly, but that Laplacian encodes the spatial gradients -- it's g_{\mu\nu}\nabla^\mu\nabla^\nu, or (1/\sqrt{-g})*(d/dx^\mu)(\sqrt{-g}(d/dx^\nu)). Though certainly I might have got it wrong the gradients are there. The actual form I wrote it in though, yes, that's written in a coordinate system that wouldn't make much sense in the vicinity of a black hole, though you could always swap to a set of coordinates where you could write it like that locally.

        We could certainly model what happens in extreme conditions, such as in some kind of hypercircular strut inside a wormhole. The gradients there will definitely muck it up, you're right, but that doesn't necessarily mean it can't be configured such that you still get a repulsive effect. Of course, it *might*. I'm not aware of anyone who's actually done the calculation.

        Likewise I have no idea how the Higgs acts near the singularity of a hole (which is what the inside of a wormhole would look like -- basically two holes connect and instead of a singularity you have a kind of hypertube which is the Einstein-Rosen bridge, but without something with negative rho+3p you're going to find the bridge closing in front of you, a bit like a gruesome version of Xeno's paradox.) That's a really good question. I suspect that you won't be able to get it moving slowly enough in its own potential, and since it interacts by definition with everything in sight it's probably quite agitated inside a hole. But frankly a realistic calculation would be so tricky, accounting for the backreaction of the Higgs itself on the hole for instance, that it's probably not been done - it would be interesting to see. In its extreme it would probably look like a Schwarzschild-de Sitter which is a black hole in a spacetime with a non-zero cosmological constant.