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Will wormholes go away (be found to be a quirk of the theory) or . . ?

  1. Dec 11, 2007 #1

    wolram

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    Will wormholes go away (be found to be a quirk of the theory) or are they to embeded in the theory?
     
  2. jcsd
  3. Dec 12, 2007 #2

    Chris Hillman

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    What theory would that be? Or this not a serious inquiry?
     
  4. Dec 12, 2007 #3

    wolram

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    Sorry i should have shown some examples of what i meant.

    http://arxiv.org/abs/gr-qc/0511003

    The generalized Chaplygin gas (GCG) is a candidate for the unification of dark energy and dark matter, and is parametrized by an exotic equation of state given by $p_{ch}=-A/\rho_{ch}^{\alpha}$, where $A$ is a positive constant and $0<\alpha \leq 1$. In this paper, exact solutions of spherically symmetric traversable wormholes supported by the GCG are found, possibly arising from a density fluctuation in the GCG cosmological background. To be a solution of a wormhole, the GCG equation of state imposes the following generic restriction $A<(8\pi r_0^2)^{-(1+\alpha)}$, where $r_0$ is the wormhole throat radius, consequently violating the null energy condition. The spatial distribution of the exotic GCG is restricted to the throat neighborhood, and the physical properties and characteristics of these Chaplygin wormholes are further analyzed. Four specific solutions are explored in some detail, namely, that of a constant redshift function, a specific choice for the form function, a constant energy density, and finally, isotropic pressure Chaplygin wormhole geometries.

    http://usparc.ihep.su/spires/find/hep/www?rawcmd=dk+"WORMHOLE,+STATIC"

    There are so many, i just do not understand why they are so important, why every one seems to want them.
     
    Last edited: Dec 12, 2007
  5. Dec 12, 2007 #4

    Chris Hillman

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    Trying to be all things to all contenders?

    Wolram, I really hope we can avoid starting a flame war here since you are asking us to comment on matters about which some people seem to feel very strongly. I'll try to give what I think is an even handed assessment which is equally unfair to all points of view currently held by a few dozen or more researchers, and I hope this will satisfy you.

    If you don't know the lingo it's easy to be fooled into thinking that something known as "Chaplygin gas" is known to actually exist in the sense that a gas called helium is known to exist (and even has technological applications in the advertising industry, e.g. the Goodyear blimp), but that is not at all the case. The weasel word "exotic" in "exotic equation of state" is your clue that someone basically tried to invent an equation of state (an equation relating density and pressure) which would lead to some kind of heuristic model which might solve some observations currently lacking well established theoretical explanations, if only such stuff actually existed. Fair enough, since when you don't have a clue you start by playing around, but the point is that models of so-called "traversable wormholes" held open by so-called "exotic matter" are at present sheer fantasy. The difference between scientific fanasies and talking dragons is that sometimes scientific fantasies eventually turn out to resemble actual phenomena in Nature. More often-- much more often--- they do not.

    As to "why everyone seems to want wormholes": well, fundamental theoretical physics has been kinda stuck for many decades; there are well understood mysteries but little progress toward devising experiments which can decide between competing theories or quasi-theories. In consquence of lack of "reality checks", theoretical physicists have gone rather wild in the past few decades and have produced many highly imaginative speculations, which they can get away with (to some extent) because there is as yet no relevant experimental evidence ruling out any manner of wild speculation. Again, in the absence of experimental evidence, there's little for theorists to do in the area of fundamental physics other than speculate; some feel that too many theorists have chosen this route rather than a "sensible" alternative, making theories of challenging but nonfundamental physics.

    To be fair, were someone someday to establish by experiment or observation irrefutable evidence of traversable wormholes or even just some kind of exotic matter, that would be big stuff; some even think that if only exotic matter existed, they could figure out how to do nifty things like physically travel to distant galaxies. That would be fun, no doubt about it, but the trouble is that, modulo pedantics about stuff like Casimir effect, at present there is no universally accepted theoretical rationale for why exotic matter "must exist" or universally accepted evidence that such stuff does exist. That said, much of the current interest in exotic matter is driven by observations which may be indirect evidence for the existence of something vaguely resembling some of the hypothetical stuff which has been discussed under the umbrella term "exotic matter".

    Now that I've offended everyone :wink: I hope we can all let this rest! (Or move this thread to GD.)
     
    Last edited: Dec 12, 2007
  6. Dec 13, 2007 #5

    marcus

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    Interesting question. First off I'll give you my immediate guess, then try to answer carefully. I think that traversables could go away (if people find out more and decide they are not likely to exist.)
    but I think that general, not necessarily static macroscopic things you could jump thru but I really mean general, are fairly deep embedded, and likely to remain a longterm feature in how people conceptualize spacetime at very small scale.

    You are using SPIRES in a kind of focused way:
    This only gets some 15 wormhole papers which is not a lot. But as i guess you found out, if you use a wider search you get over 1000 wormhole papers----around 30 - 50 a year (I checked as far back as 1993.)

    Just looking at the last 5 years (date > 2002) I find 192 wormhole papers
    http://usparc.ihep.su/spires/find/h...+date+>+2002&FORMAT=www&SEQUENCE=citecount(d)

    which when I rank them by citations suggest that the most higly cited are about TRAVERSABLE wormholes. That is a kind that I don't know much about and have always considered sort of speculative. I'm a bit puzzled by this. I expected the bulk of the research to be about general (unstable, microscopic, untraversable) wormholes.

    For instance Sidney Coleman (I think of him as on par with Nobel laureates, even though he didnt happen to win the prize himself) has a 1993 wormhole paper. It is about wormholes in the context of chaotic planckscale fluctuations in geometry (foam). Not the static macroscopic kind people imagine. I expected the papers to be more like that.

    But apparently I was wrong. At least among the most recent (since 2002) and the highly cited, they seem to be about traversable wormholes supported by exotic (never observed) matter.

    So for the moment, wolram, I am stumped. I was busy today and didn't get a chance to look at this until now. I will have another look at it in the morning. (I still suspect that the answer to your question will the more speculative traversable sort of wormholes fade out of the picture could well be YES, but I havent got evidence yet to back it up.)
     
    Last edited: Dec 13, 2007
  7. Dec 13, 2007 #6

    wolram

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    Thank you Chris, Marcus.

    I was baffled by the quantity of papers on macro WHs, i thought there must be some
    neon sign pointing to them, i am sure the case for micro WHs in the quantum fuzziness
    is far more possible.
     
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