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Math Science

Strings Link the Ultra-Cold With the Super-Hot 236

gabrlknght writes "Superstring theory claims the power to explain the universe, but critics say it can't be tested by experiment. Lately, though, string math has helped explain a couple of surprising experiments creating 'perfect liquids' at cosmic extremes of hot and cold. 'Both systems can be described as something like a shadow world sitting in a higher dimension. Strongly coupled particles are linked by ripples traveling through the extra dimension, says Steinberg, of Brookhaven. String math describing such ripples stems from an idea called the holographic principle, used by string theorists to describe certain kinds of black holes. A black hole's entropy depends on its surface area — as though all the information in its three-dimensional interior is stored on its two-dimensional surface. (The 'holographic' label is an allusion to ordinary holograms, where 3-D images are coated on a 2-D surface, like an emblem on a credit card.) The holographic principle has value because in some cases the math for a complex 3-D system (neglecting time) can be too hard to solve, but the equivalent 4-D math provides simpler equations to describe the same phenomena.'"
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Strings Link the Ultra-Cold With the Super-Hot

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  • by Amazing Quantum Man ( 458715 ) on Tuesday April 14, 2009 @06:53PM (#27579117) Homepage

    XKCD []

  • Re:Hang on (Score:3, Informative)

    by omuls are tasty ( 1321759 ) on Tuesday April 14, 2009 @07:24PM (#27579569)
    I'm just a layman, but from what I gather the extra dimensions are supposed to be circular rather than "linear", like the ones we commonly use. The circumference of these circles is very small (Planck length).
  • Re:Hang on (Score:5, Informative)

    by FooAtWFU ( 699187 ) on Tuesday April 14, 2009 @07:26PM (#27579613) Homepage
    Imagine the surface of a typical PVC pipe. It's long in one direction (perhaps infinitely long, probably not though) but in the other dimension it's actually kind of small - it's sort of "rolled up". Keep going around and you loop.

    Dimensions can have all sorts of zany topologies going out to infinity.

  • by azure8472 ( 930462 ) on Tuesday April 14, 2009 @07:46PM (#27579843)
    "Ultracold" here refers to degenerate Fermi gases, not Bose-Einstein condensates (BEC).

    Here's a layman article:
    A Fermi gas of atoms []
    Deborah Jin
    Physics World, 2002

    And the original publication by the Duke group:
    Observation of a Strongly Interacting Degenerate Fermi Gas of Atoms []
    K. M. O'Hara, S. L. Hemmer, M. E. Gehm, S. R. Granade, J. E. Thomas
    Science Vol 298, p 2179 - 2182 (2002)
  • Re:Hang on (Score:5, Informative)

    by DynaSoar ( 714234 ) on Tuesday April 14, 2009 @08:20PM (#27580277) Journal

    I was under the impression a dimension was like a mathematical axis, i.e. infinite in two directions...?

    There's no such animal outside theory. In the real universe, spacetime is curved, more or less depending upon local conditions, but definitely never geometric line straight. If it appears that way it's because either the curve is too slow, you are similarly curved, or both. At the most extreme, the theoretical 'closed' universe curves back on itself as if you lived on the inside surface of a balloon.

    Taking the lead from this Einsteinian view, string theory says the other dimensions are curved also, but to the extreme -- like to the Planck length or less (the smallest possible "grain" of the universe). The difference is not quality, only in quantity. That balloon you live in? Make it the so small that in size it is to an atom as an atom is to the Earth.

    Once you've bent your head around that, consider that due to the Planck stuff, and things like Hawking's idea that near a singluarity (such as a Planck scale phenomenon) time and space fold into each other, no dimension no matter how straight, is an exact integer at all scales. This is true of the usual 4, and almost certainly of the other hypothesized 7. These other than integer dimensions are said to be "fractional". From fractional dimensions comes the word "fractal". And here you thought fractals were just good for producing CGIs of clouds, mountains, explosions and so forth. They are, but it's because they also produce the appearance of the real things.

  • by fluffy99 ( 870997 ) on Tuesday April 14, 2009 @08:46PM (#27580591)

    The article dorks up the notion of holography by associating it with 3-d holograms. The concept is that you don't need to know whats in the middle if you can draw a border around it and measure the surface of that border with sufficient resolution.

    In "near field measurements" you are too close to the source to treat it as a simple point source, or a point source with directionality to its output. Normally you would have to be in the far field (at least several wavelengths of the frequency you're measuring or several times the physical size of the source) to be able to measure it using point receivers. Being in the near field you can't simply scale your measurement to farther distances using the normal spreading formula involving r^2 or r^3.

    As an example, sticking a mic 4 inches away from a loudspeaker can't tell you what the sound level will be 100 feet away. Amusingly, the typical 1-meter you normally on stated SPL levels is too close for larger woofers.

    Holographic measuring is the concept of putting an array of sensors in the near field surrounding the object and being able to extrapolate far field measurements. There are criteria for the number of required measurement points and spacing based on the distance and frequency you're trying to measure. From those measurements you can determine the far field measurements and make some calculations about whats inside the boundary. One technique is to take all those new measurements, amplitude and phase, and substitute those as individual point sources in calculating the far field sound levels.

  • by jholden215 ( 939343 ) on Tuesday April 14, 2009 @08:48PM (#27580607) Homepage
    It has always irked me how easily people misuse the word 'theory'. Until it is testable, with reproducable results, it will remain 'String Hypothesis'.
  • by domatic ( 1128127 ) on Tuesday April 14, 2009 @09:02PM (#27580727)

    Yes there are tests but the tests won't be definitive. One of the problems with string theories is that there are a multitude of them and they very very mutable. The collider will only rule out (likely) or confirm (doubtful) a subset of the possible string theories. However, the remainder of the string theories will be safe from falsifiable experimentation. What is needed but lacking is way to winnow out candidate string theories that a) describe our/the universe, b) solve current quandaries of physics like why certain physical constants have the values that they do, c) make predictions which are practical to confirm, d) are parsimonious as string theories are notorious for introducing several new constants and constructs for every one they explain.

    Now I may not be a PhD but I am a taxpayer who is happy to see some of his taxes go to funding basic scientific research. And I agree with those who say that the current fashionability of string theories preclude other approaches from being funded and that string theories are getting a free pass on standards of prediction, observation, and experiment that other branches of science are held to.

    Incidentally, a hallmark of all other good theories in physics to date is that all can be represented by fairly simple systems of equations which an Asimov, a Sagan, or for that matter a good HS science teacher can explain to an interested (and research funding...) public. Be they Newtons Law's, Special and General Relativity, or Maxwell's Equations, good theories tend to have a parsimonious tightness to them that practically shout out what experiments one should do next. Now I realize that in the end, that the universe need not conform to such beautiful systems but the fact that to date that it has and string theories most certainly are not give me pause.

    The FA at least holds out some hope for winnowing out more implausible string theories (and no the idea that all string theories describe a possible universe cuts zero ice until someone finds a way to observe/test that) at least and maybe showing the way to an actual viable theory that is more than pretty math.

  • by Chuckstar ( 799005 ) on Tuesday April 14, 2009 @09:18PM (#27580921)

    This article really is not about string theory. The article is really about the math developed as people have explored string theory. It is this math that has been applied in explaining "perfect liquid" experiments.

  • by Anonymous Coward on Tuesday April 14, 2009 @09:53PM (#27581289)

    The holographic principle has nothing to do with holograms. It's the idea that a 11 dimensional string theory is equivalent to a 4-dimensional quantum field theory under certain conditions. The word hologram is only a term to describe the real thing.

    If you're going to accuse string theorists of incompetence, make sure you know what you're talking about first.

  • by tixxit ( 1107127 ) on Tuesday April 14, 2009 @11:27PM (#27581915)
    They are trying to explain a concept to laymen. It is not easy. Put another way, shadows on a floor live in a 3 dimensional (2 space + time) world, but the movements and behaviour of those shadows are actually better described in a 4 dimensional (3 space + time) world. In other worlds, a shadows movements are better described by considering them as projections of 4-d objects, rather than 3-d objects. Think of the shadow of a quarter flipping. In the shadow world, we see an object that is continuously shrinking down to a thin line then expanding again to a circle. It seems weird, and the equations to describe the movement/shape through time would not be trivial. However, when we add an extra dimension, we realize we can actually model the movement/shape as a simple rotation of a rigid body.
  • Incomplete vs wrong (Score:4, Informative)

    by Weedhopper ( 168515 ) on Wednesday April 15, 2009 @01:05AM (#27582503)

    Yes and no. I read the post and the poster displays an incomplete understanding of the what he's talking about. In some ways, he's wrong, but mostly he's incomplete. I suppose my reply was incomplete for no other reason that I was being a jerk and dismissive.

    The first paragraph, nothing inherently wrong there.

    The second paragraph about "we think" things have been experimentally verified is where it starts to go off the rails. Relativity and quantum mechanics have both predicted, verified and repeatable results of both experiments and observations.

    I'm going to use relativity for a moment here because the OP states that he thinks something is "wrong" with relativity or somehow stands weaker footing than quantum mechanics, specifically because he believes that devices have not been built to explore and demonstrate. No.

    Going back to my previous example, relativity predicts that for the velocity and orbit of a GPS satellite, there will be a time dilation amounting to a very small fraction of a second. There MUST be compensation for this discrepancy, otherwise, your GPS unit would be off by about 10kms a DAY. Is this an experiment? No, it's even better. The experimental confirmations took place before. This is an everyday practical application of the Theory of Relativity. We know that in these conditions, what we know holds to be true. There is nothing inherently wrong with either relativity or QM, because in their respective spheres, they work.

    The fundamental concept that Areyoukiddingme is misunderstanding is that scientific endeavors are not predicated on the concept that the ideas of the present, and by association the past, are wrong. Newton's ideas as laid in the Principia are as fundamentally sound today as they were during his time. However, at the extremes of mass and speed, it starts to fray at the edges. Does that mean he was wrong? Negative. His understanding was incomplete , which is a very different thing from wrong. As Newton himself was standing on the shoulders of giants, others would build on his theories, all the way up to Einstein and those who followed him.

    This is a very important nuance - the elimination of errors in our understanding is a side effect of the purpose of science, which is to increase our understanding. This is a constructive, not a destructive intellectual process.

  • by harry666t ( 1062422 ) <harry666t@gma i l . com> on Wednesday April 15, 2009 @04:25AM (#27583433)
    Try "You shouldn't do that" by Hawkwind :)

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