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Quark Matter questions

  1. Jun 30, 2009 #1
    First post, guys :) Hello all. My only degree is in Earth Sciences, and my physics and astronomy knowledge base is mostly from the pages of Scientific American...and since I'm like a first grader when math time comes...I haven't been able to expand that base by understanding the various expressions and formulas myself.

    ...that said, these questions are aimed at writing a science-fiction story, so please be light on the proof and heavy on the explaining part ;)

    And I hope I'm in the right sub-forum!

    Q1: Could you structure the semi-free quarks of the quark-gluon plasma into, for lack of a better word, a solid material (i.e. like a crystalline material)? Here I'm thinking there could be a parallel with how I imagine neutrons stack inside a neutron star. Is there a structure to neutron stacking? Would the quark-gluon plasma be limited to being just that, a plasma-like state? Do materials like neutron matter (is it still called neutronium?) have tensile strengths? Were they - incredibly - shaped into useful forms, like butresses, could they support weight? Resist torsion and pull?

    Q2: If the inside of a particularly massive neutron star was dense quark matter, would the only thing preventing the total conversion of the star's mass into quark matter be the fact the pressure on the star material dimishes with the distance from its center? (This is probably quite dumb as questions go. I imagine the answer is a resounding yes.)
  2. jcsd
  3. Jun 30, 2009 #2
    Ah, that most wonderful of scientific wonderments: what happens to matter as you squeeze it, *really, really hard*. Frank Wilczek has a review paper out on high density QCD which justifies itself pretty much as just wanting to know the answer to this child-like question. Alas, that one is pretty technical, so perhaps not quite right to simply point at.

    My background is primarily condensed matter, so what I say below about HEP related stuff might just be wrong because I don't know some relevant phenomena. With that in mind:

    Quark-gluon plasma is actually a (relatively) low-density, high temperature form of matter. At sufficiently high density, you actually get a sort of superconductivity, where quarks want to pair up to form a paired background, and then individual quarks move largely freely --- this is called colour superconductivity. The material might even be superconducting in the normal sense too. However, I'm not sure it would have any lattice structure. The key question is if localisation saves energy overall; the effects of interactions are in competition with Heisenberg (localisation == small uncertainty in position == large momenta == large kinetic energy). Atoms, being big, tends to localise when you squeeze; electrons, being small, tend to localise when you have low density (Wigner crystal). I'm not sure which side of the fence the free quarks will lie (which are not really free, but maybe can be regarded as such after some renormalisation due to the pair background).

    Assuming for the moment that upon further pressure/density they will crystallise, then you would have a lattice of quarks sitting in a sea of pairs. However, general relativity still has a change to rear its ugly head. The Schwarzchild radius goes linearly with mass, but to reach the required density the size of object would only go as mass^(1/3). I don't know the numbers, but it could be that any reasonably sized chunk would end up being smaller than its Schwarzchild radius, which would be unhelpful in engineering applications.

    Finally, all this supposes the ability to apply great pressure. Truly vast pressure. Neutrons stars manage because at the centre of a star, you've got a few kilometers of the densest matter known sitting on top of you. I'm not sure there are any other methods --- anything quark-based you use to apply said pressure would, by Newton's 3rd law, feel just as great a pressure, and end up degenerating into the same material. Boson based ones (such as gravity) might be able to get around this --- maybe some form of photon pressure? (Again, the mind boggles at the energies required.)

    Finally, given that it is necessary to apply such great force to just form the matter, it would expect that its tensile strength to be, well, negative? After all, it is all the time actively trying to explode in your face. On the other hand, I'd imagine that the compressive strength would be *considerable*.
  4. Jun 30, 2009 #3
    Thanks for the answer, genneth! Albeit I don't understand much of it.

    Mmm, so QCD matter has the same story as for neutronium then: the only shape you can use it in is that of a gravitionaly-held sphere of the appropriate size, thus mass, since there's no known way of keeping the material compressed otherwise, and if it were not compressed then it's no longer neutronium, reverting to nucleons...oh, and exploding in the process.

    The bit about the Schwarzchild radius...is that in answer to question no. 2?

    "Quark-gluon plasma is actually a (relatively) low-density" : Then I'm confused, for articles point to an hypothetical intermediary state of pressure between neutron star and black hole, a stable one, the quark star. Some fiction even dabbles into that.
  5. Jun 30, 2009 #4
    The Schwarzchild radius thing is actually mostly a musing about whether it would even be possible to create much of this hypothetical matter --- too much in one place and it would just turn into a black hole.

    As far as the low density QG plasma goes: it's more correct to say that it is a state of relatively low chemical potential. The chemical potential changes both as a function of density and temperature --- analogy: it's possible to retain a gas in gas form at high pressure by heating it further. I believe (some astrophysics person should jump in and correct me at this point) that the current understanding of neutron stars is that at the centre the temperature is not high enough to create a QG plasma, given the pressures.

    On the other hand, our understanding of QCD "low energy" phenomena in general is so poor that almost any story could be plausible :-)
  6. Jun 30, 2009 #5
    Basically i'm searching for a phenomena or mechanism that can take control of a neutron star or a small black hole and use it to create energetic gamma ray bursts encoded with information for interstellar communications, and another similar but distant object on the receiving end would be affected by the burst in a predictable fashion and thus the burst's information content could be read. Each burster in the network would double as a receiver.

    I'm thinking if a neutron star was turned into a magnetar, could then futuristic technology controlling electromagnetism be able to control the magnetar so as for it to outpout some of its energy into directed energy bursts, coded?
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