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Strange Quarks, Quark Stars, & Black Holes

  1. Aug 21, 2006 #1
    I have been wondering something. Assuming strange quark stars exist (and I know that this is still too early to call), is it possible that a black hole might just be an overgrown quark star that has gone over the required mass (say from feeding on a nearby star or a collision)?

    Is there any evidence that a black hole really has no surface, as I have read people say, or is it just assumed because there is no way to detect one?

    Finally, is there any evidence for a form of matter even more dense than a quark (and therefore something that black holes might be made of)?

    Thanks in advance - I know these might seem to be silly questions, but its something I have been wondering about.
  2. jcsd
  3. Aug 21, 2006 #2
    I think that it's not just a question of whether or not there's evidence for their existence: as far as I'm aware, we still don't have cast-iron theoretical models which suggest that such things are possible.

    Black holes do have surfaces, it's just that the "surface" of a black hole may not be what you think it might be. For example, the simplest type of black hole solution to Einstein's equations is known as the Schwarzschild solution. This has a "surface" known as an event horizon. In essence, the event horizon acts as a sort of one-way membrane: anything that passes beyond the event horizon can never escape from the black hole; indeed, anything that goes beyond the event horizon must eventually collide with the singularity at the centre of the black hole itself.

    (As an aside, there exist other examples of black holes, such as something called an extremal Reissner-Nordstrom black hole, which do not have event horizons. However, you can prove quite easily that these types of black holes occur only if extremely special mathematical relations hold and, therefore, almost certainly do not occur in nature.)

    I suppose the real moral here is that the surface of a black hole is not something you can actually touch, but is instead a region that divides the universe in two.

    Well, the first thing to realise is that single quarks never seem to appear in nature: they always occur in tightly bound groups (this is a consequence of a prediction from lattice gauge theory known as quark confinement). Given that neutrons are a particularly stable form of quark configuration, it's extremely unlikely that what you suggest could ever occur.
    Last edited: Aug 21, 2006
  4. Sep 1, 2006 #3
    On the topic of quarks, has anyone else noticed that quarks express a similar mass defect property to that in the standard model of an atom? I'm wondering if anyone who knows how to calculate color charge interactions can tell me more about this.
  5. Sep 2, 2006 #4


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    Any particular property, or just the effect itself?
    No, not a silly question at all. I've been thinking (dangerous for me) something similar for quite some time. This isn't a "Labguy Theory" but a few comments and questions that the particle physics boys can help with.

    White Dwarf and Neutron stars were postulated (Chandra, Oppemheimer and even back to Eddington) a long time ago, and scoffed at up until ~1966(?), for neutron stars anyway, until the Crab Pulsar was confirmed after the 30/second pulses were analyzed. Now, everyone is familiar with electron and neutron degeneracy pressure.

    Recently, "Quark Stars" have had a lot of attention and there is a bunch of math and theory floating about. But, all papers I can find mention only Strange quarks as probable candidates. Question: Can someone explain why the other 5 are not considered? Especially the Top quark with the highest mass(Gev)?..:confused:

    An "Event Horizon" radius can be calculated for any object with any mass >0, correct? So far, only black holes seem to have the property where the EH is "outside" of any concentration of mass, whether there is a singularity or some hidden mass concentration with a "surface" as you seem to be considering. Even neutron stars have a "surface" (Fe and/or Ni). Who is to say that there isn't or can't be an as-yet undiscovered Quark Degeneracy Pressure that allows a BH to have a surface, but still within the REH?

    For all posters here, there is a nice 2006 update on quark masses at this site and the older, generic table here. As far as a more massive particles/free quarks, the second site has an interesting note that:
    Also, neither mentions a "required" connection to/with any PHiggs.

    Can someone tell me the basis of the thinking that determines mass (or binding energy) where or why the Higgs particle (or field) needs to be considered??? This question is only in regard to quarks, not the whole Higgs theory.

    PS: The link mentions the search for any "free quark". All efforts have come up empty which doesn't surprise me at all. It seems we have to stick with two's and three's for quarks. Any help on anything above?
    Last edited: Sep 2, 2006
  6. Jan 31, 2010 #5
    Yes, it is logical that black holes consist of quarks, other "exotic" non-nuclear plasma, and energy. It is baloney that black holes are a singularity, infinitely small, infinite temperature. Rules of physics still work in a black hole: there is equilibrium and pressure balance. Temperatures would be very high and would start at 200 MeV minimum (for nuclear disintegration and quark production) and go well into the TeV region. Exotic particles would be generated until there is pressure balance. Note that most effective mass might be in the form of photon energy, although these would have a very short mean free path before being absorbed and re-emitted. So most of the mass in our universe, if its in the form of black holes, could be in the form of energy. Note that likely any particle in the black hole, no matter how small, would have almost the same energy as the largest quark, similar to tokamak plasmas where the electron and proton energy is about the same.

    Perhaps a black hole could become unstable and explode, but it is more likely that a black hole explosion would occur by instability when 2 black holes of approximate similar mass merge. Evidence for this are in a few galaxies where some enormous explosion fills the whole galaxy. These explosions are centered in the galaxy. And what's in the center of a galaxy?

    So a black hole, inside the event horizon, has temperature, pressure, size, shape, probably a strong magnetic field, and effective mass summation, all of which can be described by physics. It is poor logic (Hawkins?) to state a black hole has infinite temperature and no size. Berniepie@aol.com
  7. Jan 31, 2010 #6


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    A black hole actually has two 'surfaces' an event horizon and a cauchy horizon.
  8. Feb 1, 2010 #7
    This is wrong.....

    Doesn't work. You can show via pretty straightforward calculations that if you pile enough mass in one place, that no stable equilibrium is possible without violating special relativity.

    That's the problem, the more particles you generate, the more degrees of freedom there are, and the less pressure you get.

    Not unless there is something fundamentally wrong with special relativity. *Very* roughly speaking as you pile on more and more mass onto an object, the atoms in that object vibrate faster and faster. Once things are vibrating near the speed of light, any extra mass that you put on doesn't change the speed of the vibrations. What this means is that the material doesn't push back, and so you get no extra pressure when you add more stuff.
  9. Feb 1, 2010 #8
    Once you pile on enough mass into a small enough space, then everything will undergo gravitational collapse.

    There is. If you look at neutron star candidates, they tend to be quite loud. You see bursts of energy, beams of particles coming out (i.e. pulsars). If you look at black hole candidates, you don't see bursts and beams. The explanation that people have come up with is that neutron stars have surfaces so you get these bursts of energy when enough stuff falls on the surface to have a nuclear explosion, and you have beams because the magnetic field that is attached to the surface creates a rotating beam.

    In the case of a black hole, you don't have a surface. Stuff just falls in, and so things are "quieter."

    There are reasons to think that there are no particles more fundamental than quarks, but even if there were, it still doesn't prevent black holes. What Chadrasekar figured out around 1930, is that if you take *ANY* particle, you'll find that there is some limiting mass beyond which it becomes unstable and then collapses. The thing about black holes is that beyond a critical mass, stable configurations of matter cannot exist.
  10. Feb 1, 2010 #9
    The reason that people didn't think seriously about black holes until 1968 was that Chandrasekar's equations created a result that people thought was silly. The thing that happens once you calculate stable configurations of matter is that if you put enough mass in one place, there aren't any stable configurations. Until 1968, the idea was that *something* would stop the collapse, and it wasn't until we found a neutron star, that people thought about the possibility that Chandrasekar's equations would have to be taken literally and something would stop the collapse.

    E = mc^2. If you plug in the energies for neutron stars centers, you find out that there is enough energy to have strange quarks pop out and turn up/down quarks into strange quarks. You use the same sorts of equations to figure out how many top/bottom/strange quarks there are, and the answer is not many.

    It's also possible that at very high densities and pressures that strange quarks have less energy than up/down quarks and so when you compress things enough, things will turn into strange quarks. The other types of quarks are so heavy that they'll never be the lowest energy.

    Actually if the EH is inside the object, then the assumptions you are using to work through the equations stop working. Also it is likely that there is some sort of quark degeneracy pressure, but the effect of that pressure would be to just bump up the critical mass to collapse by a small amount. The way the equations work out, eventually gravity always wins.

    The easiest way of getting an equation in which things have masses is to assume that they are interacting with some sort of field, and in quantum mechanics, each field has a particle. There are other ways of making the equation work, but the Higgs mechanism is the simplest (not to say that it's correct).

    Also as far as why the quark masses are what they are, no one has any real clue.
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