Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Do Black Holes End up as Quark Stars? and quantum gravity

  1. Aug 15, 2015 #1
    this paper

    Do Black Holes End up as Quark Stars ?


    (Submitted on 25 Feb 2007)

    The possibility of the existence of quark stars has been discussed by several authors since 1970. Recently, it has been pointed out that two putative neutron stars, RXJ 1856.5 - 3754 in Corona Australis and 3C58 in Cassiopeia are too small and too dense to be neutron stars; they show evidence of being quark stars. Apart from these two objects, there are several other compact objects which fit neither in the category of neutron stars nor in that of black holes. It has been suggested that they may be quark stars.In this paper it is shown that a black hole cannot collapse to a singularity, instead it may end up as a quark star. In this context it is shown that a gravitationally collapsing black hole acts as an ultrahigh energy particle accelerator, hitherto inconceivable in any terrestrial laboratory, that continually accelerates particles comprising the matter in the black hole. When the energy \textit{E} of the particles in the black hole is ≥102GeV, or equivalently the temperature \textit{T} of the matter in the black holes is ≥1015K, the entire matter in the black hole will be converted into quark-gluon plasma permeated by leptons. Since quarks and leptons are spin 1/2 particles,they are governed by Pauli's exclusion principle. Consequently, one of the two possibilities will occur; either Pauli's exclusion principle would be violated and the black hole would collapse to a singularity, or the collapse of the black hole to a singularity would be inhibited by Pauli's exclusion principle, and the black hole would eventually explode with a mini bang of a sort. After explosion, the remnant core would stabilize as a quark star.
    Comments: 6 pages

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:astro-ph/0702671

    (or arXiv:astro-ph/0702671v1 for this version)

    If this paper's conclusion is correct, and collapsing stars result in quark stars rather than black holes, that gravity cannot overcome fermion quark Pauli's exclusion principle astrophysical black holes are really quark stars. increasing its density simply results in excess energy being radiated away.

    if the paper is correct, how would this affect black hole physics and quantum gravity theories? how would this effect black hole entropy, black hole information paradox, black hole firewalls, hawking radiation, event horizon, reconciling gravity with quantum mechanics, if black holes are actually quark stars as argued in the paper.

    specifically, how would hawking calculation of hawking radiation, black hole entropy, structure of spacetime, holographic principle be modified if

    every astrophysical "black hole" is actually a quark star, general relativity and gravity cannot over come Pauli exclusion principle of fermions, and that quark degenerate matter, quark-gluon plasma represents the upper limit possible for density as argued in paper above. above this density the quark gluon plasma simply radiates away excess energy.

    string theory and lqg
    Last edited: Aug 15, 2015
  2. jcsd
  3. Aug 16, 2015 #2


    User Avatar
    Science Advisor

    If an astronomical object is small enough and massive enough that the escape velocity is greater than the speed of light, it is a black hole. Its physical composition is an open question, so it could be a quark star.
  4. Aug 16, 2015 #3
    i think he is arguing this

    Since quarks and leptons are spin 1/2 particles,they are governed by Pauli's exclusion principle. Consequently, one of the two possibilities will occur; either Pauli's exclusion principle would be violated and the black hole would collapse to a singularity, or the collapse of the black hole to a singularity would be inhibited by Pauli's exclusion principle, and the black hole would eventually explode with a mini bang of a sort. After explosion, the remnant core would stabilize as a quark star.

    the objects identified as black holes are actually quark stars. suppose for the sake of argument he is correct. what are the implications to string/LQG/bh physics on such issues as entropy thermodynamics holography hawking radiation firewalls information paradox if black holes are quark stars.
    Last edited: Aug 16, 2015
  5. Aug 16, 2015 #4


    User Avatar
    Gold Member

    Its strange that you guys are assuming that the paper is saying that a black hole is a quark star, it isn't!
    Its obvious from the above part, that the paper is suggesting that the scenarios that people usually don't assume to be a single class of scenarios with the same result of a black hole, should be divided into two classes, one that gives a blackhole as a result and another that gives a quark star as a result. This paper is only suggesting its not "neutron star for this much mass, blackhole for more massive" but " neutron star for this much mass, quark star for more massive, blackhole for yet more massive". I don't see what part of this suggestion is new.
  6. Aug 17, 2015 #5


    User Avatar
    Science Advisor
    Gold Member

    Note that this paper was never published in a peer reviewed journal, and it has exactly zero citations (which means experts in the field believe it irrelevant, not even worth disputing).

    On the other hand, broadly speaking, there is nothing wildly implausible about the speculations in this paper. It notes (correctly) that singularity theorems assume the correctness of GR at all energy scales, while most physicists doubt this is true. Is it the most likely candidate for what there is instead of singularity? Who knows, but probably not.
  7. Aug 22, 2015 #6
    I would think that it might be a possibility after the black hole has went throuh Hawking radiation.

    P.S. Highly advise to ignore me since I am an amateur compared to the rest on the site.
  8. Aug 22, 2015 #7
    ok can you peer review it?

    what is the most likely candidate for what there is instead of singularity?
  9. Aug 22, 2015 #8


    User Avatar
    Science Advisor
    Gold Member

    No one is going to do peer review on demand. Further, I am not a professional physicist and this is not my area of greatest expertise.

    However, purely as a matter of opinion, my personal guess for the most likely alternative to a singularity is the fuzzball picture:

    Last edited: Aug 22, 2015
  10. Aug 24, 2015 #9


    User Avatar
    Gold Member

    There are a several claims made in this paper which are only loosely related to each other that should each be evaluated on its own merits.

    The first claim is that a handful of objects that have been observed may be quark stars because they are too small and too dense to be neutron stars. The natural alternative to this claim would be that we have misunderstood something about the condensed matter physics of neutron stars (theoretical error), or that measurement error of some undetermined nature makes objects that are really neutron stars or small black holes look like something else. Given that our models of neutron stars are fairly crude and the precision of QCD calculations is not very great, particularly in complex systems, and that there objects are outliers in very large astronomy data sets (such that a several sigma deviation for the best fit value would be expected for a few data points out of all the data points measured), those explanations sound pretty convincing.

    The big problem with this data point in relation to the claim that follows is that is the mechanism proposed below creates quark stars, then quark stars should be ubiquitous. Even if one in a ten thousand stars that collapse into quark stars when they would conventionally be expected to form neutron stars or black holes are in a sweet spot where a quark star trajectory is impossible, we would expect to see far more quark star candidates.

    If the objects observed really are quark stars, one needs a mechanism that produces far fewer of them than the proposed mechanism would be expected to produce.

    One plausible sort of mechanism that I can imagine that would produce the right number of observed events plus or minus, would be one in which a quark star is relatively short lived state that either goes nova, or transforms into some other better known state after some period of time from say, a few dozen years to a tens of millions of years. It needs to be long lived enough to be observed in repeated observations of an object from Earth during time periods when we had telescopes sufficient to see them, yet short lived enough to be very uncommon. If it were stable for time periods on the order of billions of years or even hundreds of millions of years, there would be far too many of them to match astronomy observations. For example, perhaps a quark star that subsequently gains additional mass by accretion becomes a black hole as soon as it acquires enough additional mass.

    Another plausible mechanism that I can imagine would produce a quark star only in a truly tiny range of initial conditions (perhaps only in stars in a mass range of 0.001 solar masses between the neutron star and black hole threshold with virtually on outside gravitational forces preventing the mass distribution within the collapsing star from being anything other than perfectly spherically symmetrical) squeezed between those that produce a neutron star and those that produce a black hole, whose extreme rarity because the initial conditions requirements are so demanding, almost never happens but do happen in a handful of outlier cases. This might be compared by analogy to water that retains a phase outside the usual conditions of a phase diagram because it is so homogeneous that the phase change transition isn't triggered until it does so explosively one the slightest bit of anisotrophy is introduced into the system.

    In either case, for the reasons discussed below, a trajectory of evolution that does not involve a black hole as an intermediate state would be more plausible.

    Certainly, the claim that a black hole cannot collapse to a true singularity due to Pauli's exclusion principle is a common place one in pretty much any theory of quantum gravity. Almost nobody is lining up to propose theories that Pauli's exclusion principle is violated inside black holes to form true singularities. And, indeed, the density of neutron stars and black holes is such that violation's of Pauli's exclusion principle are not needed to explain any observable phenomena.

    Most theorists decline to speculate on what is happening inside a black hole on the grounds that it is inherently not observable. But, there is nothing deeply troubling about following the laws of physics to their logical conclusion inside a black hole. The claim that the interior of a black hole collapses not to a singularity but towards a quark star as noted above, to the extent that it concerns the inner workings of a black hole is "not even wrong."

    Far more controversial is the further claim that these speculations about the interior of a black hole have an observable consequence at some point as this paper suggests because a quark star inside a black hole would "explode with a mini bang of a sort" and that after the explosion, the remnant core "would stabilize as a quark star", although if the circumstances in which a mini bang were triggered were rare enough, it would provide an alternate explanation for the rarity of quark stars.

    One of the reasons that this analysis is suspect has to do with Black Hole entropy. The late Jacob Bekenstein showed that the notion of black holes in GR and the Second Law of Thermodynamics which holds that entropy always increases, are not in conflict if a black hole is a state of maximum entropy which he showed in a calculation establishing that entropy of a black hole based upon observable quantities on its event horizon and making a few other key assumptions.

    For a black hole to "explode with a mini bang of a sort" that left a remnant core that would stabilize as a quark star, one would have to show that the quark star had more entropy than the black hole state that existed before the mini bang, so as not to violate the Second Law of Thermodynamics (or alternatively, that this circumstance was a singular exception to the Second Law of Thermodynamics). Neither of these possibilities seem very likely. Naively speaking, one would expect quark stars which are quite specific sets of microstates to have lower entropy than black holes, although perhaps higher entropy than neutron stars. There is also zero evidence for a black hole nova being directly observed.

    * * *

    As a final aside, unlike PAllen, I wouldn't automatically discount the ideas in a paper merely because it wasn't published and has no citations in an eight year period (even assuming that this is the case). First of all, "Sleeping Beauty papers" which go unnoticed for years and then suddenly see a surge of citations are a well known phenomena in science. http://washparkprophet.blogspot.com/2015/05/sleeping-beauty-papers.html

    There are also a variety of reasons that a nearly finished paper wouldn't be published that have nothing to do with failing peer review. The investigator may be inept at following through on getting something published, may have seen another paper published around the same time that said exactly the same thing that may have been unknown to him until a peer reviewer pointed it out to him or he found it in a final polishing of the literature review pre-publication, the investigator may have simply gotten busy and never gotten around to resubmitting the paper, the investigator could have left academia for private industry and found that getting published was no longer a priority in his new position, or the ideas in the paper could have been incorporated into a new and better paper with a different name and different spin perhaps rendering the preprint obsolete. This author, for example, incorporated some of the same ideas into a 2011 preprint also incorporating the Pauli exclusion principle, this time in a Big Bang context: http://arxiv.org/abs/1103.3688 Or, the investigator could simply have gotten a bad peer reviewer who demanded too much to make it worth following through upon. These requests are sometimes reasonable and sometimes not. As physical anthropologist John Hawks has noted: "Peer review as practiced today is a form of hazing." http://johnhawks.net/weblog/topics/metascience/journals/peer-review-hazing-2015.html

    A lack of publications and citations certainly don't provide automatic credibility to a paper that is present when publication and citations are present. But, their absence alone isn't a reason to discount a pre-print, particularly if the author is a professional physicist. This author has 11 other co-authorships from 2012-2015 as an investigator with a dark matter direct detection experiment's collaboration, as well as the 2011 paper mentioned above, a 2009 published paper http://arxiv.org/pdf/0901.1956.pdf, a published 1982 paper http://adsabs.harvard.edu/full/1982Ap&SS..84...99T, and so is clearly a professional physicist. http://arxiv.org/find/astro-ph/1/au:+Thakur_R/0/1/0/all/0/1 He appears to be a professor at a University in India. http://www.prsu.ac.in/departments/Physics/Physics.html [Broken] While his paper didn't produce a lot of acclaim it may have been pivotal in getting hired for these jobs, suggesting his employers did not find it to be too off base.

    In any case, if I'm not misreading the data, this particular paper actually does appear to have been published as a manuscript in the Journal "Astronomy and Astrophysics" on February 5, 2008 http://arxiv.org/pdf/astro-ph/0702671.pdf and to have received one citation in this paper: http://arxiv.org/abs/gr-qc/0512088 It also received a bit of discussion of several serious science blogs maintained and most read by scientists or well educated laymen.

    While this still isn't terribly impressive, it is quite close to the median outcome and certainly suggests that it shouldn't be written off simply based upon "meta" analysis related to its authorship, publication status and citation history.
    Last edited by a moderator: May 7, 2017
  11. Aug 24, 2015 #10
    Hi thanks for replying. if there is a quark star inside every "black hole" how does it effect the bh issues i've identified like information paradox etc
  12. Aug 24, 2015 #11


    User Avatar
    Gold Member

    If there is a quark star in every black hole, this might reduce the entropy we expect in a black hole since the partition of its mass-energy into a quark star component and an non-quark star component would reduce the number of possible microstates and hence the entropy of the black hole, which would reduce the amount of information it could hold, albeit while structuring that information somewhat. I don't have the capacity to rigorously analyze that difference quantitatively however.
  13. Aug 24, 2015 #12
    i'll post another paper on this soon i'd love to hear your take on it thanks.
  14. Aug 25, 2015 #13
    [Mentor's note: Post merged with this thread]

    in response to

    what this paper is arguing is that many objects identified as "stellar mass black holes" are actually color-flavor locked quark stars.

    a quark star that absorbs all electromagnetic radiation would appear to be identical to a black hole, except instead of an event horizon, you have the surface of the quark star. apparently the quark star radius is slightly above the schwarzschild radius

    Can stellar mass black holes be quark stars?

    Z. Kovacs, K. S. Cheng, T. Harko
    (Submitted on 19 Aug 2009)
    We investigate the possibility that stellar mass black holes, with masses in the range of 3.8M⊙ and 6M⊙, respectively, could be in fact quark stars in the Color-Flavor-Locked (CFL) phase. Depending on the value of the gap parameter, rapidly rotating CFL quark stars can achieve much higher masses than standard neutron stars, thus making them possible stellar mass black hole candidates. Moreover, quark stars have a very low luminosity and a completely absorbing surface - the infalling matter on the surface of the quark star is converted into quark matter. A possibility of distinguishing CFL quark stars from stellar mass black holes could be through the study of thin accretion disks around rapidly rotating quark stars and Kerr type black holes, respectively. Furthermore, we show that the radiation properties of accretion disks around black holes and CFL quark stars are also very similar. However, strange stars exhibit a low luminosity, but high temperature bremsstrahlung spectrum, which, in combination with the emission properties of the accretion disk, may be the key signature to differentiate massive strange stars from black hole.
    Comments: 27 pages, 5 figures, accepted for publication in MNRAS
    Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
    Journal reference: MNRAS, 400, pp. 1632-1642 (2009)
    DOI: http://arxiv.org/ct?url=http%3A%2F%2Fdx.doi.org%2F10%252E1111%2Fj%252E1365-2966%252E2009%252E15571%252Ex&v=08e0698b [Broken]
    Cite as: arXiv:0908.2672 [astro-ph.HE]
    (or arXiv:0908.2672v1 [astro-ph.HE] for this version)

    if the above paper is correct that astrophysical astronmical objects identified as black holes are actually "stellar mass black holes" are actually color-flavor locked quark stars

    how does this "quark star black hole" effect black hole issues from hawking radiation to black hole information paradox black hole entropy firewall holographic principle
    Last edited by a moderator: May 7, 2017
  15. Sep 28, 2015 #14
    and "In this paper it is shown that a black hole cannot collapse to a singularity".

    I agree. Ultra-relativistic pressure (like conventional pressure) increases as the inverse of r-cubed, faster than the forces of gravity increase. The formulas I use for calculating an ultra relativistic star’s size are: Ultra relativistic pressure P = (rho)(c^2)/3, implying a viral energy of M(c^2)/3. GPE = 1.1G(M^2)/R. Virial equation energy ratio = 2.0
    This gives a star size = 1.65GM/(c^2), or 0.82 of the Schwarzschild radius.
  16. Sep 28, 2015 #15


    User Avatar
    2017 Award

    Staff: Mentor

    Gravity is not linear. Pressure actually increases the energy density, at some points it supports the collapse instead of slowing it.
  17. Sep 28, 2015 #16
    papers imply a lot of the energy is radiated away so it loses mass at same time
  18. Sep 29, 2015 #17
    Are you using the Tolman-Volkoff equation for that conclusion? This equation gives bad results for neutron star, let alone a black hole. If a star was significantly smaller than 1.0 SR, I think at 0.9 SR the gravitational acceleration would be about 0.8 that at 1.0 SR, a large number but still very finite. The core pressure in a neutron star is significantly less than (rho)(c^2)/3, which to me indicates that the next stage of support pressure after neutron collapse would be (rho)(c^2)/3.
  19. Sep 29, 2015 #18
    Correction: I meant to write: Are you using the Tolman-Volkoff equation for that conclusion? This equation gives bad results for neutron star, let alone a black hole. If a star was significantly smaller than 1.0 SR, I think at 0.9 SR the gravitational acceleration would be about 1/0.8 that at 1.0 SR, a large number but still very finite. The core pressure in a neutron star is significantly less than (rho)(c^2)/3, which to me indicates that the next stage of support pressure after neutron collapse would be (rho)(c^2)/3.
  20. Sep 29, 2015 #19


    User Avatar
    Science Advisor
    Gold Member

    A few meta-points:

    1) If you assume the dominant energy conditions holds (as it does microscopically, and exactly for classical theories like Maxwell EM), then horizon and singularity formation are inevitable for a wide range of initial conditions, as proven by Hawking and Ellis. No specific theory of matter need be assumed. Note that the dominant energy condition is also what is required to establish that the field equations of GR imply that small bodies move on timelike world lines. Violating it (macroscopically) implies bodies that can move FTL.

    2) Almost no one believes (1) describes the what actually happens for collapsed states. There are two very different types of deviations expected:

    a) Quantum theories violate the dominant energy conditions. There are bounds on the violation, but, to the best of my knowledge, there is no proof that these bounds recover the singularity theorems.

    b) It is expected that GR is only a classical limit of a more accurate theory.

    Given (2), irrespective of detailed matter models, there is no reason to believe a singularity forms. The majority view is that 'something macroscopically similar to a horizon' forms, but it is wide open what its microscopic structure is (and whether it acts like a firewall). The basis for believing that something like a horizon must form is that (especially for larger) BH, the collapse up to a horizon is not expected to have any meaningful deviations from the dominant energy condition, nor are quantum gravity corrections expected to be significant until well inside the horizon.

    The more interesting, controversial claim for quark stars is not the possibility of such a state inside a macroscopic horizon, but the claim for such a possibility preventing an effective horizon forming. This requires deviation from GR with dominant energy condition under relatively non-extreme conditions (especially if supermassive BH are to be avoided).
  21. Sep 29, 2015 #20
    If such a state as a quark star does exist it's an intermediate state between a neutron star and the traditional black hole.
    A distinct final state of degenerate matter as a free quark soup is unknown but it's a definite maybe.
    It would dispense with that annoying singularity (I think).
    Could a hypothetical quark star form an event horizon?, if so then 'black hole' and 'quark star' could be just two names for the same thing.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook