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String Theory: Higgs and Blackholes

  1. Sep 17, 2008 #1
    First question:
    Since a neutral Higgs boson is its own anti-particle, and has zero spin, it appears to have zero for all quantum numbers (in the standard model). This is what one would expect as well for the smallest neutral blackhole with no angular momentum.

    What "new" quantum numbers does a candidate quantum gravity theory, like String Theory, suggest which would distinguish between a Higgs and neutral non-spinning blackhole?

    Second question:
    Are there any other candidate quantum gravity theories which also include matter at this point? (ie. are there other theories I could ask the first question of as well?)

    Third question:
    Does string theory predict a particle which by its quantum numbers would be considered to be a blackhole, yet is too light to be confined in a classical event horizon? Basically, a 'black hole' so light it is naked purely do to quantum mechanics? (Is there a term for this? That would help me in searches for references.)

    I realize that a lot of this may not have definitive answers yet (especially the last one due to almost necessary vagueness), but I know there are a lot of intellegent people here working with string theory and I would very much appreciate your candid opinions and even educated speculation (please qualify it though, so I know it is educated speculation and not direct answers).
  2. jcsd
  3. Sep 17, 2008 #2
    I am really, REALLY not qualified to answer this question... but:

    As I understand the important thing about the Higgs is the Higgs field, which permeates everything... insofar as the actual Higgs Boson particles go, such as you would see in a particle accelerator, they are only one component of the Higgs field, and if I am not terribly mistaken (?) even though the field is omnipresent you don't really see those lone massive-Higgs-Boson particles except during unusual events such as a particle accelerator collision.

    So I don't know the answer to your question, but what I would ask is-- even if you could demonstrate a higgs boson is in some sense similar to a black hole, would that tell us anything about the pervasive Higgs field, or the other three goldstone bosons that make up that field besides the massive Higgs Boson itself?

    The only other such candidate I'm aware of is the "braid matter" program, which spun off of Loop Quantum Gravity. Braid matter takes LQG, which formerly was only a theory of spacetime, and introduces matter to it by suggesting that particles are actually little mobile knots in the spacetime fabric; an example of research in this area is here. However "braid matter" is really absolutely in its infancy and very little is known about it or even whether it works. I do not know enough about LQG or braid matter to tell you what a black hole or a higgs boson looks like in braid matter; I'm not even sure whether braid matter is well-developed enough for those questions to be answerable...
  4. Sep 17, 2008 #3
    I guess it could indicate that in some sense gravity itself caused the spontaneous symmetry breaking. But I don't want to really speculate about stuff like that (because I don't know enough to make educated speculation), and because I assume the Higgs and blackhole are actually entirely different beasts. The point is that using the standard model quantum numbers, it appears the Higgs and blackhole have the same quantum numbers ... so what do current quantum gravity candidates offer as extra quantum numbers (which I assume will clearly distinguish them).

    Yeah, that is not really a mature enough program to answer stuff like this yet.

    Hopefully string theory can give some insights though.
  5. Sep 17, 2008 #4
    You're saying that any single particle excitation of a chargeless, massive scalar field is a chargeless, ang. mom. zero black hole.

    I don't follow the logic. To get a (nonspinning, uncharged) black, you need to squeeze some mass into a sphere with radius smaller than the Schwarzschild radius. The estimated mass of the Higgs (if it exists) is tiny compared to the gravitational constant G.

    Given that any Higgs particle will have some finite spread in momentum space, it will also have some finite spread in position space. It will not be localised enough in space to be a black hole.
  6. Sep 17, 2008 #5
    No. I am not saying that.

    What I'm saying is that in the standard model the Higgs has the same quantum numbers as a neutral blackhole with no angular momentum. Do you agree with that?

    So the question is, in candidate theories of quantum gravity ... do such theories provide new quantum numbers such that they DON'T have the same quantum numbers?

    I'm asking about predictions of candidate theories of quantum gravity (such as string theory).
  7. Sep 18, 2008 #6


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    "What I'm saying is that in the standard model the Higgs has the same quantum numbers as a neutral blackhole with no angular momentum."

    What??? A microscopic blackhole is a composite gravitational entity with spatial extent (and a horizon) and it can have any mass. It is not a point particle! Moreover it does not arise from a Higgs field (the VeV is wrong by many orders of magnitude).

    The decay signatures are also completely, one hundred percent different. So for instance you would see a thermal spectrum radiating from a microscopic blackhole (if it was sufficiently massive it could actually radiate a Higgs for instance) and in typical TEV RS like scenarios, you would see rather spectacular Kaluza-Klein cascades. They arrise from completely different mechanisms, assuming microscopic TEV bhs even exist.
  8. Sep 18, 2008 #7
    Again, as I stated in my last post, I am not claiming the Higgs results in a blackhole.

    But can't the evolution on the outside of the event horizon only be dictated by what information is available on the outside?

    I guess that was the implicit assumption I was making. Which would make the blackhole outside couple with any fields, etc. with the same quantum numbers as the Higgs. Unless quantum gravity theories introduced some new quantum numbers that made them couple differently ... which is what I was hoping was the solution to this.

    Okay, let's put it this way: in a hypothetical situation in which the gravitational coupling runs _drastically_ such that all forces are combined at the TeV scale, and it turns out there is a blackhole and a Higgs of roughly the same mass. How would you distinguish between them if they have the same quantum numbers? And if decay is dominated by thermal decay, this depends solely on gravitational coupling which depends on the mass, so they would appear the same.

    I was guessing that quantum gravity theories provided some new quantum numbers that would distinguish them, so they would couple differently to something.

    From your response it sounds like the fact that the internals are composite would demonstrate itself somehow through couplings to fields, even outside of the event horizon. So they would be easily distinguishable anyway. Is this correct?

    If so, that doesn't sound like an event horizon at all, since 'events' are leaking out anyway. Would black holes at this scale then just be defined as: composite systems bound primarily by gravity (and the concept of an event horizon is not really applicable)? If so, then that clears up a lot of my questions here.

    Thank you for your responses.
  9. Sep 18, 2008 #8
    Imagine the sun wasn't rotating, and let's assume it is electrically neutral, for now. Then yes, the spacetime surrounding the sun is identical to the spacetime region outside a black hole. To that extent yes, what's going on inside doesn't really matter.

    But then the mass of a Higgs is far too small for the curvature "outside" to be detectable.
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