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If BH do not exist, would string & LQG be falsified?

  1. Sep 23, 2009 #1
    If Black holes do not exist, would string & LQG be falsified?

    Suppose that black holes do not exist in nature, in that the quantum properties of matter prevents density from increasing beyond a certain limit, as well as gravity's strength diminishing at higher energies. Stellar objects can collapse up to a certain density before new previously unknown physics takes over. GR becomes invalid a description of BH beyond a certain range of distances.

    One paper for example,
    speaks of dark energy stars

    There is no hawking radiation as they apply to BH, no information loss. "Dark stars" follow the usual entropy laws, adding energy increases its heat, losing energy cools it off (BH follow the reverse) Instead of singularities and infinite densities, dark stars undergo a phase transition analogous from solid to liquid.

    If the above were true, would it falsify string theory and LQG, which of course, both predict BH's (but not dark energy stars) and BH entropy.
    Last edited: Sep 23, 2009
  2. jcsd
  3. Sep 23, 2009 #2


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    Gold Member

    No, on the contrary, it would tend to corroborate string theory, since what is called black hole there is actually a "fuzzy sphere", which is closer to what you are thinking.
  4. Sep 24, 2009 #3


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    LQG does not predict black holes in the usual sense. It associates an entropy to a quantum object analogous to a black whole, which has some unusual properties. As far as I know the eqations of LQG are not fully solved for BHs, so one has to deal with approximations; the most common one in which dynamics can be studied to a certain extent is to restrict to the subspace of spherical symmetric solutions. This theory with a finite number of degrees of freedom is called LQG (C for cosmology). One central prediction is that gravity induces a repulsive force to matter degrees of freedom at small distances avoiding the collaps to a singularity (applies to the big crunch as well which is replaced by a big bounce). The quantum gravity repulsion becomes important below ~ 100 * Planck Length; in the long distance limit the theory reproduces well-known spherical symmetric solutions of GR.

    So as a summary there should be objects in full LQG which correspond to black hole. They should have an event horizon, but no singularity.
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