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Mar
30
revised Are black holes very dense matter or empty?
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Mar
30
revised Are black holes very dense matter or empty?
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Mar
29
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Mar
29
revised Are black holes very dense matter or empty?
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Mar
29
revised Are black holes very dense matter or empty?
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Mar
29
comment Are black holes very dense matter or empty?
@John Rennie No, I am not claiming that GR breaks down as you cross the event horizon. I am saying that, in order to know what happens with the matter inside a BH we need more. The fact that the Planck length is much smaller does not mean that it is not important for that question. Length's are relative also. I am not saying that something disastrous happens as the matter crosses the horizon. Nevertheless we should have GR as the limit of a quantum theory to truly understand BH's.
Mar
29
comment Are black holes very dense matter or empty?
To rephrase it: The Schwarzschild solution of GR is one which holds in an idealized settings which ignores known details but also the fact that we don't really know what happens in these extreme situation. It is furthermore singular which most see as indication that it is wrong in an environment of the singularity. GR alone does not tell us what happens to the matter inside the BH.
Mar
29
comment Are black holes very dense matter or empty?
For the ad-hoc quantisation of gravity to break down you don't need to go all the way to the singularity. It breaks down due to a different kind of singularity -> renormalizability. The OP asked about the matter inside the BH. Since it is a matter of definition where a BH starts, we need to contemplate that somewhere on the way to the BH singularity a quantum version of GR applies, supposedly. We thus don't know the appropriate theory and can only hope that its limit is close enough to GR.
Mar
29
revised Are black holes very dense matter or empty?
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Mar
29
revised Are black holes very dense matter or empty?
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Mar
29
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Mar
29
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Mar
29
revised Are black holes very dense matter or empty?
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Mar
29
comment Are black holes very dense matter or empty?
A BH in GR is a mathematical singularity in a field theory. Most physicists agree that this theory is the classical limit of a quantum theory yet to be identified (because of such problems with GR). The straight-forward approach to a quantum gravity fails (because of a singularity) if the curvatures are as strong as those of BH's. Therefore, GR is in this case a-priori not the appropriate theory. This does however not mean that the particular prediction of the existence of BH's is wrong. Similarly, the failure of Newtons theory did not mean that its prediction of dark stars was wrong.
Mar
29
answered Are black holes very dense matter or empty?
Mar
4
revised Initial value dependence of slow-roll inflation
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Mar
4
asked Initial value dependence of slow-roll inflation
May
26
comment Can elementary particles be rightfully considered quasiparticles?
In S-matrix formalism (which I think is limited for unstable particles) particle=state and the states have a specific (on-shell) four momentum from it I may compute mass (and width). Is this what you mean?
May
26
awarded  Commentator
May
26
comment Can elementary particles be rightfully considered quasiparticles?
@CuriousOne I tried to explain that I am not thinking of balls of some sort.