4 ms·

Thanks Roy for stating the obvious, someone needed to do it. Next: renormalization.

amai 3y ago
Problem is that gravity is generally thought to be non-renormalizable: https://arxiv.org/abs/0709.3555 https://arxiv.org/abs/0709.3555
heyoni 3y ago
For those of us that didn’t think anything about black holes was obvious, what’s up with Roy? He chasing clout or something?
- defrost 3y ago
  He's got enough clout and awards for a soccer team already, his Marcel Grossmann Award has gravitas ... He's on the cusp of 90 and getting salty still hearing about singularities on pop sci TV shows I guess. From his conclusion: The author’s opinion is that gravitational clumping leads inevitably to black holes in our universe, confirming what is observed, but this does not lead to singularities. It is true that there are ”proofs” that the curvature of a non-rotating one is infinite at its central point. These all assume that matter is classical and that it satisfies whatever nineteenth century equation of state the proponents require to prove whatever it is that they wish to prove. Equations of state assume that all variables, such as pressure and volume, occur in the simplest algebraic fashion. This may be true for the low density laboratory or engineering experiments but perhaps not at black hole densities. The author has no doubt, and never did, that when Relativity and Quantum Mechanics are melded it will be shown that there are no singularities anywhere. When theory predicts singularities, the theory is wrong! A stellar example of Max Academic shade * ”airquotes” * "whatever nineteenth century" * "low density" .. "engineering"
  - slowmovintarget 3y ago
    So basically a swift whack on the chalkboard with a pointing stick, followed by "Pay attention, class!"
- throwaway81523 3y ago
  I doubt it? https://en.wikipedia.org/wiki/Roy_Kerr https://en.wikipedia.org/wiki/Roy_Kerr
- pdonis 3y ago
  > what’s up with Roy? My read is that he is disappointed that certain lines of research that could have come from his original publication of the black hole solution that is named after him, did not actually get pursued by the community. He describes at least some of them in the paper. Unfortunately, for reasons that I have pointed out elsewhere in this discussion, I don't think the kinds of models he appears to be interested in are actually viable physically, however interesting they might be mathematically.
ajkjk 3y ago
Renormalization is on relatively good footing these days. Nobody claims that it's a "final theory", but the argument that "the same theory may work with different values for the constants depending on what energy scale you cut off at" is totally legitimate. The remaining confusion, such as "why the hell do we have to do it though", is really QFT's fault for being perturbative (and likely just incomplete).
deleted 3y ago
[deleted]
QuadmasterXLII 3y ago
Kerr as in "Kerr Metric"
- bluish29 3y ago
  Yes, Roy Kerr is the one to find the solution of GR equation for uncharged rotating black hole. The solution is called kerr metric after him. In contrast to say -Schwarzschild- metric as solution of stationary uncharged black hole (usually is what people refer to when they say black hole).
  - bmitc 3y ago
    Schwarzschild black holes are not known to actually exist though, are they? It is my understanding that most actual black holes are Kerr black holes.
    - pantulis 3y ago
      Basically yes. Angular momentum is conserved so real black holes either receive angular momentum from the stuff they ingest or inherit it from the remnants of the originating star. Not so sure of possible micro black holes.
godelski 3y ago
It hasn't been universally accepted that singularities mean infinite gravity. Nor has it been universally accepted that singularities are an error or limitation in the mathematical model. There's a lot of nuances missed when communicating complex concepts to laymen. Honestly, this should be considered stating the obvious as no one would reasonably complexity something that need not be. With the corollary, not all people are physicists that are well studied in quantum mechanics and general relativity (especially up to the graduate levels). None of this is obvious to physicists, so if it is to you I'd suggest publishing.

amai 3y ago

Problem is that gravity is generally thought to be non-renormalizable: https://arxiv.org/abs/0709.3555 https://arxiv.org/abs/0709.3555

heyoni 3y ago

For those of us that didn’t think anything about black holes was obvious, what’s up with Roy? He chasing clout or something?

defrost 3y ago
He's got enough clout and awards for a soccer team already, his Marcel Grossmann Award has gravitas ... He's on the cusp of 90 and getting salty still hearing about singularities on pop sci TV shows I guess. From his conclusion: The author’s opinion is that gravitational clumping leads inevitably to black holes in our universe, confirming what is observed, but this does not lead to singularities. It is true that there are ”proofs” that the curvature of a non-rotating one is infinite at its central point. These all assume that matter is classical and that it satisfies whatever nineteenth century equation of state the proponents require to prove whatever it is that they wish to prove. Equations of state assume that all variables, such as pressure and volume, occur in the simplest algebraic fashion. This may be true for the low density laboratory or engineering experiments but perhaps not at black hole densities. The author has no doubt, and never did, that when Relativity and Quantum Mechanics are melded it will be shown that there are no singularities anywhere. When theory predicts singularities, the theory is wrong! A stellar example of Max Academic shade * ”airquotes” * "whatever nineteenth century" * "low density" .. "engineering"
- slowmovintarget 3y ago
  So basically a swift whack on the chalkboard with a pointing stick, followed by "Pay attention, class!"
throwaway81523 3y ago
I doubt it? https://en.wikipedia.org/wiki/Roy_Kerr https://en.wikipedia.org/wiki/Roy_Kerr
pdonis 3y ago
> what’s up with Roy? My read is that he is disappointed that certain lines of research that could have come from his original publication of the black hole solution that is named after him, did not actually get pursued by the community. He describes at least some of them in the paper. Unfortunately, for reasons that I have pointed out elsewhere in this discussion, I don't think the kinds of models he appears to be interested in are actually viable physically, however interesting they might be mathematically.

ajkjk 3y ago

Renormalization is on relatively good footing these days. Nobody claims that it's a "final theory", but the argument that "the same theory may work with different values for the constants depending on what energy scale you cut off at" is totally legitimate. The remaining confusion, such as "why the hell do we have to do it though", is really QFT's fault for being perturbative (and likely just incomplete).

deleted 3y ago

[deleted]

QuadmasterXLII 3y ago

Kerr as in "Kerr Metric"

bluish29 3y ago
Yes, Roy Kerr is the one to find the solution of GR equation for uncharged rotating black hole. The solution is called kerr metric after him. In contrast to say -Schwarzschild- metric as solution of stationary uncharged black hole (usually is what people refer to when they say black hole).
- bmitc 3y ago
  Schwarzschild black holes are not known to actually exist though, are they? It is my understanding that most actual black holes are Kerr black holes.
  - pantulis 3y ago
    Basically yes. Angular momentum is conserved so real black holes either receive angular momentum from the stuff they ingest or inherit it from the remnants of the originating star. Not so sure of possible micro black holes.

godelski 3y ago

It hasn't been universally accepted that singularities mean infinite gravity. Nor has it been universally accepted that singularities are an error or limitation in the mathematical model. There's a lot of nuances missed when communicating complex concepts to laymen. Honestly, this should be considered stating the obvious as no one would reasonably complexity something that need not be. With the corollary, not all people are physicists that are well studied in quantum mechanics and general relativity (especially up to the graduate levels). None of this is obvious to physicists, so if it is to you I'd suggest publishing.