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Here is what I believe is the most relevant paper by Moschidis: https://arxiv.org/abs/1812.04268 https://arxiv.org/abs/1812.04268 I find it mildly amusing tha

Here is what I believe is the most relevant paper by Moschidis: https://arxiv.org/abs/1812.04268 https://arxiv.org/abs/1812.04268 I find it mildly amusing that this work is being done by mathematicians rather than theoretical physicists.

state_less 6y ago
Didn't Einstien use Minkowski's geometry for his key theories? Seems like it's helpful to have a few mathematicians involved in the project.
- javajosh 6y ago
  Not really my field, but I think Riemann had more of an impact on Einstein in that he was looking for a mathematical structure that fit his intuition about spacetime, and he dug up a 50-year old theory and applied it to GR. My understanding is that Einstein was searching for a long time for the right tool, and went down a lot of dead-end paths, before he discovered Riemann geometry.
  - pmiller2 6y ago
    As I recall my history, it was actually believed that Einstein's first wife, Mileva Marić Einstein, who provided at least some of the mathematical muscle needed for GR [0]. --- [0]: https://blogs.scientificamerican.com/guest-blog/the-forgotten-life-of-einsteins-first-wife/ https://blogs.scientificamerican.com/guest-blog/the-forgotte...
    - qchris 6y ago
      I definitely agree he had a mathematician working with him to help, but am not sure it was his wife. I think that there's varying interpretations of her contributions to A. Einstein's work. If I'm remembering correctly, Walter Isaacson's Einstein biography tended towards says that she didn't truly contribute much to any of the work he did around that time, but that he did have a colleague or two formally trained in non-Euclidean geometries that he spent a lot of time working on GR with.
      - agonz253 6y ago
        It was Marcel Grossman who introduced him to Riemman's work: https://en.wikipedia.org/wiki/Marcel_Grossmann https://en.wikipedia.org/wiki/Marcel_Grossmann There is no evidence that his wife provided any of the "mathematical muscle needed for GR", nor is there reason to suspect that she would have been in a position to do so, since she was not a mathematician and had failed the undergraduate physics degree at the institute where she met Einstein (Einstein himself barely passed though). [0] https://www.springer.com/gp/book/9781402039997 https://www.springer.com/gp/book/9781402039997
      - pmiller2 6y ago
        > If I'm remembering correctly, Walter Isaacson's Einstein biography tended towards says that she didn't truly contribute much to any of the work he did around that time.... I'm not sure how much credence I'd put in such an assertion given that Einstein himself wrote in a letter to Mileva: > “When I read Helmholtz for the first time, it seemed so odd that you were not at my side and today, this is not getting better. I find the work we do together very good, healing and also easier.” Emphasis added by me. Having not read the book, Isaacson might have some additional evidence and insights I'm not aware of, but who knows?
        agonz253 6y ago
        > “When I read Helmholtz for the first time, it seemed so odd that you were not at my side and today, this is not getting better. I find the work we do together very good, healing and also easier.” Note that this was written when they were both undergraduate students and would study together.
        pmiller2 6y ago
        There are other examples in the SA article I posted, including a letter from 1905 where Einstein talks about their "work on relative motion."
      - deleted 6y ago
        [deleted]
  - webdva 6y ago
    Inspiring persistence.
godelski 6y ago
I don't find this surprising at all. Theoretical physicists are really just applied mathematicians. I don't know a physicist that would disagree with this. In fact, many said Einstein was more a mathematician than a physicist.
- evanb 6y ago
  Sort of. As a physicist I'd also say we have different sets of intuition, different willingnesses to play fast and loose or to make heuristic arguments (for a good example, consider the history of the Dirac delta function). Certainly physicists apply mathematics; does that make them applied mathematicians? I'm not certain. On the other hand, while I find these sorts of theorems nice results, they do not change one bit of my understanding.
- paulpauper 6y ago
  agree . the top theoretical physicists are effectively top mathematicians, too. Witten got a Fields Medal. you need to understanding algebraic geometry, topology, diff. geometry, diff. equations, numerical analysis, special functions, stats, etc. to be a top physicist. Pretty much everything is pure math.
piokoch 6y ago
I don't think theoretical physicists would find these findings to be that interesting. There are a lot of mathematical results that can be somehow applied to physics, but very rarely something interesting comes out of it from physicists perspective. Obviously when it happens, then it can lead to a breakthrough as it happened when Einstein figured out how Riemmann geometry can be applied to GR. The author himself is kind of uncertain if there are any real consequences comming out of his math: >>The instability of AdS space-time has major implications for how we understand our own universe. First, since AdS space-time is unstable, it’s “something you will not see in nature,” Moschidis said.<< >>But “even though AdS is not real,” he said, “it can still lead us to the discovery and study of real phenomena.” << I am not sure how our understanding of time-space can be increased by a theory that just does not describe reality. Maybe the math is somehow useful? Maybe this might explain what happened after Big Bang (maybe instabilities were more common then)? Maybe this is the path to unify QM and GR (in the article it is mentioned that, but with some usual addition of not yet observed additional dimension that can explain everything - the feature of many "string" theories", that didn't give us much.
- andrewflnr 6y ago
  It's definitely not the case that AdS being non-physical stops it from being useful in physics. ADS-CFT plays a big role in physics research today. I'm hoping that seeing how it breaks down will lead to clues about exactly where it diverges from the real world.
- abdullahkhalids 6y ago
  Theoretical physics has always studied theories that don't describe reality. It deepens our understanding of the theories that do describe reality. Eg., if you change one axiom of a reality-describing-theory and certain naturally occurring phenomena disappears, then you can say that that axioms causes that that phenomena to occur. Also, this is not my field, but thousands of physics papers have been written on the AdS geometry (particularly the AdS-CFT duality). This line of thinking has brought a lot of clarity to string theory and to black hole physics.
panda-giddiness 6y ago
There's a long history of mathematicians working on general relativity; in fact, for decades general relativity was mostly the purview of mathematics, not physics, due to (1) the difficulty in finding exact solutions to the Einstein field equations and (2) their lack of physical meaning (eg, the Taub-NUT solution: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660007407.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/196600...).
gerdesj 6y ago
Assume a hyperbolic paraboloid cow ...
- thyrsus 6y ago
  Explanation of the joke: https://en.wikipedia.org/wiki/Spherical_cow https://en.wikipedia.org/wiki/Spherical_cow
philipov 6y ago
Roger Penrose is a Professor of Mathematics, not Physics. It's not unusual for mathematicians to also be theoretical physicists.
anonytrary 6y ago
> I find it mildly amusing that this work is being done by mathematicians rather than theoretical physicists. How so? This is very common. Math and theoretical physics are heavily interdisciplinary, and arguably the distinction between mathematicians and theoretical physicists is not as stark as most people would seem to think. At the highest caliber, the difference between a mathematician who works on physics and a theoretical physicist who works on math is a paper difference.

state_less 6y ago

Didn't Einstien use Minkowski's geometry for his key theories? Seems like it's helpful to have a few mathematicians involved in the project.

javajosh 6y ago
Not really my field, but I think Riemann had more of an impact on Einstein in that he was looking for a mathematical structure that fit his intuition about spacetime, and he dug up a 50-year old theory and applied it to GR. My understanding is that Einstein was searching for a long time for the right tool, and went down a lot of dead-end paths, before he discovered Riemann geometry.
- pmiller2 6y ago
  As I recall my history, it was actually believed that Einstein's first wife, Mileva Marić Einstein, who provided at least some of the mathematical muscle needed for GR [0]. --- [0]: https://blogs.scientificamerican.com/guest-blog/the-forgotten-life-of-einsteins-first-wife/ https://blogs.scientificamerican.com/guest-blog/the-forgotte...
  - qchris 6y ago
    I definitely agree he had a mathematician working with him to help, but am not sure it was his wife. I think that there's varying interpretations of her contributions to A. Einstein's work. If I'm remembering correctly, Walter Isaacson's Einstein biography tended towards says that she didn't truly contribute much to any of the work he did around that time, but that he did have a colleague or two formally trained in non-Euclidean geometries that he spent a lot of time working on GR with.
    - agonz253 6y ago
      It was Marcel Grossman who introduced him to Riemman's work: https://en.wikipedia.org/wiki/Marcel_Grossmann https://en.wikipedia.org/wiki/Marcel_Grossmann There is no evidence that his wife provided any of the "mathematical muscle needed for GR", nor is there reason to suspect that she would have been in a position to do so, since she was not a mathematician and had failed the undergraduate physics degree at the institute where she met Einstein (Einstein himself barely passed though). [0] https://www.springer.com/gp/book/9781402039997 https://www.springer.com/gp/book/9781402039997
    - pmiller2 6y ago
      > If I'm remembering correctly, Walter Isaacson's Einstein biography tended towards says that she didn't truly contribute much to any of the work he did around that time.... I'm not sure how much credence I'd put in such an assertion given that Einstein himself wrote in a letter to Mileva: > “When I read Helmholtz for the first time, it seemed so odd that you were not at my side and today, this is not getting better. I find the work we do together very good, healing and also easier.” Emphasis added by me. Having not read the book, Isaacson might have some additional evidence and insights I'm not aware of, but who knows?
      - agonz253 6y ago
        > “When I read Helmholtz for the first time, it seemed so odd that you were not at my side and today, this is not getting better. I find the work we do together very good, healing and also easier.” Note that this was written when they were both undergraduate students and would study together.
        pmiller2 6y ago
        There are other examples in the SA article I posted, including a letter from 1905 where Einstein talks about their "work on relative motion."
    - deleted 6y ago
      [deleted]
- webdva 6y ago
  Inspiring persistence.

godelski 6y ago

I don't find this surprising at all. Theoretical physicists are really just applied mathematicians. I don't know a physicist that would disagree with this. In fact, many said Einstein was more a mathematician than a physicist.

evanb 6y ago
Sort of. As a physicist I'd also say we have different sets of intuition, different willingnesses to play fast and loose or to make heuristic arguments (for a good example, consider the history of the Dirac delta function). Certainly physicists apply mathematics; does that make them applied mathematicians? I'm not certain. On the other hand, while I find these sorts of theorems nice results, they do not change one bit of my understanding.
paulpauper 6y ago
agree . the top theoretical physicists are effectively top mathematicians, too. Witten got a Fields Medal. you need to understanding algebraic geometry, topology, diff. geometry, diff. equations, numerical analysis, special functions, stats, etc. to be a top physicist. Pretty much everything is pure math.

piokoch 6y ago

I don't think theoretical physicists would find these findings to be that interesting. There are a lot of mathematical results that can be somehow applied to physics, but very rarely something interesting comes out of it from physicists perspective. Obviously when it happens, then it can lead to a breakthrough as it happened when Einstein figured out how Riemmann geometry can be applied to GR. The author himself is kind of uncertain if there are any real consequences comming out of his math: >>The instability of AdS space-time has major implications for how we understand our own universe. First, since AdS space-time is unstable, it’s “something you will not see in nature,” Moschidis said.<< >>But “even though AdS is not real,” he said, “it can still lead us to the discovery and study of real phenomena.” << I am not sure how our understanding of time-space can be increased by a theory that just does not describe reality. Maybe the math is somehow useful? Maybe this might explain what happened after Big Bang (maybe instabilities were more common then)? Maybe this is the path to unify QM and GR (in the article it is mentioned that, but with some usual addition of not yet observed additional dimension that can explain everything - the feature of many "string" theories", that didn't give us much.

andrewflnr 6y ago
It's definitely not the case that AdS being non-physical stops it from being useful in physics. ADS-CFT plays a big role in physics research today. I'm hoping that seeing how it breaks down will lead to clues about exactly where it diverges from the real world.
abdullahkhalids 6y ago
Theoretical physics has always studied theories that don't describe reality. It deepens our understanding of the theories that do describe reality. Eg., if you change one axiom of a reality-describing-theory and certain naturally occurring phenomena disappears, then you can say that that axioms causes that that phenomena to occur. Also, this is not my field, but thousands of physics papers have been written on the AdS geometry (particularly the AdS-CFT duality). This line of thinking has brought a lot of clarity to string theory and to black hole physics.

panda-giddiness 6y ago

There's a long history of mathematicians working on general relativity; in fact, for decades general relativity was mostly the purview of mathematics, not physics, due to (1) the difficulty in finding exact solutions to the Einstein field equations and (2) their lack of physical meaning (eg, the Taub-NUT solution: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660007407.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/196600...).

gerdesj 6y ago

Assume a hyperbolic paraboloid cow ...

thyrsus 6y ago
Explanation of the joke: https://en.wikipedia.org/wiki/Spherical_cow https://en.wikipedia.org/wiki/Spherical_cow

philipov 6y ago

Roger Penrose is a Professor of Mathematics, not Physics. It's not unusual for mathematicians to also be theoretical physicists.

anonytrary 6y ago

> I find it mildly amusing that this work is being done by mathematicians rather than theoretical physicists. How so? This is very common. Math and theoretical physics are heavily interdisciplinary, and arguably the distinction between mathematicians and theoretical physicists is not as stark as most people would seem to think. At the highest caliber, the difference between a mathematician who works on physics and a theoretical physicist who works on math is a paper difference.