4 ms·

I'm not an expert in GR, but the linked paper seems nonsensical[0]. It postulates a highly degenerate decomposition of the metric tensor, for which they postula

by kmm 5y ago

I'm not an expert in GR, but the linked paper seems nonsensical[0]. It postulates a highly degenerate decomposition of the metric tensor, for which they postulate a contrived action which then seems to correspond to the Einstein-Hilbert, through mathematically unsound manipulations (how can you raise indices with the metric being nowhere even close to invertible?). Besides, how can you talk about unifying general relativity and electromagnetism without mentioning Kaluza-Klein theory[1]? And what about one of the most beautiful principles in physics, gauge invariance[2]? I don't want to be rude, but I'm very curious as to how this got through peer review. 0: https://iopscience.iop.org/article/10.1088/1742-6596/1956/1/012017 https://iopscience.iop.org/article/10.1088/1742-6596/1956/1/... 1: https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory 2: https://en.wikipedia.org/wiki/Gauge_theory https://en.wikipedia.org/wiki/Gauge_theory

lamontcg 5y ago
Yeah first thought that popped into my head was Kaluza-Klein theory, and I'm far from an expert enough to dissect the paper but it has that smell of junk science.
codethief 5y ago
> Besides, how can you talk about unifying general relativity and electromagnetism without mentioning Kaluza-Klein theory[1]? No offense but the very first paragraph of the article's introduction mentions Kaluza's work: > The earliest attempts can be reasonably traced back to the German physicist Gustav Mie (1868-1957) and the Finnish physicist Gunnar Nordström (1881-1923). Fruitful efforts came, for example, from David Hilbert (1862-1943), Hermann Weyl (1885-1955), Theodor Kaluza (1885-1954), Arthur Eddington (1882-1944) and of course also from Albert Einstein (1879-1955). It is less well-known that, for example, Erwin Schrödinger (1887-1961) had such inclinations as well, see [1]. For a thorough historical review, see [2].
onhn 5y ago
Are you sure it was peer reviewed at all? It looks like a conference proceedings.
- kmm 5y ago
  According to this https://iopscience.iop.org/article/10.1088/1742-6596/1943/1/011002 https://iopscience.iop.org/article/10.1088/1742-6596/1943/1/... they're all peer-reviewed. An average number of reviews per paper of 1 seem a bit curious though.
  - piannucci 5y ago
    Assuming that every paper is reviewed at least once, Markov’s inequality implies that every paper is reviewed exactly once!
  - unishark 5y ago
    I think this is the declaration for the volume containing the conference in question? https://iopscience.iop.org/article/10.1088/1742-6596/1956/1/011002/meta https://iopscience.iop.org/article/10.1088/1742-6596/1956/1/... Higher acceptance rate, but more reviewers per paper.
goldenkey 5y ago
Kaluza's work is mentioned in the first paragraph of the paper. How can you write such an inflammatory critique without having actually read the paper?
- kmm 5y ago
  Kaluza's name is mentioned, but not Klein's, and there's no mention of their theory whatsoever. Kaluza-Klein theory is the archetype of expressing electromagnetism purely through curvature, and I'd expect any paper doing the same to refer to it, as well as explain how the work in the paper differs from or expands on it. The fact that the metric proposed in the paper corresponds to the term added to the 4D spacetime part of the Kaluza-Klein metric is already suspicious. It makes me think they're either repeating Kaluza and Klein's work, or aren't properly citing it when they should have.
  - makeitdouble 5y ago
    I have never been in academia and this is the first time it clicked to me that citing a paper is not just an act of mentioning it as a networking artefact, and should be critical to the substance. Thanks for the explanation.
  - codethief 5y ago
    > I'd expect any paper doing the same to refer to it, as well as explain how the work in the paper differs from or expands on it. But they do: > The strength of the present approach is simplicity, there is no need for higher dimensions, torsion tensors, asymmetric metrics or the like. (emphasis mine) > The fact that the metric proposed in the paper corresponds to the term added to the 4D spacetime part of the Kaluza-Klein metric is already suspicious. Why? There aren't many ways to write down a symmetric 2-tensor starting with a vector field. > It makes me think they're either repeating Kaluza and Klein's work, or aren't properly citing it when they should have. They're doing neither. Sure, they might have mentioned Kaluza's work more explicitly (AFAIK Klein's contribution was the suggestion to compatify the 5th dimension) but I suppose 1) they assumed that readers are familiar with it and 2) they wanted to mention several approaches to marry GR and ED and Kaluza's approach was just one of them.
piannucci 5y ago
Yeah, I think so too. While the authors might attempt to counter that they are only describing EM in vacuum, the fact is that GR is nonlinear. You can’t just add an EM sector by a rank-1 metric component and expect linearity to apply. At some level, this feels like a vacuous result. If you start with a rank-2 massless field theory, and constrain it to act on rank-1 fields, is it surprising that you get a rank-1 massless field theory? Is this not just an elaborate form of completing the square?

by kmm 5y ago

lamontcg 5y ago

Yeah first thought that popped into my head was Kaluza-Klein theory, and I'm far from an expert enough to dissect the paper but it has that smell of junk science.

codethief 5y ago

> Besides, how can you talk about unifying general relativity and electromagnetism without mentioning Kaluza-Klein theory[1]? No offense but the very first paragraph of the article's introduction mentions Kaluza's work: > The earliest attempts can be reasonably traced back to the German physicist Gustav Mie (1868-1957) and the Finnish physicist Gunnar Nordström (1881-1923). Fruitful efforts came, for example, from David Hilbert (1862-1943), Hermann Weyl (1885-1955), Theodor Kaluza (1885-1954), Arthur Eddington (1882-1944) and of course also from Albert Einstein (1879-1955). It is less well-known that, for example, Erwin Schrödinger (1887-1961) had such inclinations as well, see [1]. For a thorough historical review, see [2].

onhn 5y ago

Are you sure it was peer reviewed at all? It looks like a conference proceedings.

kmm 5y ago
According to this https://iopscience.iop.org/article/10.1088/1742-6596/1943/1/011002 https://iopscience.iop.org/article/10.1088/1742-6596/1943/1/... they're all peer-reviewed. An average number of reviews per paper of 1 seem a bit curious though.
- piannucci 5y ago
  Assuming that every paper is reviewed at least once, Markov’s inequality implies that every paper is reviewed exactly once!
- unishark 5y ago
  I think this is the declaration for the volume containing the conference in question? https://iopscience.iop.org/article/10.1088/1742-6596/1956/1/011002/meta https://iopscience.iop.org/article/10.1088/1742-6596/1956/1/... Higher acceptance rate, but more reviewers per paper.

goldenkey 5y ago

Kaluza's work is mentioned in the first paragraph of the paper. How can you write such an inflammatory critique without having actually read the paper?

kmm 5y ago
Kaluza's name is mentioned, but not Klein's, and there's no mention of their theory whatsoever. Kaluza-Klein theory is the archetype of expressing electromagnetism purely through curvature, and I'd expect any paper doing the same to refer to it, as well as explain how the work in the paper differs from or expands on it. The fact that the metric proposed in the paper corresponds to the term added to the 4D spacetime part of the Kaluza-Klein metric is already suspicious. It makes me think they're either repeating Kaluza and Klein's work, or aren't properly citing it when they should have.
- makeitdouble 5y ago
  I have never been in academia and this is the first time it clicked to me that citing a paper is not just an act of mentioning it as a networking artefact, and should be critical to the substance. Thanks for the explanation.
- codethief 5y ago
  > I'd expect any paper doing the same to refer to it, as well as explain how the work in the paper differs from or expands on it. But they do: > The strength of the present approach is simplicity, there is no need for higher dimensions, torsion tensors, asymmetric metrics or the like. (emphasis mine) > The fact that the metric proposed in the paper corresponds to the term added to the 4D spacetime part of the Kaluza-Klein metric is already suspicious. Why? There aren't many ways to write down a symmetric 2-tensor starting with a vector field. > It makes me think they're either repeating Kaluza and Klein's work, or aren't properly citing it when they should have. They're doing neither. Sure, they might have mentioned Kaluza's work more explicitly (AFAIK Klein's contribution was the suggestion to compatify the 5th dimension) but I suppose 1) they assumed that readers are familiar with it and 2) they wanted to mention several approaches to marry GR and ED and Kaluza's approach was just one of them.

piannucci 5y ago

Yeah, I think so too. While the authors might attempt to counter that they are only describing EM in vacuum, the fact is that GR is nonlinear. You can’t just add an EM sector by a rank-1 metric component and expect linearity to apply. At some level, this feels like a vacuous result. If you start with a rank-2 massless field theory, and constrain it to act on rank-1 fields, is it surprising that you get a rank-1 massless field theory? Is this not just an elaborate form of completing the square?