> There is a growing consensus in theoretical physics that spacetime is not a primitive notion
That’s a very strong statement. I’m not sure what the actual distribution of views on spacetime is, but there certainly isn’t a consensus on that matter. If I wanted to establish credibility, I wouldn’t open a paper with such a dubious claim.
Second, Pauli matrices are highly relevant to space (see: Dirac spinors; but also, they can be used for quaternions—i.e., rotations in 3D). Using Pauli matrices to argue that we live in a 1+3 spacetime feels, at the very least, like a circular argument.
The idea that spacetime is emergent and not fundamental dates back to the 60s and has seen some pretty neat stuff along the way, like Bekenstein and Hawking discussing information problems in the 70s that hinted at a deep connection between gravity and thermodynamics. Then in the 90s we had Jacobson deriving General Relativity from the first law of thermodynamics and in the 2000s we had Verlinde combining this with holography. It's not a "solved" problem by any stretch, but some of the greatest physicists of their generation have meddled with this and I think there are almost none left who would refute the basic idea. It's the details that people are still arguing about - which now include this paper.
There are quite a few ideas! Myself, I would bet on Polymarket that there is something more fundamental than curved 1+3 spacetime.
Some are, as you said, in thermodynamics. In the String Theory, 1+3 is a somewhat reduced space from original 26 dimensions or so. (This "somewhat" is the core issue.)
So sure, "The idea that spacetime is emergent and not fundamental dates back to the 60s" would work as an awesome opening of the paper.
The "growing consensus" bit literally alludes to all these developments. But granted, you have to be versed in the field to understand this. On the other hand, this is a research paper. It is not written for laypeople.
"Growing consensus" is not the same thing as consensus. If currently 20% of the top physicists think spacetime is not a primitive notion and this number has monotonically increased by 1% every year for the past decade, that would be an example of "growing consensus".
Besides, Vlatko Vedral is a top theorist in the area, who talks other top theorists at conferences and workshops. He wouldn't say this if he didn't think other top theorists didn't agree with him.
Weasel words (or other common sense statements said passed as objective truths) should not be a part a scientific paper, regardless of who is writing that (yes, I know that Vlatko Vedral is an established researcher).
Myself, I am quantum physicist by training. While I have certain views on stuff (e.g. many-world interpretation and decoherence, in the line of ZH Zurek), I actually cite surveys on the view on physicist on QM interpretation. (Even though I "know" from my personal observations that all almost all theoretical physicists are in the MWI.)
> If currently 20% of the top physicists think spacetime is not a primitive notion and this number has monotonically increased by 1% every year for the past decade, that would be an example of "growing consensus".
Awesome! Then any reference with such data would be useful. If one cannot make (or even create a personal survey), then one should not write such things as facts.
I don't think the Pauli matrices are used per se I think they are derived from the anti-commutation criteria of the basis elements. I don't know what justifies that criteria though.
I just watched a brief talk[1] over at Pirsa about the emergence of Lorentzian signature and time dimension from quantum fluctuations.
As I understood it, starting with a uniform 4D metric, and then introducing a certain amount of asymmetrical "noise" to the background field through particle coupling, one of the dimensions got an effective sign flip in the metric leading to spacetime metric signature we know and love.
Just a layman so can't comment on the details, but sounded interesting.
My understanding is limited, but this seems pretty interesting. I'm not quite sure I follow the argument that space is a correlated interaction at the quantum level.
As a total tangent: it would be interesting to have an LLM-based modality, like a browser extension, where a user could highlight academic concepts in a pdf and drill down. Academic writing, by convention and necessity, is terse and references prior literature, sometimes opaquely. So getting up to speed in the literature takes significant effort.
> the spin matrices were built to deal with three spatial axes
If I understand correctly, it kinda happened the other way around. First the Pauli matrices were introduced to explain unexpected degrees of freedom in experimental observations; then the term "spin" was proposed because the operators related to each other in the same way as classical angular momentum operators. See e.g. https://www.sciencedirect.com/science/article/abs/pii/S13552...
Not in this field directly, but first of all, talking about the "geometry of space" is more than just saying there are three spatial dimensions: geometry involves the local curvature of the object. Historically the Pauli matrices are discovered by assuming certain symmetries of spacetime. This paper shows the other direction also makes sense: if we assume certain structure on quantum observables, measurable only by temporal measurements and independent of the content of the quantum state (i.e., a measurement of any system will do), we can get the spatial symmetries we want.
I suppose the ideal outcome is that there is some sort of exotic algebra of observables which is well motivated somehow by purely quantum considerations and by serendipity induces all the usual spacetime symmetries + extra stuff we didn't know about. This paper itself is cute but not sure if it's very impactful, I would defer to domain experts.
Jaeger et al.’s ideas on consciousness is in which many “baked in” structures are emergent, and that living or "cognitive systems" similarly generate meaning from underlying complexity without being reducible to a straightforward set of rules. Macro level “givens” (geometry) can arise from deep nonclassical processes. “procedurally generated quantum reality” or something.
Can't assess content beyond amateur attempt, but am curious.
Second author seems very established, so some social proof there: https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=Geom...
EDIT: yesterday's video on the paper by Sabine Hossenfelder: https://www.youtube.com/watch?v=7See8OhtN-k (h/t user naasking below)
From a skim, I'd summarize the paper thus:
"product of (exponentiated) Paulis can be shown to have 2 eigenvalues"
(& Let anyone who disagrees try to argue that quaternions aren't the best way to think about classical rotation)
Well, it feels shaky. First, it starts with:
> There is a growing consensus in theoretical physics that spacetime is not a primitive notion
That’s a very strong statement. I’m not sure what the actual distribution of views on spacetime is, but there certainly isn’t a consensus on that matter. If I wanted to establish credibility, I wouldn’t open a paper with such a dubious claim.
Second, Pauli matrices are highly relevant to space (see: Dirac spinors; but also, they can be used for quaternions—i.e., rotations in 3D). Using Pauli matrices to argue that we live in a 1+3 spacetime feels, at the very least, like a circular argument.
The idea that spacetime is emergent and not fundamental dates back to the 60s and has seen some pretty neat stuff along the way, like Bekenstein and Hawking discussing information problems in the 70s that hinted at a deep connection between gravity and thermodynamics. Then in the 90s we had Jacobson deriving General Relativity from the first law of thermodynamics and in the 2000s we had Verlinde combining this with holography. It's not a "solved" problem by any stretch, but some of the greatest physicists of their generation have meddled with this and I think there are almost none left who would refute the basic idea. It's the details that people are still arguing about - which now include this paper.
There are quite a few ideas! Myself, I would bet on Polymarket that there is something more fundamental than curved 1+3 spacetime.
Some are, as you said, in thermodynamics. In the String Theory, 1+3 is a somewhat reduced space from original 26 dimensions or so. (This "somewhat" is the core issue.)
So sure, "The idea that spacetime is emergent and not fundamental dates back to the 60s" would work as an awesome opening of the paper.
The "growing consensus" bit literally alludes to all these developments. But granted, you have to be versed in the field to understand this. On the other hand, this is a research paper. It is not written for laypeople.
I don’t think anything is fundamental given that there is always something that is made of that something.
"Growing consensus" is not the same thing as consensus. If currently 20% of the top physicists think spacetime is not a primitive notion and this number has monotonically increased by 1% every year for the past decade, that would be an example of "growing consensus".
Besides, Vlatko Vedral is a top theorist in the area, who talks other top theorists at conferences and workshops. He wouldn't say this if he didn't think other top theorists didn't agree with him.
Weasel words (or other common sense statements said passed as objective truths) should not be a part a scientific paper, regardless of who is writing that (yes, I know that Vlatko Vedral is an established researcher).
Myself, I am quantum physicist by training. While I have certain views on stuff (e.g. many-world interpretation and decoherence, in the line of ZH Zurek), I actually cite surveys on the view on physicist on QM interpretation. (Even though I "know" from my personal observations that all almost all theoretical physicists are in the MWI.)
> If currently 20% of the top physicists think spacetime is not a primitive notion and this number has monotonically increased by 1% every year for the past decade, that would be an example of "growing consensus".
Awesome! Then any reference with such data would be useful. If one cannot make (or even create a personal survey), then one should not write such things as facts.
I don't think the Pauli matrices are used per se I think they are derived from the anti-commutation criteria of the basis elements. I don't know what justifies that criteria though.
ianap
No this has been a talking point by top spacetime theorists for a very long time. E.g. https://www.cornell.edu/video/nima-arkani-hamed-spacetime-is...
[dead]
I just watched a brief talk[1] over at Pirsa about the emergence of Lorentzian signature and time dimension from quantum fluctuations.
As I understood it, starting with a uniform 4D metric, and then introducing a certain amount of asymmetrical "noise" to the background field through particle coupling, one of the dimensions got an effective sign flip in the metric leading to spacetime metric signature we know and love.
Just a layman so can't comment on the details, but sounded interesting.
[1]: https://doi.org/10.48660/25060082
A recent Vedral (one of the authors) talk -
Decoding quantum reality - with Vlatko Vedral @ The Royal Institution (4-Mar-2025; 59:26)
https://youtu.be/70FhS6NAbuA
(I mostly watch while reading the running transcript these days - https://www.appblit.com/scribe?v=70FhS6NAbuA)
As a side note, The Royal Institution is one of the best youtube channels around, cannot recommend it enough, they do a great job with their playlists: https://www.youtube.com/@TheRoyalInstitution/playlists - Also recommend World Science Festival: https://www.youtube.com/@WorldScienceFestival/playlists
excellent playlists - thanks!
My understanding is limited, but this seems pretty interesting. I'm not quite sure I follow the argument that space is a correlated interaction at the quantum level.
As a total tangent: it would be interesting to have an LLM-based modality, like a browser extension, where a user could highlight academic concepts in a pdf and drill down. Academic writing, by convention and necessity, is terse and references prior literature, sometimes opaquely. So getting up to speed in the literature takes significant effort.
emergentmind is a great llm wrapper / search for scholar articles
semanticscholar does this!
You can do it with todays LLMs. First describe your level (how much math, etc you know) then ask it to explain a concept. Then ask further questions.
Yep. That's why I said I would love it as a browser extension.
Any physicist willing to comment? Sure, the spin matrices were built to deal with three spatial axes. Is there more to the paper than that?
> the spin matrices were built to deal with three spatial axes
If I understand correctly, it kinda happened the other way around. First the Pauli matrices were introduced to explain unexpected degrees of freedom in experimental observations; then the term "spin" was proposed because the operators related to each other in the same way as classical angular momentum operators. See e.g. https://www.sciencedirect.com/science/article/abs/pii/S13552...
Not in this field directly, but first of all, talking about the "geometry of space" is more than just saying there are three spatial dimensions: geometry involves the local curvature of the object. Historically the Pauli matrices are discovered by assuming certain symmetries of spacetime. This paper shows the other direction also makes sense: if we assume certain structure on quantum observables, measurable only by temporal measurements and independent of the content of the quantum state (i.e., a measurement of any system will do), we can get the spatial symmetries we want.
I suppose the ideal outcome is that there is some sort of exotic algebra of observables which is well motivated somehow by purely quantum considerations and by serendipity induces all the usual spacetime symmetries + extra stuff we didn't know about. This paper itself is cute but not sure if it's very impactful, I would defer to domain experts.
Hossenfelder actually did a video on this just yesterday:
https://www.youtube.com/watch?v=7See8OhtN-k
There was a long paper on HN recently that I've been stuck thinking about.
https://news.ycombinator.com/item?id=43990843
Jaeger et al.’s ideas on consciousness is in which many “baked in” structures are emergent, and that living or "cognitive systems" similarly generate meaning from underlying complexity without being reducible to a straightforward set of rules. Macro level “givens” (geometry) can arise from deep nonclassical processes. “procedurally generated quantum reality” or something.