4 ms·

This is the third formulation I've come across that sounds like this with space and time emerging from particle interactions. The other two are from Stephen Wol

This is the third formulation I've come across that sounds like this with space and time emerging from particle interactions. The other two are from Stephen Wolfram and Carlo Rovelli. Are the formulations related do you know? I've struggled to get beyond their popular science descriptions to the actual theories, I find descriptions like the amplituhedron being 'a multidimensional jewel' distracting, if you have any suggestions where to start for a deeper understanding of this one I'd be interested.

DebtDeflation 4y ago
Spacetime is emergent in both string theory and loop quantum gravity. Article contrasting how it works in each: https://www.scientificamerican.com/article/what-is-spacetime-really-made-of/ https://www.scientificamerican.com/article/what-is-spacetime...
danbruc 4y ago
You can find quite a few lectures by Nima Arkani-Hamed on YouTube including some on the amplituhedron. But they are mostly not gentle introductions and require some knowledge of physics to follow along. I think this one [1] provides a lot of background and explains the motivation. [1] https://www.youtube.com/watch?v=mF_vqDt-ETU https://www.youtube.com/watch?v=mF_vqDt-ETU
- philipov 4y ago
  I used to follow his lectures, but in the past 3 or 4 years he's become really quiet. I wonder if people stopped inviting him because he always overruns his time limit, or if he's too busy making progress on his theory.
Enginerrrd 4y ago
Sean Carrol has a great paper on this too showing emergent spacetime from entangled states in hilbert space: https://arxiv.org/abs/1606.08444 https://arxiv.org/abs/1606.08444 Here's a more conceptual introduction to that concept: https://web.stanford.edu/~oas/SI/QM/papers/SpaceFromQMCarroll.pdf https://web.stanford.edu/~oas/SI/QM/papers/SpaceFromQMCarrol...
philipov 4y ago
It's a common thing to see in theories that try to unify QM with GR because in GR spacetime is dynamic, while in QM it's static. For QM to produce GR, there needs to be some way of generating space and time instead of taking it as an assumption.
saboot 4y ago
The biggest clue we have right now is illustrated by last year's nobel prize. Particles in an entangled state can interact instantaneously, disregarding space and time entirely.
hughesjj 4y ago
Check out any lecture by Leonard Susskind on YouTube https://en.m.wikipedia.org/wiki/Leonard_Susskind https://en.m.wikipedia.org/wiki/Leonard_Susskind These are the coolest ideas ever and they literally relate to computational complexity and information theory. It's super cool. ER=EPR and [complexity=action](https://en.m.wikipedia.org/wiki/CA-duality https://en.m.wikipedia.org/wiki/CA-duality) especially imo
- TechBro8615 4y ago
  Be warned, I entered a similar rabbit hole about two years ago and have still not emerged from it.
- deleted 4y ago
  [deleted]
fartsucker69 4y ago
Until we get evidence of such a thing, those ideas have little credibility though they are nice thought experiments. What they're really seeing is that mathematically something can be expressed with less dimensions or degrees of freedom than what you observe in the real world, and then make the conclusion that therefor the dimensions and properties etc. that we observe are some emergent property and not fundamental. But you can't make this conclusion from the mathematical model. For example, if I have a finite sized two dimensional plane where each point is associated with some function f(x,y),you can trivially express it as a one dimensional system where all the rows of the plane are sort of unwound onto a single line. This trick does not work for infinite 2D spaces but there are other ways to remap infinite sized spaces onto finite ones (e.g. via tan). Yet there's nothing fundamental about this, it's just a mathematical modelling trick.
- ouid 4y ago
  this trick works for infinite sets of the same cardinality and in fact works continuously for the case you are describing. there is a surjective continuous function fron R to R^n for any n

DebtDeflation 4y ago

Spacetime is emergent in both string theory and loop quantum gravity. Article contrasting how it works in each: https://www.scientificamerican.com/article/what-is-spacetime-really-made-of/ https://www.scientificamerican.com/article/what-is-spacetime...

danbruc 4y ago

You can find quite a few lectures by Nima Arkani-Hamed on YouTube including some on the amplituhedron. But they are mostly not gentle introductions and require some knowledge of physics to follow along. I think this one [1] provides a lot of background and explains the motivation. [1] https://www.youtube.com/watch?v=mF_vqDt-ETU https://www.youtube.com/watch?v=mF_vqDt-ETU

philipov 4y ago
I used to follow his lectures, but in the past 3 or 4 years he's become really quiet. I wonder if people stopped inviting him because he always overruns his time limit, or if he's too busy making progress on his theory.

Enginerrrd 4y ago

Sean Carrol has a great paper on this too showing emergent spacetime from entangled states in hilbert space: https://arxiv.org/abs/1606.08444 https://arxiv.org/abs/1606.08444 Here's a more conceptual introduction to that concept: https://web.stanford.edu/~oas/SI/QM/papers/SpaceFromQMCarroll.pdf https://web.stanford.edu/~oas/SI/QM/papers/SpaceFromQMCarrol...

philipov 4y ago

It's a common thing to see in theories that try to unify QM with GR because in GR spacetime is dynamic, while in QM it's static. For QM to produce GR, there needs to be some way of generating space and time instead of taking it as an assumption.

saboot 4y ago

The biggest clue we have right now is illustrated by last year's nobel prize. Particles in an entangled state can interact instantaneously, disregarding space and time entirely.

hughesjj 4y ago

Check out any lecture by Leonard Susskind on YouTube https://en.m.wikipedia.org/wiki/Leonard_Susskind https://en.m.wikipedia.org/wiki/Leonard_Susskind These are the coolest ideas ever and they literally relate to computational complexity and information theory. It's super cool. ER=EPR and [complexity=action](https://en.m.wikipedia.org/wiki/CA-duality https://en.m.wikipedia.org/wiki/CA-duality) especially imo

TechBro8615 4y ago
Be warned, I entered a similar rabbit hole about two years ago and have still not emerged from it.
deleted 4y ago
[deleted]

fartsucker69 4y ago

Until we get evidence of such a thing, those ideas have little credibility though they are nice thought experiments. What they're really seeing is that mathematically something can be expressed with less dimensions or degrees of freedom than what you observe in the real world, and then make the conclusion that therefor the dimensions and properties etc. that we observe are some emergent property and not fundamental. But you can't make this conclusion from the mathematical model. For example, if I have a finite sized two dimensional plane where each point is associated with some function f(x,y),you can trivially express it as a one dimensional system where all the rows of the plane are sort of unwound onto a single line. This trick does not work for infinite 2D spaces but there are other ways to remap infinite sized spaces onto finite ones (e.g. via tan). Yet there's nothing fundamental about this, it's just a mathematical modelling trick.

ouid 4y ago
this trick works for infinite sets of the same cardinality and in fact works continuously for the case you are describing. there is a surjective continuous function fron R to R^n for any n