4 ms·

Perhaps "outside" means "resident on the boundary of", a la holograms and Maldecena's AdS/CFT work, and so still within reach of experiment?

codethief 2y ago
How is AdS/CFT (as it pertains to describing spacetime & the Standard Model) within reach of experiment? We're not even in an AdS universe.
- hughesjj 2y ago
  I was going to write something up but honestly the top two answers in this physics stack exchange do it more competently and comprehensively than I'm able https://physics.stackexchange.com/questions/122540/why-are-anti-de-sitter-spaces-so-interesting-when-we-believe-the-universe-is-exp https://physics.stackexchange.com/questions/122540/why-are-a... My takeaway/summary is 'AdS/CFT let's you temporarily change your space/model to make the math easier and then map it back into the original model. Although we don't currently have such a model specified for our particular observed universe, it still allows us to study functionality equivalent behavior and make some determinations over what is/isn't/could be possible'
  - codethief 2y ago
    From the link you posted: > Ok, so if I understand correctly, AdS spaces aren't meant to directly model the universe, but rather are used as a tool to make certain calculations in CFT easier? GP's comment was modelling the universe as AdS/CFT, though, which is why my question addressed precisely that part: > How is AdS/CFT (as it pertains to describing spacetime & the Standard Model)
    - jungturk 2y ago
      Sorry, my point was to (almost facetiously) interject the topological concept of "boundary/bulk" correspondence (as also exists with holograms & AdS/CFT) rather than suggesting the correctness of AdS/CFT. The idea that "outside" becomes available via a change in perspective from boundary to bulk.
austinjp 2y ago
For those who, like me, are not familiar with AdS/CFT, it's "anti-de Sitter/conformal field theory correspondence" which is "a conjectured relationship between two kinds of physical theories", allowing quantum field theories to be made more mathematically tractable. https://en.m.wikipedia.org/wiki/AdS/CFT_correspondence https://en.m.wikipedia.org/wiki/AdS/CFT_correspondence

codethief 2y ago

How is AdS/CFT (as it pertains to describing spacetime & the Standard Model) within reach of experiment? We're not even in an AdS universe.

hughesjj 2y ago
I was going to write something up but honestly the top two answers in this physics stack exchange do it more competently and comprehensively than I'm able https://physics.stackexchange.com/questions/122540/why-are-anti-de-sitter-spaces-so-interesting-when-we-believe-the-universe-is-exp https://physics.stackexchange.com/questions/122540/why-are-a... My takeaway/summary is 'AdS/CFT let's you temporarily change your space/model to make the math easier and then map it back into the original model. Although we don't currently have such a model specified for our particular observed universe, it still allows us to study functionality equivalent behavior and make some determinations over what is/isn't/could be possible'
- codethief 2y ago
  From the link you posted: > Ok, so if I understand correctly, AdS spaces aren't meant to directly model the universe, but rather are used as a tool to make certain calculations in CFT easier? GP's comment was modelling the universe as AdS/CFT, though, which is why my question addressed precisely that part: > How is AdS/CFT (as it pertains to describing spacetime & the Standard Model)
  - jungturk 2y ago
    Sorry, my point was to (almost facetiously) interject the topological concept of "boundary/bulk" correspondence (as also exists with holograms & AdS/CFT) rather than suggesting the correctness of AdS/CFT. The idea that "outside" becomes available via a change in perspective from boundary to bulk.

austinjp 2y ago

For those who, like me, are not familiar with AdS/CFT, it's "anti-de Sitter/conformal field theory correspondence" which is "a conjectured relationship between two kinds of physical theories", allowing quantum field theories to be made more mathematically tractable. https://en.m.wikipedia.org/wiki/AdS/CFT_correspondence https://en.m.wikipedia.org/wiki/AdS/CFT_correspondence