3 ms·

I assume that if we ever unify QCD with General Relativity, the resulting theory would be able to predict these hadrons from first principles?

deleted 2y ago
[deleted]
ur-whale 2y ago
> the resulting theory would be able to predict these hadrons from first principles? Not sure how bringing GR into the fray would help solve what essentially seems to be a computational complexity problem. Might actually make things worse.
- whatshisface 2y ago
  It's not a computational complexity problem, it's an undefinedness problem. Proving that the lattice simulations converge has been estimated as well beyond this century's mathematics by the pair of people (Glimm and Jaffe) that have done the most to study it. In any case it is beyond today's.
frutiger 2y ago
No. The reason perturbation theory doesn’t work as well for QCD as it does for QED is because of two reasons: 1. The coupling constant of QCD is much higher than QED so contributions to the overall result from Feynman diagrams that have more vertices (the multiplicative factor of each element in the sum is proportional to the power of the number of vertices) don’t vanish as quickly as they do for QED 2. The gauge bosons in QCD (i.e. gluons) themselves have colour charge whereas those in QED (i.e. photons) do not have electrical charge.
- whatshisface 2y ago
  You can't give a definite no to that because, since gravitons have stress-energy and are non-perturbative, a field theory advance that worked for them could also help with the strong force.
  - frutiger 2y ago
    I mean sure, since we don't know what GR + QFT could look like, the result could be just about anything and somehow give us nice closed solutions to QCD problems. But I don't feel like that line of reasoning is particularly useful.
    - whatshisface 2y ago
      AdS/CFT is already an example of an approach to gravity yielding an approach to strongly coupled field theories.
      - l33tman 2y ago
        It's an approach to a hypothetical other type of universe's gravity..

deleted 2y ago

[deleted]

ur-whale 2y ago

> the resulting theory would be able to predict these hadrons from first principles? Not sure how bringing GR into the fray would help solve what essentially seems to be a computational complexity problem. Might actually make things worse.

whatshisface 2y ago
It's not a computational complexity problem, it's an undefinedness problem. Proving that the lattice simulations converge has been estimated as well beyond this century's mathematics by the pair of people (Glimm and Jaffe) that have done the most to study it. In any case it is beyond today's.

frutiger 2y ago

No. The reason perturbation theory doesn’t work as well for QCD as it does for QED is because of two reasons: 1. The coupling constant of QCD is much higher than QED so contributions to the overall result from Feynman diagrams that have more vertices (the multiplicative factor of each element in the sum is proportional to the power of the number of vertices) don’t vanish as quickly as they do for QED 2. The gauge bosons in QCD (i.e. gluons) themselves have colour charge whereas those in QED (i.e. photons) do not have electrical charge.

whatshisface 2y ago
You can't give a definite no to that because, since gravitons have stress-energy and are non-perturbative, a field theory advance that worked for them could also help with the strong force.
- frutiger 2y ago
  I mean sure, since we don't know what GR + QFT could look like, the result could be just about anything and somehow give us nice closed solutions to QCD problems. But I don't feel like that line of reasoning is particularly useful.
  - whatshisface 2y ago
    AdS/CFT is already an example of an approach to gravity yielding an approach to strongly coupled field theories.
    - l33tman 2y ago
      It's an approach to a hypothetical other type of universe's gravity..