I have heard that the instanton effect in quark matter causes the di-quark condensate to be Lorentz scalar. As opposed to the Lorentz scalar, there are possibilities that the condensates are Lorentz pseudoscalars, Lorentz vectors, Lorentz pseudovectors, or Lorentz tensors. It could also possibly break the Lorentz symmetry.
So what is the physical intuition or math reasoning behind that instanton effect favor Lorentz scalar, but does not favor (pseudoscalars) that breaks parity $P$? How about other cases?
This post imported from StackExchange Physics at 2020-10-29 11:44 (UTC), posted by SE-user annie marie heart