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