Symmetries in the strong interactions: fact and fiction

Although only the weak interactions violate parity and time-reversal, there has been thought to be a possibility of some violation of both symmetries seeping into the strong interactions from the quark mass terms which are at the root of time-reversal violations in the weak interactions. None has been experimentally detected. Models have attempted to explain this absence of parity and time reversal violation, but their signatures have not been experimentally observed either. Fortunately we do not need non-standard models to understand the absence of parity and time-reversal violation in the strong interactions. Anyway they do not work.