unless you have a state where CP^2 = 1
How can it be anything else? Even then, T would equal (CP)^-1.
Generally, you pick up a phase factor after CP^2. The story is exactly like parity (P) if you can embed P^2 in a continuous symmetry, you can define away the phase factor, but if you can’t you are just stuck with it.
That’s still in the reference class I called “boring stuff”, though.
How can it be anything else? Even then, T would equal (CP)^-1.
Generally, you pick up a phase factor after CP^2. The story is exactly like parity (P) if you can embed P^2 in a continuous symmetry, you can define away the phase factor, but if you can’t you are just stuck with it.
That’s still in the reference class I called “boring stuff”, though.