3.6 CPT theorem

Theorem

(CPT theorem)

.

Any Lorentz invariant Lagrangian with a Hermitian

Hamiltonian should be invariant under the product of P, C and T.

We will not prove this. For details, one can read Streater and Wightman,

PCT, spin and statistics and all that (1989).

All observations we make suggest that CPT is respected in nature. This

means a particle propagating forwards in time cannot be distinguished from the

antiparticle propagating backwards in time.