CPT and strings

Abstract We define the string space-time symmetries C,P,T and their products. The effects of nonlocal interactions and the infinite number of particle fields are incorporated using string field theory. At the dynamical level, C,P,T and their products are preserved by the open bosonic string. Only the product CPT is dynamically preserved by the superstring, although a modified action can be constructed to preserve C. We show that these discrete symmetries may be spontaneously broken in a natural way by string interactions. In a favorable scenario, this might lead to CPT violation in the K-K system just below the limits of present experiments.