A CAUSAL CALCULUS (II)*

The radioactive process described in Axiom 23 can be slightly generalised by permitting return from the black to the white state, with a parameter p corresponding to the a of the white-to-black transition. We have a two-state Markov process with continuous time. The parameters a and fi are of course both non-negative. In the special case of the radioactive particle we have /9 = o. It can be shown that