The notion of complex-valued or even quaternionic or octonionic probabilities has been considered; see
http://physics.bu.edu/~youssef/quantum/quantum_refs.html for some pointers into the literature. -- Ben Goertzel > -----Original Message----- > From: scerir [mailto:[EMAIL PROTECTED] > Sent: Friday, January 23, 2004 9:23 AM > To: [EMAIL PROTECTED] > Subject: Re: probabilities & measures & computable universes > > > Are probabilities always and necessarily positive-definite? > > I'm asking this because there is a thread, started by Dirac > and Feynman, saying the only difference between the classical > and quantum cases is that in the former we assume the probabilities > are positive-definite. > > Thus, speaking of MWI, we could also ask: what is the joint > probability of finding ourselves in a universe alpha and of > finding ourselves in a universe beta, which is 180 degrees > out of phase with the first one (whatever that could mean)? > > s. > >
