Heinera wrote:Gordon Watson wrote:.
It might help us all if you could each provide your definition of an RV. And in the context of Bell's work, if you think it there differs from the definition used in probability and statistics.
PS: I use λ in FUNCTIONS: eg, A(a,λ).
Thanks; Gordon
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There is already a thread for that topic, and to be honest I don't see that there has been any resolution of the matter in that thread.
But Bell's argument goes through even without the assumption that lambda is a random variable, so I agree with you that there is not much point in explicitly assuming it is random in the context of Bell's theorem.
In Bell's argument, lambda is an element of a set Lambda, and the probability that it lies in any particular subset of Lambda is the integral over that subset of rho(lambda) d lambda. We think of nature picking a value lambda at random from the set Lambda. After that, everything is deterministic. If the experimenter has chosen to use setting a in Alice's wing of the experiment and b in Bob's, then the outcomes they get to see are A(a, lambda) and B(b, lambda). A and B are fixed functions which take values +/-1.
One can rewrite and generalise this in the language of conventional probability theory. Just rename lambda as omega, Lambda as Omega. Let A_a be the random variable (a function of omega) A(a, . ), taking values in +/-1. Instead of assuming a probability density rho we would assume a probability measure P. Instead of writing integral ... rho(lambda) d lambda we would write integral ... d P(omega). We could also drop the "omega" everywhere and write E(A_a B_b) or if you prefer integral_Omega (A_a B_b) d P instead of integral .... rho(lambda) d lambda. The usual rules stay valid. The same proof goes through. It's completely elementary.
Christian's original idea was that he would let A_a and B_b take values in a different larger space, but one which does still contain elements called -1 and +1, satisfying the usual rules, and actually A_a and B_b did only take those two particular values. This cannot change anything! The reason he got a result violating Bell's inequality was by hiding a sign error in his geometric algebra, where nobody would see it, because almost nobody knows enough geometric algebra to check the details. But of course that was unnecessary.
Later he decided to use other and more complicated tricks. You could say there was Christian 1.0, then Christian 2.0, and finally Christian 3.0.