Robin: is there a paper somewhere that elaborates this argument from mixed-state ambiguity?
Scott should add his own recommendations, but I would say here is a good starting introduction.
To my mind, the fact that two different situations of uncertainty over true states lead to the same physical predictions isn’t obviously a reason to reject that type of view regarding what is real.
The anti-MWI position here is that MWI produces different predictions depending on what basis is arbitrarily picked by the predictor; and that the various MWI efforts to “patch” this problem without postulating a new law of physics, are like squaring the circle. I think the anti-MWI’ers math is correct, but I’m not an expert enough to be 100% sure; what really makes me think MWI is wrong is the inability of the MWI’ers, after many decades, to produce an algorithm that you can “turn the crank” on to get the correct probabilities that we see in experiments; they have the tendency of trying to patch this “basis problem” by producing a new framework, which itself contains an arbitrary choice that’s just as bad as the arbitrary choice of basis.
More succinctly, in vanilla MWI you have to pick the correct basis to get the correct experimental results, and you have to peek at the results to get the correct basis.
Robin: is there a paper somewhere that elaborates this argument from mixed-state ambiguity?
Scott should add his own recommendations, but I would say here is a good starting introduction.
To my mind, the fact that two different situations of uncertainty over true states lead to the same physical predictions isn’t obviously a reason to reject that type of view regarding what is real.
The anti-MWI position here is that MWI produces different predictions depending on what basis is arbitrarily picked by the predictor; and that the various MWI efforts to “patch” this problem without postulating a new law of physics, are like squaring the circle. I think the anti-MWI’ers math is correct, but I’m not an expert enough to be 100% sure; what really makes me think MWI is wrong is the inability of the MWI’ers, after many decades, to produce an algorithm that you can “turn the crank” on to get the correct probabilities that we see in experiments; they have the tendency of trying to patch this “basis problem” by producing a new framework, which itself contains an arbitrary choice that’s just as bad as the arbitrary choice of basis.
More succinctly, in vanilla MWI you have to pick the correct basis to get the correct experimental results, and you have to peek at the results to get the correct basis.