9:19 AM
@MoreAnonymous there's a possibility that the confusion here is based around what a 'measurement' is or is not

1 hour later…
10:32 AM
@Mithrandir24601 "if one adheres to the view that the non-unitarity of measurement is an effective description of a unitary process in which some of the information is neglected, à la Zurek)" then isn't the measurement just another unitary process ... Hence the whole "But we use Heisenberg's equation to obtain the result! True. " can be removed as an objection?

@MoreAnonymous well, what is a measurement? If you define it as the unitary process before the information is 'neglected' (not entirely sure what this actually means, but anyway), then it's unitary. If you define it to include the 'information being neglected' then it's not

11:10 AM
@Mithrandir24601

"If you define it as the unitary process before the information is 'neglected' (not entirely sure what this actually means, but anyway)," ... I think by information your saying your able to say something definitive about the system say an eigenvalue from the states of the system??

"to include the 'information being neglected' then it's not" ... I'm guessing this is the essensce to way $3$ .. the measurement is a non-unitary operation. So maybe a better question to ask was what is Zurek achieving by trying to model "the non-unitarity of measurement is an effective descript
@Mithrandir24601 I was under the impression the information being neglected was the "apparatus"?

7 hours later…
5:48 PM