# Re: Hitch

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On 12 Jul 2013, at 19:18, meekerdb wrote:```
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```On 7/12/2013 2:11 AM, Bruno Marchal wrote:
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On 11 Jul 2013, at 22:14, meekerdb wrote:

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```On 7/11/2013 12:34 PM, Bruno Marchal wrote:
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On 11 Jul 2013, at 18:46, meekerdb wrote:

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```On 7/10/2013 11:25 PM, Bruno Marchal wrote:
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I have given the equation. I try to explain this on FOAR but it relies on some familiarity in logic. Normally you should know already that physics is given by a measure on relative computational continuations, and the logic explains already the statistical interferences.
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QM is deterministic and there is only one 'computational continuation';
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If you measure up+down in the base {up,down}, you get two computational continuation, unless you add a non deterministic collapse.
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No, you only get one in which the measuring device state (including you) is entangled with the system measured.
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you * (up + down) = (you * up)  +  (you * down),

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That is a deterministic bifurcation leading to two (at least) computational continuations, one where you see the electron in the up state and one in which you see the electron in the down state.
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But it is not a bifurcation because it can be undone by subsequent evolution of the wave function;
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OK.

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```which means there is only one computational continuation.
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From the 3p view only.

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It is only if you assume collapse of the wave function that the evolution cannot be reversed and that is what decoherence attempts to explain in terms of diffusing information into the environment. But a fundamental theory of everything has no "environment".
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Indeed. But we don't need the collapse, we need only that the persons in question does not erase their memory. It is exactly like with the FPI. The W and M persons can still fuse, if they forget which city they are in.
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That's what "entangle" means in QM without collapse.

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To get two you have to treat "measurement" as some non-unitary operator.
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Not at all, I can also use the FPI. The measurement becomes a machine interaction followed by self-reference/personal memory access.
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But here you deviate from QM and treat the individual consciousness as something that can irreversibly bifurcate. It is essentially Wigner's initial theory that consciousness collapses the wave function. The only difference is you suppose both branches to exist.
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If you interpret Wigner in that way, you are right. But keeping the branches makes the process reversible, and the 3p picture deterministic.
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That's the puzzle that Everett addressed by throwing out the collapse postulate and assuming only one kind of continuation. Since that seemed like an attractive idea the problem has become how to explain the experience of one thing happening and another not.
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It is solved completely by the FPI. We experience one thing and not the other for the same comp reason why we see only W (or only M) in the WM duplication.
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What is that reason? According to QM there are two systems that are entangled with environments such that they are statistically unlikely to recohere and hence form persistently different memories.
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Like the W-person and the M-person. Fusing remains possible, even reversibly, by dissociating or discarding memories, of course this needs perfect isolation of those memories from the environment.
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That is why Everett can use comp and remains in a purely deterministic framework. The only problem is that Everett did not discovered explicitly the FPI,
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He explicitly postulated it of observers in QM.
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Yes, that is what I say. He could have derived if from comp directly.

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which occurs also in arithmetic, which would have forced him to understand that the wave itself must be phenomenologically derived from a measure on all computations, and not one circumscribe to any special universal machine (like the quantum one).
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I don't see how reference to a "quantum machine" is relevant. QM is just a theory and in fact just a schema for theories; you need the specify the Hilbert space and the Hamiltonian before you actually have a theory.
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Hamiltonians provide just different models (realities) instantiating the QM basic axioms. A theory is just a set of axioms and rules.
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Bruno

http://iridia.ulb.ac.be/~marchal/

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