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From: Gilles HENRI <Gilles.Henri.domain.name.hidden>

Date: Mon, 12 Apr 1999 09:31:51 +0200

*>GH:
*

*>>It is not against these theories. The many-worlds hypothesis + a
*

*>>mathematical constraint such as analyticity of fields could lead to an
*

*>>"everything possible" hypothesis that would imply that all possible worlds
*

*>>are also different everywhere, so "clone free"...
*

*>
*

*>BM:
*

*>This would make the "many-worlds hypothesis" empty. If the worlds
*

*>are so different, how will interference be possible ?
*

In fact there is no precise definition of what is a macroscopic world in

MWI. This is one of the major difficulties of the theory; however it is

logical to consider that two different macroscopic worlds have by

definition negligible interference terms, which makes the conventional

interpretation of QM work (reduction of the wave packet). Interference

terms are important only at the microscopic level.

Note also that the fact that fields are different over any neighborhood of

any point doesn't imply that the interaction vanishes!(Ex: cos x and

cos (x+a) if a<>0 [Pi/2])

*>
*

*>GH:
*

*>> ... it relies on the hypothesis that you think you will
*

*>>really be , or "identify yourself to", one of your copy, which is
*

*>>contestable, especially if you consider that no copy can be exact.
*

*>
*

*>BM:
*

*>Remember that with comp we are by definition informatical (in the
*

*>classical sense) entity, and we are (from a third person point of view)
*

*>100% exactly duplicable. (In the same sense that you can make *in
*

*>principle* a perfect copy of the 10E100 first decimal of PI).
*

but not of PI in a finite time. Of course as we already discussed the

universe could be discrete. But you cannot make an exact copy of it at its

finest level (ie Planck scale) with a machine embedded in it.

The point is that when you say "we are informatical", you probably mean

that, like a computer, our computational structure can be described with

much less information than our physical one. That's why we can built

perfectly reproducible computers, and we can duplicate them with very

different physical structures.

But it can well be (and it is very probable) that the brain is not like our

simple computers. For example the response of neural cell can be some

continuous function of the concentration of hormons. Of course you can hope

to modelize it with a discrete approximation at any level of accuracy. But

by doing that, you start another stuff. The reproduction is not exact

anymore, and you are facing the problem of how deep you must go to

reproduce EXACTLY its behaviour. And in fact the brain is no more

informatical in the first sense, because it may well be that you need the

complete description of its physical state. So unlike our artificial

computers, its evolution is NOT simpler than the evolution of any physical

system. And if you have to go to the quantum level ,(even worse, to the

Planck scale!) you are facing a practical impossibility: it is (even in

principle) impossible to measure the complete quantum state of a single

system, and a fortiori to reproduce it (just because the complex value

Psi(x,t) can not be an observable). And as we already discussed you will be

lead to simulate the whole environment (ie visible Universe) at this level,

which is also impossible...

*>Exercice (I am joking) :
*

*>
*

*>If a mad scientist decides to put you
*

*>into the following quantum "cat" state: Psi =
*

*>
*

*> (1/sqrt(|a_1|^2 + |a_2|^2))*
*

*> [a_1*|you in-hell> + a_2*|you in-paradise>]
*

*>
*

*>and give you the opportunity to choose between
*

*>
*

*>A) Psi with a_1 >>>>>>>>> a_2 (a_2 negligeable compare to a_1) and
*

*>B) Psi with a_2 >>>>>>>>> a_1 (a_1 negligeable compare to a_2)
*

*>
*

*>Will you care about that opportunity ? and if you care,
*

*>what will you choose: A or B ?
*

As you well know, it is impossible to prepare a macroscopic system in any

coherent superposition because of the environment induced decoherence. So

your joke experiment is really impossible (the scientist is either mad or a

lier!).

What is possible of course, and very simple, is to prepare you in some

state like

(1/sqrt(|a_1|^2 + |a_2|^2)°*

[a_1*|you in-hell>|world with you in-hell> + a_2*|you in-paradise>|world

with you in-paradise>]

simply by measuring the spin of a polarized electron on a conveniently

chosen axis (with relative probability a1/a2) and decide to send you in

hell or paradize following the result. Of course as your states are

incoherent you are back to simple probability calculus and the choice is

obvious.

*>
*

*>GH:
*

*>>You
*

*>>could also think that you will die whatever, and choose B just by
*

*>>compassion with other copies.
*

*>
*

*>BM:
*

*>Indeed, but it is better, if only for the sake of the argument,
*

*>to presuppose a minimal amount of selfishness.
*

What I meant is that if you think you die, your selfishness is useless. You

only need a minimal amount of altruism to choose B. If you are a pure

selfish man, you won't care about your choice.

*>
*

*>GH:
*

*>>For example, just
*

*>>modify a little bit your experiments: you won't be destroyed, but you will
*

*>>be put in the unique "paradise" box in A and in the unique "hell" box in B.
*

*>>The other 999999 copies will be placed in the hell or paradise boxes,
*

*>>respectively. Unless you are a saint, and without misprint, won't you
*

*>>choose "A"? It would mean that you care less about your copies than about
*

*>>yourself...
*

*>
*

*>BM:
*

*>I will not choose A, because with comp, a teleportation without
*

*>annihilation of the original is equivalent with a duplication where the
*

*>original is destroyed. So, with comp, your experiment is equivalent to
*

*>mine!
*

*>I have no doubt that this is rather counter-intuitive. But comp, if true,
*

*>is necessarily *unbelievable*.
*

Ok, Bruno may be you would choose B. What about if, despite my promises,

you are not completely confident in my capability of creating the other

999999 copies? (I assume of course that once in the box, you are totally

unaware of what happens really in the other boxes. As is well known, we

will forget everything in paradise!)

May be this thought experiment is a proof that COMP (understood as the

possibility of creating an EXACT copy of yourself) is false?

Cheers

Gilles

Received on Mon Apr 12 1999 - 00:33:24 PDT

Date: Mon, 12 Apr 1999 09:31:51 +0200

In fact there is no precise definition of what is a macroscopic world in

MWI. This is one of the major difficulties of the theory; however it is

logical to consider that two different macroscopic worlds have by

definition negligible interference terms, which makes the conventional

interpretation of QM work (reduction of the wave packet). Interference

terms are important only at the microscopic level.

Note also that the fact that fields are different over any neighborhood of

any point doesn't imply that the interaction vanishes!(Ex: cos x and

cos (x+a) if a<>0 [Pi/2])

but not of PI in a finite time. Of course as we already discussed the

universe could be discrete. But you cannot make an exact copy of it at its

finest level (ie Planck scale) with a machine embedded in it.

The point is that when you say "we are informatical", you probably mean

that, like a computer, our computational structure can be described with

much less information than our physical one. That's why we can built

perfectly reproducible computers, and we can duplicate them with very

different physical structures.

But it can well be (and it is very probable) that the brain is not like our

simple computers. For example the response of neural cell can be some

continuous function of the concentration of hormons. Of course you can hope

to modelize it with a discrete approximation at any level of accuracy. But

by doing that, you start another stuff. The reproduction is not exact

anymore, and you are facing the problem of how deep you must go to

reproduce EXACTLY its behaviour. And in fact the brain is no more

informatical in the first sense, because it may well be that you need the

complete description of its physical state. So unlike our artificial

computers, its evolution is NOT simpler than the evolution of any physical

system. And if you have to go to the quantum level ,(even worse, to the

Planck scale!) you are facing a practical impossibility: it is (even in

principle) impossible to measure the complete quantum state of a single

system, and a fortiori to reproduce it (just because the complex value

Psi(x,t) can not be an observable). And as we already discussed you will be

lead to simulate the whole environment (ie visible Universe) at this level,

which is also impossible...

As you well know, it is impossible to prepare a macroscopic system in any

coherent superposition because of the environment induced decoherence. So

your joke experiment is really impossible (the scientist is either mad or a

lier!).

What is possible of course, and very simple, is to prepare you in some

state like

(1/sqrt(|a_1|^2 + |a_2|^2)°*

[a_1*|you in-hell>|world with you in-hell> + a_2*|you in-paradise>|world

with you in-paradise>]

simply by measuring the spin of a polarized electron on a conveniently

chosen axis (with relative probability a1/a2) and decide to send you in

hell or paradize following the result. Of course as your states are

incoherent you are back to simple probability calculus and the choice is

obvious.

What I meant is that if you think you die, your selfishness is useless. You

only need a minimal amount of altruism to choose B. If you are a pure

selfish man, you won't care about your choice.

Ok, Bruno may be you would choose B. What about if, despite my promises,

you are not completely confident in my capability of creating the other

999999 copies? (I assume of course that once in the box, you are totally

unaware of what happens really in the other boxes. As is well known, we

will forget everything in paradise!)

May be this thought experiment is a proof that COMP (understood as the

possibility of creating an EXACT copy of yourself) is false?

Cheers

Gilles

Received on Mon Apr 12 1999 - 00:33:24 PDT

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