On 30 Aug 2009, at 10:12, marc.geddes wrote:

> On Aug 30, 7:23 pm, Bruno Marchal <marc...@ulb.ac.be> wrote:
>> On 30 Aug 2009, at 07:06, marc.geddes wrote:
>>> It’s true that there is no wave function collapse in Bohm, so it  
>>> uses
>>> the same math as Everett.  But Bohm does not interpret the wave
>>> function in ‘many world’ terms, in Bohm the wave function doesn’t
>>> represent concrete reality, its just an abstract field – the  
>>> concrete
>>> reality is the particles, which are on a separate level of  
>>> reality, so
>>> there are no ‘zombies’ in the wave function.
>> In Bohm, the wave is not an abstract field, it plays a concrete role
>> in the determination of the position of the particles I can observed.
>> It is not a question of interpretation, it follows form the fact that
>> the wave guides the particles by simulating completely the parallel
>> branches. And in those branches the person acts exactly like  
>> believing
>> they are made of particles "like us".
>> How could we know that we belong to the branch with particles? We  
>> need
>> already to abandon CTM here.
> Yes, in Bohm the wave is 'real' , but to interpret the wave as
> actually referring to ordinary concrete things is already to
> presuppose 'many worlds' ;

Assuming the negation of computationalism in the cognitive science  
(like Bohm, I think). So why not.

But look at this. I decide to do the following experience. I prepare  
an electron so that it is in state up+down. I measure it in the base  
{up, down}, and I decide to take holiday in the North if I find it up,  
and to the south, if I find it down.
Not only that. I decide to go, after the holiday,  to the amnesia  
center where all my memories, from the state of the electron to  
everything which follows, except my feeling about how much I enjoy the  
holliday. And I am asked to answer by yes or no to the question "did  
you enjoy your holiday. Then, thanks to the amnesia my yes+no states  
will be used In this way.  I interfere with myself, and what will  
follow in the new branch where I have fuse with myself, my, and your,  
future is determined by my contentment qualia, in the two branches of  
the waves.
In Everett universal wave (or Heisenberg universal matrix) and already  
in arithmetic, "physicalness" is an indexical, we don't need the  
notion of reality, just relative self-consistency.
We can cease to reify matter, and this is nice because I think that  
this is what stuck us on the mind-body problem so long.

> reality has two levels, so really there's
> two different definitions of 'real' in Bohm.

You say so.

> There are no 'people' in
> the wave, its a more abstrast entity than ordinary concrete reality.

Ordinary concrete reality is a projection of the ordinary universal  
machine from an infinity of them, to sum up roughly UDA conclusion.

A deep weakness of Bohm, is that we can do all the possible uses of QM  
from the SWE only, and then we have to solve a complex potential  
equation to just "eliminate" the possibility of life and consciousness  
in the parallel world?
And this by assuming weird things like non-locality (the root of Bohm  
"non reductionism, I think), and non comp (or is this the root of "non  

But then why not.

I find this not highly plausible, but if you make clear your theory  
and reason validly there is no problem, go for it.

>>> Brent did make the point that it has trouble with field theory, but
>>> this problem is a feature of other interpretations also.  Brent also
>>> criticised the non-locality, but again, this problem is a feature of
>>> all other interpretations also.
>> I disagree. Everett restores locality, as he explains himself.  
>> Deutsch
>> and Hayden wrote a paper explaining rather well how locality is
>> completely restored in the many-worlds view.
>> And as I said, comp alone entails the many "worlds" (or many
>> dreams, ...). That part of the SWE confirms comp. If I remember well,
>> Bohm intuited this and made some case against the computationalist
>> hypothesis.
>> Bruno
> If MWI does eliminate non-locality, that would be a strong point in
> its favor,


> but is there any conclusive paper demonstrating that its
> done this?  I have not heard of one - I assume the Deutsch/Hayden
> paper is just their attempt to restore locality which does not
> succeed.

The first time I understood this is in the reading of Everett long  
text. But it was still a bit unclear until I read the Everett FAQ  
(Michael Clive Price:  http://www.hedweb.com/manworld.htm), which  
convinces me that it should not been so much difficult to prove, from  
the SWE, that the worlds appears local for the normal observers. (no  
use of Bayes!)
A non rigorous yet convincing (!) proof of QM locality (in the normal  
branches) has been found by Tipler.
Deutsch and Hayden, makes this even more precise, using the Heisenberg  
picture. Somehow an experience (a preparation) is a partitioning of  
the local accessible part of the multiverse, and measurement are  
generalized self-localization in the multiverse. And eventually they  
found a way to derive the Born rule from purely decision theoretic  
consideration (and uses implicity (in the paper, I think) or explicity  
(in Deutsch FOR book) comp). (But I have personnaly no problem with  
the frequentist intepretation of probability, which eases such type of  

Is the problem of locality solved in Everett QM? I think so since a  
long time, but I know that some physicists or philosophers doubt it,  
but most of the time I have reason to suspect they have a too strict  
view of what the "worlds" can be.



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