Re: MWI

On 29 May 2013, at 22:43, hibbsa wrote:

>
>
> --- In [email protected], Bruno Marchal  
> <marchal@...> wrote:
> >
> > On 27 May 2013, at 16:33, hibbsa wrote:
> >
> > >
> > >
> > > --- In [email protected], Bruno Marchal
> > > <marchal@> wrote:
> > > >
> > > >
> > > > On 27 May 2013, at 14:32, hibbsa wrote:
> > > >
> > > > > Does this question an answer?
> > > > >
> > > > > Is it logically possible for the multiverse to produce  
> macroscopic
> > > > > universes exhibiting any statistically significant  
> differences than
> > > > > our own universe?
> > > > >
> > > > > I mean "statistically significant" in the most rounded  
> possible sense.
> > > > >
> > > > > - Any difference that our universe couldn't have gone the  
> way of,
> > > > > consistent with its initial conditions all laws of physics  
> assumed
> > > > > constant
> > > > >
> > > > > - Any difference in terms of any phenomena existing at any  
> level of
> > > > > abstraction in greater or lesser or with any difference in any
> > > > > attribute including (a) abundance (b) probability of  
> occurrence (c)
> > > > > relation with other phenomena (d) internal constituents.
> > > > >
> > > > > - Any difference on any level at all where to be different  
> at the
> > > > > bottom level requires contradicting the probabilistic rules  
> of QM
> > > > > and/or causing unique consequences of those rules as a  
> result of
> > > > > interaction with macroscopic phenomena and at the top level  
> requires
> > > > > any significant difference in the timing, macroscopic and
> > > > > microscopic structure, and ultimate fate of the universe.
> > > > >
> > > > > The reason I think this question deserves a proper full  
> answer. And
> > > > > by that I mean...not just a criticism of the way the  
> question is
> > > > > formed is because there could be important  
> consequences...which may
> > > > > not be worked through. And the philosophy is all about  
> intrepidly
> > > > > working through the consequences?
> > > > >
> > > > > I've got some consequences waiting for your criticism. But I  
> think
> > > > > it's important to establish your criticism or acceptance of  
> the
> > > > > above first.
> > > > >
> > > >
> > > > What do you mean by "exhibiting any statistically significant
> > > > differences than our own universe? "
> > > >
> > > > If you prepare an electron in the up + down state, and if you  
> measure
> > > > its up/down state, QM predicts that you will end up yourself  
> in the
> > > > "seeing-up + seeing-down" state. If you had decided to go in  
> the North
> > > > or in the south, according to the result of that measurement,  
> you end
> > > > up in the visiting-North + visiting-South. from your points of  
> view
> > > > that is statistically different, imo. You get two  
> macroscopically
> > > > quite different lives. This with a probability 1/2, when  
> evaluated
> > > > before the measurement, about your future first person points  
> of view.
> > > >
> > > > Now if your question is just "is there a macroscopic world in  
> which
> > > > elephant can fly?", the answer is also "yes", but the  
> probability,
> > > > here-and-now, that you will see such an elephant is equivalent  
> to
> > > > winning the big lottery every second for a time much bigger  
> than the
> > > > age of the universe, so don't count on it. Near death, that  
> question
> > > > is just much more complex to get an answer today.
> > > >
> > > > The MWI is just the statement that the SWE applies to  
> everything,
> > > > macrosocopic, mesoscopic, microscopic, etc.
> > > >
> > > > OK?
> > > >
> > > > Bruno
> > > >
> > >
> > > Hi Bruno - no not OK but my fault. I meant statistically different
> > > macroscopic universes. So you need to name your macroscopic
> > > object...preferably with clear, known emergent properties. And  
> show
> > > how those emergent properties are altered in any of its associated
> > > quantum histories, from say,....the differences that would be
> > > exhibited by enough copies of the object in this universe to
> > > represent all the possible quantum histories.
> > >
> > > And if there aren't any differences...and if our macroscopic world
> > > is emergent phenomena from the quantum state, then it's hard to  
> see
> > > how the multiverse can exhibit statistically significant  
> differences
> > > between its macroscopic universes.
> > >
> > I am still not sure I really grasp your question. Planck constant is
> > very little. So if you decide to boil some water, QM predicts that  
> it
> > will boil normally in most of the branches you can access in the
> > multiverse, with some non negligible probability. Then you will have
> > the many universes fluctuating from that behavior, but,
> > proportionally, they will be rarer. At the extremal point of the
> > spectrum of the possibilities, you will have the "Harry Potter"
> > universe, but those are quasi-impossible to access (a good thing),
> > except perhaps near death, as the probabilities on the first person
> > expectancies get harder to compute.
> >
> > Our macroscopic world is not emergent from the multiverse, except  
> for
> > most quantum properties, so our universe is quantum normal, with
> > solid, liquid and gaz well described by the quantum statistics. but
> > each branches differ on orthogonal or quasi orthogonal state, and so
> > can differ in macroscopic properties (like if earth was not hit by  
> an
> > asteroid a long time ago), but such branches will still obeys the  
> same
> > macroscopic laws, like classical mechanics, for example.
> >
> > Our local realities are Gaussian, and that's why we can discern all
> > sort of laws. In fact that appears with just computationalism too.
> > Below our level of substitution, we emerge from infinities of
> > computations, which interfere statiostically, but above that  
> level, we
> > have much simpler classical laws. In QM this is explained by MWI +
> > decoherence. With digital mechanism it is far more complex, but then
> > we can explain where the quantum comes from.
> >
> > I hope this help, feel free to make your question more precise, if I
> > miss your point,
> >
> > Bruno
> >
>
> Sorry for the delay...I just wanted to think about your response for  
> a couple of days.
>
No problem. Take your time.



>
> One of the issues is that what I'm saying here about emergence and  
> emergent properties is very much based on David Deutsch's BoI book  
> and also his version of MWI.
>
> I'm not saying your points aren't valid or important....but would it  
> be possible for you to reference his Reality of Abstractions chapter  
> and then answer the question ,more generally in terms of emergent  
> properties as he defines them?
>
> The basic argument from me is that, since macroscopic reality is in  
> terms of emergence, for the multiverse to produce a significantly  
> different macroscopic world, it would have to change the emergent  
> properties.
>
I don't know for David. With computationalism made explicit, the whole  
of the physical reality emerges from the first person experience that  
you can associate to some infinities of arithmetical relations. The  
whole of physics is emergent, I think, from arithmetic or Turing  
equivalent. But that view from inside arithmetic is not Turing  
equivalent.



>
> I appreciate you've pointed to a Harry Potter world...but  
> surely...that world can also be understood in terms of something  
> that * might*, or *might have* happened in this world?
>
Yes, but with a very small relative probability, which is eventually  
determined by the axioms for the basic ontology (arithmetic or Turing  
equivalent). The view from inside is much more rich, and indeed  
arguably beyond the whole of mathematics.

Bruno




>
> 

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





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