Eric Lombrozo wrote: >I've recently started to find more and more problems >with the MWI which lead me to believe that the MWI, >while on the surface appears to resolve many of the >issues the Copenhagen interpretation tries to dodge, >it will also find many problems in time. Not only must >we add assumptions that are experimentally untestable, >but more importantly, there are still at least a few >fundamentally unresolved issues: > >Who is the observer? How do we resolve the measurement >problem?

I begin to guess why Everett decided to met Bohr, and thought it was possible to get some extended "copenhague" label to his "universal wave function". Everett modelises the observer by *classical memory machines*. Classical reasonings and classical communications is what made the observer with Everett and the experimenter with Bohr. It is a seldomly mentionned fundamental common point between Bohr and Everett, and most "non collapse" approaches. With the computationalist hypothesis in the "philosophy of mind" the measurement problem then reduce to one half of the mind body problem. This justifies the hardness of the problem. >What is the reasoning by which we find ourselves in >only one of the universes? Why this universe? >Why this "me"? This is easy enough. No sound introspective machine can predict its own futur experience (that is *result* of experiment) when the experiment involves a self-duplication or better a self-differentiation (which are made possible at some level finitely describable level by comp). >What causes decoherence? What type of interactions >disrupt the unitary evolution of a system, causing >it to jump into a single eigenstate, one per >universe? Nothing disrupt the unitary evolution, but the pure unitary evolution can explain the appearance of such disruptance in the discourse by the classical UM. >Furthermore, who determines the measurement basis on >which this occurs and when it occurs? Who is the >experimenter? In the multiverse all interaction can be considered as measurement. Big quantum system decohere rapidly (this is a consequence of linearity/unitarity (and perhaps even only of geometrical non-commutativity)). SNIP >Now I will venture into deep speculation by making a >proclamation that will understandably make many people >uneasy. Not me :-) (see below). >Yet, the level of speculation here >is significantly less than that required for the MWI. Except there is not one drop of speculation in the MWI. I mean more than betting that SWE applies to physical systems including observers. >I think it is not only more economical (the MWI is >conceptually expensive and fundamentally untestable) ... ? >but also more intuitive and powerful to posit that >state-vector collapse is a result of a conscious >will (the observer(s), entangled with the system in >question). I quite agree with that. If you modelise consciousness by inference of self-consistency and free-will by the ability to partially control alternative self-extensions then with Everett-Deutsch-... (who are using comp) it is just correct that (necessarily first person) consciousness collapses the wave by projecting you in a higher probability subspace *you* choose. The advantage here is that we don't need to postulate that consciousness would makes SWE false. >The Born probabilities correlate with simple >quantum systems in laboratories since the entropy is >relatively small, and once the measurement is amplified, >the entanglement with the rest of the universe becomes >very large indeed, thus we'd expect the central limit >theorem to apply. Indeed. >In other words, few bits - many observers - thus >statistics approximated from the Hamiltonian of the >system alone. Now imagine a system with high entropy of >entanglement and few observer(s) (i.e. coherent)! >Maybe the brain? More and more evidence is accumulating >indicating that the brain might very well be capable of >maintaining quantum coherence at a macroscopic level. Who knows ? >With this idea, it is at once surprising and exciting to >see the direction science can take from here! > >I realize that this approach encounters other >difficulties...but at least there are testable hypotheses >along this path. And the result: we get an extremely >insightful and intuitive way to understand not only >quantum mechanics, but ourselves as conscious observers >with the power of free will. Also, the many potential >technologies stemming from this idea are unfathomable >at the present moment. > >The implications are very deep and I cannot possibly >hope to explain them better than many others have already >done. I'll have to revisit this and add some hyperlinks >when I have more time. For now, I'll leave it up to >the reader to do the research. The MWI is not necessarily incompatible with your proposition. If you accept the hypothesis that *we* are essentially classical universal machine, then the MWI is even strongly compatible with it. (My thesis in a nutshell (and in a more modern formulation) is that comp is enough for explaining why necessarily classical universal machine are bounded by quantum universal one. Bruno http://iridia.ulb.ac.be/~marchal