Re: Many Fermis Interpretation Paradox -- So why aren't they here?
You can still have realism, but it must be the case that at least some of the things we think of as ``real physical objects´´ like e.g. electrons are not real. Suppose you are a virtual person, programmed by me and living in a virtual environment. You do some experiments to find the laws of physics. You try to break up things and look what they are ``made of´´. Would you ever discover how the pentium processor works if you proceed this way? Similarly would you ever discover anything about neurotransmitters and neurons while you are asleep (and dreaming about doing experiments). It is more likely that you would be stuck with theories that promote nonexisting artefacts of the virtual world to real physical entities. Saibal - Oorspronkelijk bericht - Van: Bruno Marchal [EMAIL PROTECTED] Aan: [EMAIL PROTECTED]; [EMAIL PROTECTED] Verzonden: donderdag 10 oktober 2002 14:55 Onderwerp: Re: Many Fermis Interpretation Paradox -- So why aren't they here? If Gerard 't Hooft's deterministic account of Quantum field is both realist and Lorentz invariant, it would contradict Bell's theorem or Kochen and Specker theorem, or GHZ (Greenberger, Horn, Zeilinger), ... or it would be equivalent with Everett (accepting that quantum contextuality + realism implies the many-things). Bruno Original message by Saibal Mitra: - Oorspronkelijk bericht - Van: Bruno Marchal [EMAIL PROTECTED] Aan: Tim May [EMAIL PROTECTED]; [EMAIL PROTECTED] Verzonden: vrijdag 4 oktober 2002 18:13 Onderwerp: Re: Many Fermis Interpretation Paradox -- So why aren't they here? At 9:36 -0700 1/10/2002, Tim May wrote: MWI looks, then, like just another variant of modal realism. To wit, there IS a universe in which unicorns exist, and another in which Germany won the Second World War, but these universes are forever and completely out of touch with us. Not quite due to possible interferences. We do have empirical evidences for those worlds imo. (if only the two slits + Bell or better GHZ) But quantum field theory can be derived from a completely classical deterministic theory. See.e.g.: 1) Quantum Gravity as a Dissipative Deterministic System Class.Quant.Grav. 16 (1999) 3263-3279 http://arxiv.org/abs/gr-qc/9903084 2) Quantum Mechanics and Determinism http://arxiv.org/abs/hep-th/0105105 3) How Does God Play Dice? (Pre-)Determinism at the Planck Scale http://arxiv.org/abs/hep-th/0104219
Re: Many Fermis Interpretation Paradox -- So why aren't they here?
Saibal Mitra wrote: Suppose you are a virtual person, programmed by me and living in a virtual environment. You do some experiments to find the laws of physics. You try to break up things and look what they are ``made of´´. Would you ever discover how the pentium processor works if you proceed this way? Interesting problem. I would set up experiments to test the limit of my world. I would find out that I get a exception interrupt when I blow the stack, run out of memory or divide by zero. This information would enable me to measure the size of my space (memory) and the limitations of the physics underlying my world. I would test the speed of each operation in my world, and find out that some operations such as MOVE and TEST IF ZERO are relatively more or less time consuming . From this information, I would formulate theories on how these operations may be implemented at a higher level and what kind of mechanism or architecture may be responsible for such timing relationships. I would watch for white rabbits, which in my world may be unexplained events such as INPUTS and try to understand what these INPUTS imply and by what mechanism they may be generated. I would generate certain events, behavior (OUTPUTS) and observe how the INPUTS are affected by my OUTPUTS. From this information I may infer that there is an intelligence lurking beyond my world and I may even deduce that its name is Saibal Mitra. George
Re: Many Fermis Interpretation Paradox -- So why aren't they here?
- Oorspronkelijk bericht - Van: Bruno Marchal [EMAIL PROTECTED] Aan: Tim May [EMAIL PROTECTED]; [EMAIL PROTECTED] Verzonden: vrijdag 4 oktober 2002 18:13 Onderwerp: Re: Many Fermis Interpretation Paradox -- So why aren't they here? At 9:36 -0700 1/10/2002, Tim May wrote: MWI looks, then, like just another variant of modal realism. To wit, there IS a universe in which unicorns exist, and another in which Germany won the Second World War, but these universes are forever and completely out of touch with us. Not quite due to possible interferences. We do have empirical evidences for those worlds imo. (if only the two slits + Bell or better GHZ) But quantum field theory can be derived from a completely classical deterministic theory. See.e.g.: 1) Quantum Gravity as a Dissipative Deterministic System Class.Quant.Grav. 16 (1999) 3263-3279 http://arxiv.org/abs/gr-qc/9903084 2) Quantum Mechanics and Determinism http://arxiv.org/abs/hep-th/0105105 3) How Does God Play Dice? (Pre-)Determinism at the Planck Scale http://arxiv.org/abs/hep-th/0104219
Re: Many Fermis Interpretation Paradox -- So why aren't they here?
At 9:36 -0700 1/10/2002, Tim May wrote: MWI looks, then, like just another variant of modal realism. To wit, there IS a universe in which unicorns exist, and another in which Germany won the Second World War, but these universes are forever and completely out of touch with us. Not quite due to possible interferences. We do have empirical evidences for those worlds imo. (if only the two slits + Bell or better GHZ) BTW, Tim, I am discovering n-categories. Quite interesting. John Baez has written good papers on that, like his categorification paper. Have you read those stuff. Could be useful for the search of coherence condition in many world/observer realities ... I've been reading Baez for a while. An excellent teacher. I hear he's working on a book on n-categories. And Baez and my namesake, J. Peter May--unrelated to me, are leading a consortium to research n-categories more deeply. I confess that I have only vague ideas what they aresort of generalizations of natural transformations, I sense. A very natural generalisation (!). Just replace the hom Sets by hom Categories. In which you can again replace the hom sets by hom categories What is intriguing is the existence of coherence conditions making those constructions apparently very genuine for many stuff from quantum field theories. (I'm still studying categories at a more basic level, having jumped ahead to other areas, as is my wont.) His From Categories to Feynman Diagrams (co-authored with James Dolan) and several of his related papers are good introductions. Thanks. I didn't see this one. Very nice. http://arxiv.org/abs/math.QA/0004133 Chris Isham is also very good on drawing the connections between conventional quantum mechanics (i.e., stuff in the lab, not necessarily quantum gravity or quantum cosmology) and category/topos theory. (In particular, the collapse of the wave function and measurement looks like a subobject classifier, or, put another way, the usual transition from neither true nor false in a Heyting algebra to the one or the other we _always_ see once there is any chance to observe/measure/decide. That is, Heyting -- Boolean is what the mystery of QM centers around. Boolean or Heyting Toposes or cartesian closed categories have exponentials. They describes subjects (first or plural). They are distributive categories. You always seem to forget the non distributive categories (nicely introduced in Lawvere Shanuel book), which are akin to linear and quantum logic, and quantum algebra. Technically linearity seems to be a consequence of the non distributivity, I'm not sure I really grasp the idea yet. (I am intrigued to find that Jeffrey Bub, in his Interpreting the Quantum World, 1997, makes central use of possible worlds, lattices, and such. While he does not explicitly mention Heyting algebras, the connection is close, and is implicit in the math. Had I encountered this approach when I was studying QM, I might have pursued it as a career. Instead, I was bored out of my mind solving partial differential equations for wave functions inside boxes. Ugh.) I'm reading Graham Priest's An Introduction to Non-Classical Logic, 2001, which covers various modal logics, conditional logics, intuitionist logic, many-valued logics, and more (first degree entailment, relevant logic, etc.). I should read it. One day I will make a comment about its use of Godel in his book In contradiction. The tableaux approach is new to me. They look like the trees of Smullyan, and hence like semilattices. I have used the smullyan trees for the G and Co. theorem provers. The tableaux structure reflects in some way the Kripke structure. Posets appears with S4-like modal logic. You should study Gentzen presentation of logic which are naturally related to categories. An indigest but brilliant introduction to many (intuitionnist) logics is the North-Holland logic book by Szabo: Algebra of proofs. To bad he miss the braided monoidal categories ... For a categorician, knots theory is a branch of logic. (I'm also reading Davey and Priestley's Introduction to Lattices and Order, along with parts of Birkhoff's classic, and the lattice/poset approach continues to appeal to me greatly. Nice. They have chapters on the non distributive order structures. It's a vantage point which makes all of this heretofore-boring-to-me logic stuff look terribly interesting. I'm viewing most programs/trees/refinements/tableaux as branching worlds, as possible worlds (a la Kripke), to be further branched or discarded. Hence my focus on MWI and Everything remains more on the mathematics. (I just ordered my own copy of Goldblatt's Mathematics of Modality.) Possible worlds, something I only encountered in any form (besides Borges, Everett, parallel universes sorts of references) in the past several years, is my real touchstone. And, more mundanely, I think it applies to cryptography and money. I had a
Re: Many Fermis Interpretation Paradox -- So why aren't they here?
At 12:26 -0700 30/09/2002, Tim May wrote: If the alternate universes implied by the mainstream MWI (as opposed to variants like consistent histories) are actual in some sense, with even the slightest chance of communication between universes, then why have we not seen solid evidence of such communication? I am not sure I understand why you oppose the mainstream MWI and the consistent histories (although many does that, I don't know why). In all case, if QM is right (independently of any interpretation), parallel histories or parallel universes cannot communicate, they can only interfere(*). The same happens with comp. Probability measures are global and depends on the whole collection of relative computational histories, but this does not allow the transfer of one bit from one computation to another. BTW, Tim, I am discovering n-categories. Quite interesting. John Baez has written good papers on that, like his categorification paper. Have you read those stuff. Could be useful for the search of coherence condition in many world/observer realities ... (*) Unless Plaga is right, and it exists 100% non elastic interaction, which I doubt ... Bruno
Re: Many Fermis Interpretation Paradox -- So why aren't they here?
On Tuesday, October 1, 2002, at 06:37 AM, Bruno Marchal wrote: At 12:26 -0700 30/09/2002, Tim May wrote: If the alternate universes implied by the mainstream MWI (as opposed to variants like consistent histories) are actual in some sense, with even the slightest chance of communication between universes, then why have we not seen solid evidence of such communication? I am not sure I understand why you oppose the mainstream MWI and the consistent histories (although many does that, I don't know why). In all case, if QM is right (independently of any interpretation), parallel histories or parallel universes cannot communicate, they can only interfere(*). The same happens with comp. Probability measures are global and depends on the whole collection of relative computational histories, but this does not allow the transfer of one bit from one computation to another. I of course was not claiming such communication (or travel, whatever) would be easy. Just doing a thought experiment settting some very rough bounds on how impossible the communication or travel would be. One of the conclusions of How come they're not here? is that, in fact, such communication or travel is essentially impossible (else they'd _be_ here). MWI looks, then, like just another variant of modal realism. To wit, there IS a universe in which unicorns exist, and another in which Germany won the Second World War, but these universes are forever and completely out of touch with us. BTW, Tim, I am discovering n-categories. Quite interesting. John Baez has written good papers on that, like his categorification paper. Have you read those stuff. Could be useful for the search of coherence condition in many world/observer realities ... I've been reading Baez for a while. An excellent teacher. I hear he's working on a book on n-categories. And Baez and my namesake, J. Peter May--unrelated to me, are leading a consortium to research n-categories more deeply. I confess that I have only vague ideas what they aresort of generalizations of natural transformations, I sense. (I'm still studying categories at a more basic level, having jumped ahead to other areas, as is my wont.) His From Categories to Feynman Diagrams (co-authored with James Dolan) and several of his related papers are good introductions. Chris Isham is also very good on drawing the connections between conventional quantum mechanics (i.e., stuff in the lab, not necessarily quantum gravity or quantum cosmology) and category/topos theory. (In particular, the collapse of the wave function and measurement looks like a subobject classifier, or, put another way, the usual transition from neither true nor false in a Heyting algebra to the one or the other we _always_ see once there is any chance to observe/measure/decide. That is, Heyting -- Boolean is what the mystery of QM centers around. (I am intrigued to find that Jeffrey Bub, in his Interpreting the Quantum World, 1997, makes central use of possible worlds, lattices, and such. While he does not explicitly mention Heyting algebras, the connection is close, and is implicit in the math. Had I encountered this approach when I was studying QM, I might have pursued it as a career. Instead, I was bored out of my mind solving partial differential equations for wave functions inside boxes. Ugh.) I'm reading Graham Priest's An Introduction to Non-Classical Logic, 2001, which covers various modal logics, conditional logics, intuitionist logic, many-valued logics, and more (first degree entailment, relevant logic, etc.). The tableaux approach is new to me. They look like the trees of Smullyan, and hence like semilattices. (I'm also reading Davey and Priestley's Introduction to Lattices and Order, along with parts of Birkhoff's classic, and the lattice/poset approach continues to appeal to me greatly. It's a vantage point which makes all of this heretofore-boring-to-me logic stuff look terribly interesting. I'm viewing most programs/trees/refinements/tableaux as branching worlds, as possible worlds (a la Kripke), to be further branched or discarded. Hence my focus on MWI and Everything remains more on the mathematics. (I just ordered my own copy of Goldblatt's Mathematics of Modality.) Possible worlds, something I only encountered in any form (besides Borges, Everett, parallel universes sorts of references) in the past several years, is my real touchstone. And, more mundanely, I think it applies to cryptography and money. I had a meeting/party at my house a few weeks ago with about 50 people in attendance (gulp!). We had a series of very short presentations. I gave a very rushed 10-minute introduction to intuitionistic logic, mainly focused on my time as a poset, a lattice example, citing the natural way in which not-not A is not necessarily the same as A. If the past of an event is A, then not-A is its future. But the not-future is larger than the
Re: Many Fermis Interpretation Paradox -- So why aren't they here?
It could just mean that communication between the universes is impossible. Which is not surprising, really, as the division between universes in the MWI is what allows conscious thought to exist. It is perhaps of more interest to other multi-universe scenarios that are independent of the anthropic principle - I'm thinking here of Smolin's black hole universes, and also patches that lie outside our lightcone, which is almost the same thing. There is a cosmic censorship conjecture, that singularities can never be naked. Perhaps the Fermi Where are they argument almost proves the case. Cheers Tim May wrote: If the alternate universes implied by the mainstream MWI (as opposed to variants like consistent histories) are actual in some sense, with even the slightest chance of communication between universes, then why have we not seen solid evidence of such communication? Amongst the universes, many (many is a huge number, obviously) of them will be way ahead of us. Some will have had galactic civilizations for a billion years. Some will be versions of Earth except that the Egyptians pioneered electronics and hence the world is a few thousand years ahead of our world...even assuming time is commensurate with ours. And so on. You can all imagine the rich possibilities. If these universes are even remotely able to affect each other, through perhaps enormously advanced technology, then the vast number of such possible worlds would suggest that at least some of them have figured out how to do so. And yet they aren't here. No visitors from alternate universes. No signals sent in, a la Benford's Timescape. Perhaps we don't know how to listen. Perhaps there are so many possible universes to potentially visit that we just haven't been gotten to yet. Perhaps in a multiverse of so many possibilities, ours is just not an interesting destination. Maybe there's a kind of MWI censorship going on: since we are still debating the validity of MWI, we obviously are in a universe where MWI has not been proved through such a visit. (There are many divergent series here, making even crude estimates difficult and probably worthless.) Hmmm --Tim May Prime, resident of Earth Prime A/Prof Russell Standish Director High Performance Computing Support Unit, Phone 9385 6967, 8308 3119 (mobile) UNSW SYDNEY 2052 Fax 9385 6965, 0425 253119 () Australia[EMAIL PROTECTED] Room 2075, Red Centrehttp://parallel.hpc.unsw.edu.au/rks International prefix +612, Interstate prefix 02
Re: Many Fermis Interpretation Paradox -- So why aren't they here?
Let's consider Tim May's question, "why have we not seen solid evidence of such communication," and Russell Standish's statement, "It could just mean that communication between the "universes" is impossible." Now lets list the relevant constants andsome interpretationsof quantum theory as they could apply to the "many worlds" interpretation of quantum mechanics (Everett). 1. The theory mandates multiple states for every particle in existence. 2. The collapse model says our observations affect the outcome of experiments: it assigns a central role to consciousness. 3. Photons, electrons, and other subatomic particles are not hard and indivisible. They behave as both waves and particles. 4. Particles can appear out of nothing - a pure void - and disappear again. 5. Physicists have teleported atoms and moved them from one place to another without passing through intervening space. 6. A single particle occupies not just one position, but exists here, there, and many places in between. 7. Quantum theory must hold at every level of reality - not just the subatomic world (David Deutsch). 8. The double slit experiment offers a rare example of two overlapping realities, in which photons in one universe interfere with those in another. 9. All quantum states are equally real, and if we see only one result of an experiment, other versions of us must see all the remaining possibilities. 10. "I don't think there are any interpretations of quantum theory other than many worlds.The others deny reality." (David Deutsch). Given the constants and some interpretations of quantum theory, I would like a wide variety of views on what's theoretically required to communicate with "many worlds," and what would present "solid evidence of such communication." For starters, let's consider David Deutsch's conjecture: "In fact, says Deutsch, a quantum computer could in theory perform a calculation requiring more steps than there are atoms in the entire universe. To do that, the computer would have to be manipulating and storing all that information somewhere. Computation is, after all, a physical process; it uses real resources, matter and energy. But if those resources exceed the amount available in our universe, then the computer would have to be drawing on the resources of other universes. So Deutsch feels that if such a computer is built, the case for many worlds will be compelling." -Bob Strasser - Original Message - From: Russell Standish Sent: Monday, September 30, 2002 6:49 PM To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: Re: Many Fermis Interpretation Paradox -- So why aren't they here? It could just mean that communication between the "universes" isimpossible. Which is not surprising, really, as the division between"universes" in the MWI is what allows conscious thought to exist.It is perhaps of more interest to other multi-universe scenarios thatare independent of the anthropic principle - I'm thinking here ofSmolin's black hole universes, and also patches that lie outside ourlightcone, which is almost the same thing. There is a "cosmiccensorship conjecture", that singularities can never be naked. Perhapsthe Fermi "Where are they argument" almost proves the case.CheersTim May wrote: If the alternate universes implied by the mainstream MWI (as opposed to variants like consistent histories) are "actual" in some sense, with even the slightest chance of communication between universes, then why have we not seen solid evidence of such communication? Amongst the universes, many ("many" is a huge number, obviously) of them will be way ahead of us. Some will have had galactic civilizations for a billion years. Some will be versions of Earth except that the Egyptians pioneered electronics and hence the world is a few thousand years "ahead" of our world...even assuming time is commensurate with ours. And so on. You can all imagine the rich possibilities. If these universes are even remotely able to affect each other, through perhaps enormously advanced technology, then the vast number of such possible worlds would suggest that at least some of them have figured out how to do so. And yet they aren't here. No visitors from alternate universes. No signals sent in, a la Benford's "Timescape." Perhaps we don't know how to listen. Perhaps there are so many possible universes to potentially visit that we just haven't been gotten to yet. Perhaps in a multiverse of so many possibilities, ours is just not an interesting destination. Maybe there's a kind of MWI censorship going on: since we are still debating the validity of MWI, we obviously are in a universe where MWI has not been proved through such a visit. (There are many divergent series here, making even crude estimates difficult and probably worthless.) Hmmm --Tim
