
#109
Jan1909, 10:53 PM

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PF Gold
P: 1,767

You don't get and assured outcome because you are inherently not preparing individual modes for the individual particles. Measuring the pair halves singly is not compatible with the mode of preparation here by the definition of entanglement. You can in principle recombine the pair and there is an equivalent measurement compatible with the entangled mode which will be assured. Again of course the measurement process for incompatible measurements or equivalently incompatible mode of preparation and subsequent measurement is not deterministic in this sense. You can't assure arbitrary pairs of classical measurements! Parse what I said originally more carefully. You choose what you are going to measure and what value you want it to have and I can throw you a system which will have the measured value you chose. The dynamic evolution, the part of quantum physics which is talking about what's happening "out there" and thus where we need to be to talk about determinism, is deterministic. You update your bet in blackjack once you see the dealers hole card (when the rules allow as when you double down). You update your expectation of winning the hand. This doesn't reshuffle the cards it is not the cards which updates but your knowledge. 



#110
Jan2009, 01:09 AM

P: 242





#111
Jan2009, 01:12 AM

P: 242

The point here is that nobody assumes that constants have a physical existence. They only describe the relationship between physical events, but they are not physical themselves. They are mathematical. You can't put them in a plastic bag. :) Similarly, a description of water waves which may cancel each other out, or not, as a description of the surface of the water, allows you to make predictions of what is going to happen, but still the description doesn't describe something that could possibly exist physically. A surface can't exist by itself. It needs something that it is the surface of, and even then it itself still doesn't exist in a physical sense. In the same way, I don't see how the wavefunction could possibly directly describe something that exists physically. It might be the limit of our knowledge (I hope not), but it doesn't make quantum physics "real". Newton's physics and Einstein's physics describe a (more or less) possible physical world, but MWI doesn't. It is mathematical, not physical. 



#112
Jan2009, 03:07 AM

P: 2,456

who promised that physical variables are real, not complex?
colorSpace, then now it is your turn. Please define, what is a difference between "mathematical" and "physical". Say I provide a description of some process. What requirements must be satisfied so you dont say "no, it is just a formula, I need an underlying physical mechanism " ? 



#113
Jan2009, 08:27 AM

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PF Gold
P: 1,767

Example: In the caption for Figure 2 of his Nature article... "According to quantum theory, a card perfectly balanced on its edge will fall down in what is known as a "superposition"  the card really is in two places at once." You see he automatically is negating CI which asserts that the superposition occurs in the description not in the card. Just as Schrodinger was trying to show with his cat. I understand his position and its self consistency (along with EMWI). I understand this viewpoint fully and reject it. He and you need to understand CI fully before rejecting it. In the card example. If we choose a classical probabilistic description of the two card positions then we get a classical "superposition" of outcomes (probability density function with two spikes). We don't call it a superposition because probability densities don't add like vectors. But the probability density function still "collapses" when we actually look at the classical cards and update our knowledge. Also in that article he states: "Everett's theory is falsifiable by future lab experiments: no matter how large a system they probe, it says, they will not observe the wave function collapse." A blatant denial of CI. Again we don't observe wave functions (except in that we look at them on paper) so of course we don't observe their collapse (except when we collapse them on paper) This "logic" is similar to the old joke: { "I'm banging two rocks together to keep away the dragons!" But there aren't any dragons! "See its working!" } His prediction that we'll never see wavefunction collapse is like the the assertion that we will never see dragons do the hula dance. Clearly that's falsifiable! (sarcastic tone of voice) Skimming some of the other articles on his website I don't see any sign that he even understands CI and what wavefunction collapse means in CI. I'm not strongly inclined to read further at this stage... I've classes to teach and a presentation to prepare. Tegmark wants a "mathematical" (ontological) description of the universe. He's a cosmologist so I understand the desire, especially given the current geometric model of classical GR. But in so assuming he automatically denies CI. Fine for him but you can't argue from your conclusion. Any "arguments" he makes as to why MWI is superior to CI are circular. His dismissal of CI as metaphysical solipsism is a category error. Denial of reality (as can be described in terms of objective states) is not denial of external "actuality" but of the format one is choosing to describe it. CI may be characterized as ontological solipsism if you like but this doesn't preclude knowledge about external nature. Only knowledge of its "objective state". But really CI goes slightly further in that it even denies ignorance about the world's "objective state". CI asserts that "objective state" is meaningless at the quantum level. This assertion is not a physical statement it is a semantic one. In science "meaning" implicitly has an "operational" qualifier. 



#114
Jan2009, 01:31 PM

P: 2,456

BTW just one another reason forloving MWI:
quote from another thread: 



#115
Jan2009, 01:37 PM

P: 2,456

jambaugh,
I dont have any hope to makeyou believe in MWI. We aregoing in circles. But I am curious what do you think about the "Tegmark wants a "mathematical" (ontological) description of the universe"  forget for the moment about CI vs MWI and level 3 universes. MWI is only a small part of his article, and not a main point he wanted to make. 



#116
Jan2009, 06:45 PM

Emeritus
Sci Advisor
PF Gold
P: 16,101





#117
Jan2109, 05:44 AM

P: 266





#118
Jan2109, 06:00 AM

P: 2,456

No matter how you want it, you can neither wipe out quasars from the sky nor make number 9 a prime one. So that part of you definition is not useful. Another part of your definition is recursive (check BOLD)  it says that "real"  is something that "physically" exist. But I asked what is "physical" in the very beginning! So sorry, but I dont see any useful definitions... 



#119
Jan2109, 06:04 AM

P: 266

Wipe us out and our concept of numbers goes with it, unless some aliens find our probes or are listening in on our transmissions. Don't you think the idea, an old fashioned one I might add, that numbers actually physically exist belongs in Plato's time? If not on another thread? "real" is in inverted commas because I'm using it beyond its definition, or not as it's meant exactly. The difference is a semantic one between pure and applied maths of interest only to philosophers with too much spare time, which for most philosophers of the age is practically all of them. 



#120
Jan2109, 06:11 AM

P: 2,456

I do believe that numbers exist independently of us. Otherwise how could physical laws work before we existed?
I even completely share Max Tegmark's idea that any mathematical system defines a universe. 



#121
Jan2209, 05:47 AM

P: 266





#122
Jan2209, 06:07 AM

P: 2,456

Lets assume that you are right and numbers are not the reality, but just a way how we think. On another planet aliens can probably live without any numbers at all, using absolutely different concepts, which do not have any intersections with our mathematics.
Then in order to prove that you are right you just need to show, that it is possible to build: * a different mathematics/different sort of reasoning * which is not isomorphic to our mathematics * and which can correctly describe the universe If you manage to do it, I will eat my hat! 



#123
Jan2209, 08:16 AM

P: 266





#124
Jan2209, 09:17 AM

Sci Advisor
PF Gold
P: 1,767

In particular their mathematical description cannot both be nonisomorphic to ours and describe the same class of physical phenomena except where the mathematics DOES describe nonreal aspects of nature. This is the role of Occam's razor to cut away all but what is essential to the physics. It is also curious that the nonisomorphism between CI and MWI (and Bhomian pilot waves) doesn't satisfy you that there's something nonreal (or as I rather say nonactual) in one or all of the interpretations given all are consistent with observable phenomena. Further note that the density operator formulation of quantum mechanics is superior in many ways (more general description of systems). You can dispense with "wavefunctions" all together. You will note that the density operator is more easily interpreted in its proper (CI) "probabilistic description of..." role. So tell me which is the "real part" the wave function or the density operator? Mathematical note, the role the density operator plays in QM is its use in defining functionals on operators i.e. as cooperators. So imagine your aliens formulated QM straight from an operator algebra and its dual cooperator coalgebra and never defined a Hilbert space equivalent. Side note: the choice of pi as a fundamental constant is not convention free. 2pi would have done as ratio of circumference to radius of a circle (or ratio of surface area to central crosssectional area of a sphere (suppose the aliens' principle sense is tactile and they feel the sphere is a more fundamental shape). Now if you want to communicate with aliens start with a binary expansion of e. (And hope they work with continuum calculus instead of an umbrial equivalent.) 



#125
Jan2209, 09:24 AM

P: 266

What if they are blind and use sound to see and talk and pheromones to designate emotion and inflection of words, in that case 1 to an alien would mean nothing, the impression of more than one source of reflection of sound and it's smell would be his numerical system or something like that. In fact it bewilders me that we think just because we are so formed that anyone in the Universe might be so bizarre as to put our limited comprehension of sense to shame. They might communicate with shapes only as thoughts for all we know, in which case 2 would be meaningless, pi wouldn't though. The shape of two objects would be a number, in that sense we'd have infinite numbers without any fixed number system, with distinctions for location rather than number in the numerical system, it'd be weird. But two shapes together wouldn't mean 2 objects, it would mean 1 object with x shape. The only thing that's eternal and exists is the Universe, everything else is a matter of conception and perception and etymology. What is at least constant from our beginnings is our humanocentric insistence on things.




#126
Jan2209, 09:29 AM

Sci Advisor
PF Gold
P: 1,767

And if that is the criterion then clearly any component of the mathematical description which doesn't matter on this point can't be determined as correct or incorrect w.r.t. the universe, only correct or incorrect with regard to the appropriateness of its inclusion in this context of empirical science vs. philosophical speculation of the same nature as "how many angels...?" 


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