- #246
PeterDonis
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martinbn said:This, and the paper are stupid.
Statements like this should be avoided as they add nothing useful to the discussion.
martinbn said:This, and the paper are stupid.
I'm not sure if I misinterpreted your meaning here. Performing such experiment is obviously possible without any previous commitment to this or that theory or theoretical assumption. However, interpreting it's result will be very different if you assume a simultaneity convention or if you reject constancy of light speed or any other assumption, IOW interpretation of an empirical test requires commitment to some assumption or to its rejection. Even interpreting if the difference of arrival of the signals is significant requires certain assumptions about the statistical error of the apparatus employed in detection, etc.PeterDonis said:The test I have described, as I have already said, does not require having or adopting any theory at all. It is a purely empirical measurement of a very limited result, the order in which two signals arrive.
It's not the only one. You can take the sound-Lorentz-transformed coordinates of the rest frame and get other frames where the same equation holds. The only problem is that nobody will use such artificial coordinates. The context gives us a lot of other things, like light rays, to study sound waves in condensed matter theory, and these many other things don't follow that sound-Lorentz invariance. So, the sound together with the other environment has a preferred frame.PeterDonis said:If it's only valid in one frame, it obviously is not Lorentz invariant, or indeed any kind of invariant. ... You are contradicting yourself.
In the limit ##\Xi, \Upsilon\to 0## it gives the Einstein equations in harmonic coordinates on ##\mathbb{R}^4##, thus, the field-theoretic version of GR. Which is a standard version, and, for example, used by Donoghue et al for the quantization of GR as an effective field theory.PeterDonis said:Schmelzer's theory is not just an interpretation; it makes different predictions from standard "modern physics", so it is a different theory, and must be judged as a different theory, not as "just an interpretation".The point is that there is an interpretation of modern physics compatible with common sense
No, it is not obviously impossible, it is impossible only if one accepts Einstein causality in its strong version (that means, not microcausality of QFT or signal causality) and rejects classical causality connected to a preferred frame.PeterDonis said:Which is obviously impossible if the two measurements are spacelike separated. Which is the whole point of discussing the Bell inequalities in the first place.
Tendex said:I'm not sure if I misinterpreted your meaning here.
Tendex said:interpreting it's result will be very different if you assume a simultaneity convention or if you reject constancy of light speed or any other assumption
Tendex said:Even interpreting if the difference of arrival of the signals is significant requires certain assumptions about the statistical error of the apparatus employed in detection, etc.
Sunil said:the sound together with the other environment has a preferred frame.
Sunil said:This does not contradict that the equation for the sound waves taken alone has that sound-Lorentz invariance.
Sunil said:In the limit
Sunil said:classical causality connected to a preferred frame.
PeterDonis said:No, it won't. As I have already said, the only "result" of the experiment I proposed is which signal arrives first. There is no measurement of speed or indeed any numerical value involved; it's just a simple choice between three discrete possibilities: A arrived before B, B arrived before A, or A and B arrived at the same instant. The time ordering is all along a single timelike worldline. No "interpretation" is required. No assumption about simultaneity or the speed of light or anything else is required.
We agree here, I just called error what you called resolution.PeterDonis said:No, it doesn't. The three possible results are discrete alternatives--see above. There is of course a finite resolution to our comparison of arrival times of the two signals, but that just means the third discrete alternative, "A and B arrived at the same instant", has a finite "width", so to speak--if the two signals arrive within some small enough time interval of each other, our apparatus will tell us they arrived at the same instant even though that's not literally true. But this is not a matter of statistical error; it's just a matter of finite resolution, which will be true for any detector
Tendex said:The latter are what give different interpretations of a "result".
PeterDonis said:You don't have to know what speed light is traveling to test for FTL influences. You just have to emit a light signal at the same time you emit whatever supposed FTL influence you are testing, and see which one arrives first at the destination.Tendex said:I would ask you how you are determining that light travels at its characteristic speed, using a one-way or a round-trip measure of lightspeed to campare it with the FTL influences
Ok, I have no problem with that response. I might have mixed it up with a second instance where you responded talking about your experiment being "one way" but that was when we hadn't cleared up yet about the issue with tachyons. Sorry about my insistence.PeterDonis said:And my whole point was that you do not need to do any of this in order to test whether "FTL influences" are present. The results of such a test might have different implications for different interpretations of theories, yes. But that is not what originally started out this subthread. Here is the original statement of yours that I responded to, and my response:
There is no reason and no base to construct probabilities in some different way. ##\rho(q)=|\psi(q)|^2## is a quite normal probability, it follows a continuity equation.Tendex said:In classical theory with just Galilean relativity FTL influences are no big deal and don't affect causality in any way since the speed of light is not a maximum,so they shouldn't require a theory that constructs probabilities in a different way than the classical real probabilities, however quantum theory does require it to obtain better predictions.
We don't know the theory below Planck length, so we don't know if the waves we observe travel through a "vacuum" or some sort of ether which does not have Lorentz invariance on the fundamental level. If there is a fundamental difference between them is your metaphysical hypothesis.PeterDonis said:There is no such thing as "the sound waves taken alone". The sound waves don't exist without what you are calling the "environment". This makes it fundamentally different from light, which can travel through a vacuum. You can't just handwave away that fundamental physical difference.
No. I have not said that the limit is the same theory. What I claim is that an ether interpretation of field theoretic GR exists. It is the limit of Schmelzer's ether theory.PeterDonis said:By this criterion, General Relativity is the same theory as Newtonian mechanics, since "in the limit" it makes the same predictions.
It allows to construct for every solution of the equations various Doppler-shifted solutions. So it is a quite useful mathematical tool. Symmetries of the equations are always useful tools, even if they are only approximate symmetries.PeterDonis said:If your theory has a preferred frame, what's the point of even talking about Lorentz invariance--or any other kind of invariance, for that matter?
Sunil said:There is no reason and no base to construct probabilities in some different way. ##\rho(q)=|\psi(q)|^2## is a quite normal probability, it follows a continuity equation.
It follows a slightly different equation, but it is also a standard probability distribution, which is non-negative everywhere and has an integral of 1 over the whole configuration space. Qualitatively the same. It only changes differently. If you simply put ##\hbar=0## you get the classical equation.Tendex said:That's the quantum one which is different to the classical.
But ##\hbar\neq0##, and I don't want to put ##\hbar=0##, also "slightly different" is highly subjective, so I don't see the relevance of your answer besides pushing once more the dBB agenda. My point was that going back to a classical explanation(like using classical trajectories or ether preferred frame) doesn't fit very well with the change in procedure to obtain probabilities from just adding up to 1 absolute values of possible outcomes to adding up squares of numbers. It doesn't matter that we get nice good old probability distributions, it doesn't fit well either that the only answers are these irreversible probabilities unlike in the classical case, so I'd say that besides what Bell's theorem discards, it also hints that interpretations that just take the math of QM and varnish it with classical trajectories go nowhere.Sunil said:It follows a slightly different equation, but it is also a standard probability distribution, which is non-negative everywhere and has an integral of 1 over the whole configuration space. Qualitatively the same. It only changes differently. If you simply put ##\hbar=0## you get the classical equation.
This holds for the Schrödinger equation rewritten in "hydrodynamic" variables. With ##\hbar=0## the equations become classical, without the quantum potential.
Sure, I didn't mean there is no classical limit(in fact QM has a weird unexplained dependence on it), I was just highlighting the departure of that limit that's characteristic for QM.vanhees71 said:It's a bit sloppy to say ##\hbar=0##. What's really meant is to do an expansion in powers of ##\hbar##. Usually it's in the sense of "singular perturbation theory". It leads to the WKB approximation when applying "wave mechanics". Within the path-integral formalism the saddle-point approximation of the path integral for the propagator (or the corresponding generating functional or quantum action) is used to get equivalent results.
No, I simply meant that if you have written down the equations appropriately (continuity equation for ρ with the velocity defined by the gradient of the phase, and the phase following the quantum variant of the Hamilton-Jakobi equation) you can simply put ℏ=0 and obtain the unchanged continuity equation together with the classical Hamilton-Jacobi equation.vanhees71 said:It's a bit sloppy to say ##\hbar=0##. What's really meant is to do an expansion in powers of ##\hbar##. Usually it's in the sense of "singular perturbation theory". It leads to the WKB approximation when applying "wave mechanics". Within the path-integral formalism the saddle-point approximation of the path integral for the propagator (or the corresponding generating functional or quantum action) is used to get equivalent results.
As usual if somebody makes claims about my "agenda", the guess is wrong, I think there are better interpretations than dBB. If you don't see the relevance of my reply, then you may have a point, given that I also have not seen the relevance of your argument.Tendex said:But ##\hbar\neq0##, and I don't want to put ##\hbar=0##, also "slightly different" is highly subjective, so I don't see the relevance of your answer besides pushing once more the dBB agenda. My point was that going back to a classical explanation(like using classical trajectories or ether preferred frame) doesn't fit very well with the change in procedure to obtain probabilities from just adding up to 1 absolute values of possible outcomes to adding up squares of numbers. It doesn't matter that we get nice good old probability distributions, it doesn't fit well either that the only answers are these irreversible probabilities unlike in the classical case, so I'd say that besides what Bell's theorem discards, it also hints that interpretations that just take the math of QM and varnish it with classical trajectories go nowhere.
jambaugh said:Orthodox Copenhagen Interpretation
(Consciousness causes collapse because wave functions represent what we know about a quantum system. They are not analogues of the system's physical reality. Wave function collapse = "when we suddenly change what we know, we suddenly change what we know.")
How does Bell's inequality relate in any way to wave-function collapse? If you view wave functions as mathematical objects of the same nature as probability distributions over classical sets of states then note that they both collapse when we update our information due to observation.stevendaryl said:... But that is not consistent with Bell's inequality (unless we give up locality, or exploit one of the other loopholes).
I am gussing the link stevendaryl has in mind is if you consider the wave function collapse to "only" be a simple information update of the physicists ignorance, then that is exactly the line of thinking underlying Bells hidden variables. Ie. the information is out there, and preset, and its just the experimenet who is not informed.jambaugh said:How does Bell's inequality relate in any way to wave-function collapse?
I am sure we agree on all this.vanhees71 said:Within QT an observer has the most complete knownledge about a system, if he has prepared it in a pure state. You cannot have "more information" about the system.
jambaugh said:How does Bell's inequality relate in any way to wave-function collapse?
I think our main point of disagreement, is wether we think we can make scientitic progress by digging here or not.jambaugh said:This description of what happens is scraping the foundation of our fundamental understanding and there is no operationally meaningful way to dig deeper. It is as ill posed a question to speak about what goes on between or beneath this as it is to ask which twin is older in the classic relativistic paradox without defining a frame of reference
No need to apologize and you are not being ignorant.Zaitsev Maxim said:Sorry, if I'm being ignorant. I'm not a physicist. But I read in the book Beyond Weird, that even if we're sure that we're not influencing particle in any way during measurement, it changes its behaviour when we measure it. And it very strongly says that it's looking that's important. But is it really? Maybe it's measurement (some interaction) in itself that's important, not looking.
There must be a causal chain to make any measurement. Some causal chains interact with the subject prior to your participation (sunlight falling on an observable projectile), but some interaction must have occurred for you to measure that light. In this case you are using the light bouncing off the projectile to locate the projectile, but you must keep in mind the fact that the light DID interact and affect the projectile.Zaitsev Maxim said:(by the way I changed "some interaction" in "extraction of information" because we really shouldn't influence particle in any way)
But it's the very thing I'm trying to say. What if the cause of change is not observation of this information but simply inquiring about it? We don't measure it for oneselves, you can guarantee that you're not influencing particle (or else there would not be such absurd conjecture about looking) and we're not influencing it by looking or knowing something. If we do the same thing, but never know results of measurements (and never can extract them, if we extract then we're looking) and only look at the end result and it changes, then it is measurement, not looking, because we never looked or tried to understand what's going on. We're not measuring because we want to know result of our measurements, we measure because we should check influence of the act of measurement itself.ObjectivelyRational said:Something isolated and kept isolated from all external interaction is by definition unmeasurable while it is being kept isolated.