EPR experiments imply STR not correct?

[zenith8]

You're asking "how" it can happen in SR, but I don't know what sort of answer you're looking for if the ones I've given you aren't enough. There's no way to use an EPR experiment to synchronize two clocks at spacelike separation. There's no transfer of information, since the wave function isn't measureable. Alice, who does the first measurement, doesn't even use the same wavefunction to represent the state of the two-particle system after her measurement as Bob at the other end at the same time in a frame where Alice's measurement happens first. So it's up to you to explain why you think EPR implies absolute simultaneity. Why would it, when there's no instantaneous transfer of information (or any transfer of information for that matter)? And even if information had been transferred at infinite speed in one inertial frame, why do you assume that the speed is infinite in all inertial frames?

OK. Consider a deterministic hidden-variables theory - de Broglie-Bohm pilot-wave theory, say. There are particles as well as the waves, and the particles follow the stream lines of the ordinary QM probability current. No extra equations. It's just QM.

Under ordinary circumstances (particles distributed as psi^2) you can't send instantaneous signals - even though when you measure spin-up then an instantaneous signal passes to the distant arm saying "You're spin down" - it is the case that there is no effect on the expectation values or on the probabilities. The statistical distribution of properties at one end are just the normal ones. and this masks any signalling. So quantum nonlocality cannot in fact be used for practical signalling at a distance. This means that if there were a preferred rest frame, it would be undetectable in practice.

But this isn't a fundamental constraint. From the hidden-variables perspective, it's a peculiarity of a special 'quantum equilibrium' distribution of the particles. The fact we can't detect the rest frame is not an uncomfortable conspiracy seemingly built into the laws of physics - it's just an accident of our living in a state of quantum equilibrium, whose statistical noise masks the underlying nonlocality.

If you do the analysis, hypothetical non-equilibrium distributions (particle distribution not equal to psi^2) do make it possible to use non-locality for instantaneous signalling (just like in stat mech, differences of temperature make it possible to convert heat into work). Proof slightly boring but obvious - trust me for the moment

So to synchronize clocks:

If experimenters at space time events A and B had access to non-equilibrium systems entangled between A and B, then they would be able to signal back and forth to each other instantaneously. In an arbitrarily short time (as measured at each wing) a long conversation could in principle take place, during which (for example) the experimenters agree to set their clocks to read time t=0. They could signal to each other to confirm that they did do this. In such conditions A and B have to be considered as simultaneous events, and the agreed-upon time variable would define an absolute simultaneity. Thus, using non-equilibrium matter, experimenters at remote locations could set their clocks to read the same instantaneous time.

This is true, even though practical difficulties might prevent us from *actually* doing the experiment. It raises the question of how these signals could mesh with the surrounding approximately classical spacetime. This question must have an answer , irrespective of the underlying microscopic theory of spacetime.

Now you might say, well - what if the two wings are in motion relative to each other. So synchronize the clocks at t=0, and then let one of them accelerate and go on a tour then come back to where it was. The clock readings will no longer be the same since the accelerated clock will have slowed down. But this doesn't matter - remember we know have an absolute time - the final clock readings will still be simultaneous events (as could be verified by non-local communication) yet, the readings will not be synchronous.

Note - and this is the fun bit - that if you synchronize your distant clocks by non-local signalling, then the speed of light will be measured to be isotropic *only* in the preferred rest frame. Recall that moving experimenters who assume that the speed of light is still c in all directions would adjust their clocks at different points in space with settings that differ by the term -vx/c^2 (to lowest order in v/c) - see Poincare. In quantum equilibrium, of course, such non-local signalling is impossible and the true rest frame can't be detected.

Which I think explains what you chaps were grumbling about earlier this evening.

Did I get anywhere?

Zenith.

 

[Mentz114]

EPR in SR - instantaneous signalling

The diagram has distance x on the horizontal axis and time t on the vertical. We see the worldlines of 3 observers who synchronise clocks and then part company. We are on the green ship so our worldline is vertical. At time Tau-green we send an instantaneous signal to red and blue. At the same time we send a light pulse ( yellow ). If red and blue recorded the time of arrival of the instant signal, we can then compare clock times, velocities and positions and calculate that indeed, the signal had taken no time on anyone's clock. Also notice that the white line, if extended will cut all observers worldlines. Furthermore, because all the taus are proper intervals, all inertial observers will agree on the clock times.
An observer not in on our deliberations wouldn't be able to tell who had originated the signal.
As far as I can see, there are no contradictions in this. No doubt you will tell me if there is one.

However, a more interesting thing occurs to me. Length contraction may be attributed to the impossibility of detecting both ends of a moving rod simultaneously. So if we could do this, there would be no length contraction and both SR and Lorentz relativity would be wrong, or at least irrelevant.

 

[atyy]

Quantum Information and Relativity Theory
Asher Peres, Daniel R. Terno
http://arxiv.org/abs/quant-ph/0212023

 

[Fredrik]

Under ordinary circumstances (particles distributed as psi^2) you can't send instantaneous signals
...
If you do the analysis, hypothetical non-equilibrium distributions (particle distribution not equal to psi^2) do make it possible to use non-locality for instantaneous signalling

I have no idea what this is supposed to mean. |\psi(x,t)|^2 is the probability density of finding the particle in a region of space near x at time t. If it isn't, it isn't QM.

 

[zenith8]

I have no idea what this is supposed to mean. |\psi(x,t)|^2 is the probability density of finding the particle in a region of space near x at time t. If it isn't, it isn't QM.

Yes, it is. You said in your earlier post that interpretations of QM don't matter - now you're saying the opposite. What I'm saying here is just the standard mathematics with a perfectly standard hidden variables interpretation.

The Schrodinger equation of 1926 is set up as if particles existed all the time (wave function depends on position of all the particles, the Hamiltonian has Coulomb interactions between point particles etc.). De Broglie set up his pilot-wave hidden variables theory of 1924-1927 along those lines - there were particles, and the Schrodinger wave 'guided' the particles as they move along the streamlines of the probability flow which explains the double slit experiment. Note the whole concept of a wave function was de Broglie's in the first place - using it to predict electron diffraction through a slit was what he got the Nobel prize for.

(Note that this is mathematically identical to what is normally called Bohmian mechanics or the Bohm interpretation - all Bohm did was add decoherence to de Broglie's original pilot wave theory in order to explain measurement).

So anyway, in a spirit of positivism fashionable at the time, Heisenberg and the others then claimed that particles didn't exist unless you measure them. So they then changed the meaning of the word probability to mean 'probability of finding the particle at point x in a suitable position measurement' instead of its original meaning of 'probability of the particle being at x'. This leads to essentially all the features of QM that are normally considered paradoxical, but that's by the by. This is the only difference between the standard QM viewpoint and the hidden variables viewpoint. It's the same mathematics, different interpretation.

In presentations of de Broglie-Bohm theory, it's normally said that there is an extra equation - the guidance equation - where the velocity is given by v = grad S, where S is the phase of the Schrodinger wave. In fact this is just the ordinary probability current over the density from the standard theory - again, the particles are following the streamlines of probability flow.. So there isn't an extra equation at all.

If you believe that particles and waves are logically separate entities then their distribution in space does not have to have any relation to each other. However, because the wave guides the particles then there is a natural 'equilibrium distribution' analagous to the ones in classical stat mech. That equilibrium distribution is found (by numerical simulations, or by maths) to be the square of the wave function. Now in standard QM the relation 'probability = psi^2' is simply given, with no reason or explanation - in hidden variables theories it has a causal explanation.

In extreme conditions (the early universe for example) it is postulated - see papers by Antony Valentini ,for example - that one can find non-equilibrium matter where p is not equal to psi^2, in which case non-local signalling becomes possible, as I've already stated.

This may sound like nutter stuff to you, but it's perfectly standard. You've just been conditioned to think from a positivist viewpoint just like Bohr told you to (note the view isn't even correctly applied here, as it is the wave function which is not measurable; the particle positions are!).

Anyway, given that such signalling is possible (i.e. in theory, ignoring practical problems) one then must consider the implications of instantaneous signalling for the ontology of space and time, which I believe is the point of this discussion.

Remember again, it is standard QM. If you don't believe that, you need to do some reading.

Zenith

 

[zenith8]

The diagram has distance x on the horizontal axis and time t on the vertical. We see the worldlines of 3 observers who synchronise clocks and then part company. We are on the green ship so our worldline is vertical. At time Tau-green we send an instantaneous signal to red and blue. At the same time we send a light pulse ( yellow ). If red and blue recorded the time of arrival of the instant signal, we can then compare clock times, velocities and positions and calculate that indeed, the signal had taken no time on anyone's clock. Also notice that the white line, if extended will cut all observers worldlines. Furthermore, because all the taus are proper intervals, all inertial observers will agree on the clock times.
An observer not in on our deliberations wouldn't be able to tell who had originated the signal.
As far as I can see, there are no contradictions in this. No doubt you will tell me if there is one.

As you wish. You are claiming this shows you can have EPR in SR where all inertial frames are equivalent. Then your arrangement is not relevant as you need to have two different lines of simultaneity (supposedly equivalent inertial frames) to show up the paradox.

So just have your red and green ships (forget the blue one) and have them travel at the same speed with respect to each other. They have a non-equilibrium EPR device to communicate with each other instantaneously, and each ship is rigged to flash its own colour in ordinary light when it either sends or receives such a signal.

Then let *my* ships, which are pink and purple should you ask, be traveling at the same speed as each other, but with a different speed to the red and green ones. They also have instantaneous EPR transmitters to communicate with each other.

Because these two pairs of spaceships are traveling at different speeds, their lines of simultaneity are tilted with respect to each other. Let the green ship transmit instantaneously to the red one, and arrange that pink is somewhere near red in space. If you arrange it so that pink transmits instantaneously to purple as soon as he sees the red ship flash red, then you could arrange the tilt such that the original green ship instantaneous transmission is still in the future of pink and purple on the occasion of the pink instantaneous transmission. So if the purple ship is anywhere near you and your green ship in space when he receives the transmission from pink, then he can arrange to blow you and your green ship out of the sky with a photon torpedo before you even sent out the original signal. In which case.. you fill in the rest..

Only way out of this is to have all EPR correlations occur in a single unique reference frame - the absolute space, ether, whatever.

Zenith

 

[Fredrik]

Yes, it is. You said in your earlier post that interpretations of QM don't matter - now you're saying the opposite.

You obviously need postulates that tell you how to interpret the mathematics as predictions about the results of experiments. What I just said about |\psi|^2 is such a postulate. The "interpretations" of QM deal with a different set of issues, like e.g. the question of whether the terms in a superposition represent "different worlds" or not. What I was trying to say earlier is that there's no need to consider those questions here.

(I have a lot of opinions about "interpretations" of QM, but I won't post them here. I might however start another thread in the philosophy subforum soon).

I don't know the Bohm theory very well, so I can't comment on every detail of what you said, but there's definitely nothing in the standard formulation of QM that let's you use the EPR effect to synchronize clocks at events with spacelike separation. If there's something in Bohm's theory that let's you do that, then it can't be described as an "interpretation" of QM, or even as a "physically equivalent theory". It would be a different theory altogether.

If it isn't a completely different theory, then you should be able to use the standard formulation of QM to make your case for absolute simultaneity.

 

[zenith8]

You obviously need postulates that tell you how to interpret the mathematics as predictions about the results of experiments. What I just said about |\psi|^2 is such a postulate. The "interpretations" of QM deal with a different set of issues, like e.g. the question of whether the terms in a superposition represent "different worlds" or not. What I was trying to say earlier is that there's no need to consider those questions here.

(I have a lot of opinions about "interpretations" of QM, but I won't post them here. I might however start another thread in the philosophy subforum soon).

I don't know the Bohm theory very well, so I can't comment on every detail of what you said, but there's definitely nothing in the standard formulation of QM that let's you use the EPR effect to synchronize clocks at events with spacelike separation. If there's something in Bohm's theory that let's you do that, then it can't be described as an "interpretation" of QM, or even as a "physically equivalent theory". It would be a different theory altogether.

If it isn't a completely different theory, then you should be able to use the standard formulation of QM to make your case for absolute simultaneity.

Well - as I said, the Bohm theory in fact follows from the usual theory by a single change in the meaning of one word (though I must say this is not widely appreciated, due to silly ways of presenting it common in the past). If you choose to say that this gives a different theory, instead of a different interpretation, well then it's your choice.

I say it's the same mathematics therefore it's the same theory. The change in the meaning of the word just gives the theory different implications, that's all. One of which is superluminal signalling.

Anyway, the question of whether one can get superluminal correlations is not in doubt (discarding my original four unlikely get-out-clauses, or whatever people have subsequently made of them). It seems to me that elevating this to the question of whether one can exploit the phenomenon to send messages is kind of missing the point. OK - in some ways of looking at it - then sending instantaneous messages is perfectly possible - in some other ways it's not possible. But the very existence of superluminal correlations has implications for spacetime structure, irrespective of who's right about the messages.

Zenith

PS: and what you said was a 'postulate' - p=psi^2. Well with my change in the meaning of a word, I can derive that postulate. So it's fundamental status as a postulate is not God-given.

 

[Fredrik]

It seems to me that elevating this to the question of whether one can exploit the phenomenon to send messages is kind of missing the point. OK - in some ways of looking at it - then sending instantaneous messages is perfectly possible - in some other ways it's not possible. But the very existence of superluminal correlations has implications for spacetime structure, irrespective of who's right about the messages.

If you can't use these correlations to synchronize clocks, then there are no implications for spacetime structure.

 

[zenith8]

If you can't use these correlations to synchronize clocks, then there are no implications for spacetime structure.

Whether or not that is true, I don't care. I'm interested in the following question. Given that in at least some interpretations of QM (all 'hidden variables' ones now I think of it) one can in principle exploit nonlocality to send instantaneous messages, what implications does this have for spacetime structure?

Dear me, it seems a perfectly reasonable question to ask.

 

[atyy]

Whether or not that is true, I don't care. I'm interested in the following question. Given that in at least some interpretations of QM (all 'hidden variables' ones now I think of it) one can in principle exploit nonlocality to send instantaneous messages, what implications does this have for spacetime structure?

Dear me, it seems a perfectly reasonable question to ask.

Hmmm, so does relativistic Bohmian QM make different predictions than relativistic "Copenhagen" QM? I haven't read this but it looks interesting:

Probability in relativistic Bohmian mechanics of particles and strings
H. Nikolic
http://arxiv.org/abs/0804.4564

 

[Fredrik]

Whether or not that is true, I don't care. I'm interested in the following question. Given that in at least some interpretations of QM (all 'hidden variables' ones now I think of it) one can in principle exploit nonlocality to send instantaneous messages, what implications does this have for spacetime structure?

Dear me, it seems a perfectly reasonable question to ask.

If you can send instantaneous messages, then you can obviously use them to synchronize clocks. So you should care. And you didn't just just ask the question. You also answered it, and claimed that your argument proves that you're right. But those claims are useless unless you can describe a way to synchronize clocks at events with spacelike separation.

 

[zenith8]

If you can send instantaneous messages, then you can obviously use them to synchronize clocks. So you should care. And you didn't just just ask the question. You also answered it, and claimed that your argument proves that you're right. But those claims are useless unless you can describe a way to synchronize clocks at events with spacelike separation.

Did I not do that in my earlier message 51?

Zenith

 

[cesiumfrog]

Sure. I knew f*ck all about relativity this time last week. [..] PS: Any smartarse saying 'and you still don't' in response to my first sentence can expect a quick unpleasant death.

Right.. so what is your intention this week? Is it just to double your understanding of physics, or are you really expecting to prove the expert consensus of physics is wrong?

You said in your earlier post that interpretations of QM don't matter - now you're saying the opposite. What I'm saying here is just the standard mathematics with a perfectly standard hidden variables interpretation. [..] Remember again, it is standard QM. If you don't believe that, you need to do some reading.

That is false, and is also offensive. To put this into your language: Bohm's theory is only an interpretation of QM when you assume "equilibrium distribution". Any other distribution constitutes a different theory, and can result in predictions that contradict standard QM. There isn't any experimental evidence to support your "Bohmian mechanics with nonequilibrium matter" theory.

Moreover, you think your theory allows you to derive the distribution (which is a postulate of other interpretations), but you have not done such a thing: please supply us with the proof that a particle riding on a pilot-wave will eventually adopt a probability distribution corresponding with the wave intensity, and then maintain that distribution throughout experiments that disturb the pilot-waveform.

You've also ignored the point that standard QM has successfully been incorporated with SR (and to an extent GR) as QFT. Contrary to your implication, this theory is not inconsistent (in fact it is well verified experimentally), and furthermore Bohm's interpretation has not been similarly fruitful. (Understand that in physics we wouldn't even care if it were ontologically correct, whatever that really means, the goal is merely improving our ability to predict experimental results and create useful technology.)

Anyway, the question of whether one can get superluminal correlations is not in doubt (discarding my original four unlikely get-out-clauses, or whatever people have subsequently made of them). It seems to me that elevating this to the question of whether one can exploit the phenomenon to send messages is kind of missing the point. OK - in some ways of looking at it - then sending instantaneous messages is perfectly possible - in some other ways it's not possible. But the very existence of superluminal correlations has implications for spacetime structure, irrespective of who's right about the messages.

Superluminal correlations are as mundane as shadows (as of a moth near a candle and distant from two points on a wall).

Remind me, did you ever cite a peer-reviewed source for your claim of an absolute reference frame?

 

[zenith8]

Right.. so what is your intention this week? Is it just to double your understanding of physics, or are you really expecting to prove the expert consensus of physics is wrong?

You're wasted away from the education world mate. The kids would love you..

That is false, and is also offensive. To put this into your language: Bohm's theory is only an interpretation of QM when you assume "equilibrium distribution". Any other distribution constitutes a different theory, and can result in predictions that contradict standard QM. There isn't any experimental evidence to support your "Bohmian mechanics with nonequilibrium matter" theory.

And yet all the new implications I'm talking about come from a single change in the meaning of a single word and precisely the same mathematics. It's not offensive, it's fascinating!

Moreover, you think your theory allows you to derive the distribution (which is a postulate of other interpretations), but you have not done such a thing: please supply us with the proof that a particle riding on a pilot-wave will eventually adopt a probability distribution corresponding with the wave intensity, and then maintain that distribution throughout experiments that disturb the pilot-waveform.

It's a bit like the wind stirring particles in the atmosphere.

Look, if you must, see any or all of the following papers, most of which address the issue directly or indirectly. Try Goldstein + Struyve 2007 for starters. Some of them propose experiments. The Valentini and Westman one from 2004 even has some nice pictures from numerical simulations for you to admire.. Go on, read that one first.

* Quantum equilibrium and the origin of absolute uncertainty, D. Durr, S. Goldstein and N. Zanghi (2008)
* De Broglie-Bohm pilot-wave theory: many worlds in denial?, A. Valentini (2009).
* Inflationary cosmology as a probe of primordial quantum mechanics A. Valentini (2008).
* De Broglie-Bohm prediction of quantum violations for cosmological super-Hubble modes, A. Valentini (2008).
* Astrophysical and cosmological tests of quantum theory, A. Valentini (2007).
* On the uniqueness of quantum equilibrium in Bohmian mechanics, S. Goldstein, W. Struyve (2007)
* On the distribution of the wave function for systems in thermal equilibrium, S. Goldstein, J. L. Lebowitz, R. Tumulka, and N. Zanghi. (2006)
* Smoothness of wave functions in thermal equilibrium, R. Tumulka and N. Zanghi (2005).
* Universal signature of non-quantum systems, A. Valentini (2004)
* Dynamical origin of quantum probabilities A. Valentini and H. Westman (2004)
* Extreme test of quantum theory with black holes, A. Valentini (2004)
* Black holes, information loss and hidden variables, A. Valentini (2004).
* Quantum equilibrium and the role of operators as observables in quantum theory, D. Durr, S. Goldstein, N. Zanghi (2003)
* Signal-locality in hidden-variables theories A. Valentini (2002)
* Subquantum information and computation, A. Valentini, Pramana - Journal of Physics, 59, 269 (2002).
* Hidden variables, statistical mechanics and the early universe, A. Valentini (2001)
* The distribution postulate in Bohm's theory, J.A. Barrett (1995)
* Quantum mechanics, randomness, and deterministic reality, D. Durr, S. Goldstein, and N. Zanghi (1992).
* Quantum equilibrium and the origin of absolute uncertainty, D. Durr, S. Goldstein and N. Zanghi (1992).
* Signal-locality, uncertainty, and the subquantum H-theorem (I and II) A. Valentini (1991).
* Proof that probability approaches $\Psi^2$ in causal interpretation of quantum theory, D. Bohm (1953).
* On the pilot-wave theory of classical, quantum, and subquantum physics, Antony Valentini's Ph.D. thesis (1992).

Sorry, I only have the titles in my files and can't be bothered typing in the exact references, but you should be able to find most of them by Googling..

You've also ignored the point that standard QM has successfully been incorporated with SR (and to an extent GR) as QFT. Contrary to your implication, this theory is not inconsistent (in fact it is well verified experimentally), and furthermore Bohm's interpretation has not been similarly fruitful. (Understand that in physics we wouldn't even care if it were ontologically correct, whatever that really means, the goal is merely improving our ability to predict experimental results and create useful technology.)

I think I touched on this in an earlier response. It's a tricky issue, but it doesn't imply that all Bohmians should immediately go and kill themselves..

Superluminal correlations are as mundane as shadows (as of a moth near a candle and distant from two points on a wall).

So you say. I think they're fascinating. Don't you find the idea that the wavefunction binding distant particles into a single irreducible reality even slightly interesting? What a funny fellow you are.

Remind me, did you ever cite a peer-reviewed source for your claim of an absolute reference frame?

No need. I've explained it myself. The chaps have been doing a great job debunking my argument. Especially Mentz114. Not.

But do keep up. I could cite Bell "Speakable and Unspeakable in Quantum Mechanics" p. 171, 194 or indeed, the recent entire book full of articles devoted to precisely this point. See "Einstein, Relativity, and Absolute Simultaneity", Routledge (2008).

As it says in the introduction to the latter one: "Almost all the contributors are convinced that the received view that simultaneity is not an absolute relation is not only unwarranted but false"

So I'm not a lone nutter. The world appears to be full of them.

Thanks for the friendly support! Love you. Mmmwah.

 

[Mentz114]

The chaps have been doing a great job debunking my argument. Especially Mentz114. Not.

Thanks. I admit that instantaneous information transmission can result in the type of causal paradox you cite. Now you'll have to get all pedagogical and explain why the same scenario can't exist in Lorentzian relativity ?

I can't get my head around 'instantaneous' at all. Rather like dividing by zero, I suspect it's a fallacious idea.

 

[Fredrik]

Did I not do that in my earlier message 51?

Are you seriously asking? The answer is of course no. You didn't even come close. Your recipe for synchronization of clocks is to use instantaneous messages, but you didn't describe how to send or receive those messages. All you said was that it has something to do with a particular interpretation of QM and something not being in equilibrium.

 

[zenith8]

Are you seriously asking? The answer is of course no. You didn't even come close. Your recipe for synchronization of clocks is to use instantaneous messages, but you didn't describe how to send or receive those messages. All you said was that it has something to do with a particular interpretation of QM and something not being in equilibrium.

Oh God, you're just impossible aren't you.

"something to do with"
"something not being"
I know you can't be bothered to bothered to read the literature about this (and to be honest, I can hardly blame you) or even to read what I've written in previous posts here, but you shouldn't use your unwillingness to study the concept as a physical argument against the point I'm trying to make.

The implication of possible non-local signalling occurs in all deterministic hidden variables theories - as has been well known for 20 years. A clear proof is given in the Valentini article in the recent book 'Einstein, Relativity and Absolute Simultaneity" p. 137 - available on Google Books,

We have been round this circle several times now. Given that a coherent proposal entirely consistent with the mathematics of standard QM for instantaneous signalling *exists*, then let us *assume* it can be done in the way suggested, and examine the consequences of this for spacetime structure.That's all I'm asking.

For that purpose it's irrelevant whether the signalling is technically feasible in an engineering sense, or whether the Bohmian interpretation has anything to do with reality, or that the argument doesn't involve your favourite picture of QM.

Zenith

PS: MWI right?

 

[cesiumfrog]

Are you seriously asking? The answer is of course no. You didn't even come close. Your recipe for synchronization of clocks is to use instantaneous messages, but you didn't describe how to send or receive those messages. All you said was that it has something to do with a particular interpretation of QM and something not being in equilibrium.

It's almost as if a MWI adherent was arguing that not only do parallel realities exist, but that it must also be physically possible to communicate between these realities, and the fact that no advanced parallel civilisation has done so to date proves that evolution is false and the multiverse has only existed for 10,000 years.

Even if Bohmian mechanics were true (despite it being otherwise demonstrated less fruitful to date), and even if the existence of non-equilibrium states does permit instantaneous messaging (which I'll take as given), and even if an absolute reference frame was the physically preferred way to mitigate paradoxes in such a situation (rather than an obvious alternative such as the block-universe which is consistent with modern GR), Zenith has still forgotten to give strong evidence for the extraordinary claim that nonequillibrium matter can actually exist.

 

[Dale]

Hi zenith8, I see that this thread is running fast and there have been a lot of posts in the interim, so I apologize if this has already been covered and you now understand the scientific error that you were making here.

I'm not patently wrong at all. The experimentally verifiable facts are as follows: the space and time coordinates of events, measured in any inertial reference system, are related to the space and time coords of the same events, as measured in any other inertial reference system, by the Lorentz transformations.

The mathematics of this is indeed the same no matter what interpretation you adopt.

Precisely. And because the equations are the same both Lorentz and Einstein make the exact same quantitative prediction for any possible experimental test of the theories.

So my basic point is that the experimental evidence (nonlocality) now allows you to distinguish between the interpretations - without, indeed, changing any of the mathematical predictions of the theory.

This is where you are patently wrong. This appears to simply be a rather severe misunderstanding of the scientific method.

A theory makes a specific prediction about the quantitative value of some specific measurement in a proposed experimental setup. That experiment is then performed and the measured result either agrees or disagrees with the quantitative prediction to within some obtained accuracy. If the experimentally measured value agrees with the quantitative prediction then that is taken as evidence in support of the theory as a whole and the experiment is said to verify the theory. On the other hand, if the experimentally measured value disagrees with the quantitative prediction then that is taken as evidence in opposition to the theory and the experiment is said to falsify the theory.

If two theories always produce the same mathematical predictions then it is simply logically impossible for any experiment to verify one and falsify the other (because X and ~X is self contradictory). In fact, in such cases the two theories are usually not considered to be separate theories, but instead are typically considered to be two interpretations of a single theory. Again, if theories A and B both predict measurement C in experiment D then it is patently impossible for experiment D to both obtain C in agreement with A and also ~C in disagreement with B.

Lorentz and Einstein have different ontologies - statements about what is real - and these can be experimentally distinguished if you have evidence for a preferred frame.

Of course Lorentz and Einstein have different ontologies. But ontologies are not experimentally testable. The only thing that is accessible to experimental evidence is the result of measurements, on which point Lorentz and Einstein agree entirely. The Lorentzian aether is, by design, not experimentally measureable, it is, by design, an undetectable ontological entity.

Again, I don't care if you prefer Lorentz over Einstein, but there is no experimental evidence to justify that preference. There is also no experimental evidence to refute that preference either. They are not really different theories, but only different interpertations of the Lorentz transforms.

 

[zenith8]

It's almost as if a MWI adherent was arguing that not only do parallel realities exist, but that it must also be physically possible to communicate between these realities, and the fact that no advanced parallel civilisation has done so to date proves that evolution is false and the multiverse has only existed for 10,000 years.

It isn't in the least like that. You just wrote that because it sounds cool (if anyone lurking in these forums can ever said to be so).

Even if Bohmian mechanics were true (despite it being otherwise demonstrated less fruitful to date), and even if the existence of non-equilibrium states does permit instantaneous messaging (which I'll take as given), and even if an absolute reference frame was the physically preferred way to mitigate paradoxes in such a situation (rather than an obvious alternative such as the block-universe which is consistent with modern GR), Zenith has still forgotten to give strong evidence for the extraordinary claim that nonequillibrium matter can actually exist.

Given your first three ifs to be true - as you state - then in reality it would be a more extraordinary claim - indeed a fantastical one - to suggest that nonequilibrium matter cannot exist. Hidden variables theories of this nature are nothing other than a statistical mechanics of waves and particles, with particular underlying laws of dynamics (which differ from the classical ones). No one goes around saying that it is impossible for classical particles to not be distributed according to the Boltzmann distribution. Why on Earth would you say the same in the quantum case? Baffling.

Zenith

 

[Mentz114]

Zenith,
If we could we use the instantaneous signalling to broadcast a universal absolute time signal, this would enable anyone to detect their absolute motion ( ie wrt the preferred frame) by comparing their clock rate to the absolute clock. So another cornerstone of relativity is undermined by instantaneous transmission.

Also please explain soberly why an absolute clock or reference frame would prevent observers seeing contradictory outcomes ? The contradictions are not because of the particular ST model, but the instantaneity.

In spite of your triumphal tone and supercilious remarks - you have not made your case.

M

 

[zenith8]

Zenith,
If we could we use the instantaneous signalling to broadcast a universal absolute time signal, this would enable anyone to detect their absolute motion ( ie wrt the preferred frame) by comparing their clock rate to the absolute clock. So another cornerstone of relativity is undermined by instantaneous transmission.

Indeed. And the existence of nonlocality does undermine the epistemological and ontological basis of STR, as you state. You're beginning to sound like a Lorentzian.

Also please explain soberly why an absolute clock or reference frame would prevent observers seeing contradictory outcomes ? The contradictions are not because of the particular ST model, but the instantaneity.

OK. The backwards in time paradoxes indeed require the structure of spacetime to be Minkowskian (as we have seen with your spaceship).

If instead we have a given preferred frame with standard Lorentzian global coordinates x,y,z,t instantaneous signalling between distant spaceships would not in itself be problematic in that frame. But what about the Lorentz transformation? You migh be disturbed by the idea that by moving along the x-axis you could 'see' such signals propagating 'backwards in time'. But in reality you are not 'seeing' the global time of the Lorentz frame. Rather, you have a collection of clocks distributed over space, and these have to be *set* according to some procedure. The time associated with an event occurring at some point in space is just the reading of the clock in the neighbourhood of that event. If an event B is for some physical reason regarded as 'causing' a spatially distant event A (e.g. a message is sent from B to A) and if the reading of a clock at B is larger than the reading of a clock at A, then before declaring this paradoxical you ought to ask how the clocks at A and B were set in the first place.

If you choose Einstein's so-called 'synchronization' using light pulses whose speed is taken to be isotropic, then at (global) time t the moving clock located at x,y,z, will read a time t' = t-vc/x^2 / sqrt(1-v^2/c2). The interpretation of this formula is simple. The moving clocks distributed along x>0 have been initially set to read progressively earier times, with a lag proportional to x; while the moving clocks along x<0 have been similarly set to read later times.

These settings have been chosen precisely so as to make a light pulse (with speed c in the global frame) appear to have a speed c, along both +x and -x in the moving frame. This is the origin of the term -vx/c^2 (to lowest order in v/c). If you include the effect of motion which slows clocks down you also get the fact 1/sqrt(1-v^2/c^2).

With this convention we have the following peculiarity: an instantaneous signal propagating along x in the global frame appears to be going 'backwards in time' as judged by the moving clocks with settings t'.
However, this is *not* mysterious or paradoxical. It is exactly the same as "jet lag" if you're on a flight round the world. Clocks on the Earth's surface have been set according to a convention based on the locally observed position of the Sun in the sky, and it is no way surprising that an airplane passenger can formally 'travel backwards in time' with respect to them.

That's the difference.

In spite of your triumphal tone and supercilious remarks - you have not made your case.

If you say so..

Zenith.

 

[zenith8]

I have no issue with anything you wrote, except the following:

Of course Lorentz and Einstein have different ontologies. But ontologies are not experimentally testable. The only thing that is accessible to experimental evidence is the result of measurements, on which point Lorentz and Einstein agree entirely. The Lorentzian aether is, by design, not experimentally measureable, it is, by design, an undetectable ontological entity.

Again, I don't care if you prefer Lorentz over Einstein, but there is no experimental evidence to justify that preference. There is also no experimental evidence to refute that preference either. They are not really different theories, but only different interpertations of the Lorentz transforms.

Ontologies are experimentally testable.

It is completely obvious that one can have experimental evidence which disproves an ontological or epistemological supposition. The ontology for a given theory is simply a statement of what is supposed to be real or to 'exist' in that theory (it has nothing to do with whatever is the ultimate reality in the real universe, which there is no way of knowing for certain, as we may be in the Matrix, and of course our theory is almost certainly not the Final Theory of Everything).

For instance if am a fourteenth-century astronomer I may posit as my astrophysical ontology that the Moon and all other heavenly bodies are made of cheese. There was no way at the time anyone could prove me wrong, so in time the Zenith Cheese Theory became big news. Now they may beg to differ.

Relativity is an excellent example of this. If someone turns out to be discover experimental evidence for a preferred frame, then Einsteinian STR - which says that there is no such frame and all frames are equivalent - will have been falsified. One might choose then to replace Einsteinian STR with Lorentzian relativity which *is* compatible with a preferred frame - but you are claiming this differs in no way that is testable from Einstein, which is surely not correct. The nonlocality people are claiming that they have found evidence for such a preferred frame - you need to be arguing with them, not about semantics..

Zenith

 

[Mentz114]

Zenith,

OK. The backwards in time paradoxes indeed require the structure of spacetime to be Minkowskian (as we have seen with your spaceship).

That example doesn't rule out paradoxes in different models of spacetime. Just because one thing is square doesn't mean something else can't be. I assert that the paradoxes are caused by instantaneous transmission.

But what about the Lorentz transformation?

What indeed. Are you saying that the LT also fits between observers in Lorentz relativity ? If so, obviously the same paradoxes could be arranged.

The rest of what you've written doesn't seem to address the issue.

Indeed. And the existence of nonlocality does undermine the epistemological and ontological basis of STR, as you state. You're beginning to sound like a Lorentzian.

Nonsense. I reject your ideas. You are prejudging the way nature works because you have an agenda, and you think the vague kind of non-locality arguments help you with it. I doubt if any kind of signalling as we think of it occurs in the quantum non-local phenomena. They can more easily be explained by using some small dimensions, which is a lot more believable than your interpretation with it's emphasis on absolutism, and impossible instantaneous transmission.

There's a lot more out there than in your philosophy, Zenith.

 

[Fredrik]

The implication of possible non-local signalling occurs in all deterministic hidden variables theories - as has been well known for 20 years. A clear proof is given in the Valentini article in the recent book 'Einstein, Relativity and Absolute Simultaneity" p. 137 - available on Google Books,

Page 137 mentions "instantaneous signaling at the statistical level", not "instantaneous messages". What makes you interpret what they're saying as a claim that you can send instantaneous messages this way? As far as I can tell (after only skimming it), they do not claim that you can send even a single bit of information this way, at least not on pages 137-138. (Pages 139-140 aren't included in the preview).

Given that a coherent proposal entirely consistent with the mathematics of standard QM for instantaneous signalling *exists*, then let us *assume* it can be done in the way suggested, and examine the consequences of this for spacetime structure.That's all I'm asking.

That doesn't make any sense. The "given" part is false, and you haven't suggested any way to send those messages, so the words "in the way suggested" refer to something undefined.

You've been doing more than asking that. You've been claiming not only that QM implies absolute simultaneity (because of EPR), but also that you have already proved that claim in this thread. Both of those claims are false.

For that purpose it's irrelevant whether the signalling is technically feasible in an engineering sense, or whether the Bohmian interpretation has anything to do with reality

I agree 100% (and I don't think I've given you a reason to believe that I wouldn't agree with this). It is however extremely relevant if you can come up with a thought experiment in which a single-bit message can be sent and received at events with spacelike separation. In fact, that would be the only way to prove your claim.

MWI right?

I don't have a favorite interpretation. Actually I think almost everything that's ever been said about interpretations of the standard formulation of QM is irrelevant nonsense. I don't think we should be talking about "interpretations" at all. I think we should be talking about a set of theories that may or may not be equivalent. (I'd like to define two theories to be "mathematically equivalent" if the axioms of either theory can be derived from the axioms of the other, and "physically equivalent" if they make the same predictions about the results of experiments). I will only be able to take the MWI seriously if I see a list of statements that defines it in a way that makes it a theory according to my definition of "theory". I know very little about Bohm, but the impression I have is that it can be expressed in the form of a "theory", so I'm less skeptical of Bohm than of the MWI.

My definition of "theory"? Short version: A set of unambiguous statements that tell us how to calculate probabilities of logically possible results of experiments. The set must also be finite, logically consistent, and not contain any statements that can be removed without changing or removing some of the predictions about the probabilities.

 

[Dale]

Ontologies are experimentally testable.

No they are not. Only predictions of measurements are experimentally testable. If think you have developed an ontologometer in your garage then you should start manufacturing and selling them. Nobody else has one so you will corner the entire market.

If someone turns out to be discover experimental evidence for a preferred frame, then Einsteinian STR - which says that there is no such frame and all frames are equivalent - will have been falsified. One might choose then to replace Einsteinian STR with Lorentzian relativity which *is* compatible with a preferred frame - but you are claiming this differs in no way that is testable from Einstein, which is surely not correct.

Again, you are not understanding science and logic. Lorentz is not compatible with just any arbitrary preferred frame, it must work according to the Lorentz transform. Lorentz is thus only compatible with an experimentally undetectable aether. Therefore, if you do find experimental evidence of a preferred frame then you will have falsified both Einstein (who says there is no preferred frame) and Lorentz (who says it is experimentally undetectable). Again, Lorentz and Einstein both use the same Lorentz transform to make all of their experimental predictions so any experimental result that falsifies one will necessarily falsify the other.

 

[zenith8]

Here's an article published yesterday that is relevant to this discussion.

http://www.sciam.com/article.cfm?id=was-einstein-wrong-about-relativity&print=true"

Zenith

 

[Dale]

First, Scientific American is a popular magazine, not a peer-reviewed journal (not even on the minimal level of arXiv), so take it for what it is. Second, nothing in that article contradicts my point that Lorentz's aether theory and Einstein's special relativity are completely experimentally indistinguishable, nor does anything in the article support your assertion that EPR provides experimental evidence that verifies Lorentz and falsifies Einstein.

You simply cannot make such a choice based on experimental evidence. It is a purely philosophical choice, one which most people have made on the basis of Occham's razor, but one which you are free to make on any aestetic or philosophical basis you like.

 

[zenith8]

First, Scientific American is a popular magazine, not a peer-reviewed journal (not even on the minimal level of arXiv), so take it for what it is. Second, nothing in that article contradicts my point that Lorentz's aether theory and Einstein's special relativity are completely experimentally indistinguishable, nor does anything in the article support your assertion that EPR provides experimental evidence that verifies Lorentz and falsifies Einstein.

You simply cannot make such a choice based on experimental evidence. It is a purely philosophical choice, one which most people have made on the basis of Occham's razor, but one which you are free to make on any aestetic or philosophical basis you like.

Lighten up, Dale. I never said it was a peer-reviewed journal - I just meant to imply it was an interesting, relevant article for the point under discussion. Anyway, David Albert is hardly some undergraduate nutjob - he is widely known as an expert in quantum foundations and has written highly-praised books on the subject.

Try the recent book "Einstein, Relativity, and Absolutely Simultaneity" which contains about 20 articles making the same point. Or is the case of two experts in the field asking 18 other experts in the field to write articles, reading them carefully and criticising them, and publishing them in a book not peer-reviewed enough for you?

Therefore, if you do find experimental evidence of a preferred frame then you will have falsified both Einstein (who says there is no preferred frame) and Lorentz (who says it is experimentally undetectable).

I'm sorry - your argument is logically ludicrous. Lorentz's theory states that there is a preferred frame/ether and explains why that preferred frame/ether would be undetectable in something like a Michelson-Morley experiment relying on measurements of lengths etc.. It does not state or imply that it is impossible to detect the preferred frame at all ever - especially through a completely different (and in 1905 completely unsuspected) mechanism.

Zenith

 

[Mentz114]

Hi Zenit,

interesting article. I noted

Thus, the mere existence of a nonlocality in quantum mechanics, in and of itself, does not mean that quantum mechanics cannot coexist with special relativity. So perhaps there is hope.

Yay ! We're off the hook.

The kind of nonlocality one encounters in quantum mechanics seems to call for an absolute simultaneity, which would pose a very real and ominous threat to special relativity.

( my bold )

Which is not the case surely ? Why does the transmission have to be instantaneous rather than say 100000c ? Notice they say 'seems to'.

The article is a bit woolly in places. It reminded of your posts.

 

[zenith8]

Yay ! We're off the hook.

Damn! [gnashes teeth]

Which is not the case surely ? Why does the transmission have to be instantaneous rather than say 100000c ?

Because that is what QM predicts.

But anyway if it wasn't instantaneous then you would be able to detect the preferred frame. Do an EPR experiment in which the relative time of detection of the two particles was extremely accurately determined. In principle the Bell inequality would then no longer be violated as there wouldn't be any time for the disturbance of one particle to propagate to the other before the measurement was made on it. And then the second particle wouldn't go into the usual state of correlation with the first one. Clearly this would need to be done a lot more accurately than they currently do it (and I think, like Michelson-Morley, you would have to take into account the speed of the Earth through the ether).

And if you did find such a thing that would mean both QM and STR were wrong..!

And then the 'self-appointed defenders of the orthodoxy' (20 points on the http://math.ucr.edu/home/baez/crackpot.html" !) would be really upset..

Notice they say 'seems to'.

Because of the four implausible get-outs I offered in my original post.

Zenith

 

[Mentz114]

I hope you don't include me in the 'defenders of the orthodoxy'. They wouldn't like it.

Probably none our current physical theories are right, but if I have to choose between instant signalling and SR I go with SR on the balance of the evidence.

I'm not convinced that non-locality can be used to propagate messages instantly. The only practical use seems to be ensuring messages have not been read by eavesdroppers.

Because of the four implausible get-outs I offered in my original post

That list is far from complete.

 

[Demystifier]

It seems to me that Bell's theorem and the Aspect EPR-style experiments demonstrating non-locality in quantum mechanics imply an absolute simultaneity and therefore that there must be a preferred frame. The experimentally confirmed instantaneous action at a distance cannot occur otherwise (the actual results of the experiment would be observer dependent if there were no such frame).

Relativity can be made compatible with the existence of a preferred frame if that frame is determined DYNAMICALLY, essentially by the choice of initial conditions. But the initial conditions on what? A possible answer is - the initial conditions on particle 4-positions in a relativistic-covariant version of the Bohmian hidden variable formulation of quantum mechanics.
See e.g.
http://xxx.lanl.gov/abs/quant-ph/0512065 [AIP Conf.Proc.844:272-280,2006]
http://xxx.lanl.gov/abs/0811.1905 [accepted for publication in Int. J. Quantum Inf.]

 

[Fredrik]

I'm sorry - your argument is logically ludicrous. Lorentz's theory states that there is a preferred frame/ether and explains why that preferred frame/ether would be undetectable in something like a Michelson-Morley experiment relying on measurements of lengths etc.. It does not state or imply that it is impossible to detect the preferred frame at all ever - especially through a completely different (and in 1905 completely unsuspected) mechanism.

If the theories make the same predictions about the results of experiments, then it's impossible to distinguish between them. As far as I know, they do make the same predictions. (I could be wrong though; I don't know much about the Lorentz theory). So if an experiment can show that there's a "preferred frame", it proves the Lorentz theory wrong too.

Notice they say 'seems to'.

Because of the four implausible get-outs I offered in my original post.

Those "get-outs" are mostly crazy talk anyway (see #9), but a modified version of #2 is likely the correct answer.

What you really should notice is that they didn't offer any arguments to support the idea that quantum non-locality might require a preferred frame. The article is actually rather strange. The "seems to" comment, and phrases like "hope for special relativity?" and "nonlocality could be compatible with special relativity" suggest there's a good reason to believe that it isn't. And yet they don't mention any such reasons.

 

[Dale]

I'm sorry - your argument is logically ludicrous. Lorentz's theory states that there is a preferred frame/ether and explains why that preferred frame/ether would be undetectable in something like a Michelson-Morley experiment relying on measurements of lengths etc.. It does not state or imply that it is impossible to detect the preferred frame at all ever - especially through a completely different (and in 1905 completely unsuspected) mechanism.

I think I understand the core problem in both this thread and your other thread. You simply do not understand what Lorentz's theory actually says and are supporting it purely out of ignorance. In the last thread you thought that Lorentz predicted physiological or optical "squishing", and in this thread you think that Lorentz is compatible with a detectable preferred frame. In both threads you mistakenly think that any preferred frame will do to support Lorentz, and neglect the fact that it must satisfy the Lorentz transform.

Tell me how you think your EPR experiment both satisfies the Lorentz transform and establishes a preferred frame.

 

[Mentz114]

Instantaneous paradox

If I had some of these instantaneous transceivers, I could arrange them so transmitter A sends to transmitter B, which then sends back to A. A is a bomb also and is triggered by any incoming signal. It explodes at the very same instant it transmits the signal that exploded it.

To be paradoxical this requires absolute simultaneity. Any delay in any part makes it just a stupid bomb.

This is why I distrust absolute concepts.

 

[zenith8]

If I had some of these instantaneous transceivers, I could arrange them so transmitter A sends to transmitter B, which then sends back to A. A is a bomb also and is triggered by any incoming signal. It explodes at the very same instant it transmits the signal that exploded it.

To be paradoxical this requires absolute simultaneity. Any delay in any part makes it just a stupid bomb.

This is why I distrust absolute concepts.

Why don't you just cut out B altogether and just have the big red button on A linked to its own detonator? Same result. The bomb explodes when you press the button. Why is this paradoxical?

 

[Mentz114]

Why don't you just cut out B altogether and just have the big red button on A linked to its own detonator? Same result. The bomb explodes when you press the button. Why is this paradoxical?

Two things happen at the same time and the same place - a signal is sent and destruction of the transmitter takes place. If the events are truly simultaneous we can say that the bomb exploded before the signal was sent with the same validity as the other way round.

Clearly we'll need an experiment to decide what really happens.

 

[zenith8]

Two things happen at the same time and the same place - a signal is sent and destruction of the transmitter takes place. If the events are truly simultaneous we can say that the bomb exploded before the signal was sent with the same validity as the other way round.

Clearly we'll need an experiment to decide what really happens.

No, come on. Most of your comments have been very sensible but you're really off-beam here.

In a real bomb the electrons will take some nanoseconds to traverse the relevant wires to explode the bomb.
If what you are suggesting is true then it is exactly the same paradox when you only have one single device with the red button attached to the detonator. What you're saying is that in your magic bomb it explodes instantaneously as soon as someone presses the button therefore they couldn't possible have pressed it in the first place (which is not true, anyway).

There is no additional content to this though experiment if the signal from the red button takes an instantaneous round trip to the other side of the universe and back, before passing down the wires to the detonator, even if the time from button press to explosion could be shrunk to zero.

Zenith

 

[Demystifier]

Has anybody noticed my post #84?

 

[Mentz114]

No, come on. Most of your comments have been very sensible but you're really off-beam here.

In a real bomb the electrons will take some nanoseconds to traverse the relevant wires to explode the bomb.
If what you are suggesting is true then it is exactly the same paradox when you only have one single device with the red button attached to the detonator. What you're saying is that in your magic bomb it explodes instantaneously as soon as someone presses the button therefore they couldn't possible have pressed it in the first place (which is not true, anyway).

There is no additional content to this though experiment if the signal from the red button takes an instantaneous round trip to the other side of the universe and back, before passing down the wires to the detonator, even if the time from button press to explosion could be shrunk to zero.

Zenith

I suppose the round trip is superfluous. The instant bomb is another kind of paradoxical thing ( it is paradoxical because it both does, and does not explode ).

I will look at Dr Nikolic's papers now. The second one looks interesting - here is the abstract

The kinematic time operator can be naturally defined in relativistic and nonrelativistic quantum mechanics (QM) by treating time on an equal footing with space. The spacetime-position operator acts in the Hilbert space of functions of space and time. Dynamics, however, makes eigenstates of the time operator unphysical. This poses a problem for the standard interpretation of QM and reinforces the role of alternative interpretations such as the Bohmian one. The Bohmian interpretation, despite of being nonlocal in accordance with the Bell theorem, is shown to be relativistic covariant.

 

[zenith8]

I suppose the round trip is superfluous. The instant bomb is another kind of paradoxical thing ( it is paradoxical because it both does, and does not explode ).

Look, I'm sorry - it really is not paradoxical.

You press the red button. The bomb explodes immediately. You die. End of story.

I think you're saying - in effect - that it is not possible for an effect to happen at the same instant as its cause?
Isn't that the definition of locality?

Zenith

 

[Mentz114]

Look, I'm sorry - it really is not paradoxical.

You press the red button. The bomb explodes immediately. You die. End of story.

I think you're saying - in effect - that it is not possible for an effect to happen at the same instant as its cause?
Isn't that the definition of locality?

Zenith

We're talking about two different bombs. As you've pointed out this is not relevant to the issue so let's forget the instant bomb and I'll stop trying to find logical or causal fallacies ( I'm not saying they don't exist). The definition of locality is 'an event cannot happen at the same time as its cause if they are spatially separated'. Locality - as in space.

I'm more interested in how non-local QM can be made covariant.