Relativity & Quantum Theory: Is Locality Violated?

[ttn]

and the MWI has been experimentally verified-

If it weren't such a deep indictment of the culture, I'd roll on the floor and laugh at this statement (which appears to come from a *philosopher*, i.e., a person whose profession is supposed to be thinking clearly about this kind of thing). No wonder the foundations of physics are so screwed up. I mean, seriously, in order to even claim consistency with experiment, MWI has to ask us to believe that we're deluded about everything we've ever thought or believed on the basis of perception (including, notably, how all the experiments have come out). So it's been "experimentally verified" to about the same extent that it's been experimentally verified that eating a 100 pound asbestos-and-uranium sandwich will cure you of cancer. Sure, all the people who ate such sandwiches have *appeared* to die of cancer shortly thereafter, but I have this theory that says those appearances are wrong, and that *really* those people are all living happy lives and *really* it's all the people who *didn't* eat those sandwiches that are dead (again, appearances to the contrary notwithstanding). You see, it's part of my theory that our eyes deceive us. And, hey look, my theory is consistent with what we appear to see -- it explains the delusionalness of our so-called perception and tells us what is really true -- so therefore it's confirmed by the data.

Again, that somebody could seriously believe all of this would normally be quite funny. I love laughing at such stupidity. But it's really not funny when such stupidity is so evidently widespread among supposedly serious people. Then it's sad and scary.

 

[Farsight]

Sucks teeth: I just don't buy the Many Worlds Interpretation.

http://en.wikipedia.org/wiki/Many-worlds_interpretation

Apart from the concept of multiple realities, the conceptual showstopper for me is that these many worlds must be the world. It's like when I hear somebody on TV talking about "Universes". The word Universe is of Greek origin. Think "Uni" as in unicycle, and "versa" as in vice versa. It means "turned into one". It means everything, and you just can't have more than one everything.

I don't have any answers, but I wonder if the real problem is in the word particle.

 

[setAI]

LOL! as I said- it is rather disturbing that in 2006 we are still seeing this odd distate for the reality of the MWI- 10 or even 5 years ago you could still have a legitimate argument- but the advent of quantum computers ended this debate-[ quantum computers simultaneously show that the Copenhagen interpretation is false and demonstrate the physical reality of the MWI http://xxx.lanl.gov/abs/quant-ph/0104033 ]- but I guess it takes some time for the ripples to shake everyone from their obsolete paradigms- I am sure there were many scientists who continued to argue for a classical ether for a few years after the Michaelson Morley experiment

but- at the end of the day one cannot argue with OBSERVED reality- the Earth is round- evolution happens- and we live in a multiverse- you're just going to have to deal with it-

there are no philisophical or logical problems with a multiverse- only personal aesthetic ones- as D Deutsch has pointed out again and again- slowly the rest of the physics community has agreed- but there are still some out there who have a hard time with it- [I don't really understand why- a multiverse is an ontological necessity unless you posite some epicycle-like mechanism that magically prevents other universes from existing just as this one- a demon that exists just to nullify the other decoherred histories of the Schroedinger equation]

"Our best theories are not only truer than common sense, they make more sense than common sense... "

"there are indeed other, equally real, versions of you in other universes, who chose differently and are now enduring the consequences. Why do I believe this? Mainly because I believe quantum mechanics... Furthermore, the universes affect each other. Though the effects are minute, they are detectable in carefully designed experiments... When a quantum computer solves a problem by dividing it into more sub-problems than there are atoms in the universe, and then solving each sub-problem, it will PROVE to us that those sub-problems were solved somewhere - but not in our universe, for there isn't enough room here. What more do you need to persuade you that other universes exist? "

~David Deutsch

 

[Hurkyl]

Apart from the concept of multiple realities

there are no philisophical or logical problems with a multiverse

AFAIK, that is not an accurate depiction of MWI.

The universe has a state. That state contains many details that are irrelevant to you. So, one applies a mathematical operation (partial trace) to the state of the universe to obtain a state containing only the information relevant to you. That is your "world". It is not some sort of alternate reality.

This isn't even a quantum idea -- we do it all the time in the classical regime. For example, when we study ballistics here on Earth, we discard the information about what's happening over in Andromeda galaxy.


But, I presume both of you are not talking about the "worlds", but the hypothesis that the universe really is in some sort of quantum state. But that also doesn't look like multiple realities, or a multiverse.

The notion of a "superposition of states" is simply an artifact of one mathematical way of representing states... and even in the linear representation, there is one choice of freedoms in which the state is not in a superposition.

E.G. in one perspective, the photon is in a superposition of spin-up and spin-down about the Z axis... but you could say the superposition is just an artifact of your perspective: it's actually in a certain spin-up state about the Y axis. (depending on the actual numbers, of course, a different axis would be the "right" one)

I mean, seriously, in order to even claim consistency with experiment, MWI has to ask us to believe that we're deluded about everything we've ever thought or believed on the basis of perception (including, notably, how all the experiments have come out).

So does Newtonian mechanics. When I see things in motion, they tend to come to rest. But Newtonian mechanics says I'm deluded and things in motion tend to stay in motion, and that there's some mysterious external force that is causing things to come to rest!

And, of course, Special Relativity. It would have me believe that when someone is walking across my room, I should think they appear thinner! Of course, it conveniently says that the difference should be to small to measure.

Oh, and General Relativity. It would have me believe there is no such force as gravity! How daft can you get?



The situation is fairly analogous to Special Relativity.

Maxwellian electrodynamics said some fairly wacky things about the universe.

Some people invented all sorts of strange physical mechanisms so that they could incorporate the emprical success of Maxwell's equations into their beloved notion of the universe.

Some other people adopted the view that Maxwell was right, adjusted their notion of the universe appropriately, and were able to explain why the universe appears the way we thought it was.

We see now which camp has won.


That's what's going on here: the quantum theory suggests quantum weirdness. Some people like to believe in some strange physical mechanism that allows them to incorporate the successes of quantum mechanics into their beloved classical notion of the universe. Others adjust their notion of the universe appropriately. MWI is one way to explain why the universe appears the way we thought it was.

But it's really not funny when such stupidity is so evidently widespread among supposedly serious people.

There's a big difference: your "abestos-and-uranium-sandwich theory" is not based upon empirically successful physics. MWI is.

The "stupidity" here is the irrational clinging to some ad-hoc physical mechanism that make one's beloved notion of the universe literally true, and refusing to even entertain the notion that such mechanisms aren't necessary.

 

[Farsight]

Thanks for the link, setAI, I've printed out David Deutsche's paper and will study it carefully.

hurkyl, what you're saying sounds good to me. I think.

I'll get back here when I've read that paper tonight.

 

[ttn]

So does Newtonian mechanics. When I see things in motion, they tend to come to rest. But Newtonian mechanics says I'm deluded and things in motion tend to stay in motion, and that there's some mysterious external force that is causing things to come to rest!

Huh? This makes it sound like you are quite clueless about Newtonian physics (which I doubt is the case). Do you really think Newton's first law says "all moving things will keep on moving no matter what"?

Anyway, there is a very clear sense in which MWI insists that we are deluded about basic apparent perceptual facts. This is in contrast to every other scientific theory that is or has been widely accepted. If this sense is not clear to you, maybe you should ask about it (or, say, read the clarifying sections of David Albert's "QM and Experience") rather than parodying it.

And, of course, Special Relativity. It would have me believe that when someone is walking across my room, I should think they appear thinner! Of course, it conveniently says that the difference should be to small to measure.

In other words, what you actually see matches (within the relevant uncertainties) with what the theory says is actually happening. This is in stark contrast to MWI. According to MWI, the real state of the world does *not* have a person walking across your room, so your perception to the contrary is a *delusion*.

Maxwellian electrodynamics said some fairly wacky things about the universe.

Please. When I say that MWI requires us to accept that our perceptual experience is delusional, I'm not just saying "MWI is fairly wacky". I use language carefully and precisely. MWI is fairly wacky, yes, but that is not the point at issue here.

That's what's going on here: the quantum theory suggests quantum weirdness. Some people like to believe in some strange physical mechanism that allows them to incorporate the successes of quantum mechanics into their beloved classical notion of the universe. Others adjust their notion of the universe appropriately. MWI is one way to explain why the universe appears the way we thought it was.

The whole point I am making is that your last sentence, taken literally, is quite false. "The way we thought it was" surely includes things like the needles on experimental apparati in Germany in the 1920's swinging in particular directions, yes? Well, according to MWI, that (and a gazillion other things like it, including, as I've said, pretty much all of our perceptual experience of the world) never actually happened. In other words, it is a delusion. So is MWI "one way to explain" all the perceptual/empirical evidence that led to quantum mechanics? Literally speaking, no. It doesn't explain that evidence; it explains it away (so to speak). According to it, that evidence was all wrong.

You have to admit, that's a very uncomfortable (because circular) position for a theory to be in.

There's a big difference: your "abestos-and-uranium-sandwich theory" is not based upon empirically successful physics. MWI is.

No, it isn't. At least, not in anything like the normal scientific sense.

The "stupidity" here is the irrational clinging to some ad-hoc physical mechanism that make one's beloved notion of the universe literally true, and refusing to even entertain the notion that such mechanisms aren't necessary.

So, it's stupid to believe that when I see a table in front of me, there's really, in external physical reality, a hunk of table-shaped stuff out there? Or that when I see the needle go right, that's because, really, there is a needle and it moved to the right?

I would ask you to seriously consider what is left of science (including in particular the alleged empirical evidence for MWI) if you take this seriously.

 

[Hurkyl]

No, it isn't. At least, not in anything like the normal scientific sense.

You take an empirically successful principle (unitary evolution), and you push it to its logical conclusion -- in the theoretical domain, how can you get more scientific than that?

To the best of my knowledge, MWI is a theory about unitary evolution. That's it. Unlike your "curative asbestos-and-uranium sandwiches" (hey, weren't you objecting to parodies? ), MWI doesn't postulate anything new: it simply studies what follows from unitary evolution. And at any point, you could reintroduce wavefunction collapse and be doing orthodox quantum mechanics. (But, you would no longer be doing MWI)


I had previously been thinking that you meant "deluded" simply to refer to the fact we think we see a classical state, when the universe is in a quantum state. But I have absolutely no idea where you get things like:

: According to MWI, the real state of the world does *not* have a person walking across your room
: Well, according to MWI, that ... never actually happened.
: According to it, that evidence was all wrong.

 

[selfAdjoint]

You take an empirically successful principle (unitary evolution), and you push it to its logical conclusion

People disagree that it's logical. Unitarity is surely a useful property, but making it the be-all of everything, at the cost of either "parallel worlds" or the possibility that people I see on the street are in a different state as far as their furshlugginer consciousness is concerned, is not best described as "logical" IMHO. And it still doesn't answer the question, how can QM operate, as evidently it does, completely hidden from human consciousness, say inside the Sun?

 

[Farsight]

setAI, hurkyl: I read the David Deutsche paper and have to say I didn't understand it. So I read it again, and again, and I still couldn't follow its thrust or see anything that "proved" the MWI. If either of you could post a link to an alternative paper or article I'd be grateful.

 

[selfAdjoint]

... see anything that "proved" the MWI

There is nothing that proves MWI, it's something that those who believe in it try to persuade you of. In other words it's like philosophy or religion: "Go on and faith will come to you."

 

[Farsight]

Er, no thanks.

setAI: can you post another link that demonstrates why MWI sounds likely or plausible?

 

[setAI]

http://xxx.lanl.gov/pdf/quant-ph/0303050

http://www.citebase.org/cgi-bin/citations?archiveID=oai:arXiv.org:gr-qc/9404013

 

[Farsight]

Thanks, setAI. Look, I don't mean to be rude, but I'm afraid they come over as "magicked out of the hat" leaping logic lubricated by bigword babble and psuedo-mathematics. If I missed a trick somewhere, apologies. But I am mathematically literate and I am smart. And I am in no way convinced of MWI by these links.

I remain deeply interested QM matters. Such as the "Quantum Eraser":

http://www.bottomlayer.com/bottom/kim-scully/kim-scully-web.htm

http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

"In terms of the conventional way of viewing the physical universe, this result seems disturbing. One possible explanation is that the causality of the second observation travels back through time to affect the outcome of the first observation. In other words, this is time travel. Oddly enough, quantum mechanics does not seem to have much of a problem with time travel. Similarly bizarre results have been shown in other experiments where we have spooky action at a distance..."

Unless somebody can tell me something better about MWI, I fancy the time travel.

 

[Hurkyl]

The only thing I'm really convinced of is that it is not necessary to assume that wavefunction collapse is a physical process.

Entangled states, quantum erasers, counterfactual computation... IMO none of that seems weird at all, unless you're working in a mindset that collapse happens as a physical process.

I first realized this during a (brief) introduction to quantum computing in one of my math courses: we were introduced to the CNOT gate whose action on a pair of qubits in basis states is given by:

|x> ------*------ |x>
          |
       /--+--\
|y> ---|C-NOT|--- |x+y>
       \-----/

In particular, if our second qubit is in the |0> state, then this is:

|x> ------*------ |x>
          |
       /--+--\
|0> ---|C-NOT|--- |x>
       \-----/

and the whole thing acts as if we had actually measured the first qubit and stored the result in the second qubit... except that a collapse didn't happen. e.g. on a superposition of |0> and |1>, we'd get have:

(a|0> + b|1>) |0>

on the left hand side, and:

a |0>|0> + b |1>|1>

on the right hand side.

If you try to imagine behaviors that measurements have... such as consistency, you'll find that these CNOT gates have that property. e.g.

|x> ------*---------*------ |x>
          |         |
       /--+--\      |
|0> ---|C-NOT|------------- |x>
       \-----/      |
                 /--+--\
|0> -------------|C-NOT|--- |x>
                 \-----/

if we make two different "measurements" of the firstqubit, the results are the same. Of course, I'm cheating by simply saying they're the same: I really should add another gate to this circuit to "measure" if they are the same... and if we did, we would find that the result of that measurement is always "yes", even if the original input is in a superposition of |0> and |1>.

 

[Farsight]

There's something very weird about the interference pattern appears at both detectors, hurkyl.

http://www.joot.com/dave/writings/articles/entanglement/spookiness.shtml

Ah, I am but a blind man searching a thunderstorm for the lightning particle.

 

[Farsight]

Hurkyl:

I made a post on the "Electron Energy" thread and it's disappeared. It was nothing contentious, just a link to something I found when looking up infinite energy. This sort of thing has happened a few times. Is there some kind of priesthood god damn thought-police on this forum expunging any concepts that challenge dogma? And is this Physics, or the Catholic Church circa 1450?

 

[selfAdjoint]

Hurkyl:

I made a post on the "Electron Energy" thread and it's disappeared. It was nothing contentious, just a link to something I found when looking up infinite energy. This sort of thing has happened a few times. Is there some kind of priesthood god damn thought-police on this forum expunging any concepts that challenge dogma? And is this Physics, or the Catholic Church circa 1450?

If you read the guidelines, and every new poster has to sign that he or she read them, then you wouldn't have to ask. If you have a theory that challenges current science then it belongs on our independent research forum, and there are strict guidelines for appearing there, mainly to make sure the theories that are present there are serious and not just random garbage.

And linking to an obvious crank site (obvious to us even if not to you) is a no-no, and if you keep doing it you will be warned, and if you still don't stop, you'll be banned. Them's the rules at PF, and if you don't like them take your creative imagination elsewhere.

 

[Farsight]

All points noted, selfAdjoint. Sorry to interrupt the thread everybody.

 

[UglyDuckling]

There is only one argument showing this, and it is the same argument showing that something *inside* the future light cone of an event can't causally affect the event. The argument is: there is no such thing as backwards-in-time causation.

Sorry I haven't replied earlier I don't get much chance to spend time on the forum.

The idea that there is backward in time causation seems to have crept into the interpretation of the proposed Bell Local Theory on its own accord. The theory itself does not contain this element. Therefore it should not be used as an argument for refuting the idea that electromagnetism is mediated by zero proper interval paths.

If we take two spatially separated quantum systems and place an observer in the vicinity of each then each observer will experience time progressing “normally” from the past to the future. For any given experimental set up and initial conditions the temporal evolution (relative to the subjective time of each observer) of the states quantum systems will be completely deterministic. The resulting state functions will provide the probabilities of measurable outcomes.

If we now consider an interaction between spatially separated systems! Let the donor emit energy of excitation at an event E1 and the acceptor receive the energy at an event E2. We know if we calculate the proper interval of separation between these two events then this has zero magnitude. In space-time these events are contiguous (Touching) and according to our proposed Bell local theory can interact directly with each other without the need of a carrier particle., Thus in space-time events E1 and E2 can be regarded as a single event but appear separated because they are viewed by observers placed at different positions and time in the universe.

The ability for the two systems to interact depended on their states immediately before interaction (relative to the subjective times of the observers). These states were dependent on the local temporal evolution of the quantum systems. There was no backwards in time causal influence necessary to trigger the interaction. There is just a single event involving the direct transfer of energy between spatially separated but properly local systems and no backward in time causation.

"Lorentz super-positioning" is a crazy phrase you seem to have made up. I have no idea what it means, and I assume others don't either. Indeed, based on what you seem to think this phrase means, I question whether you know what (normal, quantum-mechanical) super-positioning means -- i.e., whether you know any quantum physics in the first place.

You are correct I did make up the expression “Lorentz super-positioning", originally I called this idea “proper interval locality”, however I thought the word super-positioning might appeal more to specialist in quantum mechanics. I’m willing to accept it’s a “crazy phrase” and can cause confusion with the super-positioning of quantum states. Thanks for the advice.

However I’ll try and give a definition of the concept using the origin name..

Proper Interval Locality occurs when the proper interval of separation between events on the world-lines of quantum systems has zero magnitude. This occurs when, relative to a given inertial reference frame, the square of the temporal component of the proper interval is equal to minus the square of the spatial component of the spatial component of the proper interval. Under conditions of proper interval locality it is proposed that quantum systems can interact directly without requiring an intermediating particle/wave. Using this principle a method of electrodynamics can be developed which is free from the contradictions recognised in current theory.

 

[UglyDuckling]

You are mixing up two very different thing:

1) Being on the light cone (s=0) \sqrt{c^2t^2-x^2-y^2-z^2}

2) Separation in space time = \sqrt{c^2t^2+x^2+y^2+z^2}

Hi Hans

Your second expression is Euclidian and is not applicable to a universe characterised by the constancy of the speed of light relative to all inertial frames of reference. The interval between a pair of events in space-time must be calculated (for flat space-time) using the Minkowski Metric.

Following your reasoning ANY two points in the universe would have a
space-time separation of zero! Each pair of space-time points A and B
has many points C which are on the light cone of both A and B, that
is: AC = 0 and BC = 0 and thus AB = 0+0 = 0.

Your reasoning is correct any two events in space-time can be joined by zero interval paths. I suspect your instincts are telling you this is absurd every thing must happen at once! However it can be the basis of a Bell local theory and leads directly to the development of the wave-function, interference and the violation of Bell’s inequality for light correlation experiments.

The idea of universal linkage between all events takes a little getting use to but can eventually lead to a simple elegant and beautiful theory of electromagnetism? I believe it to be worth investing a little intellectual capital to get your mind round it.

Cheers

 

[Farsight]

UglyDuckling: this sounds interesting. Are you basically saying: a photon travels at the "speed of light" so no time passes for a photon. Therefore it "instantly" connects A and C such that trying to locate it somewhere between A and C means you locate it at B, and it therefore connected A and B? So trying to locate it is like trying to locate a rod somewhere along its length? Is a rod the right analagy? Or should I try to think about a property with no length? Like, is determining the position of a photon as much use as trying to measure the length of a gallon?

Or, and utmost apologies, are we straying into "crank" territory here?

Anybody?

 

[Doc Al]

Or, and utmost apologies, are we straying into "crank" territory here?

Most certainly. If UglyDuckling wishes to discuss his personal "Proper Interval Locality" theory, he should submit it to the Independent Research Forum, subject to the applicable guidelines, found https://www.physicsforums.com/showthread.php?t=82301.

 

[UglyDuckling]

UglyDuckling: this sounds interesting. Are you basically saying: a photon travels at the "speed of light" so no time passes for a photon. Therefore it "instantly" connects A and C such that trying to locate it somewhere between A and C means you locate it at B, and it therefore connected A and B? So trying to locate it is like trying to locate a rod somewhere along its length? Is a rod the right analagy? Or should I try to think about a property with no length? Like, is determining the position of a photon as much use as trying to measure the length of a gallon?

Hi Farsight

Perhaps not exactly?

What the Bell Local theory is saying, is there is no requirement for a photon at all! The geometry of space-time, demanded by the special theory of relativity, creates zero interval paths that link directly spatially separated quantum systems. This allows energy/momentum to instantly (relative to the two participating systems) and directly pass from one system to another without the need of a carrier particle.

In the case you quote where you wish to detect the “photon” in flight at some point B between points A and C; where the donor system is at A and the acceptor System at C.
Here you are altering the experimental setup. By placing a detector system at position B the donor system becomes linked by zero interval paths to the detector system at B. When an interaction occurs the donor’s energy of excitation, relative to the proper interval of time separating the two systems, is instantly passed between the systems.(A to B rather than A to C)
Nothing actually has to travel between A and C or A and B.

The basic problem we have in understanding what is going with electromagnetic interactions boils down to the fact that the geometry of the physical world particularly the geometrical relationship between space and time cannot be graphically represented. For instance let us fix a pair of events which are spatially and temporally distant from each other on a rectilinear space-time diagram. The appearance of the interval of separation represented on the diagram will be greater than the true proper interval of separation. This is an error introduced because of the way we measure and represent the locations of events in space time.

The error in the graphical representation is

((deltaX)^2 +(deltaY)^2+(deltaZ)^2+(CdeltaT)^2)^1/2 -((deltaX)^2 +(deltaY)^2+(deltaZ)^2-(CdeltaT)^2)^1/2

When
((deltaX)^2 +(deltaY)^2+(deltaZ)^2= (CdeltaT)^2)

The representational error becomes equal to the perceived gulf between the events and the true interval of separation has zero magnitude.

This defines a condition that allows objects which are distant from each other (relative to measurements in space and time) to touch each other in space-time.

Since the perceived gulf between pairs of interacting quantum systems results from errors arising from the way we measure and represent events in space and time, it is a nonsense to have a carrier particle traversing a non existent gap.

All the characteristics attributed to the photon therefore come from the donor and acceptor systems and their relationship with the geometry of space-time.

The advantage of having photonless electrodynamics is that the contradictions between special relativity and quantum mechanics disappear whilst QED can be reinterpreted without any loss of accuracy.

Or, and utmost apologies, are we straying into "crank" territory here?

Anybody?

Someone should prove me wrong if they want to call the idea crank, bogus, crackpot, jagtump etc. Although half the fun is keeping a tag of all the names people can invent.

Cheers

 

[UglyDuckling]

Most certainly. If UglyDuckling wishes to discuss his personal "Proper Interval Locality" theory, he should submit it to the Independent Research Forum, subject to the applicable guidelines, found https://www.physicsforums.com/showthread.php?t=82301.

OK Point Taken

Unless asked directly for a reply I'll keep off the subject of proper interval locality.

I'm away until the end of June so I will submit a compliant post probably sometime in July.

Cheers

 

[Ernies]

pat said:Classically, we are used to equate "correlation between events" and "causality". In quantum mechanics, this link is broken. There may be correlation without a cause/effect relationship.[end of quote].

Is the assertion that the link is always broken? If it is, what is the sense in saying that a measurement 'causes' the collapse of the wave function, and allows us to deduce some result, though other properties are made uncertain? If not always then under what conditions? To assert 'under space-like separations' seems to me to beg the question.

 

[nekkert llup]

What is it in the nature of space-time that’s enables spatially remote particles to become entangled and how one part of the entangled pair knows to 'collapse' when the other part is measured?

UD

We are missing the point by considering SR instead of GR. In the settings of EPR-like experiments, we have two setups and measurement events that are outside each other's light cone. Proclaiming that we know the angle between the SG-magnets during these events without providing an operational definition of this angle is not free. You pay a price, which is entanglement.
In the context of SR the angle between the SG magnets is precisely defined, because we can unambiguously parallel-transport a vector over any distance, but in GR we cannot. Furthermore, in GR the angle, assessed for measurement pair m, has to be reassessed for pair m+1.
If you claim that you know the metric well enough to define the angle once and for all, you are stepping outside the context where you can discuss non-locality and entanglement.