Relativity & Quantum Theory: Is Locality Violated?

[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.