Can Spinors Bridge the Gap Between Quantum Mechanics and General Relativity?

[Tom McCurdy]

I was reading Brian Greene's the elegant universe when I came across the section talking about how two people Gracie and George are traveling past each other in empty space. To each other they are stationary and the other is moving, therefore to each other the other's clock is slower. Greene discusses setting the clock to 12:00 and passing each other and how in order to check clocks later even by cellualr communication the max speed is that of light so the time it would take to contact the other to ask the the time on their watch would more than compensate for the slowness of the clock. In fact i believe he said that if there was something that was instantaneous it would mean the fall of the theory. Here is my question. As far as not being able to communicate instantly there may infact be a way I thought of from my physics class. If you separate the electrons in an electron pair no matter how far the distance the pair still "sees" itself as being connect and when one is fliped the other instantly does. I believe the space program is working on this idea to create a phone that would be used on longer than Mars missions. So my question is what would happen if they were called each other using a electron pair phone?

 

[jcsd]

Reduce it the problem:

When (the component of spin along some axis of) the 'transmitter' electron is measured you will obtain randomly either a value of +0.5 or -0.5, if the value is +0.5 then the 'receiver' electron will have a value of -0.5 and vice versa. Before this time neither electron has a definite value.

How then can this used to transmit information? If the receiver measures his electron, he gets exactly the same results if the tranmitter has measured his electrons or not (even though in the first instance it means that his elctron already has a definite value and in the second instnace it doesn't), so there's no way of sending any useful information via this method.

 

[Tom McCurdy]

way to communicate

Reduce it the problem:

When (the component of spin along some axis of) the 'transmitter' electron is measured you will obtain randomly either a value of +0.5 or -0.5, if the value is +0.5 then the 'receiver' electron will have a value of -0.5 and vice versa. Before this time neither electron has a definite value.

How then can this used to transmit information? If the receiver measures his electron, he gets exactly the same results if the tranmitter has measured his electrons or not (even though in the first instance it means that his elctron already has a definite value and in the second instnace it doesn't), so there's no way of sending any useful information via this method.

It has been suggested and is actually possible right now to control the fliping of electrons (although right now it is done in huge facilities) thereby if you can create a code with some sort of 1 and 0... say something similar to binary there is way to communicate messages

 

[jcsd]

It has been suggested and is actually possible right now to control the fliping of electrons (although right now it is done in huge facilities) thereby if you can create a code with some sort of 1 and 0... say something similar to binary there is way to communicate messages

I think you may be muddled up because it goes against the fundmental postulates of quantum physics to control which eigenstate the electrons will collapse into 9though you exert a measure of control on the proabilty, but that in no way makes the entanglend electron phone possible)

 

[Tom McCurdy]

I think you may be muddled up because it goes against the fundmental postulates of quantum physics to control which eigenstate the electrons will collapse into 9though you exert a measure of control on the proabilty, but that in no way makes the entanglend electron phone possible)

hmm, I was told in class that they are already able to control the the electron pair and flip it when they want to and watch it to see where it is at. The problem like I said earlier was the size of the device, my problem like what you infered as this presents problems for SR like when when two people moving call each other on one of these things to check watches it destroys sr properties.

 

[jcsd]

I really can't see how you can control the collapse of the wavefunction so that you can 'decide' which eigenstate you get. If this were the case it would falsify quantum physics. You can exert control over the expected value, etc, but you just can't be assured of getting the same value everytime.

 

[Tom McCurdy]

-I more see a problem in SR, anyway I am looking for a site where i can show you some of the research

 

[selfAdjoint]

I really can't see how you can control the collapse of the wavefunction so that you can 'decide' which eigenstate you get. If this were the case it would falsify quantum physics. You can exert control over the expected value, etc, but you just can't be assured of getting the same value everytime.

You can set up the experimental conditions so the AVAILABLE set of eigenfunctions is down to one or two, and then set up interferences that eliminate one of the possibilities. Look up "quantum eraser" or read the book Schroedinger's Kittens by John Gribbin. This does not violate the canons of QM but rather cleverly manipulates them.

 

[Tom McCurdy]

So if it IS possible to set up what would happen if the two talked wouldn't this voilate the laws of relativity indicated that there would be one true answer, and that they both couldn't see the others clock running slower

 

[jcsd]

So if it IS possible to set up what would happen if the two talked wouldn't this voilate the laws of relativity indicated that there would be one true answer, and that they both couldn't see the others clock running slower

No it's still impossible to comunictae solely using entanglemnt, the point is if you have a wavefunction that will give a ceratin set of eigenfunctions after collaps you cannot specifically choose which it will collapse into, though as self-adjoint points out you can eliminate some of the eigenfunctions avidable to obtain the desired eigenvalue.

The quantum eraser involves a measuremnt on one pair of entangled photon which allows you to detrimine the stae of the phton without measuring it. If we apply that to our experimnet we find that in order for this to be useful the two people on the electron telephones have to speak to each other via anther method to share the results of their experiments.

 

[Tom McCurdy]

I am not talking bout collapsing anyting, merely being able to "flip" an electron, keep in mind I have only taken one year of physics, however when my physics teacher comes back from his trip I will ask him to clarify what he was talking about. He was telling us that this is a reality and they already have the equipment to do it, they just need to make is smaller and create the language.

 

[Tom McCurdy]

add on

Additionaly wouldn't it be true if anything was in the same quantumstate it would flip instantly if its brother particle was fliped.

 

[jcsd]

Yep you can 'flip' the electron but then the values are either (0.5,0.5) or (-0.5,-0.5) as opposed to (0.5,-0.5), (-0.5,0.5)

 

[Tom McCurdy]

yes that's the whole point I believe you are able to see if its .5 .5 or -.5 or -.5 and becasue of this u are able to make a code have .5 .5 be one or -.5 -.5 be zero then you could have binary system

 

[Tom McCurdy]

I think through more thought that this is whole point we are looking for toe, my thought experiment represents the conflict between QM and GR without any math :)

 

[jcsd]

No as it is impossible to use this method to communicate, it doesn't represnt a paradox with rleativity (and general relativity has been completely ignored here via the tacit assumptions)

 

[Tom McCurdy]

How is it impossible... if you can control the state of the electrons in the same quantum state... which you can... and you can check to see if they are both possitive or both negitive ... which you can... then you can make a device to communicate. Hell you could use a morse code system if you wanted to. It will be a long time before you could make any sort of voice system off of this if it would be even possible... many theorize it can be done... but for now the binary or morse code system is in the not to distant future.

So if we have the phone...
And we have two people moving past each other
They both see the others clock running slower because of relativity
They are allowed to compre clocks because of the phone which works because of as self adjoint pointed out clever manipulation of Quantum Mechanics...

Therefore they both can't be right
IE
GR vs QM
IE
Conflict 3
IE
why we need TOE
IE
I like saying IE

 

[Tom McCurdy]

GR is involved because GR states that no inflence can travel faster than c, which in this case it can.

 

[jcsd]

How is it impossible... if you can control the state of the electrons in the same quantum state... which you can... and you can check to see if they are both possitive or both negitive ... which you can... then you can make a device to communicate. Hell you could use a morse code system if you wanted to. It will be a long time before you could make any sort of voice system off of this if it would be even possible... many theorize it can be done... but for now the binary or morse code system is in the not to distant future.

So if we have the phone...
And we have two people moving past each other
They both see the others clock running slower because of relativity
They are allowed to compre clocks because of the phone which works because of as self adjoint pointed out clever manipulation of Quantum Mechanics...

Therefore they both can't be right
IE
GR vs QM
IE
Conflict 3
IE
why we need TOE
IE
I like saying IE

You cannot choose into which state the elctrons will collapse though which is the fundamental problem, the quantum earser allows you to choose, whether or not you have a superpostion of one state or two states (for example), but it doesn't allow you to choose the one state.

Thios doesn't demonstrate the conflict with general relativity as we only need to consider special relativity here and there is no irresovable conflict between quanum mechanics and special relativity EVEN though special relativity tells us that information can't travel faster than c.

 

[Tom McCurdy]

GR states no influence can travel faster than c which would be what the QM phone would do. I am still trying to find this damn article... I will though :)

 

[jcsd]

GR states no influence can travel faster than c which would be what the QM phone would do. I am still trying to find this damn article... I will though :)

I don't htink you're ubnderstanding what I'm saying:

1) the elctron phone does not work.

2)There's nothing in the thought experiment that invokes general relativty, we need only consider special relativity (which also says that information cannot travel above c).

 

[Tom McCurdy]

GR revolustionized the way we view the universe... that it responds with warps and curves with response to matter. It stemed from the conflict between Newton's universal law of gravitation vs the ideas spread in SR. WAs fixed by einstein... stating nothing can travel faster than light- no influence.

 

[Tom McCurdy]

Read this http://www.quantumninja.com/toe/modules.php?name=News&file=article&sid=1&mode=&order=0&thold=0 that I wrote and (join the site while you are there :) )

 

[Tom McCurdy]

Do you agree that if something in pairs were in the same quantum state and one was fliped then the other one would do so instantly?

 

[jcsd]

GR revolustionized the way we view the universe... that it responds with warps and curves with response to matter. It stemed from the conflict between Newton's universal law of gravitation vs the ideas spread in SR. WAs fixed by einstein... stating nothing can travel faster than light- no influence.

The point I'm making is we're not mentioning gravity at all, so we only need to talk about special relativity which is a special case of general relatvity.

 

[jcsd]

Do you agree that if something in pairs were in the same quantum state and one was fliped then the other one would do so instantly?

What exactl;y do you mean by flipped? if you revresed the polarization of one of elctrons then the other electron's polarizartion remains the same. If you mean perform a measuremnt to determine the value of say for example the spin compoment in the z-axis, then that measuremnt would also instantly fix the value of the other's spin component in the z-axis.

 

[Tom McCurdy]

Self Adjoint Helped explain along with your posts, however I will still try to find what my physics teacher was talking about
Here was Self Adjoint wrote this
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Th key words on this effect are Entanglement, EPR (stands for Einstein, Podolski, and Rosen, who first published a paper foreseeing this effect), and Bell inequality (for John Bell, a CERN physicist of the 1960's who worked out his inequalities as a method for testing the effect). Also Aspect (don't know his first name, did the first real experiment that showed the effect). Here's how it goes.

You somehow or other produce two particles that are entangled. In quantum mechanics they form a single state, and whenever you observe one particle as having some condition (like spin or polarization), the other particle will be known to have the opposite condition). With just two particles, if you do that observation you destroy the entangled state, and so you can't send messages that way. Any quantum measurement or observation destroys the existing state of what is being observed. This is what used to be called "The collapse of the wave function". After the observation the system picks up in a new state.

Entanglement is a great way to move information around, but it can't do it faster than light. Therefore using entanglement doesn't in any way conflict with relativity (as long as you use quantum mechanics to analyze the experiments. If you use, say, Bohm's replacement for quantum mechanics, then that DOES violate relativity).

I've left a lot out of this message, in order to get the key facts to you as quickly as possible. Bottom line: no professional physicist believes entanglement can send messages FTL, but all kinds of kooks and cranks, who happily admit they can't do the math, are in love with the idea.

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Do you or anyone else then give me an example of a conflict between GR and QM that wouldn't involve math other than saying something like Blackholes-- the math doesn't work out since it involves big stuff getting crushed into a singularity.

 

[jcsd]

I can't give you an example of the conflict between GR and quantum mechanics, because it's way beyond me, you might want to look up the "renormalization problem" tho'.

 

[Tom McCurdy]

Thanks for you help... Self gave me an example... Its a bit advance but i think it will work... what do you think about it JCSD
----------- by self adjoint
One thing is, the most interesting particles in quantum mechanics are defined by spinors. Spinors are a lot like vectors - they have components - but they act different from vectors when you change coordinates.

Now in general relativity it is very important that you be able to change coordinates freely and that the equations representing your physics will still be true in the new coordinate system. This is because different coordinates determine different frames of reference, different viewpoints. Things which behave this way are called tensors, and Einstein's physics is built out of tensors.

Now here's the bummer. Spinors aren't tensors and they won't behave like tensors when you change coordinates. A spinor equation will be changed completely. So you have this spinor representing an electron over here, and you look at it from a different frame of reference and it's a different particle, maybe a quark. No good. So that's one way quantum mechanics doesn't work with general relativity.

Remember the difference between special relativity and general relativity; quantum mechanics has no problem with special relativity. It's built into Dirac's theory of the electron, and into all the theories that came after that including the standard model and string theory. It's only general relativity that they can't fit with quantum mechanics.
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Plus I get to say Spinors in a a lecture :)