Does a controversy still exist ?

[ZapperZ]

I agree with what you have stated . But this again leaves the question of how electrical energy is actually conveyed through a metal. QM regards electrons as the charge carriers , that is to say it is electrons that actually convey electrical energy ; loosely bound valence and free electrons are drawn to the positively charged ions. Unfortunately , this theory does not actually work. Take the circumstance where electrical energy flows over an open circuit without any electrons being observed. One could say , oh well ! that’s a simple one to deal with , Maxwell’s equations say it all. But the point is that Maxwell’s equations do not say it all , if they did we would once again be left with something like the Ultra violet catastrophe. If this question is raised , the answer that is usually given is that yes electrical energy is conveyed through electrons but that the energy passes from electron to electron via virtual photons . This is very confusing , is it admissible ? I was under the impression that virtual particles had to conform to Heisenberg’s Uncertainty principle , which in turn has to conform to the Conservation Laws , which means in effect that the interactions of virtual particles can not be real , except possibly in the sense of altering the direction of a real particle , they ( virtual particles ) cannot under any circumstances impart any extra momentum or energy to the real particle they are interacting with. At least this is my understanding. Thus although the concept of virtual particles might be acceptable from the QFT point of view viz-a-viz low frequency EM radiation , it cannot be applied to the conveying of electrical energy. My question is this : every interaction between electrons and other particles is mediated by real photons. This has been made especially clear in recent years , with the creation and observation , of low energy photons ( 1.4eV , 800 Nm. ) . Photons of this energy and slightly lower can only be absorbed by loosely bound valence electrons , which would make them the ideal candidate for the conveying of electrical energy. Note , that this would also escalate the wave OR particle question of light to a whole new level. It just doesn’t seem right that only in the phenomenon of electricity , exclusively , do we see electrons directly delivering energy. Isn’t it time that this was changed.

How do you make the LEAP from "optical conductivity" which was what I was trying to describe, straight into "electrical conductivity of open circuit"? Doesn't an abrupt change of topic like that causes nosebleeds?

Charge transport in metals, semiconductors, etc. is a WELL-STUDIED area of solid state physics. Open any solid state physics text if you do not believe me. One can take in everything from the semi-classical Drude model, all the way to the Landau's Fermi Liquid theory, and going into the more exotic Luttinger Liquid theory. Can you tell me where exactly in these descriptions that you see the need for a change?

Zz.

 

[Sherlock]

Sherlock while I appreciate that you have taken a lot of trouble to answer my questions and doubts and have furthermore done a good job of it , I also get the feeling that many of the pertinent points I had raised have been glossed over in your replies or simply ignored. I hope you don’t mind my making this criticism and will try to justify my statements during the course of this reply.

Criticism offered in the spirit of learning is a good thing. If I've glossed over or missed an important point, then I'm glad to have it brought to my attention.

Take first your statement that FTL is at the most a marginal issue viz-a-viz quantum mechanics.:
In actual fact FTL turns out to be very much a central issue as far as QM is concerned. Take for example the phenomenon of Quantum Tunneling which is inevitably raised whenever QM is discussed. FTL is implicit in the QM explanation of quantum tunneling. I clearly remember a reference to a group of scientists who had claimed to have transmitted a Mozart composition using FTL at 4.7 c ! If I remember rightly the subject was discussed in Physics Forums and eventually these claims were proved wrong. (I am unable to find the exact post) . Nevertheless , the fact remains that FTL is central to Quantum tunneling.

How is it central? Nothing that I've read about quantum tunneling says anything about FTL.

Again , take your insistence that EPR has nothing whatsoever to do with QM .
Yet many people feel that the EPR is a decisive issue as to whether Quantum Mechanics , at least as regards the superposition of states , is viable or not. Which is precisely the point I had repeatedly made in this thread. Also your claim that the Quantum Encryption system used in the transfer of money , posted at New Scientist and to which I had given a link in one of my earlier replies , would result in an anomalous result , seems to me quite incredible.

I don't remember saying that EPR has nothing whatsoever to do with QM. Anyway, the *viability* of qm is determined by how closely it approximates experimental results. Quantum theory is, essentially, a wave theory, so the principle of linear superposition is a necessary part of it.
I also don't remember saying that the quantum encryption system would result in an anomalous result. What do you mean by "anomalous result"?

Consider the fact that this is an encryption system , where even the slightest mistake made could result in catastrophic misunderstandings. For instance take a three letter word such as cat if any of the three letters are changed the whole meaning would be drastically changed. As for instance , hat , mat , fat , cot ,etc., etc., . Yet this is a system which is now being manufactured and sold commercially , you or I could just go to a shop and buy one.

Well, maybe you could.

Given that this is so it should be possible to conduct the experiment by changing the polarization of one of the spatially separated photons and determining if the other photon also undergoes the relevant change.

You're going to have to have to describe exactly what you mean here. I tried the link you provided (to virginia.edu) and it didn't work. To avoid any misunderstanding on my part, just describe the setup you're talking about, and what you expect to happen, because maybe I'm not getting what you mean by "changing the polarization of one of the spatially separated photons and determining if the other photon also undergoes the relevant change."

Lastly the quote from “Silver Blaze” referred to just this obtuseness which is demonstrated by (a) either not conducting the experiment or (b) obfuscating the results if the experiment has been conducted. Hence the question of why the dog did not bark. i.e., why hasn’t the experiment been carried out.

As I mentioned, according to my understanding of what you mean wrt "the experiment", it's been conducted many times and no FTL effects have ever been observed. But I await your clarification.

 

[McQueen]

How do you make the LEAP from "optical conductivity" which was what I was trying to describe, straight into "electrical conductivity of open circuit"? Doesn't an abrupt change of topic like that causes nosebleeds?

I am sorry for the sudden shift from optical conductivity to electrical conductivity. It was an attempt to try to return to the original topic in the thread.

Charge transport in metals, semiconductors, etc. is a WELL-STUDIED area of solid state physics. Open any solid state physics text if you do not believe me. One can take in everything from the semi-classical Drude model, all the way to the Landau's Fermi Liquid theory, and going into the more exotic Luttinger Liquid theory. Can you tell me where exactly in these descriptions that you see the need for a change?

Here is a link to the Wikepedia Encyclopaedia :
http://en.wikipedia.org/wiki/Electrical_conduction [/URL] on the subject of “electrical conduction.” You can imagine my amazement when I saw nothing at all about
the Landau Fermi Liquid and the even more esoteric Luttinger Liquid Theory or the Weidman- Franz Law in the article , although the enyclopaedia does list separate articles on these subjects. The point is , if the theories you had quoted namely the “Lanadau Liquid Theory “ and the “Luttinger Liquid Theory” were well accepted , well articulated theories on the subject of “electrical conduction” and remember that the Landau Fermi Liquid Theory was formulated almost fifty years ago , there should at least be some reference to the subject in accepted sources . The Hyperphysics web site
[PLAIN] http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html [/URL]( which is an accepted authority ) states that “ ……. it is electrons which are the mobile charge carriers which are responsible for electric current in conductors. “ The Landau Fermi Liquid Theory seems to relate more to the behaviour of electrons in metals , under certain conditions , resulting in such interactions as Umklapp scattering than in any explanation as to how electrical energy is actually conducted in a metal. To simplify my question , are electrons , in this single instance , the actual agents of electrical energy , or are they not ?

 

[ZapperZ]

I am sorry for the sudden shift from optical conductivity to electrical conductivity. It was an attempt to try to return to the original topic in the thread.
Here is a link to the Wikepedia Encyclopaedia :
http://en.wikipedia.org/wiki/Electrical_conduction [/URL] on the subject of “electrical conduction.” You can imagine my amazement when I saw nothing at all about
the Landau Fermi Liquid and the even more esoteric Luttinger Liquid Theory or the Weidman- Franz Law in the article , although the enyclopaedia does list separate articles on these subjects. The point is , if the theories you had quoted namely the “Lanadau Liquid Theory “ and the “Luttinger Liquid Theory” were well accepted , well articulated theories on the subject of “electrical conduction” and remember that the Landau Fermi Liquid Theory was formulated almost fifty years ago , there should at least be some reference to the subject in accepted sources . The Hyperphysics web site
[PLAIN] http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html [/URL]( which is an accepted authority ) states that “ ……. it is electrons which are the mobile charge carriers which are responsible for electric current in conductors. “ The Landau Fermi Liquid Theory seems to relate more to the behaviour of electrons in metals , under certain conditions , resulting in such interactions as Umklapp scattering than in any explanation as to how electrical energy is actually conducted in a metal. To simplify my question , are electrons , in this single instance , the actual agents of electrical energy , or are they not ?[/QUOTE]

I'm sorry, but do you not seem something GLARINGLY wrong here? You are judging the STATE of KNOWLEDGE of physics based on what you learn from Wikipedia?! You do not see the absurdity in this? If it doesn't exist on Wikipedia, it then doesn't exist? Is this where you get all your primary source of info, and this is how you are trying to contradict what I am telling you??!

Then there is no point in my pointing out Ashcroft and Mermin's Solid State Physics Text, or even Mahan's Many-Particle Physics text, etc...etc. Because they are not Wikipedia, they are useless. Why we make graduate students go through these books when there's Wikipedia available for free, AND with simpler, naive version of physics, I have no idea.

Zz.

 

[McQueen]

How is it central? Nothing that I've read about quantum tunneling says anything about FTL.

If you look at the reference :
http://www.aei-potsdam.mpg.de/~mpoessel/Physik/FTL/tunnelingftl.html [/URL] you can see what I meant by the statement that FTL is central to QM. [I] “So, has special relativity been disproved,[b] now that FTL speeds have been measured?[/b] (N.B. Bold letters are mine , for emphasis) The first problem with this naive conclusion is that, while in special relativity neither information nor energy are allowed to be transmitted faster than light, but that certain velocities in connection with the phenomena of wave transmission may well exceed light speed. For instance, the phase velocity of a wave or the group velocity of a wave packet are not in principle restricted below light speed. The speed connected with wave phenomena that, according to special relativity, must never exceed light speed, is the front velocity of the wave or wave packet. “[/I] Since QM is to a large extent committed to Schrodinger’s wave function , it follows that ,logically at least , QM is also committed to FTL .
[QUOTE=Sherlock] As I mentioned, according to my understanding of what you mean wrt "the experiment", it's been conducted many times and no FTL effects have ever been observed. But I await your clarification.[/QUOTE] I agree that over the years several experiments have been conducted on the lines of the EPR , none of which conclusively proved anything one way or another. This was mainly due to lack of the right equipment. Which is why the reference I had given to a commercially viable quantum encryption system is so vitally important. It means that suppose you produce two quantum entangled photons using PDC and send them to two spatially separated locations , the result is consistent enough to use commercially. i.e ., if the two entangled photons have the same polarization at point of origin , then when the polarization of one of the photons is found the polarization of the other is the same to a consistent degree. Do you agree with this so far ? My point is that since the process is consistent , it should be possible to [I] change [/I] the polarization of one of the spatially separated entangled photons and to determine if the other spatially separated photon also undergoes a change in polarization. This would prove conclusively whether FTL does or does not exist . If in fact FTL is found not to exist it would doubts about the whole wave function and QM in general. More important what does this say about the work of Deutsch , Aspect and others ?
[QUOTE=ZapperZ] I'm sorry, but do you not seem something GLARINGLY wrong here? You are judging the STATE of KNOWLEDGE of physics based on what you learn from Wikipedia?! You do not see the absurdity in this? If it doesn't exist on Wikipedia, it then doesn't exist? Is this where you get all your primary source of info, and this is how you are trying to contradict what I am telling you??![/QUOTE]
Right , anticipating such a reaction , if you recall my final question was a fairly simple one . “…….,are electrons , in this single instance , the actual agents of electrical energy , or are they not ?
Also I had visited your web-site and have noted a posting where you yourself had given a link to
[url]http://groups.yahoo.com/group/undernetphysics/message/7[/url]
the same hyperphysics web-site that I had mentioned in my previous post. What am I to make of this?

 

[ZapperZ]

If you look at the reference :
http://www.aei-potsdam.mpg.de/~mpoessel/Physik/FTL/tunnelingftl.html [/URL] you can see what I meant by the statement that FTL is central to QM. [I] “So, has special relativity been disproved,[b] now that FTL speeds have been measured?[/b] (N.B. Bold letters are mine , for emphasis) The first problem with this naive conclusion is that, while in special relativity neither information nor energy are allowed to be transmitted faster than light, but that certain velocities in connection with the phenomena of wave transmission may well exceed light speed. For instance, the phase velocity of a wave or the group velocity of a wave packet are not in principle restricted below light speed. The speed connected with wave phenomena that, according to special relativity, must never exceed light speed, is the front velocity of the wave or wave packet. “[/I] Since QM is to a large extent committed to Schrodinger’s wave function , it follows that ,logically at least , QM is also committed to FTL . [/quote]

This is wrong. You are confusing "non-localitiy" with "FTL". No one who does the EPR type experiments ever claim "FTL". Read any of the papers on this if you don't believe me. What is being claimed to be violated is the EPR notion of "local realism".

And if you do a search on here, I've written at least in a couple of threads why FTL claim in tunneling is also dubious.

[quote]Right , anticipating such a reaction , if you recall my final question was a fairly simple one . “…….,are electrons , in this single instance , the actual agents of electrical energy , or are they not ?
Would you be kind enough to quote from the numerous text-books you had mentioned.[/QUOTE]

Charge carriers in ordinary metals and semiconductors are carried by "quasiparticles" as defined within the Landau Fermi Liquid theory. These can be quasielectrons or quasiholes. These are called quasiparticles because the behavior (such as their effective mass) have been renormalized from the bare particles ("bare" holes are not well-defined, actually). The behavior of these quasiparticles are described by the single-particle spectral function, which in the propagator/field theoretic picture, is defined by the imaginary part of the single-particle Green's function.

Zz.

 

[McQueen]

Zapperz , I sincerely appreciate the thought you have put into your reply and the time you have taken to answer my questions . However bear in mind that what I have to say next might be irritating or even aggravating , depending on your state of mind. I hope you will have the patience to hear me out.

Charge carriers in ordinary metals and semiconductors are carried by "quasiparticles" as defined within the Landau Fermi Liquid theory. These can be quasielectrons or quasiholes. These are called quasiparticles because the behavior (such as their effective mass) have been renormalized from the bare particles ("bare" holes are not well-defined, actually). The behavior of these quasiparticles are described by the single-particle spectral function, which in the propagator/field theoretic picture, is defined by the imaginary part of the single-particle Green's function.
Zz.

What are quasiparticles , when the term was introduced fifty years ago , it referred to ‘virtual particles’ the two terms are often used interchangeably in Russian text-books on QM and I must presume it still has the same connotation. Take the quasiparticle term phonon , it is the QM term for the quantization of vibrations of the lattice and is derived from the Greek word for sound , and in fact is a resultant of the classical physics equivalent of sound vibrations . But just consider for a moment how absurd this sounds ?
Phonons travel at the speed of sound , they are massless particles , so this doesn’t make sense , theoretically they should travel at the speed of light. In the classical usage it makes perfect sense because sound is a wave traveling through a medium . But presumably phonons still exist in space , where there is no medium for them to travel through. How then is this particular phonon speed possible in space ? How the, if the argument is extended , can phonons exist at all in space? OK let’s put another meaning to the word quasiparticle and consider it to be something the electron resembles when it interacts with vibrations within the crystal lattice of the conductor , (Note: these vibrations still have to travel at the speed of sound when in space without the help of a medium and this is something that has to be explained.) But suppose it is possible and that the electron in this state is able to project something very similar to itself , each of which carries the same spin, charge and momentum as the original particle. So now the electron is capable of making ‘virtual’ clones of itself. Not only that but these ‘virtual’ clones are able to influence matter just as if they were the real thing , this is truly extraordinary ?? Consider for just a moment , you had accused me in your second last post of wanting simplistic physics. Is this theory a viable alternative. Alright , consider next the drift velocity of electrons in a conductor , the mean free path etc ., A man walking at 4 Km/hr is traveling at about a billion times the speed of an electron in a conductor. Wouldn’t it be simpler to theorize that electrical energy is carried by photons and to determine how free electrons and valence electrons in a conductor are able to absorb and emit low energy photons in order to do this ?

 

[ZapperZ]

What are quasiparticles , when the term was introduced fifty years ago , it referred to ‘virtual particles’ the two terms are often used interchangeably in Russian text-books on QM and I must presume it still has the same connotation.

No, this is wrong. Quasiparticles as defined in the Fermi Liquid theory are NOT virtual particles. In ordinary metals, if you solve the propagator, the quasiparticles have INFINITE lifetime, and thus is a delta function in the energy spectrum. This is not the behavior of a virtual particles. Besides, you can MEASURE direction the behavior of quasiparticles. When you measure the dispersion in a material, you are measuring the dispersion of the quasiparticles. When was the last time you could do the same with virtual particles. So your whole description of quasiparticles being identical to virtual particles is wrong.

Take the quasiparticle term phonon ,

Wrong. A phonon is not a quasiparticle. A phonon is a collective excitation, similar to a photon being an excitation out of a vacuum state.

Zz.

 

[vanesch]

Phonons travel at the speed of sound , they are massless particles , so this doesn’t make sense , theoretically they should travel at the speed of light. In the classical usage it makes perfect sense because sound is a wave traveling through a medium . But presumably phonons still exist in space , where there is no medium for them to travel through.

That's not correct. "Phonons" are eigenstates of the energy/momentum 4-vector of the vibrational degrees of freedom of a lattice, and because of the formal ressemblance to free field theories in fundamental QFT, you can call them "particles" of some kind, because the mathematics is the same. It is a useful mental picture, that's all. In reality you're working with eigenstates of the hamiltonian of your lattice. But because the mathematics is the same as the QFT of free particles "in space", of course a lot of properties of these solutions look exactly like the solutions you have for free particles in space, so it is a very very useful mental picture. You will for example also have the equivalent of energy and momentum conservation in perturbative interactions and all other kinds of things.

But, of course, quasi-particles cannot leave the crystal :-)

Mind you, when I was in high school, my idea was to have a positron source by accelerating holes in a semiconductor to get them out of the xtal... but I've grown up in the mean time

 

[Sherlock]

If you look at the reference :
http://www.aei-potsdam.mpg.de/~mpoes...nelingftl.html you can see what I meant by the statement that FTL is central to QM. “So, has special relativity been disproved, now that FTL speeds have been measured? (N.B. Bold letters are mine , for emphasis) The first problem with this naive conclusion is that, while in special relativity neither information nor energy are allowed to be transmitted faster than light, but that certain velocities in connection with the phenomena of wave transmission may well exceed light speed. For instance, the phase velocity of a wave or the group velocity of a wave packet are not in principle restricted below light speed. The speed connected with wave phenomena that, according to special relativity, must never exceed light speed, is the front velocity of the wave or wave packet. “ Since QM is to a large extent committed to Schrodinger’s wave function , it follows that ,logically at least , QM is also committed to FTL .

Nice link, lots of good references, thanks.

As the author of the review articles says, the consensus is that no FTL signal has been measured.

I've read one of Chiao and Kwiat's papers (involving quantum non-local correlations) in which they explicitly state that no energy has been transferred FTL.

My textbook (Bohm, 1950) states in a few places that quantum non-local correlations do not imply FTL transmissions.

So, you'll have to lay out your reasons for thinking that QM is committed to FTL

I agree that over the years several experiments have been conducted on the lines of the EPR , none of which conclusively proved anything one way or another. This was mainly due to lack of the right equipment. Which is why the reference I had given to a commercially viable quantum encryption system is so vitally important. It means that suppose you produce two quantum entangled photons using PDC and send them to two spatially separated locations , the result is consistent enough to use commercially. i.e ., if the two entangled photons have the same polarization at point of origin , then when the polarization of one of the photons is found the polarization of the other is the same to a consistent degree. Do you agree with this so far ? My point is that since the process is consistent , it should be possible to change the polarization of one of the spatially separated entangled photons and to determine if the other spatially separated photon also undergoes a change in polarization. This would prove conclusively whether FTL does or does not exist .

I know little about PDC. Are you saying that the two photons (which, as I understand it, are harmonics of the pump photon) transmitted by the nonlinear crystal are always polarized the same way --- or is it that their polarizations are always related?

The encryption systems involve parallel settings of the polarizers, don't they? I don't know for sure.

Anyway, say you've detected photon 1 wrt a certain setting of your polarizer. Now, you can change the setting of the polarizer that photon 2 is incident on while photon 2 is in flight. The probability of coincidental detection, in the ideal, is given as cos^2(theta) by qm, where theta is the angular difference between the polarizers. In effect, as you change the setting of the polarizer that photon 2 is incident on, you change the probability of detecting photon 2. How does this tell you whether FTL does or does not exist?

If in fact FTL is found not to exist it would doubts about the whole wave function and QM in general. More important what does this say about the work of Deutsch , Aspect and others ?

I don't know about Deutsch's work, but I've read a few of Aspect et al.'s papers and from what I understand they don't say anything about FTL, but only about whether local hidden variable (lhv, or local realist) formulations for their experimental setups are consistent with the results (and also whether the qm formulation is consistent with the results).

The consensus is that the lhv formulation isn't empirically viable. But, it's the hidden variable or realist part of the lhv formulations that is at odds with the results, not locality --- since the locality condition isn't really a locality condition but rather just an independence condition. A and B aren't independent of each other -- that is, the results at A and B are related to each other. But this has to do with the experimental setup, and not with them being causally related to each other during a given coincidence interval. As qm has it anyway, even without the Bell tests, the polarization of photon 1 is not defined prior to detection, and the polarization of photon 2 is not defined prior to detection (only the relationship between the polarizations of photon 1 and photon 2 is defined prior to detection). So, given the current understanding of polarization, the photons incident on the polarizers during a given coincidence interval can't be assigned specific polarization prior to detection, and hence a local realist (ie., a 'classical') description (at least wrt the current state of the art of polarization) of the incident photons isn't viable for all joint polarizer settings.

But again, at least afaik, quantum theory is not committed to FTL. (Of course, as far as anybody knows, the correlations might be due to FTL transmissions, but such an explanation isn't necessitated, so the assumption of locality is retained.) So far, from what you've written and referred to, such an FTL committment doesn't seem to follow. So, it might be good if you spell out your logical chain of reasoning that leads you to the conclusion that you're advocating.

 

[McQueen]

Anyway, say you've detected photon 1 wrt a certain setting of your polarizer. Now, you can change the setting of the polarizer that photon 2 is incident on while photon 2 is in flight. The probability of coincidental detection, in the ideal, is given as cos^2(theta) by qm, where theta is the angular difference between the polarizers. In effect, as you change the setting of the polarizer that photon 2 is incident on, you change the probability of detecting photon 2. How does this tell you whether FTL does or does not exist?

You don’t have to detect the photon before changing the polarization, because that has already been established to a consistent degree. And if your argument is to hold water , shouldn’t the probability of a photon being detected at A also change with the detection of the photon at B , something which apparently does not seem to happen ?

But again, at least afaik, quantum theory is not committed to FTL. (Of course, as far as anybody knows, the correlations might be due to FTL transmissions, but such an explanation isn't necessitated, so the assumption of locality is retained.) So far, from what you've written and referred to, such an FTL committment doesn't seem to follow. So, it might be good if you spell out your logical chain of reasoning that leads you to the conclusion that you're advocating.

If we look at the background of QM , it becomes clear that FTL is in fact central to many of the basic precepts of QM. I think that we can all agree that the matter waves postulated by Louis de Broglie , which became central to wave-particle duality and Schrodinger’s wave function are one of the key tents of QM. Yet according to de Broglies theory matter waves ( waves of probability according to Schrodinger ) which travel with an electron , move faster than the speed of light . And “……..the slower the electron the faster the velocity of its associated wave. (N.B ., Quote from Sir George Thomson , winner of the Nobel Prize in Physics. From his book “The Atom”) Thus it is the matter wave which guides the electron as to where to go. This being so , how is it possible to claim that FTL is not central to QM. Even the most basic foundations of QM have this concept of FTL inbuilt into them. If we take another approach , we get the same result. What is the size of an electron ? From the fact that an electron can give up all its energy on impact , it must be reasoned that its dimensions are fairly compact and localized , on the other hand since an electron can be influenced by another charge placed at a distance in space , the influence of the electron can be taken as being almost infinite. It is therefore difficult to come to a conclusion as to the exact size of an electron. This interaction or influence that the electron experiences from other electrons is what led to Schrodingers blurred or smeared (electron cloud ) description of the electron within the atom , which later was proved to be wrong. One way to avoid all this confusion is by the particle view of light . Thus if by the wave view of light we have : particle –> electromagnetic field –> particle . Then on the particle view we would have : particle -> photon -> particle . i.e., a charged particle generates a photon which is absorbed by another particle. This is the mechanism which is responsible for the force acting on these particles.

 

[McQueen]

Wrong. A phonon is not a quasiparticle. A phonon is a collective excitation, similar to a photon being an excitation out of a vacuum state.

Shouldn't the correct term be a "Virtual photon".

But, of course, quasi-particles cannot leave the crystal :-)

Is that why phonons travel at the speed of sound in space where there is no medium for which for them to travel through.

 

[ZapperZ]

Shouldn't the correct term be a "Virtual photon".

Why are you so hung-up on the NAME but not the physics involved? I could call it "cow photon", and it won't change a thing about the physics.

I still think you are "learning" these things via bits and pieces that you get off the web. I would be very suspicious of my knowledge if I were you.

Zz.

 

[McQueen]

Why are you so hung-up on the NAME but not the physics involved? I could call it "cow photon", and it won't change a thing about the physics.

I still think you are "learning" these things via bits and pieces that you get off the web. I would be very suspicious of my knowledge if I were you.

OK why can phonons travel at the speed of sound in space. Or are they restricted to within the crystal and if so why ?

 

[vanesch]

OK why can phonons travel at the speed of sound in space. Or are they restricted to within the crystal and if so why ?

They are of course restricted to the crystal. In fact, it does not even make sense to say so, because they are really a numbering scheme of the stationary states of the lattice vibrations ;

You could just as well ask if reciprocal vectors are restricted to the crystal or not.

The reason why phonons are a bit particle-like is because the mathematics looks much the same as the mathematics of the stationary states of the free Dirac field ; these stationary states are called electrons.

 

[ZapperZ]

OK why can phonons travel at the speed of sound in space. Or are they restricted to within the crystal and if so why ?

Considering that a phonon is DEFINED as the quanta of LATTICE VIBRATIONS, how do you propose to have this thing travel in space where there are no LATTICE VIBRATIONS? Phonons are not even well defined in liquid (even though there are loose usage of that term within that scenario), and certainly not defined in a gas. So think of how absurd it is to to talk about it in vacuum. You are taking the concept and then twisting it into ways it wasn't meant to be used.

Zz.

 

[McQueen]

Considering that a phonon is DEFINED as the quanta of LATTICE VIBRATIONS, how do you propose to have this thing travel in space where there are no LATTICE VIBRATIONS? Phonons are not even well defined in liquid (even though there are loose usage of that term within that scenario), and certainly not defined in a gas. So think of how absurd it is to to talk about it in vacuum. You are taking the concept and then twisting it into ways it wasn't meant to be used.

Lattice vibrations , yes , but how do they travel?Are they specially empowered , so that they can control their speed ? I know phonons have , or were , for a long time a well accepted part of physics. But still do they have some kind of special dispensation , that allows them to travel at specific speeds namely that of sound. The whole of Coulomb's theory can be derived from the fact that the photons has no mass. OK so the phonon is not actually a partcile , but surely it still is a vibration?

 

[Sherlock]

You don’t have to detect the photon before changing the polarization, because that has already been established to a consistent degree.

If the photons are polarization-entangled (which is what we want isn't it?), then their polarization isn't established prior to detection. Their polarization is random. Only the entanglement relationship is established -- and, depending on the photon pair source, then with polarizers aligned, A and B will always register the same results, or A and B will always register opposite results.
So let's say we're dealing with polarization-entangled photons that, with polarizers aligned, always register the same result at A and B for a given pair (either both detect, or both don't detect, with polarizers aligned). This is the entanglement relationship between paired photons that are produced by atomic calcium cascades, which were used by Aspect et al. in their 1982 experiment involving time-varying analyzers. Pairing the photons involves associating them with intervals controlled by coincidence circuitry (in the case of the Aspect experiment they wanted to pair photons emitted by the same atom). Since the emission time is a random variable, a coincidence interval is initiated by a detection at either A or B.

And if your argument is to hold water , shouldn’t the probability of a photon being detected at A also change with the detection of the photon at B , something which apparently does not seem to happen ?

The average photon count at A (or B) for, say, a 5 minute run, with polarizer in place is 1/2 what it is without the polarizer. The photon flux at A doesn't depend in any way on what you might do to the B side, and vice versa.
Individual detection is random, uncontrollable, unpredictable. What is controllable is the rate of coincidental detection, which is a function of the angular difference between the polarizers. This suggests that properly paired photons refer to disturbances that are related prior to detection, presumably because, in the process we're considering, they were emitted by the same atom. And, that's how qm treats the situation. No FTL implied.
As I mentioned before, there's no experiment (yet), afaik, that can definitively ascertain that FTL transmissions aren't happening between A and B during a given coincidence interval. But, there's no particular reason to suppose that the correlations must be due to anything FTL. It seems likely that the entanglement is produced via the emission process. The fact that there isn't any geometrical or mechanical visualization accompanying the qm account doesn't reinforce the notion that FTL transmissions must be involved.

If we look at the background of QM , it becomes clear that FTL is in fact central to many of the basic precepts of QM. I think that we can all agree that the matter waves postulated by Louis de Broglie , which became central to wave-particle duality and Schrodinger’s wave function are one of the key tents of QM. Yet according to de Broglies theory matter waves ( waves of probability according to Schrodinger ) which travel with an electron , move faster than the speed of light . And “……..the slower the electron the faster the velocity of its associated wave. (N.B ., Quote from Sir George Thomson , winner of the Nobel Prize in Physics. From his book “The Atom”) Thus it is the matter wave which guides the electron as to where to go. This being so , how is it possible to claim that FTL is not central to QM. Even the most basic foundations of QM have this concept of FTL inbuilt into them.

How is it possible that David Bohm wrote a 646 page textbook on quantum theory without mentioning any of these FTL considerations, except to say that, wrt quantum correlations such as we're considering here, events at A and B are not affecting each other. (Maybe I've missed something.)

Bohm and deBroglie were around at the same time weren't they? If what you say is true about matter waves moving FTL, then how did Bohm get by without mentioning it in a qm textbook?

I'm aware that Bohm published a non-local hidden variable formulation of qm after he wrote the textbook. But, afaik, that formulation was not meant to be a serious contender, but was presented to show that such an alternative, hidden variable formulation (albeit an explicitly non-local one) was possible. Maybe he did it to show that hidden variable formulations are required to be explicitly non-local. I don't know. But, it's clear in his quantum theory textbook that he's proceeding under the assumption that nature obeys the principle of locality. There are several places where he emphasizes this, and also several places where he emphasizes that hidden variable theories are not possible in a local universe wherein the experimental determination of natural processes is limited by a fundamental quantum of action and the uncertainty relations.

 

[DrChinese]

I know little about PDC. Are you saying that the two photons (which, as I understand it, are harmonics of the pump photon) transmitted by the nonlinear crystal are always polarized the same way --- or is it that their polarizations are always related?

A quick note about PDC, because it can be a little confusing. There are 2 types of PDC:

Type I PDC:
The output photons of a tuned non-linear crystal have parallel and known spin, and are NOT in superposition of spin states initially. Their spin is orthogonal (perpendicular) to that of the pump photon. So they are entangled, but not as to spin - which sounds wrong. But this is easily fixed so that we have a usable Bell state for an experiment.

This is accomplished by using 2 crystals instead of one. The crystals are placed in series but 90 degrees apart. The pump stream is placed at a 45 degree angle relative to the crystals. There is a mixing of 2 output beams - i.e. the photon pair comes out of one crystal or the other, but you don't know which. The result is a good superposition of H>H> and V>V> states that can then be tested per usual, with identical polarization.

Type II PDC:
The output photons of a tuned non-linear crystal have perdendicular (orthogonal) and UNknown spin, and ARE in superposition of spin states initially. The superposition is H>V> and V>H>. This only needs a single crystal.

It's a little more complicated than my explanation implies, but this al least disctinguishes the 2 types. I am working on a new page for my site that will explain this pictorially. I will post this when it is available.

 

[Sherlock]

A quick note about PDC, because it can be a little confusing. There are 2 types of PDC:
Type I PDC:
The output photons of a tuned non-linear crystal have parallel and known spin, and are NOT in superposition of spin states initially. Their spin is orthogonal (perpendicular) to that of the pump photon. So they are entangled, but not as to spin - which sounds wrong. But this is easily fixed so that we have a usable Bell state for an experiment.
This is accomplished by using 2 crystals instead of one. The crystals are placed in series but 90 degrees apart. The pump stream is placed at a 45 degree angle relative to the crystals. There is a mixing of 2 output beams - i.e. the photon pair comes out of one crystal or the other, but you don't know which. The result is a good superposition of H>H> and V>V> states that can then be tested per usual, with identical polarization.
Type II PDC:
The output photons of a tuned non-linear crystal have perdendicular (orthogonal) and UNknown spin, and ARE in superposition of spin states initially. The superposition is H>V> and V>H>. This only needs a single crystal.
It's a little more complicated than my explanation implies, but this al least disctinguishes the 2 types. I am working on a new page for my site that will explain this pictorially. I will post this when it is available.

Ok, thanks DrC. I've been meaning to read up on this stuff. :-)

As I understand McQueen's proposed experiment, it would have to involve polarization-entangled photons wrt which the polarization has "already been established to a consistent degree", as he puts it, prior to detection. So, his experiment is impossible to implement. Or is it?

Do you understand what he's talking about?

 

[Sherlock]

If we take another approach , we get the same result. What is the size of an electron ? From the fact that an electron can give up all its energy on impact , it must be reasoned that its dimensions are fairly compact and localized , on the other hand since an electron can be influenced by another charge placed at a distance in space , the influence of the electron can be taken as being almost infinite. It is therefore difficult to come to a conclusion as to the exact size of an electron. This interaction or influence that the electron experiences from other electrons is what led to Schrodingers blurred or smeared (electron cloud ) description of the electron within the atom , which later was proved to be wrong. One way to avoid all this confusion is by the particle view of light . Thus if by the wave view of light we have : particle –> electromagnetic field –> particle . Then on the particle view we would have : particle -> photon -> particle . i.e., a charged particle generates a photon which is absorbed by another particle. This is the mechanism which is responsible for the force acting on these particles.

The consensus among physicists (from what I've read) seems to be that quantum phenomena are essentially wave like. But, who really knows? There is, as pertains to the title of your thread, still a controversy. Exactly what photons and electrons correspond to in nature is unknown. They're mathematical constructs applied to certain phenomena. In the attempt to develop a picture of quantum reality in terms of familiar analogs it's observed that some aspects of experimental results lend themselves to a wave interpretation and some to a particle interpretation. Hence, the necessary wave-particle duality wrt our apprehension and comprehension of quantum phenomena.

It's not really clear how you propose to solve the dilemma of qualitatively describing the quantum realm.

 

[ZapperZ]

Lattice vibrations , yes , but how do they travel?Are they specially empowered , so that they can control their speed ? I know phonons have , or were , for a long time a well accepted part of physics. But still do they have some kind of special dispensation , that allows them to travel at specific speeds namely that of sound. The whole of Coulomb's theory can be derived from the fact that the photons has no mass. OK so the phonon is not actually a partcile , but surely it still is a vibration?

These are the times where I just want to smack someone on the head and say "READ THE DAMN TEXTBOOK!"

... but I won't! :)

Zz.

 

[McQueen]

These are the times where I just want to smack someone on the head and say "READ THE DAMN TEXTBOOK!"
... but I won't! :)

For which I am truly thankful. A few questions. Am I right in thinking that Schrodinger’s wave mechanics is a mathematical theory in which calculations are made of quantities which can be measured experimentally. Obviously , from the success of the theory , the answers given by the calculations can be verified , but isn’t it true that the intermediate stages in these calculations have no physical meaning ? For example simple atom structures can be explained mathematically. In a stationary state the wave reduces to a simultaneous vibration of all parts of the atom , which thus resembles a vibrating system. ( Presumably it is these vibrations that give rise to quasiparticles and phonons ?) For complex atoms the waves are determined by a mathematical process which can only be interpreted geometrically in terms of space of many dimensions. This means that the waves have no physical meaning. I can understand that mathematically this makes sense , because the extra dimensions can simply be explained by attributing different numbers or symbols to them , but where does this leaves things in terms of physical quantities ?

 

[selfAdjoint]

Obviously , from the success of the theory , the answers given by the calculations can be verified , but isn’t it true that the intermediate stages in these calculations have no physical meaning ?

The point of the mathematical physicists' algebraic local quantum theory is that all the predictions of quantum theory can be coded in an abstract Hilbert space and a suitable algebra of operators on it, satisfying certain axioms. This has SPECIFICALLY nothing to do with spacetime or our world.

You have to look outside QM itself for such relationship to the world; that is why the "measurement" questions, which seem so vacuous and philosophical refuse to go away.

No advance in the quantum side of physics makes any improvement on this; superstring theory is just as abstract-mathematical as nonrelativistic QM. That is why some of us have long placed our hopes and expectations on the gravity side of physics. "Gravity is spacetime curvature", even if wrong or just "effective", is an answer on a different level from anything QM gives.

 

[McQueen]

You have to look outside QM itself for such relationship to the world; that is why the "measurement" questions, which seem so vacuous and philosophical refuse to go away.

No advance in the quantum side of physics makes any improvement on this; superstring theory is just as abstract-mathematical as nonrelativistic QM. That is why some of us have long placed our hopes and expectations on the gravity side of physics. "Gravity is spacetime curvature", even if wrong or just "effective", is an answer on a different level from anything QM gives

Agreed. But just consider for the moment that , leaving aside for the moment anything to do with the nucleus , the whole of Quantum Mechanics resembles an inverted pyramid , with the whole weight of it resting on the properties of the photon and wave particle duality. Yet , what if the photon does not really reflect this duality ? All the premises built up from this point would collapse. It could be argued that De Broglie’s original hypotheses was not based upon the properties of the photon at all but upon matter energy equivalence . Yet this reasoning requires a huge leap since it would leave out an enormous factor , that of energy . Particle accelerators have shown that massive amounts of energy are required to bring about matter – equivalence effects in sub-atomic particles. Thus it was the photon that was and is the ultimate proof of wave-particle duality. Yet if we think lucidly , without letting any considerations get in the way , it is a highly unlikely scenario , requiring an almost alchemical amount of esoteric input. At one time it was thought that wave-particle duality was inevitable because it explained why electrons did not radiate away all their energy and spiral into the nucleus , yet with the advent of experimental proof of the Lamb effect and the discovery of self-interaction of electrons wave particle duality has to a large extent been obviated.
http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/lamb.html [/URL]
By this theory the electron balances its orbit within the atom through constant emission and absorption of “virtual” photons. If the subject is considered in a non-partisan and unbiased manner , this should make greater sense than wave-particle duality , because exactly similar “virtual” transactions and transformations are observed within the nucleus. The neutron constantly changing within the nucleus to a proton and back again. Thus the self-interaction of electrons lends continuity to the process while by contrast wave-particle duality opens completely new methodology. ( when viewed from this point of view). So if the photon is not a particle and it is not a wave what could it be ? Probably the simplest most logical answer to this question is also the correct one. Namely that the photon is neither a particle or a wave but a [symbiosis} of the two. It is a wave that has all the properties of a particle. Look at hyper-sonic sound waves , they behave to a certain extent like particles but everyone knows that they are waves. The photon might be similar , only dealing with frequencies many millions of times greater than that of sound , where the difference between particle and wave is almost indiscernible.

 

[ZapperZ]

Agreed. But just consider for the moment that , leaving aside for the moment anything to do with the nucleus , the whole of Quantum Mechanics resembles an inverted pyramid , with the whole weight of it resting on the properties of the photon and wave particle duality. Yet , what if the photon does not really reflect this duality ? All the premises built up from this point would collapse.

But if this is true, then a lot of our measurement would make NO SENSE, and what we interpret and observe would not be consistent. My photoemisson experiments would give strange results and all those optical conductivity experiments would give weird measurements, because they all made use of the QM description of light. This is what would happen when the starting premise is wrong, and when you try to use it to study other things, it will start to fall apart.

Yet, no such thing is occurring. We know so much about light and its interaction with matter that we USE it to study the properties of that matter. Go to any synchrotron center if you don't believe me. What you are claiming is inconsistent with experimental practices and evidence.

Zz.

 

[McQueen]

My photoemisson experiments would give strange results and all those optical conductivity experiments would give weird measurements, because they all made use of the QM description of light. This is what would happen when the starting premise is wrong, and when you try to use it to study other things, it will start to fall apart.
Yet, no such thing is occurring. We know so much about light and its interaction with matter that we USE it to study the properties of that matter. Go to any synchrotron center if you don't believe me. What you are claiming is inconsistent with experimental practices and evidence

Are these the same photoemission experiments conducted by Einstein , are any of them online , I would appreciate a reference if they are. But to come back to the question at hand . Would the experiments give strange results ? Take your example of optical conductivity experiments. Till quite recently the explanation given for the transmission of light through substances like glass did not depend upon photons at all , in fact photons hardly came into it. The explanation was ( and still is ?) as follows: “The distortion of the electron cloud of an atom by an electric field , in this case the electric field of the light, is described as polarization. As a result of polarization, some of the energy may be absorbed, i.e., converted into elastic deformations (phonons), and consequently heat. On the other hand, the polarization may propagate as a material-bound electromagnetic wave with a different speed than light. As you can see there is no reference to photons although phonons are mentioned with regard to the conduction of heat. Take electricity as another example , electrical motors were being designed since Faraday’s time , which worked perfectly well , although in actual fact over the course of the next 150 years , the theory of electricity underwent many changes . What is relevant is not whether those changes were for the better ( of course they were ) but the fact that many experiments worked even without these changes and were at the time thought to be the genuine explanation for these phenomenon . They were only improved upon because of an openness to consider alternative theories. What about gravity , think of catapulting the Voyager spacecraft around the planets to distances of billions of miles, without having any idea as to what it is. We might know how gravity works but we don’t know ( for certain) what it is , or why it works in the way it does. So faced with theories such as the disembodiment of sub-atomic particles as for instance with neutrons having definite size and mass , so that they can in two places at once , or FTL communication , both of which explanations are offered as a reason for the results of the Double Slit Experiment with single particles , is it not possible or even plausible to at least examine alternate explanations. Especially when , as I had pointed out , the whole of these theories stem from the properties of the photon which can be both wave like and particle like. What if the photon is not a particle or a wave but something totally different ? It would no longer make sense to attribute these properties to other sub-atomic particles , because then the photon would have nothing in common with these particles.

 

[inha]

What if the photon is not a particle or a wave but something totally different ?

But it already is something totally different. It's not a particle nor is it a wave but a photon. Using the photon picture one can calculate both XRD spectra and IXS spectra that agree with experiments. Wouldn't that be quite a feat for photons if they didn't even exist?

 

[ZapperZ]

Are these the same photoemission experiments conducted by Einstein , are any of them online , I would appreciate a reference if they are. But to come back to the question at hand . Would the experiments give strange results ? Take your example of optical conductivity experiments. Till quite recently the explanation given for the transmission of light through substances like glass did not depend upon photons at all , in fact photons hardly came into it. The explanation was ( and still is ?) as follows: “The distortion of the electron cloud of an atom by an electric field , in this case the electric field of the light, is described as polarization. As a result of polarization, some of the energy may be absorbed, i.e., converted into elastic deformations (phonons), and consequently heat. On the other hand, the polarization may propagate as a material-bound electromagnetic wave with a different speed than light. As you can see there is no reference to photons although phonons are mentioned with regard to the conduction of heat. Take electricity as another example , electrical motors were being designed since Faraday’s time , which worked perfectly well , although in actual fact over the course of the next 150 years , the theory of electricity underwent many changes . What is relevant is not whether those changes were for the better ( of course they were ) but the fact that many experiments worked even without these changes and were at the time thought to be the genuine explanation for these phenomenon . They were only improved upon because of an openness to consider alternative theories. What about gravity , think of catapulting the Voyager spacecraft around the planets to distances of billions of miles, without having any idea as to what it is. We might know how gravity works but we don’t know ( for certain) what it is , or why it works in the way it does. So faced with theories such as the disembodiment of sub-atomic particles as for instance with neutrons having definite size and mass , so that they can in two places at once , or FTL communication , both of which explanations are offered as a reason for the results of the Double Slit Experiment with single particles , is it not possible or even plausible to at least examine alternate explanations. Especially when , as I had pointed out , the whole of these theories stem from the properties of the photon which can be both wave like and particle like. What if the photon is not a particle or a wave but something totally different ? It would no longer make sense to attribute these properties to other sub-atomic particles , because then the photon would have nothing in common with these particles.

Einstein's "photoelectric effect" model is PRIMITIVE. I have given several citation of a review of photoemission experiments, especially angle-resolved photoemission on high-Tc superconductors. ARPES, resonant photoemission, x-ray photoemission, etc.. are all techniques that were built using the photon picture, NEVER using "wave" picture of light. And when I say that, I am not distinguishing light as "particle" instead of a "wave", because in QM, that dichotomy is meaningless.

I don't think I have the patience to once again describe optical conductivity. I don't have the energy anymore to correct the popular misconception of "electron cloud by atom field" when it comes to solid. Even after saying that bulk property of a solid often has no resemblance to the property of individual atoms, this still doesn't get the message through. And in glass, what "electron cloud" are we talking about? There's no conduction electron. The electron cloud for each of the atom? Then how come I rearrange the atom and get a different property? Or I have light coming in different crystallographic direction and get different transmission? Your classical description is adequate, but it doesn't give the complete picture. Like in any other phenomena, the classical picture starts running into trouble when you try to stretch it into the extreme situation.

One thing Einstein did not see during his life time was the multiphoton photoemission process. Here, the semi-log plot of the photocurrent vs. instensity changes in slope DISCRETELY according to how many photons is required to cause the emission of a single photoelectrons. Again, I have described this phenomenon more than once, especially since I have observed this myself. Now go and explain THAT with your classical picture.

Zz.

 

[McQueen]

One thing Einstein did not see during his life time was the multiphoton photoemission process. Here, the semi-log plot of the photocurrent vs. instensity changes in slope DISCRETELY according to how many photons is required to cause the emission of a single photoelectrons. Again, I have described this phenomenon more than once, especially since I have observed this myself. Now go and explain THAT with your classical picture.

There’s one thing I can’t understand in all this , though the references you had made to multiphoton photoemission do seem to throw some (light) on the subject. Take the reflection of light , when we look out of the window into the garden on a sunny day , we see brilliant colours ( there’s no need at the moment to go into optical conductivity) , and this is the result of the electrons in the objects ( flowers etc., ) that we see outside the window , rapidly absorbing and re-emitting photons of a given energy. This absorption and emission has to take place at a very rapid rate at least at around 10^^-18 secs for each absorption and emission. Given that this is so , could it be that individual electrons are continuously emitting at this rate , for instance if we are dealing with green light at 550 nm. Does it mean that single electrons are emitting at 5.4 x 10^^14 photons per sec. Or is it an intermittent and uncoordinated affair with individual electrons absorbing an electron and then after some time firing off an electron and then going quiescent for some time and then absorbing and emitting another electron. The reason that I said your references throw some light on this subject is because apparently to trigger photo emission at below the threshold through multiple photons requires powerful light sources such as lasers , which shows that it needs a concentration of energy to achieve electron ejection below the threshold level. Am I making any sense or am I talking through my hat.

 

[ZapperZ]

There’s one thing I can’t understand in all this , though the references you had made to multiphoton photoemission do seem to throw some (light) on the subject. Take the reflection of light , when we look out of the window into the garden on a sunny day , we see brilliant colours ( there’s no need at the moment to go into optical conductivity) , and this is the result of the electrons in the objects ( flowers etc., ) that we see outside the window , rapidly absorbing and re-emitting photons of a given energy.

Please justify this description. How do you know this is the valid explanation for what you are describing?

Zz.

 

[alfredblase]

FYI, I stopped seriously reading your article after this introduction. The question has been answered for quite a while now: light is neither a (classical) particle nor a (classical) wave. Light is some quantum mechanical thing to which the classical notions of particles and waves are good approximations under various circumstances.

Oh dear oh dear, even a dunce like me can contradict the best comment in this thread... hehe or maybe I'm wrong. What about the Schrodinger WAVE equation? What about the optical Bloch equations? The former treats light all mathematical objects as waves, and the latter can be used to predict the TRANSITION RATES (classical particle notion if ever I heard one) of atoms in illuminated by laser light. A combination of Schrodinger formalism and notions such as Rabbi FREQUENCY are employed on the way to the optical Bloch equations.

emm maybe I AM a dunce and I'm getting confused by basic stuff, but common.. Schrodinger WAVE equation... its not an approximation is it? hahaha

But I think you have a point. No one REALLY understands QM, its obviously lacking badly as far conceptualising goes, a real failure as far as a physicist is concerned, perhaps not a mathematician though... Light is bound to be something thing other than a particle or a wave...or not hehe ... String Theory might provide a more definate answer in time?...

 

[ZapperZ]

Oh dear oh dear, even a dunce like me can contradict the best comment in this thread... hehe or maybe I'm wrong. What about the Schrodinger WAVE equation? What about the optical Bloch equations? The former treats light all mathematical objects as waves, and the latter can be used to predict the TRANSITION RATES (classical particle notion if ever I heard one) of atoms in illuminated by laser light. A combination of Schrodinger formalism and notions such as Rabbi FREQUENCY are employed on the way to the optical Bloch equations.
emm maybe I AM a dunce and I'm getting confused by basic stuff, but common.. Schrodinger WAVE equation... its not an approximation is it? hahaha
But I think you have a point. No one REALLY understands QM, its obviously lacking badly as far conceptualising goes, a real failure as far as a physicist is concerned, perhaps not a mathematician though... Light is bound to be something thing other than a particle or a wave...or not hehe ... String Theory might provide a more definate answer in time?...

But the SOLUTION to the Schrodinger equation, usually called the "wavefunction", is not a PHYSICAL wave. This is NOT the wave you see or detect! For a system of more than 1 particle, this wavefunction sits in a CONFIGURATION space, not in real space. This wavefunction is also NOT equivalent to the "wave" picture in classical light/EM theory, i.e. it is not the wave equation that you get from Maxwell equations. Don't be mislead by the NAME. Instead, pay attention to the PHYSICS.

And it is silly to say "no one really understand QM", as if we "understand" classical mechanics any better when it fails to describe a whole zoo of phenomena that QM can. Maybe it's our stubborness in trying to FIT nature in the classical picture that is causing all of these weird conceptual problems. You have a square object, and you're trying to force it through a round hole. When you can't get it through, rather than attributing the fact that you're trying to fit an object that isn't meant to go through that hole, you blame the hole!

Zz.

 

[alfredblase]

Ok so QM doesn't consider classical waves, I stand corrected and apologize for displaying my ignorance. :P

But at the risk of displaying it again, like Hurkyl said, "Light is some quantum mechanical thing"... Doesn't sound like he or anyone else understands it, and by understand I mean feel comfortable with the PHYSICS not just the maths. (There is a reason that physics sounds like physical I think). Physics is more than just a bunch of equations, there has to be a conceptual understanding of the problem too. And we can only concieve objects in our head that we are familiar with. By familiar I mean that we may have seen something in everyday physical life that aids our imagination. I mean we need something we can picture or else its just maths. But even the idea of a point it ridiculous, especially if we extend the argument to fundamental particles with mass... infinite density and all that... If there is some one out there who can explain what it is that people who really understand QM picture when they think of light, valid in all circumstances, not just in the classical limit of this, or the classical limit of that, then I will stand corrected on this point too. Thanks ;) I'm sorry but QM is deeply unatractive because it seems like just a bunch of yucky maths. If the general physics community is really ok with that then perhaps we should do away with physics departments altogether and replace them with applied mathematics departments. At least that would make sense. But it would be a shame too. Maths should be a modelling tool to work on problems/objects that we concieve in my oipinion. I mean what is a measured result if not a conception? Maths without conceptions is just counting stars, and saying that you own them. Its accountancy no more. There's no truth or beauty in that.

 

[ZapperZ]

Ok so QM doesn't consider classical waves, fair enough I stand corrected.
But like Hurkyl said, "Light is some quantum mechanical thing"... Doesn't sound like he or anyone else understands it, and by understand I mean feel comfortable with the PHYSICS not just the maths. Physics is more than just a bunch of equations, there has to be a conceptual understanding of the problem too. And we can only concieve objects in our head that we are familiar with. By familiar I mean, a fuzzy point or a wave, I mean we need something we can picture or else its just maths. If there is some one out there who can explain what it is that people who really understand QM picture when they think of light, valid in all circumstances, not just in the classical limit of this, or the classical limit of that, then I will stand corrected on this point too. Thanks ;)

But I'm sure Hurkyl, or anyone else, would not want to write the whole book on QED on here! I certainly don't! It is silly to explain light in the intimate details of QED when the basic QM knowledge here is still shaky.

And I question the approach to QM using "conceptual understanding". There's nothing a priori to indicate everyone has the ability to have a "conceptual understanding" of QM, especially when most people are trying to forcebly impose CLASSICAL understanding into a realm in which such a thing may not be applicable. I find that highly illogical. I have already argued several times on why "QM is so difficult" to understand if one doesn't make any connection to the mathematics.

Zz.

 

[alfredblase]

so you are saying the Standard Model approach is to find some equations that fit the results, THEN try to work out the objects described by the maths. And then there is the further complication that the objects the maths, or even the maths alone may be too complicated for you.

Ok consider instead the way string theory is approached by a student of the subject. The idea of objects as open or closed strings, or membranes is presented. Then the idea of compact dimension is presented. All not too difficult to visualize. THEN you begin to tackle the maths of object actions, interactions and blah blah blah. I prefer that by a long way, don't you? And even though string theory may never be proven, who knows, I'd still be willing to risk spending four or five years undertaking a doctorate in that area rather than on the generaly accepted Standard Model, because I like the idea, the concept, its there its available to the begginer, to the general public even. That is important in physics. Its no use if only a select few can really concieve the objects, who knows maybe they don't and they just pretend to! hehe

 

[ZapperZ]

so you are saying the Standard Model approach is to find some equations that fit the results, THEN try to work out the objects described by the maths. And then there is the further complication that the objects the maths, or even the maths alone may be too complicated for you.
Ok consider instead the way string theory is approached by a student of the subject. The idea of objects as open or closed strings, or membranes is presented. Then the idea of compact dimension is presented. All not too difficult to visualize. THEN you begin to tackle the maths of object actions, interactions and blah blah blah. I prefer that by a long way, don't you? And even though string theory may never be proven, who knows, I'd still be willing to risk spending four or five years undertaking a doctorate in that area rather than on the generaly accepted Standard Model, because I like the idea, the concept, its there its available to the begginer, to the general public even. That is important in physics. Its no use if only a select few can really concieve the objects, who knows maybe they don't and they just pretend to! hehe

Please don't equate what I said with what is going in String Theory. I place a lot of emphasis on experimental observations, being an experimentalist. If you have been in the forum, you would have seen my objection and discomfort to that branch of physics.

If you wish, you may either read my take on this in my journal, or go to physicspost.com.

Zz.

 

[alfredblase]

Would it be right to say that a Quantum Mechanical object, be it light or any other, is a point particle, with a time dependant probablity distribution for its position, energy, interaction with other objects, and so on and so forth? If that's true it doesn't seem too hard to visualise...

 

[McQueen]

Please justify this description. How do you know this is the valid explanation for what you are describing?

The quote above referred to my statement that when we look out of a window on a sunny day , we see brilliant colours , and this is the result of the electrons in the objects ( flowers etc., ) that we see outside the window , rapidly absorbing and re-emitting photons of a given energy. This absorption and emission has to take place at a very rapid rate at least at around 10^^-18 secs for each absorption and emission.
The reference is one of your posts :
https://www.physicsforums.com/showthread.php?t=99218 [/URL]
[QUOTE=ZapperZ]“When light hits a metallic surface, the conduction electrons actualy ABSORBS the photons, causing a transition from one conduction band to another (there's a whole spiel here that I'm skipping about the transition is actually between two points between two different band separated by a reciprocal lattice vector). But this doesn't last and the conduction electrons will drop back to the original band and re-emit this photon,”
and “So if one prefers, the light being reflected is not the same light that was incident onto the mirror.” [/QUOTE]
So the question I really wanted answered was do these electrons [I] continuously [/I] absorb and emit photons at the frequency of the particular light they are being radiated with , as an example I had given green light at 550 nm and a frequency of 5.4 x 10 ^^ 14 Hz. The reason for my making this statement is that if we turn our attention away from the garden and to the window pane through which we are looking , we find that it takes about 10 ^^- 18 seconds for each absorption and emission to take place , based approx. on the number of atoms in the glass which the photon has to traverse , the speed of light through glass etc., Taking into consideration Fermat’s Law which states that light will take the shortest route through the glass , it seems likely that the same electrons are involved and are continuously absorbing and emitting photons at something like the rate of frequency of the light which they are transmitting. The thing is even if you stand looking out of the window for a couple of hours , the process doesn’t stop. Is it a [I] continuous [/i] emission and absorption process on the part of the electrons ? Or do individaul electrons absorb a photon , hang around for a while then re-mit it?

 

[ZapperZ]

The quote above referred to my statement that when we look out of a window on a sunny day , we see brilliant colours , and this is the result of the electrons in the objects ( flowers etc., ) that we see outside the window , rapidly absorbing and re-emitting photons of a given energy. This absorption and emission has to take place at a very rapid rate at least at around 10^^-18 secs for each absorption and emission.
The reference is one of your posts :
https://www.physicsforums.com/showthread.php?t=99218 [/URL]
So the question I really wanted answered was do these electrons [I] continuously [/I] absorb and emit photons at the frequency of the particular light they are being radiated with , as an example I had given green light at 550 nm and a frequency of 5.4 x 10 ^^ 14 Hz. The reason for my making this statement is that if we turn our attention away from the garden and to the window pane through which we are looking , we find that it takes about 10 ^^- 18 seconds for each absorption and emission to take place , based approx. on the number of atoms in the glass which the photon has to traverse , the speed of light through glass etc., Taking into consideration Fermat’s Law which states that light will take the shortest route through the glass , it seems likely that the same electrons are involved and are continuously absorbing and emitting photons at something like the rate of frequency of the light which they are transmitting. The thing is even if you stand looking out of the window for a couple of hours , the process doesn’t stop. Is it a [I] continuous [/i] emission and absorption process on the part of the electrons ? Or do individaul electrons absorb a photon , hang around for a while then re-mit it?[/QUOTE]

Read CAREFULLY what you quoted me, and what you are citing as an example. "Garden" and "window panes" have NO CONDUCTION ELECTRONS!

The optical properties of INSULATORS can be very different than the optical properties of METALS! Thus, when you go on and on with the electron transition and stuff but talking about colors reflecting off your garden, my question would be: you have metallic plants??!

Zz.

 

[alfredblase]

Would it be right to say that a Quantum Mechanical object, be it light or any other, is a point particle, with a time dependant probablity distribution for its position, energy, interaction with other objects, and so on and so forth? Yes or no would do please although more would be nicer. Thanks.

 

[McQueen]

you have metallic plants??!

Come on now ! With metals everything is reflected ( absorbed and re-emitted ,with other objects there is selective absorption and emission.

 

[ZapperZ]

Come on now ! With metals everything is reflected ( absorbed and re-emitted ,with other objects there is selective absorption and emission.

Yeah, but you were using my explanation of the mechanism in METALS, and using that inappropriately to describe the reason why we see colors in objects that aren't metals! Do you think this is kosher?

Again, as I've stated way earlier in this thread, it appears as if your primary source of info on physics is based on what you read on the web, and not anymore more formal than that. I would be very weary of such sources if I were you. Things like what you're doing here will occur often.

Zz.

 

[McQueen]

Again, as I've stated way earlier in this thread, it appears as if your primary source of info on physics is based on what you read on the web, and not anymore more formal than that. I would be very weary of such sources if I were you. Things like what you're doing here will occur often.

Can you make some time. If you leave me in the air it means , we wouldn't see colours or anything else. AND what's wrong with things on the web? Also I have some great Russian books , so don't dis me on that account. (P.S., not weary BUT wary)

 

[ZapperZ]

Can you make such time. If you leave me in the air it means , we wouldn't see coulours or anything else.

Say what? Are you still claiming that your hijack of my explanation for optical process in metals is valid when applied to insulators?

AND what's wrong with things on the web?

1. How would you know the stuff you read off the web is valid, or even correct? As much as I like and refer to Hyperphysics, I can STILL find things that I find misleading or incorrect.

2. They lack RIGOR and details

3. Physics isn't just "reading" off anything. You miss a lot simply by reading only. This is not a literature class. You could read till you're blind how to ride a bicycle, but unless you actually get on one, do it a few times, fall off it a few times, you will never be able to ride a bicycle. Physics is as much knowledge as it is a SKILL. Skills cannot be taught - it can only be ACQUIRED.

Zz.

 

[McQueen]

2. They lack RIGOR and details

I could give you a higly detailed summary of your spectroscopy experiments with multi- photon photoemission , unfortunately it didn't download properly , so I saved it as a word document. So I don't have the URL , still you see what I mean.

3. Physics isn't just "reading" off anything. You miss a lot simply by reading only. This is not a literature class. You could read till you're blind how to ride a bicycle, but unless you actually get on one, do it a few times, fall off it a few times, you will never be able to ride a bicycle. Physics is as much knowledge as it is a SKILL. Skills cannot be taught - it can only be ACQUIRED.

That's just it I have been thinking. and you still haven't answered my question , " metals reflect everything , coloured objects use selective absorption and emission. Or is this too big a subject to undertake? P.S. Anyone can ride a bicylcyle , even a chimp.

 

[ZapperZ]

I could give you a higly detailed summary of your spectroscopy experiments with multi- photon photoemission , unfortunately it didn't download properly , so I saved it as a word document. So I don't have the URL , still you see what I mean.

A "DETAILED SUMMARY"? What is THAT?

That's just it I have been thinking. and you still haven't answered my question , " metals reflect everything , coloured objects use selective absorption and emission. Or is this too big a subject to undertake?

What does this have anything to do with your explanation? You were using electron transition to explained everything by hijacking my explanation of optical processes in metals. I asked you to justify such a usage. You never did.

And oh, I would think twice before saying that metals reflect everything. Find out the plasma frequency of the conduction electrons and see what happens if I have light at a frequency GREATER than the plasma frequency. And while you're at it, if metals reflect everything, why does it become hot when left in the sun? Could it mean that, horrors, it actually absorbs the IR part of the spectrum? NO!

P.S. Anyone can ride a bicylcyle , even a chimp.

And even a chimp can spew back everything he was told but without understanding what they all mean.

Zz.

 

[McQueen]

And even a chimp can spew back everything he was told but without understanding what they all mean

I am sorry I apologise for the statement.

And oh, I would think twice before saying that metals reflect everything.

I was referring to visible light.

What does this have anything to do with your explanation? You were using electron transition to explained everything by hijacking my explanation of optical processes in metals. I asked you to justify such a usage. You never did.

What do you say about this then ?

etc.. are all techniques that were built using the photon picture, NEVER using "wave" picture of light.

 

[ZapperZ]

I was referring to visible light.

No, you were not. Besides, what is so special about visible light? It is, in fact, a VERY limited range of the EM spectrum. Our physics should NOT work only for that small range. If you are limiting your explanation to only this, then your explanation has serious fault, not that it hasn't already.

Please go back and read my objection here. You were using my explanation using conduction electrons in metals to explain the optical properties of NON METALS. I do not know how much more I can emphasize on how WRONG this is. YOu can't simply repeat what I said without understanding it, and then use it in the wrong situation.

What do you say about this then ?

And I'd ask you "What's wrong with that?" Open G.D. Mahan's "Many-Particle Physics" text and see why optical conductivity experiments CAN and DOES use QM's description of light as the foundation for all such experiments.

This has become a convoluted thread. It seems that every explanation I gave, I have to double-back and have to explain the explanation, and then have to explain that too! Whenever things like this happen, it is usually a symptom that some very fundamental understanding is lacking. While I don't mind going one or two layers deep in trying to explain things, you will understand that at some point, this gets very tiring and exasperating. I can no longer assume that you know such-and-such to be able to comprehend my explanation, and certainly not after you misrepresented my explanations. This thread has taken way too much of my time with no apparent benefit or progress.

So stick a fork in me, because I'm done. Someone else who probably have more patience and can explain things a lot better may want to take over.

Zz.

 

[McQueen]

This has become a convoluted thread. It seems that every explanation I gave, I have to double-back and have to explain the explanation, and then have to explain that too! Whenever things like this happen, it is usually a symptom that some very fundamental understanding is lacking. While I don't mind going one or two layers deep in trying to explain things, you will understand that at some point, this gets very tiring and exasperating. I can no longer assume that you know such-and-such to be able to comprehend my explanation, and certainly not after you misrepresented my explanations. This thread has taken way too much of my time with no apparent benefit or progress.

I'm sorry ! You know I expected something like this to happen , because your work is very detailed and requires your total attention.I appreciate both what you are doing and your level of competence. I'm sorry for distracting you. I just wanted to know how ordinary objects reflect light . How we see things. You have been very patient and I appreciate that.