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Quantum Field as Physical Entity?

  1. Feb 2, 2012 #1
    Hello experts (or even the not so experts) in QFT. Have you encountered before the following stuff on QFT?

    http://www.scribd.com/doc/58635278/Introduction-to-a-Realistic-Quantum-Physics

    The following is an example of what it's saying:

    The basic idea is that:

    Please find critical flaws in the idea and let me know what it is. Thanks.

    If there is no flaws. Why didn't the scientific community encompass it?
     
  2. jcsd
  3. Feb 2, 2012 #2

    mysearch

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    Hi,
    You originally raised your question in the following thread: What are the Fields in QFT? However, I think you are right to raise the issue in its own stand-alone thread. This said, I did take a look at the essay, as requested, so felt that I might as well add an initial post to your discussion, which is more an expression of interest than any deeper insight.

    By way of a few general comments, which other members may wish to cross reference. I have only quickly scanned the Giuliano Preparata essay and his background qualifications – see http://en.wikipedia.org/wiki/Giuliano_Preparata. As such, he appears, unlike me, to be qualified to make his own interpretation of both QM and QFT, although this doesn’t necessarily make him right. The passage you quote from this essay is taken from Chapter-4 (p.39). I haven’t had a chance to look all the mathematical arguments forwarded in this chapter and I doubt that I would understand all the details at this stage of my own learning curve. However, there are clearly people in this forum who are qualified to comment. Purely as further examples of the main conclusion being forwarded in this essay, i.e. there exists only one consistent type of physical object: the quantum field.

    End of Chpater-4, p62
    “…in QFT the quantum particles have no independent physical reality, nor a well defined physical localization, they just correspond to the peculiarity of the localized quantum measurement, that can only reveal the presence of the quantum field in a "quantized" way, i.e. through their quanta. Thus in QFT the "elements of reality" only belong to the quantum field, which is neither localized nor separable”

    Chapter-5: p.63
    “I may easily imagine the "normal" scientist of our times sneering at this latter statement: Big deal! What have we gained? A prediction of new phenomena? A new set of computational rules? Only a different interpretation of the physical meaning of the mathematical symbols of the quantum mechanical formulae, which does not take us an inch ahead in our long journey through energy and matter. For such is the attitude of the positivists, who completely dominate modern science, generally uninterested in questions of principle, philosophy in short, and keenly concentrating on the "practical "aspects of their activity, whose range is, however, rigorously constrained by a rigid "paradigm", that stands, without their knowing, on a pedestal of philosophy, including Copenhagen's brand of conventionalism”

    So, like you, I would be interested in understanding whether there is any support for this view by those really qualified to comment. Thanks for the link to this article.
     
    Last edited: Feb 2, 2012
  4. Feb 3, 2012 #3
    I think one problem with treating the quantum field as a physical field is upon collapsed in the detector in say the double slit experiment, the entire field seems to be in coordination or communicating superluminally within. Preparata said in EPR, one must not look the particles as having any element of reality because particles don't really exist.. only the field has element of reality. But to explain entanglement, the physical field has to be non-local. But then would it violate relativity if no information can be conveyed to us by these non-local physical quantum field? Remember phase velocity of a particle is faster than light compared to the pilot velocity and this doesn't violate relativity. It seems relativity doesn't forbid faster than light if causality is not affected and no paradox can occur. Therefore if the quantum field internal aspect is superluminal yet it doesn't convey information to us or we can't use it to transfer information faster than light. Then relativity is not violated? Can anyone give example of how a non-local physical quantum field can be used to transfer information faster than light. If such an example can be made. Then maybe the idea is not viable.
     
  5. Feb 3, 2012 #4

    mysearch

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    Hi,
    I hope the following comments are not too off-topic for this thread, but appeared to me to be linked with the general issue of physicality of objects in both the original QM, i.e. NRQM, and its transition towards QFT. You make reference to ‘pilot velocity’ and then a ‘phase velocity’ being greater than [c], which I would like to clarify, as I am still not sure of the implications. First, I am assuming that your reference to pilot velocity is linked to deBroglie’s definition of matter waves:
    [tex]E=mc^2=hf=\frac {hv}{\lambda} \rightarrow
    \lambda=\frac {hc}{mc^2}=\frac {h}{p}[/tex]
    However, deBroglie’s wavelength for a particle appears to rest on the assumption that the relationship [h/p] can be extended from a particle-like photon to a wave-like particle, if we make the following assumption about the definition of momentum [p]
    [tex]\lambda=\frac {hv}{mc^2}= \frac {h}{p} only \ if \ p= m \frac {c^2}{v}[/tex]
    As such, we have what I think you are referring to as the pilot (group) velocity [vg<c] and the phase velocity [vp>c]. In terms of trying to describe a matter wave packet being finite in space, the wave packet might ‘conceptually’ be described in terms of a superposition of waves, which then raises the issue of matter wave dispersion. This idea can be cross referenced to the Wikipedia link ‘De Broglie dispersion relations’ where the relationship is linked to kinetic energy, not total energy:
    [tex]E= \frac {p^2}{2m}[/tex]
    [tex]\omega = \frac {\hbar \kappa^2}{2m}[/tex]
    [tex]v_p = \frac {\omega}{\kappa} = \frac {\hbar \kappa}{2m}[/tex]
    The implication of the equations above appears to suggest that the superposition waves required to construct a finite matter wave packet must all travel are different phase velocities and therefore disperse. If you can cross reference Example 6.4 in this reference, you will find the derivation of the following equation:
    [tex]\Delta x(t) = \sqrt{ \left[ \Delta x(0) \right]^2 + \left[ \frac{\hbar t}{2m \Delta x(0)} \right]^2 }[/tex]
    As far as I can see, this equation is linked to dispersion equation above rooted in deBroglie’s hypothesis. However, the suggestion of the equation above appears to be that the electron wave packet will disperse by a factor of 10 after a time 10^-15 sec. This seems to raise that question as to where the electron wave packet exists prior to its collapse and whether this construct has any physicality or is just another mathematical construct of quantum theory. Would be interested in any clarifications, if this is relevant to this thread and the subsequent development of QFT, otherwise simply ignore. Thanks
     
  6. Feb 3, 2012 #5
    As mentioned by Fredick, our QFT is in crisis. They use Fock space that doesn't really interact in the fundamental level. So how could they solve for quantum gravity and solve for room temperature superconductivity if they didn't even use the right tool.

    Right now. There are thousands of papers in Arxiv that deals with perfecting QFT. So those serious physicists would rather spend time with them rather than Preparata stuff. This may be the reason why his work is just ignored because for those physicists who know rigorous QFT, they would spend time with other papers. For those who know only non-rigorous QFT which comprise maybe the bunch of physicists with Ph.D. They don't have training to even analyze the far end of QFT. Therefore this is why I guess Preparata stuff is ignored especially since he died prematurely... but what if he were right that the key to the secret of room temperature superconducitivity is an alternative way to look at QFT. Then most would miss it. See his second book "QED Coherence in Matter" for the details of room temperature superconductivity using enhanced QFT.

    Hope at least one physicist would seriously review Preparata work. It's the opposite of demystifier theory which deals purely with particles. Preparata's is the opposite which deals solely with fields. For now. I consider demystifier theory as nonviable because to make it all possible. Free will doesn't have to exist and everything from past to future is already written in stone.. which you know is a ridiculous idea (hereby demystifier theory is refuted).
     
  7. Feb 6, 2012 #6

    Demystifier

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    I am not against presenting rational arguments against my theory, and I am sure such arguments can be found (as can be against any other theory), but statement that it is "ridiculous" is not an argument at all. Still, I can understand why do you find it ridiculous, and you are not alone, and for such people I have written this:
    http://fqxi.org/data/essay-contest-files/Nikolic_FQXi_time.pdf
     
  8. Feb 6, 2012 #7

    mysearch

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    Demystifier, thanks for the reference to your paper, I think I read it some ‘time’ ago and have only quickly scan the paper again before posting the comments below, which I might regret on closer reading. However, I was wondering whether there was ever a discussion thread of your paper in the PF, which might be a more appropriate way to raise some further questions, if they have not already been discussed. While not wishing to divert the direction of this thread, I am assuming the issue of free-will raised may stem from statements concerning the description of relativistic time as follows:
    “Instead, relativity suggests a picture of the block time, where time is nothing but one of the coordinates on the static 4-dimensional manifold. All we know about relativity is perfectly consistent with such a picture. According to this picture, the universe does not evolve with time. Instead, the universe simply is, extended in 4 dimensions, one of them being called “time”. Both the “future” and the “past”, as well as the “presence”, are there, without any of them being less certain or less real then the other.”​

    From a human perspective, there seems to be a suggestion that the causality of some decision taken ‘now’ already exists in the future(s), but I think this is a misrepresentation of your actual arguments, as I really need to read the paper more carefully and consider the issue of light-cones. This said, is the description of a quantum matter wave, when described as a function of time/frequency affected by your description? However, as indicated, such issues appear off-topic to this thread. Thanks
     
  9. Feb 6, 2012 #8

    Demystifier

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    The block-time interpretation of spacetime has manifestations on the interpretation of quantum wave function. Instead of being interpreted as a probability density in 3-dimensional space, it is reinterpreted as a probability density in 4-dimensional spacetime. For more details see e.g.
    http://xxx.lanl.gov/abs/0811.1905 [Int. J. Quantum Inf. 7 (2009) 595-602]

    And it is not off-topic at all, because such an interpretation of the wave function can be generalized to quantum field theory
    http://xxx.lanl.gov/abs/0904.2287 [Int. J. Mod. Phys. A25:1477-1505, 2010]
    suggesting that quantum field may not be a physical entity per se.
     
  10. Feb 6, 2012 #9
    For me, free will is 'restored' by realising that we cannot know what our future is anymore than Quantum Mechanics can realistically be used to predict the outcome of a horse race. There is effectively no real difference between a predetermined future we can't calculate with any precision and a non-predetermined future. This is currently the crux of my own interpretation of Quantum Mechanics.

    Although I often think along the lines you discuss - block time, two different types of time (you might want to come up with a better word than 'pime' - it's right up there with 'charm quarks'), these are not the only musings I consider. Other thoughts recognise that space is still growing and time with it, and that it may not be possible to consider either in 'block' form. All of space can only be considered once there is an 'all of time' - and both are still passing. Space is, in a symmantic way, 'lapsing'.
     
  11. Feb 7, 2012 #10

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    Demystifier, I won’t pretend that I understand all the content of the following papers, but you have sure given me a lot to think about. If possible, I would like to raise some questions in connection with trying to extend my own understanding, especially in the context of this thread regarding the ‘physicality’ of some of the foundation concepts of QM/QFT. In wider context, I have got the impression that while some people have in-depth understanding of the maths, the physical interpretation stemming from the mathematical description still seems open to much debate. See the following threads as possible examples: ‘QFT vs QM 101’ and ‘What are the Fields in QFT?
    I would like to add one additional reference in order to ask whether this paper cuts across similar ground as any of the papers above?
    From my own perspective, the papers above have highlighted a number of issues that I would like to understand better and see, if possible, whether they can still be anchored in physical concepts.
    • Relative and physical time
    • DeBroglie Pilot and Matter Waves
    • Quantum Operators
    • Klein-Gordon Equation
    • Bohmian interpretation
    Relative and physical time:
    While having an understanding of the benefits of Minkowski spacetime, it is not clear to me that time can be said to have no flow or direction. The second law of thermodynamics seems to suggest that there is more than low-probability preventing a broken cup spontaneously re-assembling. However, I still need to give the paper cited a lot more thought.

    DeBroglie Pilot and Matter Waves
    I outlined some issues in post #4 regarding the logic of extending Compton’s rationale of a particle-like wave to deBroglie’s wave-like particle. For it seems you are led to the idea of superluminal phase velocity [c2/v] and the notion of dispersion of the superposition waves required to create a matter wave packet that is localised in space. The physicality of the superposition waves seems ambiguous, to say the least, and also leads to questions about the location of a particle, like a free electron prior to the wave function collapse, which itself a subject of almost endless debate.

    Quantum Operators
    From a historical context, there seems to be 2 key ideas underpinning quantization. First, Planck described a quantization of energy [E=hf] needed to explain blackbody radiation, although the idea seems to be more rooted in the ‘equi-partition’ of the energy spectrum. Einstein’s paper on the photoelectric effect also seems to point towards a quantization of energy in the form of a photon [E=hf]. Later, Bohr started to explain atomic orbits in terms of the quantization of angular momentum. Today, the physicality of these concepts seems to be reduced to 2 mathematical operators, where the second is reduced to a 1-dimensional simplification:
    [tex]E=i \hbar \frac {\partial}{\partial t}[/tex]
    [tex]p=i \hbar \frac {\partial}{\partial x}[/tex]
    Defining Planck’s constant [h] in terms of joule.sec, the operators themselves reflect the units of energy [E] and momentum [p]. Therefore, I am assuming that any object they are applied to cannot have any unit dimensions, which is the case for the following plane wave description:
    [tex]\psi = e^{i \left( \frac {2 \pi}{ \lambda}x – 2 \pi ft \right) } = e^{i \left( \kappa x - \omega t \right) } = e^{ \frac {i}{\hbar} \left(px - Et \right) } [/tex]
    I have presented the wave equation in this form because it seems to illustrate that the concept of energy [E] and momentum [p] can be linked to a wave or perturbation of a field without any implicit reference to a rest mass, as in the case of a photon. Returning to the issue of quantized operators, the energy operator above appears to reflect a dependency on time [t], possibly linked to frequency [f=1/t] in order that the units of [h] are normalised to energy. By a similar argument, the momentum operator seems to transform the quantized energy.sec represented by [h] to momentum. While I have tried to rationalise the idea quantisation of the energy and momentum operators, I believe QM also defines position [x] as an operator, while QFT treats position, and time, as parameters. Is there any implication in QM that position is indirectly quantized by implication to Heisenberg’s uncertainty principle?

    Klein-Gordon Equation
    The reason for speculating as to the physicality of the quantized operator is linked to the definition and use of the Klein-Gordon equation in several of the paper cited above. This equation is often described as a relativistic version of Schrodinger’s wave equation, although the following somewhat non-standard derivation suggests that it is almost entirely rooted in the relativistic energy equation, where [m] corresponds to the rest mass:
    [tex]E^2 = p^2c^2 + m^2c^4[/tex]
    [tex]E^2 - \left(p^2c^2 + m^2c^4 \right) = 0[/tex]
    If we simply substitute for the quantized operators of Energy [E] and momentum [p], as defined above we get:
    [tex]\left( i \hbar \frac {\partial}{\partial t} \right)^2 - \left( \left(i \hbar \frac {\partial}{\partial x} \right)^2c^2 + m^2c^4 \right) = 0[/tex]
    However, we need to apply the operator to a suitable object, possibly the plane wave function above and if we reverse the sign on the square of we get:
    [tex] \hbar^2 \frac {\partial^2 \psi}{\partial t^2} - \hbar^2 \frac {\partial^2 \psi}{\partial x^2}c^2 + m^2c^4 \psi = 0[/tex]
    [tex] \frac {\partial^2 \psi}{\partial t^2} -\frac {\partial^2 \psi}{\partial x^2}c^2 + \frac {m^2c^4}{\hbar^2} \psi = 0[/tex]
    As such, we appear to have arrive at the basic form of the Klein-Gordon equation that is said to represent the equation of motion of a scalar field, where a quanta of this field might be said to correspond to a spinless particle of rest mass [m]. As such, this equation that appears to be rooted primarily in a definition of relativistic energy, i.e. RQM, also appears to have some scope in QFT. However, do we need to question the ‘physicality’ of the concept of mass [m] at the most fundamental quantum level in terms of energy as well?

    Bohmian interpretation
    Many of the papers give reference to the Bohmiam interpretation as a preferred interpretation. Again, I am not really in a position to question this interpretation, so will only raise one general question at this stage. Looking at Demystifier’s public profile, he is a theoretical physicist by profession and presumably has the mathematical background to look at the details of quantum theory in greater depth than most. However, he seems to support an interpretation that many other professional theoretical physicists reject, while presumably looking at the same information. Why? Is it possible that the verification of quantum theory is simply so vague that many alternative interpretation are possible and will remain possible, until some sort of tangible/physical/real description of the processes at work is made, rather than the apparent evidence of a probability outcome?

    Again, for the record, my comments are not meant as assertions, simply questions and apologises for an overly long post, but I wanted to log my initial thoughts and issues for my own cross reference with the hope that some clarifications might be on offer. Thanks
     
    Last edited: Feb 7, 2012
  12. Feb 7, 2012 #11
    I have read all of Demystifer papers. What I can say is that by trying to prevent Preferred Foliations in Bohmian Mechanics, he has to do away with Free Will where the future is already written. This is a high price to pay. I don't like this. I'd rather have theories where Preferred Foliations existing than Free Will disappeared... which supports Occam's Razor too. Therefore if anyone know of a relativistic Bohmian Mechanics with Preferred Foliations, please let me know. Is there such and is it impossible? How come?
     
  13. Feb 8, 2012 #12

    Demystifier

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    I have some good news and some bed news for you.

    The good news is the fact that there are versions of relativistic Bohmian mechanics with preferred foliation, including some of my own such as
    http://xxx.lanl.gov/abs/0804.4564 [Found.Phys.38:869-881,2008]

    The bed news is the fact that it cannot save free will, simply because the theory is deterministic. In fact, all known fundamental theories in physics are either deterministic or probabilistic. Neither deterministic nor probabilistic theories can incorporate free will, as long as they are fundamental in the sense that everything, including the human brain, obeys their laws.

    Still, the good news is that it does not imply that all physical theories are ridiculous. They all can incorporate the idea that free will exists as an ILLUSION, which is sufficient to explain the fact that humans do perceive the existence of free will. That includes Bohmian mechanics without preferred foliation.

    If illusion of free will is not enough for you, then the only alternative that remains is the idea that neither of the known physical theories is fundamental, i.e., that something (e.g., some processes in the brain) does not obey these theories. This can be applied to Bohmian mechanics without preferred foliation as well, so in effect, your legitimate desire to save free will is not an argument against Bohmian mechanics without preferred foliation.
     
  14. Feb 8, 2012 #13
    I'm talking of the Special Relativity thing where any superluminal velocity would always have one frame that sees it backward in time.. if lorentz invariance hold. The only way out of this is preferred foliations. This won't produce any backward in time scenerio and removal of free will to preserve causality. This is the strong sense.

    But you mentioned that in spite of these. Bohmian or Copenhagen's deterministic and probabilistic nature is fundamental and the brain has to obey them and free will is still not there. This is the weaker sense compared to that of the first paragraph. However, Qualia can not be modelled or simulated in any computer. So maybe we have to assume Qualia is based on a physics where intrinsic randomness create it. If not, then perhaps free will is an illusion.
     
  15. Feb 8, 2012 #14


    I think science will be considered finished when we can model qualia and the human mind in a computer. This will prove everything is just matter, energy and spacetime and nothing else. This will be hundreds of years into the future. By which time, Higgs is well defined, quantum gravity is discovered, dark matter and energy is totally understood. If by then we still can't distinguish quantum interpretations, then there would be no hope of it.

    Maybe you can put up a blog site and write them as you know more about QFT and what makes it ticks.
     
  16. Feb 8, 2012 #15
    But thinking of it more. Note that in a computer random number generator. The output is truly random. You can never write a program that can predict the random nature of the output. And this is a classical computer where the randomness didn't come from quantum randomness. Therefore we can treat daily life decisions and events as like from a random number generator in a classical computer. This means our the interaction of our will is enough to totally randomize everything even classical. This proves free will exist.

    In your paper Demystifer. You focus on total lorentz invariance in Bohmian Mechanics without preferred foliations, the consequence is that the future already exists and it's just coming to meet us. But the computer random generator thing above alone disputes that. Hence why not focus on BM that has preferred foliations instead of saying even a computer random generator is predictable which we know is not.
     
  17. Feb 8, 2012 #16
    A random computer is predictable. In easy terms, a random number is a number which was chosen from a table through an algorythm that the user don´t know, but the developer of that software do know and can predict with total precision. The fact that the user don't know the algorithm and the structure of the algorithm give the user the illusion that the number was chosen randomly.
     
  18. Feb 8, 2012 #17
    Really? Can you give another example where events can be truly random? There is this concept called Chaos where if a butterfly flaps her wings, it can affect the pattern of hurricanes later (The Butterfly Effect). This may produce randomness. Or are you saying if the world were deterministic. A butterfly who flaps her wings in the days of the dinonaur can have the effects tracked even to the present and billions of butterflies effect can be tracked and the present and future predicted like in 70,000 A.D. on July 14 we can know what will be located in a certain position on earth and everything tracked? Does anyone know how to dispute this?
     
  19. Feb 8, 2012 #18

    Demystifier

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    That is true.

    I don't understand why do you think that a way out of it is even needed. In other words, what's the problem with the fact that some trajectory looks like going backwards in time?
     
  20. Feb 8, 2012 #19

    Demystifier

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    I don't think that it does, because the computer random generator is not really random, but only pseudo-random. In other words, the numbers are generated by a deterministic mechanism, which for all practical purposes does not appear deterministic because not all initial conditions can in practice be controlled.
     
  21. Feb 8, 2012 #20
    The problem is you can meet your earlier self say 2 hours before now. But if no free will.. then they are consistent because even if you meet your other self. Your other self is destined to meet your future self, and no causality violation because it forms a loop. This is what you are reasoning and suggesting. But if there is preferred foliation. Then no paradox about going back in time. This is more elegant. Think about it. Why not focus more on relativistic Bohmian Mechanics version with preferred foliations. This is more believable and plausible than believing that we already know what will happen in 1 Billion A.D. at Sept 3 at 11pm in a certain location in New York. Come on. You are even more fantastic than Nostradamus. Lol...
     
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