Fra said:
Hello Peter, I think I skimmed some of your random field paper long time ago, but doesn't remember the points (I probably need to read it again), I remember that the last time I asked for the "physics of the indexing process".
Yes, I posted in January, just after a paper was accepted by J. Math. Phys. It's
https://www.physicsforums.com/showthread.php?t=204567".
I think I didn't answer your query about the index set back then. I think it's problematic, but I'll give it a try again now. The usual index function is a pure frequency. Thus, when we say in quantum optics that waves of a particular frequency are being measured, that's what the equipment is sensitive to, so we use creation and annihilation operators associated with pure frequency index functions, perhaps exp(-i\omega t+ikx). This is problematic in QFT: mathematically, because it has infinite norm, because it's spread over all space-time; operationally, because the experimental apparatus doesn't really resonate with a signal over all of space-time. The experimental apparatus does resonate with the signal over some of space-time, at least where the measurement device is placed, so the appropriate index function is one that is centered on a given frequency in Fourier space-time and centered on a given place in real space-time. Test functions that represent a measurement device well, in great detail, have to be established by characterizing the device with standard sources of various kinds (of course it's a succession of approximations, standard sources become standard by being measured with standard measurements, which became standard by ...).
Fra said:
1) a somewhat unclear benefit in adopting the supposed solution (random fields) of the question posed. I would want a stronger motivation to read the paper more carefully. Ie. Why is the desired to have some kind of "classical style model" (fields or particles) such an important question?
To me this is not very clear, thereby does my motivation to analyze a supposed solution to that drop.
I am not saying there are no issues with QM, I am just thinking that perhaps this original concern of loss of classical logic and old style realism isn't the main problem? Or if it is, perhaps your paper should try to explain why, as to increase the motivation to study your solution.
I'm not a modernist Physicist. I'm post-positivist. Classical Physics is not a better conceptual system than quantum Physics. They are different. There is a straightforward Occam's razor reason for preferring to use classical models throughout, instead of using classical models at macroscopic scales and quantum models at small scales when necessary,
IF we can do so without introducing even greater complexities. All existing classical models either appear ad-hoc or introduce non-locality in some way that Physicists, on balance, think unacceptable.
I think continuous random fields might be acceptable to Physicists. The history of Physics is strewn with people who've failed to convince anyone of a myriad of similar claims, of course.
Additionally, since quantum theory cannot give a detailed account for Physical processes without introducing quantum
fields, but there is, so far, no mathematically valid
interacting quantum field in Minkowski space, and the mathematical procedures and our conceptual understanding of both perturbative and non-perturbative QFT are somewhat problematic, the fact that there are mathematically elementary models for continuous random fields is
enough to justify more attention. It may be that people will decide against this approach, but I believe it now justifies more attention that just from me.
Fra said:
2) I think one may need to read up on your other papers to appreciate this paper more.
You surely have better things to do.
Fra said:
Other than that, I tried to think about this and there might be elements that I like. I also think the general trait of contextuality is plausible. But my personal view of contextuality is the evolutionary one that the logic of interactions are best understood conditional to the evolved present (which is dependent on the past).
I think I can agree with your sentiment about contextuality, or at least my reading of it makes sense to me, but how are you going to represent that web of multiple interactions? Also, does the past superdetermine the present? Perhaps deterministically or perhaps only probabilistically (the latter is enough that Bell inequalities cannot be derived, for a random field)? How will you represent, mathematically, the exact, detailed ways in which your physical model of dependencies is not deterministic, or does not determine evolving probabilities?
If you stay with quantum theory, you are essentially staying with an effective way to talk about the contextuality of measurements, in which measurements change the possibility of carrying out other experiments. Alternatively, in a classical approach, measurements can change the system that is measured, changing the context in which the other measurement is made. The irony is, perhaps, that before the EPR paper Bohr and Heisenberg both talked about quantum mechanics in terms of measurements changing the system that was measured, a position they dropped when they realized that it required nonlocality for particle properties. For continuous random field models, holism is required, but not nonlocality.
Fra said:
Also general idea of indexing observables is something I feel needs a physical explanation. Ie. from the point of view of "black box physics", how is the index on which the field is defined emergent?
I guess one of the classical logic things is that these things "just are", but from the point of view of information process that I find more plausible than the ontologies of classical physics, I see these as emergent. Isn't the index structure itself an ontology? How do you "measure" the index? or don't you?
I tried to answer this above, but I'll try again. The world is what it is. We are in it. We construct various experiments, frequently reusing parts from other experiments, attempting to construct parts that we understand well so that we can extend our understanding and control incrementally. To do so, we try one mathematical system or another, which have various degrees of freedom that we try to fix with the experimental results. Our measurements of the lengths, geometry, and approximate symmetries of an apparatus are part of those experimental results. Quantum theory, on this view, is not a linear theory, because we know neither what the state is not what the measurement is Tr[\rho_i,\M_j]=R_{ij} is bilinear in the unknowns, constrained by the experimental results R_{ij}. To solve this bilinear system, we guess what measurements we've constructed, then iterate. There are all sorts of subtleties, since we have only a finite number of finite accuracy data points, but we presume to fix a state in an infinite-dimensional space of density operators, but we work to obtain a system that is conceptually pleasing, self-consistent, and practical for engineering purposes --- hence we obtain quantum optics, for example.
Fra said:
From my perspective I don't clearly see from that two page paper what fundamental problem you are addressing. To me the loss of some "classical features" is not a fundamental problem, because the classical logic wasn't satisfactory to start with.
I agree, certainly, that classical logic, mechanics, continuous random fields, etc., are not
satisfactory. But that doesn't mean we can't use them from time to time. There are conceptual problems with quantum mechanics, too, but I will certainly continue using them.
This two page paper was my current attempt to reiterate the argument that I made in my published papers at a more accessible level. I don't think I succeeded very well, but, for what it's worth, I put a lot of work into it. I've valued comments made at PF on my earlier papers; here I am again, doing pretty well again. Most obviously, you've led me to mention Occam's razor in a way that I think I like and might possibly use again.
Thanks, Fredrik! Best wishes.