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a reply to: BO XIAN
This gets into the semantics of exactly what you mean by "communicate". We see chemical and electrochemical forms of communication between cells in living organisms to coordinate the efforts of the cells to keep the organism alive.
If you mean outside living organisms, like two individual hydrogen atoms, I would explain the process by which they form an H2 molecule as an "interaction". However if I was explaining this process to my young nephew I might inaccurately describe their interaction as a form of communication to simplify it for him, fully realizing that it's not really what I would normally consider "communication". So I guess it depends on what you mean by "communicate". We say particles interact, but when physicists say two like charges repel and unlike charges attract, the vocabulary is more one of interaction and not so much "communication" though if you define "communication" broadly enough I suppose it could overlap with interaction somehow.
Your fellow physicists might be guilty of some things like groupthink sometimes, but I think they know better than to make experimental conclusions using circular reasoning along these lines.
Because of course, if we have one free parameter to set for every truly unique experiment, we will always get 100% agreement between theory and experiment.
At some exponentially high energy scale - that you may morally visualize as "exp(137.036) times electron mass", although there are extra coefficients everywhere - QED breaks down, anyway. It has a Landau pole: the fine-structure constant diverges if extrapolated to the huge energy scale. The same occurs with theories with quartic self-couplings of scalar fields etc.
In practice (I mean practician's practice), this Landau pole is not a real problem because the scale "exp(137.036) times electron mass" is much higher than the Planck scale, so obviously many things such as quantum gravity (and even much more mundane phenomena such as the electroweak unification) will modify QED long before you get to the Landau pole. But from a theoretical viewpoint, not thinking about the extra modifications of physics that exist in the real world, the Landau pole is a problem, too.
I've also seen others like Steven Weinberg discuss using a Lattice version of QED as an approach to the Landau Pole issue, among others, as discussed here:
We investigate a lattice version of QED by numerical simulations. For the renormalized charge and mass we find results which are consistent with the renormalized charge vanishing in the continuum limit. A detailed study of the relation between bare and renormalized quantities reveals that the Landau pole lies in a region of parameter space which is made inaccessible by spontaneous chiral symmetry breaking.
That topic is discussed on pages 13-16 if you want to skip the first 12 pages which are interesting but maybe not so relevant. He's obviously given the subject a lot of thought.
....I describe for non-specialists the current status of the problem, and present my personal view on how it may be resolved in the future.
originally posted by: delbertlarson
Here is the question: how experimentally accurate, really, is QED?
Background: After Physical Review Letters rejected my latest work, saying I needed field quantization, I ordered Julian Schwinger's book. In reading the forward, I remembered why I didn't dig deep into the topic before. I did take, and fully pass, my grad school courses on it, but there was always THE CENTRAL PROBLEM - which is that renormalization never made any sense at all, it fact it appeared as a blatant fudge. And then in the forward, Schwinger emphasized toward the end what an unsatisfactory thing it is. Feynmann made similar totally disparaging comments. I don't know of any of the originators that ever really supported it wholeheartedly. Since it appeared to be totally based on a fraud, I didn't dive too deep into it.
But there is the issue of how extremely well it is advertised to match experiments, and this is a big, big deal. If it really does match experiments as well as is claimed, then one has to perhaps revisit the issue of how this can be. Perhaps renormalization, as flaky as it looks, has some sort of solid underpinning that just hasn't been found. (Or perhaps it has been found, and you can enlighten me.)
Yet there is also the possibility, I believe, that perhaps QED isn't nearly as good as it is claimed to be. What I recall renormalization doing is that it requires that certain parameters - mass, charge - be set experimentally. Now these parameters are not the same ones that are observed in the "far field", because (for example, in the case of charge) as one gets closer to the center things like electron positron pair creation occur, and there can be some sort of screening that takes place. So you then get a far field charge and a bare charge, and they are different. The far field charge is set by classical tests. And the bare charge gets assigned as the result of different experimental tests, and then renormalization wraps it all up so that things all agree. That is how I've understood it - is that basically correct?
And so the issue is this - if renormalization theory allows for a determination of the bare quantities from experiment, are there enough independent high resolution experiments so that we really do have high accuracy? Or, say, does the Lamb shift allow us to set the bare charge, and the electron g-2 allow us to set the bare mass of the electron, and the muon g-2 allow us to set the bare mass of the muon?
And then there are the running coupling constants. Are they allowed to let the renormalization just run to another value whenever needed?
Because of course, if we have one free parameter to set for every truly unique experiment, we will always get 100% agreement between theory and experiment. So my question (again) is how experimentally accurate, really, is QED?
I am just starting to look into all of this again, so I'd appreciate any enlightenment.
If you're asserting they really had a circular assumption in their calculations I'd be interested in seeing the details of that, but from your vague description it's hard to confirm if that's the case. Maybe they didn't do what you expected them to do but they did what they intended to do. Some experiments test relativity and some don't. If the experiment is testing relativity it should pre-calculate the expected results if relativity is right and what results to expect if some other model is correct instead, or if relativity is wrong. On the other hand, if the experiment isn't testing relativity, it's not unreasonable to make assumptions that relativity is correct based on other experimental results. As long as those assumptions are clearly stated I don't see it as circular or flawed science, even if relativity turns out to be wrong which it probably is in some broader case like Newton's model turned out to be wrong in the broader case.
originally posted by: delbertlarson
It turned out that they had assumed the usual special relativity relations to derive the angles rather than measuring them. So it was at that time that I really began to question how many circular arguments might be around right now.
That's quite an ordeal, but I guess politics isn't just in politics, it's rampant in corporations, and per to your experience, also in laboratories. Lead scientist Dr Rind had it worse than you though, when US House of Representatives passed a resolution in 1999 that his team's science was wrong even though they apparently knew next to nothing about his science, since one representative who did know something about the science pointed out that almost nobody who voted on it even read the paper, and of the handful who did read the paper, most were unqualified to evaluate the science. So politics is even worse in politics but even outside of government it rears its ugly head.
So the way things work right now is really not much further along that when it was with Galileo from the point of view of accepting new ideas. At least we no longer use the rack. We just make it very hard for people with different ideas to find work "in science".
As I said I can't vouch for what he says being accurate but as far as I can tell his viewpoints that the existing QED and QCD models are somewhat useful even with their flaws seems to be shared by many. I'm sure he won't argue that QCD can calculate masses, so perhaps you and he have different ideas on what's expected from the current working models. I also read the article a little differently than you as your reading seems to infer a lack of problems, but as I said if you ignore the title it does describe problems with the models, then puts those into perspective. If you're trying to model the big bang I think the problems are currently unsurmountable, but that's a rather unique application at extremely high energies and the problems with the models at those energies don't apply to all energies which is how they can be useful even if they are "wrong" in the sense of not working at big bang energies.
originally posted by: delbertlarson
a reply to: Arbitrageur
I read through the article motls.blogspot.com... I remain totally unconvinced. ... Especially the arrogant assertion that QCD is on track. The bottom line there is that if QCD was on track it could calculate the meson masses with at least some degree of accuracy. Instead its just a mess. Again, I just don't buy it.
Steven Weinberg referred to it as one of the *potential* solutions, not a present solution. It does provide more useful results with large coupling than with small coupling but the hope is we can find better mathematical approaches to using it than we currently have.
On arxiv.org... I got lost on the Chiral symmetry breaking. However, they did mention the thing I thought of on my own, which was that putting things on a lattice just means that you are localizing the problem to the smallest lattice step. And as that step goes to zero you have issues computationally, since now any finite volume of analysis will require infinite steps. So I really don't see the hope in this approach either.
originally posted by: KrzYma
BTW.. you know nothing about me and the EM theory
originally posted by: delbertlarson
a reply to: joelr
Thanks joelr for joining the discussion. Perhaps you can further enlighten me on some of the thinking behind QED.
If we have a point-like electron with charge e, it will have an infinite, positive, self energy from that charge by the classical arguments. If we now let e run to infinity that would naively appear (at least to me) that we have infinity squared, not a cancellation. How does QED refute that logic?
And further, is QED saying we now have negative infinite energies in order to cancel out the positive ones? For pre-QED physics, total energy is always a positive quantity in any physical system I know of. Of course, in bound states the total energy is less than the total energy of the constituents, but I don't obviously see what is bound here if we are considering a single particle.
I have heard that QED is the most accurate theory ever. My question really is what experiments prove that, and how many free parameters are being determined as a result of those experiments. I believe the claim comes from truly impressive work, both theoretically and experimentally, on g-2 experiments. I understand that such experiments and theory agree to many, many decimal places. But if the bare mass is set via renormalization through these experiments, then these experiments are really just extremely accurate determinations of the physical bare mass constants. That is still excellent and important science, but it doesn't address my question. And charge gets set via renormalization too. So that should allow a perfect match to the Lamb shift through a determination of bare charge, once the bare masses were calculated by g-2. So next we get to high energy scattering and possibly decay processes, and I don't believe we get all that many 9's of accuracy in those measurements. The scattering measurements will require excellent knowledge of energies and momenta both before and after the events, while the decay processes rely on assumptions of internal structure. So that is what I meant by the question.
Also I think that "the most accurate theory ever" claim comes with at least a tinge of hype. F = dp/dt is still considered exact as far as I am aware, so I don't think QED passes F = dp/dt for accuracy. Of course what happens is that F = dp/dt is used to determine what F, p and t are in some situations. And that gets back to my point. It seems to me that some (maybe most?) of the claimed accuracy of QED comes from the fact that it Is used to determine what the bare m's and q's are.