What is electron? Is it a perfect point? What does it mean?

You check it out. Make sure you understand what Mr. Brown writes down. It's your illiterate interpretation of what you've read. So think about doing what Alphanumeric and now JamesR suggest.

 

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You should have asked Farsight which theoretical model he was referring to. LOL.

 

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Every post you dig yourself a deeper hole with respect to your understanding of mainstream physics and logical argument.

Naked claims not based on calculation while I have already pointed to the mainstream theory (QED) which precisely models all such behaviors without a finite electron size.

You have not elucidated your point over the previous mention (in post #10) of bargepoles and billiard balls in this thread. The bargepole empirical method combined with a theoretical atomic model of water sets an upper limit on the size of a molecule of water. A lower bound wasn't really established until Einstein's 1905 observations on the significance of Brownian motion. While proponents of atomic theory had theoretical models of finite molecule mass, they didn't have evidence of a specific size until 1905. Your position with regard to electron radius is worse off as you don't have a model of electrodynamics which presumes finite electron size that predicts the actual behavior of electrons and photons as well as QED therefore you don't even have theoretical support for the notion that electrodynamics is best explained by finite-sized electrons.

Wrong. There are finite size effects and such effects have empirical support in electron-nucleus studies and none in electron-electron studies which is consistent with the QED assumption electron size is zero.

Correct, but as I was careful to say before, 0 is the best summary of human knowledge and ignorance if the question is to be answered with a single number.

Compton wavelength is \(\frac{h}{mc} \approx 2.43 \times 10^{-12} \, \textrm{m} \) which shows up in the Compton scattering formula for wavelength change of photons scattered from free electrons: \(\lambda' - \lambda = \frac{h}{mc} ( 1 - \cos \theta)\). The derivation of that is semi-classical where the only the photons have quantum energy-momentum relationships with momentum equal to \(\frac{h}{\lambda}\). A hypothetically similar derivation which assumes \(\frac{h}{mc}\) is the radius of the electron and the formula is derived from that makes no sense since the relation between angle of reflection off a hard sphere and momentum transferred is a function only of angle, not the size of the sphere.

https://en.wikipedia.org/wiki/Compton_scattering#Derivation_of_the_scattering_formula

Similarly, electron diffraction experiments confirm the DeBroglie relation between momentum and wavelength of the probability amplitude function for all particles: \(p = \frac{h}{\lambda}\). As the electron momentum ranges from zero in the electron's own rest frame, to at least 104.5 GeV/c at the Large Electron-Positron Collider with corresponding wavelengths from infinity down two \(1.2 \times 10^{-17}\, \textrm{m}\), it follows that electron probability amplitude function are no measure of electron size.

https://en.wikipedia.org/wiki/Large_Electron–Positron_Collider#History
https://en.wikipedia.org/wiki/Matter_wave#Electrons

You phrased that like a statement of faith. It would be better to say there is no empirical support for models of finite electron of photon size over that of QED where both are modeled as point-like. In addition, there is serious tension between your claim that the diffraction-measured wavelength of electrons should be interpreted as size when that same phenomena and same formula \(p = \frac{h}{\lambda}\) was first associated with photons. Your special pleading is readily apparent and reduces the reader's estimate of your position as one with internally consistent logic.

It is experimental fact that under certain conditions, gamma rays impacting on bulk matter can give rise to electron-positron pairs largely consistent with the detailed predictions of QED. That does not say that electrons are made of out photons in the sense of a sandwich being made out of bread, butter and meat. That later opinion is your special claim, not an experimental fact and not the mainstream (QED) interpretation of the real physical phenomena.

Repeating your naked claim does not make it stronger. A single photon by itself has light-like energy-momentum consistent with the photon being a massless particle and \(E^2 = (mc^2)^2 + (pc)^2\). Any number of electrons and positrons has a time-like energy momentum consistent with electrons having finite mass. Thus isolated photons should not be able to turn into observable electron-positron pairs under any relativistic theory. QED agrees with experiment that pair production happens when gamma rays interact with the high electromagnetic field densities of normal atoms especially near heavy nuclei and not in isolation. Thus QED already explains pair production in precise details that can be checked against reality in contrast to your non-mathematical hypothesis that somehow electrically uncharged photons somehow fall into electrically charges bound states that resemble the experimental electron.

https://en.wikipedia.org/wiki/Pair_production#Cross_section

That's only a first order picture of pair production. Details in experiment and QED both indicate that pair production often results in QED-consistent Bremsstrahlung radiation which is hard to explain in your sandwich-parts model. Your sandwich parts model is also inconsistent with quantum theory in that no number of spin-1 particles and orbital momentum can give rise to a spin-1/2 bound state. Your sandwich parts model ignores that QED predicts pair production of electron-positron pairs, muon-antimuon pairs, strange quark-strange antiquark pairs, etc as seen in reality because each particle (electron, muon, quark) has its own quantum field that the electromagnetic field couples to, preserving net electric charge, net strangeness, net color, net muon number, exactly without special bookkeeping mechanisms. Your sandwich parts model doesn't explain why electromagnetic pair production doesn't sometimes give rise to two electrons or an electron-antimuon pair. It also doesn't explain how Z particles can decay into muon-antimuon pairs or how gluons can give rise to quark-antiquark pairs. QED explains so much about electrodynamics and extends naturally to other particles and with some tweaks to other Standard Model forces. The sandwich parts model is an intellectual dead end.

 

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No one has mentioned yet that electrons have fractional statistics, i.e. the quantum Hall effect; what does it say about our understanding of pointlike charges?

What about the recent HOM experiment that splits electrons into two "collective modes", which then dissipate?

My understanding of what electrons are is that, although a lot is known we don't really have the full picture yet. Pontifications in that case can't really amount to much either.

 

First off, apologies to Jarek; your thread seems to have been thoroughly hijacked.

We've been over this. No one cares about the intellectual pedigree of the model in question. It's "your model" in the sense that it's the model you are advocating. Or rather, it would be if you actually presented a model for a change, instead of a loose cluster of ideas that are almost specific enough to make a genuine prediction. Rpenner is doing a solid job with the line-by-line refutation, so I'm just hoping to provide a constant reminder that we really wish you'd give us a proper hypothesis to argue against.

 

But Ehrenberg and Siday used the interaction term of QED, the one I mentioned above, to calculate the effect.

https://en.wikipedia.org/wiki/Aharonov–Bohm_effect

“The underlying mechanism is the coupling of the electromagnetic potential with the complex phase of a charged particle's wavefunction, and the Aharonov–Bohm effect is accordingly illustrated by interference experiments.”​

Thus the empirical effect confirms the predictions of QED. The electron probability amplitude function (\(\psi\)) has a complex phase and couples locally to the electromagnetic potential (\(A_{\mu}\)) and therefore two different paths give rise to interference of the complex phases and results in variation in the probability of finding the electron. At no place does a co-variant size of the electron enter the picture. Your citation of authority is inapposite.

(Image taken from http://cns-alumni.bu.edu/~slehar/fourier/fourier.html )

You've missed the point about the relation between momentum and position, possibly because you have not worked with Fourier transforms with respect to quantum theory.

A complex Gaussian wave packet might have a position representation (at time t=0) of \(\psi(x) = \frac{1}{\sqrt[4]{2 \pi L^2}} e^{i k_0 x} e^{-\frac{x^2}{4 L^2}}\).
The Fourier transform has the same information: \(\Psi'(k) = \sqrt[4]{\frac{2 L^2}{\pi}} e^{- L^2 (k - k_0)^2}\).
\(\psi(x) = \frac{1}{\sqrt{2 \pi}} \int_{-\infty}^{\infty} \, \Psi'(k) \, e^{ikx} \, dk\).

That's just a mathematical formalism common to all smooth functions. But in quantum physics, we effectively use units such that \(\hbar = p/k = 1\) so that
\(\Psi'(k) = \Psi' (p / \hbar ) \propto \Psi(p )\) which allows one to establish analogues for the Heisenberg uncertainty bounds for all wave phenomena and prove that Gaussian packets minimize the product of the variances.

Details are standard in any undergraduate textbook for a year-long course in quantum mechanics and are regularly summarized for review in introductory textbooks on relativistic quantum theory.

http://quantummechanics.ucsd.edu/ph130a/130_notes/node84.html
See also R. Shenkar, Principles of Quantum Mechanics.

You don't dispute that they are naked assertions. You likewise have done a poor job of showing that your claims follow from the evidence or that you have had substantial physics education. Thus your claims that they are not naked assertions are also naked assertions.

You are welcome to attempt to demonstrate this from the QED Lagrangian density, but there have been given many reasons to suspect the matter is not merely one of conflicting interpretations.

Clear as mud. Pair production was predicted as a consequence of symmetry of the QED Lagrangian density which made pair production (1933) and annihilation in a very real sense as expected as Coulomb repulsion. The coupling between the electron field and the photon field in QED is time-symmetric so the Feynman vertex diagram (in perturbation theory) for photon-electron interaction can be time-oriented in any way provided that energy, momentum, angular momentum and charge are conserved.

That's an incorrect reading. My claim was that you failed to cite authorities in a way that those authorities, in context, would support. You were the one calling me an authority and I explained that you had taken my support for QED as also describing bound states mediated by electromagnetic attraction (c.f. positronium) with complicated wave functions in both electron and photon fields out of context to attempt to support your notion of electrons as bound states of photons.

Those are naked claims, not part of the mainstream, not part of a precise model of electrodynamics, not an interpretation of QED and resting on your own soi disant authority. It is for that reason that James R asked you to leave such stuff out the mainstream discussions that should be hosted on this subforum.

I have talked about the details of QED, the simplest mainstream theory. If by "this stuff" you mean your naked claims, then you have been invited by James R to discuss it in another subforum. Like this one:
http://www.sciforums.com/threads/electromagnetism-quantum-mechanics-or-vortices.143937/

 

There is both an integer quantum Hall effect and a fractional quantum Hall effect. In the latter case it is the charge carriers in 2-D condensed material (i.e. solids and liquids) physics which have fractional statistics, which reflects one of the ways 2+1 quantum field theory has a different character than 3+1 quantum field theory. The microscopic details about how exactly 3+1 QED and certain configurations of real materials equates to 2+1 quantum field theory is a matter of ongoing research.

http://www.nobelprize.org/nobel_prizes/physics/laureates/1998/
https://en.wikipedia.org/wiki/Fractional_quantum_Hall_effect

This is an active field of research with experimental results consistent with QED. Because it is so active, there have been many recent papers and news articles since 2011, and I'm not sure which exact experiment you mean.
(Searching for HOM experiment may return NSFW results!)
https://en.wikipedia.org/wiki/Hong–Ou–Mandel_effect
http://www.phys.ens.fr/~placais/publication/2015_ncomm_Freulon_HOM-fractionalization.pdf

Our knowledge should be recognized as bounds on our ignorance. QED is not the whole story. The Standard Model may not be the whole story. But even if the Standard Model were the whole story, just having a fundamental physical theory doesn't make pulling out real-world predictions of complicated experimental setups trivial.

 

Much appreciated.

Harsh language, completely justified as fair comment based on years of evidence here and elsewhere.

I would say they summarize the real state of knowledge of the behavior of electrons and photons. To actually get into the details of the physical descriptions prescribed by current knowledge I would have to work through about eight examples (Rutherford scattering, Møller scattering, Bhabha scattering, Mott scattering, annihilation, pair production, finite size effects and the Lamb shift, renormalization) in such excruciating detail no one would read it who didn't already have access to superior textbooks.

It's not clear that he sees the utility of mathematics, logical self-consistency, external validation or gentle warnings.
http://www.dartmouth.edu/~matc/MathDrama/reading/Wigner.html
https://schneider.ncifcrf.gov/Hamming.unreasonable.html
http://rationalwiki.org/wiki/Principle_of_explosion
https://en.wikipedia.org/wiki/Principle_of_explosion
https://en.wikipedia.org/wiki/Peer_review

His public presentation is one of the reasons I try to summarize what a scientific theory is and communicate that in an attempt to set a standard for later debate.

A physical theory is a useful, precise, communicable framework for predicting the behavior of a wide variety of related observable phenomena.​

http://scientificlegaltourist.tumblr.com/post/128514874536/fundamental-principles-in-physics

 

Abuse is no substitute for addressing the patent blatant evidence for the wave nature of matter.

 

A loaded term, since in context you cannot mean "misuse" or "cruelty" but rather "disparagement." Indeed by describing you as a "fraud" he is saying your claims of accomplishment are without justification, which is fair comment on some percentage of your posting history. When people seek justification of your claims they come away empty-handed. The defense against such disparagement is to either withdraw the claims or provide the justification. In the past you instead tended to double down on the baseless claims and contextomy.

Evidence does not speak for itself. It's up to rational speakers to gather and curate evidence and present it as part of a reasoned argument for a point of view. You can't just name phenomena and nakedly assert they support your claims. That's not what Newton did, not what Maxwell did, not what Einstein did, not what Minkowski did, etc.

That was never a point of contention. Quantum Field Theories like QED incorporate the DeBroglie hypothesis and for any free particle in any QFT system we have:
\( E^2 = (mc^2)^2 + (c \vec{p})^2, \; E \vec{v} = c^2 \vec{p}, \; E = hf = \hbar \omega, \; p = \frac{h}{\lambda} = \hbar k, \; \vec{p} = \hbar \vec{k}\)
\(v_{\textrm{group}} \equiv \frac{\partial \omega}{\partial k} = \frac{\partial E}{\partial p} = \frac{\partial \sqrt{(mc^2)^2 + (c p)^2}}{\partial p} = \frac{1}{2 \sqrt{(mc^2)^2 + (c p)^2}} \times 2 c^2 p = \frac{c^2 p}{\sqrt{(mc^2)^2 + (c p)^2}} = \frac{c^2 p}{E} = v\)
\(v_{\textrm{phase}} \equiv \frac{\omega}{k} = \frac{E}{p} = \frac{c^2}{v_{\textrm{group}}} = \frac{c^2}{v}\)

The actual topic introduced by Jarek was whether the electron should be considered point-like.The defining difference between point-like objects and extended objects is that changes to point-like objects happen all-at-once while spatially extended objects require time for changes to propagate. QED describes a quantum field theory of point-like electrons and photons. There is nothing in QED which suggests transfers of angular momentum, linear momentum or energy between photons and electrons takes any time. You wished to introduce claims about the electron that have never been accepted by the mainstream or supported by evidence. You wished to substitute an analogy based on a misinterpretation of a wikipedia diagram on the behavior spinors under rotation for the mathematics of spinors themselves. You would have mislead people about the subject of a paper by Maxwell where you performed a contextomy of an abstract diagram from its caption.

You have a great sense of self-entitlement to express opinions on what physics should be but never seem to get around to doing physics better. And that is what I find to be "abuse" — misuse of your self-claimed authority and your long-ago considered and rejected proposals, misuse of citations of authorities who don't hold the position you say they hold, miseducation about topics of Wikipedia articles, etc.

 

James: abuse won't make renormalization go away either.

 

The Wikipedia article you link to does not justify any dispute with renormalization and you make no such reasoned argument yourself.

Renormalization doesn't "fix" QED -- it fixes the divergent integrals in the perturbation theory built to calculate physical quantities from QED. As it turns out the hand-wavy math (c. 1953) turns out to be closely related to features of QED that justify such slight of hand (c. 1972), just like Cauchy (1821) justified the slight of hand used in the original formulations of calculus (c. 1670).

Physicists have goals that are different than pure mathematicians and let their intuition of how math should work occasionally run ahead of what math can be shown to work. But you appear to have missed the boat on this by 43 years.

http://www.nobelprize.org/nobel_prizes/physics/laureates/1982/

 

Renormalization is a "fudge" to "fix" a problem wherein treating particles as point particles leads to infinities. It's a clear demonstration that the mathematics of point particles is incorrect, just as the hard scientific evidence of the wave nature of matter demonstrates that the concept of point particles is incorrect. And by the way...

...it's "sleight" of hand.

Gamma gamma pair production, electron diffraction, electron optics, electron magnetic moment, the Einstein de-Haas effect is not some loose cluster of ideas. These things are scientific evidence which demonstrate the electron is not a point particle. As does the need for renormalization.

No he isn't. He dismissed the hard scientific evidence and shot himself in the foot with the knot of quantum field. And so totally lost the argument. Now he's trying to bury the thread in a wall of unsupported assertions. Tsk. Now I'll have to wade through his waffle and shoot him down yet again.

Jarek: apologies. I'll wait a while to give you a chance to reclaim the thread. I hope you have nevertheless obtained something useful so far. Such as some further examples of the evidence for the wave nature of matter, and a few useful hyperlinks. And perhaps a taste of the utter desperation with which some people will attempt to defend a "lies to childen" claim which is utterly contradicted by the scientific evidence. I rather think that particle physicists have painted themselves into a corner with this and related claims, and that this has contributed to the demise of HEP in the USA.

 

I probably should not post, but "renormalization" was being developed when I was a physics graduate student. I did not like it nor the trend toward mathematics dominating my type of physics ("string and sealing wax," experimental); but it is not a trick. It is a procedure that permits calculation for observable results. Sort of like imaginary numbers are very useful for the analysis of electrical circuits.

I don't see that any of these disprove a possible point nature for the electron, but the way humans think, it is easier to understand and model these phenomina with non-points. There are many things that seem, by human understanding, to be impossible, but are demonstrated. For example I have personally shown that a photon can be more than a meter from its self.* As electrons do exhibit interference I assume the same methodology could be applied to them, also showing they can be more than a meter from them selves.

The real world is too strange for human understanding, so IMHO, it would be wise to not be too dogmatic one way or the other about the point nature of the electron.

* How I did that is described here: http://www.sciforums.com/threads/proof-of-the-existence-of-god.144082/page-40#post-3317138 Why it got posted in that thread, I forget. It certainly has nothing to do with the existance or not of God. I think it was posted elsewhere too, but I found this link first.

 

Farsight claims mainstream theory QED assumes electrons and photons are point particles. FTW. Jared there is your answer again.

In other news, Farsight doesn't like the way renormalization fixes the approximate methods to extract solutions from QED as found by perturbation methods. That would be a more impressive opinion if the first paragraphs of the Wikipedia article Farsight linked do didn't pooh-pooh his concern as antique or if Farsight could write exposition on Jeffries-Wentzel-Kramers-Brillouin expansions in general. But not only is QED mainstream physics, it is the gateway to the pinnacle of mainstream particle physics and so part of every serious particle physicist's education. Farsight's gut feelings about potentially dodgy math aren't justified by the history of said math or Farsight's history with math.

Had to look that one up in a dictionary, and can't blame it on autocorrect. Also, post #23 has "down two" where clearly "down to" is meant. Don't even ask me how that happened.

But since "sleight of hand" is "the use of dexterity, especially so as to deceive" a more correct phrase might be "sleight of logic" to mean "the use of cunning, especially so as to deceive" with the pejorative connotation meant ironically since later justifications were found as the 1982 Nobel lecture and the article Farsight linked to reveal.

Correct -- they aren't ideas at all. They are all physical phenomena which are precisely modeled by the physical theory called QED, in the sense that “[a] physical theory is a useful, precise, communicable framework for predicting the behavior of a wide variety of related observable phenomena” as I claimed above.

So you have claimed, but not demonstrated. So whatever your idea is, it has not been shown to be useful, nor is it precise as it is mathless and you have never stated a fixed size of the electron, nor is it communicable as you don't tell us what your idea is but only give us diagrams of things other people drew about other things and analogies, nor is it a framework for predicting behavior of observable phenomena. Instead of a physical theory, your idea appears to be that you are some unimpeachable authority on the nature of the electron and the states of physics. But the proof of the pudding is in the eating and your audience has starved for years waiting for you to do physics better, the hallmark that distinguishes the insightful thought leader from the sea of crackpots.

As above, mutatis mutandis.

I disputed you did more than name physical phenomena and claimed you failed to argue your point from the evidence provided by such phenomena. So it was your efforts in this thread that I categorically dismissed, but never the physical evidence.

I pointed out that in that quote or paraphrase I was talking about bound systems in QED and pointed out your citation of my claim was inapposite to application to a non-QED idea that an electron is a bound state of photons. Thus you failed at textual analysis and failed in contextomy.

For most points, I'm still waiting for you to take the field. But congratulations for winning the all-important "sleight of hand" victory.

Any apparent lack of utility of my writing is more a function of the state of mind and education of the reader. To the extent I favor readers that value mathematics, logical self-consistency, and taking the time to form an argument rather than just name phenomena and assume that people will find a chain of logic without a guide, I apologize. It's the way I was taught to present ideas in writing.

See post #13 where I point out QED assumes based on current experimental evidence that electrons are points and the beginning of post #34 where Farsight agrees that QED assumes electrons are points.

See post #31 where demonstration that QED is a wave theory.

All phenomena cited by Farsight have been well known for decades. QED is not "lies to childen" but the subject of the 1965 Nobel prize and very close to the best summary of particle physics in mainstream use today where electrons are still modeled as point-like.
http://www.nobelprize.org/nobel_prizes/physics/laureates/1965/

Here Farsight acknowledges his ideas are not the ones in the mainstream. He's concern trolling mainstream physics.

 

I wished to limit myself to describing the current state of knowledge with respect to electron size and discussion of how it is modeled in QED. Physical theory as a summary of human knowledge about the behavior of phenomena should not be used to make unsubstantiated claims about the nature of reality, so the fact that electrons are points in QED and QED is very successful is only evidence that the charge radius of an electron is not larger than \(10^{-22} \, \textrm{m}\) with potential for future experiments to either improve on that upper bound or find a lower bound that is different from current theoretical assumptions of 0.

 

Yes, but he's the mods lovable fraud, which is why he will be back again and again 'fruading' ( is there such a word?).

 

Seems to me that rpenner is an authority on every subject he speaks about. It's great that he chooses to share his scholarship with the members of this forum. Thanks.

 

It sort of reminds me of the mother lioness bringing back live prey, so that the young can practice killing...you see even Farsight has a purpose.