Experimental boundaries for size of electron?

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Expand view Topic review: Experimental boundaries for size of electron?

Re: Experimental boundaries for size of electron?

Post by JohnDuffield » Tue Mar 05, 2019 1:19 pm

Hi Jarek. I've looked into this. IMHO there's actually no evidence that the electron is small. Yes, the particle data group will tell you that electrons “are definitely smaller than 10ˉ¹⁸ meters”, but when you look for the supporting evidence, it just isn't there. See the 2002 paper limits on sizes of fundamental particles and on gravitational mass of a scalar by Irina Dymnikova, Juergen Ulbricht, and Jiawei Zhao. They talk about the QED reaction e+e− → γγ(γ) at energies between 91GeV and 202GeV. That’s high-energy electron-positron annihilation to gamma photons. They say the interaction proceeds via the exchange of a virtual or “excited” electron with a mass greater than 402 GeV, and the characteristic size of this is less than 1.17 x 10ˉ¹⁷cm. They also say that they assume that a fundamental particle must have a de Sitter vacuum core related to its mass, with a finite geometrical size defined by gravity. This de Sitter vacuum core is hypothetical. It cannot be employed to support a claim that relies upon a virtual electron exchange. Not when virtual particles "only exist in the mathematics of the model". There’s no evidence that a 402 GeV electron is exchanged between the electron and the positron, and there’s no evidence for the de-Sitter vacuum core. So there’s no evidence here that the electron is small.

On Wikipedia you can read that “observation of a single electron in a Penning trap shows the upper limit of the particle’s radius is 10ˉ²² meters”. But when you follow up on the references and read Hans Dehmelt’s 1989 Nobel lecture you realise that the upper limit is merely an extrapolation. It’s an extrapolation from a measured g value, which relies upon “a plausible relation given by Brodsky and Drell (1980) for the simplest composite theoretical model of the electron”. The extrapolation yields an electron radius R ≈ 10ˉ²⁰cm, but it isn’t a measurement. Especially when “the electron forms a 1 μm long wave packet, 30 nm in diameter”. When you track back to Brodsky and Dell you can read the anomalous magnetic moment and limits on fermion substructure. And what you read is this: “If the electron or muon is in fact a composite system, it is very different from the familiar picture of a bound state formed of elementary constituents since it must be simultaneously light in mass and small in spatial extension”. The conclusion is effectively this: if an electron is composite it must be small. But there’s no actual evidence that it’s composite. So it’s a non-sequitur to claim that the electron must be small. So again there’s no evidence here that the electron is small.

The electron isn't small. Its field is what it is. It isn't some billiard ball thing that has a field. It is field. It's got the Compton wavelength it's got because h is what it is.

Re: Experimental boundaries for size of electron?

Post by Jarek » Wed Feb 13, 2019 1:16 pm

As written, it concerns only first moment, not excluding e.g. quadrupole moment like plus - minus - plus.

Re: Experimental boundaries for size of electron?

Post by FrediFizzx » Wed Feb 13, 2019 12:44 pm

Jarek wrote:So neutron is perfectly spherically symmetric? ... built of 3 quarks ...

The "perfect ball" fairy tale is only to convince public that another experiment reducing boudary for EDM makes sense ...
Electron has huge magnetic dipole moment - is tiny magnet ... is at most cylindrically symmetric.
Zero EDM means only that ... e.g. + - + quadrupole has also zero EDM, but has nonzero radius and is not spherically symmetric.

Well, zero EDM means that the electron's electric charge radius is perfectly spherical. Of course its "magnetic charge" radius is not perfectly spherical.

Re: Experimental boundaries for size of electron?

Post by Jarek » Wed Feb 13, 2019 12:25 pm

So neutron is perfectly spherically symmetric? ... built of 3 quarks ...

The "perfect ball" fairy tale is only to convince public that another experiment reducing boudary for EDM makes sense ...
Electron has huge magnetic dipole moment - is tiny magnet ... is at most cylindrically symmetric.
Zero EDM means only that ... e.g. + - + quadrupole has also zero EDM, but has nonzero radius and is not spherically symmetric.

Re: Experimental boundaries for size of electron?

Post by FrediFizzx » Wed Feb 13, 2019 10:09 am

Yeah, sorry EDM is just how much it deviates from a perfectly spherical shape. Nothing to do with size.

Re: Experimental boundaries for size of electron?

Post by Jarek » Wed Feb 13, 2019 4:03 am

If you want to conclude from dipole moments, so what about magnetic dipole moment of electron?
It is ~1000x larger than of proton, does it mean that electron is 1000x larger?
Neutron has similar boundaries for EDM ( https://en.wikipedia.org/wiki/Neutron_e ... ole_moment ) - do you also conclude its size from it?

Re: Experimental boundaries for size of electron?

Post by FrediFizzx » Tue Feb 12, 2019 10:41 am

Jarek wrote:Arnold Neumaier has responded on stack ( https://physics.stackexchange.com/quest ... f-electron ) - he has gathered many materials on this topic:
https://www.mat.univie.ac.at/~neum/phys ... tlike.html
But still no clear argument that electron is much smaller then femtometer (?)

Anyway, to better specify the problem, define E(r) as energy in a radius r ball around electron.
We know that E(r) ~ 511keVs for large r, for smaller it reduces e.g. by energy of electric field. Assuming perfect point charge, we would get E(r) -> -infinity for r->0 this way. Where does divergence from this assumption starts?
More specifically: for example where is maximum of E'(r) - in which distance there is maximal deposition of 511keVs energy?
Or median range: such that E(r) = 511/2 keVs.
It is not a question about the exact values, only their scale: ~femtometer or much lower?

What about electric dipole moment of an electron?

http://www.doylegroup.harvard.edu/wiki/ ... ersion.pdf

Does this not indicate that the charge radius of an electron must be smaller than 4.3 x 10^-30 cm?
.

Re: Experimental boundaries for size of electron?

Post by Jarek » Tue Feb 12, 2019 1:34 am

Arnold Neumaier has responded on stack ( https://physics.stackexchange.com/quest ... f-electron ) - he has gathered many materials on this topic:
https://www.mat.univie.ac.at/~neum/phys ... tlike.html
But still no clear argument that electron is much smaller then femtometer (?)

Anyway, to better specify the problem, define E(r) as energy in a radius r ball around electron.
We know that E(r) ~ 511keVs for large r, for smaller it reduces e.g. by energy of electric field. Assuming perfect point charge, we would get E(r) -> -infinity for r->0 this way. Where does divergence from this assumption starts?
More specifically: for example where is maximum of E'(r) - in which distance there is maximal deposition of 511keVs energy?
Or median range: such that E(r) = 511/2 keVs.
It is not a question about the exact values, only their scale: ~femtometer or much lower?

Re: Experimental boundaries for size of electron?

Post by Q-reeus » Thu Nov 08, 2018 8:40 am

Jarek wrote:...Regarding charge quantization - you need any mechanism (e.g. topological), then just define/calibrate its lowest nonzero charge as 'e'.
I was looking for quantization mechanism in the paper you linked, but without success - could you briefly explain this mechanism?

He he. I suggest re-reading that article several times. The author builds an overall concept slowly and from numbers of subtle non-linear phenomena. Particle physics is very not my forte. Ditto for self-organizing dissipative structures. If it really interests, consider contacting him directly for expert clarification.

Re: Experimental boundaries for size of electron?

Post by Jarek » Thu Nov 08, 2018 7:37 am

Regarding hydrodynamics, the real QM model is dBB pilot wave: substituting psi = sqrt(rho) exp(iS) to Schrodinger and looking at equations for density rho and action S: https://en.wikipedia.org/wiki/Pilot_wav ... e_particle
It gives interference in double-slit experiment as tested e.g. in http://science.sciencemag.org/content/332/6034/1170
Walking droplets is not the same but have some similarities - I don't understand how inability of some people to recreate interference says anything about its success in recreating charge quantization? Does somebody also claim inability to recreate these orbit quantization experiments?
Can you show that they are somehow equivalent?
That its quantization mechanism is incorrect: (described by stationary Schrodinger) standing wave as having the lowest energy? Do you know any other quantization mechanism?

Regarding charge quantization - you need any mechanism (e.g. topological), then just define/calibrate its lowest nonzero charge as 'e'.
I was looking for quantization mechanism in the paper you linked, but without success - could you briefly explain this mechanism?

Re: Experimental boundaries for size of electron?

Post by Q-reeus » Thu Nov 08, 2018 6:56 am

This may seem harsh but if an analog model predicts everything fine except for one crucial feature (say one-particle-at-a-time double slit interference pattern) then it fails, period. One either looks for another conceptual scheme that can explain it and the other aspects, or accept QP as primary in itself and without deeper explanation.

Re charge quantization - my point was that deriving the value, not necessarily the phenomena itself, has to presuppose one or more primitives ab initio. Planck constant, HUP, de Broglie relations, permittivity/permeability, or such. Manasson starts with such primitives in place and it will be likewise with your mentioned topological charge scheme(s). Maybe I misinterpreted your initial criticism of Manasson article.

Re: Experimental boundaries for size of electron?

Post by Jarek » Thu Nov 08, 2018 1:57 am

Once again, no one claims that hydrodnynamical analogues give perfect agreement - there are many differences, they only provide valuable intuitions ... especially for orbit quantization in many settings - including double quantization (of separately radius and angular momentum like in Bohr-Sommerfeld: https://www.nature.com/articles/ncomms4219 ) and Zeeman effect (using Coriolis force in place of Lorentz force: https://journals.aps.org/prl/abstract/1 ... 108.264503 ).
This is the only intuition for quantization, nonradiation I know: that coupled wave needs to become standing wave to minimize energy - do you have some objection to it or a different explanation?

Regarding "no-one can" for charge quantization, I disagree - mathematicians know well quantization of topological charges.
Take vector field v preferring unit lengths due to Higgs potential: V(v) = (1-|v|^2)^2.
It can get topologically nontrivial configuration, e.g. hedgehog: v(x) ~ x/|x|, there is Gauss(-Bonnet) law for them and they can only get quantized possibilities e.g.
Image

Re: Experimental boundaries for size of electron?

Post by Q-reeus » Wed Nov 07, 2018 11:57 pm

Jarek I have no pretensions to expertise in these difficult subjects. Regarding your first criticism - that Manasson's approach doesn't predict the absolute value of charge quantization (completely ab initio), well no-one can without assuming some relations a priori as brute facts. For instance, linking field strength to field energy density, one has to write in by hand given values for vacuum permittivity and permeability. But with few assumptions, his scheme seems to go very far in explaining (nearly) all of particle physics! But not Bell. For an ongoing discussion, see:
https://www.physicsforums.com/threads/q ... al.958582/

Regarding clear absence of double slit interference for Couder bouncing drops experiments, how is resorting to inherently non-local DBB theory going to leave other Couder results any more than interesting analogues to actual QP, but now shown to be without full correspondence?

Re: Experimental boundaries for size of electron?

Post by Jarek » Wed Nov 07, 2018 10:27 pm

Regarding problems with recreating interference, which is even further from the title: experimental boundaries for size of electron (maybe let's take it to dedicated: viewtopic.php?f=6&t=361 ), these are only (hydrodynamical) analogues - instead we need to use de Broglie-Bohm: obtained by substituting phi = sqrt(rho) * exp(iS) to Schrodinger equation, and confirmed experimentally e.g. while (weakly) measuring average trajectories of interfering photons: http://science.sciencemag.org/content/332/6034/1170
And instead of interference, we are talking here about intuitions for orbit quantization to prevent synchrotron radiation - orbit quantization was obtained in multiple ways for walking droplets by different groups - providing clear intuition: that to minimize energy of e.g. electron-proton system (they cannot join as neutron is much heavier), the coupled (pilot) wave needs to become a standing wave (described by stationary Schrodinger equation) - otherwise it would have additional energy in form of fluctuations.
Do you disagree with such intuition for nonradiation?

Regarding vacuum self-organizing into particles - localized stable energy configurations (formally called solitons), I generally agree.
The most crucial question there is explaining charge quantization (barely mentioned in the paper you have linked) - having that, e.g. electron is just the simplest (lightest) negative (quantized) charge.
Charge quantization is a restriction for Gauss law: that integrating electric field over a closed surface, the returned charge is not any real number like in standard EM, but an integer multiplicity of e (or e/3).
But there is also quantized version of Gauss law: topological Gauss-Bonnet theorem says that integrating curvature of a vector field over a closed surface, we get topological charge inside - which has to be integer.
Hence interpreting curvature of some deeper field as EM field, we get quantized (by topology) charges governed by electromagnetism (Faber's model of electron): https://www.dropbox.com/s/aj6tu93n04rcgra/soliton.pdf

Re: Experimental boundaries for size of electron?

Post by Q-reeus » Wed Nov 07, 2018 8:21 pm

Re: Experimental boundaries for size of electron?

Post by Jarek » Wed Nov 07, 2018 5:14 am

Regarding nonradiation condition, this is a question for from the size of electron: ~10^-10m vs ~10^-15m.

But generally it is strongly connected with quantization condition - if electron is not exactly in one of orbitals, it should quickly get to a close orbital and release the abundant energy as EM radiation (photon) - time of such process should be in attosecond scale: http://science.sciencemag.org/content/328/5986/1658

The best intuitions for orbit quantization come from walking droplets experiments - allowing to get orbit quantization in a few different ways (slides 11-22 here).
Generally it comes from ("pilot") wave created by electron's internal clock (de Broglie's/zitterbewegung) - it will have the lowest energy if becoming a standing wave (described by stationary Schrodinger), which we will get if satisfying (Bohr-Sommerfeld like) quantization condition: the clock has to perform integer number of ticks during a single orbit.
Here are nice videos: http://www.pnas.org/content/pnas/suppl/ ... rgetid=SM1 from http://www.pnas.org/content/107/41/17515

Image

Re: Experimental boundaries for size of electron?

Post by _Jim » Thu Oct 04, 2018 7:40 am

Nothing referenced by Hermann Haus regarding electrons, or the size thereof? It would help, perhaps, if we considered the electron in two or three known environs when considering size, e.g. when bound in an atom or free-space environ ...

Added, also Haus, who was working on development of a “free electron” laser. One would think he had some insights in this matter.

Some work by Haus shown here: https://wikivisually.com/wiki/Nonradiation_condition

Re: Experimental boundaries for size of electron?

Post by Jarek » Sun Aug 26, 2018 12:00 am

I am asking for objective size of resting electron - energy dependence (Lorentz contraction) should be removed by Lorentz transform to resting electron.
Sure, definition of particle's radius is nontrivial - they use root-mean square for composite particles: weighted average of squares of distances (e.g. negative for neutron due to positive charge being closer to center).

For non-composite particle like electron, we could define energy profile: E(r) as energy inside radius r sphere around electron.
We know that E(r) ~ 511keV for large r.
Increasing r, we need to add energy of EM field, so E(r) should be increasing.
One question is r->0 behavior, assuming electron being perfect point we would have E(r) -> - infinity.
To get E(r) -> 0 for r -> 0, we need to modify electric field of perfect point in femtometer scale.
Generally, we could define e.g. median radius: such that E(r) = 511/2 keV.

Experiments have shown that an electron must be smaller than 10^{-22} meters.

Great - this is exactly what I am asking for - could you point these experiments?
Are you referring to arguments based on g-factor: using Dehmelt's fitting parabola to two points (no kidding - top plot) ?

Re: Experimental boundaries for size of electron?

Post by FrediFizzx » Sat Aug 25, 2018 11:25 pm

Well..., effectively an electron has two "sizes". At low energy-momentum, they scatter off each other as if their size was of order of about the Compton wavelength. That is due to the screening effects. At high energy they scatter as if they are point-like. Experiments have shown that an electron must be smaller than 10^{-22} meters. We find that they are possibly of order of 10^{-34} meters very near to Planck length due to gravitational torsion.

Re: Experimental boundaries for size of electron?

Post by Jarek » Sat Aug 25, 2018 11:01 pm

Compton wavelength of electron is relatively huge: 2.4pm, electron-positron scattering (and energy of electric field) suggests thousand times smaller fm-scale radius ...
Also baryon size is fm-scale, electron shouldn't be thousand times larger.
With pm-scale electron radius interaction with nucleus should be frequent, but it is relatively rare: https://en.wikipedia.org/wiki/Electron_capture https://en.wikipedia.org/wiki/Internal_conversion

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