Is the electron a particle or field?

[Pedraam]

I was having a casual conversation with my uncle the other day and he basically told me that electron is a field. Essentially he claimed that there is an electron field that encompasses the whole universe (like the Higgs field) and what we think of as an "electron particle" is just a fixed point of energy of that field. It also explains why we can't see or even accurately predict where an electron is.

I want to know how true what my uncle is saying actually is. If we could somehow see in electron would it really be a particle?

 

[Nugatory]

The electron isn't a field, but it is a quantized excitation of one. It is also really a particle - but in quantum mechanics the word "particle" means something rather different than the ordinary English-language meaning of the word, so saying that it's really a particle isn't especially helpful. Whatever it is, it is definitely not a small solid object like a grain of sand but even smaller.

 

[bhobba]

Specifically it's a quantum field. Its a special type of field (to be exact a field of quantum operators) that has some very interesting mathematical properties.

See the following for nine different but equivalent formulations of ordinary QM:
http://www.colorado.edu/physics/phys5260/phys5260_sp16/lectureNotes/NineFormulations.pdf

See formulation F - Second Quantisation Formulation.

Well it turns out if you do some mathematical manipulations on a quantum field you can find in virtually any QFT textbook it can be put in the form for formulation F. Now that's simply plain - well astounding - and how the field and particle picture are reconciled in QFT - they are the same thing - amazing but true.

So yes your uncle is correct - there is an electron field permeating the whole universe, a photon field as well, and any other elementary particle you can name. But it really is the same as particles.

The following on the photon field may help - it explains an otherwise complete mystery - spontaneous emission - only by going to this combined particle-field picture can it be explained:
http://www.physics.usu.edu/torre/3700_Spring_2015/What_is_a_photon.pdf

Thanks
Bill

 

[Dadface]

I'm just picking up on this stuff and all I want, just for interest sake only, is to get a rough idea of what it's all about. Now it's been stated here "that an electron field permeates the whole universe" and that "an electron can be described as a quantum excitation of the field". Am I right in assuming that it's only the excitation, namely the electron itself that can be observed. Or does the field have other characteristics that can be observed? I hope this is relevant to the question asked by Pedraam. If not I will start another thread.

 

[bhobba]

Or does the field have other characteristics that can be observed? I hope this is relevant to the question asked by Pedraam. If not I will start another thread.

Yes - for example see the linked paper on spontaneous emission.

Thanks
Bill

 

[Dadface]

Thanks for your reply. I think I've scanned through that paper before and I've just taken another look. It mentions different things including electrons, positrons and photons. And I assume that all of these are excitations of underlying fields and it is the excitation parts of the fields that we observe. But are there any regions of a field where at any particular time there are no excitations and if so can those regions be detected?

 

[bhobba]

But are there any regions of a field where at any particular time there are no excitations and if so can those regions be detected?

Well quantum fields and particles are really the same thing as I tried to get across. Saying they are excitation's of an underlying field is simply a heuristic - QFT field - particle - same thing. Now taking that view makes your query a bit hard to answer, but I will say this - it its possible to have a quantum field where if you measured the position of a particle it will be a definite position and if you measured it anywhere else you would not get a particle.

Thanks
Bill

 

[vanhees71]

Well, it's not as simple as that. First of all one must tell everybody who wants to learn QT that you have to give up the classical worldview. A "particle" at the quantum level is neither a classical particle (which is necessarily a sufficiently large macroscopic object, which is not prepared in a state where it shows quantum properties itself) nor a classical field (which from the point of view of quantum theory is a coherent state).

The most fundamental theory of elementary particles is the Standard Model, which uses relativistic quantum field theory to describe them (including all the matter around us and many more subatomic particles which are created in collisions at men-made accelerators and in nature by collisions of high-energetic cosmic rays). Here the concept of "particle" is quite abstract, being defined as a single-quantum asymptotic free Fock state of a quantum field. There's no other (compact) way to define what the theoretical physicist of the 21st century understands if he talks about "particles". To make sense of this, you have to study relativistic QFT.

 

[Dadface]

Thank you bhobba and vanhees 71. I'm picking up QFT bit by bit and I think it's something I will return to now and again. It's quite interesting.