[geordief (OP)]

The photon is the force carrier of the em field (hope I got that right) and has no mass.


Is it considered as an excitation  in that field?

And what about the electron?Is it just an excitation  in the electric field?

So can both  massless and massive particles be modeled as excitations of their respective fields?

Hope I have not made too many basic errors in my question..

[Origin]

So can both  massless and massive particles be modeled as excitations of their respective fields?

Quantum field theory treats all fundamental particles as field excitations.

[geordief (OP)]

So can both  massless and massive particles be modeled as excitations of their respective fields?

Quantum field theory treats all fundamental particles as field excitations.

Was I right about the respective fields that the photon and the electrons are modeled as  excitations  of?

Are all fields the same kinds of mathematical or physical  object or are some fields fundamentally  different  from other fields?

I am guessing that the Higgs  field might be fundamentally  different  but I know very little of it.

[Eternal Student]

Hi.

   I'm learning that keeping things short is better for everyone.   Here goes...

@Origin  basically had it right.   The only thing that may be lacking is some detail and more explanation.

The photon is the force carrier of the em field (hope I got that right) and has no mass.

   That is good enough for school and almost exactly what was written on an A-level syllabus a year or two ago.  Well done.

Is it considered as an excitation  in that field?

   Depends on how fundamental you want to go.    One of the most fundamental theories we have is QFT.   In that, a photon is an oscillation in its own field which can be called the photon field.  The photon field is not same as the em field.

    QFT does not have an em field.   However, when you do the calculations and start considering things on a bigger scale then certain behaviours and macroscopic properties emerge.  An EM field will emerge once you at a big enough scale   (it would still be small but bigger than the fundamental scale of QFT).

     You could choose not to start at such a fundamental level.   Science is just about having some models.   So you could choose to assume an Electric and magnetic Field exists and just start from that level.   In that case, EM radiation can certainly be well modelled as an oscillation in the Electric and Magnetic fields.

    Now you said "photon" which is complicated.   That's a Quantum Mechanical object while electromagnetism is just a classical theory not a quantum theory.  We don't need to spend too long discussing that.   It's sufficient to note that there's very little reason from the classical theory why photons, or indivisible little packets of em radiation, should exist.  As such modelling a photon with just a classical theory is bound to be limited.  None the less it's a simplification that is sometimes done.

And what about the electron?Is it just an excitation  in the electric field?

   No.   electron and electric sound similar but that's almost about as far as it goes.   The names have some history that explains why they would be similar.   We probably don't need to discuss that history.   
    In QFT, electrons have their own field usually called the electron field.
    In classical theories, electrons are just particles and not considered as anything like a field or an oscillation in someone else's field (like the electric field) that is assumed to exist.   A moving electron can cause an oscillation in the electric and magnetic fields but the electron itself is not an oscillation in those fields.
    There are theories in-between the two,  electrons can be modelled as Quantum Mechanical objects, so that's a quantum theory but not as fundamental as QFT.   It's still not an oscillation in the electric field.

So can both  massless and massive particles be modeled as excitations of their respective fields?

   In QFT, yes.....   I can't say much more without going really long.

    I should also make it clear that QFT doesn't have a field for every massive object in the world.   Neutrons, house bricks and Aunt Jane don't have their own field.    Only the fundamental particles that appear in the standard model of particle physics have their own field.

---  That's already too long, I'm not even going to do the second post you've written. ---

Best Wishes.

[evan_au]

And what about the electron?Is it just an excitation  in the electric field?

The electron carries an electric field (so does the proton and other particles).
- So the presence of a charged particle modifies the electric field
- When an electron and proton interact, they can produce a photon, which is an excitation of the electromagnetic field, and propagates away at the speed of light
- However, the proton and electron continue to impact the electromagnetic field in their original location (with a small momentum balancing that of the photon)

So there is a separate electron field, and excitations of the electron field represent an electron.
- The electron has rest mass, so excitations of the electron field cannot propagate at c
https://www.damtp.cam.ac.uk/user/tong/whatisqft.html

Oops: My mostly-classical response overlapped with the erudite QFT response from Eternal Student...

[geordief (OP)]

Much appreciated @evan_au  and @Eternal Student
Whilst my ambition  to learn many  things in this subject is very low I do welcome the prospect of hopefully   not making the exact same mistakes in my questions in the future (although doubtless I will) as well as learning one or two things I am not likely to forget.

And let us hope that others can also learn something from your answers.

[evan_au]

Some background on the electromagnetic field:
- Maxwell developed the equations which describe the electromagnetic field, and also light as transverse electromagnetic waves propagating in this electromagnetic field. You could call this a "classical" theory, a 3D analogy to transverse waves propagating in a 1D guitar string.
- There had been notions about light as particles, but it wasn't until Einstein's analysis of the Photoelectric effect that it was confirmed that light travels in "quanta" of fixed energy for their frequency. This was a quantum theory of light.
- Put these two together, and you have a semi-classical theory with wavicles of light (photons) propagating through the electromagnetic field.

Reading the QFT answer from ES, it seems that this semi-classical theory of photons and the electromagnetic field is an emergent phenomena from the more detailed behaviour described in QFT(?).

[Eternal Student]

Hi.

Reading the QFT answer from ES, it seems that this semi-classical theory of photons and the electromagnetic field is an emergent phenomena from the more detailed behaviour described in QFT(?).

    Yes that's exactly the sort of thing I was saying.
     However, historically Quantum Field theories were not developed this way around.  For example, QED (Quantum Electrodynamics) was developed before the more complete QFT appeared.   There were various attempts to quantise some classical fields like the electric and magnetic fields and many of these quantum field theories are still in use.  As such you will find the phrase "Quantum Field Theory" being used to describe many different things.
    The QFT I was describing is the one associated with the standard model of particle physics.    There are underlying fields only for the particles of the standard model,  while forces like the weak force or the electromagnetic force are considered as "fundamental interactions" involving an exchange of a force carrier.    From such interactions classical electromagnetism results like a Coulomb potential for the E field,   V = Q/4πεr  can be recovered.   As such you have an Electric field that emerges.

      This is one online reference where someone asked about this:
https://physics.stackexchange.com/questions/142159/deriving-the-coulomb-force-equation-from-the-idea-of-photon-exchange
 
It's complicated but I can't find an easy to read or PopSci article that will cover it at the moment.

Best Wishes.

[Zer0]

May i ask a follow up Question?

[geordief (OP)]

May i ask a follow up Question

No objection on my part,but set your rubbish filter to high if I try to answer it ;-)

[Zer0]

May i ask a follow up Question

No objection on my part,but set your rubbish filter to high if I try to answer it ;-)

Why, Thank You!
: )

Thou i Doubt anyone would attempt to answer Considering my query is a Load full of BS!
(activate ur anti-crap defense shields Right Now)

Whenever i Think/Imagine Quantum Fields...
I see a 3d fishing net permeating in Space.
Is that the Right way to picture it?
Or QFs are just purely Mathematical constructs which look good & feel right only on paper?

Also, can Any of these QFs expand or contract?
With expansion do they dilute, disperse, or fade away?
Or with contraction get denser, heavier, stronger?
Can We manipulate or control them?
Can they be torn apart?

(short n simple responses expected)

[geordief (OP)]

May i ask a follow up Question

No objection on my part,but set your rubbish filter to high if I try to answer it ;-)

Why, Thank You!
: )

Thou i Doubt anyone would attempt to answer Considering my query is a Load full of BS!
(activate ur anti-crap defense shields Right Now)

Whenever i Think/Imagine Quantum Fields...
I see a 3d fishing net permeating in Space.
Is that the Right way to picture it?
Or QFs are just purely Mathematical constructs which look good & feel right only on paper?

Also, can Any of these QFs expand or contract?
With expansion do they dilute, disperse, or fade away?
Or with contraction get denser, heavier, stronger?
Can We manipulate or control them?
Can they be torn apart?

(short n simple responses expected)

I won't attempt to answer but you are welcome to look at my other ongoing  and perhaps similar thread on another  forum  where others will probably  weigh in in due course

https://www.scienceforums.net/topic/131347-fields-as-understood-in-qft/#comment-1237721

[Eternal Student]

Hi.

Whenever i Think/Imagine Quantum Fields...
I see a 3d fishing net permeating in Space.

    Many videos and diagrams do end with something like you've described.  If it's just for yourself and your own interest, why not visualise it however you find it helps.  Just be cautious not to assume something must be exactly as we have chosen to picture it.

Or QFs are just purely Mathematical constructs which look good & feel right only on paper?

     I really wouldn't know if they feel right or look right.   They are not always elegant, numerical approximations are often used.    If you translate   English <-->  Pure mathematics      you'll find that   "numerical approximations"  translates as "ugly piece of stuff".

Also, can Any of these QFs expand or contract?
With expansion do they dilute, disperse, or fade away?
Or with contraction get denser, heavier, stronger?
Can We manipulate or control them?
Can they be torn apart?

     Some of these questions are just a consequence of visualising something and allowing that to imply some physical aspect of a field that it may not have.
   With expansion, do they dilute?   I don't know.   General Relativity isn't built in to the model.   We can wave our hands a bit and link to other models about what might happen.   Theories (which have very limited connection with QFT) suggest the expansion of the universe could result in all particles eventually decaying into photons of low energy.   On the face of it then, this makes most of the fundamental particle fields very quiet.   The fields should still exist everywhere through space they just have very low values (or magnitudes for vector quantities or some equivalent for tensor fields).
    Can we manipulate or control them?   When you walk from one room to another you have manipulated millions of particles and made use of numerous fields but it just looked like you were walking from one room to another.  None the less I would say you had a considerable amount of control and were able to act so as to make some fields behave a certain way.   Well done, you're a skilled field manipulator.
     Can they be torn apart?  I don't know.  I don't think of a field as material that can be torn.

Best Wishes.

[Zer0]

Hmm...so a Simple act of switching On an electrical bulb is in a way manipulating/fidgeting with the EM field?

Making a Hot cuppa coffee is modifying/changing the Electron Field?

Umm...What about the Higgs Field?
Walking, running or head bopping Affects it or Not?

Higgs came into Effect before atoms, protons, neutrons, electrons Right?
Even before Quarks?
What then happens to the Higgs Field after an upper limit of Entropy is hit?
HF Disappears?
Or Remains?
It surely must be Expanding along with the Universe, Right?
(won't ask what would have happened to the HF if the Universe was Collapsing/Crunching lol)

(Appreciate the Short & Simple responses Received)
Great Work!

[Zer0]

Thanx for that Link G!

I read pretty much All of it, won't say i Understood it all.

I've obtained another doubt from it thou lol.

Why is a UFT required?
& If it's so Essential, Why not keep GR & QM aside, n come up with something Different/something New?

(square peg in a round hole = M Theory?)

[geordief (OP)]

Thanx for that Link G!

I read pretty much All of it, won't say i Understood it all.

I've obtained another doubt from it thou lol.

Why is a UFT required?

I don't know  and others will give you a better answer but I suspect a ToE (what you mean by UFT I think) is necessary to understand the conditions  even earlier in the life of the universe than we do already.

But don't take my opinion for it as I  only.listen to what more knowledgeable  people have to say on the subject.

[Eternal Student]

Hi.

Umm...What about the Higgs Field?
Walking, running or head bopping Affects it or Not?

    It depends how you wish to consider the term "manipulating".   I would say yes, you are using it.   To achieve the things you are talking about (Walking and head bopping) some particles had to have the property of mass, which was obtained through an interaction with the Higgs field.
    Just to be clear:  I would say that we (human beings) can manipulate fire.   We can make fire spread to somewhere we want it, we can use it, we can start a fire and we can put one out.    This is some control and manipulation of fire.   It doesn't usually look like waving your hands in the air like a wizard or doing something to please the god of fire.   It just involves putting the right things together and taking the right actions.    That is what you are doing when you walk somewhere, you are using the properties that the fields have.  I would say this is some control and manipulation of the fields.   However you can't choose to make the fields behave in a way that they don't usually do,   just as you can't choose to make fire behave in a way that it usually doesn't.   All you are doing is using the interactions and behaviours that they do have.

What then happens to the Higgs Field after an upper limit of Entropy is hit?
HF Disappears?
Or Remains?
It surely must be Expanding along with the Universe, Right?

   I don't know - but thinking of a field as something that can just stop existing probably isn't the best picture to have.     
Fields should be something which exist and have some value (maybe a scalar value but maybe a vector or spinor etc.) at every point in space and time.  They shouldn't disappear but they can become low valued or might even be 0 valued everywhere after some time (some fields won't or can't drop to 0 energy, they have a minimum energy > 0).   If something makes no contribution to any physics then I suppose it's just philosophy or personal choice to decide whether they still exist or not.   I would choose to assume they continue to exist but just have low or 0 value.
    Fields which do have a minimum or zero-point energy will always make some contribution, for example they should contribute to the energy density of space and should be part of the "dark energy" which is important for determining the curvature of space and its eventual fate (e.g. continued expansion or eventual colapse).

Best Wishes.

[Zer0]

Thanks to All!

This Thread now has more information & details & explanations than the QFT page on Wiki.

Good Job!