Photons are said to be the electromagnetic force carries. But I have a hard time imagining photons being the particles that carries a force between negative and positive charges. Everytime I hear about photons, they are described as light particles. So is there some other type of electromagnetic force-carrier particle that acts between two charges? I've heard that there are 8 different types of strong nuclear force carries and 3 different kinds of weak nuclear force carries.

Saith,

Electromagnetic photons have oscillating electric and magnetic fields. They are emitted by electrons at certain frequencies that are related to their energies.

The particles that are responsible for static electric and magnetic fields may not be photons at all. Although, the scientific community calls these particles "virtual photons", nobody really knows what static fields (electric and magnetic) are composed of.

It is my opinion that the static electric field of an electron is not the result of an emmision of particles from the electron, but that it is actually an extension of the electron itself. In other words, I believe that an electric field is a "less dense" part of the electron.

Tom

Saith

There are four known force carriers, the photon; carrier of the electromagnetic force, the gluon; carrier of the strong force, and the electroweak bosons (W and Z). The graviton is theoriezed as the carrier of gravity however, it has not been detected.

So far, I think that's about it for force carriers.

Wouldn't W+, W-, and Z be considered three particles? Since particles with a different charge are considered to be different particles, like the electron and posititron or up and down quark. And gluons can carry three different kinds of colour charge. I ask because I heard that there are 48 quantum particles. And I only came up with 28.

Also, don't the pions take part in mediating the strong nuclear force between baryons? I have a lot easier time understanding fundamental bosons rather than the composite ones. Are all bosons considered force carriers?

There seems to be very little information on new theories and the observations that the theories were based on. For example, what observation gave the conclusion that light comes in packets, or electrons have set energy levels.

Does anyone know how someone would measure the wavelength and amplitude of a photon?

Has any expirement seen the effects of an incomplete photon (that is one that never completely reached the end of its wave, which is to say one that maybe had a positive flux for so long, then had a negative flux for so long, but stopped before it got back to zero)?

Has any experiment shown that it is possible for a photon to have an incomplete cycle?

For anyone that doesn't know what i mean by flux, here is the explanation: a flux is a change. A photon goes through a change from being positive, then changes negative, then goes back to 0. In this way a photon is neutral, beacuse the chages cancel out, much like in an atom.

These questions are hard to find answers to im sure, but it would be great if a couple could be answered.

Frencheneesz

There seems to be very little information on new theories and the observations that the theories were based on. For example, what observation gave the conclusion that light comes in packets,


The photoelectric effect (Einstein).


or electrons have set energy levels.


Cavity radiation (Planck).


Does anyone know how someone would measure the wavelength and amplitude of a photon?


As for wavelength, very often you know the energy of the photon (if you are generating the photons). E=hc/(lambda), where (lambda) is the wavelength.

As for amplitude, that is not a property of individual photons, only of classical EM waves (which are composed of trillions of photons).


Has any expirement seen the effects of an incomplete photon (that is one that never completely reached the end of its wave, which is to say one that maybe had a positive flux for so long, then had a negative flux for so long, but stopped before it got back to zero)?
Has any experiment shown that it is possible for a photon to have an incomplete cycle?


Photons do not have cycles like EM waves have. The closest analogy I can think of is...
water waves:water molecules::EM waves: photons


For anyone that doesn't know what i mean by flux, here is the explanation: a flux is a change. A photon goes through a change from being positive, then changes negative, then goes back to 0. In this way a photon is neutral, beacuse the chages cancel out, much like in an atom.


There is no experimental justification for that model of a photon.


These questions are hard to find answers to im sure, but it would be great if a couple could be answered.


It's not as hard as you think--there's free physics stuff everywhere online.

Start by digging around here:
http://web.mit.edu/redingtn/www/netadv/welcome.html

Tom

Tom

Why did Einstein choose to define the universe in terms of three spatial and one time dimension instead of four spatial dimensions?

Jeff

<a href=http://home.attbi.com/~jeffocal/shadows.htm> Shadows </a>

jeffocal,

Why did Einstein choose to define the universe in terms of three spatial and one time dimension instead of four spatial dimensions?

Cause he was an idiot. :)

Oh....I'm sorry. You must have been asking the other Tom.


Tom

I think Albert did so because it is coherent with our perceptions. Why did he not define the universe in terms of 431 spatial, 56 temporal, 123 temporary, 12 weird and 1 totally-uncomprehensible dimension?

The reason I asked is because if one transposes Einstein’s space time equations that were derived in terms of velocity and time into four spatial dimensions in terms of momentum and energy wouldn’t they be more compatible with the energy and moment equations of Quantum mechanics.

Merlijn

Do you think this would make it possible for one to directly compare the relativistic solutions regarding the force of gravity to quantum mechanical solution regarding the quantum nature of mass and energy?

Jeff

http://home.attbi.com/~jeffocal/shadows.htm

Originally posted by jeffocal
Why did Einstein choose to define the universe in terms of three spatial and one time dimension instead of four spatial dimensions?


Well, I've never asked him :) , but I imagine it is because the spacetime coordinates of an event are uniquely specified by those 4 coordinates.

Originally posted by Prosoothus
Cause he was an idiot. :)


You mean you have a theory that requires more than 4 paramaters to specify an event??? :bugeye:

I thought you were all about economy, Tom! :)

Sincerely,
"The other" Tom :)

What i meant by having little information on new theories and the observations they are based on, is that i can't FIND them.

Like they have to be published SOMEWHERE i know, i just can't find them.

Well i was kind of going for explanations of the observations instead of sitations, but thats ok.

I kind of had the mind that the theory on light is that photons are that the photons DO osscilate (sp error sorry)... eh whatever.

the thing is i am trying to learn about light so i can make my own theory. I have a very simplistic theory that just takes into account forces and the particles associated with those forces. So far I have been able to explain many many things from this simple point of view, from the reason why evaporation cools things to heat and pressure to why matter changes states to brownian motion to why plasma happens.

Of course most of it stems from what is already taught, but it has a more easy to understand overview.

Some of the things i haven't been able to explain are anything about light, electricity, and im sure there are more things, but i can't remeber them right now.

From what I know right now, people think light comes in packets called photons. And these photons have the wave property.

I know the picture of a light wave with crests and troughs, frequencies and amplitudes are nothing but a graph of some sort of test on light. In no way am i going to believe that a light "wave" travels up and down like that.

My question is: What do the axis of the graphs mean?

As in a higher amplitude means what, and i presume that the farther along the wavelenght you go is for time?

Please explain your explanation of light with the photons that don't ocislate, because i have a very similar idea, it is just not what i've heard from "the books".

When i've heard your explanation i can discuss further.

Thanks. Frencheneesz

I found the book Q.E.D. by Richard Feynmann very insightfull! It is not too hard to read and much fun. try it.
SinceI am not a physicist, I think I am not the right person to try to explain it. The thing that I understood was, that the wave function of particles, is not so much a fysical property but more a quatum-probablility property. The state of a photon can be bescribed with a probability vector of constant legth, but with varying direction (it's 'rotating'). When two photons collide it's the sumn of the two vectors that determine the result. they extinguish each other, add up, or something in between.

Hmm
abstract
FUN!
WOW!
:D

“Well, I've never asked him , but I imagine it is because the space-time coordinates of an event are uniquely specified by those 4 coordinates.”

Tom2

Relativity attributes physical properties and causality to the dimension of time. Relativity defines the curvature of space-time as the causality of the force of gravity. However Chapter Sixteen http://home.attbi.com/~jeffocal/chapter16.htm of
Shadows defines time only in terms of the sequential ordering of the causality of events while defining the force of gravity in terms of a curvature of three dimensional space with respect to the fourth spatial dimension. Therefore, according to the shadows http://home.attbi.com/~jeffocal/shadows.htm , model time is non-physical dimension, which allows one to uniquely specify an event in four spatial dimensions.

Jeff

Tom2,

You mean you have a theory that requires more than 4 paramaters to specify an event???

I thought you were all about economy, Tom!


Let me remind you that in Einstein's curved-space model there are more parameters than four, since now you have to explain how space can curve at all. Let me also remind you that the curved-space theory is an exclusive model: it excludes other long-distance interactions such as the electromagnetic interaction.

I have a gravitational model that not only lets space remain uncurved, but also includes the electromagnetic interaction.

Tom

“I have a gravitational model that not only lets space remain incurved, but also includes the electromagnetic interaction.”

Tom

I’d be interested in reviewing this if possible. However, I disagree with you that a curved space model it excludes other long-distance interactions such as the electromagnetic interaction. The curved space mechanisms defined in shadows does explain and predict all long-range interactions including those associated with electromagnetic energy.


Jeff

Prosoothus,

The question was:

Why did Einstein choose to define the universe in terms of three spatial and one time dimension instead of four spatial dimensions?


In other words, "Why did Einstein develop a theory in which 4 parameters are required to specify a point in spacetime?"


Let me remind you that in Einstein's curved-space model there are more parameters than four,


I'm not sure, so let's count them:

x (that's one)
y (that's two)
z (that's three)
t (yay! that's four!)

Whatever other parameters you are thinking of, they are unrelated to the question at hand.

Tom

Tom2,

x (that's one)
y (that's two)
z (that's three)
t (yay! that's four!)

Let me complete your list:

Conversion of x,y,z,t from one geometry to another (that's at least five)

Tom

Jeffocal,
i was wondering if you could give us explanations here in the forum, instead of siting the shadows long and frankly hard to read paper.

Thanks.

Hey,
Since I have my theory, I was wondering if anyone would test it by asking me to explain things with my theory.
Look at the post of mine before my previous post if you don't know what im talking about.
But even if you don't know what im talking about, just ask any question you can think of that doesn't involve complicated thinking (like such a specific question like why does iron bond with air, nothing like that)

Will anyone take me up on that? Come on it'll be a challenge from people who think they know it all, and itll be a chance to improve my theory!


Frencheneesz

Frencheneesz requests:

Since I have my theory, I was wondering if anyone would test it by asking me to explain things with my theory. Look at the post of mine before my previous post if you don't know what im talking about.

What theory ? I read little more than gibberish in your post.

But even if you don't know what im talking about, just ask any question you can think of that doesn't involve complicated thinking

Why are you talking gibberish ? Oops, sorry, that may be too complicated. :D

Will anyone take me up on that? Come on it'll be a challenge from people who think they know it all, and itll be a chance to improve my theory!

Or it may be an opportunity to trash what's left of your credibility. Carry on.

Thank you Q,

You know you could be a little more serious, if you'd like to trash my credibility i'd be happy to have you try by asking me a question for my theory instead of insulting me.

Frencheneesz

French

You know you could be a little more serious, if you'd like to trash my credibility i'd be happy to have you try by asking me a question for my theory instead of insulting me.

Seriously then, what theory ?

Ok, fine

What theory you ask. Its not that complicated. Instead of having a ton of theories for science my theory tries to explain everything in terms of forces and the particles associated with those forces.

So far I have been able to explain many many things from this simple point of view, from the reason why evaporation cools things to heat and pressure to why matter changes states to brownian motion to why plasma happens.

So you can ask me to explain something like plasma or something like sound with my simplistic theory.

That is my theory, it ain't much, but if it can explain most things other models can explain then it is an excellent model in comparison because of its simplistic base theories.

Hopfully you can comprehend my gibberish and ask me a question

Come on try to rape my theory, try your hardest.

French

Instead of having a ton of theories for science my theory tries to explain everything in terms of forces and the particles associated with those forces.

The above statement is not a theory. Could you at least explain your theory.

Come on try to rape my theory, try your hardest

Provide the substance first, then we'll provide the pillage.

Fine its not a theory, but it is as much a theory as the theory of relativity. It is more a way of thinking of things.

Ill give you an example, Instead of explaining that hotter things are less dense or take up more volume, my -idea- would explain what heat is and why more of it would make a substance less dense.

That is my idea, simplifying science to the basis of forces and the particles associated with those forces.

If that is too much for you to comprehend then don't bother testing it. If you would rather think of it as testing my knowledge go ahead.

- -

French

Fine its not a theory, but it is as much a theory as the theory of relativity. It is more a way of thinking of things.

Relativity is a well defined theory backed up with mathematics and is much more than just a way of thinking of things.

Ill give you an example, Instead of explaining that hotter things are less dense or take up more volume, my -idea- would explain what heat is and why more of it would make a substance less dense.

That is my idea, simplifying science to the basis of forces and the particles associated with those forces.

You keep talking about an idea/theory, but I've yet to see anything. Forces and particles associated with those forces means nothing.

If that is too much for you to comprehend then don't bother testing it.

Provide something to comprehend, sans gibberish.

Fine Q, you don't want to listen to me, don't k?

Photons do not have cycles like EM waves have. The closest analogy I can think of is...
water waves:water molecules::EM waves: photons
Tom2, can't EM waves be preceived as traveling electromagnetical field?
(sorry if this's a stupid question)

Why did Einstein choose to define the universe in terms of three spatial and one time dimension instead of four spatial dimensions?
in my oppinion maybe because time is dependent of 3D space forming timespace. You can take all the other dimmensionns and look at them by one and measure, but to measure time, we need to have some points in 3D universe (just my weird thought)

heh Aviotar, I think it might be a stupid question, lol.

Electromagnetic wave is a traveling electromagnetic wave, the thing is people don't know exactly how it travels. As i understand it, the "wave" is that as the wave passes through a detector it has a positive charge then neutral then negative then back to neutral as time goes on. But then there are the packets of light that don't follow the idea of a -continuous- wave. And the packets of light are said not to be the carriers of normal electromagnetic waves....

"Why did Einstein choose to define the universe in terms of three spatial and one time dimension instead of four spatial dimensions?"
just my weird thought, but maybe it was a retorical question.

Frencheneesz

French

Photons have no charge. They are comprised of an electric and magnetic field.

Prosoothus sez:

Let me complete your list:

Conversion of x,y,z,t from one geometry to another (that's at least five)


For the third time, the question was:

Why did Einstein choose to define the universe in terms of three spatial and one time dimension instead of four spatial dimensions?


Your answer above is wrong. Period.

Avatar,

An EM wave is a traveling EM field, with the special condition that the E and B fields induce one another.

Q,

Photons are not comprised of any EM field. They are more fundamental than the EM field. You yourself say that the photon has no charge. How, then, can it have any kind of field? It can't.

Tom

Tom2,

Stop acting stupid.

This is your quote:

You mean you have a theory that requires more than 4 paramaters to specify an event???

Since Einstein's coordinate system can be curved, you would need MORE than just four paremeters (x,y,z,t) to specify an event. X,y,z, or t will not tell you how much space is curved, and x,y, and z are dependent on the curvature.

Jeez, why do I always have to explain everything.

Tom

Prosoothus, you could not explain your way out of a paper bag. Are you deliberately trying to obfuscate this? It seems you do that all the time. It's almost as if you don't want to learn.

"Geometry" is not a parameter needed to specify the coordinates of an event. In fact, "geometry" is not a parameter at all. The question was about why Einstein used 3 spatial dimensions and 1 time dimension. You replied, "because he was an idiot." I was prodding you for your thoughts on what you think is a better scheme. Naturally, I did not receive it from you, and I suspect that I never will.

Tom

Tom2

Photons are not comprised of any EM field. They are more fundamental than the EM field. You yourself say that the photon has no charge. How, then, can it have any kind of field? It can't.

Photons of light are quanta of mass-energy that propagate through spacetime using alternating electromagnetic fields.

http://www.starlight-pub.com/Matter/PartIII/III8Photons.html

http://www.starlight-pub.com/Matter/gifs/em_wave.jpg

Photons (electromagnetic radiation) can travel through empty space. How can this be?
The electric and magnetic fields keep each other going!

http://ethel.as.arizona.edu/~collins/astro/subjects/electromag7.html

http://ethel.as.arizona.edu/~collins/astro/subjects/img/emwavea.gif

Beautyfull, (Q), beautyful!

I like this Quick Time movie

http://www4.ncsu.edu/~rwchabay/emimovies/PlaneWave.html

stumbled on it, while searching the net

Obviously a photon is not the infinitely long EM string that an electromagnetic wave brings up the thought of, but is smaller than .... um infinite. So how long is a photon? Is it one Wavelength or is it something else?

To me a photon is very indescript and its properties not understood.

Can someone tell me why the light would seem a different color, and different brightness? What do amplitude and frequency equate to phisically?

The photons might travel at different speeds to make up different colors, but that seems improbable for the reason that you can see a far off planet and the picutre isn't warped in that way.

The photons might be more numerous to create a brighter picutre, which seems likely.

The photons could be oscilating at different electromagnetic charges, but how?

The properties of the photon are important in this discussion. So anyone have any ideas?

Oh by the way:

"Photons of light are quanta", yes photon and a quantum are synonimous

French

To me a photon is very indescript and its properties not understood.

You've made it quite clear you don't understand. Why not read the links I posted above.

The photons could be oscilating at different electromagnetic charges, but how?

It appears you're not even reading the posts. It has already been stated that photons have no charge. Please read the posts and links provided before making such comments.

There are four known force carriers, the photon; carrier of the electromagnetic force, the gluon; carrier of the strong force, and the electroweak bosons (W and Z). The graviton is theoriezed as the carrier of gravity however, it has not been detected. So far, I think that's about it for force carriers.

why do you pretend to know what you're talking about?

don't listen to Q
he's obviosly not a physicist
just go to this link:

http://physics.hallym.ac.kr/education/lecture/netadv/qcd.html




I found the book Q.E.D. by Richard Feynmann very insightfull! It is not too hard to read and much fun. try it.

Since I am not a physicist, I think I am not the right person to try to explain it.

Then you shouldn't be giving advice in a physics topic
go make some posts in philosophy where it's safe to be ignorant
of the facts

you're advice is terrible

photon girl

Hi ultravioletten. :D

(Q),

That "Unit Particle Substructure Theory" looks like a crackpot site to me. What are the positive and negative parts of the photons? "Negative" and "positive" what, exactly?

Also, the second link you posted uses macroscopic (ie-classical) experiments to demonstrate EM phenomena. Those demonstrations do not reveal the photon nature of the EM field at all.

I completely agree that for the high Fock states Maxwell's equations describe traveling EM waves (by mutual induction) very well. But this description breaks down completely when there are just a few photons.

You have only to look at a basic introduction to QED to see this. Try Chapter 2 of Advanced Quantum Mechanics by Sakurai. It is a clear derivation of the quantization of the EM vector potential.

Photon Girl,

The link you posted to the Net Advance of Physics pertain to QCD (the theory of quarks and gluons). You want the link to QED (the theory of photons and charged particles).

Tom

photon girl,


quote:
--------------------------------------------------------------------------------
I found the book Q.E.D. by Richard Feynmann very insightfull! It is not too hard to read and much fun. try it.

Since I am not a physicist, I think I am not the right person to try to explain it.
--------------------------------------------------------------------------------



Then you shouldn't be giving advice in a physics topic
go make some posts in philosophy where it's safe to be ignorant
of the facts

you're advice is terrible
Hahahaha. Why not be an ass when there's an opportunity, right?
At least I am honest enough to tell I have only limited knowledge of these matters. If you think you can lecture me, first prove yourself.

Please be sure to make clear who you're quoting.... I wanted credit for it.
BTW. I was the first to write "terrible" as a comment. It was a comment to a copied piece posted by ultravioletten.
.... maybe (Q) is right - as always. :D

photon girl,
It is a strange thing that in your four posts (until now: 31-08-2002 23:55 CET) you have done nothing but try to insult (Q) en me(rlijn).
Odd enough, the very same persons to have commented to the copy-paste posts of ultravioletten.

You know what Q, just stop insulting me and start giving out facts, ideas, and evidence.

I guarrantee to you that people do not fully understand light, photons, or electromagnetism. THIS MEAN THAT NOONE understands. Get it?

Just becuase it has been "stated' does not mean its fact. I can give you a very good reason photons are "stated" to be neutral. This is because they oscillate as much positively as negatively. Thus when you look at it, on average photons are negative.

This is the same for an atom. Obviously electrons and protons are opposite charges. But the atom is said to be neutral. Of course if it were neutral COMPLETELY then your hand would not be repelled when you touch a piece of glass, your hand would go right though it.

Give some ideas, not links, not put downs, but actual STUFF.


Photon girl... (sigh),
your critisism is without base, i can't take your word for it, so ill have to find out for myself (and i have).

Tom2':

"What are the positive and negative parts of the photons? "Negative" and "positive" what, exactly?"

negative and positive electro-magnitic charges, exactly.

"Also, the second link you posted uses macroscopic (ie-classical) experiments to demonstrate EM phenomena.Those demonstrations do not reveal the photon nature of the EM field at all."

I have to agree with you. The experiment with the radio in a can thing was complete crap. Sound comes through because your pump sucks (ie not all the air is out). Photons usually do not create sound :D

"If you think you can lecture me, first prove yourself." merlijn

I agree! If all you do is critisize, your going to look like an idiot (hint, hint).

"maybe (Q) is right - as always"

hmm, i haven't seen much more than critisism and a couple links come out of him either.....

Tom2: "What are the positive and negative parts of the photons? "Negative" and "positive" what, exactly?"

Frencheneesz: negative and positive electro-magnitic charges, exactly.

In that case, the model is wrong. If photons were composed of pairs of charges, then we would observe all kinds of effects that have never been found.

Off the top of my head, I can think of these:

1. The charge distribution could be polarized.
2. The charge distribution could be excited and de-excited, to produce photons in all directions.
3. Photons would be massive (unless one postulates massless charge carriers to be the photon constituents).

If someone wishes to pursue this model seriously, he should be aware that it is a competitor with QED as the description of photon-charge interactions, and that he has a lot of work cut out for him. QED predictions are accurate to at least 12 decimal places, making it the most accurate scientific theory ever devised. Hand-waving arguments by amateurs in a science forum won't cut it.

Tom

Tom2

Because it carries light, a photon contains vibrating electric and magnetic fields.

http://www.aip.org/physnews/graphics/html/photon.htm

In a sense, the Schrodinger wave of a photon corresponds to the electro-magnetic wave of light, and this wave is governed by Maxwell's equations, which tell us that the electric and magnetic fields oscillate transversely in the plane normal to the direction of motion (and perpendicular to each other)

http://www.mathpages.com/rr/s9-04/9-04.htm

In 1864 James Clerk Maxwell discovered that, light was consisted of electromagnetic waves. He offered; light was made up of a changing electric field, E, and a changing magnetic field, B, which was perpendicular to the electric field.

http://library.thinkquest.org/16468/quan-a1.htm

From what I've read of your posts so far, I'm rather surprised you don't know what comprises a photon. This is first year basic stuff. I was almost sure you were well beyond that stage.

French

This is because they oscillate as much positively as negatively. Thus when you look at it, on average photons are negative.

Photons have zero mass and zero charge and interact with objects that have electric charge.

Give some ideas, not links, not put downs, but actual STUFF.

I always do just that. And if I grate on your nerves somewhat, please feel free to thank me. :D

(Q) sez:
Because it carries light, a photon contains vibrating electric and magnetic fields.

http://www.aip.org/physnews/graphics/html/photon.htm


Q, that is just a pop-science rendition of a "photon". If you look at that book I recommended or the following link (particularly chapter 4):

http://www.pact.cpes.sussex.ac.uk/users/markh/RQF1/rqf1.pdf

you'll see what I mean.

Our understanding of the nature of photons comes out of experimentally verified mathematical formalisms, not AIP publicity webpages.


In a sense, the Schrodinger wave of a photon corresponds to the electro-magnetic wave of light, and this wave is governed by Maxwell's equations, which tell us that the electric and magnetic fields oscillate transversely in the plane normal to the direction of motion (and perpendicular to each other)

http://www.mathpages.com/rr/s9-04/9-04.htm


Even this website says "In a sense...", which is to be read as, "I'm going to wave my hands now."


In 1864 James Clerk Maxwell discovered that, light was consisted of electromagnetic waves. He offered; light was made up of a changing electric field, E, and a changing magnetic field, B, which was perpendicular to the electric field.

http://library.thinkquest.org/16468/quan-a1.htm


Now you're talking about classical EM fields. I already said I agree that the mutual induction of Maxwellian electrodynamics is valid for high Fock states (high-n eigenstates of the photon number operator). Again, see chapter 4 ("Canonical Quantization") of that link above. The single-photon state simply does not satisfy the classical EM wave equation, no matter how much you would like it to. Therefore, photons do not "have" electric and magnetic fields. To the contrary, it is the other way around: Electromagnetic fields have photons.


From what I've read of your posts so far, I'm rather surprised you don't know what comprises a photon. This is first year basic stuff. I was almost sure you were well beyond that stage.


I am well beyond that stage. I am a 4th year PhD student in theoretical physics. The problem here is that you are taking the "first year basic" explanation way too literally.

Tom

Tom2

Q, that is just a pop-science rendition of a "photon". If you look at that book I recommended or the following link (particularly chapter 4): ... you'll see what I mean.

Thanks for the link. Some of the math here is a little beyond me. Could you please explain (4.84 - 4.86) which introduces the properties of polarization vectors leading to this statement:

Thus each polarisation behaves like an independent scalar field.

The single-photon state simply does not satisfy the classical EM wave equation, no matter how much you would like it to. Therefore, photons do not "have" electric and magnetic fields. To the contrary, it is the other way around: Electromagnetic fields have photons.

Quoted from your link:

The quantised states of the electromagnetic field are of course the particles known as photons.

I don't see anything beyond this statement explaining the single state of the photon, did I miss something ?

I am well beyond that stage. I am a 4th year PhD student in theoretical physics. The problem here is that you are taking the "first year basic" explanation way too literally.

Perhaps this is one of semantics. I am talking about light in general terms and should not be concentrating on the single state of a photon. You've cleared that up for me, thanks. I would be pleased to hear your explanation for the single state of a photon.

I would also like to mention that sciforums is more or less "pop-science" and that few, if any, have attained 4th year PhD theoretical physics. Much of what you will learn is well beyond the understanding of most, myself included. That said, I would of course, like to hear more from your area of expertice as long as you're willing to answer the questions.

(Q) sez:
Thanks for the link. Some of the math here is a little beyond me. Could you please explain (4.84 - 4.86) which introduces the properties of polarization vectors leading to this statement:


Sure.

Start with the first relation of 4.84. This simply says that the momentum vector is orthogonal to both of the polarization vectors (ie-their dot product is zero). The index ‘i’ runs through x,y,z and the index ‘l’ runs through 1,2 (both of the polarization states). The second relation of 4.84 says that the polarization states are orthonormal to each other. That is, their dot product is zero if l and l’ are not the same, and one if they are.

Equation 4.85 is, as advertised, the completeness relation for the orthonormal basis, and it is derived from the earlier equations. Completeness is required of a set of basis vectors because it is the set of vectors from which any arbitrary vector is built up. Also, that completeness relation is exploited in calculations all the time.

Equation 4.86 is the very statement of canonical quantization. a is the annihilation operator, and a* is the creation operator (For simplicity of typing, I am sticking with monochromatic photons and a single polarization state). For eigenstates |n> of the number operator N=a*a, it can be shown that the operators have the following effect:

a*|n>=(n+1)^1/2|n+1>
a|n>=n^1/2|n-1>

Thus, ‘a*’ “creates” one photon, and ‘a’ “annihiliates” one photon. In the quantum theory of radiation, a and a* take the place of the single-mode coefficients in the vector potential A (see 4.83), and the EM field becomes an operator, not just a real-valued vector function.


Thus each polarisation behaves like an independent scalar field.


I will have to think about this statement a little bit. Each polarization is quite clearly a 3-vector in Euclidean space. However, there is a sense in which the polarization is a “scalar” (=”invariant”), because you can never overtake a photon to see its polarization “flip”.





Quoted from your link:

The quantised states of the electromagnetic field are of course the particles known as photons.

I don't see anything beyond this statement explaining the single state of the photon, did I miss something ?


His notation is a bit different from mine. I say that the single photon state is represented by |n> with n=1. He says (up around equation 4.53) that it is |k’>. Just a different convention.


Perhaps this is one of semantics. I am talking about light in general terms and should not be concentrating on the single state of a photon. You've cleared that up for me, thanks. I would be pleased to hear your explanation for the single state of a photon.


A couple of remarks:

First, this topic is about the electromagnetic field carrier. The most dominant contributions to the interaction are indeed the single photon states, so that is what the discussion should be focused on.

Second, the notes I linked you to are incomplete, but if they were you would see the following commutation relation:
[Ex(x,t),By(x’,t)]=ic(hbar)(d/dz)d3(x-x’)
for (x-x’)2-(1/c2)(t-t’)2<0.

The important thing about this is that the commutator does not vanish. That means that you cannot determine both Ex and By simultaneously, making the graph you posted meaningless at the quantum level. It’s definitely not just semantics!


I would also like to mention that sciforums is more or less "pop-science" and that few, if any, have attained 4th year PhD theoretical physics. Much of what you will learn is well beyond the understanding of most, myself included. That said, I would of course, like to hear more from your area of expertice as long as you're willing to answer the questions.


Sure, I would be willing to do that. It just so happens that starting tomorrow, I will be conducting an online discussion of the following book:
http://xxx.lanl.gov/PS_cache/hep-th/pdf/9912/9912205.pdf

at http://www.physicsforums.com. The link to the thread is:
http://www.physicsforums.com/topic.asp?TOPIC_ID=5584&whichpage=1&ARCHIVE=

You’re welcome to join us. Not that I’m trying to steal members away from this forum, but we have 7 people ready to take part over there, and I don’t want to have to type out all that discussion twice. Also, besides me, there are two professional physicists, one guy with a BS in physics, and two physics undergrads, plus a curious laywoman who has studied some physics. I think you would benefit from their counsel and questions.

Tom

Tom2

The statement:

Thus each polarisation behaves like an independent scalar field.

You said:

I will have to think about this statement a little bit. Each polarization is quite clearly a 3-vector in Euclidean space. However, there is a sense in which the polarization is a “scalar” (=”invariant”), because you can never overtake a photon to see its polarization “flip”.

Along with your statement:

I say that the single photon state is represented by |n> with n=1. He says (up around equation 4.53) that it is |k’>. Just a different convention.

We get:

The two polarisation vectors form an orthonormal basis for 3-vectors.

Your additional:

The important thing about this is that the commutator does not vanish. That means that you cannot determine both Ex and By simultaneously, making the graph you posted meaningless at the quantum level.

Now it makes sense. Thanks.

You’re welcome to join us.... I think you would benefit from their counsel and questions.

I agree. I'll do what I can however, I cannot commit to fultime involvement and will most likely be relegated to the sideline.

(Q),

FYI, here is Part 2 of Prof. Hindmarsh's notes:
http://www.pact.cpes.sussex.ac.uk/users/markh/RQF2

Here are some other, more complete sets of notes:
http://www.pt.tu-clausthal.de/~aswl/scripts/qft.html (you’ll need Ghostview for this one)
http://www.desy.de/~wittig/ral.pdf
http://www.lorentz.leidenuniv.nl/vanbaal/FT/lect.pdf
http://www.lorentz.leidenuniv.nl/vanbaal/FT/prob.pdf

Tom

oops, crap.

I just realized something I said was mistyped.

I said: "This is because they oscillate as much positively as negatively. Thus when you look at it, on average photons are negative. "

I MEANT, on average photons are neutral. NEUTRAL, dah. there you go.

"since now you have to explain how space can curve at all."
what i understand from cosmology on this subject is that we're kinda floating on the edge of space and that space is curved or "wrinkled". and what i understand about electromagnatism and virtual photon exchange is that an electron will emit and absorb virtual photons. virtual photons are the biggest problem when trying to calculate the energy field of an electron. the reason is the emmision and absorbtion of virtual photons makes the energy field of an electron infinate. although, i have a good theory on grand unification and the begining universe that would describe this interaction.

"i have a good theory on grand unification and the begining universe that would describe this interaction."

Go ahead.

alright. you know how electrons will emit and absorb virtual photons right? making their energy field infinate. mabey their just sitting in an already infinate energy field produced by energy we can't "see" or detect with any method we have today. now say you where to create a "vacuum" and particals started to appear outta no where. now don't get me wrong here, there's been experiments at near absolute zero where particals do seem to appear outta nowhere inside a vacuum. what i'm saying is when you suck all the electrons out you let that energy free to do other things. if you where to recreate this reaction then you would see that the better vacuum you make, with less electrons absorbing the "energy", the more particles that would "appear" from nowhere. you would then see that this would grow exponentialy untill reaching a crest and then decreasing dramaticaly. or in other words you'ld see the spectrum of a blck body. at the crest though you'ld have an explosion of nuclear energy given off by these particles when forming. or big bang. if oyu where able to calculate how much heat and radiation where given off by each particle, then you could predict the temp of the beginning universe. these particals formed could be the "force carriers" of our every day particles and atoms and such. partical physics meets cosmology, yes some bugs to be worked out but there you go.

Originally posted by kinderharvest
alright. you know how...partical physics meets cosmology, yes some bugs to be worked out but there you go.
a) You have zero grasp of QED. Please educate yourself before opening your mouth.

b) Your spelling is atrocious -- work on it. Few people will take seriously a person who claims to have a grand unified theory, yet cannot spell "particle."

- Warren

The crackpots have teeth!

<font color="red">Removed by moderator due to excessive profanity.</font>

- Warren

chroot, it's **** in the world like you and photon girl that are the crackpots. why do you find it necessary to critisize others for their original ideas while you have none of your own? **** wake up. the world doesn't revolve around you. if your such an expert then explain the whole existance of man. who said you had to spell to be smarter then the unimaginative like you. if so then einstine should have been shot, niels bohr banned from doing any science and all the other great scientist that couldn't write. .

<font color="red">Moderator edit: Swearing adds nothing to the discussion.</font>

This will be my last response to you before putting you on my ignore list, but I just have to say it -- "einstine" was actually a fantastically skilled writer.

- Warren

kinderharvest:

Chilllllllllllllllllllllllllllll OUT. Chroot has some openmindedness problems, but you have no right to explode. You look like an idiot.

And with spelling like yours, noone will take you seriously. I read you're thing and its quite difficult to glean the word you mean. Why exactly did you say a particle would appear "out of nowhere"?

I see that chroot has the remarkable ability of bringing out the best in people. :)