Photon Spin: 1 vs 2 - Answers for Alex

[afcarval]

Dear all,

Can you please enlighten me about the spin of photons?

How can you tell if it is spin 1 or 2 ?

Thanks,
Alex

 

[ansgar]

1 since it transforms as a vector under lorentz transformations (or rather the four potential transforms as a vector)

 

[afcarval]

Dear ansgar,

Can you explain the detection and nature of the four potential?

"it" is the "four potential" that transforms as vector under Lorentz transformations?

The spin is 1 because the vector is a tensor of order 1?

Thanks,
Alex

 

[ansgar]

Dear ansgar,

Can you explain the detection and nature of the four potential?

"it" is the "four potential" that transforms as vector under Lorentz transformations?

The spin is 1 because the vector is a tensor of order 1?

Thanks,
Alex

yes vector = tensor rank 1

http://en.wikipedia.org/wiki/Electromagnetic_four-potential

Use google mate

 

[afcarval]

Dear ansgar,

Thank you for your reply.

What kind of tensor of rank 2 can you expect after a Lorentz transformation?

Is the "four-potential" enough to describe the signals detected?

cheers mate,
Alex

 

[sheaf]

Is the "four-potential" enough to describe the signals detected?

Assuming by "the signals" you mean the electric and magnetic fields, then it's more than enough (gauge freedom).

 

[afcarval]

Dear sheaf,

Thank you for your kind reply.
So the "four-potential" detects electric and magnetic fields.
The matrix consider the electric and magnetic fields has independent signals?
Is the magnetic field independent of the magnetic field?

Cheers,
Alex

 

[ansgar]

you mean

Is the ELECTRIC field independent of the magnetic field?

no you can see that from the very definition of E and B ...

 

[afcarval]

Dear ansgar,

yes, I meant: Is the electric field independent of the magnetic field?
thank you!

cheers mate,
Alex

 

[Vanadium 50]

Afcarval, what's your background in physics. I get the impression that these answers aren't pitched at the level you're expecting.

 

[afcarval]

Dear Vanadium 50,

In my degree I had some physics, in my master too and in my PhD also... but not specific in physics. Only a course in Quantum Monte Carlo...

I had no expection about this forum pitch.

My basic question: can you detect one photon with spin 2? Why?

Thanks!
Alex

 

[ansgar]

Dear Vanadium 50,

In my degree I had some physics, in my master too and in my PhD also... but not specific in physics. Only a course in Quantum Monte Carlo...

I had no expection about this forum pitch.

My basic question: can you detect one photon with spin 2? Why?

Thanks!
Alex

there is no such thing so how can you detect it?

 

[afcarval]

Dear ansgar,

So you are telling me that by definition is not a photon?

But can you model the response in order to have a photon with spin 2?

Another way to put the question. Can you have a particule with spin 2 without electromagnetic perturbation?

Why?

Thanks,
Alex

 

[ansgar]

you can detect photons with a combined angular momentum and spin and parity as you want, that is just the multipole expansion..

 

[afcarval]

Dear ansgar,

Can you explain better?

You are telling me that: if you want, you can detect a spin 2 for photons?

Thanks,
Alex

 

[ansgar]

you have not defined properly what you mean with all of this. photons can have angular momentum J which is the sum of L and S

I can not explain better since what you really need is to define what and why you are asking this for and a couple of textbooks

 

[afcarval]

Dear ansgar,

Thank you for your kind reply.

One last question.
In the detector and in the signal analysis can you tell the difference between a photon with spin 2 and a graviton?

Cheers mate,
Alex

 

[ansgar]

I kknow that there was some mumbo jumob behind all of this

gravitions does not interact electromagnetically

I am not your mate

 

[afcarval]

Dear ansgar,

Mumbo jumob? They are simple questions...

The question:
Can you really have a particule with spin 2 without electromagnetic perturbation?
Can you explain why?

Or are they dogmas?

Can I google it?

cheers mate,
Alex

 

[twofish-quant]

Can you really have a particule with spin 2 without electromagnetic perturbation?

It seems that at some level you can model gravitons seem to be modeled by spin 2 particles.

Can you explain why?

Not really.

Or are they dogmas?

Observations. Some particles we see existing. Some particles we don't.

 

[afcarval]

Dear Twofish-quant,

Thank you for your kind reply.

Unfortunately I can not understand:
"It seems that at some level you can model gravitons seem to be modeled by spin 2 particles."

Can you explain? please.

Thanks,
Alex

 

[ansgar]

Dear ansgar,

Mumbo jumob? They are simple questions...

The question:
Can you really have a particule with spin 2 without electromagnetic perturbation?
Can you explain why?

Or are they dogmas?

Can I google it?

cheers mate,
Alex

PARTICLES

yes of course you can, just propose a tensor field of rank 2 and quantize it

 

[afcarval]

Dear ansgar,

Thank you for your reply.

Dirac did propose something like that...

But then you have the other question.

If you want, can you detect a "defined" photon with spin 2?

Thanks,
Alex

 

[ansgar]

Dear ansgar,

Thank you for your reply.

Dirac did propose something like that...

But then you have the other question.

If you want, can you detect a "defined" photon with spin 2?

Thanks,
Alex

defined photon.. what?

 

[afcarval]

Dear ansgar,

0k, fair enough.

Can I rephrase?

If you want, can you detect a bosonic particle with spin 2?

Thanks,
Alex

 

[ansgar]

a spin 2 particle IS a boson

are you still talking about intrinsic angular momentum?

 

[diggy]

Some additional information... Angular momentum in photons was discovered in the 1930's by Beth. After that selection rules in atomic transitions showed what the allowed angular momentum of photons were. Those should both be pretty google-able if you don't have texts in front of you.

 

[afcarval]

Dear all,

Thank you for your kind replies.

Spin 1 is 1 by definition of the unit.

All the best wishes,
Alex

 

[chrispb]

I believe someone told me once that if there exists an elementary/fundamental spin 2 particle, it must be a graviton.

 

[diazona]

Bottom line, on both experimental and theoretical grounds, photons have spin 1. Anything that has a spin other than 1 cannot be a photon.

 

[afcarval]

The hypothesis is the change caused by interference in the absorption of photons ...
Spin 2?

 

[Bill_K]

afcarval,

Evidence that photons have spin 1 comes from the nature of electromagnetic waves. EM waves have a linear polarization, and their effects can described by a vector E perpendicular to the wave. Regarding the source, they can be emitted from a dipole antenna. All of these are characteristic of a spin-1 particle.

By contrast, gravitons (assuming they exist) are spin 2 particles. Gravitational waves would have a much different character. Instead of a transverse vector E they would need to be described by a transverse shear tensor. That is, alternate stretching and compression in both directions perpendicular to the wave. Likewise, the source of the wave would need to be quadrupole. Spin 2 waves could not be emitted by a dipole antenna, since they are quadrupole in nature.