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what_are_electrons

**[SOLVED] What controls/defines S=1 for Photons?**

The spin for photons is S=1 for photons, but I do not know what controls or defines that assignment. Your help will be appreciated.

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what_are_electrons

The spin for photons is S=1 for photons, but I do not know what controls or defines that assignment. Your help will be appreciated.

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Daniel.

- #3

what_are_electrons

My understanding is that a spin = 1 implies +1, 0, -1.dextercioby said:

Daniel.

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Daniel.

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yes, that is correct. However QFT shows us that the [tex]s_{z} = 0[/tex]-state corresponds to a non-physical degree of freedom. Such photons will exhibit a negative probability-distribution. The reason for these troubles are the fact that a photon has zero-restmass.what_are_electrons said:My understanding is that a spin = 1 implies +1, 0, -1.

Virtual photons however can exhibit the three spin-values...

regards

marlon

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Daniel.

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What exactly do you mean by these words ?dextercioby said:

Daniel.

marlon

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Daniel.

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marlon

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Because second-class constrained systems are rather dull and simple to quantize using the Dirac bracket & the second principle,other more spectacular methods (BRST) were developed,as the transformation of a II-nd class system in a I-st class counterpart and applying the traditional BRST techniques.

I'm quite proud that the 2 teachers who contributed mostly to my scientifical knowledge are working in this domain.

Quite interesting...

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Sounds very interesting indeed

marlon

marlon

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selfAdjoint

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Yes it does. References, Dexter?

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My 2 teachers wrote a book (unfortunately in Romanian,so it's not in your libraries) on "Quantization of Second-Class Theories" based on their numerous articles in Nucl.Phys.B and other peer-reviewed journals.Actually they wrote many books,but that's on the sbject i discussed earlier:transforming a second class system---->gauge system and quantizing it via BRST cohomological approach.

There are 3 working groups (on this specific subject) in Europe that i know of:the one at ULB with prof.Henneaux,the one at Craiova with prof.Bizdadea and the one at Moscow with Batalin,Fradkin,Vilkoviski,...(about the Russians,they must be really in their '60-s at least,they published at the end of the '70's,so they're probably retired,but surely they've left their places to someone else).

Daniel.

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any references to articles in peer reviewed journals, dexter ?

marlon

marlon

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C.Bizdadea,S.O.Saliu,Nucl.Phys.B469(1996),302.

C.Bizdadea,S.O.Saliu,Phys.Lett.B368(1996),202.

C.Bizdadea,Phys.Rev.D53(1996),7138.

And so on and so forth.

And a ton on arxiv.

Daniel.

- #16

Haelfix

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The three spin state photon must therefore have a small mass. But wait its not that easy. If we require local gauge invariance, one immediately notices the small mass term is not gauge invariant, which clashes horribly with what we know. The theory will be nonrenormalizable.

Am I missing something?

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If we build interaction theories (not necessarily in the SM) from the principle of minimal coupling,then matter fields will never couple to second class fields,because the latter don't have gauge invariance by definition.

Daniel.

P.S.Guys,this discussion is at classical level... Quantization is another matter.

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All you say is very true. However, the Higgs-mechanism incorporates zero mass spin 1 bosons (the photon that is). The local U(1) symmetry of EM-interactions is never broken after the continuous breakdown of symmetry. Therefore the photon does not interact with the Higgs-field. Before this symmetry-loss, all elementary particles are massless...Haelfix said:

The three spin state photon must therefore have a small mass. But wait its not that easy. If we require local gauge invariance, one immediately notices the small mass term is not gauge invariant, which clashes horribly with what we know. The theory will be nonrenormalizable.

Am I missing something?

marlon

- #19

Haelfix

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There is an infinite class of non gauge invariant, nonrenormalizable theories, what makes this attractive?

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In the end,it's purely a theoretical model.We'll have to change everything,if the photons will turn out to be massive...Which i hope will never happen.

Daniel.

- #21

what_are_electrons

Been reading Quantum Theory of Light (R. Loudon) and Quantum Chromodynamics (G.Schaefer) but have not come across any reference to a spin = 1 (using 1/2, 1/2) for photons. Where can I read about these 1/2, 1/2 states?dextercioby said:

Daniel.

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Pierre Ramond:"Field Theory:A Modern Primer",L.H.Ryder:"Quantum Field Theory".

Daniel.

Daniel.

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Haelfix

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