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Sep
8
answered Tensor Operators
Sep
8
revised Anomalies and Modification of symmetry algebra
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Sep
8
revised Anomalies and Modification of symmetry algebra
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Sep
8
answered Anomalies and Modification of symmetry algebra
Sep
6
awarded  Enlightened
Sep
6
awarded  Nice Answer
Sep
1
revised What is the interpretation of the Chern-Simons electromagnetic spin density?
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Sep
1
answered What is the interpretation of the Chern-Simons electromagnetic spin density?
Aug
22
awarded  mathematical-physics
Aug
21
comment What is the algebraic property that corresponds to a topological term?
2) When you say that you want to go from quantum to classical, I assume that you mean that the quantum theory is defined by means of a path integral, but in general path integrals are ambiguous, and also it is hard to see from them the quantum linear structure that you want to dequantize, this is why I think that methods of geometric quantization are superior.
Aug
21
comment What is the algebraic property that corresponds to a topological term?
@BebopButUnsteady Yes, that what I am trying to tell. The quantization point of view is quite unifying of various physical ideas. But, let me first remark: 1) The WZW terms already change the symplectic structure in the classical theory, not only that but they can spoil the closure of the Jacobi identities resulting nonassociativity and lack of Hilbert space representation of the quantum theory.
Aug
21
answered What is the algebraic property that corresponds to a topological term?
Aug
15
answered If photons carry 1 spin unit, why does visible light seem to have no angular momentum?
Aug
13
comment Why helicity is proportional to the spin of particle and has two values?
@PhysiXxx The helicity eigenvalue in contrast to that of the spin projection indicates the identity of the particle. For example a photon with a positive helicity is a different particle from a photon with a negative helicity. This is because different helicities correspond to different representations of the Poincare' group. This can also be seen in the photon's Fock space where different helicity photons have different creation and annihilation operators.
Aug
13
comment Why helicity is proportional to the spin of particle and has two values?
@PhysiXxx The way I see it is that the computation of the helicity operator is classical, and since the energy of a massless particle is never zero, one may divide by it. After obtaining the classical expression, we quantize according the rules of canonical quantization
Aug
12
comment Why helicity is proportional to the spin of particle and has two values?
@PhysiXxx I have added an update showing the computation of the helicity in 3-vector notation. The generalization of the case of the electromagnetic field (that I know of) requires the use of spinor notation of the massless field equations. It requires more than a few lines. I'll try to find a good reference.
Aug
12
revised Why helicity is proportional to the spin of particle and has two values?
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Aug
12
answered Why helicity is proportional to the spin of particle and has two values?
Aug
8
revised Fractionalization and the structure of spin rotation group?
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Aug
8
answered Fractionalization and the structure of spin rotation group?