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xxfzero
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Why are photons described by real field, while electrons by complex field?
Oh, sorry, field is a loose statement. I just refer to plane wave or other eigenfunctions by "field" (please see the attached figures, both from Scully's Quantum optics, one from pp5, the other pp27).Simon Bridge said:Define the fields, and do the math, and see.
(Aside: are particles described by fields - or are they understood as disturbances of the field?)
Because they don't carry any kind of charges.xxfzero said:Why are photons described by real field
Because they are charged particles. In general, the quanta of real field have vanishing (Noether) charge, while those of complex field carry non-zero charge., while electrons by complex field?
samalkhaiat said:Because they don't carry any kind of charges.
Because they are charged particles. In general, the quanta of real field have vanishing (Noether) charge, while those of complex field carry non-zero charge.
Gluons carry SU(3) charge, they are described by real gauge fields.samalkhaiat said:Because they don't carry any kind of charges.
Although you may perfectly well have a complex field that is a gauge singlet.samalkhaiat said:while those of complex field carry non-zero charge.
Orodruin said:Gluons carry SU(3) charge, they are described by real gauge fields.Although you may perfectly well have a complex field that is a gauge singlet.
In the end, it boils down to the adjoint representation being real.
Orodruin said:Gluons carry SU(3) charge, they are described by real gauge fields.
Although you may perfectly well have a complex field that is a gauge singlet.
In the end, it boils down to the adjoint representation being real.
No, we don't work this way. If we believe that [itex]G[/itex] is a symmetry of nature, then the irreducible representations of [itex]G[/itex] and experiment tell us about the allowed fields, Lagrangians and charges.xxfzero said:Oh, thank you very much. So if I can roughly speak that when someone gives me a kind of particle, I should check if it has any kinds of Noether charge, then decide either write it as real field or complex field?
samalkhaiat said:No, we don't work this way. If we believe that [itex]G[/itex] is a symmetry of nature, then the irreducible representations of [itex]G[/itex] and experiment tell us about the allowed fields, Lagrangians and charges.
xxfzero said:that real/complex field comes from real/complex representation, is this answer OK?
There is no such "correlation". Nothing prevent you from taking complex combinations if the dimension of the representation space is greater than one.And, still, I want to know what the correlation between real field/complex field and real/complex representation is,
If you have not yet studied group theory, then you should start doing it now.could you please recommend some book/chapters?
samalkhaiat said:No, this is not what I said, and it is not correct. For example, [itex]SU(2)[/itex] has the property that all its representations are real, yet its fundamental representation [itex][2][/itex] can be realized in terms of doublets of complex spinor fields like [tex] q(x) = \begin{pmatrix} u(x) \\ d(x) \end{pmatrix} , l(x) = \begin{pmatrix} e(x) \\ \nu_{e}(x) \end{pmatrix} \ , [/tex] and its adjoint representation [itex][3][/itex] can have multiplets consist of three real scalar fields (not realized in nature) some times called the phions [tex]\vec{\varphi} = \begin{pmatrix} \varphi_{1} \\ \varphi_{2} \\ \varphi_{3} \end{pmatrix} \ ,[/tex] and a triplet containing two complex and one real scalar fields, this is the usual pion triplet [itex](\pi^{\pm} , \pi^{0})[/itex]. Mathematically, the two triplets are equivalent to each other, but the experiment rules out the phions triplet in favour of the pions.
There is no such "correlation". Nothing prevent you from taking complex combinations if the dimension of the representation space is greater than one.
If you have not yet studied group theory, then you should start doing it now.
xxfzero said:OK, thank you. I'll firstly read group theory, esp. representation part, and then return.
Photons are described by a real field because they are considered to be fundamental particles that make up electromagnetic radiation. This field is used to describe the behavior and interactions of photons, as well as their propagation through space.
The use of a real field to describe photons allows for a more accurate and comprehensive understanding of their properties and behavior. It also allows for the prediction and explanation of various phenomena, such as the photoelectric effect and the emission of light from atoms.
The real field description of photons differs from other models, such as the wave-particle duality model, in that it treats photons as excitations of a quantized field rather than individual particles or waves. This model is consistent with the principles of quantum mechanics and has been successful in explaining a wide range of experimental results.
The real field description of photons can be difficult to visualize because it involves a mathematical representation of the field rather than a physical one. However, some models and simulations have been developed to provide visualizations of the behavior and interactions of photons described by a real field.
The real field description of photons is closely related to the concept of electromagnetic waves because photons are considered to be the quanta of these waves. This means that the real field describes the behavior of individual photons, while the concept of electromagnetic waves describes the collective behavior of a large number of photons.