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Diego Mazón


22h
comment The gauge invariance and the tree unitarity
@TwoBs I'm skeptical too. Show your arguments/work, Andrew McAddams . After that, I will remove my downvote.
1d
comment The gauge invariance and the tree unitarity
Andrew McAddams: I only see diagrams the first two diagrams with two vertex and the third one with one. What diagrams are you talking about? @TwoBs and Andrew McAddams: Should we understand the lagrangian of the question as the full lagrangian or as a part of the standard model lagrangian? If the former, there are more symmetries and the analysis is different.
1d
comment The gauge invariance and the tree unitarity
@TwoBs Aren't you and the paper talking about the longitudinal modes and zero mass limit of the $W$s rather than the photon ($A$) as the questions asks??
1d
comment The gauge invariance and the tree unitarity
@TwoBs That paper is based on the fact that amplitudes grow too fast with energy rather than on the appearance of longitudinal modes, right?
1d
comment The gauge invariance and the tree unitarity
I know, but the wording of your question seems to point that there in only ONE massive boson rather than two. Anyway, can you show your calculation? The photon's longitudinal polarization is produced at tree level? I might know what is going on.
2d
comment The gauge invariance and the tree unitarity
@AndrewMcAddams From your notation, the field $W$ seems to be complex (not real). Why do you claim that your first Lagrangian describe a SINGLE massive spin-1 particle"
Jul
25
awarded  Nice Answer
Jul
19
awarded  Necromancer
Jul
12
awarded  Yearling
Jul
2
awarded  Curious
May
30
awarded  Nice Question
Mar
7
comment Why am I wrong about how to view gauge theory?
In this context a redundant transformations means that it does not change the physical state of the system but only the field related to it (and that creates spurious d.o.f).
Mar
7
comment Why am I wrong about how to view gauge theory?
1) Are you saying that non-large gauge transformations (those that are continuously connected with the identity) change the physical state of a system? 2) The gauge transformations you say that they are not redundancies, do they tend to the identity in the space-time boundary? Are they the so-called "large gauge transformations"? Thanks.
Feb
20
awarded  Nice Answer
Feb
17
awarded  quantum-field-theory
Feb
10
comment When is quasiparticle same as elementary excitation, and when is not?
@huotuichang The Poincare algebra has two quadratic Casimir invariant: the square of the cuadri-momentum (the particle's mass) and the square of the Pauli- Lubanski (related to the spin or helicity of the particle), which self-commute. Therefore, the eigenvalues of these operators are good label. This classification is originally due to Wigner. Elementary particles are also classified according to the way they transform under the gauge group of the standard model $U_y(1)\times SU_l(2)\times SU_c(3)$
Feb
7
comment When is quasiparticle same as elementary excitation, and when is not?
Hello @IsidoreSeville Then, can some of you provide the definition of "elementary excitation" in condensed matter physics? I only see one sense in which an "elementary excitation" can be elementary. If this answer is correct, then, in my opinion, this condensed matter terminology should be abandoned because it is confusing and useless.
Feb
7
revised When is quasiparticle same as elementary excitation, and when is not?
dictionary and short answer added
Feb
7
comment When is quasiparticle same as elementary excitation, and when is not?
Hello, you read correctly, but excitation=particle, while elementary$\neq$collective . Thanks.
Feb
6
revised When is quasiparticle same as elementary excitation, and when is not?
added 232 characters in body