On page 177 in Peskin & Schroeder there is a derivation I have a hard time with. They write the current for a charge at rest as $$j^\mu = (1,0)^\mu e \delta(x). $$ I don't understand what the ...
I have two questions, which are connected with each other. The first question. In a classical relativistic (SRT) case for one particle can be defined (in a reason of "antisymmetric" nature of ...
When I first learned gauge theories in my introductory quantum field theory course, I was taught that the Faraday (field-strength) tensor can be constructed by computing the commutator of the ...
Except when a particle is spin-0, field of all particles transforms when frame of reference is changed, and this defines what spin is. The question is, specifically how does the quantum field ...