Hi, guys,
Why do we assume Lagrangian Density only depend on field variables and their first derivative?
Currently, I am reading Ashok Das's Lectures on Quantum Field Theory.
He says (when he is talking about Klein-Gordon Field Theory):
"In general, of course, a Lagrangian density...
Hi, Everybody!
Currently, I am reading the book "Lectures on Quantum Field Theory" (by Ashok Das)
But I am a bit confusing. Why does Dirac Equation describe spin 1/2 particles?
I have already known that Dirac Equation bears some angular momentum structure, but why it just describe spin...