Recent content by fala

spin is an intrinsic angular momentum of Dirac field. you can derive it by investigation of invariance of Dirac Lagrangian under a infinitesimal variation of spinors. spinors are imaginary entities.you can not define spin as function of space-time(it may be possible in string theory??)

the hamiltonian of a system must be invariant by a small rotation around an arbitary axis in 3d.this gives the generators namely angular momentum. in 4d gives angular momentum and spin. you can study neother theorm in QFT.