Based on example 10.3 in the textbook, the Proca Lagrangian for a vector (spin-1) field is written as
L=-(1)/(16\pi )F_(\mu )
u F^(\mu v)+(1)/(8\pi )((mc)/(?))^(2)A^(v)A_(v)where the field strength tensor is defined as
F_(\mu )
u =del_(\mu )A_()
u -del_()
u A_(\mu ), and
mis the mass of the vector field. Applying the Euler-Lagrange equation of motion, derive the field equation
del_(\mu )F^(\mu v)+((mc)/(?))^(2)A^(v)=0.Why does the Proca Lagrangian not preserve gauge invariance? Can you explain why the photon is a massless particle?
