Proca equation
= Proca equation
{c}
A massive vector field coupled to a conserved current obeys
$$
\partial_\mu F^{\mu\nu}-m^2A^\nu=-\mu_0J^\nu.
$$
The mass term breaks electromagnetic gauge invariance.
= Proca equation
{c}
A massive vector field coupled to a conserved current obeys
$$
\partial_\mu F^{\mu\nu}-m^2A^\nu=-\mu_0J^\nu.
$$
The mass term breaks electromagnetic gauge invariance.