Maxwell Lagrangian
= Maxwell Lagrangian
{c}
{title2=$\mathcal L=-\frac14F_{\mu\nu}F^{\mu\nu}$}
The source-free electromagnetic <Lagrangian density> is quadratic in the <electromagnetic field tensor>. Its <Euler-Lagrange field equation> is $\partial_\mu F^{\mu\nu}=0$. Antisymmetry of $F$ makes the density invariant under <gauge transformations>, and contraction of its indices makes it a <Lorentz scalar>.