Show that [math]\displaystyle{ \tilde F_{\mu\nu}F^{\mu\nu} }[/math] can be rewritten as [math]\displaystyle{ \partial_\mu K^\mu }[/math].
What is the vector potential [math]\displaystyle{ A_\mu }[/math] of a static charge at the origin in the axial gauge [math]\displaystyle{ A_0=V=0 }[/math] ?
Establish the expression of the energy-momentum tensor for a complex scalar field.
What is the expression of the energy density and of the momentum density of an electromagnetic field as a function of [math]\displaystyle{ \vec E }[/math] and [math]\displaystyle{ \vec B }[/math]?