Remarks on Gauge-Invariant Variables and Interaction Energy in QED
  The calculation of the interaction energy in pure QED and Maxwell-Chern-Simons gauge theory is re-examined by exploiting the path dependence of the gauge-invariant variables formalism. In particular, we consider a spacelike straight line which leads to the Poincar\'{e} gauge. Subtleties related to the problem of exhibiting explicitly the interaction energies are illustrated. 
Patricio Gaete