  The hadronic form factors of the energy-momentum tensor (EMT) have attracted
considerable interest in recent literature. This concerns especially the D-term
form factor D(t) with its appealing interpretation in terms of internal forces.
With their focus on hadron structure, theoretical studies so far have
concentrated on strongly interacting systems with short-range forces. Effects
on the EMT due to long-range forces like the electromagnetic interaction have
not yet been studied. Electromagnetic forces play a small role in the balance
of forces inside the proton, but their long-range nature introduces new
features which are not present in systems with short-range forces. We use a
simple but consistent classical field theoretical model of the proton to show
how the presence of long-range forces alters some notions taken for granted in
short-range systems. Our results imply that a more careful definition of the
D-term is required when long-range forces are present.
