Light-front dynamics (LFD), also known as front-form dynamics, is on of
the three form of relativistic Hamiltonian dynamics distinguished by
Dirac (1949).
At the time Dirac's seminal paper appeared, quantum field theory was in
a state of rapid development and its manifestly-covariant formulation
all but eclipsed the older Hamiltonian formalism. The latter experienced
a revival when the usefulness of the "infinite-momentum frame" was
discovered for current algebra and used by Weinberg (1966) to propose a
"dynamics at infinite momentum."
Since then, LFD has been developed by many different groups, mainly with
the motivation to obtain a viable non-perturbative treatment of
strongly-interacting systems, in particular for QCD, at the amplitude
level.
In the lectures, LFD will be discussed in the first place as an example
of a Hamiltonian framework, in comparison with the two other forms,
instant-form and point-form dynamics. Next, two topics will be
highlighted, namely the treatment of bound states, and the occurrence of
"light-front singularities," i.e., singularities that do not occur in
the manifestly-covariant treatment of the same systems, being specific
to the LF formulation. It will be shown that these singularities can be
tamed
rather easily in perturbation theory, but also that their occurrence is more
serious when bound states are looked for.