  We recall the special features of quantum dynamics on a light-front (in an
infinite momentum frame) in string and field theory. The reason this approach
is more effective for string than for fields is stressed: the light-front
dynamics for string is that of a true Newtonian many particle system, since a
string bit has a fixed Newtonian mass. In contrast, each particle of a field
theory has a variable Newtonian mass P^+, so the Newtonian analogy actually
requires an infinite number of species of elementary Newtonian particles. This
complication substantially weakens the value of the Newtonian analogy in
applying light-front dynamics to nonperturbative problems. Motivated by the
fact that conventional field theories can be obtained as infinite tension
limits of string theories, we propose a way to recast field theory as a
standard Newtonian system. We devise and analyze some simple quantum mechanical
systems that display the essence of the proposal, and we discuss prospects for
applying these ideas to large N_c QCD.
