  An action functional is developed for nonlinear dislocation dynamics. This
serves as a first step towards the application of effective field theory in
physics to evaluate its potential in obtaining a macroscopic description of
dislocation dynamics describing the plasticity of crystalline solids.
Connections arise between the continuum mechanics and material science of
defects in solids, effective field theory techniques in physics, and fracton
tensor gauge theories.
  The scheme that emerges from this work for generating a variational principle
for a nonlinear pde system is general, as is demonstrated by doing so for
nonlinear elastostatics involving a stress response function that is not
necessarily hyperelastic.
