Chaotic Field Theory - a Sketch
  Spatio-temporally chaotic dynamics of a classical field can be described by means of an infinite hierarchy of its unstable spatio-temporally periodic solutions. The periodic orbit theory yields the global averages characterizing the chaotic dynamics, as well as the starting semiclassical approximation to the quantum theory. New methods for computing corrections to the semiclassical approximation are developed; in particular, a nonlinear field transformation yields the perturbative corrections in a form more compact than the Feynman diagram expansions. 
Predrag Cvitanovic (Dept of Physics & Astronomy, Northwestern   University Evanston IL, USA)