Algebraic characterization of approximate controllability of behaviours   of spatially invariant systems
  An algebraic characterization of the property of approximate controllability is given, for behaviours of spatially invariant dynamical systems, consisting of distributional solutions, that are periodic in the spatial variables, to a system of homogeneous, linear, constant coefficient partial differential equations corresponding to a polynomial matrix. 
Amol Sasane
math.OC math.AP