Dynamical Complexity of Planar Piecewise Isometries

In this paper, we investigate dynamical complexity of general planar piecewise isometries. We reveal the relations between the complexity and the admissible finite words generated by a planar piecewise isometry, and present the necessary and sufficient conditions for the complexity to be zero. Furthermore, we give equivalent statements for the complexity to be not less than 1, and also discuss some essential properties about the complexity.