HAMILTONIAN PATHS IN m x n PROJECTIVE CHECKERBOARDS

For any two squares iota and tau of an m x n checkerboard, we determine whether it is possible to move a checker through a route that starts at iota, ends at tau, and visits each square of the board exactly once. Each step of the route moves to an adjacent square, either to the east or to the north, and may step off the edge of the board in a manner corresponding to the usual construction of a projective plane by applying a twist when gluing opposite sides of a rectangle. This generalizes work of M. H. Forbush et al. for the special case where m = n.