A sequence of order relations, encoding heteroclinic connections in scalar parabolic PDE

We address the problem of heteroclinic connections in the attractor of dissipative scalar semilinear parabolic equations ut = uxx + ƒ (x, u, ux), 0 < x < 1 on a bounded interval with Neumann conditions. Introducing a sequence of order relations, we prove a new and simple criterion for the existence of heteroclinic connections, using only information about nodal properties of solutions to the stationary ODE problem. This result allows also for a complete classiffication of possible attractors in terms of the permutation of the equilibria, given by their order at the two boundaries of the interval.