Domain walls in nonequilibrium systems and the emergence of persistent patterns

Domain walls in equilibrium phase transitions propagate in a preferred direction so as to minimize the free energy of the system. As a result, initial spatiotemporal patterns ultimately decay toward uniform states. The absence of a variational principle far from equilibrium allows the coexistence of domain walls propagating in any direction. As a consequence, persistent patterns may emerge. We study this mechanism of pattern formation using a nonvariational extension of Landaus model for second-order phase transitions.