Symmetries of Quotient Networks for Doubly Periodic Patterns on the Hexagonal Lattice

Abstract

Pattern formation, dynamics and bifurcations for lattice models are strongly influenced by the symmetry of the lattice. However, network structure introduces additional constraints, which sometimes affect the resulting behavior. We compute the automorphism groups of all doubly periodic quotient networks of the hexagonal lattice with nearest-neighbor coupling, with emphasis on “exotic” cases where this quotient network has extra automorphisms not induced by automorphisms of the square lattice. These cases comprise three isolated networks and two infinite families with wreath product structure. We briefly discuss the implications for pattern formation, dynamics and bifurcations. This paper is a sequel to a similar analysis of the square lattice and uses similar methods.