Frieze groups are discrete subgroups of the full group of isometries of a flat strip. We investigate here the dynamics of specific architected materials generated by acting with a frieze group on a collection of self-coupling seed resonators. We demonstrate that, under unrestricted reconfigurations of the internal structures of the seed resonators, the dynamical matrices of the materials generate the full self-adjoint sector of the stabilized group C*-algebra of the frieze group. As a consequence, in applications where the positions, orientations and internal structures of the seed resonators are adiabatically modified, the spectral bands of the dynamical matrices carry a complete set of topological invariants that are fully accounted by the K-theory of the mentioned algebra. By resolving the generators of the K-theory, we produce the model dynamical matrices that carry the elementary topological charges, which we implement with systems of plate resonators to showcase several applications in spectral engineering. The paper is written in an expository style.
REFERENCES
Stabilization means tensoring with the algebra of compact operators over a separable Hilbert space.
Notably, the reduction of the crossed products to Morita equivalent (étale) groupoid C*-algebras.
Stably isomorphic algebras are said to be Morita equivalent.
COMSOL Multiphysics is a widely adopted commercial platform for finite element analysis, known to produce reliable simulations of continuous mechanics models.
This is entirely sufficient in our case.