Hidden symmetries in acoustic wave systems

Abstract: Mirror symmetry of a wave system imposes corresponding even or odd parity on its eigenmodes. For a discrete system, eigenmode parity on a specific subset of sites may also originate from so-called latent symmetry. This symmetry is hidden, but can be revealed in an effective model upon reduction of the original system onto the latently symmetric sites. Here we show how latent symmetries can be leveraged for continuous wave setups in the form of acoustic networks. These are systematically designed to have point-wise amplitude parity between selected waveguide junctions for all low frequency eigenmodes. We further develop a modular principle: latently symmetric networks can be interconnected to feature multiple latently symmetric junction pairs, allowing the design of arbitrarily large latently symmetric networks. By connecting such networks to a mirror symmetric subsystem, we design asymmetric setups featuring eigenmodes with domain-wise parity. Bridging the gap between discrete and continuous models, our work takes a pivotal step towards exploiting hidden geometrical symmetries in realistic wave setups.