Excitation and strain enhancement of gravitational-wave quasi-BICs

Determine whether gravitational-wave quasi-bound states in the continuum can be excited in periodic C2-asymmetric matter distributions by an incident propagating gravitational wave, and whether such structures can produce significant strain enhancements relative to the incident gravitational-wave amplitude at material densities achievable with common materials.

Background

The paper constructs symmetry-protected gravitational-wave bound states in the continuum within linearized general relativity. These idealized modes are infinitely extended in the plane, localized exponentially along the perpendicular direction, and protected from coupling to propagating planar gravitational waves by incompatible C2 rotational parities.

The unresolved problem concerns the realization of finite, matter-supported quasi-BIC analogues. Specifically, it asks whether periodic distributions of ordinary matter with controlled C2 asymmetry can couple an incoming propagating gravitational wave to a localized resonance, and whether the resulting resonance can amplify the gravitational-wave strain sufficiently to be experimentally useful. The paper notes that such effects would parallel excitation and field enhancement in photonic quasi-BIC platforms.