Construction of Exceptional Points in Time-Modulated High-Contrast Elastic Media

Spatially periodic elastic metamaterials, comprising hard inclusions within a soft matrix in $d$-dimensional space ($d\geq 2$), exhibit a rich spectrum of physical phenomena. This paper investigates such a model and presents the following contributions. First, we analyze the system's subwavelength quasi-frequencies under static conditions, establishing their functional dependence on the high-contrast parameter. This analysis enables the determination of the subwavelength quasi-frequency range. Second, for time-modulated structures, we derive a system of ordinary differential equations (ODEs) within the subwavelength regime. We demonstrate that this ODE system accurately captures the quasi-frequency behavior of the original elastic system. Finally, leveraging the derived ODEs and Floquet's theorem, we construct concrete examples of first-order asymptotic exceptional points (EPs) in three dimensions.