Fundamental Asymmetries between Spatial and Temporal Boundaries in Electromagnetics

Time-varying materials bring an extra degree of design freedom compared to their conventional time-invariant counterparts. However, few discussions have focused on the underlying physical difference between spatial and temporal boundaries. In this letter, we thoroughly investigate those differences from perspective conservation laws. By doing so, building blocks optics electromagnetics such as reflection law, Snell’s Fresnel’s equations can be analogously derived in a context, but with completely different interpretations. Furthermore, study unique features boundaries, nonconformance energy causality.