Non-Smooth Solutions of the Elastic Wave Equation and Singularities of the Scattering Kernel

Let Ω be an exterior domain in R ⁿ (n ≥ 3) with a bounded C ^∞ boundary ∂Ω, and consider the elastic wave equation (0.1) ( ∂ t 2 − L ) u ( t , x ) = 0 in  I × Ω , https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003072096/6e6221c8-364d-4a5e-bfe5-98bb034e69b7/content/eq3333.tif"/>