Let Ωy \Omega yΩy be a bounded Lipschitz domain in Rd R^dRd, let a=1a=1a=1, and let c∈L∞(Ω)c\in L^{\infty}(\Omega)c∈L∞(Ω) satisfy … For ω≥ω0>0 \omega\geq \omega_0>0ω≥ω0>0, consider the heterogeneous Helmholtz solu…