Complete Low Frequency Analysis for the Reduced Wave Equation with Variable Coefficients in Three Dimensions *
Norbert Weck, Karl J. Witsch · Communications in Partial Differential Equations · 1992
We study the low frequency asymptotics of the solutions uw, to some exterior boundary value problems for reduced wave equations in three dimensions with frequencies w. The coefficients of the underlying differential operator and of the right hand sides are allowed to be variable and tend to those of the Laplacian and to 0 respectively at infinity with a certain order. As far as allowed by this order an asymptotic expansion in terms of powers of w is determined.