TY - GEN A1 - Schmidt, Frank T1 - An Alternative Derivation of the Exact DtN-Map on a Circle N2 - The paper supplies an alternative derivation of the exact boundary conditions needed for the solution of time-harmonic acoustic scattering problems modeled by the Helmholtz equation. The main idea is to consider the exterior domain problem as an initial value problem with initial data given on the boundary of a disc or sphere. The solution of the exterior domain problem is obtained via Laplace transformation techniques, where the asymptotic Sommerfeld radiation condition is reformulated accordingly. T3 - ZIB-Report - SC-98-32 KW - Helmholtz equation KW - Dirichlet-to-Neumann map KW - Sommerfeld radiation condition Y1 - 1998 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-3752 ER -