Convergence analysis of a multigrid algorithm for the acoustic single   layer equation
  We present and analyze a multigrid algorithm for the acoustic single layer equation in two dimensions. The boundary element formulation of the equation is based on piecewise constant test functions and we make use of a weak inner product in the multigrid scheme as proposed in \cite{BLP94}. A full error analysis of the algorithm is presented. We also conduct a numerical study of the effect of the weak inner product on the oscillatory behavior of the eigenfunctions for the Laplace single layer operator. 
Simon Gemmrich, Jay Gopalakrishnan, Nilima Nigam
math.NA