Multiwavelets for second-kind integral equations

We consider a Galerkin method for an elliptic pseudodifferential operator of order zero on a two-dimensional manifold. We use piecewise linear discontinuous trial functions on a triangular mesh and describe an orthonormal wavelet basis. Using this basis we can compress the stiffness matrix from N-2 to O(n'log N) nonzero entries and still obtain (up to log N terms) the same convergence rates as for the exact Galerkin method.