%0 Journal Article %T Ultra-weak formulation of a hypersingular integral equation on polygons and DPG method with optimal test functions %A Norbert Heuer %A Felipe Pinochet %J Mathematics %D 2013 %I arXiv %X We present an ultra-weak formulation of a hypersingular integral equation on closed polygons and prove its well-posedness and equivalence with the standard variational formulation. Based on this ultra-weak formulation we present a discontinuous Petrov-Galerkin method with optimal test functions and prove its quasi-optimal convergence in $L^2$. Theoretical results are confirmed by numerical experiments on an open curve with uniform and adaptively refined meshes. %U http://arxiv.org/abs/1309.1697v1