A finite element to interpolate symmetric tensors with divergence inL 2

Inner approximations of the space of second order symmetric tensors with square-integrable «divergence» over a bounded domain inR ² are built up by means of a family of affine elements, analogous to the family defined by Raviart and Thomas in the case of vectors. As an application, we solve the Dirichlet problem for the biharmonic operator by a method of «equilibrium» type.