Mixed Hybrid Finite Element Approximations Of Second Order Elliptic Boundary Value Problems

Mixed-hybrid finite element approximations are described for second-order elliptic boundary-value problems in which independent approximations are used for the solution and its gradient on the interior of an element and the trace of the gradients on the boundary of the element. This leads to nonconforming finite elements. The independent boundary approximations are introduced by means of Lagrange multipliers. A-priori error estimates are derived. several other finite element models are also obtained as special cases. (Author).