Convergence analysis of hybrid expanded mixed finite element method for elliptic equations

In this article, we utilize the approach of the variational characterization of the Lagrange multipliers in Cockburn and Gopalakrishnan (2005) and present the convergence analysis of hybrid expanded mixed finite element method for elliptic equations. The unknowns in the expanded mixed formulation can be expressed in terms of lifting operators. The analysis provides a novel perspective for error estimates of the hybrid expanded mixed finite element method. Numerical examples are presented to confirm the convergence analysis.