A new a priori error estimate of nonconforming finite element methods

This paper is devoted to a new error analysis of nonconforming finite element methods. Compared with the classic error analysis in literature, only weak continuity, the F-E-M-Test for nonconforming finite element spaces, and basic H ^m regularity for exact solutions of 2m-th order elliptic problems under consideration are assumed. The analysis is motivated by ideas from a posteriori error estimates and projection average operators. One main ingredient is a novel decomposition for some key average terms on (n - 1)-dimensional faces by introducing a piecewise constant projection, which defines the generalization to more general nonconforming finite elements of the results in literature. The analysis and results herein are conjectured to apply for all nonconforming finite elements in literature.