Improved error estimates of hybridizable interior penalty methods using a variable for diffusion problems

In this paper, we derive improved a priori error estimates for families of hybridizable interior penalty discontinuous Galerkin (H-IP) methods using a variable penalty for second-order elliptic problems. The strategy is to use a penalization function of the form O(1/h(1+delta)), where h denotes the mesh size and a is a user-dependent parameter. We then quantify its direct impact on the convergence analysis, namely, the (strong) consistency, discrete coercivity and boundedness (with h(delta)-dependency), and we derive updated error estimates for both discrete energy-and L-2-norms. The originality of the error analysis relies specifically on the use of conforming interpolants of the exact solution. All theoretical results are supported by numerical evidence.