A Hybridizable Discontinuous Galerkin Method for the Helmholtz Equation   with High Wave Number
  This paper analyzes the error estimates of the hybridizable discontinuous Galerkin (HDG) method for the Helmholtz equation with high wave number in two and three dimensions. The approximation piecewise polynomial spaces we deal with are of order $p\geq 1$. Through choosing a specific parameter and using the duality argument, it is proved that the HDG method is stable without any mesh constraint for any wave number $\kappa$. By exploiting the stability estimates, the dependence of convergence of the HDG method on $\kappa,h$ and $p$ is obtained. Numerical experiments are given to verify the theoretical results. 
Huangxin Chen, Peipei Lu and Xuejun Xu
math.NA