In the traditional PDE problem,one approximates symbol by principal symbol in Taylor decomposition's way.In this paper,we apply appropriate wavelets to approximate the symbol operator by a very good compact operator,and such an operator converges very fast to the original symbol operator in the sense of operator's continuity norm.
Qi Xiang YANG.
Symbol Operator and the Speed of ApproximAtion by Compact Operator. Acta Mathematica Sinica, Chinese Series, 2007, 50(5): 999-100 https://doi.org/10.12386/A2007sxxb0117