Uniqueness of solutions to the initial-value problem for partial differential equations with multiple characteristics
The author continues his investigations on the uniqueness of solutions to the Cauchy problem for partial differential operators with multiple characteristics [Ann. Sc. Norm. Super. Pisa, Cl. Sci., IV. Ser. 7, 257- 285 (1980; Zbl 0478.35006)]. Assuming that the multiplicity of the characteristics is constant he shows that uniqueness can be proved without having to put a condition on the subprincipal symbol at doubly characteristic elliptic points. The proof is based on a Carleman estimate.
scientific article; zbMATH DE number 3918885