A boundary-value problem with an operator in the boundary conditions, for a second-order elliptic differential-operator equation
We prove first a theorem on an isomorphism realized by the operator generated by a second-order elliptic differential-operator equation and by boundary conditions which contain, in general, unbounded operators. After this, making use of the isomorphism theorem, we prove the Fredholm property for the perturbed equation.
second-order elliptic differential-operator equation
Fredholm property for the perturbed equation
scientific article; zbMATH DE number 4030314
scientific article