Selfadjoint extensions of the orthogonal sum of symmetric relations, II

Abstract

Let S 1 and S 2 be closed symmetric linear relations in Hilbert spaces H 1 and H 2 with finite and equal defect numbers. The selfadjoint extensions of the closed symmetric linear relation S = S 1 ⊕ S 2 are studied and a description for these extensions in the Hilbert space H 1 is given. The results are applied to a class of differential operators.