ESSENTIAL APPROXIMATE POINT SPECTRA FOR UPPER TRIANGULAR MATRIX OF LINEAR RELATIONS

摘要

When A ∈ LR(H) and B ∈ LR(K) are given,for C ∈ LR(K,H) we denote by M C the linear relation acting on the infinite dimensional separable Hilbert space H ⊕ K of the form M C =( A C 0 B).In this paper,we give the necessary and sufcient conditions on A and B for which M C is upper semi-Fredholm with negative index or Weyl for some C ∈ LR(K,H).