On eigenvalues and inverse singular values of compact linear operators in Hilbert space
J. P. O. Silberstein, FRANK W. SMITHIES · Mathematical Proceedings of the Cambridge Philosophical Society · 1953
1·1. In this paper we shall be concerned with the equations where K is a compact (completely continuous) linear operator in a Hilbert space , K is the adjoint of K, I is the identity operator, x and y are elements of ∥ x ∥ denotes the norm of x, and κ and σ are complex numbers.