Birkhoff-James orthogonality to a subspace of operators defined between Banach spaces

Abstract

This paper deals with study of Birkhoff-James orthogonality of a linear operator to a subspace of operators defined between arbitrary Banach spaces. In case the domain space is reflexive and the subspace is finite dimensional we obtain a complete characterization. For arbitrary Banach spaces, we obtain the same under some additional conditions. For arbitrary Hilbert space $\mathbb{H},$ we also study orthogonality to subspace of the space of linear operators $L(\mathbb{H}),$ both with respect to operator norm as well as numerical radius norm.

8 Pages, Submitted to Journal of Operator Theory on 12th November, 2019