… We also assume that the reader is well aware of the basic notions of bounded and
unbounded operators as well as the algebraic notions of right and left invertibility …

… In order to avoid trivialities in the bounded case, we further assume that dim H = ∞. Also,
we assume that the reader is well aware of the basic notions of bounded and unbounded …

… that prevent an operator from being invertible. The presentation is based … operators between
incomplete spaces. It builds the enlargement of a normed space and of a bounded operator …

… unbounded linear operators in normed linear (not necessarily Hilbert) spaces with applications
… It remains to prove that T has a bounded inverse. Define a real-valued function ƒ on Un …

… bounded case and the previous definition, we say that an unbounded A with domain D(A) ⊂
H is right invertible if … operators and applications to the spectrum of products, Complex Anal. …

… to have some good knowledge of limit operators; and on the … a criterion on invertibility at
infinity for such operators, provided … subset of R which is unbounded towards plus infinity. A …

… We will nevertheless use Definition 2.23 which also allows unbounded … left and a right
inverse to A exist, and by puzzling these operators together (see Lemma 2.6) we will get some left …

… Suppose we know it is true for some n and let u … is bounded for all For invertible
semigroups, Proposition 4.2 admits the following strengthening, which is useful in applications. …

… of matrices acting as bounded linear operators on euclidean … for "unbounded" operators,
too. The extremal case of a linear … below show, this need not be true. The paper also contains a …

… algebra of all bounded linear operators on H). Most unbounded operators that we encounter
… the latter means that the normal operator A is left invertible, by [6] we get that A is invertible. …