Optimized Schwarz methods form a class of domain decomposition methods for the solution of partial differential equations. Optimized Schwarz methods employ a first or higher order boundary condition along the artificial interface to accelerate its convergence. In the literature, analysis of optimized Schwarz methods rely on Fourier analysis and so the domains are restricted to be regular (recta...

In this article, we obtain several new weighted bounds for the numerical radius of a Hilbert space operator. The significance obtained results is way they generalize many existing in literature; where certain values weights imply some known results, or refinements these results. end, present examples that show how our refine well literature, related to topic.

We study various inequalities for numerical radius and Berezin number of a bounded linear operator on Hilbert space. It is proved that the pure two-isometry 1 Crawford 0. In particular, we show any scalar-valued non-constant inner function θ, Toeplitz Tθ Hardy space 0, respectively. also shown multiplicative class isometries sub-multiplicative commutants shift. have illustrated these results wi...

Let ρ ≥ 1 and w ρ (A) be the operator radius of a linear operator A. Suppose m is a positive integer. It is shown that for a given invertible linear operator A acting on a Hilbert space, one has w ρ (A −m) ≥ w ρ (A) −m. The equality holds if and only if A is a multiple of a unitary operator.

An operator T is called (α, β)-normal (0 ≤ α ≤ 1 ≤ β) if αT ∗T ≤ TT ∗ ≤ βT ∗T. In this paper, we establish various inequalities between the operator norm and its numerical radius of (α, β)-normal operators in Hilbert spaces. For this purpose, we employ some classical inequalities for vectors in inner product spaces.

We provide a local as well as a semilocal convergence analysis for a certain class of fixed slope iterations in a Banach space setting. Using a weaker Hölder condition on the operator involved and more precise estimates than in [1], [2] we provide in the semilocal case: finer error estimates on the distances involved and an at least as precise information on the location of the solution; in the...

We show that if T is a bounded linear operator on a complex Hilbert space, then 1 2 ‖T‖ ≤ √ w2(T ) 2 + w(T ) 2 √ w2(T )− c2(T ) ≤ w(T ), where w(·) and c(·) are the numerical radius and the Crawford number, respectively. We then apply it to prove that for each t ∈ [0, 12 ) and natural number k, (1 + 2t) 1 2k 2 1 k m(T ) ≤ w(T ), where m(T ) denotes the minimum modulus of T . Some other related ...