The Kreiss Matrix Theorem on a General Complex Domain
نویسندگان
چکیده
Let A be a bounded linear operator in a Hilbert space H with spectrum Λ(A). The Kreiss matrix theorem gives bounds based on the resolvent norm ‖(zI−A)−1‖ for ‖An‖ if Λ(A) is in the unit disk or for ‖etA‖ if Λ(A) is in the left half-plane. We generalize these results to a complex domain Ω, giving bounds for ‖Fn(A)‖ if Λ(A) ⊂ Ω, where Fn denotes the nth Faber polynomial associated with Ω. One of our bounds takes the form K̃(Ω) ≤ 2 sup n ‖Fn(A)‖, ‖Fn(A)‖ ≤ 2 e (n+ 1) K̃(Ω), where K̃(Ω) is the “Kreiss constant” defined by K̃(Ω) = inf { C : ‖(zI −A)−1‖ ≤ C/dist(z,Ω) ∀ z 6∈ Ω } . By means of an inequality due originally to Bernstein, the second inequality can be extended to general polynomials pn. In the case where H is finite-dimensional, say, dim(H) = N , analogous results are also established in which ‖Fn(A)‖ is bounded in terms of N instead of n when the boundary of Ω is twice continuously differentiable.
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عنوان ژورنال:
- SIAM J. Matrix Analysis Applications
دوره 21 شماره
صفحات -
تاریخ انتشار 1999