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On Erb's uncertainty principle

Hubert Klaja (2016)

Studia Mathematica

We improve a result of Erb, concerning an uncertainty principle for orthogonal polynomials. The proof uses numerical range and a decomposition of some multiplication operators as a difference of orthogonal projections.

On ergodicity for operators with bounded resolvent in Banach spaces

Kirsti Mattila (2011)

Studia Mathematica

We prove results on ergodicity, i.e. on the property that the space is a direct sum of the kernel of an operator and the closure of its range, for closed linear operators A such that | | α ( α - A ) - 1 | | is uniformly bounded for all α > 0. We consider operators on Banach spaces which have the property that the space is complemented in its second dual space by a projection P. Results on ergodicity are obtained under a norm condition ||I - 2P|| ||I - Q|| < 2 where Q is a projection depending on the operator A....

On essential norm of the Neumann operator

Dagmar Medková (1992)

Mathematica Bohemica

One of the classical methods of solving the Dirichlet problem and the Neumann problem in 𝐑 m is the method of integral equations. If we wish to use the Fredholm-Radon theory to solve the problem, it is useful to estimate the essential norm of the Neumann operator with respect to a norm on the space of continuous functions on the boundary of the domain investigated, where this norm is equivalent to the maximum norm. It is shown in the paper that under a deformation of the domain investigated by a diffeomorphism,...

On exact null controllability of Black-Scholes equation

Kumarasamy Sakthivel, Krishnan Balachandran, Rangarajan Sowrirajan, Jeong-Hoon Kim (2008)

Kybernetika

In this paper we discuss the exact null controllability of linear as well as nonlinear Black–Scholes equation when both the stock volatility and risk-free interest rate influence the stock price but they are not known with certainty while the control is distributed over a subdomain. The proof of the linear problem relies on a Carleman estimate and observability inequality for its own dual problem and that of the nonlinear one relies on the infinite dimensional Kakutani fixed point theorem with L 2 ...

On existence and uniqueness of solutions for ordinary differential equations with nonlinear boundary conditions

Alessandro Calamai (2004)

Bollettino dell'Unione Matematica Italiana

We prove an existence and uniqueness theorem for a nonlinear functional boundary value problem, that is, an ordinary differential equation with a nonlinear boundary condition. The proof is based on a Global Inversion Theorem of Ambrosetti and Prodi, which is applied to the boundary operator restricted to the manifold of the global solutions to the equation. Our result is a generalization of an analogous existence and uniqueness theorem of G. Vidossich, as it is shown with some examples.

On existence of equilibria of set-valued maps

Grzegorz Gabor, Marc Quincampoix (2003)

Bollettino dell'Unione Matematica Italiana

The present paper is devoted to sufficient conditions for existence of equilibria of Lipschitz multivalued maps in prescribed subsets of finite-dimensional spaces. The main improvement of the present study lies in the fact that we do not suppose any regular assumptions on the boundary of the subset. Our approach is based on behaviour of trajectories to the corresponding differential inclusion.

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