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Théorie spectrale

H. Buchwalter, D. Tarral (1982)

Publications du Département de mathématiques (Lyon)

Time regularity and functions of the Volterra operator

Zoltán Léka (2014)

Studia Mathematica

Our aim is to prove that for any fixed 1/2 < α < 1 there exists a Hilbert space contraction T such that σ(T) = 1 and | | T n + 1 - T | | ( n 1 ) . This answers Zemánek’s question on the time regularity property.

Time-dependent Schrödinger perturbations of transition densities

Krzysztof Bogdan, Wolfhard Hansen, Tomasz Jakubowski (2008)

Studia Mathematica

We construct the fundamental solution of t - Δ y - q ( t , y ) for functions q with a certain integral space-time relative smallness, in particular for those satisfying a relative Kato condition. The resulting transition density is comparable to the Gaussian kernel in finite time, and it is even asymptotically equal to the Gaussian kernel (in small time) under the relative Kato condition. The result is generalized to arbitrary strictly positive and finite time-nonhomogeneous transition densities on measure spaces. We...

Toeplitz operators in the commutant of a composition operator

Bruce Cload (1999)

Studia Mathematica

If ϕ is an analytic self-mapping of the unit disc D and if H 2 ( D ) is the Hardy-Hilbert space on D, the composition operator C ϕ on H 2 ( D ) is defined by C ϕ ( f ) = f ϕ . In this article, we consider which Toeplitz operators T f satisfy T f C ϕ = C ϕ T f

Topological and algebraic genericity of divergence and universality

Frédéric Bayart (2005)

Studia Mathematica

We give general theorems which assert that divergence and universality of certain limiting processes are generic properties. We also define the notion of algebraic genericity, and prove that these properties are algebraically generic as well. We show that universality can occur with Dirichlet series. Finally, we give a criterion for the set of common hypercyclic vectors of a family of operators to be algebraically generic.

Topological dual of B ( I , ( X , Y ) ) with application to stochastic systems on Hilbert space

N.U. Ahmed (2009)

Discussiones Mathematicae, Differential Inclusions, Control and Optimization

In this paper, we prove that the topological dual of the Banach space of bounded measurable functions with values in the space of nuclear operators, furnished with the natural topology, is isometrically isomorphic to the space of finitely additive linear operator-valued measures having bounded variation in a Banach space containing the space of bounded linear operators. This is then applied to a stochastic structural control problem. An optimal operator-valued measure, considered as the structural...

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