Jürgen Voigt

Perturbation of Dirichlet forms by measures

AbstractPerturbations of a Dirichlet form

Regulation by polyamines of ornithine decarboxylase activity and cell division in the unicellular green alga Chlamydomonas reinhardtii.

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14-3-3 Proteins Are Constituents of the Insoluble Glycoprotein Framework of the Chlamydomonas Cell Wall

by measures μ are studied. The perturbed form

The spectrum of a Schrödinger operator inL p ℝ v isp-independent

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Stochastic operators, information, and entropy

−μ−+μ+ is defined for μ− in a suitable Kato class and μ+ absolutely continuous with respect to capacity. Lp-properties of the corresponding semigroups are derived by approximating μ− by functions. For treating μ+, a criterion for domination of positive semigroups is proved. If the unperturbed semigroup has Lp-Lq-smoothing properties the same is shown to hold for the perturbed semigroup. If the unperturbed semigroup is holomorphic on L1 the same is shown to be true for the perturbed semigroup, for a large class of measures.

On the existence of the scattering operator for the linear Boltzmann equation

We generalize the Jörgens-Vidav semigroup perturbation theorem: If (U (t)), (V (t)) are s. c. semigroups, the generator of (V (t)) a bounded perturbation of the generator of (U (t)), and some remainder in the iteration series ofV (t) is strictly power compact, then the spectrum ofV (t) outside the spectral disc ofU (t) consists of eigenvalues of finite algebraic multiplicity. As a prerequisite, we show the invariance of components of the essential resolvent set of an operator under relatively power compact pertubations.