Convergence at the origin of integrated semigroups

Lower estimates near the origin for functional calculus on operator semigroups

This paper provides sharp lower estimates near the origin for the functional calculus $F(-uA)$ of a generator $A$ of an operator semigroup defined on the (strictly) positive real line; here $F$ is given as the Laplace transform of a measure or distribution. The results are linked to the existence of an identity element or an exhaustive sequence of idempotents in the Banach algebra generated by the semigroup. Both the quasinilpotent and non-quasinilpotent cases are considered, and sharp results are proved extending many in the literature.

On off-diagonal decay properties of the generalized Stokes semigroup with bounded measurable coefficients

We investigate off-diagonal decay properties of the generalized Stokes semigroup with bounded measurable coefficients on $\mathrm{L}^2_σ (\mathbb{R}^d)$. Such estimates are well-known for elliptic equations in the form of pointwise heat kernel bounds and for elliptic systems in the form of integrated off-diagonal estimates. On our way to unveil this off-diagonal behavior we prove resolvent estimates in Morrey spaces $\mathrm{L}^{2 , ν} (\mathbb{R}^d)$ with $0 \leq ν< 2$.

Dichotomy results for norm estimates in operator semigroups

This is a survey paper concerned with strongly continuous semigroups in a Banach algebra (often itself simply the algebra of bounded linear operators on a Banach space). These are defined either on $(0,\infty)$ or on a sector in the complex plane, in which case they are supposed analytic. However, the semigroups are not assumed to be strongly continuous at 0. The results in this survey, beginning with classical theorems of Beurling, Kato and Neuberger and concluding with recent work by the authors, are of the nature of "0-1" laws, indicating that the quantitative behaviour of the semigroup at …

The Cuntz semigroup and domain theory

Domain theory has its origins in Mathematics and Theoretical Computer Science. Mathematically it combines order and topology. Its central concepts have their origin in the idea of approximating ideal objects by their relatively finite or, more generally, relatively compact parts. The development of domain theory in recent years was mainly motivated by question in denotational semantics and the theory of computation. But since 2008, domain theoretical notions and methods are used in the theory of C*-algebras in connection with the Cuntz semigroup. This paper is largely expository. It presents t…

与具有特定势的薛定谔算子相关的保正性 Riesz 变换的无维数估计

Dimension-free estimates for positivity-preserving Riesz transforms related to Schrödinger operators with certain potentials

本文针对各坐标独立、幂增长非负势的薛定谔算子，通过将半群分解为一维因子并分别估计再合成，证明了相关保正性 Riesz 变换在 L^∞ 上的无维数有界性，并在 a≤1 时推广到 L^1。

Irregular convergence of mild solutions of semilinear equations

We prove that even irregular convergence of semigroups of operators implies similar convergence of mild solutions of the related semi-linear equations with Lipschitz continuous nonlinearity. This result is then applied to three models originating from mathematical biology: shadow systems, diffusions on thin layers, and dynamics of neurotransmitters