91 citations · 244 across the 32 of their papers we have counts for
33 papers
Two examples of ungrading in higher education from the United States and from Germany
Christine von Renesse, Sven A. Wegner
In this paper the authors discuss their experiences with ungrading at a small public university in the U.S. as well as a large public university in Germany. The courses described a…
A Lumer-Phillips type generation theorem for bi-continuous semigroups
Christian Budde, Sven-Ake Wegner
The famous 1960s Lumer-Phillips Theorem states that a closed and densely defined operator on a Banach space generates a strongly continuo…
The category of Silva spaces is not integral
Marianne Lawson, Sven-Ake Wegner
We establish that the category of Silva spaces, aka LS-spaces, formed by countable inductive limits of Banach spaces with compact linking maps as objects and linear and continuous…
The left heart and exact hull of an additive regular category
Ruben Henrard, Sondre Kvamme, Adam-Christiaan van Roosmalen +1
Quasi-abelian categories are abundant in functional analysis and representation theory. It is known that a quasi-abelian category is a cotilting torsionfree class of…
Lecture notes on high-dimensional data
Sven-Ake Wegner
These are lecture notes based on the first part of a course on 'Mathematical Data Science', which I taught to final year BSc students in the UK in 2019-2020. Topics include: concen…
Examples and non-examples of integral categories and the admissible intersection property
Souheila Hassoun, Amit Shah, Sven-Ake Wegner
Integral categories form a sub-class of pre-abelian categories whose systematic study was initiated by Rump in 2001. In the first part of this article we determine whether several…
Dissipative extensions and port-Hamiltonian operators on networks
Marcus Waurick, Sven-Ake Wegner
In this article we study port-Hamiltonian partial differential equations on certain one-dimensional manifolds. We classify those boundary conditions that give rise to contraction s…
Well-posedness of a class of hyperbolic partial differential equations on the semi-axis
Birgit Jacob, Sven-Ake Wegner
In this article we study a class of hyperbolic partial differential equations of order one on the semi-axis. The so-called port-Hamiltonian systems cover for instance the wave equa…
On a counterexample in connection with the Picard-Lindelöf theorem
Georgios Passias, Sven-Ake Wegner
We give an example, which demonstrates that in the situation of the Picard-Lindelöf theorem, the Lipschitz condition on the right hand side with respect to , cannot be…
Some remarks on the notions of boundary systems and boundary triple(t)s
Marcus Waurick, Sven-Ake Wegner
In this note we show that if a boundary system in the sense of (Schubert et al. 2015) gives rise to any skew-self-adjoint extension, then it induces a boundary triplet and the clas…
Engaging students in conjecturing through homework in Real Analysis and Differential Equations
Thomas Pawlaschyk, Sven-Ake Wegner
In this note we report on an implementation of discovery-oriented problems in courses on Real Analysis and Differential Equations. We explain a type of task-design that gives stude…
An outlook on self-assessment of homework assignments in higher mathematics education
Sarah Beumann, Sven-Ake Wegner
We discuss first experiences with a new variant of self-assessment in higher mathematics education. In our setting, the students of the course have to mark a part of their homework…
Boundary triplets for skew-symmetric operators and the generation of strongly continuous semigroups
Sven-Ake Wegner
We give a self-contained and streamlined exposition of a generation theorem for C0-semigroups based on the method of boundary triplets. We apply this theorem to port-Hamiltonian sy…
The heart of the Banach spaces
Sven-Ake Wegner
Consider an exact category in the sense of Quillen. Assume that in this category every morphism has a kernel and that every kernel is an inflation. In their seminal 1982 paper, Bei…
Pivot duality of universal interpolation and extrapolation spaces
Christian Bargetz, Sven-Ake Wegner
It is a widely used method, for instance in perturbation theory, to associate with a given C0-semigroup its so-called interpolation and extrapolation spaces. In the model case of t…
A workshop for high school students on naive set theory
Sven-Ake Wegner
In this article we present the prototype of a workshop on naive set theory designed for high school students in or around the seventh year of primary education. Our concept is base…
An open day in the metric space
Sven-Ake Wegner, Katrin Rolka
We report on a workshop for grade eleven high school students, which took place in the framework of a university open day. During the workshop the participants first discovered the…
Non power bounded generators of strongly continuous semigroups
Anna Golińska, Sven-Ake Wegner
It is folklore that a power bounded operator on a sequentially complete locally convex space generates a uniformly continuous -semigroup which is given by the corresponding po…
Variations on Barbalat's Lemma
Bálint Farkas, Sven-Ake Wegner
It is not hard to prove that a uniformly continuous real function, whose integral up to infinity exists, vanishes at infinity, and it is probably little known that this statement r…
Asymptotics of Evolution Equations beyond Banach spaces
Birgit Jacob, Sven-Ake Wegner
We study the asymptotics of strongly continuous operator semigroups defined on locally convex spaces in order to develop a stability theory for solutions of evolution equations bey…
Desch-Schappacher Perturbation of One-Parameter Semigroups on Locally Convex Spaces
Birgit Jacob, Sven-Ake Wegner, Jens Wintermayr
We prove a Desch-Schappacher type perturbation theorem for strongly continuous and locally equicontinuous one-parameter semigroups which are defined on a sequentially complete loca…
The growth bound for strongly continuous semigroups on Fréchet spaces
Sven-Ake Wegner
We introduce the concepts of growth and spectral bound for strongly continuous semigroups acting on Fréchet spaces and show that the Banach space inequality e…
Asymptotic bounds on the equilateral dimension of hypercubes
Lorenz Minder, Thomas Sauerwald, Sven-Ake Wegner
A subset of the finite dimensional hypercube is said to be equilateral if the distance of any two distinct points equals a fixed value. The equilateral dimension of the hypercube i…
Maximal exact structures on additive categories
Dennis Sieg, Sven-Ake Wegner
We show that every additive category with kernels and cokernels admits a maximal exact structure. Moreover, we discuss two examples of categories of the latter type arising from fu…