Elenco seminari del ciclo di seminari
“SCUBE”

Series of Semester Seminars organized at the Department of Mathematics, University of Bologna. The presentations mainly cover Numerical Linear Algebra problems and their wide range of applications. Broader contributions are very welcome.
Ottobre
10
2024
Kai Bergermann, Math Dept, TU-Chemnitz, Germany
nell'ambito della serie: SCUBE
nel ciclo di seminari: SCUBE
Seminario di analisi numerica
Multiplex networks are used to model complex systems from myriad applications. They generalize classical complex networks by recording different types of relationships, different interactions, or changing interactions over time between the same entities in different layers. They possess natural linear algebraic representations in terms of structured matrices, which makes efficient numerical linear algebra techniques a valuable tool for their analysis. In this talk, we give an overview over several network science problems that can be formulated in terms of matrix function expressions, which we approximate by polynomial and rational Krylov methods. We discuss centrality measures, the solution of stiff systems of non-linear differential equations with exponential Runge--Kutta integrators, as well as un- and semi-supervised community detection. Additionally, we present a nonlinear spectral method for core-periphery detection in multiplex networks. All presented methods have a linear runtime scaling, which allows the treatment of large-scale multiplex networks and we present numerical experiments for all considered problems.
Maggio
14
2025
Karl Meerbergen, KU Leuven
nel ciclo di seminari: SCUBE
Seminario di analisi numerica
A nonlinear matrix is a matrix whose entries are nonlinear functions of a parameter. Such problems arise from physics (Schroedinger equation) and mechanical engineering (porous materials, boundary element method, e.g.). The last 20 years, rational approximation methods and linearization were proposed to approximate such matrices by linear pencils of much higher dimensions. Applications are the nonlinear eigenvalue problem, parametric linear systems, frequency sweeping, model order reduction and the solution of time dependent problems with nonlinear frequency dependencies. We give an overview of approximation methods with focus on AAA and Krylov methods that exploit the structure of the linear pencil.