* Dates within the next 7 days are marked by a star.
Prof. Christian Webb (University of Helsinki)
Fractional charge correlation functions in the sine-Gordon model and twisted fermions
* Tuesday 21 October 2025, 10:15, M3 (M234)
The sine-Gordon model is a fascinating model of two-dimensional quantum field theory. It is not a conformal field theory, but it is believed to enjoy many interesting properties. This talk will focus on one of these properties known as bosonization. I will discuss how at the so-called free fermion point of the model, certain correlation functions of the sine-Gordon model are tau functions related to two-dimensional Dirac operators with twisting. This talk is based on joint work with Roland Bauerschmidt and Scott Mason.
Theo Elenius
Carleson-type removability results for nonlinear parabolic PDEs
* Wednesday 22 October 2025, 10:15, M3 (M234)
Seminar on analysis and geometry
Hanz Cheng
Model order reduction via domain decomposition and the partition of unity condensed pole interpolation (PU-CPI)
* Wednesday 22 October 2025, 14:00, M3 (M234)
In this talk, we discuss the PU-CPI, first developed in [1], which allows to construct a reduced order model which approximates the eigenvalues of an elliptic operator accurately and efficiently. The PU-CPI is a domain decomposition technique where local subdomain solutions are used to perform model order reduction via RayleighRitz projections. These local subspaces are constructed independently of each other, using data only related to the corresponding subdomain, resulting in a method that can be fully parallelized. Moreover, communication is only needed at the beginning and at the end, namely for distributing the local data, and for transferring the computed local results at the end of each task, respectively. Numerical examples will also be presented to illustrate the efficiency of the method.
[1] A. Hannukainen, J. Malinen, and A. Ojalammi. Distributed solution of laplacian eigenvalue problems. SIAM Journal on Numerical Analysis, 60(1):76103, 2022.
Numerical Analysis seminar
Dr. Augustin Lafay (Aalto University)
TBA
Tuesday 28 October 2025, 10:15, M3 (M234)
Henri Lahdelma
TBA
Wednesday 29 October 2025, 10:15, M3 (M234)
Seminar on analysis and geometry
Prof. Gerardo Barrera (Instituto Superior Técnico Lisboa)
Asymptotic Behavior of the Condition Number of Random Circulant Matrices
Wednesday 29 October 2025, 14:15, M2 (M233)
We analyze the asymptotic distribution of the extremal singular values of random circulant matrices generated by sequences of independent and identically distributed random variables satisfying the Lyapunov condition. Under an appropriate normalization, we establish that, as the matrix dimension tends to infinity, the joint distribution of the largest and smallest singular values converges in distribution to the independent product of Rayleigh and Gumbel laws. This result directly implies that a suitably normalized condition number of such matrices converges in distribution to a Fréchet law in the large-dimensional limit. The condition number serves as a quantitative measure of the sensitivity of linear systems to infinitesimal perturbations of the input. The proof relies on the classical coupling method of EinmahlKomlósMajorTusnády to achieve precise probabilistic control over the spectral extremes. This is a joint contribution with Paulo Manrique (Extremes, 2022).
Stochastics Seminar
Dr. Alexis Langlois-Rémillard (Universität Bonn)
TBA
Tuesday 04 November 2025, 10:15, M3 (M234)
Erno Vihanto
TBA (MSc thesis presentation)
Wednesday 05 November 2025, 10:15, M3 (M234)
Seminar on analysis and geometry
Dr. Francesca Arrigo (University of Strathclyde)
Katz centrality... Just a one-trick pony?
Tuesday 11 November 2025, 15:15, U3 (U141)
Further information
Complex networks are ubiquitous in our daily lives. Frequently, practitioners are interested in identifying the most important, or central, entities within the network. This goal can be achieved using centrality measures, which are functions that assign nonnegative scores to the entities in order to quantify their importance. There are several (families of) centrality measures in the literature, and in this talk I will focus on a specific one; Katz centrality. This centrality was introduced in the 1950s to measure the relative influence of an actor within a social network. Since its introduction, Katz centrality has been adapted to handle various types of graphs and relations, and I will cover some of these after a smooth introduction to networks, walk-based centrality measures, and the original Katz centrality. The goal of my talk is to help you decide for yourself whether the question in the title should be answered positively.
Leah Schätzler
TBA
Wednesday 26 November 2025, 10:15, M3 (M234)
Seminar on analysis and geometry
Prof. Tuomas Hytönen (Aalto University)
TBA
Tuesday 09 December 2025, 15:15, M1 (M232)
TBA
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