* Dates within the next 7 days are marked by a star.
Kalle Kytölä (Aalto University)
Virasoro algebra and Sugawara constructions, not just informally
* Tuesday 09 September 2025, 10:15, M3 (M234)
Prof. Nuutti Hyvönen (Aalto University)
Electrical impedance tomography: a simple linearization approach
* Tuesday 09 September 2025, 15:15, U6 (U149)
The goal of electrical impedance tomography (EIT) is to reconstruct the internal conductivity of an examined body from boundary measurements of current and voltage. As the current-voltage pairs depend nonlinearly on the conductivity, EIT leads to a nonlinear inverse elliptic boundary value problem that is severely ill-posed: significant alterations in the internal conductivity may only cause tiny changes in the boundary measurements.
This talk first briefly reviews some standard mathematical models for EIT, in particular, indicating how practical restrictions of the underlying imaging modality are often ignored in mathematical analysis. The focus then shifts to the simplest approach to solving the inverse problem of EIT, i.e., linearizing the forward model around a constant conductivity level and solving the resulting linear inverse problem for a perturbation in the conductivity. It is shown how an appropriate choice of a basis for the conductivity perturbation (Zernike polynomials) allows to introduce an explicit solution formula and prove Lipschitz stability for the linearized problem over infinite-dimensional subspaces of square-integrable conductivity perturbations. The results are demonstrated via numerical examples on both simulated and experimental data.
Dr. Padraig Ó Catháin
Monomial groups and combinatorial matrices
* Thursday 11 September 2025, 15:15, M3 (M234)
D. G. Higman observed that the centraliser algebra of a rank 3 permutation group is spanned by the incidence matrix of a strongly regular graph on which the permutation group acts by automorphisms. Quite generally, incidence matrices of combinatorial structures invariant under a permutation group are contained in the centraliser algebra of the corresponding permutation representation.
In this talk, I will explain how monomial representations act on matrices of combinatorial interest with entries in a finite subset of $\mathbb{C}$. I will explain how central extensions, character sums and Gröbner basis techniques can be combined to classify complex Hadamard matrices with sufficiently rich automorphism groups. The talk will require knowledge only of elementary group theory and linear algebra. This is joint work with Santiago Barrera-Acevedo, Heiko Dietrich and Ronan Egan.
ANTA Seminar / Hollanti et al.
Dissertation
Niklas Miller
PhD Defence: Lattices and packings of convex bodies
* Friday 12 September 2025, 12:00, M1 (M232)
Further information
ANTA Seminar / Hollanti et al.
Alessandro Filippo
Walk-induced strategies for updating Katz centrality and applications to Network Robustness
Wednesday 17 September 2025, 14:00, M1 (M232)
Numerical Analysis seminar
Dissertation
Okko Makkonen
PhD Defence: Algebraic methods for secure coded computing
Friday 10 October 2025, 12:00, M1 (M232)
Further information
ANTA Seminar / Hollanti et al.
Prof. Gretchen Matthews (Virginia Tech)
Colloquium talk (TBA)
Tuesday 14 October 2025, 15:15, M1 (M232)
Further information
Prof. Gretchen Matthews (Virginia Tech)
TBA
Tuesday 14 October 2025, 15:15, M1 (M232)
TBA
Prof. Tuomas Hytönen (Aalto University)
TBA
Tuesday 09 December 2025, 15:15, M1 (M232)
TBA
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