### Department of Mathematics and Systems Analysis

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* Dates within the next 7 days are marked by a star.

Prof. Norbert Peyerimhoff (Durham University)**Expander graphs and curvature***** ** Tuesday 17 December 2019, 15:15, M3 (M234)

Expander graphs are increasing families of graphs which are at the same time sparse and very well connected. They are not only of
practical relevance for the construction of robust networks but their theoretical research uncovered many suprising connections with various mathematical disciplines: representation theory (Kazdhan property (T)), geometric group theory (Cayley graphs), combinatorics (zigzag products), number theory (Ramanujan graphs), spectral theory (Cheeger inequalities) and probability theory (random walks and random covers). Another challenging question about graphs are to introduce proper notions of curvature. In this talk, I will briefly present an analytical approach, due to Bakry-Emery, which allows to define curvature on graphs. Once these concepts are introduced, I will discuss relations between expander graphs and Bakry-Emery curvature.

ANTA Seminar

Dr. Riikka Kangaslampi (Tampere University)**Introduction to hypergraphs***** ** Tuesday 17 December 2019, 16:15, M3 (M234)

In network science problems complex systems or datasets are often modelled as weighted graphs. These models are simple and powerful, but in some cases insufficient to capture the network structure information, if there are higher-order interactions among more than a pair of nodes. Hypergraphs are a generalisation that can be used to tackle this difficulty.
In this talk I will introduce hypergraphs and some of their basic properties and provide a few examples of networks where hypergraphs would be a natural way to describe the interactions. If time permits, I will also discuss current results and research problems related to Ricci curvatures of hypergraphs.

ANTA Seminar

Teemu Pennanen (King's College London)**Convex duality in nonlinear optimal transport***** ** Wednesday 18 December 2019, 10:00, M1 (M232)

Stochastic Sauna 2019

Kaie Kubjas (Aalto)**Exact solutions in log-concave maximum likelihood estimation***** ** Wednesday 18 December 2019, 11:00, M1 (M232)

Stochastic Sauna 2019

Jaron Sanders (TU Eindhoven)**Markov chains for error accumulation in quantum circuits***** ** Wednesday 18 December 2019, 13:00, M1 (M232)

Stochastic Sauna 2019

Vesa Julin (University of Jyväskylä)**The Gaussian isoperimetric problem for symmetric sets***** ** Wednesday 18 December 2019, 14:00, M1 (M232)

Stochastic Sauna 2019

Tom Claeys (Université Catholique de Louvain)**Random growth, interacting particles, and Riemann-Hilbert problems: from KPZ to KdV***** ** Wednesday 18 December 2019, 15:15, M1 (M232)

Stochastic Sauna 2019

Joni Virta (University of Turku)**Fast tensorial independent component analysis***** ** Wednesday 18 December 2019, 16:15, M1 (M232)

Stochastic Sauna 2019

Prashanta Garain**TBA**

Wednesday 15 January 2020, 12:15, M3 (M234)

Seminar on analysis and geometry

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