# Lectures, seminars and dissertations

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

Dario Gasbarra (University of Helsinki)

**Estimating passengers travel lenghts distributions in Helsinki commuter trains**

*** ** Tuesday 28 February 2017, 10:15, M237

A local train stops at stations 0, 1, . . . , T and passengers
getting in and out a wagon are counted at every station. Since
passengers are not labeled and with the same ticket it is possible to
travel across all the line, when a passenger gets off the train, it is
not known from which station he started. The distribution of the
individual trips satisfies a constrained system of linear
diophanitine equations, which typically is underdetermined.
Nevertheless we show that, when i.i.d. realizations are
collected , the probability distribution of the travel lengths,
depending on the passengers departure station is identifiable.
We use a Bayesian data augmentation, where the the
distribution of the individual trips is the hidden variable. The
posterior distribution is explored by the fiber walk Markov chain
Monte introduced by Diaconis and Sturmfels 1998.

AScI Large Structures Seminar / Freij-Hollanti, Kubjas

Eero Saksman (University of Helsinki)

**The Riemann zeta function meets Gaussian multiplicative chaos**

*** ** Tuesday 28 February 2017, 15:15, M1 (M232)

We begin by recalling some basic properties of the Riemann zeta
function and its relevance to number theory. Later on we describe it's chaotic nature on the critical strip. The final theme to be discussed is the functional statistics of the zeta function on the critical line. The last mentioned topic is based on joint work with Christian Webb (Aalto).

Colloquium of Mathematics and Systems Analysis

Clifford Gilmore (University of Helsinki)

** Growth rates of frequently hypercyclic harmonic functions**

*** ** Wednesday 01 March 2017, 12:15, M3 (M234)

The notion of frequent hypercyclicity stems from ergodic theory and has been an active area of research since it was introduced by Bayart and Grivaux (2004).
Many natural bounded linear operators are frequently hypercyclic, for instance the differentiation operator on the space of entire functions.
We will begin by recalling some basic examples and the pertinent notions of frequent hypercyclicity.
We then consider the partial differentiation operator acting on the space of harmonic functions on R^n.
Our primary goal is to identify sharp growth rates, in terms of the L^2-norm, of harmonic functions that are frequently hypercyclic vectors for the basic partial differentiation operator. This answers a question posed by Blasco et al. (2010).
This is joint work with Eero Saksman and Hans-Olav Tylli.

Seminar on analysis and geometry

Prof. Petteri Kaski

**Arithmetic circuits for multilinear tasks (45min, NOTE unusual time!)**

*** ** Wednesday 01 March 2017, 17:15, M3 (M234)

This talk will give a brief introduction to the design of arithmetic circuits for solving computational tasks, with a focus on multilinear tasks and designs, such as fast matrix multiplication and fast polynomial multiplication in the bilinear case, and higher-order designs such as determinants, permanents, and our recent design (with Andreas Björklund) for the \binom{6}{2}-linear form, which e.g. captures the task of counting the 6-cliques in a given graph.

ANTA Seminar: Algebra, Number Theory, and Applications to Communications and Computing / Karpuk, Kaski, Hollanti, Greferath

Amaro Barreal

**Lattices for physical layer network coding**

Tuesday 07 March 2017, 10:15, M205

Doctoral student talk / Engström

Lauri Perkkiö

**Differential material parameter in finite element analysis**

Tuesday 07 March 2017, 10:40, M205

Doctoral student talk / Engström

Ferdinand Blomqvist

**The closest vector problem in high dimension**

Tuesday 07 March 2017, 15:15, M203

Doctoral student talk / Engström

Antti Ojalammi

**On exterior acoustics and speech modelling**

Tuesday 07 March 2017, 15:40, M203

Doctoral student talk / Engström

Tiina Vesanen

**Numerical aspects of multicentric calculus**

Tuesday 07 March 2017, 16:15, M203

Doctoral student talk / Engström

Diana Apetrei

**Advances in multicentric calculus**

Tuesday 07 March 2017, 16:40, M203

Doctoral student talk / Engström

Juha Kuortti

**Spectral characteristics of the vocal tract**

Wednesday 08 March 2017, 14:40, M205

Doctoral student talk / Engström

Prof. Kaie Kubjas (Aalto)

**Matrices, photos and Netflix**

Wednesday 08 March 2017, 15:00, TU1

LUMA-luennot lukiolaisille / Kangaslampi

Anna-Lena Horlemann-Trautmann

**Symbol Erasures in Random Network Coding**

Wednesday 08 March 2017, 15:15, M3 (M234)

In random network coding we want to communicate over a noisy network channel with one sender and several receivers, where all receivers want to get the same information from the sender. We encode the data before sending it through the network, so the receivers can reconstruct the original data from the corrupted data. From a mathematical point of view, classical tools used in this context are projective spaces over finite fields.
In this talk we will give an introduction to random network coding and explain how the classical model by Kötter and Kschischang treats erasures during the communication. Then we give an alternative model and show that, depending on the network topology, the classical or the alternative model can be advantageous for erasure correction.

ANTA Seminar: Algebra, Number Theory, and Applications to Communications and Computing / Karpuk, Kaski, Hollanti, Greferath

Vesa Kaarnioja

**On the structure and eigenvalues of lattice-theoretic tensors**

Wednesday 08 March 2017, 15:15, M205

Doctoral student talk / Engström

Lauri Mustonen

**Surrogate models and computational inverse problems**

Wednesday 08 March 2017, 15:40, M205

Doctoral student talk / Engström

Mikael Laaksonen

**Spectral inverse iteration for stochastic eigenvalue problems**

Wednesday 08 March 2017, 16:15, M205

Doctoral student talk / Engström

Tom Gustafsson

**Numerical methods for lubrication and elastic contact**

Wednesday 08 March 2017, 16:40, M205

Doctoral student talk / Engström

Mikko Harju

**Spatial decision analysis with incomplete information**

Thursday 09 March 2017, 10:15, M205

Doctoral student talk / Engström

Pekka Laitila

**Facilitating expert elicitation of probabilities for Bayesian networks**

Thursday 09 March 2017, 10:40, M205

Doctoral student talk / Engström

Heikki Puustinen

**Network optimization and simulation in military air mission planning**

Thursday 09 March 2017, 11:15, M205

Doctoral student talk / Engström

Anton von Schantz

**Modeling crowd dynamics in an evacuation as a multiagent system**

Thursday 09 March 2017, 11:40, M205

Doctoral student talk / Engström

Yrjänä Hynninen

**Mathematical methods for medical decision making**

Thursday 09 March 2017, 13:15, M3 (M234)

Doctoral student talk / Engström

Juho Andelmin

**Solving the green vehicle routing problem and allocating resources based on efficiency analysis**

Thursday 09 March 2017, 13:40, M3 (M234)

Doctoral student talk / Engström

Armando Gutiérrez

**The horoboundary of metric spaces and its role in dynamics**

Thursday 09 March 2017, 14:15, M3 (M234)

Doctoral student talk / Engström

Hoa Ngo

**Information spreading in large networks**

Thursday 09 March 2017, 14:40, M3 (M234)

Doctoral student talk / Engström

Pekka Lehtelä

**Generalized solutions to the porous medium equation**

Thursday 09 March 2017, 15:15, M3 (M234)

Doctoral student talk / Engström

Casimir Lindfors

**Regularity for nonlinear parabolic PDEs with general growth**

Thursday 09 March 2017, 15:40, M3 (M234)

Doctoral student talk / Engström

Jonas Tölle

**The ***p*-Laplace evolution equation as *p* tends to 1: Mosco convergence and convergence of solutions

Friday 10 March 2017, 14:15, M3 (M234)

Harmonic analysis and PDE seminar

Eero Ruosteenoja (University of Jyväskylä)

**Tug-of-war games**

Wednesday 15 March 2017, 12:15, M3 (M234)

Ten years ago Peres, Schramm, Sheffield and Wilson introduced two-player zero-sum stochastic games that they called tug-of-war games. They showed that these games have close connections to certain nonlinear PDEs of p-Laplacian and infinity Laplacian type. I will give an overview of the topic. No background knowledge of probability theory is needed.

Seminar on analysis and geometry

Taoufiq Damir

**TBD**

Wednesday 15 March 2017, 15:15, M3 (M234)

ANTA Seminar: Algebra, Number Theory, and Applications to Communications and Computing / Karpuk, Kaski, Hollanti, Greferath

Prof. Henry Segerman (Oklahoma State University)

**"Design of 3D printed mathematical art" **

Wednesday 15 March 2017, 16:00, B-Hall

When visualising topological objects via 3D printing, we need a three-dimensional geometric representation of the object. There are approximately three broad strategies for doing this: "Manual" - using whatever design software is available to build the object by hand; "Parametric/Implicit" - generating the desired geometry using a parametrisation or implicit description of the object; and "Iterative" - numerically solving an optimisation problem.
The manual strategy is unlikely to produce good results unless the subject is very simple. In general, if there is a reasonably canonical geometric structure on the topological object, then we hope to be able to produce a parametrisation of it. However, in many cases this seems to be impossible and some form of iterative method is the best we can do.
I will discuss these matters with many examples, including visualisation of four-dimensional polytopes (using orthogonal versus stereographic projection) and Seifert surfaces (comparing my work with Saul Schleimer with Jack van Wijk's iterative techniques).
I will also describe some computational problems that have come up in my 3D printed work, including the design of 3D printed mobiles (joint work with Marco Mahler), "Triple gear" and a visualisation of the Klein Quartic (joint work with Saul Schleimer), and hinged surfaces with negative curvature (joint work with Geoffrey Irving).

Mathematics and Arts Colloquium / Kirsi Peltonen

Estibalitz Durand Cartagena (UNED, Spain)

**TBA**

Friday 17 March 2017, 15:00, M3 (M234)

Harmonic analysis and PDE seminar

Mikko Stenlund (University of Helsinki)

**TBA**

Wednesday 22 March 2017, 12:15, M3 (M234)

Seminar on analysis and geometry

Matthias Grezet

**TBD**

Wednesday 22 March 2017, 15:15, M3 (M234)

ANTA Seminar: Algebra, Number Theory, and Applications to Communications and Computing / Karpuk, Kaski, Hollanti, Greferath

Matthew Romney (University of Illinois)

**TBA**

Wednesday 29 March 2017, 12:15, M3 (M234)

Seminar on analysis and geometry

Matias Vestberg

**TBA**

Friday 31 March 2017, 14:15, M3 (M234)

Harmonic analysis and PDE seminar

Thomas Westerbäck

**TBD**

Wednesday 05 April 2017, 15:15, M2 (M233)

ANTA Seminar: Algebra, Number Theory, and Applications to Communications and Computing / Karpuk, Kaski, Hollanti, Greferath

Christopher Hopper

**TBA**

Friday 07 April 2017, 14:15, M3 (M234)

Harmonic analysis and PDE seminar

Ville Tengvall (University of Jyväskylä)

**TBA**

Wednesday 12 April 2017, 12:15, M3 (M234)

Seminar on analysis and geometry

Prof. Thomas Britz

**TBD**

Wednesday 12 April 2017, 15:15, M3 (M234)

ANTA Seminar: Algebra, Number Theory, and Applications to Communications and Computing / Karpuk, Kaski, Hollanti, Greferath

Prof. Samuli Siltanen (University of Helsinki)

**Electrical impedance tomography imaging via the Radon transform**

Wednesday 19 April 2017, 12:15, M3 (M234)

Seminar on analysis and geometry

Casimir Lindfors

**TBA**

Friday 21 April 2017, 14:15, M3 (M234)

Harmonic analysis and PDE seminar

Stavros Evdoridis (Aalto)

**TBA**

Wednesday 26 April 2017, 12:15, M3 (M234)

Seminar on analysis and geometry

Prof. Harri Ehtamo (Aalto)

**Evoluutiopelit evakuointimalleissa - Pelastettavien kovan leikin peliteoreettinen kuvaus**

Wednesday 26 April 2017, 15:00, U8

LUMA-luennot lukiolaisille / Kangaslampi

Dr. David Cushing (Durham)

**TBD**

Wednesday 26 April 2017, 15:15, M3 (M234)

ANTA Seminar: Algebra, Number Theory, and Applications to Communications and Computing / Karpuk, Kaski, Hollanti, Greferath

Pekka Lehtelä

**TBA**

Friday 28 April 2017, 14:15, M3 (M234)

Harmonic analysis and PDE seminar

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