Category: Málstofa í stærðfræði

Lukas Schneiderbauer

Carlos Argaez Garcia, nóvember 22, 2019

Math colloquium

Fyrirlesari: Lukas Schneiderbauer, Háskóli Íslands

Titill: Non-Commutative Geometry: An introduction.

Ágrip:

This is my attempt to introduce non-commutative geometry to mathematicians. After putting forward the main ideas and main theorem(s), I will concentrate on the construction of simple examples in the context of fuzzy spaces (special cases of non-commutative geometries). In case time still allows it, I shall tell you about my past research in this area.

Anna Helga Jónsdóttir och Benedikt Steinar Magnússon

Valentina Giangreco, nóvember 19, 2019

Math colloquium

Fyrirlesari: Anna Helga Jónsdóttir og Benedikt Steinar Magnússon, Háskóli Íslands

Titill 1: Student evaluations of teaching at the University of Iceland – analysis of data from 2013 – 2017

Ágrip 1:

Student evaluations of teaching (ísl. kennslukönnun) is administrated at the end of each and every course at the University of Iceland with the purpose of improving teaching and learning. In the talk, analysis of data from student evaluations from 2013 to 2017 at the UI will be presented. Mixed effect models were used to investigate possible relationships between the grades students give courses and several variables, such as the age and gender of the student and the teacher, number of students taking the course and the average final grade in the course.

Titill 2: Online course notes in Edbook and the role of the textbook

Ágrip 2:

In the last years I, with the help of many good people, have been developing a platform for online course notes called Edbook (http://edbook.hi.is). It consists of using Sphinx, which was developed for and in Python, along with specialized extension suited for teaching material in Mathematics. We have been using these notes in a few courses, mostly big calculus courses. The students have overall been very happy with them but in the spring of 2019 I had students in Mathematical Analysis II (STÆ205G) answer a more detailed survey about their usage of the teaching material they used. I will introduce the Edbook platform and the results of the survey which raises some questions about the role of the textbook today.

Staðsetning: HB5 (Háskólabíó)
Tími: Föstudag 15.nóvember kl. 11:40

Room: HB5 (Háskólabíó)
Time: Friday 22th November, 11:40hrs

Sigurður Freyr Hafstein

Carlos Argaez Garcia, nóvember 11, 2019

Math colloquium

Fyrirlesari: Sigurður Freyr Hafstein, Háskóli Íslands

Titill: Lyapunov functions for stochastic differential equations and their computation

Staðsetning: HB5 (Háskólabíó)
Tími: Föstudag 15.nóvember kl. 11:40

Ágrip:

Attractors and their basins of attraction in deterministic dynamical systems are most commonly studied using the Lyapunov stability theory.  Its centerpiece is the Lyapunov function, which is an energy-like function from the state-space that is decreasing along all solution trajectories.
The Lyapunov stability theory for stochastic differential equations is much less developed and, in particular, numerical methods for the construction of Lyapunov functions for such systems are few and far between.  We discuss the general problem and present some novel numerical methods.

Iman Mehrabinezhad

Carlos Argaez Garcia, október 30, 2019

Math colloquium

Fyrirlesari: Iman Mehrabinezhad, Háskóli Íslands

Titill: A new method for computation and verification of contraction metrics

Staðsetning: HB5 (Háskólabíó)
Tími: Föstudag 8.nóvember kl. 11:40

Ágrip:

The determination of exponentially stable equilibria and their basin of attraction for a dynamical system given by a general autonomous ordinary differential equation can be achieved by means of a contraction metric. A contraction metric is a Riemannian metric with respect to which the distance between adjacent solutions decreases as time increases.
The Riemannian metric can be expressed by a matrix-valued function on the phase space.The determination of a contraction metric can be achieved by approximately solving a matrix-valued partial differential equation by mesh-free collocation using Radial Basis Functions (RBF).
Then, we combine the RBF method (to compute a contraction metric) with the CPA method to rigorously verify it. In particular, the computed contraction metric is interpolated by a continuous piecewise affine (CPA) metric at the vertices of a fixed triangulation, and by checking finitely many inequalities, we can verify that the interpolation is a contraction metric. Moreover, we show that, using sufficiently dense collocation points and a sufficiently fine triangulation, we always succeed with the construction and verification.
This presentation is based on a joint work with Prof. Sigurdur Hafstein (University of Iceland), and Prof. Peter Giesl (University of Sussex, UK).

Henning Arnór Úlfarsson

Carlos Argaez Garcia, september 24, 2019

Math colloquium

Fyrirlesari: Henning Arnór Úlfarsson, Háskólinn í Reykjavík

Titill: Pattern avoidance in various domains

Staðsetning: HB5 (Háskólabíó)
Tími: Föstudag 25.oktúber kl. 11:40

Ágrip:

When one searches the web for „pattern avoidance“ most of the results are about pattern avoiding permutations and their variants, such as colored, partial, multi-, affine, signed, and poset permutations. However there are definitions and results about similar concepts in other objects, such as graphs and topological spaces. We will survey these examples of pattern avoidance as well as highlighting more recent variants, such as polyominoes, integer partitions and alternating sign matrices.

This talk will be accessible to any student who has walked past a room where discrete mathematics was being taught.

Björn Birnir

Carlos Argaez Garcia, ágúst 23, 2019

Math colloquium

Fyrirlesari: Björn Birnir, Center for Complex and Nonlinear Science at the University of California at Santa Barbara (UCSB)

Titill: When can we expect the Greenland glacier to melt?

Staðsetning: VR-II,V-258
Tími: Þriðjudag 27.ágúst kl. 11:00

Ágrip:

It was suggested by Rose (2005) that because of the migratory and responsive nature of the capelin, a small pelagic fish that is key to the ecology and fisheries of the North Atlantic, it can be viewed as the „canary in the coalmine“ to detect signals of environmental changes in the Arctic Ocean. In this talk we will combine analysis of data and extensive simulations of the migrations of the capelin and its physiology to analyze the changes in the ocean environment taking place over the last half-century. The environmental data for the last thirty year is obtained from a database called Copernicus, constructed by the European Union. Our goals will be to understand and predict the migrations of the capelin and its interactions with the ocean environment. We will explain how these have changed over time and how they are likely to change in the future. Then we will explain how our simulations can be compared with data, with the aim of finding out the rate of the temperature changes in the Arctic Ocean and when thresholds for major disruptions in Arctic environments are likely to be reached. The recent changes in the spawning routes of the capelin lead to a startling prediction.

Arnbjorg Soffia Arnadottir

Carlos Argaez Garcia, ágúst 20, 2019

Math Phys seminar

Fyrirlesari: Arnbjorg Soffia Arnadottir,University of Waterloo

Titill: Continuous Quantum Walks

Staðsetning: VR-II, V-158
Tími: Fimmtudag 22.ágúst kl. 11:00

Ágrip:

Continuous quantum walks arise naturally as quantum analogues of continuous random walks, but in contrast to their classical counterparts, they exhibit some curious and counter-intuitive properties. I will give an introductory talk on continuous quantum walks and present some of these exciting properties. 
The motivation for studying quantum walks largely comes from quantum physics and quantum computing, however, the emphasis of this talk will be on the mathematics. In particular, no prior knowledge of anything quantum is assumed.

Finnur Lárusson

Valentina Giangreco, júní 7, 2019

Málstofa í stærðfræði

Fyrirlesari: Finnur Lárusson, Adelaide University

Titill: Chaotic holomorphic automorphisms of Stein manifolds with the 
volume density property

Staðsetning: VR-II, V-158
Tími: þriðjudagur 9. júlí kl. 11.00

Ágrip:

I will report on joint work with Leandro Arosio.  Let $X$ be 
a Stein manifold of dimension $n\geq 2$ satisfying the volume density 
property with respect to an exact holomorphic volume form.  For example, 
$X$ could be $\C^n$, any connected linear algebraic group that is not 
reductive, the Koras-Russell cubic, or a product $Y\times\C$, where $Y$ 
is any Stein manifold with the volume density property. We prove that 
chaotic automorphisms are generic among volume-preserving holomorphic 
automorphisms of $X$.  In particular, $X$ has a chaotic holomorphic 
automorphism. Forn\ae ss and Sibony proved (but did not explicitly 
state) this for $X=\C^n$ in 1997.  We follow their approach closely. 
Peters, Vivas, and Wold showed that a generic volume-preserving 
automorphism of $\C^n$, $n\geq 2$, has a hyperbolic fixed point whose 
stable manifold is dense in $\C^n$.  This property can be interpreted as 
a kind of chaos.  We generalise their theorem to a Stein manifold as above.

Guðmundur Magnússon

Valentina Giangreco, júní 7, 2019

Málstofa í stærðfræði

Fyrirlesari: Guðmundur Magnússon, HI

Titill: Multi Dispatcher Systems and interacting policies

Staðsetning: VR-II, V-258
Tími: þriðjudagur 18. júní kl. 11.00

Ágrip:

This project explores the performance of parallel server system. The focus of the project is a system using multiple heuristic policies to route jobs to a server. To achieve this there is a simulator created that uses the Monte Carlo method to numerically simulate the performance of a system. It displays with figures the result of some simulations under different conditions and answers how different policies interact in this multi dispatcher system.

BSc thesis under the supervision of  Esa Olavi Hyytiä.

Sylvain Arguillère

Valentina Giangreco, júní 7, 2019

Málstofa í stærðfræði

Fyrirlesari: Sylvain Arguillère, CNRS – Institut Camille Jordan – MMCS

Titill: Shape analysis through flows of diffeomorphisms

Staðsetning: VR-II, V-258
Tími: fimmtudagur 13. júní kl. 11.00

Ágrip:

The goal of shape analysis is to compare shapes in a way that takes into account their geometric properties. The end goal is to give an adapted framework for the statistical analysis of medical data, in order to identify sick patients automatically for example. In this talk, I will describe a method introduced by Alain Trouvé, which allows to compare shapes through flows of diffeomorphisms with minimal energy, using tools from differential geometry and optimal control.