Date/Time : 31 Oct 2018 14:00
Venue : S17 #04-06 SR1
Speaker : Francois Labourie, University of Nice – Sophia Antipolis

The general subject of the talk will be to explain techniques helping in building surfaces in spaces. We will first recall how one can build (topologically) surfaces from triangles. Moving to geometry, and after a brief crash course in plane hyperbolic geometry, we will explain how one can describe « hyperbolic » surfaces out of « ideal triangles » in the hyperbolic plane, which themselves correspond to triple of points in the projective line. After having explained these basic constructions, I will explain how one can move to describe triangles associated to Lie group — think of of the group of invertible matrices with complex coefficients –and explain how these constructions, will the help of ideas from Probability Theory, can help to solve our initial problem: building surfaces in spaces known as symmetric spaces. The talk should be accessible to graduate students and I will assume no knowledge of hyperbolic geometry and Lie groups. This is motivated by a recent collaboration with J.Kahn and S. Mozes.

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Date/Time : 24 Oct 2018 16:00
Venue : S17 #05-12 SR4
Speaker : An Xinliang, National University of Singapore

Date/Time:24 Oct 2018 16:00 Venue: S17 #05-12 SR4 Speaker: An Xinliang, National University of Singapore Formation of Singularity in General Relativity I I will present three introductory talks on a mathematical approach to studying singularity formation in general relativity. In the first talk, basic concepts and theorems of space time geometry will be discussed. PhD students in 1st and 2nd years are welcome to attend. Add to calendar: 

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Date/Time : 18 Oct 2018 16:00
Venue : S17 #05-12 SR4
Speaker : An Xinliang, National University of Singapore

Date/Time:31 Oct 2018 16:00 Venue: S17 #05-12 SR4 Speaker: An Xinliang, National University of Singapore Formation of Singularity in General Relativity II In this talk, I will address an interesting physical question: can a black hole form dynamically in the vacuum? Without the help of matter, we will show that focusing of gravitational waves could lead to black hole formation. Add to calendar: 

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Date/Time : 16 Aug 2018 14:00
Venue : S17 #04-05 SR2
Speaker : Dong Chaoping, Shanghai Normal University

Date/Time:16 Aug 2019 14:00 Venue: S17 #04-05 SR2 Speaker: Dong Chaoping, Shanghai Normal University Dirac cohomology: Towards the classification We will recall necessary math ingredients related to the notion of Dirac cohomology, such as Parthasarathy’s Dirac operator inequality, PRV-component, spin module, the unitarily small convex hull, and the spin norm. Then we will discuss some recent progress towards the classification of irreducible unitary representations with non-vanishing Dirac cohomology. In particular, we will mention a few questions. Add to calendar: 

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Date/Time : 27 Jul 2018 15:00
Venue : S16 #05-96
Speaker : Asaf Hajiyev, Azerbaijan National Academy of Sciences

Date/Time:27 Jul 2018 15:00 Venue: S16 #05-96 Speaker: Asaf Hajiyev, Azerbaijan National Academy of Sciences Some Paradoxical Phenomena in Theory of Probability and The mathematical models of moving particles, describing a behavior of traffic, communication, queuing and other systems are considered. Motion of particles depends on a distance between them. It is provided that in stationary regime each separately considered particle makes the binomial random walk. This fact allows to calculate some characteristics of traffic systems and predict a traffic jam. In the capacity of an efficiency index in these systems, an average waiting time of particle in the fixed point is taken. A control function is introduced, which means delay of some particles during motion. The class of systems for which introducing of delays can reduce an efficiency index is described. The optimal function minimizing an efficiency index is found. Numerical examples demonstrating results are given. Add to calendar: 

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Date/Time : 27 Jun 2018 15:30
Venue : S17 #04-04 SR3
Speaker : Johnson, Liu Qiang , University of Macau

Date/Time:27 Jun 2018 15:30 Venue: S17 #04-04 SR3 Speaker: Johnson, Liu Qiang, University of Macau Inference of Spot Volatility in the presence of Infinite Variation Jumps Empirical evidences witness that the jumps appear to be very frequent in the financial markets. In this talk, we propose a kernel estimator for the spot volatility of an Ito semi-martingale at a given time point by using the high frequency data, under the circumstance that the jumps contained in the underlying driven process could be of infinite variation. The estimator is based on the representation of the characteristic function of Levy processes. The consistency of the proposed estimator is established under some mild assumptions. By assuming that the jump part of the underlying process behaves like a symmetric stable Levy process around 0, we establish the asymptotic normality of the proposed estimator. In particular, with a specific kernel function, the estimator is variance efficient. We conduct Monte Carlo simulation studies to assess our theoretical results. We also extend our theories to the estimation of spot covariation quantities between two Ito semi-martingales. Our estimators are applied to some real high frequency financial data sets for empirical analysis. Add to calendar: 

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Date/Time : 23 May 2018 10:30
Venue : S17 #04-06 SR1
Speaker : Claudia Klüppelberg , Technical University of Munich

Date/Time:23 May 2018 10:30 Venue: S17 #04-06 SR1 Speaker: Claudia Klüppelberg, Technical University of Munich Max-linear models on graphs Graphical models are a popular tool to analyse and visualise dependence properties between random variables; see e.g. Lauritzen (1996). Each node in the graph represents a random variable, and the absence of an edge between two nodes indicates conditional independence between the corresponding random variables. We introduce a new recursive structural equation model, where all random variables can be written as a max-linear function of their parents and independent noise variables. In particular, we define directed graphical models, where edge orientations come along with an intuitive causal interpretation and present conditional independence properties of the model. Furthermore, we use algebraic methods to characterise all max-linear models, which are generated by a structural equation model and detail the relation between the coefficients of the structural equation model (the edge weights of the graph) and the max-linear coefficients. Finally, we extend finite-dimensional max-linear models to models on infinite graphs, and investigate their relations to classical percolation theory, more precisely to nearest neighbour Bernoulli bond percolation. The talk is based on joint work with Nadine Gissibl, Steffen Lauritzen, Moritz Otto, and Ercan Sönmetz. Add to calendar: 

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Date/Time : 16 May 2018 14:00
Venue : IMS Seminar Room, House 3
Speaker : Michael Miksis, Northwestern University

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Date/Time : 16 May 2018 15:30
Venue : IMS Seminar Room, House 3
Speaker : Wei Jiang, Wuhan University

In this talk, I will talk about our work about modeling solid-state dewetting problems. Taking the 2D case for example, I will explain the main idea behind these approaches; some extensions to the 3D case will be also presented. If time permits, I will talk about our recent work about using Onsager’s variational principle to derive reduced models with applications to solid-state dewetting.

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