April 2017

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### 03.04.2017 14:45 Paul Stursberg (TUM):Manipulating Single and Double Elimination Knock-out TournamentsMI 02.04.011 (Boltzmannstr. 3, 85748 Garching)

Balanced knockout tournaments are one of the most common formats for sports competitions, and are also used in elections and decision-making. The computational complexity of determining whether there is a way to make a particular player win such a tournament had been an open problem for at least 10 years. We prove that checking whether there exists a draw in which a particular player wins is NP-complete. We also generalize this result to double-elimination tournaments.

### 04.04.2017 10:30 Thomas Fink (Universität Passau):Multi-scale detection of higher order geometric features using TaylorletsMI 02.10.011 (Boltzmannstr. 3, 85748 Garching)

In various fields of image analysis, determining the precise geometry of occurent edges, e.g. the contour of an object, is a crucial task. Especially the curvature of an edge is of great practical relevance. In this talk, we introduce an extension of the continuous shearlet transform which additionally utilizes shears of higher order. This extension, called the Taylorlet transform, allows for a detection of the position and orientation, as well as the curvature and other higher order geometric information of edges. Furthermore, we introduce novel vanishing moment conditions of the form $$\int_{\mathbb{R}} g \left( \pm t^k \right) t^m dt$$. We will show that Taylorlets fulfilling such conditions enable a more robust detection of the geometric edge features.

### 05.04.2017 09:00 https://www.mathfinance.ma.tum.de/kpmgce/konferenzen/aktuelle-konferenzen/conference-innovations-in-insurance-risk-and-asset-management-2017/:Conference: Innovations in Insurance, Risk- and Asset ManagementHörsäle & quanTUM Lounge (Parkring 35, 85748 Garching)

https://www.mathfinance.ma.tum.de/kpmgce/konferenzen/aktuelle-konferenzen/conference-innovations-in-insurance-risk-and-asset-management-2017/

### 24.04.2017 10:15 Pierre-Antoine Absil (University of Louvain, Belgium):Optimization on manifolds: methods and applicationsMI 02.06.011 (Boltzmannstr. 3, 85748 Garching)

Dates, times and rooms in detail: https://igdk1754.ma.tum.de/IGDK1754/CCAbsil2017

Optimization on manifolds is now a well established research field. The first developments can be traced back to the 1970s, and the area has been very active for the past few years. Optimization on manifolds is concerned with problems that can be formulated as finding an optimum of a real-valued cost function defined on a smooth nonlinear search space. Oftentimes, the search space is a "matrix manifold" (or more generally a "tensor manifold"), in the sense that its points admit natural representations in the form of matrices. In most cases, the matrix manifold structure is due either to the presence of certain nonlinear constraints (such as orthogonality or rank constraints), or to invariance properties in the cost function that need to be factored out in order to obtain a nondegenerate optimization problem. Manifolds that come up in practical applications include the rotation group SO(3) (generation of rigid body motions from sample points), the set of fixed-rank matrices (low-rank models, e.g., in collaborative filtering), the set of 3x3 symmetric positive-definite matrices (interpolation of diffusion tensors), and the shape manifold (morphing). The practical importance of optimization problems on manifolds has stimulated the development of geometric optimization algorithms that exploit the differential structure of the manifold search space. This course will give an overview of geometric optimization algorithms and their applications, with an emphasis on the underlying geometric concepts and on the numerical efficiency of the algorithm implementations. The course will end with recent developments related to curve fitting and nonsmooth optimization on manifolds. The second day will include computer exercises. Computers with Matlab are available in the seminar room, or you can bring your own laptop with Matlab installed.

### 24.04.2017 12:30 Ehud Kalai (Northwestern University):Large Dynamic Interaction: Uncertain Fundamentals and Noisy Public Information (@Micro Workshop)301 (Ludwigstraße 28, 80539 München)

More information at http://www.et.econ.uni-muenchen.de/studium_lehre/microworkshop/index.html

Biography: Ehud Kalai is a prominent American game theorist and mathematical economist known for his contributions to the field of game theory and its interface with economics, social choice, computer science and operations research. He is the James J. O’Connor Distinguished Professor of Decision and Game Sciences at Northwestern University, where he has taught since 1975. (https://en.wikipedia.org/wiki/Ehud_Kalai)

### 24.04.2017 13:00 Dr. Manuel Gnann (TUM):Stability of receding traveling waves in viscous thin filmsMI 03.06.011 (Boltzmannstr. 3, 85748 Garching)

We consider a thin-film equation with linear mobility and zero contact angle at the free boundary, that is, at the contact line where liquid, gas, and solid meet. Previous results on stability and well-posedness of this equation have focused on perturbations of equilibrium-stationary or self-similar profiles, the latter eventually wetting the whole surface. These solutions have their counterparts for the second-order porous-medium equation. Both porous-medium and thin-film equation are degenerate-parabolic, but the porous-medium equation additionally fulfills a comparison principle while the thin-film equation does not.

In this talk, we consider receding traveling waves describing de-wetting, a phenomenon genuinely linked to the fourth-order nature of the thin-film equation and not encountered in the porous-medium case as it violates the comparison principle. The linear stability analysis leads to a linear fourth-order degenerate-parabolic operator for which we prove maximal-regularity estimates with arbitrary regularity in a right-neighborhood of the contact line. This leads to a well-posedness and stability result for the corresponding nonlinear equation. As the linearized evolution has different scaling as at the contact line and in the bulk, the analysis is more intricate than in related previous works. We believe that our analysis is a natural step towards investigating other situations in which the comparison principle is violated, such as rupture of droplets.

The talk is based on joint work with Slim Ibrahim (University of Victoria, BC) and Nader Masmoudi (Courant Institute, NYU).

### 24.04.2017 16:30 Prof. Dr. Ewa Damek (Wroclaw):Affine stochastic equation with triangular matrices2.01.10 (Parkring 11, 85748 Garching-Hochbrück)

We consider affine stochastic equation X=AX+B, where A is an upper triangular matrix, X and B are vectors, X is independent of (A,B) and the equation is meant in law. Under appropriate assumptions X has a heavy tail, but unlike the Kesten situation the tails of components X_1,..., X_d of X decay with various speed. What is more interesting not only the exponents may be different but also non trivial slowly varying functions may appear in the asymptotics.

### 25.04.2017 15:00 Stefan Dohr (TU Graz):Space-time boundary element methods for the heat equation (Werner-Heisenberg-Weg 39, 85577 Neubiberg)

In this talk we describe the boundary element method for the discretization of the time-dependent heat equation. In contrast to standard time-stepping schemes we consider an arbitrary decomposition of the boundary of the space-time cylinder into boundary elements. Besides adaptive refinement strategies this approach allows us to parallelize the computation of the global solution of the whole space-time system. In addition to the analysis of the boundary integral operators and the derivation of boundary element methods for the Dirichlet initial boundary value problem we state convergence properties and error estimates of the approximations. Those estimates are based on the approximation properties of boundary element spaces in anisotropic Sobolov spaces. The systems of linear equations are solved with the GMRES method. For an efficient computation of the solution we need preconditioners. Based on the mapping properties of the single layer and the hypersingular boundary integral operator we construct a preconditioner for the discretization of the first boundary integral equation. Moreover we describe the basic idea of the FEM-BEM coupling method for parabolic transmission problems. The theoretical results are confirmed by numerical tests.

### 27.04.2017 16:30 Manfred Lehn:Der Satz von Grothendieck-Brieskorn-Slodowy und symplektische SingularitätenA 027 (Theresienstr. 39, 80333 München)

Dynkindiagramme tauchen bekanntlich bei der Klassifikation von Liealgebren auf, aber auch in der Darstellungstheorie von endlichen Gruppen und Köcheralgebren oder in der Theorie der einfachen Flächensingularitäten. Der klassischen Satz von Brieskorn und Slodowy stellt einen direkten Zusammenhang zwischen Liealgebren und Flächensingularitäten her. Ich möchte die geometrische Idee an einem ausführlichen Beispiel erläutern und anschließend auf Ergebnisse einer gemeinsamen Arbeit mit Yoshinori Namikawa, Christoph Sorger und Duco van Straten eingehen, in der wir den Satz von Grothendieck-Brieskorn-Slodowy durch die Berücksichtigung von Poissonstrukturen erheblich erweitern können.

Alle Interessierten sind hiermit herzlich eingeladen. Eine halbe Stunde vor dem Vortrag gibt es Kaffee und Tee im Sozialraum (Raum 448) im 4. Stock.

Treffpunkt zum Abendessen um 18.00 Uhr wird noch bekannt gegeben.