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Wednesday, 12.12.2018, 10:00 (WIAS-ESH)
Forschungsseminar Mathematische Statistik
Prof. B. Szabo, Universität Leiden, Niederlande:
On the fundamental understanding of distributed computation
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
In recent years, the amount of available information has become so vast in certain fields of applications that it is infeasible or undesirable to carry out the computations on a single server. This has motivated the design and study of distributed statistical or learning methods. In distributed methods, the data is split amongst different administrative units and computations are carried out locally in parallel to each other. The outcome of the local computations are then aggregated into a final result on a central machine. In this talk we will consider the limitations and guarantees of distributed methods in general under communication constraints (i.e. only limited amount of bits are allowed to be transmitted between the machines) on the random design regression model. We derive minimax lower bounds, matching upper bounds and provide adaptive estimators reaching these limits. This is an ongoing joint work with Harry van Zanten.

Host
Humboldt-Universität zu Berlin
Universität Potsdam
WIAS Berlin
Westfälische Wilhelms-Universität Münster
Wednesday, 12.12.2018, 11:30 (WIAS-406)
Seminar Interacting Random Systems
Prof. Dr. K. Doku-Amponsah, University of Ghana School of Physical and Mathematical Sciences, Ghana, Republik:
Joint large deviation result for empirical measures of the random geometric graphs
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
We prove joint large deviation principle for the empirical pair measure and empirical locality measure of the near intermediate coloured random geometric graph models on n points picked uniformly in the space [0; 1]d; for d 2 N: From this result we obtain large deviation principles for the number of edges per vertex, the degree distribution and the proportion of isolated vertices for the near intermediate random geometric graph models.

Further Informations
Seminar Interacting Random Systems

Host
WIAS Berlin
Wednesday, 12.12.2018, 15:15 (WIAS-ESH)
Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. J. Rehberg, WIAS Berlin:
L bounds for the Neumann problem
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Further Informations
Berliner Oberseminar “Nichtlineare Partielle Differentialgleichungen” (Langenbach Seminar)

Host
WIAS Berlin
Humboldt-Universität zu Berlin
Wednesday, 19.12.2018, 11:30 (WIAS-406)
Seminar Interacting Random Systems
C. Betken, Universität Osnabrück:
Dynamic random graphs: Sedentary random waypoint and preferential attachment models
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Further Informations
Seminar Interacting Random Systems

Host
WIAS Berlin
Thursday, 10.01.2019, 14:00 (WIAS-ESH)
Seminar Numerische Mathematik
Dr. N. Ahmed, Lahore University of Management Sciences, Pakistan:
Numerical comparisons of finite element stabilized methods for a 2D vortex dynamics simulation at high Reynolds number
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
In this talk, I will present an up-to-date and classical Finite Element (FE) stabiliz ed methods for time-dependent incompressible flows. All studied methods belong to the Variational MultiScale (VMS) framework. So, different realizations of stabilized FE-VMS methods are compared in a high Reynolds number vortex dynamics simulation. In particular, a fully Residual-Based (RB)-VMS method is compared with the classical Streamline-Upwind Petrov--Galerkin (SUPG) method together with grad-div stabilization, a standard one-level Local Projection Stabilization (LPS) method, and a recently proposed LPS method by interpolation. These procedures do not make use of the statistical theory of equilibrium turbulence, and no ad-hoc eddy viscosity modeling is required for all methods. Applications to the simulation of a high Reynolds numbers flow with vortical structures on relatively coarse grids are showcased, by focusing on a two-dimensional plane mixing-layer flow. Both Inf-Sup Stable (ISS) and Equal Order (EO) (H^1)-conforming FE pairs are explored, using a second-order semi-implicit Backward Differentiation Formula (BDF2) in time. Based on the numerical studies, it is concluded that the SUPG method using EO FE pairs performs best among all methods. Furthermore, there seems to be no reason to extend the SUPG method by the higher order terms of the RB-VMS method.

Host
WIAS Berlin
Wednesday, 23.01.2019, 11:30 (WIAS-406)
Seminar Interacting Random Systems
P. Houdebert, Aix-Marseille Université, Frankreich:
Sharp phase transition for the Widom-Rowlinson model
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
The Widom-Rowlinson model is formally defined as two homogeneous Poisson point processes forbidding the points of different type to be too close. For this Gibbs model the question of uniqueness/ non-uniqueness depending on the two intensities is relevant. This model is famous because it was the first continuum Gibbs model for which phase transition was proven, in the symmetric case of equal intensities large enough. But nothing was known in the non-symmetric case, where it is conjectured that uniqueness would hold. In a recent work with D. Dereudre (Lille), we partially solved this conjecture, proving that for large enough activities the phase transition is only possible in the symmetric case of equal intensities. The proof uses percolation and stochastic domination arguments.

Further Informations
Seminar Interacting Random Systems

Host
WIAS Berlin