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Monday, 16.10.2017, 14.00 Uhr (WIAS-ESH)
INSTITUTSKOLLOQUIUM
Dr. S. Amiranashvili, WIAS:
Negative frequency radiation in optical fibers
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
Tuesday, 17.10.2017, 15.00 Uhr (WIAS-ESH)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. A. Suvorikova, WIAS Berlin:
Two-sample test based on 2-Wasserstein distance
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
Tuesday, 17.10.2017, 15.15 Uhr (FU-140)
Oberseminar Nonlinear Dynamics
Dr. J. Sieber, University of Exeter, UK:
Smooth center manifolds for delay-differential equations
more ... Location
Freie Universität Berlin, Arnimallee 7, 14195 Berlin, Hinterhaus, Raum: 140

Abstract
Delay-differential equations (DDEs) with state-dependent delays are, as far as is known, at best continuously differentiable once as dynamical systems. That is, the time-t map does not depend on its argument with a higher degree of smoothness than 1. However, as I will show, center manifolds near equilibria are still as smooth as expected from the spectral gap and from the smoothness of coefficients. In particular, I will review what precisely ßmoothness of coefficients" means.

Host
Freie Universität Berlin
WIAS Berlin
Wednesday, 18.10.2017, 10.00 Uhr (WIAS-ESH)
Forschungsseminar Mathematische Statistik
Prof. Dr. V. Spokoiny, WIAS Berlin:
Big ball probability with applications in statistical inference
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
We derive the bounds on the Kolmogorov distance between probabilities of two Gaussian elements to hit a ball in a Hilbert space. The key property of these bounds is that they are dimensional-free and depend on the nuclear (Schatten-one) norm of the difference between the covariance operators of the elements. We are also interested in the anticoncentration bound for a squared norm of a non-centered Gaussian element in a Hilbert space. All bounds are sharp and cannot be improved in general. We provide a list of motivation examples and applications in statistical inference for the derived results as well. (joint with Götze, Naumov and Ulyanov)

Host
WIAS Berlin
Humboldt-Universität zu Berlin
Universität Potsdam
Thursday, 19.10.2017, 14.00 Uhr (WIAS-ESH)
Seminar Numerische Mathematik
Prof. L. Rebholz, Clemson University, USA:
On conservation laws of Navier--Stokes Galerkin discretizations
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
We study conservation properties of Galerkin methods for the incompressible Navier-Stokes equations, without the divergence constraint strongly enforced. In typical discretizations such as the mixed finite element method, the conservation of mass is enforced only weakly, and this leads to discrete solutions which may not conserve energy, momentum, angular momentum, helicity, or vorticity, even though the physics of the Navier-Stokes equations dictate that they should. We aim in this work to construct discrete formulations that conserve as many physical laws as possible without utilizing a strong enforcement of the divergence constraint, and doing so leads us to a new formulation that conserves each of energy, momentum, angular momentum, enstrophy in 2D, helicity and vorticity (for reference, the usual convective formulation does not conserve most of these quantities). Several numerical experiments are performed, which verify the theory and test the new formulation.

Host
WIAS Berlin