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Date Time Venue Talk
12/12/19 02:00 pm Am Schwarzenberg-Campus 3 (E), Room 3.074 TBA
Philipp Neumann, Helmut-Schmidt-Universität
11/28/19 02:00 pm Am Schwarzenberg-Campus 3 (E), Room 3.074 TBA
Vincent Griem
11/26/19 05:00 pm Am Schwarzenberg-Campus 5 (H), Room H0.10 Two-scale convergence for evolutionary equations
Marcus Moppi Waurick, Department of Mathematics and Statistics, University of Strathclyde, Livingstone Tower, 26 Richmond Street, Glasgow G1 1XH, Scotland, Room number: LT1007

In the talk, we shall develop a general framework for the treatment of both deterministic and stochastic homogenisation problems for evolutionary equations. The versatility of the methods allow the unified treatment of static, dynamic as well as mixed type problems.
11/21/19 02:00 pm Am Schwarzenberg-Campus 3 (E), Room 3.074 Parallel-in-time integration with PFASST: from prototyping to applications
Robert Speck, Jülich Supercomputing Centre, Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428 Jülich

The efficient use of modern supercomputers has become one of the key challenges in computational science. New mathematical concepts are needed to fully exploit massively parallel architectures. For the numerical solution of time-dependent processes, time-parallel methods have opened new ways to overcome scaling limits. With the "parallel full approximation scheme in space and time" (PFASST), multiple time-steps can be integrated simultaneously. Based on spectral deferred corrections (SDC) methods and nonlinear multigrid ideas, PFASST uses a space-time hierarchy with various coarsening strategies to maximize parallel efficiency. In numerous studies, this approach has been used on up to 448K cores and coupled to space-parallel solvers with finite differences, spectral methods or even articles for discretization in space. Yet, since the integration of SDC or PFASST into an existing application code is not straightforward and the potential gain is typically uncertain, we will present in this talk our Python prototyping framework pySDC. It allows to rapidly test new ideas and to implement first toy problems more easily. We will also discuss the transition from pySDC to application-specific implementations and show recent use cases.
11/14/19 02:00 pm Am Schwarzenberg-Campus 3 (E), Room 3.074 Where are my ions? A new algorithms to track fast ions in the magnetic field of a fusion reactor
Daniel Ruprecht, TUHH, Institut für Mathematik, Lehrstuhl für Computational Mathematics, Am Schwarzenberg-Campus 3, Gebäude E, 21073 Hamburg

The plasma in a fusion reactor is heated by neutral beam injection: injecting high energy neutrons which quickly ionize and swirl around in the reactor's magnetic fiel. Modelling this process requires solving the Lorentz equations numerically over long times (up to a second) with very small time steps (order of nanoseconds), which means very many time steps and thus long simulation times (from days up to a week). The talk will introduce GMRES-Boris-SDC (GBSDC), a new time stepping algorithm that can reduce computational cost compared to the currently used Boris method. The method is a potpourri of various numerical techniques, including the GMRES linear solver, spectral deferred corrections, the velocity Verlet scheme and the Boris trick. I will describe the algorithm and show examples of its performance for benchmarks with varying degree of realism.

This is joint work with Dr Krasymyr Tretiak, School of Mathematics, University of Leeds.
10/24/19 02:00 pm Am Schwarzenberg-Campus 3 (E), Room 3.074 Observability Estimates in Banach Spaces and Applications
Dennis Gallaun

In this talk we study sufficient conditions for obserability of systems in Banach spaces. In an abstract Banach space setting we show that an uncertainty relation together with a dissipation estimate implies an observability estimate with explicit dependence on the model parameters. Our approach unifies and generalizes the respective advantages from earlier results obtained in the context of Hilbert spaces. As an application we consider elliptic operators on Lp spaces. Combined with the well-known relation between observability and controllability we derive sufficient conditions for null-controllability and bounds on the control cost.
The talk is based on joint work with Christian Seifert and Martin Tautenhahn.
10/17/19 02:00 pm Am Schwarzenberg-Campus 3 (E), Room 3.074 Extension of vector-valued functions and weak-strong principles
Karsten Kruse

We give a unified approach to handle the problem of extending functions with values in a locally convex Hausdorff space $E$ over the field $\mathbb{K}=\mathbb{R}$ or $\mathbb{C}$, which have weak extensions in a space $\mathcal{F}(\Omega,\mathbb{K})$ of scalar-valued functions on a set $\Omega$, to functions in a vector-valued counterpart $\mathcal{F}(\Omega,E)$ of $\mathcal{F}(\Omega,\mathbb{K})$. The main tool is the representation of vector-valued functions as linear continuous operators.
09/25/19 10:30 am Am Schwarzenberg-Campus 3 (E), Room 3.074 Stabilität gewöhnlicher Differentialgleichungen (Bachelorarbeit)
Patrizia Hermann
09/23/19 02:00 pm Am Schwarzenberg-Campus 3 (E), Room 3.074 Erkennung und Vorhersage von Meinungsbildern anhand neuronaler Netze (Bachelorarbeit)
Nesrine Zarrouki
09/09/19 03:00 pm Room H0.03 Application of Hierarchical Matrices to Scattered Data Interpolation [Promotionsvortrag]
Michael Wende