WIAS-Doktorand(inn)enseminar

Welcome to the website of the self-organized seminar of the PhD-students at WIAS. The seminar provides a platform for the PhD-students of the WIAS (and alumni) to give talks on their research and present themselves and their work to colleagues. The seminar is also open for minicourses on math, science and tutorials on scientific software packages.
You're cordially invited to contribute to the WIAS PhD-Seminar! Please don't hesitate to contact one of the organizers.

  • Place: Weierstrass-Institute for Applied Analysis and Stochastics
    Place: Mohrenstraße 39, 10117 Berlin
    Place: Weierstrass Lecture Room (WIAS-406)
  • Time: Mondays, 2:00PM - 3:00PM
  • Organizers: Laura Blank, Sebastian Eydam, Markus Kantner
Upcoming talks
22.11.2018 Markus Mittnenweig (RG 1)

Thursday!

Entropy methods for quantum and classical evolution equations

Previous talks
27.08.2018 Clemens Bartsch (RG 3)

Post-quantum cryptography and the first quantum-safe digital signature scheme

Abstract:
In May 2018 news spread far beyond the cryptologist community: a group of German, Dutch and American computer scientists had published the first quantum-resilient digital signature scheme as an internet standard (RFC 8391), thus taking a major step towards arming digital signature against future attacks with quantum computers. The proposed XMSS scheme (eXtended Merkle Signature Scheme) makes use of cryptographic hash functions, which are considered quantum-safe. In this talk we want to lead the audience towards an understanding of the importance and mode of operation of digital signature schemes, the threat that quantum computers might in the near future pose to them, and how the newly standardized scheme offers resilience against quantum computer attacks. We will start with a general introduction of digital signature and an explanation of a basic version of the widespread RSA algorithm and its major weaknesses, focusing on factorization attacks. Then we will introduce the basics of quantum computing, show how Shor's algorithm enables them to very efficiently perform factorization attacks, thus breaking RSA, and finally introduce XMSS and give an explanation for why it is supposed to be safe against quantum-aided attacks. Code examples and examples of quantum computations performed with a prototypical 5-qubit processor (IBM Q Experience) will be included in the talk.

19.02.2018 Thomas Frenzel (RG 1)

Working with Wasserstein gradient flows

Abstract:
This talk explains what the Wasserstein distance is, how it generates a gradient flow for the heat equation and how to pass to the limit in a sandwich model with thin plates.

19.06.2017 Artur Stephan (Guest of RG 1)

starts at 1:00 PM

On approximations of solutions of evolution equations using semigroups

Abstract:
In the talk, some results of my master thesis will be discussed. We approximate the solution of a non-autonomous linear evolution equation in the operator-norm topology. The approximation is derived using the Trotter product formula and can be estimated. As an example, we consider the diffusion equation perturbed by a time dependent potential.

12.06.2017 Clemens Bartsch (RG 3)

starts at 11:00 AM

A mixed stochastic-numeric algorithm for transported interacting particles

Abstract:
A coupled system of population balance and convection-diffusion equations is solved numerically, employing stochastic and finite element techniques in combination. While the evolution of the particle population is modelled as a Markov jump process and solved with a stochastic simulation algorithm, transport of temperature and species concentration are subject to a finite element approximation. We want to briefly introduce both the stochastic and the deterministic approach and discuss some difficulties to overcome when combining them. A proof of concept simulation of a flow crystallizer in 2D is presented.

08.05.2017 Sibylle Bergmann (RG 7)

An atomistically informed phase-field model for describing the solid-liquid interface kinetics in silicon

Abstract:
An atomistically informed parametrization of a phase-field model for describing the anisotropic mobility of liquid-solid interfaces in silicon is presented. The model is derived from a consistent set of atomistic data and thus allows to directly link molecular dynamics and phase field simulations. Expressions for the free energy density, the interfacial energy and the temperature and orientation dependent interface mobility are systematically fitted to data from molecular dynamics simulations based on the Stillinger-Weber interatomic potential. The temperature-dependent interface velocity follows a Vogel-Fulcher type behavior and allows to properly account for the dynamics in the undercooled melt.
Our three dimensional simulations reproduce the expected physical behavior of a silicon crystal in a melt, e.g. the critical nucleation radius and the experimentally observed equilibrium shape.

24.10.2016 Johannes Neumann (RG 4)

The phase field approach for topology optimization

Abstract:
In this talk I will present an approach on topology optimization based on the phase field model from [Blank et. al., 2014] which utilizes the Allan-Cahn gradient flow. This method natively includes changes to the topology during the optimization and replaces sharp interfaces with boundary layers for smoothness. Instead of the prime-dual active set method a Lagrangian approach is considered.

10.10.2016 Swetlana Giere (RG 3)

A Walk to a Random Forest

05.09.2016 Alexander Weiß (GetYourGuide: Head of Data Science)

Talk on professional experience in the field of data science

22.08.2016 Michael Hofmann (RG 2)

Einfluss dynamischer Resonanzen auf die Wechselwirkung optischer Femtosekunden-Pulse mit transparenten Dielektrika

27.06.2016 Florian Eichenauer (RG 1)

starts at 4:00 PM

Analysis for Dissipative Maxwell-Bloch Type Models

20.06.2016 Paul Helly (Guest of RG 1)

A structure-preserving finite difference scheme for the Cahn-Hilliard equation

25.01.2016 Alena Moriakova (Guest of RG 2)

Analysis of periodic solutions of the Mackey-Glass equation

Abstract:
The Mackey-Glass equation is the nonlinear time delay differential equation, which describes the formation of white blood cells. We study the possibility of simultaneous existence of several stable attractors (periodic solutions) in this equation. As a research method we use method of uniform normalization.

11.01.2016 Thomas Frenzel (RG 1)

(Evolutionary) Gamma-Convergence and micro-macro limits

23.11.2015 Sina Reichelt (RG 1)

Two-scale homogenization of systems of nonlinear parabolic equations

Abstract:
We consider two different classes of systems of nonlinear parabolic equations, namely, reaction-diffusion systems and Cahn-Hilliard-type equations. While the latter class admits a gradient structure, the former does in general not admit one. The equation's coefficients are periodically oscillating with a period which is proportional to the characteristic microscopic length scale. Using the method of two-scale convergence, we rigorously derive effective (upscaled or homogenized) equations for the limit of smaller and smaller periods. Therefore, depending on the class of systems under consideration, we use either suitable Gronwall-type estimates (for Lipschitz continuous reaction terms) or Gamma-convergence (for energy functionals).

09.11.2015 Mayya Zhilova (RG 6)

Bootstrap confidence sets under model misspecification

26.10.2015 Dmitry Puzyrev (RG 1)

starts at 10:00 AM (Erhard-Schmidt lecture room)

Delay Induced Multistability and Zigzagging of Laser Cavity Solitons

21.09.2015 Clemens Bartsch (RG 3)

starts at 2:30 PM

An Assessment of Solvers for Saddle Point Problems Emerging from the Incompressible Navier-Stokes equations