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Place:
Weierstrass-Institute for Applied Analysis and Stochastics
Place:
Mohrenstraße 39, 10117 Berlin
Place:
Weierstrass Lecture Room (WIAS-406)
Place:
Online, contact the organizers for credentials
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Time:
Every second Monday of the month, 2:00PM - 3:00PM
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Organizers:
Moritz Ebeling-Rump,
Derk Frerichs
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Upcoming talks |
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08.02.2021 |
David Sommer (RG 4)
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TBA
Abstract:
TBA.
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08.03.2021 |
Leonie Schmeller (RG 7)
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TBA
Abstract:
TBA.
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12.04.2021 |
Heide Langhammer (RG 5)
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TBA
Abstract:
TBA.
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10.05.2021 |
Dilara Abdel (LG 3)
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TBA
Abstract:
TBA.
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14.06.2021 |
Lasse Ermoneit (RG 2)
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TBA
Abstract:
TBA.
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Previous talks |
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11.01.2021 |
Alexandra Quitmann (RG 5)
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Spin systems and random loops
Abstract:
Random loop models are systems of statistical mechanics whose
configurations can be viewed as collections of closed loops living in
higher dimensional space. They are interesting objects on its own and
further have a close connection to other important statistical mechanics
models such as spin systems. In this talk, I will introduce random loop
models, discuss a conjecture about the occurrence of macroscopic loops
and explain its role as alternative formulation of spin systems.
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07.12.2020 |
Moritz Ebeling-Rump
(RG 4)
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Topology Optimization subject to a Local Volume Constraint
Abstract:
The industry sector of additive manufacturing has shown remarkable
growth in previous years and is predicted to continue growing at a rate
of 15% in the coming years. It progressed from prototyping to actual
production. Topology Optimization and Additive Manufacturing have been
called a "match made in heaven", because Topology Optimization
can aid engineers to take advantage of the newfound design freedom.
Commonly a perimeter term is incorporated which avoids checker-boarding,
but also counteracts the desired creation of infill structures. By
incorporating a local volume constraint mesoscale holes are introduced.
Analytically, the existence of unique solutions is shown. Apart from
better cooling properties and a larger resilience to local material
damage, these structures demonstrate an improved nonlinear material
behavior. One observes an increased critical buckling load
- a potentially catastrophic failure mode that would not be taken into
account if only considering linear elasticity.
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11.11.2020 |
Derk Frerichs
(RG 3)
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The very basics of numerical analysis - or what am I doing here when I'm
not drinking coffee?
Abstract:
When we drink coffee, caffeine spreads in our body through our blood.
The flow of particles inside a media, e.g. the caffeine inside the
blood, can be described with the so called convection-diffusion-reaction
equations that are often approximated using numerical algorithms. In
this talk the basic concepts of numerical analysis are explained with
the help of a conforming Courant finite element discretization of the
convection-diffusion-reaction equations. Afterwards a short outlook is
given that explains my current research activities.
Numerical examples round up the presentation.
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22.11.2018 |
Markus Mittnenweig (RG 1)
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Entropy methods for quantum and classical evolution equations
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27.08.2018 |
Clemens Bartsch (RG 3)
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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.
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19.02.2018 |
Thomas Frenzel (RG 1)
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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.
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19.06.2017 |
Artur Stephan (Guest of RG 1)
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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.
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12.06.2017 |
Clemens Bartsch (RG 3)
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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.
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08.05.2017 |
Sibylle Bergmann (RG 7)
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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.
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24.10.2016 |
Johannes Neumann (RG 4)
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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.
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10.10.2016 |
Swetlana Giere (RG 3)
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A Walk to a Random Forest
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05.09.2016 |
Alexander Weiß (GetYourGuide: Head of Data Science)
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Talk on professional experience in the field of data science
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22.08.2016 |
Michael Hofmann (RG 2)
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Einfluss dynamischer Resonanzen auf die Wechselwirkung optischer Femtosekunden-Pulse mit transparenten Dielektrika
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27.06.2016 |
Florian Eichenauer (RG 1)
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starts at 4:00 PM |
Analysis for Dissipative Maxwell-Bloch Type Models
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20.06.2016 |
Paul Helly (Guest of RG 1)
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A structure-preserving finite difference scheme for the Cahn-Hilliard equation
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25.01.2016 |
Alena Moriakova (Guest of RG 2)
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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.
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11.01.2016 |
Thomas Frenzel (RG 1)
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(Evolutionary) Gamma-Convergence and micro-macro limits
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23.11.2015 |
Sina Reichelt (RG 1)
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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).
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09.11.2015 |
Mayya Zhilova (RG 6)
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Bootstrap confidence sets under model misspecification
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26.10.2015 |
Dmitry Puzyrev (RG 1)
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starts at 10:00 AM (Erhard-Schmidt lecture room) |
Delay Induced Multistability and Zigzagging of Laser Cavity Solitons
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21.09.2015 |
Clemens Bartsch (RG 3)
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starts at 2:30 PM |
An Assessment of Solvers for Saddle Point Problems Emerging from the Incompressible Navier-Stokes equations
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