Upcoming Events
- Wednesday, 07.05.2025, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
Lukas Lüchtrath, Wias Berlin:
The effects of strong clustering in spatial random graphs
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
We consider general percolation models, where edges of unbounded length are present but rare. This can be seen as a measurement for spatially induced clustering. We give a brief overview of recent results about the graph properties of these models and extensively study the contact process on one-dimensional instances of these graphs. The latter will lead to some ongoing projects and open problems. Based on joint work with Emmanuel Jacob, Benedikt Jahnel und Christian Mönch.
Further Informations
Seminar Interactin Random Systems
Host
WIAS Berlin
- Wednesday, 07.05.2025, 14:15 (WIAS-405-406)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Prof. Dr. Edriss Titi, University of Cambridge, UK and Texas A&M University, USA:
On a generalization of the Bardos--Tartar conjecture to nonlinear dissipative PDEs
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
In this talk I will show that every solution of a KdV-Burgers--Sivashinsky type equation blows up in the energy space, backward in time, provided the solution does not belong to the global attractor. This is a phenomenon contrast to the backward behavior of the 2D Navier--Stokes equations, subject to periodic boundary condition, studied by Constantin, Foias, Kukavica and Majda, but analogous to the backward behavior of the Kuramoto--Sivashinsky equation discovered by Kukavica and Malcok. I will also discuss the backward behavior of solutions to the damped driven nonlinear Schrödinger equation, the complex Ginzburg--Landau equation, and the hyperviscous Navier--Stokes equations. In addition, I will provide some physical interpretation of various backward behaviors of several perturbations of the KdV equation by studying explicit cnoidal wave solutions. Furthermore, I will discuss the connection between the backward behavior and the energy spectra of the solutions. The study of backward behavior of dissipative evolution equations is motivated by a conjecture of Bardos and Tartar which states that the solution operator of the two-dimensional Navier--Stokes equations maps the phase space into a dense subset in this space.
Further Informations
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Wednesday, 14.05.2025, 10:00 (WIAS-HVP-3.13)
- Forschungsseminar Mathematische Statistik
Prof. Dr. Vladimir Spokoiny, WIAS Berlin:
Estimation and classification for DNN: Bless of dimension
more ... Location
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13
Further Informations
Dieser Vortrag findet hybrid statt. Die Teilnahme per Zoom ist über den (neuen!) Link: https://hu-berlin.zoom-x.de/j/62476510180?pwd=1bws9DORlDM2Iub3ANrb7zzDNANvsJ.1
Host
Humboldt-Universität zu Berlin
Universität Potsdam
WIAS Berlin
- Wednesday, 14.05.2025, 14:00 (WIAS-405-406)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Prof. Dr. Pierluigi Colli, Università di Pavia, Italien:
Solvability and optimal control in spatially structured epidemic models
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
Compartmental models are widely used in the mathematical modeling of infectious diseases, where the population is divided into distinct groups or compartments based on disease status. In this talk, we present results - obtained in collaboration with various co-authors - related to compartmental epidemic models that evolve within spatially heterogeneous environments. These models lead to nonlinear systems of reaction-diffusion partial differential equations, subject to homogeneous Neumann boundary conditions and appropriate initial conditions. Particular attention is given to a class of models incorporating a modified chemotaxis-type term, reflecting movement influenced by spatial infection gradients. We will discuss existence and uniqueness of solutions, and outline some optimal control problems.
Further Informations
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Wednesday, 14.05.2025, 15:30 (WIAS-405-406)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Ass. Prof. Andrea Signori, Politecnico di Milano, Italien:
Mathematical models of active phase separation and droplet dynamics
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
Active phase separation gives rise to striking phenomena, such as the suppression of coarsening and the spontaneous growth and division of droplets, that sharply contrast with the behavior seen in classical systems. Whereas classical phase separation favors the growth of larger domains at the expense of smaller ones, chemically active mixtures can sustain a stable population of droplets with finite size. These dynamics have been proposed as a model for protocells, shedding light on the emergence of self-organized prebiotic structures and the transition from non-living to living matter. In this talk, I will present a mathematical framework for modeling the dynamics of active droplets, using both the phase-field formulation (via the Cahn--Hilliard equation) and the sharp-interface limit (described by the Mullins--Sekerka free-boundary problem). I will explore the connection between these two approaches and discuss the well-posedness and stability of the resulting models, focusing on planar and radial configurations. Finally, I will present numerical simulations that support the asymptotic analysis and highlight complex behaviors such as droplet division and shell formation.
Further Informations
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Thursday, 15.05.2025, 14:00 (WIAS-405-406)
- Seminar Numerische Mathematik
Dr. Peter Munch, Technische Universität Berlin:
The deal.II finite-element library: recent developments and applications
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
deal.II is an open-source general-purpose finite-element C++ library with origins at the University of Heidelberg in 1997. Since then, it has evolved into a mature and worldwide developed and used mathematical software library (including at WIAS and TU Berlin). It is the basis of applications ranging from traditional application fields like computational solid mechanics, fluid mechanics, biomechanics, and geosciences to more ?exotic? fields of research such as quantum and plasma physics. The scalability of deal.II has been shown by solving partial differential equations with trillions of unknowns on 300k processes. For its outstanding contributions to the development and use of mathematical and computational tools and methods for the solution of science and engineering problems, deal.II was awarded the prestigious ?SIAM/ACM Prize in Computational Science and Engineering 2025?. In this talk, we will give a short introduction into deal.II, discuss recent developments in the library and present new use cases.
Further Informations
Seminar Numerische Mathematik
Host
WIAS Berlin
- Monday, 19.05.2025, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
Peter Gracar, University of Leeds:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Further Informations
Seminar Interacting Random Systems
Host
WIAS Berlin
- Wednesday, 21.05.2025, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
Adrian Röllin, National University of Singapore:
Centered Subgraph Counts in Dense Random Graphs
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
Complex networks appear in many fields, from social media to biology, and understanding their structure often boils down to studying how frequently small subgraphs (such as triangles or squares) appear. In this talk, I will introduce the idea of centered subgraph counts: a way of measuring subgraph occurrences that corrects for the dependence that we observe among regular subgraph counts. By focusing on these centered counts, we can describe and quantify the natural 'fluctuations' in dense random networks via tools first developed by Janson and Nowicki in the study of generalised U-statistics in the 90s. I will explain how these theoretical results lead to practical methods for assessing how well a given network fits a chosen statistical model--often referred to as a goodness-of-fit analysis.
Further Informations
Seminar Interactin Random Systems
Host
WIAS Berlin
- Wednesday, 21.05.2025, 14:15 (WIAS-ESH)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
PD Dr. Olaf Klein, WIAS Berlin:
Uncertainty quantification for a model for a magnetostrictive material involving a hysteresis operator
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
WIAS Berlin
Humboldt-Universität zu Berlin
Freie Universität Berlin
- Thursday, 22.05.2025, 10:00 (WIAS-ESH)
- Berlin Oberseminar: Optimization, Control and Inverse Problems
Prof. Michael Hinze, Universität Koblenz:
Shape optimization with Lipschitz methods (joint work with Klaus Deckelnick (Magdeburg) and Philip Herbert (Sussex))
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstract
We present a general shape optimisation framework based on the method of mappings in the Lipschitz topology. We propose and numerically analyse steepest descent and Newton-like minimisation algorithms for the numerical solution of the respective shape optimisation problems. To illustrate our approach we present a selection of PDE constrained shape optimisation problems and compare our findings to results from so far classical Hilbert space methods and recent p-approximations.
Further Informations
Berlin Oberseminar: Optimization, Control and Inverse Problems
Host
WIAS Berlin
- Thursday, 22.05.2025, 14:00 (WIAS-ESH)
- Halbleiterseminar
Prof. Band Ram, Mathematics Department, Technion Israel Institute of Technology:
Universality of the band-gap density - From periodic graphs to laminates
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstract
The spectrum of periodic objects has a band-gap structure. We show that such a spectrum can be described in terms of a linear flow on a torus. This characterization is valid for various periodic structures, from quantum graphs to wave propagation in elastic laminates. Using this approach allows us to prove universal properties of the band-gap density and obtain many useful spectral characteristics.
Host
WIAS Berlin
- Thursday, 22.05.2025, 14:00 (WIAS-405-406)
- Seminar Numerische Mathematik
Dr. Holger Stephan:
Improvement of the diffusion equation using hyperbolic systems and memory equations
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
The diffusion equation is the simplest equation to describe the motion of a particle in a random medium. It is the 0th moment (mass balance) of the more exact kinetic equation (Kramers equation). Higher momentum approximations such as the 1st momentum (momentum balance) and the 2nd momentum (energy balance) are also common. Moment approximations must be closed. We calculate the optimal approximations for various higher moment systems for the case of no external potential. This leads to hyperbolic systems which, as is well known, are difficult to solve numerically. However, systems of diffusion equations with memory terms can be derived from them without loss of information. These can also be converted into common systems of diffusion equations also without loss of information using a recently developed method, which can be solved numerically very well. The result is a much more precise description of the diffusion process.
Host
WIAS Berlin
- Tuesday, 27.05.2025, 15:00 (WIAS-ESH)
- Forschungsseminar Mathematische Modelle der Photonik
Prof. Dmitry Turaev, Imperial College London, GB:
TBA
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Further Informations
Forschungsseminar Mathematische Modelle der Photonik
Host
WIAS Berlin
- Wednesday, 04.06.2025, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
Elena Pulvirenti, Delft University of Technology:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Further Informations
Seminar Interacting Random Systems
Host
WIAS Berlin
- Thursday, 05.06.2025, 14:00 (WIAS-405-406)
- Seminar Numerische Mathematik
Adrian Hill, TU Berlin:
SparseConnectivityTracer.jl
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Host
WIAS Berlin
- Wednesday, 11.06.2025, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
Michiel Renger, Technische Universität München:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Further Informations
Seminar Interacting Random Systems
Host
WIAS Berlin
- June 23 – 26, 2025 (Harnack-Haus)
- Workshop/Konferenz: 4th Annual Conference of SPP 2265 Random Geometric Systems 2025
more ... Location
Harnack-Haus -- Tagungsstätte der Max-Planck-Gesellschaft
Host
WIAS Berlin
- Wednesday, 09.07.2025, 14:15 (WIAS-ESH)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Prof. Dr. Amru Hussein, Universität Kassel:
The three limits of the hydrostatic approximation
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstract
The primitive equations are a large scale model for ocean and atmosphere. Formally, they are derived from the 3D-Navier--Stokes equations by the assumption of a hydrostatic balance. This can be formalized by a rescaling procedure on an $varepsilon$-thin domain where one considers anisotropic viscosities with vertical viscosity $varepsilon^gamma$ and $varepsilon$-independent horizontal viscosity. Now, the choice of the order $gamma$ leads to different limit equations:
For $gamma=2$, one obtains the primitive equations with full viscosity term $-Delta$;
For $gamma>2$, one obtains the primitive equations with only horizontal viscosity term $- Delta_H$;
For $gamma <2$, one obtains the 2D Navier-Stokes equations.
Thus, there are three possible limits of the hydrostatic approximation depending on the assumption on the vertical viscosity. Here, we show how maximal regularity methods and quadratic inequalities - reminiscent of the Fujita-Kato methods - can be an efficient approach to prove norm-convergences in all three cases. This is a joint work with Ken Furukawa, Yoshikazu Giga, Matthias Hieber, Takahito Kashiwabara, and Marc Wrona, see https://arxiv.org/abs/2312.03418 for a preprint.
Further Informations
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- September 29 – October 1, 2025 (WIAS-ESH)
- Workshop/Konferenz: Mathematical Analysis of Fluid Flows by Variational Methods
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
Freie Universität Berlin
Universität Leipzig
WIAS Berlin
- October 15 – 17, 2025 (WIAS-ESH)
- Workshop/Konferenz: Recent Developments in Spatial Interacting Random Systems
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
WIAS Berlin