Upcoming Events (Archive)
- Wednesday, 15.01.2025, 10:00 (WIAS-ESH)
- Forschungsseminar Mathematische Statistik
Xiaorui Zuo, National University of Singapore , Singapur:
Cryptos have rough volatility and correlated jumps
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
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, 04.12.2024, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
Günter Last, Karlsruher Institut für Technologie:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Host
WIAS Berlin
- Wednesday, 20.11.2024, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
Júlia Komjáthy, TU Delft:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Host
WIAS Berlin
- Tuesday, 19.11.2024, 13:30 (WIAS-406)
- Seminar Materialmodellierung
Angeliki Koutsimpela, Universität Augsburg:
Mean-field limits for interacting particle systems
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)
Host
WIAS Berlin
- Wednesday, 13.11.2024, 15:15 (WIAS-405-406)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Lukas Abel, Humboldt-Universität zu Berlin:
A scaling law for a model of epitaxial growth with dislocations
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
Epitaxy is a special form of crystal growth and of great importance in modern technology. We consider a crystalline film on a (rigid) substrate. The misfit between the crystal structures of the film and the substrate can lead to dislocations and can have an influence on the morphology of the film. Dislocations are topological defects of the crystallographic lattice. In this talk we will study a variational model from the literature. It is based on linearized elasticity and additionally takes into account the surface energy of the film's free surface as well as the dislocation nucleation energy. In particular we will discuss a new scaling law for the infimum of the energy. This includes a new construction for the upper bound and a new variant of a ball-construction combined with thorough local estimates for the lower bound. The results indicate that in certain parameter regimes, the formation of dislocations is expected. Reference: Preprint arXiv no. 2403.13646, https://arxiv.org/abs/2403.13646
Further Informations
Oberseminar “Nichtlineare Partielle Differentialgleichungen” (Langenbach Seminar)
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- November 13, 2024 (Erwin-Schroedinger-Zentrum)
- Workshop/Konferenz: Foundations of Modern Nonparametric Statistics
more ... Location
Erwin-Schrödinger Zentrum Adlershof , Rudower Chaussee 26, 12489 Berlin.
Host
Humboldt-Universität zu Berlin
Universität Potsdam
WIAS Berlin
- Thursday, 07.11.2024, 15:00 (WIAS-405-406)
- Seminar Materialmodellierung
Dr. Tomáš Bodnár, Czech Technical University in Prague, Tschechische Republik:
On the use of viscoelastic fluids flows models in hemolysis prediction
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
The mathematical modeling and numerical simulations of blood flows is a very challenging problem due to complex rheological properties of blood. The blood can be considered as a suspension of red blood cells in blood plasma, resulting in a shear-thinning and viscoelastic behavior of the whole blood. It is well known that high levels of stress in blood flows, typically found in ventricular assist devices for example, can lead to blood damage - the hemolysis. Under high stress the red blood cells can be damaged or ruptured, which can lead to serious medical consequences. This is why a considerable effort has been dedicated by numerous researchers to prediction of the blood damage, based on the detailed knowledge of the flow field. There exists a number of models for hemolysis, but non of them is generally accepted as a definitive, convenient and reliable tool for prediction of hemolysis. The aim of the presented talk is to point out the importance of inclusion of non-Newtonian rheology of blood in the hemolysis predictions. The similarity between some of the promising stretch based tensorial models of hemolysis and the non-linear viscoelastic rheology models offers the possibility to estimate the hemolysis directly from the local stretch tensor. This possibility will be presented and discussed in detail.
Further Informations
Seminar Materialmodellierung
Host
WIAS Berlin
- Wednesday, 06.11.2024, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
Jonas Köppl, WIAS Berlin:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Host
WIAS Berlin
- Thursday, 31.10.2024, 14:00 (WIAS-405-406)
- Seminar Nichtlineare Optimierung und Inverse Probleme
Prof. Dr. Martin Gugat, Friedrich-Alexander-Universität Erlangen-Nürnberg:
Optimal control problems with probabilistic constraints
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Host
WIAS Berlin
- Wednesday, 30.10.2024, 15:15 (WIAS-405-406)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Prof. Dr. Tomáš Roubíček, Czech Academy of Sciences, Tschechische Republik:
Time discretization in visco-elastodynamics at large displacements and strains in the Eulerian frame
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
The fully-implicit time discretization (i.e. the backward Euler formula) is applied to compressible nonlinear dynamical models of viscoelastic media in the Eulerian description, i.e. in the actual deforming configuration. The Kelvin--Voigt rheology or also, in the deviatoric part, the Jeffreys (also called anti-Zener) rheology describing a (possibly nonlinear) creep or a rate-dependent plasticity are considered. Both a linearized convective model at large displacements with a convex stored energy and the fully nonlinear large strain variant with a (possibly generalized) polyconvex stored energy are considered. The time-discrete suitably regularized schemes (suggesting an implementable numerical strategy) are devised for both these heavily nonlinear cases. The numerical stability and, considering the multipolar 2nd-grade viscosity, also convergence towards weak solutions are proved, exploiting the convexity of the kinetic energy when written in terms of linear momentum instead of velocity. In the fully nonlinear case, the examples of neo-Hookean and Mooney--Rivlin materials are presented. A comparison with models of viscoelastic barotropic fluids is also made and thermodynamical extension is outlined, too.
Further Informations
Oberseminar “Nichtlineare Partielle Differentialgleichungen” (Langenbach Seminar)
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Wednesday, 30.10.2024, 10:00 (WIAS-HVP-3.13)
- Forschungsseminar Mathematische Statistik
Prof. Dr. Olga Klopp, ESSEC Business School, Frankreich:
Adaptive density estimation under low-rank constraints
more ... Location
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13
Abstract
In this talk, we address the challenge of bivariate probability density estimation under low-rank constraints for both discrete and continuous distributions. For discrete distributions, we model the target as a low-rank probability matrix. In the continuous case, we assume the density function is Lipschitz continuous over an unknown compact rectangular support and can be decomposed into a sum of K separable components, each represented as a product of two one-dimensional functions. We introduce an estimator that leverages these low-rank constraints, achieving significantly improved convergence rates. We also derive lower bounds for both discrete and continuous cases, demonstrating that our estimators achieve minimax optimal convergence rates within logarithmic factors.
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
- Thursday, 24.10.2024, 14:00 (WIAS-405-406)
- Seminar Numerische Mathematik
Prof. Dr. Winnifried Wollner, Universität Hamburg:
Gradient-robustness in the context of optimal control
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Host
WIAS Berlin
- Wednesday, 23.10.2024, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
Helia Shafigh, WIAS Berlin:
A spatial model for dormancy in random environment
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
In this talk, we introduce a spatial model for dormancy in random environment via a two-type branching random walk in continuous-time, where individuals can switch between dormant and active states through spontaneous switching independent of the random environment. However, the branching mechanism is governed by a random environment which dictates the branching rates. We consider three specific choices for random environments composed of particles: (1) a Bernoulli field of immobile particles, (2) one moving particle, and (3) a Poisson field of moving particles. In each case, the particles of the random environment can either be interpreted as catalysts, accelerating the branching mechanism, or as traps, aiming to kill the individuals. The different between active and dormant individuals is defined in such a way that dormant individuals are protected from being trapped, but do not participate in migration or branching. We quantify the influence of dormancy on the growth resp. survival of the population by identifying the large-time asymptotics of the expected population size. The starting point for our mathematical considerations and proofs is the parabolic Anderson model via the Feynman-Kac formula. Especially, the quantitative investigation of the role of dormancy is done by extending the Parabolic Anderson model to a two-type random walk.
Further Informations
A spatial model for dormancy in random environment
Host
WIAS Berlin
- Wednesday, 23.10.2024, 10:00 (WIAS-HVP-3.13)
- Forschungsseminar Mathematische Statistik
Prof. Dr. Weining Wang, University of Groningen, Niederlande:
Conditional nonparametric variable screening by neural factor regression
more ... Location
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13
Abstract
High-dimensional covariates often admit linear factor structure. To effectively screen correlated covariates in high-dimension, we propose a conditional variable screening test based on non-parametric regression using neural networks due to their representation power. We ask the question whether individual covariates have additional contributions given the latent factors or more generally a set of variables. Our test statistics are based on the estimated partial derivative of the regression function of the candidate variable for screening and a observable proxy for the latent factors. Hence, our test reveals how much predictors contribute additionally to the non-parametric regression after accounting for the latent factors. Our derivative estimator is the convolution of a deep neural network regression estimator and a smoothing kernel. We demonstrate that when the neural network size diverges with the sample size, unlike estimating the regression function itself, it is necessary to smooth the partial derivative of the neural network estimator to recover the desired convergence rate for the derivative. Moreover, our screening test achieves asymptotic normality under the null after finely centering our test statistics that makes the biases negligible, as well as consistency for local alternatives under mild conditions. We demonstrate the performance of our test in a simulation study and two real world applications.
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