Veranstaltungen
- Mittwoch, 29.07.2026, 14:15 Uhr (WIAS-ESH)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Ass. Prof. Quoc Bao Tang, Universität Graz, Österreich:
Global existence and large time behaviour of nonlinear reaction-diffusion systems
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Weierstraß-Institut, Anton-Wilhelm-Amo-Str. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Weitere Informationen
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin
- Dienstag, 04.08.2026, 10:15 Uhr (WIAS-406)
- Seminar Nichtlineare Optimierung und Inverse Probleme
Dr. Hendrik Kleikamp, Universität Graz, Österreich:
From reduced bases to U-Nets: Machine Learning for parametric optimal control
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Weierstraß-Institut, Anton-Wilhelm-Amo-Str. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)
Abstrakt
In this talk, we consider optimal control problems whose dynamics and objective functional depend on parameters. Solving such problems for many parameter values is often computationally prohibitive. To address this challenge, we consider reduced-order models (ROMs) that accelerate computations while retaining rigorous accuracy guarantees, including a posteriori error estimates.The projection-based reduced basis ROMs considered here can be further accelerated through the incorporation of machine learning techniques. By combining classical model reduction with machine learning, the a posteriori error estimator can be transferred directly to the machine learning predictions. Moreover, the full-order model, reduced basis ROM, and machine learning surrogate can be organized into an adaptive model hierarchy, in which the different models are trained and employed in an adaptive manner.
In the final part of the talk, we present recent work on the use of U-Nets for nonlinear surrogate modeling in problems characterized by slowly decaying Kolmogorov widths, where linear reduced models are known to struggle. To assess their performance, we compare U-Nets with alternative approaches, including autoencoder architectures and parametric decoders, on challenging optimal control problems.
Veranstalter
WIAS Berlin - Dienstag, 04.08.2026, 14:00 Uhr (WIAS-ESH)
- Forschungsseminar Mathematische Modelle der Photonik
Dr. Maria Chernysheva, Leibniz-IPHT:
Mamyshev oscillators: Towards self-starting generation
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Weierstraß-Institut, Anton-Wilhelm-Amo-Str. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstrakt
Mamyshev oscillators offer a particularly valuable platform for investigating the phenomenon of ultrashort pulse formation because they do not rely on conventional saturable absorbers. Instead, pulse formation is governed by self-phase modulation in normal-dispersion fibres combined with periodic offset spectral filtering. Achieving self-starting in these systems is challenging. In my talk, I will first present the self-starting, all-fibre, all-normal-dispersion Thulium-doped Mamyshev oscillator operating near 1.9 µm. The real-time measurements and numerical simulations reveal the build-up pathway from noise through transient multi-pulsing and pulse competition to a stationary noise-like envelope. Then I will discuss the new developemnts in hybrid laser systems employing SOA as a gain media within fibre cavities, built in a compact Fabry?Perot design or righ configuraiton. Both systems incorporate a highly nonlinear passive near-zero normal-dispersion fibre, developed at IPHT for this project. I will present current limitations towards achieving stable ultrashort pulse generation.
Veranstalter
WIAS Berlin
- 7. – 11. September 2026 (HUB main building)
- Workshop/Konferenz: 17th International Conference on Free Boundary Problems: Theory and Applications 2026
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Humboldt Universität zu Berlin, Unter den Linden 6, 10117 Berlin
Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin
- 3. – 6. November 2026 (WIAS-ESH)
- Workshop/Konferenz: Stochastic processes with reinforcement
mehr ... Veranstaltungsort
Weierstraß-Institut, Anton-Wilhelm-Amo-Str. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Veranstalter
WIAS Berlin