Veranstaltungen

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Dienstag, 28.06.2022, 15:00 Uhr (WIAS-405-406)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Karsten Tabelow, WIAS Berlin:
In-vivo tissue properties from magnetic resonance data (hybrid talk)
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

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Dieser Vortrag findet bei Zoom statt: https://zoom.us/j/492088715

Veranstalter
WIAS Berlin
Mittwoch, 29.06.2022, 10:00 Uhr (WIAS-ESH)
Forschungsseminar Mathematische Statistik
Prof. Anuj Srivastava, Florida State University, USA:
Statistical shape analysis of complex natural structures (hybrid talk)
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
Shape analysis of structured data is a fast-growing field with broad applications. Advances in imaging techniques have led to a rich data source for analyzing shapes across many scientific disciplines. Examples include shapes of brain structures; morphological analysis of cancer cells, leaves, or botanical trees; shapes of geographical objects; human biometrics; shapes of the human genome; and so on. Shapes are relevant even in non-imaging data contexts, e.g., the shapes of COVID rate curves or the shapes of breathing pat- terns in sleep studies. What makes shape analysis both fascinating and challenging? The main difficulty stems from the fact that shape is generally an abstract notion that is hard to quantify. Imposing statistical models and inferences on shapes seem even more daunting. I will outline developments in a particular approach called elastic shape analysis. This approach defines shape as a quantity left after the effects of so-called nuisance transformations (often translations, rotations, and parameterizations) are removed. This removal requires representations and metrics that are invariant to these transformations. Elastic Riemannian metrics provide desired invariances but can be cumberso- me in practical implementations. A family of square-root type transformations has helped simplify these computations and make this approach feasible. These geometrical tools help us compute average shapes of 3D (botanical) trees, develop a shape alphabet for representing chromosomes as letter sequences, perform principal component analysis of arterial brain networks, and model dynamics of Entamoeba Histolytica in different liquid media. Furthermore, they help us address some fundamental scientific questions: Are the shapes of mitochondria in muscle tissues affected by the lifestyle (active versus sedentary)? Can we predict the onset of cognitive disorders using subcortical structures in the human brain? How does aging affect morphologies of arterial networks in human brains? I will present some of these applications of elastic shape analysis

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Der Vortrag findet bei Zoom statt: https://zoom.us/j/159082384

Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin
Universität Potsdam
29. Juni – 1. Juli 2022 (Harnack-Haus)
Workshop/Konferenz: Random Point Processes in Statistical Physics
mehr ... Veranstaltungsort
Harnack-Haus -- Tagungsstätte der Max-Planck-Gesellschaft

Veranstalter
WIAS Berlin
DFG Schwerpunktprogramm 2265
Mittwoch, 29.06.2022, 15:15 Uhr (WIAS-ESH)
Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Stefanie Schindler, WIAS Berlin:
Entropy method for a coupled reaction-diffusion system on the real line (hybrid talk)
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
In this talk, we investigate the long-time behavior of solutions to a nonlinear coupled reaction-diffusion system with detailed balance on the real line. By assuming that the solutions are in equilibria at infinity, we study the convergence towards a self-similar profile, which is a generalized steady-state in parabolic scaling variables. With this convergence, we answer how the solutions to the system mix the two stable asymptotic boundary values when time increases. Our strategy is to use an entropy approach with the relative Boltzmann entropy functional. This is a standard method for reaction-diffusion systems of mass-action type on bounded domains and a meaningful alternative to the linearization around an equilibrium. While this approach is well-studied on bounded domains, things become more complicated on the whole real line. This research is joint work with Alexander Mielke.

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Hybridveranstaltung - Teilnahme vor Ort bitte bei Dr. A. Glitzky (annegret.glitzky@wias-berlin.de) anmelden.
Hybrid event - please give Dr. A. Glitzky (annegret.glitzky@wias-berlin.de) notice of your on-site participation.

Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin
Mittwoch, 06.07.2022, 10:00 Uhr (WIAS-ESH)
Forschungsseminar Mathematische Statistik
Prof. Vincent Rivoirard, Université Paris Dauphine, Frankreich:
Nonparametric Bayesian estimation of nonlinear Hawkes process
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
Multivariate point processes are widely applied to model event-type data such as natural disasters, online message exchanges, financial transactions or neuronal spike trains. One very popular point process model in which the probability of occurrences of new events depend on the past of the process is the Hawkes process. In this work we consider the nonlinear Hawkes process, which notably models excitation and inhibition phenomena between dimensions of the process. In a nonparametric Bayesian estimation framework, we obtain concentration rates of the posterior distribution on the parameters, under mild assumptions on the prior distribution and the model. These results also lead to convergence rates of Bayesian estimators. Another object of interest in event-data modelling is to recover the graph of interaction of the phenomenon. We provide consistency guarantees on Bayesian methods for estimating this quantity; in particular, we prove that the posterior distribution is consistent on the graph adjacency matrix of the process, as well as a Bayesian estimator based on an adequate loss function. Joint work with Judith Rousseau and Deborah Sulem.

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Der Vortrag findet bei Zoom statt: https://zoom.us/j/159082384

Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin
13. – 15. Juli 2022 (WIAS-ESH)
Workshop/Konferenz: Nonlinear Waves and Turbulence in Photonics
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
The workshop "Nonlinear Waves and Turbulence in Photonics" (NWTP22) will bring together leading experts in the field of nonlinear optics and photonics. The workshop's guiding idea is to provide an international platform which leads to a more comprehensive understanding of fundamental nonlinear phenomena, such as wave-turbulence, solitons, and extreme waves. We expect exciting reports and fruitful discussions both on the most recent advances in the field and promising future developments.

Veranstalter
WIAS Berlin
Mittwoch, 13.07.2022, 10:00 Uhr (WIAS-405-406)
Seminar Interacting Random Systems
Quirin Vogel, NYU Shanghai, China, Volksrepublik:
tba
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Weitere Informationen
Seminar Interacting Random Systems

Veranstalter
WIAS Berlin