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Mon, 02. Nov at 15:00
Rudower Chaussee ...
An Energy Scaling Law for N -Gradient multi-well functionals
Tue, 03. Nov at 11:15
1.023 (BMS Room, ...
Refining Witten-Kontsevich
Abstract. The moduli space of metric Möbius graphs, which are non-orientable ribbon graphs, has one component homeomorphic to the moduli space of Riemann surfaces and another component homeomorphic to the moduli space of Klein surfaces. I'll discuss a lattice point count on this moduli space, weighted by a polynomial in b known as the measure of non-orientability. This "refined" lattice point count satisfies a refined version of Norbury's recursion for the count of lattice points on the moduli space of curves. Consequently, we obtain a recursion for the volumes of these moduli spaces that reduces to the Witten-Kontsevich recursion when b=0.
Tue, 03. Nov at 13:15
Room 3.007, Rudow...
Wed, 04. Nov at 10:00
HVP 11 a, R.313
Recent advances in drift estimation for high-dimensional diffusion models
Abstract. In this talk, we will present a selection of recent theoretical results on high-dimensional inference for the drift component of diffusion models. Such models have found numerous applications in areas including mathematical finance and biology among others. The primary focus will be on drift estimation for high-dimensional Ornstein-Uhlenbeck processes, although we will also discuss extensions to more general linear and nonlinear diffusion models. In particular, we will present Lasso-type estimators for sparse drift matrices, establish their statistical guarantees, and discuss consistent support recovery property. In the second part of the talk, we will consider drift estimation under low-rank constraints, a framework closely related to the concept of cointegration in continuous time. The presentation is based on joint work with Gabriela Ciołek, Dmytro Marushkevych, and Francisco Pina.
Wed, 04. Nov at 13:15
Room: 3.007 John ...
Wed, 04. Nov at 14:15
R. 405/406
The effects of pressure loads in the dimension reduction of elasticity models
Abstract
Thu, 05. Nov at 14:00
SR 115, Arnimallee 3
Transformers and large language models
Thu, 05. Nov at 14:00
FU Berlin, Villa ...
Thu, 05. Nov at 15:15
Rudower Chaussee ...
Differentiable programming for hybrid Earth system modeling
Abstract. Despite the revolution in autonomous in-situ and satellite remote sensing, much of the ocean remains poorly sampled observationally in terms of its spatio-temporal evolution. Inverse methods seek to combine the incomplete knowledge reservoirs from sparse observations and numerical models that require the provision of uncertain inputs to produce optimal state and parameter estimates of the system considered. In its various renderings, methods of optimal estimation and control or data assimilation are being used to learn uncertain parameters (calibration problem) in models or to produce optimal initial states for prediction (extrapolation problem). State estimates serve as optimal reconstructions to improve system understanding (interpolation problem). Rigorously applied, these methods also enable characterization of uncertainty that arise from different sources (model, observations, forcings). Scientific machine learning methods rely on similar mathematical concepts that underpin optimal estimation and may be successful when the system is heavily sampled. In this presentation I explore some of the concepts in the context of ocean modeling, in particular the concept of differentiable programming. I provide a subjective perspective on opportunities and challenges with a view toward hybrid data assimilation and machine learning to enable online or full-model learning. These ideas are being implemented in the context of general-purpose automatic differentiation applied to a new ocean model written in the Julia programming language.
Thu, 05. Nov at 16:00
1.013
New times, new relations
Abstract. I will present the results (so far) of an ongoing Human-AI collaboration to explore new tautological relations in the moduli of curves. Joint work with S. Canning, B. Kong, D. Peterson, A. Pixton, and J. Schmitt.
Fri, 06. Nov at 14:15
@TU (IMoS 0005)
Mathematics After AI
Abstract
Tue, 10. Nov at 11:15
1.023 (BMS Room, ...
A novel open/closed duality on toric Calabi--Yau threefolds
Abstract. The study of A-model topological string theory on toric Calabi--Yau threefolds X occupies a distinguished position at the crossroads of physics and mathematics, as it provides a tractable framework for string theory in which quantum string amplitudes can be defined rigorously and computed exactly. In this talk, I will discuss the open-closed A-model on X in the presence of Aganagic--Vafa special Lagrangian A-branes, as well as the closed A-model on X in the presence of Ramond--Ramond fluxes induced by toric B-branes. I will establish an open-closed duality theorem that explicitly relates the amplitudes arising in these two setups, thereby demonstrating that the two A-model configurations provide dual descriptions of the same underlying physical and enumerative problem. If time permits, I will further comment on the conjectural interpretation of the duality in terms of the geometric engineering of surface and line defects in four-dimensional N=2 gauge theory.
Tue, 10. Nov at 13:15
Room 3.007, Rudow...
Tue, 10. Nov at 14:00
MA 366
Wed, 11. Nov at 10:00
ESH, Anton-Wilhel...
Stochastic optimization and regularization for inverse problems
Abstract. In this talk, I will investigate two perspectives on the interaction between regularization and stochastic optimization. In the first part, I will present stochastic gradient methods with decaying Tikhonov regularization and show that a suitably balanced vanishing regularization schedule can stabilize the optimization dynamics while preserving convergence to a solution of the original unregularized problem. In the second part, I will turn to data-driven variational regularization, formulated as a stochastic bilevel optimization problem. In this setting, each upper-level evaluation requires a computationally expensive and typically inexact lower-level solve. This naturally motivates the use of multilevel Monte Carlo methods, whose efficiency depends critically on the coupling between successive lower-level approximations.
Thu, 12. Nov at 15:15
Rudower Chaussee ...
Thu, 12. Nov at 17:15
HU Berlin, Instit...
Sun, 15. Nov
SR 115, Arnimallee 3
Pretraining, scaling, in-context learning
Tue, 17. Nov at 11:15
1.023 (BMS Room, ...
Tue, 17. Nov at 14:00
MA 366
Wed, 18. Nov at 10:00
ESH, Anton-Wilhel...
Robust Gaussian process regression: Posterior contraction
Abstract. Gaussian processes form a popular and flexible class of prior distributions with principled uncertainty quantification, but the Gaussian likelihood on which they rely makes them highly sensitive to outliers and contaminated observations. We study Gaussian process regression when among the n observations, m of these are possibly contaminated. A generic framework to obtain posterior contraction rates in this setting is considered, from a frequentist perspective as the sample size n and the number of corrupted observations m grow. We adopt a generalised Bayes approach in which the log-likelihood is replaced by a robustified version; we discuss various choices thereof, such as one recently proposed by Altamirano et al. (2024) that preserves conjugacy. We investigate the minimax rate of estimation under adversarial contamination in terms of the Sobolev smoothness β of the regression function and m. The question of building adaptive procedures to both β and m is investigated, and we show that a polynomial loss for adaptation must be paid in general. We instantiate our results for Matérn Gaussian process and deep ReLU network priors. Numerical experiments for existing and new robust algorithms are provided, illustrating the practical applicability of our results.
Wed, 18. Nov at 11:30
WIAS-406
Wed, 18. Nov at 11:30
WIAS-406
Wed, 18. Nov at 14:15
WIAS, Erhard-Schm...
Perturbed minimizing movements of time-dependent functionals on metric spaces
Abstract
Thu, 19. Nov at 14:00
SR 115, Arnimallee 3
Reasoning models and reinforcement learning
Thu, 19. Nov at 14:00
1.023 (BMS Room, ...
Near-critical dimers and sine-Gordon model
Abstract. We consider the dimer model with Temperleyan boundary conditions on the square lattice (or more generally isoradial superpositions). When the edge weights are critical it is well known since the work of Kenyon that in the scaling limit, the associated height function is conformally invariant and is described by the Gaussian free field (aka massless free boson). We consider here a massive perturbation of this model, where the edge weights deviate slightly from their critical values. I will discuss a recent result, obtained jointly with Scott Mason and Lucas Rey, in which we showed that the associated height function is described in the scaling limit by the sine-Gordon model at its free fermion point. In parallel, geometric interfaces naturally associated via Temperley's bijection were previously shown (in joint work with Levi Haunschmid-Sibitz) to converge to a massive variant of SLE (Schramm--Loewner evolution) introduced by Makarov and Smirnov. We will strive to present these ideas in a non-technical manner; in particular no probability background should be needed.
Tue, 24. Nov at 13:15
Room 3.007, Rudow...
Wed, 25. Nov at 10:00
ESH, Anton-Wilhel...
Symmetry-preserving geodesic regression on Lie Groups for longitudinal medical imaging
Abstract. Many medical imaging tasks require statistical modeling of continuous transformations, including longitudinal anatomical shape change and articulated skeletal motion. These transformations naturally live on Lie groups, where meaningful statistical analysis should respect group symmetries to remain invariant to arbitrary coordinate choices and reference frames. In this talk, I will present a geodesic regression framework on Lie groups for longitudinal imaging data. Common approaches rely on Riemannian metrics, but many Lie groups do not admit a metric fully compatible with the group structure. This mismatch breaks symmetry and leads to unstable regression estimates. We therefore introduce a non-metric, bi-invariant estimator that is equivariant under both left and right group actions. We evaluate the method on synthetic data and on an open-access clinical dataset of longitudinal knee joint configurations acquired for osteoarthritis research. The proposed approach yields stable trajectories and reproducible statistical conclusions, while state-of-the-art Riemannian methods exhibit sensitivity and instability. These results highlight the practical advantages of symmetry-preserving statistical modeling in longitudinal medical imaging studies.
Wed, 25. Nov at 11:30
WIAS-406
Wed, 25. Nov at 16:30
IMoS 3003
Fast Counting of Cyclic Polytope Triangulations
Thu, 26. Nov at 14:00
SR 115, Arnimallee 3
Information geometry and gradient methods
Thu, 26. Nov at 16:15
HU Berlin, Instit...
Thu, 26. Nov at 17:15
HU Berlin, Instit...
Fri, 27. Nov at 14:15
@TU (IMoS 0005)
Tue, 01. Dec at 11:15
1.023 (BMS Room, ...
Tue, 01. Dec at 14:00
MA 366
Wed, 02. Dec at 10:00
ESH, Anton-Wilhel...
Wed, 02. Dec at 10:00
Weierstrass-Insti...
Fri, 04. Dec at 14:30
Hamburg
Abstract
Fri, 04. Dec at 16:00
Hamburg
Abstract
Tue, 08. Dec at 11:15
1.023 (BMS Room, ...
Tue, 08. Dec at 14:00
MA 366
Wed, 09. Dec at 10:00
ESH, Anton-Wilhel...
Wed, 09. Dec at 14:15
WIAS, Erhard-Schm...
Connecting models with data: inverse problems, their well-posedness and computational techniques
Abstract
Thu, 10. Dec at 16:15
HU Berlin, Instit...
Thu, 10. Dec at 17:15
HU Berlin, Instit...
Fri, 11. Dec at 14:15
@TU (IMoS 0005)
Tue, 15. Dec at 11:15
1.023 (BMS Room, ...
Wed, 16. Dec at 10:00
ESH, Anton-Wilhel...
Geometric deep operator learning for inverse problems with functional data
Fri, 25. Dec
Christmas Day
Sat, 26. Dec
St. Stephen's Day
Fri, 01. Jan
New Year's Day
Wed, 06. Jan at 10:00
ESH, Anton-Wilhel...
Fri, 08. Jan at 14:15
@TU (IMoS 0005)
Tue, 12. Jan at 11:15
1.023 (BMS Room, ...
Wed, 13. Jan at 10:00
Weierstrass-Insti...
Wed, 13. Jan at 14:15
WIAS, Erhard-Schm...
Thu, 14. Jan at 14:00
SR 115, Arnimallee 3
Tue, 19. Jan at 11:15
1.023 (BMS Room, ...
Wed, 20. Jan at 10:00
Weierstrass-Insti...
Wed, 20. Jan at 11:30
WIAS-406
Wed, 20. Jan at 16:30
IMoS 3003
Orthogonal projections, linearization and sausages: a geometric approach to Cheeger sets
Fri, 22. Jan at 14:15
@TU (IMoS 0005)
Tue, 26. Jan at 11:15
1.023 (BMS Room, ...
Thu, 28. Jan at 17:15
HU Berlin, Instit...
Wed, 03. Feb at 11:30
WIAS-406
Wed, 10. Feb at 10:00
ESH, Anton-Wilhel...
Wed, 17. Feb at 10:00
Weierstrass-Insti...
Mon, 08. Mar
International Women's Day (Regional Holiday)
Fri, 26. Mar
Good Friday