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Tue, 03. Feb at 11:15
1.023 (BMS Room, ...
The off-shell one and two-loop box recovered from intersection theory
Abstract. We advertise intersection theory for generalised hypergeometric functions as a means of evaluating Mellin-Barnes representations. As an example, we study two-parameter representations of the off-shell one- and two-loop box graphs in exactly four-dimensional configuration space. Closing the integration contours for the MB parameters we transform these into double sums. Polygamma functions in the MB representation of the double box and the occurrence of higher poles are taken into account by parametric differentiation. Summing over any one of the counters results into a <sub>p+1</sub>F<sub>p</sub> that we replace by its Euler integral representation. The process can be repeated a second time and results in a two- or four-parameter Euler integral, respectively. We use intersection theory to derive Pfaffian systems of equations on related sets of master integrals and solve for the box and double box integrals reproducing the known expressions. Finally, we use a trick to re-derive the double box from a two-parameter Euler integral. This second computation requires only very little computing resources.
Tue, 03. Feb at 11:15
1.023 (BMS Room, ...
Panorama of matrix models and topological recursion IV
Abstract. This is crash course which aims at explaning various aspects of: random matrix ensembles and Coulomb gases, loop equations, spectral curves, topological recursion, maps, free probability, how they fit together and pose some open problems.
Tue, 03. Feb at 16:00
zibredsalon
Clustering with mixture models to identify model deficiencies
Abstract. When representing a complex system through a computational model, a mismatch between the results of the simulations and the measurements from the real world is usually unavoidable. If such discrepancy renders the model unreliable and thus unuseful, improving it becomes a necessity. The work considered for this talk proposes a mixture model-based, non-intrusive strategy which clusters sensor readings using multiple sets of parameters, aiming to give the modeler insight about model biases behind structured discrepancies in order to improve the model.
Wed, 04. Feb at 10:00
HVP 11 a, R.313
Advancing Decision-Efficiency in (Pre)-clinical Research via Novel Sequential Frameworks
Abstract. The escalating costs and ethical imperatives of drug development necessitate statistical frameworks that prioritize both efficiency and rigorous evidence generation. Conventional fixed-sample designs often lack the flexibility to adapt to emerging data, leading to potentially redundant animal testing or delayed decision-making. This talk introduces a suite of novel sequential testing procedures designed to optimize the transition from pre-clinical discovery to clinical validation. We explore three primary pillars of application: (1) Pre-clinical Statistics: We demonstrate how sequential probability ratio tests (SPRT) and group sequential designs can be adapted for small-sample laboratory studies, ensuring ethical stop-for-efficacy or stop-for-futility boundaries are met without compromising the Type I error rate. (2) Generalized Pairwise Comparisons (GPC): We extend the sequential framework to GPC, a versatile method for analyzing multiple prioritized endpoints. This allows researchers to assess the net clinical benefit of a treatment sequentially, integrating diverse outcomes (e.g., survival, toxicity, and biomarkers) into a single, unified decision metric. (3) Digital Biomarkers: Addressing the high-frequency, longitudinal nature of data from wearable devices, we propose sequential monitoring techniques that detect treatment signals in real-time. These methods account for the inherent noise and autocorrelation in digital health data, facilitating faster go/no-go decisions in early-phase trials. By bridging these methodologies, this talk provides a roadmap for implementing adaptive evidence synthesis that reduces sample size requirements and accelerates the identification of promising therapeutic candidates.
Thu, 05. Feb at 10:00
SR 009, Arnimallee 6
Thu, 05. Feb at 10:00
SR 009, Arnimallee 6
Thu, 05. Feb at 10:00
SR 009, Arnimallee 6
Finite volume methods for regularized Dean-Kawasaki equations
Thu, 05. Feb at 15:15
Rudower Chaussee ...
Economic MPC with periodic stabilizing terminal constraints for a generalized Nash equilibrium problem
Tue, 10. Feb at 11:15
1.023 (BMS Room, ...
On the conifold gap for the local projective plane
Abstract. The conifold gap conjecture asserts that the polar part of the Gromov-Witten potential of a Calabi-Yau threefold near its conifold locus has a universal expression described by the logarithm of the Barnes G-function. In this talk I will describe a proof of the conifold gap conjecture for the local projective plane, whereby the higher genus conifold Gromov-Witten generating series of local P<sup>2</sup> are related to the thermodynamics of a certain statistical mechanical ensemble of repulsive particles on the positive half-line. As a corollary, this establishes the all-genus mirror principle for local P<sup>2</sup> through the direct integration of the BCOV holomorphic anomaly equations.
Wed, 11. Feb at 10:00
Weierstrass-Insti...
Linear Monge is All You Need
Abstract. In this talk, we explore the geometry of the Bures-Wasserstein space for potentially degenerate Gaussian measures on a separable Hilbert space, based on our recent work with Yoav Zemel. A key feature of our approach is its simplicity: relying only on elementary arguments from linear operator theory, we are able to derive explicit results without resorting to Kantorovich duality or Otto's Calculus. We provide a complete characterisation of both the Monge and Kantorovich problems in this context, regardless of the degeneracy of their measures. Furthermore, we show a simple way to construct all possible Wasserstein geodesics connecting two Gaussian measures. Finally, we generalise our results to characterise Wasserstein barycenters of Gaussian measures, borrowing the idea of Procrustes distance from statistical shape analysis.
Wed, 11. Feb at 10:00
Weierstrass-Insti...
Kernel ridge regression for spherical responses
Abstract. The aim is to propose a novel nonlinear regression framework for responses taking values on a hypersphere. Rather than performing tangent space regression, where all the sphere responses are lifted to a single tangent space on which the regression is performed, we estimate conditional Fréchet means by minimizing squared distances on the nonlinear manifold. Yet, the tangent space serves as a linear predictor space where the regression function takes values. The framework integrates Riemannian geometry techniques with functional data analysis by modelling the regression function using methods from vector-valued reproducing kernel Hilbert space theory. This formulation enables the reduction of the infinite-dimensional estimation problem to a finite-dimensional one via a representer theorem and leads to an estimation algorithm by means of Riemannian gradient descent. Explicit checkable conditions on the data that ensure the existence and uniqueness of the minimizing estimator are given.
Wed, 11. Feb at 11:30
Weierstrass Lectu...
Quantitative mixing properties for Gibbs fields on bounded degree graphs
Abstract. Mixing properties are an important object of study within the theory of Gibbs measures. In this talk I will focus on two quantitative mixing properties: exponential $\phi$-mixing (also called weak mixing) and exponential $\psi$-mixing (also called ratio weak mixing). These mixing conditions are well studied for Gibbs fields on square lattices. For instance, the unique Gibbs state of the Ising model above the critical temperature exhibits both types of mixing. In this talk we shall consider random fields on arbitrary graphs with bounded degree. While exponential $\phi$-mixing is known to hold whenever Dobrushin's uniqueness condition is satisfied, exponential $\psi$-mixing has been studied very little in this general setting. The main result I'm going to present shows that for Markovian random fields $\phi$-mixing with sufficiently high exponential decay rate implies $\psi$-mixing with slower, but still exponential decay rate. This generalizes a result of Alexander for square lattices and allows to formulate a general criterion for exponential $\psi$-mixing of Gibbs measures in terms of the corresponding Dobrushin constant. I will illustrate how this criterion applies to Ising and Potts models on regular trees.
Wed, 11. Feb at 14:15
WIAS, Erhard-Schm...
A Navier--Stokes/Mullins--Sekerka system with different densities: weak solutions
Abstract
Wed, 11. Feb at 16:00
Wed, 11. Feb at 16:00
Thu, 12. Feb at 10:00
SR 009, Arnimallee 6
Thu, 12. Feb at 12:00
Thu, 12. Feb at 14:00
Counting cells of the Dressian
Abstract. A valuation of a matroid M is a map v that assigns a real value v(B) to each basis B of M, such that a quantitative version of the symmetric base exchange axiom holds: v is a valuation of M if and only if (V) for all bases B, B’ of M an all e in B\B’, there is an f in B'\B so that v(B) + v(B’) >= v(B-e+f) + v(B'+e-f). The Dressian is the collection of all valuations of M: Dr(M):= { v : v a valuation of M }. Dr(M) is a polyhedral complex in R^{bases of M}. In previous joint work with Guus Bollen and Jan Draisma, we found that each algebraic representation of M over a finite field gives rise to a valuation of M. In some cases this fact could be used to rule out that M has an algebraic representation. Such arguments would always involve an enumeration of the cells of Dr(M). This promted the question how the cells of Dr(M) are best enumerated and more broadly, what properties of M limit their number and variation. In this talk, I describe a method for bounding the number of cells of the Dressian, inspired by entropy counting and the contained method.
Thu, 12. Feb at 16:15
HU Berlin, Instit...
Thu, 12. Feb at 17:15
HU Berlin, Instit...
Sat, 14. Feb at 16:30
EN 058
Wed, 18. Feb at 11:30
Weierstrass Lectu...
Wed, 25. Feb at 11:30
Weierstrass Lectu...
Wed, 04. Mar at 16:30
EN 058
Wed, 15. Apr at 14:15
WIAS, Erhard-Schm...
Thu, 16. Apr at 14:15
WIAS, Erhard-Schm...
Tue, 21. Apr at 11:15
1.023 (BMS Room, ...
Tue, 21. Apr at 14:30
TU Berlin, MA Bui...
Tue, 28. Apr at 14:30
TU Berlin, MA Bui...
Tue, 05. May at 11:15
1.023 (BMS Room, ...
Wed, 20. May at 14:15
WIAS, Erhard-Schm...
Tue, 14. Jul at 11:15
1.023 (BMS Room, ...
Thu, 17. Dec at 16:30
EN 058
Drawing algebraic curves in OSCAR
Abstract. I will talk about how to visualize real plane algebraic curves given as the zero set of a polynomial in two variables using Oscar.jl. I will highlight performance and exactness issues using real world examples.