Piotr
Sulkowski
University of Warsaw
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13. January
Tue W02
Konstantin
Viol
HU Berlin
LSFEM for indefinite second-order elliptic PDE
14. January
Wed W02
Ulrike
Schneider
Universität Wien
Frank
Konietschke
Charité
Marcel
Ortgiese
University of Bath
Dynamic accessibility percolation
Abstract.
Accessibility percolation is a simple model in evolutionary biology describing how a population driven by the evolutionary forces of selection and mutation explores a fitness landscape. Mathematically, the fitness landscape is modeled by attaching random weights to the vertices of a graph. Then, accessible percolation asks whether there are paths of increasing fitness of a certain length. I will review some of the progress in this area and then consider the question what happens if the fitness landscape changes over time. In particular, I will focus on the case when the underlying graph is a regular tree. Depending on the ratio of depth to width of the tree, we will see different scaling regimes for the time it takes to see an increasing path. Some of the proofs rely on adapting techniques from the area of noise sensitivity for Boolean functions.
Matthew
Konefal
Loughborough, UK
Definability in Theories Based on Free Group and Free Monoid Equations
Abstract.
Equations in the free group and free monoid have long been studied together. I’ll outline their history and properties, comparing facets of their two theories. Each can be studied by adapting techniques developed for the other. After demonstrating this, we’ll focus on definability in theories whose atoms are free group equations. Tools for establishing nondefinability in this setting are due to group theorists and model theorists, yet have the appearance of word-combinatorial lemmas. The tools - combined - yield characterisations of definability, the free monoid analogues of which seem more elusive. I'll end discussing length abstractions and length constraints, which link equations to weak arithmetics. Naturally, more definability questions result, including major open problems.
André
Erhardt
WIAS
Marcel
Ortgiese
U Bath
Jean-Dominique
Deuschel
TU Berlin
Mikhail
Gorsky
Jean Monnet University
15. January
Thu W02
Alheydis
Geiger
Realizing self-projecting Matroids
Abstract.
Self-dual point configurations have been studied throughout the centuries. In this talk the generalization to self-projecting point configurations will be introduced. These give rise to self-projecting matroids, in other words, to matroids that satisfy the disjoint bases property and that have no almost generic element. The parameter space of self-projecting point configurations is the self-projecting Grassmannian. This is also the space of self-projecting realizations of self-projecting matroids. Its structure is interesting from multiple perspectives, like mathematical physics. We compute the realization spaces for small matroids up to rank 4 on 9 elements. There will be a short overview of the available code and database. If time permits, I will finish with an outlook on the perspective of tropical geometry and subdivisions of matroid polytopes. This project is joint work with Francesca Zaffalon.
Francesca
Primavera
University of California
16. January
Fri W02
Daan
Janssen
University of York
Boundaries, corners and edge modes: semi-local observables for electromagnetism
Abstract.
For gauge field theories on spacetimes with (asymptotic) boundaries, the gauge transformations acting non-trivially at boundaries and/or corners have a distinguished role compared to those acting purely in the bulk, where the latter are viewed as redundancies, the former play an important role in boundary/infrared features of these theories. We investigate the quantum electromagnetic field on spacetimes with boundaries and corners, and construct algebras of semi-local observables sensitive to the boundary gauge group. We discuss the role of these observables in gluing procedures and superselection theory for electromagnetism, as well as the existence of physically well behaved (Hadamard) states on these algebras.
20. January
Tue W03
Burkhard
Eden
HU Berlin
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.
Falk
Hante
HU Berlin
Stabilizing PDE Control: Optimization and Feedback in Moving Horizons
21. January
Wed W03
Ulrike
Schneider
Universität Wien
Yannic
Steenbeck
TU Braunschweig
Olaf
Klein
WIAS
Uncertainty quantification for a model for a magnetostrictive material involving a hysteresis operator
Jan Moritz
Petschick
Uni Bielefeld
22. January
Thu W03
Karan
Mukhi
Raphael
Kuess
HU Berlin
23. January
Fri W03
Malte
Leimbach
MPI Bonn
Janina
Bernardy
MPI Bonn
27. January
Tue W04
Maciej
Dolega
Institute of Mathematics, Polish Academy of Sciences
Nathan
Arnaud
HU Berlin
28. January
Wed W04
Jakob
Runge
Uni Potsdam
Anastasija
Pešić
WIAS
Curvature-driven pattern formation in biomembranes: A gradient flow approach
RĂĽdiger
Frey
WU Vienna
Andrew
Allen
U Durham
Christopher
Voll
Bielefeld University
Hall-Littlewood polynomials, affine Schubert series, and lattice enumeration
Abstract.
In this talk, I would like you to meet Hall-Littlewood-Schubert series, a new class of multivariate generating functions. Their definition features semistandard Young tableaux and polynomials resembling the classical Hall-Littlewood polynomials. Their intrinsic beauty notwithstanding, Hall-Littlewood-Schubert series have many applications to counting problems in algebra, geometry, and number theory. In my talk the spotlight will be on applications to affine Schubert series. These may be seen as an integral analogue of the Poincare polynomials enumerating the rational points over finite fields of classical Schubert varieties. The latter parametrize subspaces of a given vector space by the intersection dimensions with a fixed flag of reference. This work is joint with Joshua Maglione. I will explain things from scratch, assuming no familiarity with the advanced technical vocabulary used in this abstract.
29. January
Thu W04
Ben
Smith
Xiaofei
Sei
University of Toronto
Claudio
Dappiaggi
University of Pavia
Equivalence between local and global Hadamard States with Robin boundary conditions on half-Minkowski spacetime
Abstract.
We construct the fundamental solutions and Hadamard states for a Klein-Gordon field in half-Minkowski spacetime with Robin boundary conditions in arbitrary dimensions using a generalisation of the Robin-to-Dirichlet map. On the one hand this allows us to prove the uniqueness and support properties of the Green operators. On the other hand, we obtain a local representation for the Hadamard parametrix that provides the correct local definition of Hadamard states, capturing 'reflected' singularities from the spacetime timelike boundary. This allows us to prove the equivalence of our local Hadamard condition and the global Hadamard condition with a wave-front set described in terms of generalized broken bicharacteristics, obtaining a Radzikowski-like theorem in half-Minkowski spacetime.<br><br>Joint work with B. Costeri, R. D. Singh and B. Juárez-Aubry -- ArXiv: 2509.26035 [math-ph]
Alessandro
Bondi
École Polytechnique Paris
30. January
Fri W04
Beatrice
Costeri
University of Pavia
03. February
Tue W05
Gaëtan
Borot
HU Berlin
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.
04. February
Wed W05
Frank
Konietschke
Charité
10. February
Tue W06
Andrea
Brini
Sheffield University
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.
11. February
Wed W06
Ho
Yun
EPFL
Linear Monge is All You Need
Abstract.
We explore the geometry of the Bures–Wasserstein space for potentially degenerate Gaussian measures on a separable Hilbert space. Using elementary linear operator arguments, we derive explicit results without Kantorovich duality or Otto calculus. We fully characterize the Monge and Kantorovich problems irrespective of degeneracy, construct all Wasserstein geodesics between two Gaussian measures, and generalize to Wasserstein barycenters of Gaussian measures, borrowing the Procrustes distance from statistical shape analysis. (Joint work with Yoav Zemel.)
BĂ©atrice
Matteo
University of Geneva
Kernel ridge regression for spherical responses
Abstract.
We propose a nonlinear regression framework for responses on a hypersphere, estimating conditional Fréchet means by minimizing squared manifold distances while employing a linear predictor space in the tangent space. Integrating Riemannian geometry with functional data analysis via vector-valued RKHS methods yields a representer theorem and an algorithm based on Riemannian gradient descent. We give explicit, checkable conditions ensuring existence and uniqueness of the estimator.
Elias
Zimmermann
Universität Leipzig
Andrea
Poiatti
Universität Wien
Tony
Lelievre
CERMICS
Vitalii
Konarovskyi
U Hamburg
12. February
Thu W06
Rudi
Pendavingh
Guido
Gazzani
University of Verona
Beatrice
Ongarato
Technische Universität Dresden
14. February
Sat W06
Mikhail
Gorsky
Jean Monnet University
15. April
Wed W15
Pierluigi
Colli
UniversitĂ Pavia, Italy
16. April
Thu W15
José Antonio
Carrillo
University of Oxford, United Kingdom
21. April
Tue W16
Pierrick
Bousseau
Oxford University
05. May
Tue W18
Damien
Simon
Sorbonne Universite
20. May
Wed W20
Riccarda
Rossi
University of Brescia, Italy
14. July
Tue W28
Alexander
Alexandrov
IBS Pohang
17. December
Thu W50
Lars
Kastner
TU Berlin
Drawing algebraic curves in OSCAR