var sms = '<div id="sms_bulletin">  <div id="sms_header">  <div class="do_not_print" id="arrow_left"><a href="?next=-1"><img src="//www2.math.ethz.ch/smsjs/images/arrow_left.png"/></a></div><div class="do_not_print" id="arrow_right"><a href="?next=1"><img src="//www2.math.ethz.ch/smsjs/images/arrow_right.png"/></a></div>    <div class="sms_title">      <span style="float: left;">SMS</span>      <span>SWISS MATHEMATICAL SOCIETY</span>      <span style="float: right;">SMG</span>    </div>    <div class="sms_info">      <span style="float: left; width: 250px;">Bulletin no. 9</span>      <span style="float: right; text-align:right; width: 250px;">14.4 - 18.4.2025</span>      <span style="text-align: center; display: block; width: 250px; margin: auto; position: relative;">Spring Semester 2025</span>    </div>  </div>  <div></div>  <div id="sms_content">    <div class="day">      <div class="day_title">        Monday, April 14      </div>      <div class="day_content">        <div class="day_content_item normal"><div class="event_location uni_ba"><a class="external" href="https://unibas.ch">Universität Basel</a></div><div class="event_type"><a class="external" href="https://dmi.unibas.ch/de/studium/mathematik/doktorat/bernoullis-tafelrunde">Bernoullis Tafelrunde</a></div><br /><div class="event_speaker"> Federico Accossato (Turin)</div><div class="event_title"><a class="external" href="https://dmi.unibas.ch/de/studium/mathematik/doktorat/bernoullis-tafelrunde/detail/bernoullis-tafelrunde-federico-accossato-turin/">Chasing Transcendental Numbers through Continued Fractions</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The existence of transcendental numbers was probably first conjectured by Euler in the 18th century, but it was Liouville who, in 1844, provided the first explicit example of such numbers. Since then, brilliant mathematicians have developed numerous methods either to establish the transcendence of famous mathematical constants, most notably $\\pi$ and $e$, or to construct new transcendental numbers from scratch. In particular, continued fractions have emerged as a powerful tool for this latter purpose. In this talk, after recalling some fascinating properties of continued fractions and their deep connections to Diophantine Approximation, we will highlight how they have been used to construct explicit examples of transcendental numbers. Time permitting, we will also touch upon recent advances in the generalization of these techniques to multidimensional continued fractions. Such results are a joint work with Nadir Murru and Giuliano Romeo. abstract</div><div class="event_time">12:15 &bull; Universität Basel, Seminarraum 05.002, Spiegelgasse 5</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/talks-in-mathematical-physics">Talks in Mathematical Physics</a></div><br /><div class="event_speaker"> Marvin Dippel (University of Salerno)</div><div class="event_title">DeformationTheory for generalized Coisotropic Reduction <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Reduction of Poisson manifolds by coisotropic submanifolds formalizes symmetry reduction of classical mechanical systems, and therefore plays an important role in Poisson geometry. Constraint algebras encode the additional structure on the algebra of functions needed for reduction and their deformations yield (formal) star products compatible with reduction. I will discuss the deformation theory of these constraint algebras and present some results about an adapted Hochschild-Kostant-Rosenberg Theorem computing the cohomology controlling this deformation theory.</div><div class="event_time">13:30 &bull; ETH Zentrum, Winterthurerstrasse 190, Z&uuml;rich, Building Y27, Room H 25</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/symplectic-geometry-seminar">Symplectic Geometry Seminar</a></div><br /><div class="event_speaker"> Marcelo Alves (University of Antwerp)</div><div class="event_title">From curve shortening to Birkhoff sections of geodesic flows <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In this talk, based on joint work with Marco Mazzucchelli, I will present some new results on the dynamics of geodesic flows of closed Riemannian surfaces, proved using the curve shortening flow. The first result is a forced existence theorem for orientable closed Riemannian surfaces of positive genus, asserting that the existence of a contractible simple closed geodesic &gamma; forces the existence of infinitely many closed geodesics in every primitive free homotopy class of loops and intersecting &gamma;. I will then explain how this type of result can be used to show the existence of Birkhoff sections for the geodesic flow of any closed orientable Riemannian surface.</div><div class="event_time">15:15 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/mpseminar/seminar.html">Séminaire de Mathématique Physique </a></div><br /><div class="event_speaker"> Sébastien  Ott  (EPFL)</div><div class="event_title">Finite volume mixing properties of lattice spin models <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Mixing properties of lattice spin models are ways to formalize the notion of information propagation/spatial dependency in these random fields.I will present a family of notions making precise mixing properties of finite volume lattice spin models, in particular describing how boundary conditions do (or do not) affect information propagation inside a system. I will spend most of the time presenting an overview of what is known and applications. Then, I will present recent work on some of the issues in dimension 2, and, if time permits, briefly discuss less standard motivations for extensions of these questions to larger classes of models than the one considered up to now.</div><div class="event_time">16:15 &bull; Université de Genève, Conseil Général 7-9, Room 1-15</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_be"><a class="external" href="https://www.unibe.ch">Universität Bern</a></div><div class="event_type"><a class="external" href="https://www.math.unibe.ch/research/talks/colloquium/index_eng.html">Mathematisches Kolloquium </a></div><br /><div class="event_speaker">Prof. Dr. Yann Brenier (Université Paris-Saclay)</div><div class="event_title"><a class="external" href="https://www.math.unibe.ch/research/talks/colloquium/index_eng.html">From fluids to combinatorics and vice versa via Optimal Transport theory</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />A comprehensive mathematical description of fluids like water goes back to Leonard Euler in the middle of the 18th century. If we think at a discrete level, for instance in terms of pixels, the motion of water looks very much like a very fast succession of permutations exchanging pixels, a little like a "melting rubik cube". We will discuss this analogy in more details, in connection with the mathematical theory of optimal transportation and its numerous applications.</div><div class="event_time">17:15 &bull; Universität Bern, Sidlerstrasse 5, 3012 Bern, Room B6</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Tuesday, April 15      </div>      <div class="day_content">        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/annonces/groupes-geometrie">Groupes et Géométrie </a></div><br /><div class="event_speaker"> Mikhail  Hlushchanka  (University of Amsterdam)</div><div class="event_title">The independence polynomial on recursive graph sequences - the dynamical perspective <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The distribution of the zeros of partition functions on graphs are intimately related to the analyticity of physical quantities and their phase transitions. In their pioneering work in the 1950s, Lee and Yang proved that the free energy per site of the cubic lattice is analytic at a given positive real parameter, provided that the complex zeros of the partition functions for a sequence of finite graphs converging to the lattice avoid a neighborhood of this parameter. In the last decade, a special focus was put on graph sequences that do not converge to a regular lattice but are instead defined recursively. Examples of such recursive graph sequences include hierarchical lattices, Cayley trees, Sierpi&#324;ski gasket graphs, and various self-similar Schreier graphs. Significant progress has been made in studying the partition functions of the Ising, Potts, and Hard-Core models on these graphs (with the latter two corresponding to the chromatic and independence graph polynomials, respectively). One main advantage of working with recursive sequences of graphs is that the underlying recursion naturally induces an iterative system on the level of partition functions, often given in terms of rational maps in one or several (complex) variables. By analyzing the dynamical behavior of these iterative systems, we can gain insights into the properties of the respective graph polynomials, such as phase transitions and computational complexity.In our current work with Han Peters (University of Amsterdam), we attempt to establish a unified framework for recursive graph sequences in the Hard-Core model setting. We start with an arbitrary graph with k marked vertices. At each recursive step, we construct a new graph by taking n copies of the previous graph and connecting these copies along the marked vertices (according to a specified rule). The dynamical systems that emerge from the respective independence polynomials are represented by homogeneous polynomials of degree n in 2^k variables. Somewhat surprisingly, it turns out that these systems can be successfully analyzed in this general context. In the talk, I will report on our results on the structure of the zero sets of the independence polynomials for these recursive graph sequences, particularly highlighting the absence of phase transitions.</div><div class="event_time">10:30 &bull; Université de Genève, Conseil Général 7-9, Room 1-05</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ba"><a class="external" href="https://unibas.ch">Universität Basel</a></div><div class="event_type"><a class="external" href="https://dmi.unibas.ch/de/forschung/mathematik/algebraische-geometrie/">Seminar Algebra and Geometry</a></div><br /><div class="event_speaker"> Aline Zanardini (EPFL)</div><div class="event_title"><a class="external" href="https://dmi.unibas.ch/de/news-events/detail/seminar-algebra-and-geometry-aline-zanardini-epfl/">GIT for linear systems of hypersurfaces</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In this talk, we will consider the problem of classifying linear systems of hypersurfaces inside projective space and up to projective equivalence. I will report on a possible approach to solving this problem via geometric invariant theory, and I will further illustrate how such an approach can be applied to some relevant geometric examples. This is based on joint work with Masafumi Hattori.</div><div class="event_time">10:30 &bull; Universität Basel, Seminarraum 00.003, Spiegelgasse 1</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/annonces/seminaire-danalyse-numerique">Séminaire d\'Analyse Numérique </a></div><br /><div class="event_speaker"> Euan Spence (University of Bath)</div><div class="event_title">New theory for two-level domain-decomposition preconditioners for the high-frequency Helmholtz equation  <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />When solving self-adjoint positive-definite problems (such as Laplace’s equation) with domain-decomposition methods, coarse spaces provide global transfer of information, and are the key to parallel scalability. However, the design of practical coarse spaces for high-frequency wave problems, such as the high-frequency Helmholtz equation, is much more di&#64259;cult than in the self-adjoint positive-definite case. In the last year, there have been several papers providing theory for specific coarse-spaces consisting of (pre-computed) problem-adapted basis functions. This talk will present:1) a general theory that applies to all these previously-analysed coarse spaces, and2) new results about piecewise-polynomial coarse spaces.This is joint work with Jeffrey Galkowski (University College London) and Ivan Graham (University of Bath).</div><div class="event_time">14:00 &bull; Université de Genève, Conseil Général 7-9, Room 1-05</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://calendar.google.com/calendar/embed?mode=AGENDA&height=600&wkst=2&bgcolor=%23FFFFFF&src=t36it03v52cus2detrvinlgk18%40group.calendar.google.com&color=%235F6B02&ctz=Europe%2FZurich">Groups, Arithmetic and Algebraic Geometry Seminar </a></div><br /><div class="event_speaker"> Eva Bayer-Fluckiger</div><div class="event_title">Automorphisms of K3 surfaces and cyclotomic polynomials <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Let X be a complex projective K3 surface and let TX be its transcendental lattice. The characteristic polynomials of the isomorphisms of TX induced by automorphisms of X are powers of cyclotomic polynomials. Which powers of cyclotomic polynomials occur? The aim of this talk is to answer this question, as well as related ones.</div><div class="event_time">14:00 &bull; EPF Lausanne, Bernoulli Center</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/annonces/seminaire-danalyse-numerique">Séminaire d\'Analyse Numérique </a></div><br /><div class="event_speaker"> Rob Corless (University of Ontario)</div><div class="event_title">Structured Backward Error for the WKB method <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The classical WKB method (also known as the WKBJ method, the LG method, or the phase integral method) for solving singularly perturbed linear differential equations has never, as far as we know, been looked at from the structured backward error (BEA) point of view. This is somewhat surprising, because a simple computation shows that for some important problems, the WKB method gives the exact solution of a problem of the same structure that can be expressed in finitely many terms. This kind of analysis can be extremely useful in assessing the validity of a solution provided by the WKB method. In this paper we show how to do this and explore some of the consequences, which include a new iterative algorithm to improve the quality of the WKB solution. We also explore a new hybrid method where the potential is approximated by Chebyshev polynomials, which can be implemented in a few lines of Chebfun.This is joint work with Nic Fillion, Simon Fraser University</div><div class="event_time">15:00 &bull; Université de Genève, Conseil Général 7-9, Room 1-05</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/annonces/groupes-geometrie">Groupes et Géométrie </a></div><br /><div class="event_speaker"> Marco  Gualtieri  (Toronto)</div><div class="event_title">Groupoids, generalized Kahler structures, and (2,2) supersymmetry <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />It has recently become clear that the 2d supersymmetric sigma model has a hidden higher groupoid structure, which generalizes the appearance of the classifying stack BG in Chern-Simons theory.  I will describe our recent work on this subject in https://arxiv.org/abs/2407.00831 and outline how the higher groupoids govern the behaviour of generalized Kahler metrics.</div><div class="event_time">15:00 &bull; Université de Genève, Conseil Général 7-9, Room 1-07</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://www.math.uzh.ch/mat075.1">Zurich Graduate Colloquium</a></div><br /><div class="event_speaker">Barbara Betti (MPI MiS Leipzig)</div><div class="event_title">What is... a Khovanskii basis? <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Gröbner bases are one of the main tools in computer algebra to solve many theoretical problems. For instance, they provide algorithms to solve the ideal membership problem, to perform elimination of variables and to solve zero-dimensional polynomial systems. In this talk, we will recall some basics notions about Gröbner bases and introduce the analogous but less known Khovanskii (or Sagbi) bases. These are particularly well-behaved sets of algebra generators that allow similar algorithms on subalgebras of the polynomial ring. Unlike Gröbner bases, Khovanskii bases are not always finite. We will discuss examples and introduce applications of Khovanskii bases to solve structured equations on projective varieties (based on joint work with M.Panizzut and S. Telen).</div><div class="event_time">15:45 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 19.2</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://www.epfl.ch/labs/mathicse/">Computational Science and Engineering </a></div><br /><div class="event_speaker"> Feliks  Nüske</div><div class="event_title">Learning Metastable Dynamics: Application to Molecular Dynamics <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Metastablility is a phenomenon which often inhibits the efficient simulation of dynamical systems, or the generation of samples from high-dimensional probability measures. In particular, it is frequently encountered in computer simulations of biological macromolecules using molecular dynamics. It is well-known that metastable transitions and their time scales are encoded in the dominant spectrum of certain transition operators, also called Koopman operators. The study of Koopman operators, and their data-driven approximation by algorithms like the Extended Dynamic Mode Decomposition (EDMD), have gained significant traction in recent years.In this talk, I will report on recent progress concerning the data-driven analysis of metastable systems using Koopman operators. First, I will introduce approximation methods based on reproducing kernel Hilbert spaces (RKHS), which allow the use of rich approximation spaces, and explain how the resulting large-scale linear problems can be solved efficiently using random Fourier features (RFF). Second, I will explain how similar ideas can be applied to learn models for the infinitesimal generator, which allows for a more detailed system analysis, including interpolation across statistical ensembles, or the definition of reduced (coarse grained) models.</div><div class="event_time">16:15 &bull; EPF Lausanne, CM 1 517</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_fr"><a class="external" href="https://www.unifr.ch">Université de Fribourg</a></div><div class="event_type"><a class="external" href="https://www.unifr.ch/math/de/info/kolloquium.html">Colloquium </a></div><br /><div class="event_speaker"> Ilya Molchanov (University of Bern)</div><div class="event_title">The semigroup of metric measure spaces and its infinitely divisible measure <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The family of metric measure spaces can be endowed with the semigroup operation being the Cartesian product. The aim of this talk is to arrive at the generalisation of the fundamental theorem of arithmetics for metric measure spaces that provides a unique decomposition of a general space into prime factors. These results are complementary to several partial results available for metric spaces (like de Rham\'s theorem on decomposition of manifolds). Finally, the infinitely divisible and stable laws on the semigroup of metric measure spaces are characterised (joint work with S.N. Evans (Berkeley)</div><div class="event_time">17:15 &bull; Université de Fribourg, room Phys 2.52</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Wednesday, April 16      </div>      <div class="day_content">        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/fim/activities/nachdiplom-lectures">Nachdiplomvorlesung</a></div><br /><div class="event_speaker"> Adam Kanigowski (University of Maryland)</div><div class="event_title">Sparse Equidistribution Problems in Dynamics</div><div class="event_time">10:15 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/seminaires/lie-sem/">Lie groups and moduli spaces </a></div><br /><div class="event_speaker"> Szilard  Szabo  (Alfréd Rényi Institute of Mathematics)</div><div class="event_title">Confluence of parabolic singularities in the E6 Higgs bundle moduli space <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In an ongoing joint work with Miklos Eper, we study the degenerations of a rank 3 logarithmic Higgs bundle moduli space and the associated character variety, as the punctures collide and form irregular singularities with various irregular types. We describe the fibers at infinity of the elliptic Hitchin fibration, and present the wild character varieties as affine cubic surfaces. We use Fourier--Laplace transformation to relate the irregular connections to the Painleve moduli spaces. </div><div class="event_time">10:30 &bull; Université de Genève, Conseil Général 7-9, Room 1-07</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://www.math.uzh.ch/mat760">Ergodic theory and dynamical systems seminar</a></div><br /><div class="event_speaker">Prof. Dr. Tobias Hartnick (TU)</div><div class="event_title">An invitation to transverse dynamical systems <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We propose a general framework of transverse dynamical system which allows us to simultaneously study point processes related to lattices in locally compact groups; aperiodic tilings in locally compact groups; strata of translation surfaces. In this general context we introduce a notion of intersection space and construct an associated Siegel-Radon transform, which generalizes the classical Siegel and Siegel-Veech transforms. We discuss conditions which guarantee (square-)integrability of the image and applications of the transform to the spectral theory of tiling spaces and various counting problems. This talk is based on joint work with Michael Björklund (Chalmers).</div><div class="event_time">13:30 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 19.1</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://calendar.google.com/calendar/embed?mode=AGENDA&height=600&wkst=2&bgcolor=%23FFFFFF&src=t36it03v52cus2detrvinlgk18%40group.calendar.google.com&color=%235F6B02&ctz=Europe%2FZurich">Groups, Arithmetic and Algebraic Geometry Seminar </a></div><br /><div class="event_speaker"> Emma Brakkee</div><div class="event_title">Moduli spaces of K3 surfaces with a Brauer class <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Twisted K3 surfaces are pairs of a K3 surface together with a Brauer class. They are parametrized by moduli spaces of twisted K3 surfaces of fixed order with an ample line bundle. Over the complex numbers, one can construct these moduli spaces using Hodge theory, which we did in previous work to study the relation with cubic fourfolds. In a current joint project with D. Bragg and A. Várilly-Alvarado, we generalize the above, constructing moduli spaces of twisted K3 surfaces with a polarization by a lattice of higher rank. We use them to study the size of the transcendental parts of Brauer groups of K3 surfaces over number fields. In this talk, I will focus on the construction of these moduli spaces and what they look like over the complex numbers.</div><div class="event_time">14:00 &bull; EPF Lausanne, Bernoulli Center</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://www.epfl.ch/labs/hessbellwald-lab/seminar/epfl-topology-seminar-fall-2024/">Séminaire de Topologie </a></div><br /><div class="event_speaker"> Bastian Rieck (University of Fribourg)</div><div class="event_title"><a class="external" href="https://www.epfl.ch/labs/hessbellwald-lab/3141-2/">From Coarse to Fine and Back Again: Geometry, Topology, and Deep Learning</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />A large driver contributing to the success of deep-learning models is their ability to synthesize task-specific features from data, which typically outshine hand-crafted features. Thus, for a long time, the predominant belief was that “given enough data, all features can be learned.” However, it turns out that certain tasks require imbuing models with inductive biases such as invariance or equivariance properties that cannot be readily gleaned from the data! This is particularly true for data sets that model real-world phenomena, including those that involve relations beyond the dyadic, creating a crucial need for different approaches.In this talk, I will present novel advances in harnessing multi-scale geometrical-topological characteristics of data, focusing in particular on how the tandem of geometry and topology can improve (un)supervised tasks in representation learning. Underscoring the generality of a hybrid geometrical-topological perspective, I will furthermore showcase applications from a diverse set of data domains, including point clouds, graphs, and higher-order combinatorial complexes.</div><div class="event_time">14:15 &bull; <a class="external" href="https://plan.epfl.ch/?room==CM%201%20416">EPF Lausanne</a></div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/geometry-seminar">Geometry Seminar</a></div><br /><div class="event_speaker"> Jeremy Tyson (University of Illinois Urbana-Champaign)</div><div class="event_title">Dimension interpolation and conformal dimension <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The conformal dimension of a metric space $(X,d)$ measures its optimal shape from the perspective of quasiconformal geometry. It is defined by infimizing dimension over metrics in the quasisymmetric equivalence class of $d$. Introduced by Pierre Pansu in 1989, conformal Hausdorff dimension played an important early role in the development of analysis on metric spaces. Subsequently a variant notion, conformal Assouad dimension, gained prominence. Assouad dimension—which bounds Hausdorff dimension from above—is a scale-invariant, quantitative measurement of optimal coverings of a space. Dimension interpolation is an emerging program of research in fractal geometry which identifies geometrically natural one-parameter dimension functions interpolating between existing concepts. Two exemplars are the Assouad spectrum (Fraser-Yu, 2015), which interpolates between box-counting and Assouad dimension, and the intermediate dimensions (Falconer-Fraser-Kempton, 2020), which interpolate between Hausdorff and box-counting dimension. In this talk, I’ll discuss the mapping-theoretic properties of intermediate dimensions and the Assouad spectrum, with applications to the quasiconformal classification of sets and to the range of conformal Assouad spectrum. The latter results are based on a recent joint project with Efstathios Chrontsios Garitsis (Univ of Tennessee) and an ongoing collaboration with Jonathan Fraser (Univ of St. Andrews).</div><div class="event_time">15:30 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://memento.epfl.ch/event/probability-and-stochastic-analysis-seminar/">Probability (and Stochastic Analysis) Seminar </a></div><br /><div class="event_speaker"> Robert A. Crowell (ETH)</div><div class="event_title">McKean—Vlaosv SDEs: New results on existence of weak solutions and on propagation of chaos <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We consider the existence of weak solutions of McKean-Vlasov SDEs with common noise and the propagation of chaos for the associated weakly interacting finite particle systems. Our strategy consists of two main components allowing us to analyze settings with general nonlinear but uniformly elliptic coefficients possessing only low spatial regularity through a marriage of probabilistic and analytic techniques. First, we explore the emergence of regularity in limit points of McKean-Vlasov particle systems, leading to a priori regularity estimates for large-system limits of the empirical measure flows from finite particle systems. Second, we leverage this regularity to establish the existence of weak solutions for McKean-Vlasov SDEs and to identify more nuanced conditions under which chaos propagates, i.e. under which an asymptotic decoupling of the particles takes place and the dynamics in large systems become conditionally independent in law. Next to its applicability to low-regularity regimes, the approach we take to obtain weak solutions and the propagation of chaos may also be useful in future applications to mean-field games and controlled problems.</div><div class="event_time">16:00 &bull; EPF Lausanne, Bernoulli Center, GA 3 34</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://www.epfl.ch/labs/mathicse/">Computational Science and Engineering </a></div><br /><div class="event_speaker"> Raul  Tempone (KAUST - King Abdullah University Of Science And Technology, Arabie saoudite)</div><div class="event_title">Uncertainty Quantification and Stochastic Optimal Control: Navigating Complexity in Forecasting and Decision-Making <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In the era of data-driven decision-making, accurately quantifying and managing uncertainty is crucial across scientific and engineering disciplines. This talk introduces recent methodological advancements in Uncertainty Quantification (UQ) and Stochastic Optimal Control (SOC), highlighting novel computational techniques and their relevance in critical real-world scenarios.In the first part, we discuss innovative UQ methods applied to complex systems, modeling the forecast error using Stochastic Differential Equations (SDEs). We present a data-driven approach that effectively quantifies uncertainties with concrete applications to renewable energy forecasting (wind and solar photovoltaic power). We also demonstrate a post-hoc UQ strategy for enhancing reliability in machine-learning-based biomedical image segmentation, specifically for estimating left ventricle volumes in cardiac MRI.The second part of this talk focuses on recent methodological developments in SOC. Here, we present a framework for continuous-time stochastic optimal control under discrete-time partial observations, where control decisions integrate noisy measurements through a Bayesian update characterized by interlaced Hamilton–Jacobi–Bellman (HJB) equations with an infinite dimensional state.</div><div class="event_time">16:15 &bull; EPF Lausanne, GC D0 386</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Thursday, April 17      </div>      <div class="day_content">        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/number-theory-seminar">Number Theory Seminar</a></div><br /><div class="event_speaker">Dr. Arthur Forey (Université de Lille)</div><div class="event_title">An orbifold formula for Artin stacks <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Let G be a finite subgroup of SL_2. The McKay correspondence relate therepresentation theory of G to the geometry of the quotient X of C^2 bythe action of G. An avatar of this correspondence has been studied byBatyrev and later Denef-Loeser. They show that the p-adoc or motivicvolume of X can be explicitly computed as a sum over conjugacy classesof G. Yasuda reinterprets this sum in terms of the inertia of theDeligne-Mumford stack associated to this quotient. I will present ageneralization of this formula to the case of a quotient of a smoothvariety by a general linear group. This is joint work with FrançoisLoeser and Dimitri Wyss.</div><div class="event_time">14:15 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://calendar.google.com/calendar/embed?mode=AGENDA&height=600&wkst=2&bgcolor=%23FFFFFF&src=t36it03v52cus2detrvinlgk18%40group.calendar.google.com&color=%235F6B02&ctz=Europe%2FZurich">Groups, Arithmetic and Algebraic Geometry Seminar </a></div><br /><div class="event_speaker"> Joni Teravainen</div><div class="event_title">Title T.B.A.</div><div class="event_time">14:15 &bull; EPF Lausanne</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://k-os.math.ethz.ch">[K-OS] Knot Online Seminar</a></div><br /><div class="event_speaker"> Jae Choon Cha (POSTECH)</div><div class="event_title">On Calegari’s homotopy 4-spheres <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In 2009, in connection with the smooth 4-dimensional Poincaré conjecture, D. Calegari constructed an infinite family of smooth homotopy 4-spheres arising from monodromies of fibered knots in the 3-sphere. We review this construction and prove that all of these are diffeomorphic to the standard 4-sphere. We also discuss some related applications.</div><div class="event_time">16:15 &bull; <a class="external" href="https://u-paris.zoom.us/j/87853056962">online</a></div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/annonces/colloque">Colloque de Mathématiques </a></div><br /><div class="event_speaker"> Rob Corless (University of Western Ontario)</div><div class="event_title">Gamma and Factorial in the Monthly <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />By 2016, the American Mathematical Monthly had published roughly fifty papers on the &#915; function or Stirling\'s formula. We survey those papers (discussing only our favourites in any detail) and place them in the context of the larger mathematical literature on &#915;. We also discuss a surprising blank spot: there had been very little published work on the functional inverse of this function. This omission has been rectified somewhat, since.</div><div class="event_time">16:15 &bull; Université de Genève, Conseil Général 7-9, Room 1-15</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/talks-in-financial-and-insurance-mathematics">Talks in Financial and Insurance Mathematics</a></div><br /><div class="event_speaker">Dr. Gechun Liang (University of Warwick)</div><div class="event_title">Convergence Rates of the Universal Robust Limit Theorem for Nonlinear Lévy Processes under Sublinear Expectations: A Monotone Scheme Analysis <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The Feynman-Kac formula bridges PDEs and probability theory by providing a probabilistic representation of PDE solutions, connecting the convergence of numerical schemes for PDEs to limit theorems in stochastic processes. In this talk, we extend this paradigm beyond linear frameworks to sublinear expectations—known as Peng’s G-expectations. We establish convergence rates for the Universal Robust Limit Theorem, including central limit theorems, laws of large numbers, and alpha-stable limit theorems, all under the sublinear expectation framework. Our analysis leverages the monotone scheme analysis of viscosity solutions to fully nonlinear second-order PIDEs associated with nonlinear Lévy processes. Based on joint work with Mingshang Hu and Lianzi Jiang.</div><div class="event_time">17:15 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Friday, April 18      </div>      <div class="day_content">        <div class="day_content_item no_event">        No events scheduled today!        </div>      </div>    </div>  </div>  <div id="sms_footer">    address: Alessandra Naldi Windler, Departement Mathematik, HG G 51.4, ETH Zurich, Raemistrasse 101, CH-8092 Zurich<br />    email: <a href="mailto:bulletin@math.ch">bulletin@math.ch</a> | phone: +41 44 632 3684 | url: <a href="https://math.ch">https://math.ch</a>    <br /><br /><img src="//www2.math.ethz.ch/smsjs/sms_logo.gif" width="150" alt="SMS/SMG Logo" title="SMS/SMG Logo" />  </div></div>';