var sms = '<div id="sms_bulletin">  <div id="sms_header">  <div class="do_not_print" id="arrow_left"><a href="?next=-2"><img src="//www2.math.ethz.ch/smsjs/images/arrow_left.png"/></a></div><div class="do_not_print" id="arrow_right"><a href="?next=0"><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. 8</span>      <span style="float: right; text-align:right; width: 250px;">7.4 - 11.4.2025</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 7      </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"> Victor Chachay (Dijon)</div><div class="event_title"><a class="external" href="https://dmi.unibas.ch/de/studium/mathematik/doktorat/bernoullis-tafelrunde/detail/bernoullis-tafelrunde-victor-chachay-dijon/">Counting lines on surfaces, how to make the base field not matter anymore?</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In algebraic geometry, counting lines contained in surfaces is an old habit. However, in some cases doing so for a variety defined over a non-algebraically closed field (say R instead of C) brakes a wonderful invariant result to one depending on the surface! There are some "by hand" ways to go around this problem using geometric properties of the surface (apart from counting a line whenever found). We\'ll see how people translated these counting techniques to a more global setup (motivic homotopy and Grothendieck-Witt groups) to recover an invariant result of surfaces and (almost) fields. 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_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://theory.epfl.ch/seminar/">Theory and Combinatorics Seminar</a></div><br /><div class="event_speaker"> Matteo Russo</div><div class="event_title"> A Tight VC-Dimension Analysis of Clustering <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We consider coresets for $k$-clustering problems (such as $k$-median,$k$-means, and $k$-center), where the objective is to assign points tocenters while minimizing distance-based costs. Given a point set $P$, acoreset $C$ is a small weighted subset that approximates the cost of $P$for all candidate solutions $S$ within a $(1\\pm\\varepsilon)$multiplicative factor. The existence of a coreset for a problem enablesan algorithmic framework that first compresses large datasets intocompact representations before applying an algorithm. By preservingessential information while reducing data size, this approach enhancescomputational efficiency, facilitates polynomial-time approximationschemes, and enables efficient streaming solutions.  We provide tight bounds on the coreset size in terms of theVC-dimension of the metric space at hand. As a consequence, we obtainimproved $k$-median coreset bounds for the following metrics:- Coresets of size $\\Tilde{O}\\left(k\\varepsilon^{-2}\\right)$ forshortest path metrics in planar graphs and graphs with a fixed excludedminor;-Coresets of size $\\Tilde{O}\\left(kd\\ell\\varepsilon^{-2}\\log m\\right)$for clustering $d$-dimensional polygonal curves of length at most $m$with curves of length at most $\\ell$ with respect to Frechet metrics.  This is joint work with Vincent Cohen-Addad, Andrew Draganov, DavidSaulpic and Chris Schwiegelshohn.</div><div class="event_time">12:15 &bull; EPF Lausanne, INJ114</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://uzh.ch">Universit&auml;t 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"> Coline Emprin (Ecole Normale Supérieure de Paris)</div><div class="event_title">Kaledin classes and formality criteria <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />A differential graded algebraic structure A (e.g. anassociative algebra, a Lie algebra, an operad, etc.) is formal if it isrelated to its homology H(A) by a zig-zag of quasi-isomorphismspreserving the algebraic structure. Kaledin classes were introduced asan obstruction theory fully characterizing the formality of associativealgebras over a characteristic zero field. In this talk, I will presenta generalization of Kaledin classes to any coefficients ring, to otheralgebraic structures (encoded by operads, possibly colored, or byproperads), and to address a more general problem: the existence ofhomotopy equivalences between algebraic structures. I will prove newformality criteria based on this obstruction theory, presentingapplications in several domains such as algebraic geometry,representation theory and mathematical physics.</div><div class="event_time">13:30 &bull; UZH Irchel, 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"> Maksim Stokic</div><div class="event_title">C&#8304;-Contact Geometry of Smooth Submanifolds <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />A contact homeomorphism is defined as a C&#8304;-limit of a sequence of contact diffeomorphisms. In this talk, we will discuss C&#8304;-flexibility and C&#8304;-rigidity properties of various classes of submanifolds in the contact setting. Our primary focus will be on Legendrian submanifolds, which exhibit C&#8304;-rigidity in the closed case and C&#8304;-flexibility in the open case. More precisely, we will focus on the following question: if a contact homeomorphism maps a Legendrian submanifold to a smooth submanifold, must the image necessarily be Legendrian?</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"> Johannes Gutenberg (University Mainz)</div><div class="event_title">Gaussian free field on the tree subject to a hard wall constraint <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We consider the Gaussian free field on a binary tree (also known as branching random walk) under the constraint that the values at all leaves at generation n are non-negative.  We obtain a remarkably precise description of the conditional law and the conditional field. The conditioning leads to an upward shift of the whole field. We obtain sharp estimates on this upward shift (up to o(1) terms). We show that the properly rescaled maximum converges to a Gumbel distribution (without a random shift!), and the rescaled minimum is exponentially distributed. We use tools from DGFFs on general graphs and estimates on random walks that are weakly attracted to zero either through a pinning potential or a drift. The talk is based on joint work with M. Fels (Technion) and O. Louidor (Technion).</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. Tyson Jeremy (University of Ilinois)</div><div class="event_title"><a class="external" href="https://www.math.unibe.ch/research/talks/colloquium/index_eng.html">Dimension interpolation and conformal dimension</a> <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 by linking this emerging subject to the coarse geometry of Gromov hyperbolic groups. In later years a variant notion, conformal Assouad dimension, gained prominence. Assouad dimension—which bounds Hausdorff dimension from above—is a scale-invariant, quantitative measurement of the size of optimal coverings of a space. Intermediate between these two is Minkowski (box-counting) dimension. 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 highlight a few significant milestones in the theory of conformal dimension, concluding with recent applications of dimension interpolation to the quasiconformal classification of sets and the range of conformal Assouad spectrum. The latter results are joint work with Efstathios Chrontsios Garitsis (Univ of Tennessee) and Jonathan Fraser (Univ of St. Andrews).</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 8      </div>      <div class="day_content">        <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.unil.ch/dsa/en/home/menuinst/seminaires--evenements/research-seminars.html">Talks in Actuarial Mathematics </a></div><br /><div class="event_speaker"> Pierre-Olivier  Goffard  (Université de Strasbourg)</div><div class="event_title">Collaborative and parametric insurance on the Ethereum blockchain <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br /> I will present a blockchain-based insurance scheme that integrates parametric and collaborative elements. A pool of investors, referred to as surplus providers, locks funds in a smart contract, enabling blockchain users to underwrite parametric insurance contracts. These contracts automatically trigger compensation when predefined conditions are met. The collaborative aspect is embodied in the generation of tokens, which are distributed to both surplus providers and policyholders. These tokens represent each participant\'s share of the surplus and grant voting rights for management decisions. The smart contract is developed in Solidity, a high-level programming language for the Ethereum blockchain, and deployed on the Sepolia testnet, with data processing and analysis conducted using Python. I will discuss both the technical details as well as the actuarial aspects. </div><div class="event_time">11:00 &bull; EPF Lausanne, Extranef 125</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"> Manel  Tayachi-Pigeonnat (University of Grenoble)</div><div class="event_title">Design and analysis of a Schwarz coupling method for 3D Navier-Stokes equations and 2D Shallow Water equations <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />When dealing with the simulation of complex physical phenomena and in order to avoid heavy numerical simulations, one can reduce a complex model in some locations and replace it, if the physics allow it, by simpler ones usually obtained after simplifications. Such simplifications in the model may involve a change in the geometry and the dimension of the physical domain. In that case, one deals with dimensionally heterogeneous coupling problems. First, I will present briefly an iterative method to couple the 2-D Laplace equation with a corresponding 1-D Laplace equation. This simple case will allow us to understand the main questions that we have to face when dealing with the coupling of dimensionally heterogeneous models and when using a Schwarz-like algorithm in this context. Then, I consider the case of 3D linearized hydrostatic Navier-Stokes equations coupled with corresponding 2D linearized shallow water equations. I will show briefly how to derive the 2D linearized shallow water system from the 3D linearized hydrostatic Navier-Stokes system. Then a Schwarz-like algorithm to couple the twosystems is proposed and studied. I will show that under some assumptions, the convergence of thisSchwarz algorithm is equivalent to the convergence of the classical domain decomposition algorithmof shallow water equations. Finally, some theoretical results related to the control of the differencebetween the global 3D reference solution and the 3D part of the coupled solution are given. Theseresults are illustrated numerically. This is a joint work with Céline Acary-Robert and Eric Blayo (Inria Grenoble and LJK).</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_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"> Ilario  Mazzieri (Polytecnico di Milano)</div><div class="event_title">Space-time RAS discretization of wave problems on polytopal meshes <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The numerical simulation of wave propagation presents significant challenges, particularly when dealing with complex geometries, heterogeneous media, and high-frequency regimes. Traditional time-stepping methods often struggle with achieving high-order accuracy while maintaining computational efficiency. In this talk, we introduce a space-time Restricted Additive Schwarz (XT-RAS) method tailored for discontinuous Galerkin (dG) discretizations of wave problems on polytopal meshes. This approach provides a parallelizable framework that enhances computational performance while preserving high-order accuracy in both space and time. Additionally, we address the computational complexity introduced by the higher dimensionality of space-time discretizations and propose an efficient domain decomposition strategy that improves scalability and reduces computational costs. Numerical experiments validate the effectiveness of our XT-RAS approach, demonstrating its ability to accelerate wave simulations while maintaining robustness across different problem configurations. Finally, we discuss potential extensions, including adaptive strategies for time subdomain selection and applications to more complex multi-physics problems.</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_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/analysis-seminar">Analysis Seminar</a></div><br /><div class="event_speaker">Prof. Dr. Antoine  Gloria (Sorbonne )</div><div class="event_title">Homogenization of the 2d Euler system in porous media <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In this talk I will discuss some homogenization results for the 2D Euler equations with impermeable inclusions. The main difficulty is the homogenization of the transport equation for the vorticity. In particular, localization of the latter could rule out separation of scales. Our approach combines classical results from different areas to prevent such phenomena and prove homogenization towards a variant of the Euler system: homogenization of elliptic systems with stiff inclusions, unique ergodicity for dynamical systems, and variants of the Rado-Kneser-Choquet theorem. I will conclude with some open problems. This is joint work with Mitia Duerinckx (ULB).</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_zh"><a class="external" href="https://uzh.ch">Universit&auml;t 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">Jasmin Jörg (Unversität Bern)</div><div class="event_title">What is... the crossing number of curves on surfaces? <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Fixing a closed surface and a number \\(k\\), we ask: How many crossings do any \\(k\\) non-homotopic simple closed curves on the surface necessarily create? In this talk, we focus on small minimising systems on a surface of genus 2 and relate them to optimal curve systems appearing in other contexts. If time allows, we discuss more general results concerning higher genus surfaces and asymptotic behaviour.</div><div class="event_time">16:30 &bull; UZH Zentrum, Building KO2, Room F 150</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"> Jeremy Tyson (University of Illinois)</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 by linking this emerging subject with the coarse geometry of Gromov hyperbolic groups. In later years a variant notion, conformal Assouad dimension, gained prominence. Assouad dimension—which bounds Hausdorff dimension from above—is a scale-invariant, quantitative measurement of the size of optimal coverings of a space. Intermediate between these two is Minkowski (box-counting) dimension. 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 highlight a few significant milestones in the theory of conformal dimension, concluding with recent applications of dimension interpolation to the quasiconformal classification of sets and the range of conformal Assouad spectrum. The latter results are based on joint work with Efstathios Chrontsios Garitsis (Univ Tennessee) and Jonathan Fraser (Univ of St. Andrews).</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 9      </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 cancelled"><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://theory.epfl.ch/seminar/">Theory and Combinatorics Seminar</a></div><br /><div class="event_speaker"> Abhishek Shetty </div><div class="event_title">CANCELLED: Discrepancy and Compression: Two Perspectives <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Discrepancy theory has been an area that has recently seen a lot of activity due to algorithmic progress on longstanding open problems. This has opened up connections in diverse areas such as machine learning, probability theory, convex geometry and communication complexity. In this talk, we will focus on some new perspectives on a classical connection between discrepancy theory and compression. In the first part of the talk, we will focus on a connection between discrepancy and one-way communication complexity. In particular, we will show that certain natural question in discrepancy i.e. (Matrix) Spencer problem are equivalent to the one-way (Quantum) communication complexity of a natural communication problem (the indexing problem). Using this connection, we will see applications to the Matrix Spencer conjecture. In the second part of the talk, we will see application of algorithmic discrepancy theory to the problem of distribution compression, i.e. the task of producing a small representative data set that approximates a distribution. We will see general algorithms in this setting that lead to diverse applications such as speeding up testing and optimization and approximating attention.</div><div class="event_time">11:15 &bull; EPF Lausanne, BC129</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. Kostiantyn Drach (Universitat de Barcelona/CRM-Barcelona)</div><div class="event_title">(Unmarked) Length spectral rigidity for expanding circle maps <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />For a smooth expanding map of the circle, its (unmarked) length spectrum is defined as the set of logarithms of multipliers along all periodic orbits. This set is analogous to the set of lengths of all closed geodesics on negatively curved surfaces -- the classical length spectrum. In the talk, I will present a length spectral rigidity result for expanding circle maps. Namely, I will show that a smooth expanding circle map, under certain assumptions on the sparsity of its length spectrum, cannot be perturbed with an arbitrarily small smooth perturbation (depending on the map) so that the length spectrum stays the same. The proof uses the Whitney extension theorem, a quantitative Livcis-type theorem, and a novel iterative scheme. This is joint work with Vadim Kaloshin.</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_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/algebraic-geometry-and-moduli-seminar">Algebraic Geometry and Moduli Seminar</a></div><br /><div class="event_speaker"> Zhiyu Liu (Zhejiang Univeristy and ETH-ITS)</div><div class="event_title">Irreducible symplectic varieties with a large second Betti number <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Irreducible symplectic varieties are one of three building blocks of varieties with Kodaira dimension zero, which are higher-dimensional analogs of K3 surfaces. Despite their rich geometry, there have been only a limited number of approaches to construct irreducible symplectic varieties. In this talk, I will introduce a general criterion for the existence of irreducible symplectic compactifications of non-compact Lagrangian fibrations, based on the minimal model program and the geometry of Lagrangian tori. As an application, I will explain how to get a 42-dimensional irreducible symplectic variety with the second Betti number at least 24. This is a joint work with Yuchen Liu and Chenyang Xu.</div><div class="event_time">13:30 &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://www.epfl.ch/labs/hessbellwald-lab/seminar/epfl-topology-seminar-fall-2024/">Séminaire de Topologie </a></div><br /><div class="event_speaker"> Johannes Schipp von Branitz (University of Nottingham)</div><div class="event_title"><a class="external" href="https://www.epfl.ch/labs/hessbellwald-lab/3141-2/">An Informal Introduction to Homotopy Type Theory via Synthetic Homotopy Theory</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Homotopy type theory is an intuitionistic type theory with the aspiration of becoming a foundation for all of mathematics. In this talk we introduce the basic type theoretic constructions and their semantic interpretation in an infinity topos, before discussing the synthetic analogues of classical homotopy theoretic constructions such as Eilenberg-MacLane spacesand Whitehead\'s theorem.</div><div class="event_time">14:15 &bull; <a class="external" href="https://plan.epfl.ch/?room==CM%201%20517">EPF Lausanne</a></div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://uzh.ch">Universit&auml;t Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://www.math.uzh.ch/aa/?events">Neuchatel - St.Gallen - Zurich Seminar in Coding Theory and Cryptography</a></div><br /><div class="event_speaker">Samed Düzlü (Universität Regensburg)</div><div class="event_title">Automorphic Forms and Cryptographic Lattice Problems <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In lattice-based cryptography, one of the most popular approaches to increase efficiency is to attach structures to lattices. These structures usually come from algebraic number theory: For instance, taking fractional ideals of number fields become lattices inside the associated Minkowski space, on which the ring of integers act by multiplication. Extending this idea, module lattices are defined by taking submodules over the ring of integers inside an m-dimensional vector spaces over the number field. As the structures involve these algebraic number theoretic notions, it seems natural to analyze the corresponding lattice problems using number theoretic techniques. De Boer et al. (CRYPTO&#039;20) carried out this strategy for ideal lattices: Fixing a number field, the set of ideal lattices (up to scaling) is a compact commutative Lie group. Cryptographic problems on the ideal lattices can be translated to the study of the space of ideal lattices. We explain this approach by a slight reformulation in terms of adeles and ideles. Then, the natural generalization of the idele class group to GL(m) corresponds immediately to the class of module lattices of rank m, for the same fixed number field. We describe this correspondence and explain the building blocks to generalize the results of de Boer et al. to module lattices of higher ranks. We finish with a partial result and explanation of the obstacles to conclude an effective solution.</div><div class="event_time">15:15 &bull; UZH Irchel, Winterthurerstrasse 190, Z&uuml;rich, Building Y27, Room H 28</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"> Anthony Genevois (Institut Montpellierain Alexander Grothendieck)</div><div class="event_title">Quasi-median graphs, right-angled Artin groups, and homotopy <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />After a general introduction to applications of metric graph theory in geometric group theory, focused on quasi-median graphs, I will explain how one can deduce from such a perspective new quasi-isometric invariants for right-angled Artin groups. This is joint work with Carolyn Abbott and Eduardo Martinez-Pedrosa.</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_be"><a class="external" href="https://www.unibe.ch">Universität Bern</a></div><div class="event_type"><a class="external" href="https://www.imsv.unibe.ch/research/talks/colloquia/index_eng.html">Colloquia on Probability and Statistics </a></div><br /><div class="event_speaker">Prof. Dr. Christopher Criscitiello</div><div class="event_title"><a class="external" href="https://www.imsv.unibe.ch/research/talks/schedule/index_eng.html">Curvature and complexity: Lower bounds for geodesically convex optimization</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Some optimization problems encountered in practice are non-convex, but become geodesically convex (g-convex) when the search space is endowed with the right Riemannian metric.  Examples from statistics include Tyler\'s M-estimator for robust covariance estimation, and maximum likelihood estimators for matrix and tensor normal models.  Further instances arise in theoretical computer science (e.g., noncommutative polynomial identity testing), quantum information (e.g., tensor scaling), and pure mathematics (e.g., Brascamp-Lieb constants).Motivated by these applications, we investigate the query complexity of geodesically convex optimization.  Our main result is a lower bound showing that the curvature of the search space fundamentally increases the difficulty of g-convex optimization compared to its Euclidean counterpart.  This, in turn, rules out the possibility of Nesterov acceleration on manifolds, in certain regimes.  It also has implications for tensor scaling and related problems.The talk will begin with motivating applications from statistics, followed by a brief review of the necessary geometric tools.  We then present the lower bounds, provide intuition for their validity, and explore their consequences for downstream tasks.</div><div class="event_time">16:15 &bull; Universität Bern, IMSV, Alpeneggstrasse 22, 3012 Bern, Hörraum -203</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/sam/news-and-events/zhacm-colloquia">Zurich Colloquium in Applied and Computational Mathematics</a></div><br /><div class="event_speaker">Prof. Dr. Michael Dumbser (University of Trento)</div><div class="event_title">On well-balanced finite difference, finite volume and discontinuous Galerkin schemes for the Einstein-Euler system of general relativity</div><div class="event_time">16:30 &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_zh"><a class="external" href="https://uzh.ch">Universit&auml;t Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/seminar-on-stochastic-processes">Seminar on Stochastic Processes</a></div><br /><div class="event_speaker">Dr. Alejandro Rosales Ortiz  (Universität Zürich, Switzerland)</div><div class="event_title">Graduate Workshop Reinforcement</div><div class="event_time">17:15 &bull; UZH Irchel, Winterthurerstrasse 190, Z&uuml;rich, Building Y27, Room  H12</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Thursday, April 10      </div>      <div class="day_content">        <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"> Tudor Padurariu (Sorbonne)</div><div class="event_title">Cohomology of symmetric stacks <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />I will talk about a joint project with Chenjing Bu, Ben Davison, Andrés Ibáñez-Núñez, and Tasuki Kinko.For a large class of stacks, we decompose their cohomology in BPS cohomology, which is a structure originating in enumerative geometry of Calabi-Yau 3-folds, but which is of interest beyond this class of examples. Such stacks include smooth stacks (such as the moduli of G-bundles on a curve), symplectic stacks (such as the moduli of G-Higgs bundle on a curve), or (-1)-shifted symplectic stacks (such as the moduli of semistable sheaves on a Calabi-Yau threefold). In the pre-talk, I plan to discuss the local structure of the moduli of semistable vector bundles on a curve, and properties of vanishing cycles.  In the talk, I will explain the proof of the main theorem for the example of rank 2 and degree 0 semistable vector bundles on a curve (which was already treated by Meinhardt and Mozgovoy-Reineke). I will then introduce BPS cohomology and state the theorem for (-1)-shifted and 0-shifted symplectic stacks. Time permitting, I will explain conjectural applications of BPS cohomology in Langlands duality for compact real oriented 3-manifolds (following Ben-Zvi-Gunningham-Jordan-Safronov). BPS cohomology can be also used to state a version of topological mirror symmetry for G-Higgs bundles (for general reductive groups G).</div><div class="event_time">13:15 &bull; EPF Lausanne, CM 1 517</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/daco-seminar">DACO Seminar</a></div><br /><div class="event_speaker">Dr. Mitchell Taylor (ETH Z&uuml;rich, Switzerland)</div><div class="event_title">Recent advances in the phase retrieval problem <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In many physical experiments, detectors are only able to measure the intensity of a signal and hence loseaccess to the phase. The phase retrieval problem deals with the reconstruction of a signal from magnitudemeasurements, assuming certain physical constraints are satisfied. In this talk, I will briefly discuss thehistory of this problem and overview some recent progress on proving rigorous stability bounds in infinitedimensions.</div><div class="event_time">14:15 &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_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/zahlentheorie/">Seminar Zahlentheorie</a></div><br /><div class="event_speaker"> Gabriel Dill (Université Neuchâtel)</div><div class="event_title"><a class="external" href="https://dmi.unibas.ch/de/news-events/detail/number-theory-seminar-gabriel-dill-universite-neuchatel/">Title T.B.A.</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Titel: Points of small height and where to find them - a group-theoretic criterion Abstract: The height of an algebraic number is a measure for its arithmetic complexity. While numbers of height zero are classified by Kronecker\'s theorem (they are precisely 0 and the roots of unity), many questions remain open about numbers of small but non-zero height. The famous conjecture of Lehmer predicts an essentially best possible lower bound for the height of such numbers. A related question is whether, given an algebraic extension of the rationals, it contains numbers of arbitrarily small height. Rémond formulated a generalization of Lehmer\'s conjecture, which yields a characterization of points of small height on abelian varieties or algebraic tori that are defined over some infinite algebraic extensions of the rational numbers, generated by the division points of certain finitely generated subgroups. For instance, the field generated over the rationals by all roots of 2 contains some obvious points of very small height (0, small fractional powers of 2 multiplied by roots of unity) and the conjecture implies that it contains no others. If the finitely generated subgroup is of positive rank, then even weaker versions of Rémond\'s conjecture (analogues of Dobrowolski\'s theorem) are wide open. Recently, Pottmeyer identified a necessary group-theoretic condition for Rémond\'s conjecture to hold and showed that it is satisfied for the multiplicative group. In joint work in progress with Sara Checcoli, we show that Pottmeyer\'s condition is also satisfied for arbitrary almost split semiabelian varieties, using results from Kummer theory. Spiegelgasse 5, Seminarraum 05.002</div><div class="event_time">14:15 &bull; Universität Basel</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"> Livia Campo (University of Vienna)</div><div class="event_title">Flags on Fano 3-fold hypersurfaces <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The existence of Kaehler-Einstein metrics on Fano 3-folds can be determined by studying lower bounds of stability thresholds. An effective way to verify such bounds is to construct flags of point-curve-surface inside the Fano 3-folds. This approach was initiated by Abban-Zhuang, and allows us to restrict the computation of bounds for stability thresholds only on flags. We employ this machinery to prove K-stability of terminal quasi-smooth Fano 3-fold hypersurfaces. This is deeply intertwined with the geometry of the hypersurfaces: in fact, birational rigidity and superrigidity play a crucial role. The superrigid case had been attacked by Kim-Okada-Won. In this talk I will discuss the K-stability of strictly rigid Fano hypersurfaces via Abban-Zhuang Theory. This is a joint work with Takuzo Okada.</div><div class="event_time">15:15 &bull; EPF Lausanne</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"> Colin  Guillarmou  (Orsay)</div><div class="event_title">Probabilistic construction of the Wess-Zumino-Witten SL_2(C)/SU(2) model <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The WZW model with target space the hyperbolic 3 space H^3=SL_2(C)/SU(2) is a conformal field theory with central charge c>3 that has been studied in physics by Gawedski, Kupiainen, Teschner, Schomerus, Ribault … In particular, it has been shown in physics that there is an intriguing correspondence with Liouville CFT. It can be thought of as a quantization of the SL_2(C) unitary connections on a rank 2 holomorphic vector bundle on a surface, the critical point being the flat connections.I will explain how to define rigorously the path integral and correlation functions using probability, and how to prove the correspondence with Liouville.Probabilistically it essentially corresponds to the non-linear sigma model with target space the hyperbolic 3 space H^3. This is joint work with Kupiainen and Rhodes.</div><div class="event_time">16:00 &bull; EPF Lausanne, Bernoulli</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Friday, April 11      </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"> Boris Bukh (Carnegie Mellon University)</div><div class="event_title">Discrete Geometry</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_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">Prof. Dr. William Duke (UCLA)</div><div class="event_title">A Diophantine divisor function <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />I will describe recent work joint with Olga Balkanova and Dmitry Frolenkov on a restricted divisor function and its associated divisor problem. This problem shares properties with the usual Dirichlet divisor problem  and the Hardy-Littlewood problem to count lattice points in a right triangle. The latter depends deeply on the arithmentic nature of the slope of the triangle the restricted divisor problem  has a similar property. For the H-L problem, Hecke showed how to go much further when the slope comes from a real quadratic field.  We apply Hecke’s idea to our problem, which introduces a number of interesting new difficulties,</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_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://stat.ethz.ch/events/zukost">ZueKoSt: Seminar on Applied Statistics</a></div><br /><div class="event_speaker"> Victoria Stodden (University of Southern California)</div><div class="event_title">Leveraging AI in Scientific Research: Transparency, Reproducibility, and Trust <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In the last 10 years colossal cloud infrastructure investments behind the rise of near-ubiquitous global mobile technologies have trickled down to scientific research through innovative infrastructure including cloud compute and storage, I/O tools, data analysis and modeling frameworks, which in turn have generated broad and expanding communities of users and supporters. Arguably, the recent success of Large Language Models were catalyzed by the resulting technological innovations of 1) open and accessible massive data, and 2) re-executable discovery pipelines for model estimation and prediction. These changes are deeply disruptive to the research community since they open new paths to knowledge creation that were previously inaccessible and largely culturally unknown.The scientific community is faced with the challenge of responding to changes in research modalities due to these technological innovations. Research is now conducted as an “Olympics” of benchmarked competitions between Machine Learning models leveraged by the opaque results of Large Language Models, access to massive data, and redeployment of complex scientific discovery workflows. In this seminar I provide a roadmap of challenges and responses by various stakeholders in the research community to ensure that scientific results remain reliable and reproducible, and secure within a position of trust in the broader society.</div><div class="event_time">15:15 &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://www.epfl.ch/schools/sb/research/math/statistics-seminars/">Statistics Seminar </a></div><br /><div class="event_speaker"> Cecilia Balocchi (University of Edinburgh)</div><div class="event_title">Improving uncertainty quantification in Bayesian cluster analysis <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The Bayesian approach to clustering is often appreciated for its ability to provide uncertainty in the partition structure. However, summarizing the posterior distribution over the clustering structure can be challenging. Wade and Ghahramani (2018) proposed to summarize the posterior samples using a single optimal clustering estimate, which minimizes the expected posterior Variation of Information (VI).  In instances where the posterior distribution is multimodal, it can be beneficial to summarize the posterior samples using multiple clustering estimates, each corresponding to a different part of the space of partitions that receives substantial posterior mass.In this work, we propose to find such clustering estimates by approximating the posterior distribution in a VI-based Wasserstein distance sense. An interesting byproduct is that this problem can be seen as using the k-means algorithm to divide the posterior samples into different groups, each represented by one of the clustering estimates.Using both synthetic and real datasets, we show that our proposal helps to improve the understanding of uncertainty, particularly when the data clusters are not well separated, or when the employed model is misspecified.</div><div class="event_time">15:15 &bull; EPF Lausanne, CM 1 517</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/algebraic-geometry-and-moduli-seminar">Algebraic Geometry and Moduli Seminar</a></div><br /><div class="event_speaker"> Terry Song (Cambridge University)</div><div class="event_title">Topology of genus one mapping spaces <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />I will present a formula of the S_n-equivariant Euler characteristics of genus one stable maps to the projective space. It enriches the ordinary Euler characteristics, which are previously unkown, and continues the results of Getzler - Pandharipande on genus zero stable maps. The approach connects torus localization, composition structure on the Grothendieck ring of varieties, and graph enumeration techniques via wreath symmetric functions. Joint work with Siddarth Kannan.</div><div class="event_time">16:00 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </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>';