var sms = '<div id="sms_bulletin">  <div id="sms_header">  <div class="do_not_print" id="arrow_left"><a href="?next=-190"><img src="//www2.math.ethz.ch/smsjs/images/arrow_left.png"/></a></div><div class="do_not_print" id="arrow_right"><a href="?next=-188"><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. 7</span>      <span style="float: right; text-align:right; width: 250px;">3.4 - 7.4.2023</span>      <span style="text-align: center; display: block; width: 250px; margin: auto; position: relative;">Spring Semester 2023</span>    </div>  </div>  <div></div>  <div id="sms_content">    <div class="day">      <div class="day_title">        Monday, April 3      </div>      <div class="day_content">        <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/mat770.1">Oberseminar: Algebraische Geometrie</a></div><br /><div class="event_speaker">Prof. Dr. Christophe Mourougane (Université Rennes 1)</div><div class="event_title">BCOV invariant of Calabi-Yau varieties <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />I will present the construction of the BCOV invariant of Calabi-Yau varieties, inspired by the physicists Bershadsky, Cecotti, Ooguri and Vafa. I will show how this birational invariant of the complex structure enriches, by a spectral data, the data of the variations of Hodge structure and plays, for the counting of genus 1 curves in Calabi-Yau varieties via mirror symmetry, the role of the Yukawa potential for the counting of rational curves. This is a joint work with Dennis Eriksson and Gerard Freixas i Montplet.</div><div class="event_time">13:15 &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://www.math.uzh.ch/mat760">Ergodic theory and dynamical systems seminar</a></div><br /><div class="event_speaker">Dr. Charlene Kalle (Leiden University)</div><div class="event_title">Random intermittent dynamics <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Intermittent dynamics, where systems irregularly alternate between long periods of different types of dynamical behaviour, has been studied since the work of Pomeau and Manneville in 1980. In random dynamical systems this phenomenon has only been well understood in a few specific cases. A random dynamical system consists of a family of deterministic systems, one of which is chosen to be applied at each time step according to some probabilistic rule. In this talk we will describe the intermittency of some families of random systems with a particular emphasis on how the intermittency of the random system depends on the intermittency of the underlying deterministic systems. This talk is based on joint works with Ale Jan Homburg, Tom Kempton, Valentin Matache, Marks Ruziboev, Masato Tsujii, Evgeny Verbitskiy and Benthen Zeegers.</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_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/tggroup/doku.php?id=fables">Séminaire "Fables Géométriques" </a></div><br /><div class="event_speaker"> Alexander Bobenko (TU Berlin)</div><div class="event_title">Discrete conformal mappings, ideal hyperbolic polyhedra, and Ronkin function <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The general idea of discrete differential geometry is to find and investigate discrete models that exhibit properties and structures characteristic for the corresponding smooth geometric objects. We focus on a discrete notion of conformal equivalence of polyhedral metrics. Two triangulated surfaces are considered discretely conformally equivalent if the edge lengths are related by scale factors associated with the vertices. This simple definition leads to a surprisingly rich theory. We review connections between conformal geometry of triangulated surfaces, the geometry of ideal hyperbolic polyhedra and discrete uniformization of Riemann surfaces. Surprisingly, variational description of discrete conformal mappings is given by Ronkin function on amoeba with three ends. Applications in geometry processing and computer graphics will be demonstrated.</div><div class="event_time">15:00 &bull; Université de Genève, Conseil Général 7-9, Room 6-13</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"> Patricia Dietzsch (ETH Zürich)</div><div class="event_title">Lagrangian Hofer metric and barcodes <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Filtered Lagrangian Floer homology gives rise to a barcode associated to a pair of Lagrangians. It is well-known that the lengths of the finite bars and the spectral distance are lower bounds of the Lagrangian Hofer metric. In this talk we will discuss a reverse inequality: We will show an upper bound of the Lagrangian Hofer distance between equators in the cylinder in terms of a weighted sum of the lengths of the finite bars and the spectral distance.</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_fr"><a class="external" href="https://www.unifr.ch">Université de Fribourg</a></div><div class="event_type"><a class="external" href="https://commonweb.unifr.ch/_Science/Math/Pub/Math/seminars/OSTopologie/OSTopologie.html">Oberseminar Topologie </a></div><br /><div class="event_speaker"> Luke Higgins (Durham University)</div><div class="event_title">Classifying Noncompact Surfaces <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The classification of compact surfaces is a standard result which is presented in almost all first courses in topology; less common is the classification of noncompact surfaces. This talk will cover some properties of noncompact surfaces, before developing the invariants which classify them. In addition to invariants familiar from the compact classification theorem, we must include the space of ends, and some of its notable subspaces, of the surface. Earlier considerations will also justify additional invariants regarding the boundary components of the surface.</div><div class="event_time">17:00 &bull; Université de Fribourg, 0.05 PER23</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Tuesday, April 4      </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"> Karoly Böröczky (Alfréd Rényi Institute of Mathematics)</div><div class="event_title">The Isoperimetric inequality, the Brunn-Minkowski theory, and the Lp Minkowski problem</div><div class="event_time">10:15 &bull; Zoom</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.unine.ch/math/home/colloques_et_seminaires/seminaires-de-linstitut.html">Séminaire Groupes et Géométrie </a></div><br /><div class="event_speaker"> Letizia Issini (Université de Genève)</div><div class="event_title">Divergence of wreath products and Houghton groups <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Divergence of finitely generated groups is a quasi-isometry invariant that describes how difficult it is to connect two points in a Cayley graph of a group, avoiding a certain ball around the identity. It was defined by Gersten in 1994, when he gave the first example of a CAT(0)-group whose divergence is neither linear nor exponential. In this talk I will present the definition of divergence, mention some results about it, and focus on divergence of wreath products and Houghton groups.</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_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"> Elena Vigna (University of Turin)</div><div class="event_title">Tail optimality and preferences consistency for intertemporal optimization problems <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Given an intertemporal optimization problem over a time interval $[t_0,T]$ and a control plan associated to it, we introduce the four notions of local and global tail optimality of the control plan, and local and global preferences consistency of the agent. While the notion of tail optimality of a control plan is not new, the main innovation of this paper is the definition of preferences consistency of an agent, that is a novel concept.<br>We prove that, in the case of a \\emph{linear} time-consistent problem where dynamic programming can be applied, the optimal control plan is globally tail-optimal and the agent is globally preferences-consistent. Opposite, in the case of a \\emph{non-linear} problem that gives rise to time inconsistency, we find that global tail optimality and global preferences consistency do not coexist. We analyze three common ways to attack a time-inconsistent problem: (i) precommitment approach,  (ii) dynamically optimal approach, (iii) consistent planning approach. We find that none of the three approaches keeps simultaneously the desirable properties of global tail optimality and global preferences consistency: the existing approaches to time inconsistency are flawed in various ways. We also prove that if the performance criterion includes a convex function of expected final wealth and a globally tail-optimal plan exists, then the three approaches coincide and the problem is linear.<br>The contribution of the paper is to disentangle the notion of time consistency into the two notions of tail optimality and preferences consistency. The analysis should shed light on the price to be paid in terms of tail optimality and preferences consistency with each of the three approaches currently available for time inconsistency.</div><div class="event_time">11:00 &bull; EPF Lausanne, UniL campus, 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"> Julien Levallois (Science Innovation Hub, Université de Genève)</div><div class="event_title">L’Innovation et l’Entrepreneuriat à l’Université  <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />L’Entrepreneuriat est-il compatible avec une activité de recherche ou lorsque l’on est étudiant-e en Mathématiques ? Vous avez éventuellement une idée (commerciale) innovante et vous aimeriez créer votre propre entreprise ?<br>Ce séminaire vise à encourager et à renforcer la culture de l’innovation, l’esprit d’entreprise et le développement de nouvelles idées auprès des étudiant-es et des chercheur-euses. Nous aborderons en particulier les différentes étapes du développement d’un projet entrepreneurial et verrons qu’il s’agit d’un processus quasi-scientifique et qui peut s’apprendre. Le plus important étant qu’il constitue une véritable opportunité de carrière et de transfert de savoir.</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://www.epfl.ch/labs/stoan/probability-stochastic-analysis-seminar/">Probability (and Stochastic Analysis) Seminar </a></div><br /><div class="event_speaker"> Nicolas Perkowski (Freie Universität Berlin)</div><div class="event_title">Title T.B.A.</div><div class="event_time">15:00 &bull; EPF Lausanne, Salle CM 0 11</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. Matteo  Bonforte (Universidad Autonoma Madrid)</div><div class="event_title">Nonlinear and Nonlocal Diffusions. Smoothing effects, Green functions and functional inequalities <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We will consider the Cauchy problem for Nonlinear Diffusion equations of porous medium type $u_t=-\\mathcal{L} u^m$, with $m>1$ and investigate whether or not integrable data produce bounded solutions. The diffusion operator belongs to a quite general class of nonlocal operators, and we will see how different assumption on the operator imply (or not) smoothing properties. We will briefly compare the approach based on Moser iteration and the approach through Green functions. On the one hand, we show that if the linear case ($m=1$) enjoys smoothing properties, also the nonlinear will do. On the other hand, we see that in some cases the nonlinear diffusion enjoys the smoothing properties also when the linear counterpart does not, thanks to the convex nonlinearity. Following Nash\' ideas, we see how smoothing properties are often equivalent to the validity of Gagliardo-Nirenberg-Sobolev (and Nash) inequalities: we explore these implications also in the nonlinear and nonlocal context and the connection with dual inequalities (Hardy-Littlewood-Sobolev) and Green function estimates.  This is a work with J. Endal (NTNU, Trondheim). Finally, I shall present smoothing and higher regularity estimates for a class of zero-order p-Laplacian evolution equations, showing another case in which the regularization is true in the nonlinear setting while it fails for the linear counterpart. This is a work in progress with A. Salort (Univ. Buenos Aires).</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://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://stat.ethz.ch/events/research_seminar">Research Seminar in Statistics</a></div><br /><div class="event_speaker"> Boaz Nadler (The Weizmann Institute of Science, Israel)</div><div class="event_title">Spectral Methods for Reconstructing Trees <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Tree graphical models are common statistical models for data in a wide variety of applications. Tree models are particularly popular in phylogenetics, where an important task is to infer the evolutionary history of current species. Given observations at the leaves of the tree, a common problem is to reconstruct the tree\'s latent structure. We present two simple spectral-based methods for tree recovery: <br>(i) A bottom up spectral neighbor joining method (SNJ); and <br>(ii) STDR - a spectral based top down method. <br>We prove that under suitable assumptions, both methods are consistent and derive finite sample recovery guarantees. We illustrate the competitive performance of our algorithms in comparison with popular tree recovery methods.</div><div class="event_time">15:15 &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_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"> Andrey Krutov (University of Prague)</div><div class="event_title">Noncommutative differential geometry of the quantum Grassmannians <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Noncommutative geometry is, in general, more tractable on quantum homogeneous spaces than on quantum groups themselves. Some of the best-behaved examples are the irreducible quantum flag manifolds. We  will review recent results about noncommutative (complex) differential geometry of the irreducible quantum flag manifolds. The main example here will be the quantum Grassmannians. In particular, in the talk we will discuss noncommutative generalization of the following notions from the classical complex differential geometry: complex structures, holomorphic homogeneous line bundles, Hodge structures, Fano structures, and Schubert calculus.</div><div class="event_time">15:15 &bull; Université de Genève, Conseil Général 7-9, Room 1-07</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ne"><a class="external" href="https://unine.ch">Université de Neuchâtel</a></div><div class="event_type"><a class="external" href="http://www.unine.ch/math/home/colloques_et_seminaires/les-colloques-du-mardi.html">Colloque du Mardi </a></div><br /><div class="event_speaker"> Laura Ciobanu (Heriot-Watt University, Edinburgh)</div><div class="event_title">Equations in groups: between decidability and undecidability <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />For a group or semigroup or ring G, solving equations where the coefficients are elements in G and the solutions take values in G can be seen as akin to solving systems of linear equations in linear algebra, Diophantine equations in number theory, or more generally, polynomial systems in algebraic geometry.<br>In this talk I will give a survey about solving equations in infinite groups, with emphasis on the free ones, and show how imposing certain constraints on the solutions can tilt the balance between decidability and undecidability.</div><div class="event_time">16:00 &bull; Université de Neuchâtel, Rue Emile Argand 11, Auditoire B013</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">Mireille Soergel (ETHZ)</div><div class="event_title">What is... the Davis Complex? <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The study of abstract reflection groups is due to Tits, who defines Coxeter systems (W,S) through their presentation. There are many different combinatorial and geometric objects associated to such Coxeter systems (W,S). One of them is the Davis complex. The goal of this talk is to introduce abstract Coxeter groups and describe their associated Davis complex.</div><div class="event_time">16:15 &bull; UZH Zentrum, Building KO2, Room F 150</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Wednesday, April 5      </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"> Shahar Mendelson (The Australian National University)</div><div class="event_title">Probabilistic methods in Analysis</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_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"> Pascal Oswald (Johannes Gutenberg Universität Mainz)</div><div class="event_title">Of Mice and Men <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Within Europe there are two genetically distinct subspecies of the house mouse;the Mus musculus musculus (eastern European house mouse) and the Mus musculusdomesticus (western European house mouse). The geographical region of meetingand interbreeding of these two subspecies is known as a hybrid zone. Assumingthat the underlying genetics is controlled by a single gene which occurs in twotypes (alleles) a and A and using that the reproductive fitness of homozygotic (i.e.aa,AA) individuals is grater than that of heterozygotic (i.e. aA) individuals onecan show that in an infinitely dense population and viewed over large spatial andtemporal scales, the proportion of a-alleles in the population at location x and timet is modelled by solutions of the Allen-Cahn equation. In this talk I will discussprobabilistic interpretations of solutions to certain semi-linear parabolic equations(such as the Allen-Cahn equation) by means of a duality to voting schemes on thegenealogy of branching Brownian motion.</div><div class="event_time">12:15 &bull; Universität Basel, Spiegelgasse 5, SR 05.002</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">Prof. Dr. Renzo Cavalieri (Colorado State University)</div><div class="event_title">Tropical contributions to enumerative geometry of target dimension 1, Part III <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />This cycle of talks wants to highlight how ideas from tropical geometry have contributed not only to the solution, but also to the development of enumerative geometric problems regarding moduli spaces of curves, and maps from curves to curves. We will spend a little of time reviewing the origins of this story, i.e. the development of tropical Hurwitz numbers as combinatorial analogues for the classical Hurwitz numbers. We will discuss a more recent interpretation that views tropical Hurwitz numbers as the natural computation for the intersection number of the double ramification cycle with an element of the log Chow ring of the moduli space of curves (called in this case the branch polynomial, as it is presented as a piecewise polynomial function on the moduli spaces of tropical curves) which is determined by the tropical moduli space of covers of the projective line. We will see that from the tropical perspective analogous piecewise polynomial functions may be associated to $k$-DR cycles (cycles arising from spaces of twisted pluri-differentials), thus giving rise to $k$-analogues of Hurwitz numbers (called leaky Hurwitz numbers) that enjoy many of the algebro-combinatorial properties of Hurwitz numbers - such as piecewise polynomiality and wall crossings.We will present some work in progress which intends to incorporate descendants into these pictures. Tropical algorithms are developed that give rise to some intruiguingly simple formulas in the case when one point is fully ramified. The material presented is based on many years of joint work with several people, including Paul Johnson, Hannah Markwig, Dhruv Ranganathan and Johannes Schmitt.</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_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">Prof. Dr. Michele Wigger (Telecom Paris, LTCI)</div><div class="event_title">Lectures on Information Theory - Part 5 <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Shannon\'s capacity theorem &lt;BR> &lt;BR> (**This eSeminar will take place over Zoom, using the same meeting details as previous seminars. If you do not have meeting details, please contact zita.fiquelideabreu@math.uzh.ch **)</div><div class="event_time">15:15 &bull; UZH Irchel, Winterthurerstrasse 190, Z&uuml;rich, Building Y27, Room H 25</div>        </div>        <div class="day_content_item important"><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"> Miguel Moreira (ETH Zürich)</div><div class="event_title">The cohomology ring is not &#967;-invariant <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />This talk will be about the moduli space M_{d, &#967;} of stable 1-dimensional sheaves on the projective plane. The cohomology of these moduli spaces is conjecturally related to the enumerative geometry of local P^2. This relation predicts in particular that the (intersection) Betti numbers of M_{d, &#967;} do not depend on &#967;, which has been proven by Maulik-Shen. A natural question is whether the cohomology ring is also &#967;-invariant. In this talk I will answer that question negatively: except for possibly finitely many exceptional cases, the ring cohomology determines &#967; up to some trivial symmetries. In particular this shows that those spaces are typically not homeomorphic (previously they were only known to be non-isomorphic as algebraic varieties). This is based on joint work with W. Lim and W. Pi. </div><div class="event_time">15:30 &bull; ETH Zentrum, Building ITS, Room  </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"> Henry Bradford (University of Cambridge)</div><div class="event_title"> Identities with constants for finite groups <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />An identity, or law, for a group G is a nontrivial equation in one or more variables, which is always satisfied when the variables are evaluated in G. Every finite group satisfies a law, and it is natural to ask for the length of the shortest law for G, and to investigate how this length reflects the structure of G. These questions are explored in several papers in the literature. In ongoing joint work with Jakob Schneider and Andreas Thom, we investigate how the answers to these questions may change (or not) when our equations are allowed to contain constants in G as well as variables.</div><div class="event_time">15:45 &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/aa/?events">Neuchatel - St.Gallen - Zurich Seminar in Coding Theory and Cryptography</a></div><br /><div class="event_speaker">Prof. Dr. Michele Wigger (Telecom Paris, LTCI)</div><div class="event_title">Lectures on Information Theory - Part 6 <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Secrecy capacity and undetectable communication &lt;BR> &lt;BR> (**This eSeminar will take place over Zoom, using the same meeting details as previous seminars. If you do not have meeting details, please contact zita.fiquelideabreu@math.uzh.ch **)</div><div class="event_time">16:15 &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://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">Prof. Dr. Bastien Mallein (Université Sorbonne Paris Nord)</div><div class="event_title">Extremal process of multidimensional branching Brownian motion <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The branching Brownian motion is a particle system in which each particle evolves independently of one another. Each particle moves according to a Brownian motion in dimension d, and splits into two daughter particles after an independent exponential time of parameter 1. The daughter particles then start from their positions independent copies of the same process.We take interest in the long time asymptotic behaviour of the particles reaching farthest away from the origin. We show that these particles can be found at a distance of order $\\sqrt{2} t + \\frac{d-4}{2\\sqrt{2}} \\log t$ from the origin of the process, and that they can be grouped into a Poisson point process of families of close relatives, spreading in directions sampled according to the random measure $Z(\\mathrm{d} \\theta)$ that plays the role of an analogue of the derivative martingale of the branching Brownian motion.</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 6      </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"> Brita Nucinkis (Royal Holloway, University of London)</div><div class="event_title">Cohomological methods in group theory</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_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"> Pierre Descombes (Université Paris Jussieu)</div><div class="event_title">Toric localization for cohomological DT invariants <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 first review the construction of cohomological DT invariants, a kind of virtual cohomology for moduli spaces of sheaves on Calabi-Yau threefolds. We will explain their construction by Brav, Bussi, Dupont, Joyce, and Szendroï, using perverse sheaves of vanishing cycles. We will then present a toric localization formula for these invariants, which can be seen as a virtual version of the Bialinicky-Birula decomposition. The proof of this formula uses in a crucial way the formalism of hyperbolic localization and its interaction with perverse sheaves.</div><div class="event_time">13:15 &bull; EPF Lausanne, Salle MA A3 30</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/events/">Seminar in Mathematics </a></div><br /><div class="event_speaker"> Gabrielle De Micheli (University of California, San Diego)</div><div class="event_title">Hard mathematical problems used in Cryptography <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The security of public key cryptography relies on hardness assumptions coming from a variety of mathematical problems. One of the two main candidates originally considered to construct public-key cryptosystems is modular exponentiation with its hard inverse operation, computing discrete logarithms. More recently, with the emergence of new technologies such as quantum computers, cryptographers have focused on new hard problems coming from different mathematical objects, euclidean lattices for example. The main goal of my research is to evaluate the hardness of such mathematical problems in order to correctly assess the security of cryptographic schemes widely deployed and used in the real world.<br>More precisely, I have focused on the complexity of algorithms solving the discrete logarithm problem and the use of RingLWE (Learning With Errors) to construct fully homomorphic encryption schemes. I will cover results from both these directions during this talk.</div><div class="event_time">13:30 &bull; EPF Lausanne, Salle MA B1 524 </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"> Tommaso Botta (ETH Zurich)</div><div class="event_title">Bow varieties, stable envelopes and 3d-mirror symmetry <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Mirror symmetry for 3d N=4 supersymmetric gauge theories has recently received much attention in geometry and representation theory. Theories within this class admit very interesting moduli spaces of vacua, whose most relevant components are called Higgs and Coulomb branches. The study of the mathematics of the Higgs branch was initiated by Nakajima in the 90s, and since then its geometry has proved to be intimately related to the representation theory of Kac-Moody Lie algebras and quantum groups. Only recently, mathematically accurate definitions of the Coulomb branch have been proposed, and their study has started.The main mathematical prediction of 3d mirror symmetry is that the Higgs and Coulomb branches of a pair of dual theories are interchanged. Hence, both pairs of homologous branches (Higgs-Higgs and Coulomb-Coulomb) are expected to share exceptional topological and geometric properties. One of the main predictions of mirror symmetry is that the elliptic stable envelopes, which are certain topological classes intimately related to elliptic quantum groups, are the same after appropriate identifications. In this talk, I will focus on Coulomb and Higgs branches of type A, which are collectively described by a class of varieties known as Cherkis bow varieties, and I will discuss the main ideas behind the proof of mirror symmetry of sable envelopes (joint work in preparation with Richard Rimanyi).</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_ba"><a class="external" href="https://unibas.ch">Universität Basel</a></div><div class="event_type"><a class="external" href="https://www.ntwebseminar.org/">Number Theory Web Seminar</a></div><br /><div class="event_speaker"> Kannan Soundararajan (Stanford University)</div><div class="event_title"><a class="external" href="https://www.ntwebseminar.org/">Covering integers using quadratic forms</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />How large must $\\Delta$ be so that we can cover a substantial proportion of the integers below $X$ using the binary quadratic forms $x^2 +dy^2$ with $d$ below $\\Delta$?  Problems involving representations by binary quadratic forms have a long history, going back to Fermat.  The particular problem mentioned here was recently considered by Hanson and Vaughan, and Y. Diao.  In ongoing work with Ben Green, we resolve this problem, and identify a sharp phase transition:  If $\\Delta$ is below $(\\log X)^{\\log 2-\\epsilon}$ then zero percent of the integers below $X$ are represented, whereas if $\\Delta$ is above $(\\log X)^{\\log 2 +\\epsilon}$ then 100 percent of the integers below $X$ are represented.  </div><div class="event_time">17:00 &bull; Universität Basel, online Seminar</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. Tobias Fissler (ETH Z&uuml;rich, Switzerland)</div><div class="event_title">Generalised Covariances and Correlations <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Pearson covariance of two random variables $X$ and $Y$ measures the average joint comovements around the respective means of $X$ and $Y$. We generalise this well known measure by replacing the means with other summary statistics of the marginal distributions of $X$ and $Y$ such as quantiles, expectiles, or absolute thresholds. Deviations from these quantities are defined via generalised errors, induced by identification or moment functions. As a normalised measure of dependence, a generalised correlation, is constructed. Replacing the common Cauchy--Schwartz normalisation by a novel Fréchet--Hoeffding normalisation, we obtain attainability of the entire interval $[-1,1]$ by the generalised correlation for any given marginals. After uncovering favourable properties of these new dependence measures and establishing consistent estimators, we construct function-valued distributional correlations, exhibiting the entire dependence structure. They give rise to tail correlations, which should arguably supersede the coefficients of tail dependence. The two quantities coincide for positive tail dependence, but the novel notion may distinguish between negative dependence and asymptotic independence. Finally, we construct summary covariances (correlations), which arise as (normalised) weighted averages of distributional covariances. We retrieve Pearson covariance and Spearman correlation as special cases. The talk is based on joint work with Marc-Oliver Pohle.</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 7      </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>';