var sms = '<div id="sms_bulletin">  <div id="sms_header">  <div class="do_not_print" id="arrow_left"><a href="?next=-40"><img src="//www2.math.ethz.ch/smsjs/images/arrow_left.png"/></a></div><div class="do_not_print" id="arrow_right"><a href="?next=-38"><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. 5</span>      <span style="float: right; text-align:right; width: 250px;">16.10 - 20.10.2023</span>      <span style="text-align: center; display: block; width: 250px; margin: auto; position: relative;">Autumn Semester 2023</span>    </div>  </div>  <div></div>  <div id="sms_content">    <div class="day">      <div class="day_title">        Monday, October 16      </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://theory.epfl.ch/seminar/">Theory and Combinatorics Seminar</a></div><br /><div class="event_speaker"> Axel Parmentier</div><div class="event_title"> Combinatorial optimization layers in neural networks: Applications to dynamic vehicle routing and theoretical guarantees. <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The 2022 EURO-NeurIPS challenge (1) on dynamic vehicle routing highlighted the difficulties of multistage stochastic optimization problems whose state and decision spaces are discrete and combinatorially large. Multistage stochastic optimization policies do not scale, while reinforcement learning approaches have difficulties with the combinatorial decisions. We suggested using a combinatorial optimization layer in a deep learning pipeline : a deep neural network takes in input the state of the system and returns as output the parameters of a deterministic vehicle routing problem, which we solve with a classic combinatorial optimization heuristic to obtain the decision. It seems to overcome the difficulties above and enabled to win the challenge with a three percent margin. The approach requires a learning algorithm to choose the parameters of the neural network. The results of the challenge startled the winning team and opened a scientific question because the learning algorithm used should not have worked. Indeed, it imitated the anticipative policy, which is known to perform poorly in multi-stage stochastic optimization. In the first part of this talk, we use tools from combinatorial optimization, reinforcement learning, and multi-stage stochastic optimization to reinterpret the learning algorithm, understand why it worked on the problem of the challenge and fails on others, and introduce better learning algorithms for policies based on combinatorial optimization layers. We illustrate the performance of these algorithms on several dynamic routing problems. In particular, we significantly improve the performance of the policy used for the challenge. In the second part of this talk, we outline theoretical questions raised by these methods, and prove some first theoretical guarantees on the quality of the solution they return.(1) <a href="https://euro-neurips-vrp-2022.challenges.ortec.com/">https://euro-neurips-vrp-2022.challenges.ortec.com/</a></div><div class="event_time">11:00 &bull; EPF Lausanne, GA 321</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/mat760">Ergodic theory and dynamical systems seminar</a></div><br /><div class="event_speaker">Christopher Enno Hardy Lutsko (Universität Zürich)</div><div class="event_title">Effective Counting of Sphere Packings <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\'ll present a method, using abstract spectral theory, for counting points in a group orbit. That is, given a discrete group of isometries acting on the (n+1) dimensional upper half-space, our method allows one to count the number of points in an orbit a distance T from an observer. In particular, the method does not rely on an explicit pre-trace formula, and thus can be used in infinite volume. Further, I will present how to extend the method to obtain effective error rates when counting Apollonian (and more generally Kleinian) sphere packings. This is based on joint work with Alex Kontorovich, and joint work with Dubi Kelmer and Alex Kontorovich.</div><div class="event_time">15:00 &bull; UZH Irchel, Winterthurerstrasse 190, Z&uuml;rich, Building Y27, Room H 25</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Tuesday, October 17      </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://algebra.dmi.unibas.ch/seminar.html">Seminar Algebra and Geometry</a></div><br /><div class="event_speaker"> Cinzia Casagrande (University of Torino)</div><div class="event_title">Fano 4-folds with large Picard number <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Let X be a smooth, complex Fano 4-fold, and rho(X) its Picard number. We will discuss the following theorem: if rho(X)>12, then X is a product of del Pezzo surfaces. This implies, in particular, that the maximal Picard number of a Fano 4-fold is 18.After an introduction and a discussion of examples, we will introduce the Lefschetz defect, an integral invariant of X, and see how its properties are related to this theorem. In the second part of the talk we will discuss the strategy of proof of the theorem in one particular case: when X has a rational contraction X-->Y where Y has a dimension 3. A rational contraction is a rational map that factors as a sequence of flips followed by a surjective morphism with connected fibers; we will see an explicit example of such setting.</div><div class="event_time">10:30 &bull; Universität Basel, Spiegelgasse 5, Seminarraum 05.001</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/mat770.1">Oberseminar: Algebraische Geometrie</a></div><br /><div class="event_speaker">Dr. Christian Dahlhausen (Universität Zürich)</div><div class="event_title">Representability of analytic K-theory within a rigid analytic motivic homotopy category <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Algebraic K-theory of smooth schemes (over a regular noetherian base scheme) is representable within Morel-Voevodsky\'s motivic homotopy category, wherein the affine line is contractible. For rigid analytic spaces, Ayoub developed an analogous theory wherein the closed unit ball B^1 is contractible. Within Ayoub\'s category, Morrow\'s continuous K-theory and Kerz-Saito-Tamme\'s analytic K-theory are not representable for two reasons: First, they are not B^1-invariant and, secondly, the mapping objects are not pro-spaces. In this talk, I will sketch the construction of a rigid analytic motivic homotopy category with coefficients in condensed spectra. By design, the rigid affine line is contractible in this category and it is canonically enriched over the category of condensed spectra. I will explain how this yields that -- after passing from pro-spaces to condensed spaces -- continuous K-theory and analytic K-theory shall be representable. Furthermore, we can identify the representing object with the image of the representing object of algebraic K-theory under a canonical analytification functor. In future work, I intend to employ this representability in order to study Adams operations, similarly to Riou\'s work on Adams operations on higher algebraic K-theory. In the long run, this might be useful for studying the problem of lifting algebraic cycles as studied by Bloch-Esnault-Kerz who linked this problem to the Hodge conjecture for abelian varietes.</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://math.ethz.ch/s/daco-seminar">DACO Seminar</a></div><br /><div class="event_speaker"><a class="external" href="https://admcrae.github.io/">Dr. Andrew McRae (EPFL)</a></div><div class="event_title">Benign nonconvexity in overparametrized group synchronization <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />I consider an optimization problem arising in orthogonal group synchronization, in which we want to estimate orthogonal matrices from (potentially noisy) relative measurements. The naïve least-squares estimator over orthogonal matrices requires solving a nonconvex program that, in general, has many spurious local minima. We show that adding a small number of degrees of freedom (specifically, relaxing to optimization over slightly “wider” Stiefel manifold matrices) makes the nonconvexity benign in that every second-order critical point is a global minimum and, in fact, yields an optimal solution to the original unrelaxed problem. In the noiseless measurement case, our results are tight and solve a previous conjecture in synchronization over Stiefel manifolds. The key proof innovation is a new randomized perturbation direction. Joint work with Nicolas Boumal; https://arxiv.org/abs/2307.02941.</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_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"> Frank Kutzschebauch (Bern)</div><div class="event_title">The density property for complex manifolds <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Most complex manifolds have a trivial group of holomorphic symmetries. To the contrary, $C^n$ for $g\\geq 2$ has a huge automorphism group which was studied a lot by Rudin and Rosay in late 1980\'s. Answering a question by Rudin, Andersen and Lempert proved that a certain infinite dimensional subgroup of automorphisms is dense, however meagre, in the holomorphic automorphism group. Their result was improved by Forstneric and Rosay to show that any local phase flow of a time dependent holomorphic vector fieldcan be approximated on a compact by a family of holomorphic automorphisms. This remarkable result led to an enormous number of applications for complex geometry. In 2002, Varolin generalized this to complex manifolds calling it density property and gave first examples of such highly symmetric objects. Kaliman and the speaker developed effective tools for proving the density property, the list of such manifolds is rather long nowadays and is growing steadily. We try to givew an overview of this area of research also called Andersen-Lampert theory. There is a version of volume density property. Natural generalizations of symplectic holomorphic manifolds are awaiting us in the future.</div><div class="event_time">15:15 &bull; Université de Genève, Section de mathématiques, 7-9 rue du Conseil-Général, Room 1-07</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"> Gaofeng Huang (Bern)</div><div class="event_title">Symplectic holomorphic density property for Calogero-Moser spaces <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The n-th rational Calogero-Moser space is the completed phase space of a system of n indistinguishable particles on a complex line, interacting through inverse square potential. By a work of Wilson, its mathematical model is known to be a smooth complex affine variety with a holomorphic symplectic structure obtained from symplectic reduction, and this variety is diffeomorphic to the Hilbert scheme of n points on the affine plane. We consider four completely integrable symplectic holomorphic vector fields on this manifold, then compute new symplectic vector fields by taking linear combination and Lie bracket. It turns out that this process does generate all algebraic fields, thus giving the symplectic holomorphic density property of this Stein manifold. Joint work with Rafael B. Andrist. </div><div class="event_time">16:15 &bull; Université de Genève, Section de mathématiques, 7-9 rue du Conseil-Général, Room 1-07</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/MATHS/?period=14">Computational Mathematics Seminar </a></div><br /><div class="event_speaker"> Mi-Song Dupuy (Sorbonne Université)</div><div class="event_title">Anderson-Pulay Acceleration: Convergence of Adaptive Algorithms and Applications to Quantum Chemistry <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In this talk, a general class of non-gradient algorithms forsolving fixed-point problems, named Anderson-Pulay acceleration, isintroduced. This family brings together the DIIS technique (Pulay, 1980) to accelerate the convergence of self-consistent field procedures in quantum chemistry, as well as the Anderson acceleration (Anderson 1960), and their variations. Such methods aim at accelerating the convergence of fixed-point problems by combining at each step several of thesuccessive approximations to generate the next one. This process of extrapolation is characterized by its depth, i.e. the number of previous approximations stored. While this parameter is decisive in the efficiency of the method, in practice, the depth is fixed without any guarantee of convergence. In this presentation, we consider two mechanisms to vary the depth during the course of the method. A firstway is to let the depth grow until the rejection of all the storedapproximations (except the last one) and restart the method. Another way is to adapt the depth by eliminating some less relevant approximations at each step. In a general framework and under natural assumptions, the local convergence and acceleration of Anderson-Pulay acceleration methods can be proved. These algorithms are tested for the numerical resolution of the Hartree-Fock equations and the DFT Kohn-Sham model.These numerical experiments show a faster convergence and lowercomputational costs compared to the traditional fixed window approach.This is a joint work with Maxime Chupin, Guillaume Legendre and Éric Séré. </div><div class="event_time">16:15 &bull; EPF Lausanne, GA 3 21</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"> Jehanne Dousse (UNIGE)</div><div class="event_title"> Integer partitions and representations of Lie algebras <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br /> A partition of a positive integer n is a non-increasing sequence of positive integers whose sum is n. Partitions are classical objects in combinatorics and number theory, but recently several connections with the representation theory of affine Lie algebras have emerged. Among these, an approach initiated by Primc in the 1990’s and developed by the speaker and Konan in the past few years consists in studying crystal bases to express characters of Lie algebra representations in terms of generalised coloured partitions. We will show how this approach gives new partition identities (theorems stating that two different sets of partitions of n have the same cardinality for all n) and simple character formulas.</div><div class="event_time">17:00 &bull; Université de Neuchâtel, Institut de Mathématiques, B103</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"> Sylvester Eriksson-Bique (University of Jyväskylä)</div><div class="event_title">Embeddings of Spaces, Approximations and Differentiable structures <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />How can one represent a non-smooth space in Euclidean space? How to approximate Sobolev and Lipschitz functions with functions of small energy? How can one differentiate functions in non-smooth spaces? These three questions initially seem rather disjoint. I will try to explain a connection between these three via some theorems, tools and ideas from my and others work. We will see at least two of theseconnections: how embeddings can be constructed via approximations, and how differentiable structures may pre-empt such approximations from existing. We will also see a theorem of how a differentiable structure together with an embedding will enforce some rigidity on the space. I will try to explain these phenomena through examples and with as few definitions as possible.</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, October 18      </div>      <div class="day_content">        <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/OSgeom-top.html">Oberseminar Geometrie</a></div><br /><div class="event_speaker"> Patrick Ghanaat (Uni Fribourg)</div><div class="event_title">Solving Maurer-Cartan equations <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The Maurer-Cartan equations are integrability conditions that a frameon a manifold M must satisfy in order to define a local Lie group struc-ture on M . In this talk we review how, under suitable conditions, almostintegrable frames can be deformed into integrable ones. Topics: Maurer-Cartan equations and Cartan curvature, the comparison problem, van-ishing theorems and semisimple groups, Laplace spectrum and nilpotentgroups, elliptic methods and Min-Oo’s curvature flow.</div><div class="event_time">10:20 &bull; Université de Fribourg, 1.309 PER07</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">Dr. Johannes Schmitt (ETH Zürich)</div><div class="event_title">Log intersection theory: from toric varieties to moduli of curves II</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"> Gurvan Mével (Université de Nantes)</div><div class="event_title">Universal polynomials for coefficients of tropical refined invariant in genus 0 <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In enumerative geometry, some numbers of curves on surfaces are known to behave polynomially when the cogenus is fixed and the linear system varies, whereas it grows more than exponentially fast when the genus is fixed. In the first case, Göttsche\'s conjecture expresses the generating series of these numbers in terms of universal polynomials.Tropical refined invariants are polynomials resulting of a weird way of counting curves, but linked with the previous enumerations. When the genus is fixed, Brugallé and Jaramillo-Puentes proved that some coefficients of these polynomials behave polynomially, bringing back a Göttsche\'s conjecture in a dual and refined setting. In this talk we will investigate the existence of universal polynomials for these coefficients.</div><div class="event_time">14:15 &bull; Université de Genève, salle 6 - 13</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Thursday, October 19      </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"> Javier Fresán (Sorbonne Université)</div><div class="event_title">E-functions and 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_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"> Martin Sombra (Universität de Barcelona)</div><div class="event_title">Equidistribution of small points in projective varieties <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Let X be a projective variety over a number field equipped with a metrized line bundle L&#9135;&#9135;&#9135;. A generic sequence of algebraic points of X is small if their heights with respect to L&#9135;&#9135;&#9135; converge to the smallest possible value, namely the essential minimum of the height function. Yuan\'s equidistribution theorem (2008) describes the asymptotic distribution of the Galois orbits of the points in a small generic sequence, under the assumption that the essential minimum coincides with the normalized height of X. This hypothesis holds in important cases such as dynamical heights on projective varieties, but it fails for most choices of (X,L&#9135;&#9135;&#9135;).In this talk I will present a generalization of this theorem, extending to the general projective setting a result by Burgos, Philippon, Rivera Letelier and the speaker for the toric case. In particular, it applies to the canonical height on a semiabelian variety, and thus permits to recover Kühne\'s equidistribution theorem (2019).Joint work with François Ballaÿ (Caen).</div><div class="event_time">14:15 &bull; Universität Basel, Spiegelgasse 1, SR 00.003</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/annonces/colloque">Colloque de Mathématiques </a></div><br /><div class="event_speaker"> Francisc Brown (University of Oxford)</div><div class="event_title">Graph complexes, homology of the general linear group, and numbers <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 a guided tour of some very distinct, but highly interconnected areas of combinatorics, algebraic geometry and number theory. Graph complexes were introduced by Kontsevich and encode the contraction of edges in a graph. Despite the elementary definition, their homology is surprisingly complicated and mostly unknown.  After surveying recent results in this area, I will turn to the homology of the special linear group, and discuss the classical work of Minkowski on values of the zeta function, Voronoi on quadratic forms, and of Borel on stable cohomology. In the final part of the talk I will try to draw the different strands together, and explain how these topics all share a common underlying pattern. </div><div class="event_time">16:15 &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://www.math.uzh.ch/mat675.1">PDE and Mathematical Physics</a></div><br /><div class="event_speaker">Dr. Lucas Ertzbischoff (Imperial College)</div><div class="event_title">On thick spray equations <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We consider a coupled system between kinetic and fluid equations, describing a cloud of particles immersed within a gas. In the "thick spray" regime, the volume fraction for the particles is not negligible compared to that of the fluid: it raises many difficulties for the study of such system, which seems to present losses of derivatives. In particular, and contrary to some other fluid-kinetic couplings, its mathematical study has almost remained absent. I will review some recent progress on thick spray equations, and show that one can actually build a Cauchy theory in Sobolev regularity (at least for a compressible viscous fluid) when the initial data satisfies a Penrose type stability condition (being in fact necessary and sufficient for well-posedness). This is based on joint works with Aymeric Baradat (CNRS, Université Lyon 1) and Daniel Han-Kwan (CNRS, Nantes Université).</div><div class="event_time">16:15 &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_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"><a class="external" href="https://www.imperial.ac.uk/people/e.neumann">Dr. Eyal Neuman (Imperial College London)</a></div><div class="event_title">Fast and Slow Optimal Trading with Exogenous Information <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br /> We model the interaction between a slow institutional investor and a high-frequency trader as a stochastic multiperiod Stackelberg game. The high-frequency trader exploits price information more frequently and is subject to periodic inventory constraints.  We first derive the optimal strategy of the high-frequency trader given any admissible strategy of the institutional investor. Then, we solve the problem of the institutional investor given the optimal  strategy of the high-frequency trader, in terms of the resolvent of a Fredholm integral equation, thus establishing the unique multi-period Stackelberg equilibrium of the game. Our results provide an explicit solution which shows that the high-frequency trader can adopt either predatory or cooperative strategies in each period, depending on the tradeoff between the order-flow and the trading signal. We also show that the institutional investor\'s strategy is more profitable when the order-flow of the high-frequency trader is taken into account.  This talk is based on a joint work with Rama Cont and Alessandro Micheli. </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, October 20      </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/forschung/mathematik/seminar-in-numerical-analysis">Seminar in Numerical Analysis</a></div><br /><div class="event_speaker"> Marco Zank (U Wien)</div><div class="event_title">Conforming Space-Time Finite Element Methods <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />For the discretization of time-dependent partial differential equations, the standard approaches are explicit or implicit time-stepping schemes together with finite element methods in space. An alternative approach is the usage of space-time methods, where the space-time domain is discretized and the resulting global linear system is solved at once. In this talk, some recent developments in space-time finite element methods are reviewed. For this purpose, the heat equation and the wave equation serve as model problems. First, for both model problems, space-time variational formulations and their unique solvability in space-time Sobolev spaces are discussed, where a modified Hilbert transformation is used such that ansatz and test spaces are equal. Second, conforming discretization schemes, using piecewise polynomial, globally continuous functions, are introduced. Solvability and stability of these numerical schemes are discussed. Next, we investigate efficient direct solvers for the occurring huge linear systems. The developed solvers are based on the Bartels--Stewart method and on the Fast Diagonalization method, which result in solving a sequence of spatial subproblems. The solver based on the Fast Diagonalization method allows solving these spatial subproblems in parallel, leading to a full parallelization in time. In the last part of the talk, numerical examples are shown and discussed.</div><div class="event_time">11:00 &bull; Universität Basel, Spiegelgasse 5, Seminarraum 05.001</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://sites.google.com/view/pm-seminar/home">Physical Mathematics Seminar</a></div><br /><div class="event_speaker"> Veronica Fantini</div><div class="event_title">Quantum modularity from resurgence of the spectral trace of local P2 <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The resurgent structures of the first fermionic spectral trace of local P2 (computed separately by C. Rella and by M. Mariño and J. Gu) are simple yet very rich. In this talk, I will focus on their conjectural relationship with quantum modular forms and possible applications. This is based on a joint project with C. Rella.</div><div class="event_time">14:00 &bull; Université de Genève, Conseil Général 7-9, Room 1-07</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/number-theory-seminar">Number Theory Seminar</a></div><br /><div class="event_speaker">Dr. Brandon Williams (RWTH Aachen)</div><div class="event_title">Computing Fourier coefficients of paramodular eigenforms <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 an ongoing project of computing the Fourier expansions of cuspidal paramodular eigenforms, particularly in low weight. This is joint work with Eran Assaf.</div><div class="event_time">14:15 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://www.epfl.ch/schools/sb/research/math/statistics-seminars/">Statistics Seminar </a></div><br /><div class="event_speaker"> Anne  van Delft (Columbia University)</div><div class="event_title">Title T.B.A.</div><div class="event_time">15:15 &bull; EPF Lausanne, CM 1 100</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">Dr. Alessandro Giacchetto (ETH Zürich)</div><div class="event_title">The geometry of combinatorial moduli spaces <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The Teichmüller space of bordered surfaces can be described via metric ribbon graphs, leading to a natural symplectic structure introduced by Kontsevich in his proof of Witten\'s conjecture. I will show that many tools of hyperbolic geometry can be adapted to this combinatorial setting, and in particular the existence of Fenchel–Nielsen coordinates that are Darboux. As applications of this setup, I will present a combinatorial analogue of Mirzakhani\'s identity, resulting in a completely geometric proof of Virasoro constraints as well as Norbury\'s recursion for the counting of integral points. Time permitting, I will describe how to count simple closed geodesics in this setting, and how its asymptotics compute Masur–Veech volumes of the moduli space of quadratic differentials.</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>';