var sms = '<div id="sms_bulletin">  <div id="sms_header">  <div class="do_not_print" id="arrow_left"><a href="?next=-31"><img src="//www2.math.ethz.ch/smsjs/images/arrow_left.png"/></a></div><div class="do_not_print" id="arrow_right"><a href="?next=-29"><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. 14</span>      <span style="float: right; text-align:right; width: 250px;">18.12 - 22.12.2023</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, December 18      </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"> Jim Zhao (University of Basel)</div><div class="event_title"><a class="external" href="https://dmi.unibas.ch/de/studium/mathematik/doktorat/bernoullis-tafelrunde/detail/bernoullis-tafelrunde-jim-zhao-university-of-basel/">Cubic Regularized Subspace Newton for Non-convex Optimization</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />&lt;p><a href="https://dmi.unibas.ch/fileadmin/user_upload/dmi/Studium/Mathematik/Bernoullis_Tafelrunde/_HS23/Jim_Zhao.pdf" target="_blank">abstract</a>&lt;/p></div><div class="event_time">12:15 &bull; Universität Basel, Seminarraum 05.002</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"> Konstantin Walter Wernli (University of Southern Denmark)</div><div class="event_title">Towards geometric functorial field theories via perturbative quantization   <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />https://www.math.uzh.ch/mat074</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://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">Dr. Nicolas de Saxcé (University Paris-Nord)</div><div class="event_title">Lattices, subspaces and diophantine approximation <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Since the work of Minkowski in the early twentieth century, the space of lattices has been a fundamental tool in the study of natural or rational numbers. Then, Margulis and his followers, in particular Dani, showed that methods from ergodic theory could be used very efficiently in that setting. More recently, Schmidt and Summerer started the "parametric geometry of numbers", which is a way to describe diagonal orbits in the space of lattices, using a simple combinatorial coding. The goal of this mini-course is to introduce the main concepts of parametric geometry of numbers, and to use them to study two problems going back to Jarník and Schmidt: - (Jarník) Given r>(n+1)/n, does there exist x in R^n such that the inequality |x-p/q| &lt; q^(-r) has infinitely many solutions p/q in Q^n, but for all c&lt;1, the inequality |x-p/q| &lt; c q^(-r) has only finitely many solutions p/q in Q^n? (And what is the Hausdorff dimension of the set of such points?) - (Schmidt) Given an l-dimensional subspace x in R^d, for what values of r can one always find an l-dimensional rational subspace v in Q^d arbitrarily close to x and such that the distance to x satisfies d(v,x) &lt; H(v)^(-r)? (Height and distance on Grassmann varieties will be defined in the first lecture -- note that this talk will last 1h30 and it will be introductory lecture for the ensuing mini-course that will take place on Tuesday 19th and Wednesday 20th of December. Please contact organizers for more info.)</div><div class="event_time">15:00 &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_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">Dr. Livio Liechti (Universität Fribourg)</div><div class="event_title"><a class="external" href="https://www.math.unibe.ch/research/talks/colloquium/index_eng.html">Optimal multicurve intersection degrees</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />A multicurve on a surface is a disjoint union of finitely many simple closed curves. We consider intersection matrices built from pairs of multicurves that fill a closed orientable surface of genus~$g\\ge 2$. These matrices have integer coefficients and their spectral radii are algebraic integers. In the eighties, Thurston claimed that spectral radii with algebraic degrees up to~$3g-3$ could be realised in this way. While it is well-known that the degree of such a spectral radius is bounded from above by~$3g-3$, actually realising these degrees remains an open problem to which we present a partial solution. Precisely, we exhibit the first known infinite sequence of closed orientable surfaces for which spectral radii of degree~$3g-3$ can indeed be realised. This is joint work with Erwan Lanneau. </div><div class="event_time">17:15 &bull; Universität Bern, Sidlerstrasse 5, 3012 Bern, Lecture Room B6</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Tuesday, December 19      </div>      <div class="day_content">        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/annonces/groupes-geometrie">Groupes et Géométrie </a></div><br /><div class="event_speaker"> Caterina Campagnolo (Universitad Autónoma de Madrid)</div><div class="event_title">Un nouveau critère d\'annulation pour la cohomologie bornée <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />La définition de la cohomologie bornée des groupes remonte à Johnson et Gromov. C\'est un invariant puissant, mais qui demeure difficile à calculer audelàdes groupes moyennables.Dans un travail en commun avec Francesco Fournier-Facio, Yash Lodha et Marco Moraschini, nous présentons une nouvelle condition algébrique qui implique l\'annulation de la cohomologie bornée d\'un groupe pour une grande classe de coefficients. Cette condition est satisfaite par de nombreux groupes non-moyennables d\'origine topologique et dynamique.</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_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"> Joackim Bernier (Université de Nantes)</div><div class="event_title">Numerical integration of the nonlinear Klein-Gordon equations at low regularity and conservation properties <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Close to the origin, the nonlinear Klein--Gordon equations on the circle are nearly integrable Hamiltonian systems which have infinitely many almost conserved quantities called "harmonic energies" or "super-actions". In a series of works in 2008,  D. Cohen, E. Hairer and C. Lubich proved that, at high regularity, classical symplectic numerical integrators preserve this qualitative property (even if the CFL number is not small).  I will present a joint work with C. Abou Khalil (in progress), in which we extend this result for non-smooth solutions.</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/schools/sb/research/math/statistics-seminars/">Statistics Seminar </a></div><br /><div class="event_speaker"> Sagnik Nandy (UPenn)</div><div class="event_title">Orchestrated Approximate Message Passing: A New Way of Information Integration from Multimodal Data <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Integrating information from multiple correlated datasets is a crucial aspect of modern data science. Despite the existence of numerous methods for this purpose, their statistical properties remain unclear, making valid statistical inference challenging. In this talk, I shall introduce Orchestrated Approximate Message Passing for integrating information across multiple correlated datasets. This method is both computationally efficient and statistically optimal under certain stylized models. Subsequently, I shall show how to apply this technique to tackle two distinct problems, namely community detection in a balanced, two-community, contextual stochastic block model and compressed sensing in the presence of network-side information.</div><div class="event_time">14:15 &bull; EPF Lausanne, GA 3 21</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. Richard  Sowers (University of Illinois Urbana-Champaign)</div><div class="event_title">Lateral boundary conditions for a Kolmogorov-type PDE <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We consider a hypoelliptic Kolmogorov-type PDE corresponding to a particle under white noise force. We are interested in imposing Dirichlet conditions at a side boundary. We construct a simple Gaussian heat kernel inside the domain, and investigate a boundary-layer kernel. We show that this boundary layer heat kernel has a novel jump condition. We outline a polynomial expansion of the heat kernels, and then construct a Volterra equation.This Volterra equation has a periodic structure resulting from the novel jump condition.</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_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://www.epfl.ch/labs/mathicse/">Computational Science and Engineering </a></div><br /><div class="event_speaker"> Allan Peter  Engsig-Karup (DTU)</div><div class="event_title">High-Order Numerical Methods for Nonlinear Free Surface Wavesand Wave-Structure Interaction for Engineering Applications <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Advances in numerical simulation and modelling fidelity of water waves go in hand with continued improvements in computational resources, improving the efficiency ofnumerical algorithms and the adoption of modern and emerging many-core hardware for massively parallel computations. We discuss trends in scientific computing and link these to recent research in addressing scientific gaps to be able to address nonlinear wave and wave-structure interaction problems through designing new high-order numerical schemes for both nonlinear and dispersive wave propagation and nonlinear wave-structure interaction based on potential flow theory and more recently also Navier-Stokes modelling. Through simple benchmarks of increasing complexities ourresearch targetimprovements in numerical efficiencythrough accelerated iterative solver strategies based on defect corrections / multigrid preconditioning, simulation at large spatial scales in practical times and with ability to handlethe geometric complexities ofoffshore structures and marine environments in simulations. Highlights are given from our research spanning nearly adecade with scopes towards engineering applications of high relevance for renewablesapplications.Historically, and perhaps surprisingly, spectral element methods appear to have been somewhat ‘overlooked’ in world-wide research for marine hydrodynamics applications. We therefore given an overview of key scientific developments and benchmarks, and discuss some of the pros and cons, as well as the recent years progress on advancing theuse of high-order numerical schemes such as spectral element methods for free surface flows.</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_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/zurich-colloquium-in-mathematics">Zurich Colloquium in Mathematics</a></div><br /><div class="event_speaker">Prof. Dr. Ivan Smith (University of Cambridge)</div><div class="event_title">New directions in floer theory</div><div class="event_time">16:30 &bull; ETH Zentrum, Building KO, 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"> Frank Kutzschebauch (Uni Bern)</div><div class="event_title">Factorization of Holomorphic Matrices <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Every complex symplectic matrix in Sp2npCq can be factorized as aproduct of the following types of unipotent matrices (in interchangingorder).‚ (i): ˆI B0 I&#729;, upper triangular with symmetric B “ BT.‚ (ii): ˆI 0C I&#729;, lower triangular with symmetric C “ CT.The optimal number TpCq of such factors that any matrix in Sp2npCqcan be factored into a product of T factors has recently been establishedto be 5 by Jin, P. Lin, Z. and Xiao, B.If the matrices depend continuously or holomorphically on a parameter, equivalently their entries are continuous functions on a topologicalspace or holomorphic functions on a Stein space X, it is by no meansclear that such a factorization by continuous/holomorphic unipotentmatrices exists. A necessary condition for the existence is the mapX Ñ Sp2npCq to be null-homotopic. This problem of existence of afactorization is known as the symplectic Vaserstein problem or GromovVaserstein problem. In this talk we report on the results of the speakerand his collaborators B. Ivarsson, E. Low and of his Ph.D. student J.Schott on the complete solution of this problem, establishing uniformbounds Tpd, nq for the number of factors depending on the dimensionof the space d and the size n of the matrices. It seems difficult to establish the optimal bounds. However we obtain results for the numbersTp1, nq, Tp2, nq for all sizes of matrices in joint work with our Ph.D.students G. Huang and J. Schott. Finally we give an application tothe problem of writing holomorphic symplectic matrices as product of exponentials.</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, December 20      </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"> Luke Higgins (Uni Fribourg)</div><div class="event_title">Exotic smooth structures on the 7-sphere <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Given two smooth manifolds which are homeomorphic to one another, is it possible to prove they also must be diffeomorphic - thereby strengthening the quality of this equivalence? In a paper from 1956, Milnor presents a family of counterexamples; thus, a manifold which admits at least one smooth structure may admit many. In particular, Milnor constructs a family of 7-manifolds which are topologically equivalent to the 7-sphere but which carry smooth structures distinct from that of the standard smooth $S^7$.We show how Milnor constructed these first examples of (so-called) exotic spheres, and how Eels & Kuiper later developed an invariant which may be used to classify the exotic 7-spheres, up to diffeomorphism. To end, an overview of Grove & Ziller\'s proof that Milnor\'s exotic spheres admit nonnegative sectional curvature is given.</div><div class="event_time">10:20 &bull; Université de Fribourg, 0.05 PER23</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://www.epfl.ch/labs/mathicse/">Computational Science and Engineering </a></div><br /><div class="event_speaker"> Diane Guignard</div><div class="event_title">Finite Element Methods for the Stretching and Bending of Thin Structures with Folding <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In [Bonito et al., J. Comput. Phys. (2022)], a local discontinous Galerkin method was proposed for approximating the large bending of prestrained plates, and in [Bonito et al., IMA J. Numer. Anal. (2023)] the numerical properties of this method were explored. These works considered deformations driven predominantly by bending. Thus, a bending energy with a metric constraint was considered. We extend these results to the case of an energy with both a bending component and a nonconvex stretching component, and we also consider folding across a crease. The proposed discretization of this energy features a continuous finite element space, as well as a discrete Hessian operator. We establish the &#915;-convergence of the discrete to the continuous energy and also present an energy-decreasing gradient flow for finding critical points of the discrete energy. Finally, we provide numerical simulations illustrating the convergence of minimizers and the capabilities of the model.</div><div class="event_time">16:00 &bull; EPF Lausanne, MA A1 12</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"> Richard Sowers (Illinois)</div><div class="event_title">Side boundary conditions for a Kolmogorov Diffusion <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We consider a Kolmogorov-type PDE corresponding to a particle under white noise force.  We are interested in stopping the process at a fixed position, i.e., imposing Dirichlet conditions at a side boundary.  We construct a simple Gaussian heat kernel inside the domain, and investigate a boundary-layer kernel, connected to some work by McKean.  We show that this boundary layer heat kernel has a novel jump condition.  We outline a polynomial expansion of for the heat kernels, and then construct a Volterra equation for solving the original problem.  The novel jump leads to a periodic structure of the Volterra equationThe seminar will be typically in two parts, separated by a tea break. The first part of is 30 minutes.</div><div class="event_time">16:00 &bull; EPF Lausanne</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Thursday, December 21      </div>      <div class="day_content">        <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="https://www.unine.ch/math/home/colloques_et_seminaires/seminaires-de-linstitut.html">Séminaire de Géométrie et Systèmes dynamiques </a></div><br /><div class="event_speaker"> Lucas Dahinden (Universität Bochum)</div><div class="event_title">C0-stability of topological entropy for Reeb flows in dimension 3 <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Topological entropy is a numerical measure of how chaotic a map is. We are interested in how topological entropy depends on the  map, especially how stable it is   under perturbation. For example for diffeomorphisms homotopic to the identity on three  dimensional manifolds it is well known that topological entropy can  collapse to 0 after smooth perturbations, so it can be very  unstable.We have managed to prove that for  Reeb flows on three dimensional co-oriented compact contact  manifolds topological entropy is surprisingly stable: a generic Reeb flow (with respect to C^\\infty-topology) is a point of  lower semi-continuity (with respect to C^0-topology) of  the topological entropy. The tool that allows us to conclude this is a mechanism discovered byMatthias Meiwes, by which one can approximate topological entropy usinglinks of Reeb chords extracted from a horseshoe. In our work we showstability of these links under perturbation.This is joint work with Marcelo Alves, Matthias Meiwes and AbrorPirnapasov.</div><div class="event_time">14:00 &bull; Université de Neuchâtel, Rue Emile-Argand 11, Room B217</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Friday, December 22      </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>';