var sms = '<div id="sms_bulletin">  <div id="sms_header">  <div class="do_not_print" id="arrow_left"><a href="?next=-13"><img src="//www2.math.ethz.ch/smsjs/images/arrow_left.png"/></a></div><div class="do_not_print" id="arrow_right"><a href="?next=-11"><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. 12</span>      <span style="float: right; text-align:right; width: 250px;">4.5 - 8.5.2026</span>      <span style="text-align: center; display: block; width: 250px; margin: auto; position: relative;">Spring Semester 2026</span>    </div>  </div>  <div></div>  <div id="sms_content">    <div class="day">      <div class="day_title">        Monday, May 4      </div>      <div class="day_content">        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://www.epfl.ch/labs/mathicse/">Computational Science and Engineering </a></div><br /><div class="event_speaker"> Andrew  McRae</div><div class="event_title">Low-rank matrix optimization landscapes with overparametrization <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />I will discuss the global nonconvex landscape of low-rank matrix optimization. In particular, we consider the landscape under restricted strong convexity and restricted smoothness assumptions. We focus on the effect of rank overparametrization, that is, optimizing over matrices of rank strictly larger than that of the global optimum. Our main contribution is twofold:First, we give a positive landscape result for smooth factored formulations, showing that, under certain conditions on the rank parameters and restricted strong convexity/smoothness constants, every second-order critical point is globally optimal. This generalizes and unifies previous state-of-the-art results; in particular, our result allows for nuclear-norm regularization and applies to asymmetric matrix problems without requiring balancing of the factorization. A more statistical version of this result gives, under classical statistical assumptions, optimal recovery of low-rank matrices from noisy linear measurements.Second, we construct a family of counterexamples showing that our positive result is optimal in terms of all problem parameters. In particular, contrary to popular belief, rank overparameterization does not always improve the optimization landscape. Although our examples are adversarial, empirical evidence suggests that this phenomenon extends to standard statistical matrix sensing settings.Joint work with Richard Y. Zhang (UIUC). </div><div class="event_time">10:30 &bull; EPF Lausanne, CM 1 517</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://theory.epfl.ch/seminar/">Theory and Combinatorics Seminar</a></div><br /><div class="event_speaker"> Anastasiia  Sofronova</div><div class="event_title">No Constant-Cost Protocol for Point–Line Incidence <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Alice and Bob are given n-bit integer pairs (x, y) and (a, b), respectively, and they must decide if y = ax + b. We prove that the randomised communication complexity of this Point–Line Incidence problem is &#920;(log n). This confirms a conjecture of Cheung, Hatami, Hosseini, and Shirley (CCC 2023) that the complexity is super-constant, and gives the first example of a communication problem with constant support-rank but super-constant randomised complexity.This is joint work with Mika Göös, Nathaniel Harms and Florian K. Richter.</div><div class="event_time">11:00 &bull; EPF Lausanne,  INF 211 </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"> Yasha Eliashberg (Stanford )</div><div class="event_title">Invariants of open contact manifolds <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Any  open domain in the standard contact  ${\\mathbb R}^3$ which is diffeomorphic to ${\\mathbb R}^3$  is contactomorphic  to the standard contact ${\\mathbb R}^3$. Until now it was unknown  whether there are open subsets of the   standard contact  ${\\mathbb R}^{2n+1}$   which are diffeomorphic but  not contactomorphic to the standard contact ${\\mathbb R}^{2n-1}$. In the talk I will show that there are continuous families of  such pairwise non-contactomorphic domains for iany $n>2$.The main tool is a version of contact homology which can be defined for any open contact manifolds. This is a joint work with Kiran Ajij, Mahan Mj, Dishant Pancholi and Leonid Polterovich.</div><div class="event_time">15:15 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/mpseminar/seminar.html">Séminaire de Mathématique Physique </a></div><br /><div class="event_speaker"> Nathan  de Montgolfier</div><div class="event_title">Small perturbations of the classical Heisenberg model have a BKT transition <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Polyakov predicted in 1975 that the spin O(3) model(or classical Heisenberg model) should have exponential decay of correlations at all positive temperatures on Z^2.I will discuss the following result (j.w. with Christophe Garban). If we replace the Euclidean scalar product&#9001;s_i s_j&#9002; = s_i^x s_j^x + s_j^y s_j^y + s_j^z s_j^zby the &#949;-modified scalar product&#9001;s_i, s_j &#9002;_&#949; := s_i^x s_j^x + s_j^y s_j^y +( 1 - &#949;) s_j^z s_j^z, then for all 1 >= &#949; > 0, the S2 valued spin system with Gibbs measure proportional toexp(&#946; &#8721;{i&#8764;j} &#9001;s_i, s_j &#9002;_&#949;) has polynomial decay of correlations if &#946; is chosen large enough .</div><div class="event_time">16:15 &bull; Université de Genève, Conseil Général 7-9, Room 1-15</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_be"><a class="external" href="https://www.unibe.ch">Universität Bern</a></div><div class="event_type"><a class="external" href="https://www.math.unibe.ch/research/talks/colloquium/index_eng.html">Mathematisches Kolloquium </a></div><br /><div class="event_speaker">Prof. Dr. Erhard Aichinger (Johannes Kepler University Linz)</div><div class="event_title"><a class="external" href="https://www.math.unibe.ch/research/talks/colloquium/index_eng.html">Nullstellensätze</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />David Hilbert\'s Nullstellensatz (1983) for multivariate polynomials over the complex numbers is a cornerstone of algebraic geometry.</div><div class="event_time">17:15 &bull; Universität Bern, Sidlerstrasse 5, 3012 Bern, Room B6</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Tuesday, May 5      </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"> Mark  Pengitore (IMPAN (Varsovie))</div><div class="event_title">A linearity criteria for automorphism groups of hyperbolic groups <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />This talk will introduce various growth functions associated to a finitely generated groupwhich measure the difficulty of separating an element from the identity using epimorphismsto a fixed family of nonabelian finite simple groups with characteristic kernels as a functionof the word length. As an application of these functions, we provide a characterization ofwhen the automorphism group of a hyperbolic group is linear.</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"> Alberto Bucci (University of Edinburgh)</div><div class="event_title">Randomized techniques for the low-rank approximation of matrices and tensors: theory and applications <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Low-rank approximations play a central role in the efficient treatment of high-dimensional problems arising in scientific computing. In this talk, we present an overview of randomized techniques for constructing low-rank representations of matrices and tensors, highlighting both theoretical guarantees and practical performance. We begin with the matrix setting and classical randomized schemes, and then extend the discussion to tensor formats, including Tucker and Tensor Train decompositions. We further consider more general structures such as tree tensor networks, which provide a flexible framework for high-dimensional approximation. Finally, we illustrate how these techniques can be effectively integrated into iterative methods for the solution of large-scale partial differential equations. Numerical examples and applications will be discussed throughout.</div><div class="event_time">14:00 &bull; Université de Genève, Conseil Général 7-9, Room 1-05</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ge"><a class="external" href="https://unige.ch">Université de Genève</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/seminaires/lie-sem/">Lie groups and moduli spaces </a></div><br /><div class="event_speaker"> Thomas  Gerber  (Institut Camille Jordan, Lyon)</div><div class="event_title">Defect zero block enumeration <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In finite group theory, modular representations are assembled into blocks. A famous result states that, up to a few characteristic 2 and 3 exceptions, every finite simple group has a defect 0 block (i.e., a singleton block).In this talk, I will explain how to establish similar results in two different directions: for unipotent representations of finite classical groups, and for representations of Hecke algebras. In fact, in our context, blocks will be labelled by certain (multi)partitions called cores, and our entire approach will become combinatorial.This is based on joint work with Emily Norton, Nathan Chapelier, Nicolas Jacon, Cédric Lecouvey and Sylvie Corteel. </div><div class="event_time">15:30 &bull; Université de Genève, Conseil Général 7-9, Room 1-07</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://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">Daniela Portillo del Valle (Institut für Mathematik, Universität Zürich)</div><div class="event_title">What is... Markov Chain Monte Carlo? <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />&lt;p>Markov Chain Monte Carlo (MCMC) methods provide a general framework for numerical approximation and quantitative information analysis in settings where direct computation is infeasible. Relying on the long-time behavior of Markov chains, MCMC can be used to solve problems via random sampling of complex probability distributions. In this talk, we develop the intuition/theory behind this idea and show how it leads to practical computational methods. The Metropolis&ndash;Hastings algorithm is presented as a central example and, as an application, we revisit a real-life cipher-decoding problem. We also give a brief overview of further applications of MCMC across probability, statistics, and related fields.&lt;/p></div><div class="event_time">16:30 &bull; UZH Zentrum, Building KO2, Room F 150</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_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/sfs/news-and-events/stiefel-lectures">ETH-FDS Stiefel Lectures</a></div><br /><div class="event_speaker"> Joel A. Tropp (Caltech)</div><div class="event_title">Applied Random Matrix Theory <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Random matrices now play a role in many parts of computational mathematics. To advance these applications, it is desirable to have tools that are flexible, easy to use, and powerful. Over the last 25 years, researchers have developed a remarkable family of results, called matrix concentration inequalities, that meet the criteria. This lecture offers an invitation to the field of matrix concentration and its multifarious applications.</div><div class="event_time">17:15 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG , Room E 1.2</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Wednesday, May 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://www.math.uzh.ch/mat760">Ergodic theory and dynamical systems seminar</a></div><br /><div class="event_speaker">Dr. Zhiyuan Zhang (Université Paris 13 Nord)</div><div class="event_title">Ergodicity of conservative random dynamics <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />&lt;div class="elementToProof" style="font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-line: none; text-decoration-thickness: auto; text-decoration-style: solid; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: #000000;">We prove ergodicity of conservative random dynamics satisfying a certain hyperbolicity condition. The new feature of our result is that we do not require the non-existence of zero Lyapunov exponents. As a particular application, we show that if \\(R_1, R_2\\) in \\(\\mathrm{SO}(d + 1), d &ge; 2\\), generate a dense subgroup, then any pair \\((f_1, f_2)\\) of infinitely smooth volume preserving diffeomorphisms of the \\(d\\)-dimensional sphere that is sufficiently close to \\((R_1, R_2)\\) is ergodic with respect to the volume. Previously this was only known to hold when \\(d\\) is even by a result of Dolgopyat and Krikorian. Joint work in progress with Jonathan DeWitt and Dmitry Dolgopyat.&lt;/div></div><div class="event_time">13:30 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 19.1</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://calendar.google.com/calendar/embed?mode=AGENDA&height=600&wkst=2&bgcolor=%23FFFFFF&src=t36it03v52cus2detrvinlgk18%40group.calendar.google.com&color=%235F6B02&ctz=Europe%2FZurich">Groups, Arithmetic and Algebraic Geometry Seminar </a></div><br /><div class="event_speaker"> Sean Monahan</div><div class="event_title">Horospherical stacks <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Toric varieties are beloved in algebraic geometry because of their combinatorial theory using polyhedral fans; horospherical varieties vastly generalize this theory using so-called coloured fans. In the first 30 minutes, I will briefly introduce these horospherical varieties and their combinatorial theory (knowledge of toric varieties is not necessary). Then, in the next 45 minutes, I will introduce horospherical stacks -- extending horospherical varieties into the larger world of algebraic stacks, and generalizing the known class of toric stacks -- and discuss my results on developing their combinatorial theory.</div><div class="event_time">14:15 &bull; EPF Lausanne, GR A3 32</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ne"><a class="external" href="https://unine.ch">Universit&auml;t Neuchatel</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">Eduardo Camps Moreno (University of Bordeaux)</div><div class="event_title">Non-special Divisors on Kummer Extensions and Applications to AG Code Hulls <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />&lt;p>For an AG code \\(C=C(D,G)\\) on a curve \\(\\mathcal X/\\mathbb{F}_q\\), the structure of the hull \\(C\\cap C^\\perp\\) plays an important role in code equivalence, entanglement-assisted quantum codes, and efficient decoding. In general the hull need not be an AG code, but it becomes one when a certain divisor \\(A\\) associated to \\(G\\) and its dual divisor \\(H\\) is non-special.&lt;/p> &lt;p>This reduces the problem to determining when effective divisors of the form<br>\\[<br>A=\\sum_{P\\in \\mathbb{P}(\\mathcal X)}<br>&nbsp; &nbsp;\\max\\{v_P(G),\\,v_P(H)\\}\\,P<br>\\]<br>are non-special. In this talk I give explicit criteria for non-speciality of several classes of effective divisors of small degree on \\emph{Kummer extensions}. The characterization is obtained using the description of the Weierstrass semigroup at multiple points of these curves.&lt;/p> &lt;p>These results yield new families where the hull of an AG code can be written again as an AG code, and illustrate how the geometry of Kummer extensions controls the Riemann--Roch behaviour of low-degree divisors.&lt;/p></div><div class="event_time">15:00 &bull; Uni Neuchatel, B217</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/sam/news-and-events/zhacm-colloquia">Zurich Colloquium in Applied and Computational Mathematics</a></div><br /><div class="event_speaker"> Christian Alber (IWR, Univ. Heidelberg)</div><div class="event_title">Grassmann interpolation of optimal local approximation spaces <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Multiscale, parameter-dependent partial differential equations (PDEs) pose severe computational challenges due to strong coefficient heterogeneity and high-dimensional parameter spaces.We develop a geometric interpolation approach within the multiscale generalized finite element method (MS-GFEM) that targets the most expensive component: computing parameter-dependent optimal local approximation spaces. Leveraging the spatial localization of MS-GFEM and assuming local parameter dependence, we decompose the global problem into parametrically low-dimensional local subproblems. The optimal subspaces for each parameter are identified as points on a Grassmann manifold and approximated via Grassmann interpolation on sparse grids, which preserves the geometric structure of these spaces while efficiently handling high-dimensional parameter spaces.The resulting localized model reduction method inherits the nearly exponential spatial convergence of MS-GFEM and the parametric convergence rates of sparse grids. Numerical experiments for elliptic problems confirm the theoretical convergence results.</div><div class="event_time">16:30 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 19.2</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ne"><a class="external" href="https://unine.ch">Universit&auml;t Neuchatel</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">Arani Paul (University College Dublin)</div><div class="event_title">Flag Invariants of Rank Metric Codes (joint work with Dr. John Sheekey, Dr. Eimear Byrne) <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />&lt;div>The problem of determining when two F&lt;span style="font-size: xx-small;">q^m&lt;/span> -linear rank-metric codes are equivalent is important for reasons of both mathematical interest and for practical applications. Even though this problem can be efficiently solved computationally [2], finding structural properties that remain invariant under equivalence remains an active line of research. One of the main reasons behind that is the computational hardness of existing invariants, which act as distinguishers between equivalence classes. Beyond initial considerations such as minimum distance and weight enumerators, one of the most well-studied invariants is the generalised weights of a code [1, 3].&lt;/div> &lt;p>In this talk we introduce a new invariant for vector rank metric codes based on the support dimensions of complete flags of subcodes. We will demonstrate that these invariants are related to the generalised weights, but that they are both different and comparatively easier to compute than the generalised weights. We also relate the new invariants to the corresponding q-system of the code.&lt;/p> &lt;div>References:&lt;/div> &lt;div>[1] T. H. Randrianarisoa. A geometric approach to rank metric codes and a classification of constant weight codes. Designs, Codes and Cryptography, 88:1331&ndash;1348, 2020&lt;/div> &lt;div>[2] A. Couvreur, T. Debris-Alazard, and P. Gaborit. On the hardness of code equivalence problems in rank metric. arXiv:&lt;span id="OBJ_PREFIX_DWT115_com_zimbra_phone" class="Object" role="link">2011.04611, 2020&lt;/span>.&lt;/div> &lt;div>[3] G. Marino, A. Neri, and R. Trombetti. Evasive subspaces, generalized rank weights and near mrd codes. Discrete Mathematics, 346(12):&lt;span id="OBJ_PREFIX_DWT116_com_zimbra_phone" class="Object" role="link">113605, 2023&lt;/span>.&lt;/div></div><div class="event_time">16:30 &bull; Uni Neuchatel, B217</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/seminar-on-stochastic-processes">Seminar on Stochastic Processes</a></div><br /><div class="event_speaker">Prof. Dr. Ariel Yadin (Ben-Gurion University of the Negev)</div><div class="event_title">Aggregation models on cylinders <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />A cylinder is a the graph obtained by taking the product of a finite graph with the half-line N.We consider two aggregation models on cylinders, internal and external DLA, analyzing asymptotics as the size of the base graph grows to infinity.There is a stark contrast between the behavior of these two models. External DLA is notoriously very difficult to analyze, whereas for internal DLA we have very good understanding of the limiting shape and even a type of CLT for the fluctuations.This is based on joint works with Itai Benjamini, Ahmed Bou-Rabi and Vittoria Silvestri. </div><div class="event_time">17:15 &bull; ETH Zentrum, Winterthurerstrasse 190, Z&uuml;rich, Building Y27, Room  H12</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Thursday, May 7      </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"> Sylvain Crovisier (Université Paris-Saclay)</div><div class="event_title">Ergodic theory of surface diffeomorphisms</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"> Gianluca Somma (Università di Padova)</div><div class="event_title"><a class="external" href="https://dmi.unibas.ch/de/studium/mathematik/doktorat/bernoullis-tafelrunde/detail/gianluca-somma-padova/">Well-posedness of transport equations in Heisenberg groups</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Abstract Transport equations describe the evolution of quantities conserved along a velocity field and play a central role in Analysis and Mathematical Physics. In the Euclidean setting, DiPerna-Lions (1989) proved existence and uniqueness of solutions for velocity fields with Sobolev regularity. In this talk, I will discuss the extension of this theory to the non-Euclidean setting of Heisenberg groups, where the natural assumption is horizontal Sobolev regularity. In particular, I will present a recent result on existence and uniqueness of solutions to transport equations associated with the class of contact velocity fields. This is joint work with L. Ambrosio, S. Verzellesi and D. Vittone.</div><div class="event_time">12:15 &bull; Universität Basel, Seminarraum 05.001, Spiegelgasse 5</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="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"> Beomjun Sohn (Universität Aachen)</div><div class="event_title">Hofer-Zehnder capacity of disk tangent bundles of triaxial ellipsoids, I <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Symplectic capacities are invariants in symplectic geometry that provide a notion of size and are monotone under symplectic embeddings. One important example is the Hofer–Zehnder capacity, defined in terms of Hamiltonians compactly supported on the given symplectic manifold. In the first talk, we discuss methods for proving the finiteness of this capacity and some of its applications to Hamiltonian dynamics. In particular, we focus on cotangent bundles, where the almost existence theorem is still open in general, but is implied by the finiteness of the Hofer–Zehnder capacity.</div><div class="event_time">12:30 &bull; Université de Neuchâtel, Rue Emile-Argand 11, Room B217</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"> Anne Moreau</div><div class="event_title"> Double Poisson vertex algebras from jet algebras and quivers <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Double Poisson vertex algebras can be viewed as vertex-algebraic analogues of double Poisson algebras. In this talk, I will explain how to construct such structures using the jet algebra construction. This construction naturally leads to Poisson vertex algebras on representation spaces of double Poisson (vertex) algebras. Using related procedures such as Poisson reductions and Hamiltonian reductions, we obtain a variety of interesting examples of double Poisson vertex algebras, in particular those arising from double quivers. I will also discuss motivations coming from vertex algebras. This is based on joint works with Tristan Bozec and Maxime Fairon.</div><div class="event_time">14:15 &bull; EPF Lausanne, CM 1 517</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/~palmeran/topsem.html">Séminaire de Topologie et Géométrie </a></div><br /><div class="event_speaker"> Lukas  Lewark (ETH Zürich)</div><div class="event_title">Concordance, Rasmussen invariants, Satellites and Twisting <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />A knot in the 3-sphere is slice if it bounds a smooth disk in the 4-ball. Knots modulo slice knots form an abelian group called the concordance group. We will explore what can be said about this group by mixing the following three ingredients: Rasmussen invariants (which come from Khovanov homology); satellite knots (which are the result of knotting a solid torus that itself contains a knot); and twisting (which means to put a full twist into a bunch of strands of a knot). This talk will feature joint work with Claudius Zibrowius, and joint work in progress with Chiara Donatone, Marc Kegel, and Paula Truöl.</div><div class="event_time">14:15 &bull; Université de Genève, Conseil Général 7-9, 1-15</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://stat.ethz.ch/events/zukost">ZueKoSt: Seminar on Applied Statistics</a></div><br /><div class="event_speaker"> Björn  Bornkamp (Novartis)</div><div class="event_title">A Structured Workflow to Assess Treatment Effect Heterogeneity in Drug Development <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Understanding whether a treatment works differently across patient subgroups is a central question in drug development. However, answering it reliably is notoriously difficult. Clinical trials are typically powered for overall treatment effects, leaving subgroup analyses underpowered and vulnerable to both false positives and false negatives, as illustrated by multiple real cases where subgroup findings couldn\'t be confirmed in follow-up trials. Despite these severe limitations however questions around treatment effect heterogeneity are of great interest to sponsors, regulators, and clinicians alike and need to be addressed in drug development.In this talk, I will present WATCH (Workflow to Assess Treatment EffeCt Heterogeneity) for exploratory assessment of TEH in randomized clinical trials. The challenges resulting from insufficient data-based information on the question of interest (TEH) are approached via (i) providing a structured and pre-planned analysis approach for this exploratory question, providing more standardization and reducing  analyst degrees of freedom, (ii) documenting a-priori, external evidence on potential effect modifiers upfront and as part of the workflow and (iii) utilizing flexible, multivariate analysis methods based on statistical learning methods. I will present the workflow steps, and discuss current analysis methods used to implement the workflow, as well as open methodological questions.</div><div class="event_time">16:15 &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_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/mat675.1">PDE and Mathematical Physics</a></div><br /><div class="event_speaker">Prof. Dr. Georgios Moschidis (EPFL)</div><div class="event_title">Naked singularities with finite blue-shift for the Einstein--massless Vlasov system <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />&lt;div class="elementToProof"> &lt;p class="elementToProof">In his celebrated proof of the weak cosmic censorship conjecture for the spherically symmetric Einstein-scalar field system, Christodoulou exploited the following property of that specific matter model:&nbsp;Naked&nbsp;singularities, when they arise, exhibit infinite blue-shift along the null geodesics terminating at the singularity. This behaviour is consistent with self-similarity: Even for more general spherically symmetric matter models, it can be shown that self-similar&nbsp;naked&nbsp;singularities&nbsp;must exhibit infinite blue-shift. Whether, for these more general models, all&nbsp;naked&nbsp;singularities&nbsp;have the infinite blue shift property (and hence are potentially subject to an instability mechanism analogous to that introduced by Christodoulou) still remains an open question.&lt;/p> &lt;/div> &lt;div class="elementToProof"> &lt;p class="elementToProof">&nbsp;&lt;/p> &lt;/div> &lt;div class="elementToProof"> &lt;p class="elementToProof">In this talk, we will present the construction of a spherically symmetric solution to the Einstein-massless Vlasov system which contains a locally naked singularity with finite total blue-shift along its past null cone. The initial data giving rise to this solution have limited differentiability, but belong to a regularity class above the scale invariant threshold.&lt;/p> &lt;/div></div><div class="event_time">16:15 &bull; UZH Irchel, Winterthurerstrasse 190, Z&uuml;rich, Building Y27, Room H 35/36</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">Prof. Dr. Christoph Czichowsky (LSE)</div><div class="event_title">No-Arbitrage, Superreplication and Utility Maximisation in Propagator Price Impact Models <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We develop a comprehensive mathematical finance framework for propagator models with transient linear price impact. These models lead to infinite-dimensional, non-Markovian control problems and fall outside the scope of classical arbitrage and duality theory. We establish a fundamental theorem of asset pricing, a superreplication theorem with liquidity-adjusted risk measures, and a full convex-duality approach to utility maximisation. Despite the non-linearity of preferences and the path-dependent impact structure, we show that optimal strategies can be obtained from an equivalent frictionless optimisation problem under a suitably constructed shadow price.</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, May 8      </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"> Tom Hutchcroft (California Institute of Technology (Caltech))</div><div class="event_title">Dimension dependence of critical phenomena in percolation</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_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"> Beomjun Sohn (Universität Aachen)</div><div class="event_title">Hofer–Zehnder Capacity of Disk Cotangent Bundles of Triaxial Ellipsoids, II <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In this second talk, we study the Hofer–Zehnder capacity of disk cotangent bundles of convex 2-spheres. While its finiteness is known and can be established by several methods as in the first talk, its explicit value is understood only in the round case. We show that, for triaxial ellipsoids, the Hofer–Zehnder capacity can be described in terms of the lengths of simple closed geodesics with prescribed Morse indices. The computation is based on two inequalities, derived using singular Riemannian billiards and Gromov–Witten theory. This is joint work with Johanna Bimmermann.</div><div class="event_time">13:00 &bull; Université de Neuchâtel, Rue Emile-Argand 11, Room B217</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/number-theory-seminar">Number Theory Seminar</a></div><br /><div class="event_speaker">Prof. Dr. Dimitri Stelio Wyss (EPFL)</div><div class="event_title">New entries in the function-sheaf dictionary for p-adic integrals <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Let R be the ring of integers of a p-adic field with residue field k. Given an algebraic variety X over R one can consider the function that associates to any k-point x of X the p-adic volume of the ball of R-points specializing to x. Unless X has quotient singularities it is unknown whether this function is the trace of Frobenius of some interesting l-adic sheaf on X. In joint work with M. Groechenig and P. Ziegler we study this question for certain moduli spaces X appearing in enumerative geometry, where the sheaf in question turns out to be the intersection complex.</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/labs/anmath/seminars/">Seminar of Analysis </a></div><br /><div class="event_speaker"> Rajendra  Beekie  (Imperial College London)</div><div class="event_title">Advection by shears with critical points in the presence of diffusion <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Shear flows are one of the most well studied classes of vector fields. An important feature of shear flows is their ability to generate small scales and mix quantities that they transport. For passive scalar transport, these mixing rates can be quantified in a rather straightforward way. However, quantifying mixing rates for 2d Euler linearized around non-monotone shears is surprisingly subtle due to an effect known as vorticity depletion which is not present in the passive transport case. Since real fluids have viscosity, a natural question is to understand whether mixing rates persist in the presence of viscosity. In this talk, I will discuss recent progress on addressing this question for both the passive scalar advection-diffusion equation and the linearized Navier-Stokes equation. Based on joint work with Dallas Albritton (University of Wisconsin), Shan Chen (University of Minnesota), and Hao Jia (University of Minnesota). </div><div class="event_time">14:15 &bull; EPF Lausanne, MA B1 11</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"> Aikaterini  Papagiannouli (University of Pisa)</div><div class="event_title">Beyond NNGP: Large Deviations and Feature Learning in Bayesian Neural Networks <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Bayesian neural networks, in the overparameterized and infinite-width regime, are now well understood. Under mild assumptions, their prior converges to a Gaussian process (NNGP), and both Bayesian inference and training dynamics can be described by kernel methods. Although, these infinite-width limits provide tractable models and sharp theoretical insights, they also exhibit a fundamental rigidity: the induced feature representation becomes fixed and independent of data. As a result, feature learning disappears in the infinite-width limit, and Bayesian inference reduces to kernel regression with a predetermined kernel.In this talk, I present a complementary large-deviation perspective on wide Bayesian neural networks. Rather than studying typical Gaussian fluctuations, we analyse exponentially rare, but statistically dominant, configurations that govern posterior concentration as width grows. At this scale, Bayesian inference becomes variational: posterior mass concentrates near minimizers of an explicit functional rate function defined directly on predictors.Our main result shows that, in contrast to the Gaussian-process limit, the posterior large-deviation rate function involves a joint optimization over predictors and internal covariance kernels. This nested variational structure leads to data-dependent kernel selection and provides a mechanism for feature learning that persists even in the infinite-width regime. In particular, we prove that the posterior-optimal kernel generically differs from the NNGP kernel. Joint work with D. Trevisan</div><div class="event_time">15:15 &bull; EPF Lausanne, CM 1 517</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>';