var sms = '<div id="sms_bulletin">  <div id="sms_header">  <div class="do_not_print" id="arrow_left"><a href="?next=-23"><img src="//www2.math.ethz.ch/smsjs/images/arrow_left.png"/></a></div><div class="do_not_print" id="arrow_right"><a href="?next=-21"><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. 2</span>      <span style="float: right; text-align:right; width: 250px;">23.2 - 27.2.2026</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, February 23      </div>      <div class="day_content">        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://uzh.ch">Universit&auml;t Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/talks-in-mathematical-physics">Talks in Mathematical Physics</a></div><br /><div class="event_speaker"> Ioannis Chrysikos</div><div class="event_title">Title T.B.A. <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />tba</div><div class="event_time">13:30 &bull; UZH Irchel, Winterthurerstrasse 190, Z&uuml;rich, Building Y27, Room H 25</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/symplectic-geometry-seminar">Symplectic Geometry Seminar</a></div><br /><div class="event_speaker"> Christian Urech (ETHZ)</div><div class="event_title">Characterizing varieties by their groups of birational transformations <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />To an algebraic variety X one associates its group of birationaltransformations Bir(X). In the last decades, these groups and their richalgebraic, geometric, and dynamic structures have attracted a great dealof interest. In this talk, I will explain how the group structure ofBir(X) characterizes in many important cases the variety X. Inparticular, we will obtain new rationality criteria.</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"> Alice Guionnet (ENS Lyon)</div><div class="event_title">Random tilings and Nekrasov\'s equation <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We will discuss this limit shape of random tilings and their fluctuations around it, for general domains that do not need to be simply connected. In particular, we show that the Kenyon-Okounkov conjecture that these fluctuations are described by a Gaussian Free Field is valid for a wide variety of models. Because of their strong constraints, random tiles can be considered as strongly interacting random variables.Their analysis is closely related with that of the spectrum of random matrices and the so called Beta-ensembles or Coulomb gases. In this talk, we will introduce discrete Beta-ensembles and their specialization to lozenge tilings, and explain how to use a system of equations introduced by Nekrasov to study them. This talk is based on joint works with Alexei Borodin, Gaetan Borot and Vadim Gorin.</div><div class="event_time">16:15 &bull; Université de Genève, Conseil Général 7-9, Room 1.15</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Tuesday, February 24      </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"> Paul-Henry  Leemann  (Xi\'an Jiaotong-Liverpool University)</div><div class="event_title">Cayley graphs with few automorphisms: beyond finitely generated groups <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Given a group G, the choice of a generating set S turns G onto a metric space (G,d_S), on which G faithfully acts by left multiplication. While the group of isometries of (G, d_S) is often much larger than G, it can sometimes coincide with G.In such a case, we say that (G,d_S) is called a graphical rigid representation (GRR) of G. The name comes from the fact that Iso(G,d_S) is isomorphic to the automorphism group of the Cayley graph Cay(G,S).A group G admits a GRR if and only if it can be realised as the automorphism group of a "nice" graph. The classification of groups admitting GRR began in the late 1960s and was completed in 1981 for finite groups. In 2022, alongside Mikael de la Salle, we solved the infinite finitely generated case. In this talk, I will explain how to handle countable (not necessarily finitely generated) groups. While some methods for finitely generated groups remain applicable in this broader context, new ones are also necessary.  Specifically, I\'ll define a "small generating set" for groups of arbitrary cardinality and prove that every group has such a generating set.The talk will be accessible to a wide audience and no prior knowledge of the subject is required.</div><div class="event_time">10:30 &bull; Université de Genève, Conseil Général 7-9, Room 1-05</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://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"> Felicien Comtat (Bonn)</div><div class="event_title">Moments of symmetric square L-functions on GL(3) <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In joint work with Valentin Blomer we give an asymptotic formula for the first moment of the symmetric square L-function on GL(3) in the level aspect. I will give some background on the symmetric square L-function on GL(3), followed by an overview of the method, which combine an approximate functional equation, the Kuznetsov formula for GL(3), and some ingredients of representation theory allowing to determine the sign of the functional equation in terms of the Fourier coefficients.</div><div class="event_time">14:15 &bull; EPF Lausanne</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_dis"><a class="external" href="https://unidistance.ch">UniDistance Suisse</a></div><div class="event_type"><a class="external" href="https://unidistance.ch/en/mathematiques-et-informatique/recherche/number-theory/number-theory-seminar">Number Theory Seminar</a></div><br /><div class="event_speaker"> Gal  Porat  (Weizmann Institute of Science)</div><div class="event_title">Solid Locally Analytic Representations in Mixed Characteristic <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Locally analytic representations of p-adic Lie groups with Q_p coefficients play an important role in p-adic Hodge theory and in the p-adic Langlands program. This perspective reveals important differential structures, such as the Sen and Casimir operators.A few years ago, Rodrigues Jacinto and Rodriguez Camargo developed a "solid" version of this theory using the language of condensed mathematics, which provides more robust homological tools (comparison theorems, spectral sequences...) for studying these representations.This talk will present work that extends this solid theory to a much broader class of mixed characteristic coefficients, such as F_p((X)) or Z_p[[X]]&lt;p/x>, as well as semilinear representations. I plan to explain how these ideas relate to mixed characteristic phenomena in p-adic Hodge theory and the Langlands program.</div><div class="event_time">15:00 &bull; <a class="external" href="https://tinyurl.com/UniDistanceNTSeminar">UniDistance Suisse, Zoom</a></div>        </div>        <div class="day_content_item normal"><div class="event_location uni_dis"><a class="external" href="https://unidistance.ch">UniDistance Suisse</a></div><div class="event_type"><a class="external" href="https://distanceuniversity.ch/academic-events/mathematics-colloquium/">Mathematics Colloquium </a></div><br /><div class="event_speaker">Dr. Fabian Ziltener (ETH Z&uuml;rich, Switzerland)</div><div class="event_title"><a class="external" href="https://unidistance.ch/evenement/capacities-as-a-complete-symplectic-invariant">Capacities as a complete symplectic invariant</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />This talk is about joint work with Yann Guggisberg. The main result is that the set of generalized symplectic capacities is a complete invariant for every symplectic category whose objects are of the form (<i>M</i>, &#969;), such that <i>M</i> is compact and 1-connected, &#969; is exact, and there exists a boundary component of <i>M</i> with negative helicity. This answers a question of Cieliebak, Hofer, Latschev, and Schlenk. It appears to be the first result concerning this question, except for results for manifolds of dimension 2, ellipsoids, and polydiscs in <i>R</i><sup>4</sup>.</div><div class="event_time">16:30 &bull; <a class="external" href="https://fernuni.zoom.us/j/67733135300">UniDistance Suisse, Zoom</a></div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://uzh.ch">Universit&auml;t Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://www.math.uzh.ch/mat075.1">Zurich Graduate Colloquium</a></div><br /><div class="event_speaker">Tristan Humbert (Sorbonne Université)</div><div class="event_title">What are... magic angles? <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />&lt;div dir="auto" data-olk-copy-source="MessageBody">I will introduce the main objects from spectral theory of&lt;/div> &lt;div dir="auto">infinite dimensional operators: the domain, the resolvent and the&lt;/div> &lt;div dir="auto">spectrum. I will then describe an analytic family of non normal operator&lt;/div> &lt;div dir="auto">\\(D(\\alpha)\\) (for \\(\\alpha \\in \\mathbb{C}\\)) such that \\(\\alpha\\mapsto\\mathrm{Spec}(D(\\alpha))\\) is discontinuous. The points of discontinuity are called&lt;/div> &lt;div dir="auto">"magic angles" and I will show that there are infinitely many of them.&lt;/div> &lt;div dir="auto">This is joint work with Simon Becker and Maciej Zworski.&lt;/div> &lt;div dir="auto">&nbsp;&lt;/div> &lt;div dir="auto">The existence of these angles were predicted by Bistritzer&ndash;MacDonald in&lt;/div> &lt;div dir="auto">2011 and were observed experimentally in 2018. They correspond to&lt;/div> &lt;div dir="auto">specific "twisting angles" between two sheets of graphene for which we&lt;/div> &lt;div dir="auto">observe supraconductivity.&lt;/div></div><div class="event_time">16:30 &bull; UZH Zentrum, Building KO2, Room F 150</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Wednesday, February 25      </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. Vikramaditya Giri (Universität Zürich)</div><div class="event_title">A Spectral Gap for Spinors on Hyperbolic Surfaces <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />&lt;p>We&apos;ll recall the spectral theory of the Laplacian on functions on a hyperbolic surface and show that as the genus goes to infinity, one can&apos;t obtain a uniform spectral gap above 1/4 - the bottom of the \\(L^2\\) spectrum of the hyperbolic plane. We&apos;ll show that this obstruction goes away when one instead considers the spectrum of the Dirac operator on spinors on a hyperbolic surface with a choice of spin structure. We&apos;ll sketch a construction of these surfaces with such a uniform spectral gap and note that these surfaces can be taken to be arithmetic.&lt;/p> &lt;p><br>Based on joint work with Anshul Adve.&lt;/p></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://www.epfl.ch/labs/mathicse/">Computational Science and Engineering </a></div><br /><div class="event_speaker"> Marius  Zeinhofer</div><div class="event_title">Geometric Optimization in Scientific Machine Learning <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We discusses an “optimize-then-project” approach for applications in scientific machine learning. The key idea is to design algorithms at the infinite-dimensional level and subsequently discretize them in the tangent space of the neural network ansatz. We illustrate this approach in the context of the variational Monte Carlo method for quantum many-body problems, where neural quantum states have recently emerged as powerful representations of high-dimensional wavefunctions. In this setting, we recover the celebrated stochastic reconfiguration algorithm, interpreting it as a projected Riemannian L2 gradient descent method. We further explore extensions to Riemannian Newton methods, and conclude with considerations related to the scalability of these schemes. </div><div class="event_time">13:30 &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://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"> Olivier  Schiffmann</div><div class="event_title">Hecke operators, COHAs and chi-independence for symplectic surfaces <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In his study of Gopakumar-Vafa curve counting invariants on CY 3folds, Toda conjectured that the (BPS) cohomology of moduli stacks of semistable one-dimensional sheaves only depends on the curve class (and not on the Euler characteristics) of sheaves considered. This allows one to extend the computation of these invariants to the singular setup. We prove this conjecture (and in fact a slightly stronger statement, relative over the Chow variety) for CY3 folds of the form $X=S\\times \\mathbb{A}^1$, where $S$ is a symplectic surface. For this we use the theory of (2d and 3d) cohomological Hall algebras,  as well as Hecke operators of punctual modifications on surfaces. As a corollary, we obtain a computation of both the intersection homology of the (coarse) moduli space and the homology of the moduli stack of semistable coherent sheaves on a projective K3 or abelian surface for any Mukai vector and (generic) polarization. We also obtain an extension of Markman \'tautological generation of the cohomology\' theorem to the case of nonprimitive Mukai vectors. This is joint work with Ben Davison, Lucien Hennecart, Tasuki Kinjo and Eric Vasserot.</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_be"><a class="external" href="https://www.unibe.ch">Universität Bern</a></div><div class="event_type"><a class="external" href="https://www.imsv.unibe.ch/research/talks/colloquia/index_eng.html">Colloquia on Probability and Statistics </a></div><br /><div class="event_speaker">Dr. Katerina Papagiannouli (University of Pisa)</div><div class="event_title"><a class="external" href="https://www.imsv.unibe.ch/research/talks/schedule/index_eng.html">Beyond NNGP: Large Deviations and Feature Learning in Bayesian Neural Networks</a> <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.</div><div class="event_time">16:15 &bull; Universität Bern, Hörsaal B78, ExWi, Sidlerstrasse 5, 3012 Bern</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">Dr. David Wiedemann (TU Dortmund)</div><div class="event_title">Interface conditions for Maxwell’s equations by homogenization of thin inclusions: transmission, reflection or polarization <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We investigate the time-harmonic Maxwell equations in complex geometries, with particular emphasis on configurations that model polarization filters or Faraday cages. The domains under consideration contain perfectly conducting inclusions that are periodically distributed along a surface. We analyze the asymptotic regime in which both the size of the inclusions and the distance between them tend to zero, and we derive the resulting effectiveinterface conditions. Depending on the geometric properties of the inclusions, the limiting system exhibits markedly different behaviors: perfect transmission, perfect reflection orpolarization effects</div><div class="event_time">16:30 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 19.2</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://uzh.ch">Universit&auml;t Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/seminar-on-stochastic-processes">Seminar on Stochastic Processes</a></div><br /><div class="event_speaker">Dr. Sahar Rabin Diskin (ETH Z&uuml;rich, Switzerland)</div><div class="event_title">Mixing time and diameter of the percolated hypercube <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We study bond percolation on the d-dimensional hypercube Q^d with edge retention probability p=c/d. It is well known that when c>1 is fixed, a unique giant component emerges. In this regime, we resolve conjectures of Bollobás, Kohayakawa, and &#321;uczak (1994) and of Benjamini and Mossel (2003), showing that the typical diameter of the giant component is &#920;(d), and that the mixing time of the lazy random walk on it is &#920;(d^2). In the talk, we will introduce the notion of mixing time and its connection to expansion properties of subsets of the giant. We will then discuss some of the key obstacles in obtaining this result, and in particular why classical sprinkling techniques are insufficient for this problem. Finally, we will explain how our new approach - based on analysing the effect of small perturbations and establishing stability under thinning - overcomes these obstacles. This method also yields tight large-deviation estimates for the size of the giant.  Based on joint work with Michael Anastos, Lyuben Lichev, and Maksim Zhukovskii.</div><div class="event_time">17:15 &bull; UZH Irchel, Winterthurerstrasse 190, Z&uuml;rich, Building Y27, Room  H12</div>        </div>      </div>    </div>    <div class="day">      <div class="day_title">        Thursday, February 26      </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_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"> Luke Conners (UZH)</div><div class="event_title">Algebraic Structures in Colored HOMFLY Homology <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />I will discuss a 2013 package of conjectures due to Gorsky--Gukov--Stoši&#263; (GGS) regarding colored HOMFLY homology of links and survey some recent progress towards their resolution. In particular, I will discuss ongoing work to construct spectral sequences from HOMFLY homology to link homologies associated to the Type A Lie superalgebras gl(m|n), mirror symmetry properties between different colorings and the special cases in which this result is known, the role of Gorsky--Hogancamp\'s y-ified homology in the whole story, and the conjectural "quadruply-graded" homology underlying these structures. These conjectures generalize the 2005 package of Dunfield--Gukov--Rasmussen to the setting of colored homology, and I will take the DGR conjectures as a point of comparison throughout.</div><div class="event_time">14:15 &bull; Université de Genève, Conseil Général 7-9, Room 1-15</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_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"> Diego Izquierdo</div><div class="event_title">Transfer principles for Galois cohomology and Serre\'s conjecture II <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In this talk, I will present some transfer principles for the cohomological dimension of fields. I will then show some applications to Serre\'s Conjecture II, which predicts a characterization ofcohomological dimension 2 fields in terms of rational points on torsors under algebraic groups. In particular, we will see that Serre\'s Conjecture II for characteristic zero fields implies the same conjecture for positive characteristic fields. This is joint work with Giancarlo Lucchini Arteche.</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_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">Dr. Lars Eric Hientzsch (KIT Karlsruhe)</div><div class="event_title">On leapfrogging vortex rings for the Euler equations <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />&lt;p>In 1858, Helmholtz conjectured that coaxial vortex rings in 3D inviscid fluids can exhibit the "leapfrogging" dynamics, where rings repeatedly pass through one another. While well-documented experimentally, this phenomenon involves singular interactions that are difficult to capture analytically. In this talk, we present a rigorous justification of these dynamics for the 3D incompressible Euler equations. We consider a general class of initial data corresponding to N sharply concentrated coaxial vortex rings and prove that the leapfrogging motion persists on a logarithmic time scale. The core of the analysis requires new estimates to propagate the concentration of vorticity despite the singular mutual interactions required for the phenomenon to occur.&nbsp;&lt;/p> &lt;p>Joint work with M. Donati, C. Lacave, and E. Miot.&lt;/p></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"> Lucas Morisset (École Normale Supérieur de Lyon)</div><div class="event_title">Non-Asymptotic Analysis of Data Augmentation for Precision Matrix Estimation <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />This paper addresses the problem of inverse covariance (also known as precision matrix) estimation in high-dimensional settings. Specifically, we focus on two classes of estimators: linear shrinkage estimators with a target proportional to the identity matrix, and estimators derived from data augmentation (DA). Here, DA refers to the common practice of enriching a dataset with artificial samples--typically generated via a generative model or through random transformations of the original data--prior to model fitting. For both classes of estimators, we derive estimators and provide concentration bounds for their quadratic error. This allows for both method comparison and hyperparameter tuning, such as selecting the optimal proportion of artificial samples. On the technical side, our analysis relies on tools from random matrix theory. We introduce a novel deterministic equivalent for generalized resolvent matrices, accommodating dependent samples with specific structure. We support our theoretical results with numerical experiments.</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, February 27      </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_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"> Lukas Schimmer</div><div class="event_title">Spectral theory of functional difference operators  <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Functional difference operators arise naturally in several areas of mathematical physics. As differential operators of “infinite order”, they push classical spectral methods to their limits. In this talk, I will give an overview of some of these techniques, notably the Birman–Schwinger principle, and present recent results establishing Lieb–Thirring-type bounds for the discrete spectrum of such operators. I will also discuss the emergence of resonances in a particular case.</div><div class="event_time">14:00 &bull; Université de Genève, Conseil Général 7-9, Room 8-08</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. Laurent Berger (ENS de Lyon)</div><div class="event_title">Integer-valued polynomials and p-adic Fourier theory <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Let K be a finite extension of Qp and let o_K be its ring of integers. The theory of Lubin-Tate formal groups allows us to construct many integer-valued polynomials on o_K. To what extent do these polynomials generate all integer-valued polynomials on o_K? I will explain some results of de Shalit and Iceland, as well as of Ardakov, Sprang and myself on this question. I will also explain the motivation (p-adic Fourier theory) for our results.</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>    </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>';