var sms = '<div id="sms_bulletin">  <div id="sms_header">  <div class="do_not_print" id="arrow_left"><a href="?next=-10"><img src="//www2.math.ethz.ch/smsjs/images/arrow_left.png"/></a></div><div class="do_not_print" id="arrow_right"><a href="?next=-8"><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;">5.5 - 9.5.2025</span>      <span style="text-align: center; display: block; width: 250px; margin: auto; position: relative;">Spring Semester 2025</span>    </div>  </div>  <div></div>  <div id="sms_content">    <div class="day">      <div class="day_title">        Monday, May 5      </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"> Riccardo Tosi (Essen)</div><div class="event_title"><a class="external" href="https://dmi.unibas.ch/de/studium/mathematik/doktorat/bernoullis-tafelrunde/detail/bernoullis-tafelrunde-riccardo-tosi-essen/">Irrationality proofs and periods of hyperplane arrangements.</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The values of the Riemann zeta function at odd positive integers greater than 1 are conjectured to be transcendental, yet even their irrationality remains a mostly open question. Recently, new inputs to irrationality proofs have come from geometric methods, especially in connection with periods of hyperplane arrangements. In this talk, we will have a look at some classical strategies to prove the irrationality of a number. Then, we will realize zeta values as periods of some algebraic varieties and finally we will try to understand how this geometric perspective can give further impulse to irrationality proofs for zeta values. abstract</div><div class="event_time">12:15 &bull; Universität Basel, Seminarraum 05.002, Spiegelgasse 5</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"> Noah Porcelli (Imperial College London, United Kingdom)</div><div class="event_title">Parametrised Whitehead torsion of families of nearby Lagrangians <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The parametrised Whitehead torsion is an invariant of families of manifolds, and can be viewed as a map to an algebraic K-theory space. A strong version of the nearby Lagrangian conjecture says that when applied to families of closed exact Lagrangians in a cotangent bundle, this invariant vanishes. Abouzaid and Kragh showed that in this case, this map lands in the trivial path component of the target, i.e. is trivial on \\pi_0. Using generating functions, we find strong constraints on what this map does to higher homotopy groups. I\'ll illustrate this with some concrete consequences for the symplectic mapping class group of T^*T^n relative to the 0-section. This is based on joint work-in-progress with Sylvain Courte. </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"> Clément Cosco (Université Paris Dauphine)</div><div class="event_title">The subcritical phase of 2d directed polymers <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Directed polymers in random environment model the behavior of a long, directed chain that spreads among an inhomogeneous environment. Dimension two turns out to be critical for the model, which then exhibits a phase transition found by renormalizing the temperature at a suitable rate (Caravenna-Sun-Zygouras 17’).  In this talk, I will focus on the high temperature regime and present works in collaboration with Anna Donadini and Francesca Cottini about an elementary proof of the central limit theorem for the partition function (CSZ17) and its extension to space-correlated noise. The proof relies on a decomposition that also plays a central role in a related work with Shuta Nakajima and Ofer Zeitouni, where we study extreme value statistics of the partition function in connection to branching random walks (with a decreasing variance profile). I will try to explain this link, as well as some results about high moments estimates that we require for the proof.</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. Maté Matolcsi (Rényi Institute Budapest)</div><div class="event_title"><a class="external" href="https://www.math.unibe.ch/research/talks/colloquium/index_eng.html">Fuglede\'s conjecture, spectral sets and weak tiling</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />A bounded measurable set X in a d-dimensional Euclidean space is called spectral if the function space L^2(X) admits an orthogonal basis of exponentials. The easiest example is the unit cube, where elementary Fourier analysis tells you that complex exponentials with integer frequencies form an orthogonal basis.Fuglede\'s conjecture stated that a set X is spectral if and only if it tiles the space by translation. In general, the conjecture turned out to be false, but it wasrecently proved for all convex bodies in all dimensions in ajoint work of Nir Lev and Mate Matolcsi. We will review theproof, which includes the notion of weak tiling as a key ingredient. Other results and open problems related to weak tiling will also be mentioned.</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 6      </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"> Leandro Arosio (University of Rome, Tor Vergata)</div><div class="event_title">A Julia-Wolff-Carathaléodory theorem in convex domains of finite type <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The classical Julia-Wolff-Carathéodory shows that, if f is a holomorphic self-map of the disc, the derivative f&#8242; admits a positive nontangential limit near any boundary regular fixed point z, and the limit equals the dilation of f at z which can be computed in terms of the Poincaré distance. This result had several generalizations to several variables, in particular by Rudin and Abate. In this talk I will show how to generalize the theorem to the context of a convex domain &#937; &#8834; Cq of D’Angelo finite type, using as a main tool the fact that &#937; is Gromov hyperbolic with respect to the Kobayashi distance k&#937; and that holomorphic maps do not expand k&#937;.This is a joint work with Matteo Fiacchi. </div><div class="event_time">10:30 &bull; Université de Genève, Conseil Général 7-9, Room 1-05</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_la"><a class="external" href="https://www.epfl.ch">EPF Lausanne</a></div><div class="event_type"><a class="external" href="https://www.unil.ch/dsa/en/home/menuinst/seminaires--evenements/research-seminars.html">Talks in Actuarial Mathematics </a></div><br /><div class="event_speaker"> Arthur  Charpentier  (UQAM Montréal, Canada)</div><div class="event_title">Using optimal transport to mitigate unfair predictions and quantify counterfactual fairness <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Many industries are heavily reliant on predictions of risks based on characteristics of potential customers. Although the use of said models is common, researchers have long pointed out that such practices perpetuate discrimination based on sensitive features such as gender or race. Given that such discrimination can often be attributed to historical data biases, an elimination or at least mitigation, is desirable. With the shift from more traditional models to machine-learning based predictions, calls for greater mitigation have grown anew, as simply excluding sensitive variables in the pricing process can be shown to be ineffective.  In the first part of this seminar, we propose to mitigate possible discrimination (related to so call «group fairness», related to discrepancies in score distributions) through the use of Wasserstein barycenters instead of simple scaling. To demonstrate the effects and effectiveness of the approach we employ it on real data and discuss its implications. This part will be based on recent work with François Hu and Philipp Ratz (2310.20508, 2309.06627, 2306.12912 and 2306.10155). In the second part, we will focus on another aspect of discrimination usually called « counterfactual fairness », where the goal is to quantify a potential discrimination « if that person had not been Black » or « if that person had not been a woman ». The standard approach, called «ceteris paribus» (everything remains unchanged) is not sufficient to take into account indirect discrimination, and therefore, we consider a « mutates mutants » approach based on optimal transport. With multiple features, optimal transport becomes more challenging, and we suggest a sequential approach based on probabilistic graphical models. This part will be based on recent work with Agathe Fernandes Machado and Ewen Gallic (2408.03425 and 2501.15549). </div><div class="event_time">11:00 &bull; EPF Lausanne, Extranef, 126</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.unige.ch/math/tggroup/doku.php?id=symplectic ">Geneva Neuchatel Symplectic Geometry Seminar (GeNeSyS)</a></div><br /><div class="event_speaker"> Marco Golla (Université de Nantes, CNRS)</div><div class="event_title">Alexander polynomials and symplectic curves in CP^2 <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Libgober defined the Alexander polynomial of a (complex) plane projective curve and showed that it detects some Zariski pairs ofcurves: these are curves with the same degree and the same singularities but with non-homeomorphic complements. He also proved that the Alexander polynomial of a curve divides the Alexander polynomial of its link at infinity and the product of Alexander polynomials of the links of its singularities. We extend Libgober\'s definition to the symplectic case and prove that the divisibility relations also hold in this context. This is joint work with Hanine Awada.</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_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"> Victorita Dolean</div><div class="event_title">Using Spectral Coarse Spaces of the H-Geneo Type for Efficient Solutions of the Helmholtz Equation <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The Helmholtz equation is a widely used model in wave propagation and scattering problems. However, its numerical solution can be computationally expensive in high-frequency regime due to the oscillatory solution and the potential contrasts in coefficients. Parallel domain decomposition methods have been identified as promising solvers for such problems, but they often require a suitable coarse space to achieve robust behaviour. In this talk, we present the H-GenEO coarse space, which constructs an effective coarse space using localized eigenvectors of the Helmholtz operator. Since the GenEO coarse space is designed for symmetric positive definite problems, the theory cannot be extended directly to the H-GenEO coarse space due to the indefinite nature of the underlying problem. During this talk it will be shown that the H-GenEO coarse space is capable of providing the required robust behaviour when used with a suitable domain decomposition method. Numerical experiments for increasing wave numbers demonstrate the efficiency of the method in solving complex Helmholtz problems, with potential applications in various scientific and engineering domains.</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_ne"><a class="external" href="https://unine.ch">Université de Neuchâtel</a></div><div class="event_type"><a class="external" href="https://www.unige.ch/math/tggroup/doku.php?id=symplectic ">Geneva Neuchatel Symplectic Geometry Seminar (GeNeSyS)</a></div><br /><div class="event_speaker"> Conan Leung (The Chinese University of Hong Kong)</div><div class="event_title">3d Mirror Symmetry is 2d Mirror Symmetry <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We introduce an approach to study 3d mirror symmetry via 2d mirror symmetry. The main observations are: (1) 3d brane transforms are given by SYZ-type transforms; (2) the exchange of symplectic and complex structures in 2d mirror symmetry induces the exchange of Kähler and equivariant parameters in 3d mirror symmetry; and (3) the functionalities of 2d mirror symmetry control the gluing of 3d mirrors.</div><div class="event_time">14:30 &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/analysis-seminar">Analysis Seminar</a></div><br /><div class="event_speaker">Prof. Dr. Frédéric  Hélein (Université Paris Diderot)</div><div class="event_title">Kaluza-Klein theories without a priori fibration hypotheses <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />I will present a Lagrangian action on fields, the critical points of which lead to solutions of the Einstein-Yang-Mills equations, in the spirit of Kaluza-Klein theories. The novelty is that the a priori fiber bundle structure hypothesis is not required: fields are defined on a "space-time" $Y$ of dimension $4+r$ without any a priori principal bundle structure, where $r$ is the dimension of the structure group. If the latter group is compact and simply connected, to each solution of the Euler-Lagrange equations it corresponds a 4-dimensional pseudo-Riemannian manifold $X$ (which can be interpreted as our usual space-time) in such a way that $Y$ acquires a principal bundle structure over $X$ equipped with a connection. Moreover the metric on $X$ and the connection on $Y$ are solutions of the Einstein-Yang-Mills system. If the structure group is $U(1)$ (the case which corresponds to the Einstein-Maxwell system) the situation is slightly degenerated and supplementary hypotheses are necessary.</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_ne"><a class="external" href="https://unine.ch">Université de Neuchâtel</a></div><div class="event_type"><a class="external" href="http://www.unine.ch/math/home/colloques_et_seminaires/les-colloques-du-mardi.html">Colloque du Mardi </a></div><br /><div class="event_speaker"> Sobhan Seyfaddini (ETH Zürich)</div><div class="event_title">Closing Lemmas on Symplectic Manifolds <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Given a diffeomorphism of a manifold, can one perturb it to create a periodic orbit passing through a specified region? This question, first raised in the 1960s, is known as the Closing Lemma. While the problem was resolved positively in C^1 regularity long ago, it remains largely open at higher levels of smoothness. Recent years have seen significant progress in the C^\\infty setting, particularly for area-preserving maps on surfaces. In this talk, I will review these developments, highlighting works by Asaoka, Irie, Cristofaro-Gardiner, Edtmair, Hutchings, Prasad, and Zhang. I will also present some recent joint work with Cineli & Tanny and Mak & Smith, including partial results in higher dimensions.</div><div class="event_time">16:00 &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://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">Samuel Koovely (Universität Zürich)</div><div class="event_title">What is... Free Convolution? <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We will start this talk by describing how to model heat diffusion on graphs and the relation between this model and the eigenvalues of random matrices, in particular Wigner\'s semicircle law. These considerations will lead us to discuss free probability theory at an introductory level, highlighting its similarities with standard probability theory.</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_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">Prof. Dr. Bastian Grossenbacher (Uni Fribourg)</div><div class="event_title">Shapes, Spaces, Simplices, and Structure: Geometry, Topology, and Machine Learning <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />A large driver contributing to the undeniable success of deep-learningmodels is their ability to synthesise task-specific features from data.For a long time, the predominant belief was that \'given enough data, allfeatures can be learned.\' However, as large language models are hittingdiminishing returns in output quality while requiring an ever-increasingamount of training data and compute, new approaches are required. Onepromising avenue involves focusing more on aspects of modelling, whichinvolves the development of novel *inductive biases* such as invariancesthat cannot be readily gleaned from the data. This approach isparticularly useful for data sets that model real-world phenomena, aswell as applications where data availability is scarce. Given their dualnature, geometry and topology provide a rich source of potentialinductive biases. In this talk, I will present novel advances inharnessing multi-scale geometrical-topological characteristics of data.A special focus will be given to show how geometry and topology canimprove representation learning tasks. Underscoring the generality ofa hybrid geometrical-topological perspective, I will furthermoreshowcase applications from a diverse set of data domains, includingpoint clouds, graphs, and higher-order combinatorial complexes.</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, 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"> Adam Kanigowski (University of Maryland)</div><div class="event_title">Sparse Equidistribution Problems in Dynamics</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_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">Prof. Dr. David Aulicino (Brooklyn College (CUNY))</div><div class="event_title">Siegel-Veech Constants of Cyclic Covers of Generic Translation Surfaces <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We consider generic translation surfaces of genus g&gt;0 with marked points and take covers branched over the marked points such that the monodromy of every element in the fundamental group lies in a cyclic group of order d. Given a translation surface, the number of cylinders with waist curve of length at most L grows like L^2. By work of Veech and Eskin-Masur, when normalizing the number of cylinders by L^2, the limit as L goes to infinity exists and the resulting number is called a Siegel-Veech constant. The same holds true if we weight the cylinders by their area. Remarkably, the Siegel-Veech constant resulting from counting cylinders weighted by area is independent of the number of branch points n. All necessary background will be given.  This is joint work with Aaron Calderon, Carlos Matheus, Nick Salter, and Martin Schmoll.</div><div class="event_time">13:30 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room E 33.1</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/daco-seminar">DACO Seminar</a></div><br /><div class="event_speaker">Dr. Pedro Abdalla Teixeira (UC Irvine, US)</div><div class="event_title">LLM Watermarking Using Mixtures and Statistical-to-Computational Gaps <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Given a text, can we determine whether it was generated by a large language model (LLM) or by a human? Watermarking is a prominent method used to address this question. In this talk, we will analyze two different watermarking settings from a statistical perspective, focusing in particular on how mixtures and statistical-to-computational gaps can be useful for watermarking. This is a joint work with Roman Vershynin.</div><div class="event_time">14:00 &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_ba"><a class="external" href="https://unibas.ch">Universität Basel</a></div><div class="event_type"><a class="external" href="https://dmi.unibas.ch/de/forschung/mathematik/zahlentheorie/">Seminar Zahlentheorie</a></div><br /><div class="event_speaker"> Yuri Zarhin (Penn State)</div><div class="event_title"><a class="external" href="https://dmi.unibas.ch/de/news-events/detail/number-theory-seminar-yuri-zarhin-penn-state/">Title T.B.A.</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Title: Torsion points of small order on cyclic covers of the projective line Abstract: We discuss generalizations of well-known properties of torsion points of order 3 on elliptic curves in characteristic 3 to the curves described in the title. This is a report on a joint work with Boris Bekker (St. Petersburg University). Spiegelgasse 1, Seminarraum 00.003</div><div class="event_time">14:15 &bull; Universität Basel</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ba"><a class="external" href="https://unibas.ch">Universität Basel</a></div><div class="event_type"><a class="external" href="https://dmi.unibas.ch/de/forschung/mathematik/analysis/analysis-seminar">Analysis Seminar</a></div><br /><div class="event_speaker"> Mattia Freguglia (Scuola Normale Superiore di Pisa)</div><div class="event_title"><a class="external" href="https://dmi.unibas.ch/de/news-events/detail/seminar-analysis-and-mathematical-physics-mattia-freguglia-scuola-normale-superiore-di-pisa/">A nonlocal approximation of the area functional in codimension two</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />In this seminar, we will introduce, for any $s\\in (0,1)$, a notion of s-fractional volume on closed, oriented, codimension-two surfaces in Euclidean space. We will then show that this quantity Gamma-converges, with respect to the flat distance, and converges pointwise to the codimension-two Hausdorff measure, as s goes to 1. In particular, we will see how this fractional volume can be interpreted as the codimension-two analogue of the well-established notion of fractional perimeter. If time permits, we will discuss a possible generalization of this definition to higher codimension, along with some (equi)compactness properties related to these fractional volumes. Based on a joint project with Michele Caselli and Nicola Picenni.</div><div class="event_time">14:15 &bull; Universität Basel, Spiegelgasse 5, Seminarraum 05.002</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/geometry-seminar">Geometry Seminar</a></div><br /><div class="event_speaker"> Hugo Parlier ( Université de Fribourg)</div><div class="event_title">Criss-crossing curves <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The crossing lemma for simple graphs gives a lower bound on the necessary number of crossings of any drawing of a graph in the plane in terms of its number of edges and vertices. Viewed through the lens of topology, this leads to other questions about arcs and curves on surfaces.In joint work with Alfredo Hubard, we provide estimates on the necessary number of intersections of any realization of <i>m</i> distinct homotopy classes of curves on a (fixed) surface. These estimates allow us to answer questions raised by Pach, Tardos, and Toth concerning a version of the crossing lemma for graph drawings with non-homotopic edges. Our approach uses the geometry of hyperbolic surfaces in an essential way.</div><div class="event_time">15:30 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_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"> Andrey    Pilipenko (Geneve University / Ukrainian National Academy of Sciences)</div><div class="event_title">Diffusions in a media with semipermeable membranes. <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Diffusions in a medium with semipermeable membranes naturally arise in models of material science, chemistry, biology, telecommunications, etc.  We will discuss them from the following points of view: (a) macroscopic, (b) stochastic, (c) PDE.</div><div class="event_time">16:00 &bull; EPF Lausanne, CM1 517</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"> Ting Lin (Peking University)</div><div class="event_title">Finite element form-valued forms: A unified construction <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We provide a finite element discretization of $\\ell$-form-valued $k$ form in $n$ dimensions for general $k$, $\\ell$ and $n$ and polynomial degree. The construction generalizes finite element Whitney forms for the de~Rham complex and their higher-order and distributional versions, the Regge finite elements and the Christiansen--Regge elasticity complex, the TDNNS element for symmetric stress tensors, the MCS element for traceless matrix fields, the Hellan--Herrmann--Johnson (HHJ) elements for biharmonic equations, and discrete divdiv and Hessian complexes in [Hu, Lin, and Zhang, 2025]. The construction discretizes the Bernstein--Gelfand--Gelfand (BGG) diagrams. Applications of the construction include discretization of strain and stress tensors in continuum mechanics and metric and curvature tensors in differential geometry in any dimension. This talk is based on a joint work with Kaibo Hu (Edinburgh).</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">Prof. Dr. Sylvie Méléard (Centre de Mathématiques Appliquées, Ecole Polytechnique)</div><div class="event_title">Long time asymptotics for critical birth and death diffusion processes <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />We study the long time behavior for the distribution of a critical birth and death diffusion process, motivated  by population dynamics in changing environment (cf. a recent paper by Calvez, Henry, Méléard, Tran). The birth rates are  bounded but  death rates  are unbounded. Our analysis is based on the spectral properties of the associated Feynman Kac semigroup. We  require a standard spectral gap property for this semigroup with a dominant eigenfunction vanishing at infinity.  Some examples of diffusions, diffusions with jump, pure jump dynamics are given for which it is true. We consider situations where the underlying diffusion process doesn\'t come down rapidly from infinity but the compactness properties follow from the divergence of the death rate at infinity. We prove the convergence in law of the branching diffusion process  suitably normalized and conditioned to non-extinction. We also prove the existence of the $Q$-process. The main tool is the convergence of suitably normalized moments of  the process, which follows from recursive relations for these moments. This is a joint work with Pierre Collet and Jaime San Martin.</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, May 8      </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://sites.google.com/view/pm-seminar/home">Physical Mathematics Seminar</a></div><br /><div class="event_speaker"> Diksha  Jain  (University of Cambridge)</div><div class="event_title">Supersymmetric Grey Galaxies, Dual Dressed Black Holes and the Superconformal Index <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Motivated by the recent construction of grey galaxy and Dual Dressed Black Hole solutions in AdS5 Å~ S5, in this talk, I will present a conjecture relating to the large N entropy of supersymmetric states in N=4 Yang-Mills theory. We conjecture the existence of a large number of supersymmetric states which can be thought of as a non-interacting mix of supersymmetric black holes and supersymmetric `gravitons\'. It predicts a microcanonical phase diagram of supersymmetric states and makes a sharp prediction for the supersymmetricentropy (as a function of 5 charges) in each phase. We also predict a large N formula for the superconformal index as a function of indicial charges and predict a microcanonical indicial phase diagram with nine distinct phases. It predicts agreement between the superconformal index and black hole entropy in one phase (so over one range of charges), but disagreement in other phases (and so at other values of charges).</div><div class="event_time">13:00 &bull; <a class="external" href="https://cern.zoom.us/j/65703510284?pwd=nrC7OwTZanEUQGzxEpQunNPbPMiP6A.1">Université de Genève</a></div>        </div>        <div class="day_content_item normal"><div class="event_location uni_ba"><a class="external" href="https://unibas.ch">Universität Basel</a></div><div class="event_type"><a class="external" href="https://dmi.unibas.ch/de/forschung/mathematik/zahlentheorie/">Seminar Zahlentheorie</a></div><br /><div class="event_speaker"> Vaidehee Thatte (King\'s College London)</div><div class="event_title"><a class="external" href="https://dmi.unibas.ch/de/news-events/detail/number-theory-seminar-vaidehee-thatte-kings-college-london/">Title T.B.A.</a> <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Title: Ramification Theory for Henselian Valued Fields Abstract: Ramification theory serves the dual purpose of a diagnostic tool and treatment by helping us locate, measure, and treat the anomalous behaviour of mathematical objects. In the classical setup, the degree of a finite Galois extension of "nice" fields splits up neatly into the product of two well-understood numbers (ramification index and inertia degree) that encode how the base field changes. In the general case, however, a third factor called the defect (or ramification deficiency) can pop up. The defect is a mysterious phenomenon and the main obstruction to several long-standing open problems, such as obtaining resolution of singularities. The primary reason is, roughly speaking, that the classical strategy of "objects become nicer after finitely many adjustments" fails when the defect is non-trivial. I will discuss my previous and ongoing work in ramification theory in this setting; in particular, it allows us to understand and treat the defect. Background in ramification theory or valuation theory is not assumed. Spiegelgasse 5, Seminarraum 05.002</div><div class="event_time">14:15 &bull; Universität Basel</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"> Toby Dylan Hocking  (Université de Sherbrooke, Canada)</div><div class="event_title">Using and contributing to the data.table package for efficient big data analysis <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />data.table is an R package with C code that is one of themost efficient open-source in-memory database packages availabletoday. First released to CRAN by Matt Dowle in 2006, it continues togrow in popularity, and now over 1500 other CRAN packages depend ondata.table. This talk will discuss basic and advanced datamanipulation topics, and end with a discussion about how you cancontribute to data.table.</div><div class="event_time">15:15 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://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. Christian Brennecke (Universität Bonn)</div><div class="event_title">Operator Norm Bounds on the Correlation Matrix of the SK Model <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 discuss basic predictions for the replica symmetric regime of the Sherrington-Kirkpatrick spin glass model. For the model without external field, Talagrand conjectured that at high temperature the two point correlation matrix has operator norm that is bounded uniformly in the system size $N$. Based on suitable Schatten norm estimates, he was able to show that the operator norm grows at most logarithmically in $N$. I will present a different strategy that is based on ideas related to the TAP approach and that enables an exact computation of the operator norm as $N\\to\\infty$, valid in the full high temperature regime. I will conclude the talk with some related open questions for the SK model with non-zero external field. The talk is based on joint work with A. Schertzer, C. Xu and H.-T. Yau.</div><div class="event_time">16:15 &bull; UZH Irchel, Winterthurerstrasse 190, Z&uuml;rich, Building Y27, Room H 46</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. Jennifer Alonso-Garcia (Université Libre de Bruxelles)</div><div class="event_title">Variable annuities: a closer look at ratchet guarantees, hybrid contract designs, and taxation <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Recently, providers of variable annuity (VA) contracts have launched products which offer potentially higher guaranteed benefits through a ratcheting mechanism in conjunction with an array of investment options, including a cash fund. In some contract designs, the cash fund serves as an intermediate repository of earnings. For example, in a VA with a guaranteed minimum withdrawal benefit (GMWB), the policyholder has the option to withdraw less than the guaranteed withdrawal amount, with the difference being deposited into the cash fund, which appreciates at a benchmarked rate until the contract matures. We consider the valuation of a VA contract with a GMWB rider in which the policyholder has access to a cash fund. Assuming a ratcheting mechanism for the guarantee, we determine the optimal withdrawal strategy and provide numerical examples of cash flows emanating from the contract. We also investigate the implications of taxation on the value of the VA contract.</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 9      </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"> Boris Bukh (Carnegie Mellon University)</div><div class="event_title">Discrete Geometry</div><div class="event_time">10:15 &bull; ETH Zentrum, R&auml;mistrasse 101, Z&uuml;rich, Building HG, Room G 43</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_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"> Lyonell  Boulton (Heriot-Watt University)</div><div class="event_title">Jumps, cusps and fractals in time-evolution models <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />The phenomenon of revivals in linear dispersive equations was discovered first experimentally in optics, in around 1834, then rediscovered several times by theoretical and experimental investigations. While the concept has been used systematically and consistently by many authors, there is no consensus on a rigorous definition.Several have described it by stating that a given periodic time-dependent boundaryvalue problem exhibits revivals at rational times, if the solution evaluated at a certain dense subset of times, is given by finite superpositions of translated copies of the initial condition. When this initial condition has jump discontinuities at time zero, these discontinuities are propagated and remain present in the solution at each rational time.The complementary phenomenon to revivals is fractalisation. One instance of this is that, for initial conditions with jump discontinuities, the solution is continuous in space for every irrational time, but its graph is a curve of high fractal dimension.In this talk I will report on the presence of revivals and fractalisation, defined in the context of spectral theory, for three models of parabolic differential equations.Nonlocal equations that arise in water wave theory and are defined by convolution kernels [1] and [5].Schrödinger equations with different types of boundary conditions [2] or with complex potentials [3].Indefinite Laplacian time-evolution equations [4].This research has been conducted jointly with George Farmakis (London South Bank University), Peter Olver (University of Minnesota), Beatrice Pelloni (Heriot-Watt University) and David Smith (Newcastle University).References[1] Stud. Appl. Math. 147 (2021) p.1209.[2] Proc. Royal Soc. A. 477 (2021) p.2251.[3] Z. Anal. Anwend. 43 (2024) p.401.[4] Preprint ArXiV:2403.01117.[5] Preprint ArXiV:2501.01322.</div><div class="event_time">14:15 &bull; EPF Lausanne, AAC 0 14</div>        </div>        <div class="day_content_item normal"><div class="event_location uni_zh"><a class="external" href="https://ethz.ch">ETH Z&uuml;rich</a></div><div class="event_type"><a class="external" href="https://math.ethz.ch/s/number-theory-seminar">Number Theory Seminar</a></div><br /><div class="event_speaker">Dr. Gabriel  Ribeiro (ETH Zurich)</div><div class="event_title">On a duality theory for commutative group stacks <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />Aiming to unify the construction of the dual abelian variety with the Cartier duality of algebraic tori, one is naturally led to a duality theory for commutative group stacks. This construction was first considered by Laumon, and it led to the proof of geometric Langlands for tori. In this talk, I will present a conceptual construction of this duality and highlight intriguing phenomena that emerge—in particular, the dual of the additive group turns out to be a rather mysterious object. This is joint work with Zev Rosengarten.</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://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"> Javier  Fresan  (Institut de mathématiques de Jussieu)</div><div class="event_title">On G-functions of differential order 2 <span class="abstract-button do_not_print">abstract</span></div><div class="abstract-text" style="display: none"><strong>Abstract:</strong><br />G-functions are power series that solve a linear differential equation and satisfy some growth conditions of arithmetic nature. Those which are solution of a differential equation of order 1 are algebraic of a rather particular shape. A rich family of G-functions of differential order 2 is given by algebraic substitutions of the classical Gauss hypergeometric series. However, I will argue that G-functions of order 2 are infinitely much richer than those. Indeed, there exist infinitely many non-equivalent differential equations of order 2 whose solutions include a G-function that is not a polynomial in algebraic substitutions of hypergeometric series. This solves Siegel\'s problem for G-functions, as formulated by Fischler and Rivoal, and answers a question of Krammer in connection to his counterexample to a conjecture by Dwork. (Joint work with Josh Lam and Yichen Qin)</div><div class="event_time">14:15 &bull; EPF Lausanne, GA 3 21</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>';