Différences

Ci-dessous, les différences entre deux révisions de la page.

--- fables [2020/01/12 23:23] – weronika
+++ fables [2023/02/28 16:53] – kalinin0
@@ Ligne 1: / Ligne 1: @@
 ====== Séminaire "Fables Géométriques". ======
-The normal starting time of this seminar is 16.30 on Monday.
+----
+  Monday, March 6, 2023
+  room 6-13
+**15h00 — Ali Ulaş Özgür Kişisel**
+**Expected measures of amoebas of random plane curves**
+There are several natural measures that one can place on the amoeba of an algebraic curve in the complex projective plane. Passare and Rullgård prove that the total mass of the Lebesgue measure on the amoeba of a degree $d$ curve is bounded above by $π^2 d^2 / 2$, by comparing it to another Monge-Ampère type measure, which is dual to the usual measure on the Newton polytope of the defining polynomial via the Legendre transform. Mikhalkin generalizes this upper bound to half-dimensional complete intersections in higher dimensions, by considering another measure supported on their amoebas; their multivolume. The goal of this talk will be to discuss these measures in the setting of random plane curves. In particular, I’ll first present our results with Bayraktar, showing that the expected multiarea of the amoeba of a random Kostlan degree $d$ curve is equal to $π^2 d$. For Lebesgue measure, it turns out that the expected asymptotics are much lower: I’ll describe our results with Welschinger, showing that the expected Lebesgue area of the amoeba of a random Kostlan degree $d$ curve is of the order $(\log d)^2$.
+----
+  Monday, February 27, 2023
+  room 6-13
+**15h00 — Evgeni Abakoumov (Paris/Eiffel U)**
+**Chui's conjecture аnd rational approximation**
+C. K. Chui conjectured in 1971 that the average gravitaional field strength in the unit disk due to unit point masses on its boundary was the smallest when these point masses were equidistributed on the circle. We will present an elementary solution to some weighted versions of this problem, and discuss related questions concerning approximation of holomorphic functions by simple partial fractions. This is joint work with A. Borichev and K. Fedorovskiy.
+**16h00 — Ferit Ozturk (Istanbul/Bosphorus U and Budapest/Renyi Inst)**
+**Every real 3-manifold admits a real contact structure**
+We survey our results regarding real contact 3-manifolds and present our result in the title.
+A real 3-manifold is a smooth 3-manifold together with an orientation preserving smooth involution, called a real structure.
+A real contact 3-manifold is a real 3-manifold with a contact distribution that is antisymmetric with respect to the real structure.
+The standard examples of real contact 3-manifolds are link manifolds of isolated, real analytic surface singularities.
+We show that every real contact 3-manifold can be obtained via contact surgery along invariant knots starting from the standard real contact 3-sphere.
+As a corollary we show that any oriented overtwisted contact structure on an integer homology real 3-sphere can be isotoped to be real.
+----
+  Monday, February 6, 2023
+:00, room 6-13
+**Sergey Finashin (Ankara)**
+**“Affine Real Cubic Surfaces”**
+Abstract: (A joint work with V.Kharlamov) We prove that the space of
+affine, transversal at infinity, non-singular real cubic surfaces has 15 connected components. We give a topological criterion to distinguish them and show also how these 15 components are adjacent to each other via wall-crossing.
+----
+  Thursday, June 16, 2022
+:00, room 1-07
+**Prof.  Yakov Eliashberg (Stanford)**
+**“Topology of spaces of Legendrian knots via Algebraic K-theory”**
+Abstract: The highly non-trivial stable homotopy groups of the Waldhausen’s
+h-cobordism space inject into the homotopy groups of spaces of appropriate Legendrian submanifolds. For instance,  there is  a  homotopically non-trivial 2-parametric family of Legendrian unknots in ${\mathbb R}^{2n+1}$ for a sufficiently large $n$. This is a joint work with Thomas Kragh.
+----
+  Fri 17.12.2021, 13h30, room 6-13
+  Andras Szenes
+**Diagonal bases and wall-crossings in moduli spaces of vector bundle**
+The idea  of the calculation of the Hilbert function of the moduli spaces of vector bundles on Riemann surfaces goes back to the works of Michael Thaddeus in the early 90’s.
+I describe joint work with Olga Trapeznikova where this plan is carried out in detail, which uses only basic tools of Geometric Invariant Theory and a combinatorial/analytic device introduced by myself: the diagonal basis of hyperplane arrangements.
+----
+  Nov 1, 16h15. Room 06-13
+  Vasily Golyshev (Moscow, Bures-sur-Yvette)
+**Markov numbers in number theory, topology, algebraic geometry, and differential equations**
+I will explain how the Markov numbers arise in different mathematical
+disciplines, and sketch the links. A recent contribution will be discussed, too.
+----
+, Wednesday, May 20, 16:00 (CEST), Virtual seminar, Lionel Lang (Stockholm University)
+https://unige.zoom.us/j/5928729514
+Meeting ID: 592 872 9514  Password: (the number of lines on a cubic surface)
+**Co-amoebas, dimers and vanishing cycles**
+In this joint work in progress with J. Forsgård, we study the topology of maps P:(\C*)^2 \to \C given by Laurent polynomials P(z,w).
+For specific P, we observed that the topology of the corresponding map can be described in terms of the co-amoeba of a generic fiber. When the latter co-amoeba is maximal, it contains a dimer (a particularly nice graph) whose fundamental cycles corresponds to the vanishing cycles of the map P. For general P, the existence of maximal co-amoebas is widely open. In the meantime, we can bypass co-amoebas, going directly to dimers using a construction of Goncharov-Kenyon and obtain a virtual correspondence between fundamental cycles and vanishing cycles.
+In this talk, we will discuss how this (virtual) correspondence can be used to compute the monodromy of the map P.
+----
+, Tuesday, April 7, 17:00, Virtual seminar (EDGE seminar) Grigory Mikhalkin (Geneva)
+https://zoom.us/j/870554816?pwd=bERmR0ZQTitYNXJ1aFZLckxzeXZJZz09
+Meeting ID: 870 554 816 Password: 014504
+**Area in real K3-surfaces**
+Real locus of a K3-surfaces is a multicomponent topological surface. The canonical class provides an area form on these components (well defined up to multiplication by a scalar). In the talk we'll explore inequalities on total areas of different components as well a link between such inequalities and a class of real algebraic curves called simple Harnack curves. Based on a joint work with Ilia Itenberg.
+----
+, Monday, March 31, 17:00, Virtual seminar, Vladimir Fock (Strasbourg)
+https://unige.zoom.us/j/737573471
+Meeting ID: 737 573 471
+**Higher measured laminations and tropical curves**
+We shall define a notion of a higher lamination - a graph embedded
+into a Riemann surface with edges coloured by generators of an affine
+Weyl group. This notion generalises the notion of the ordinary
+integral measured lamination and on the other hand of a tropical
+curve and can be constructed out of a integral Lagrangian submanifold
+of the cotangent bundle.
+----
+, Monday, March 16, 16:30, Battelle, Alexander Veselov (Loughborough University)[POSTPONED]
+**On integrability, geometrization and knots**
+I will start with a short review of Liouville integrability in relation with Thurston’s geometrization programme,
+using as the main example the geodesic flows on the 3-folds with SL(2,R)-geometry.
+A particular case of such 3-folds the modular quotient SL(2,R)/SL(2,Z), which is known, after Quillen, to be equivalent to the complement in 3-sphere of the trefoil knot. I will show that remarkable results of Ghys about modular and Lorenz knots can be naturally extended to the integrable region, where these knots are replaced by the cable knots of trefoil.
+The talk is partly based on a recent joint work with Alexey Bolsinov and Yiru Ye.
+----
 , Monday, February 17, 16:30, Battelle, Karim Adiprasito