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--- shared:seminars_graphs [01.09.2019 10:39]
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+++ shared:seminars_graphs [09.11.2025 21:30] (текущий)
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 ====Спецсеминар "Графы на поверхностях и кривые над числовыми полями"====
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-**Семинар проходит по средам в ауд. 14-15 Главного здания, начало в 18:30.**
 ----
+**Семинар Георгия Борисовича Шабата регулярно работает с сентября 1991г. Обычно проходит по средам в ауд. 14-05 Главного здания. В настоящее время проводится частично он-лайн, с использованием технологии Zoom, начало в 18:30.** Программа семинара появляется также на нашей страничке на [[http://www.mathnet.ru/php/conference.phtml?option_lang=rus&eventID=12&confid=1881|Math-Net]]. Следите за обновлениями!
 ----
-**04.09.2019** ВНИМАНИЕ: начало в 18:00
+Для участия в он-лайн семинаре напишите elena -dot- kreines @ gmail -dot- com
-. Pálfia Miklós, On the recent advances in the multivariable theory
+**19.11.2025**
-of operator monotone functions and means
-Functional Analysis Research Group, Institute of Mathematics,
-University of Szeged, Hungary,
-Sungkyunkwan University, Korea
-Abstract:
+Sergey Fomin  (University of Michigan), Incidence geometry and tiled surfaces
-The origins of this talk go back to the fundamental theorem of Loewner
-in 1934 on operator monotone real functions and also to
-the hyperbolic geometry of positive matrices. Loewner's theorem
-characterizing one variable operator monotone functions has been
-very influential in matrix analysis and operator theory. Among others
-it lead to the Kubo-Ando theory of two-variable operator means
-of positive operators in 1980. One of the nontrivial means of the
-Kubo-Ando theory is the non-commutative generalization of the
-geometric mean which is intimately related to the hyperbolic,
-non-positively curved Riemannian structure of positive matrices.
-This geometry provides a key tool to define multivariable
-generalizations of two-variable operator means. Arguably the most
-important
-example of them all is the Karcher mean which is the center of mass on
-this manifold. This formulation enables us to define this mean
-for probability measures on the cone of positive definite matrices
-extending further the multivariable case. Even the infinite
-dimensional
-case of positive operators is tractable by abandoning the Riemannian
-structure in favor of a Banach-Finsler structure provided by
-Thompson's part metric on the cone of positive definite operators.
-This metric enables us to develop a general theory of means of
-probability measures defined as unique solutions of nonlinear operator
-equations on the cone, with the help of contractive semigroups
-of nonlinear operators. We also introduce the recently established
-structure theory of multivariable operator monotone functions
-extending the classical result
-of Loewner into the non-commutative multivariable realm of free
-functions, providing theoretically explicit closed formulas for our
-multivariable
-operator means.
-. F. Pakovich, COMMUTING RATIONAL FUNCTIONS REVISITED
+We show that various classical theorems of linear incidence geometry, such as the theorems of Pappus, Desargues, Möbius, and so on, can be interpreted as special cases of a general result that involves a tiling of a closed oriented surface by quadrilateral tiles. This yields a general mechanism for producing new incidence theorems and generalizing and interpreting the known ones.
-Ben Gurion University, Israel
-Abstract
+**12.11.2025**
-Let A and B be rational functions on the Riemann sphere. The classical
-Ritt theorem states that if A and B commute and do not have an iterate
+Н.М. Адрианов, (2,3)-рисунки, малые семейства Фрида и инвариант хамелеона
-in common, then up to a conjugacy they are either powers, or Chebyshev
-polynomials, or Latt`es maps. This result however provides no
+**05.11.2025**
-information about commuting rational functions which do have a common
-iterate. On the other hand, non-trivial examples of such functions
+Katie Waddle (University of Michigan), Spherical friezes
-exist and were constructed already by Ritt. In the talk we present new
-results concerning this class of commuting rational functions. In
+A fundamental problem in spherical distance geometry aims to recover an $n$-tuple of points on a 2-sphere in $\mathbb{R}^3$, viewed up to oriented isometry, from $O(n)$ input measurements. This talk will discuss an algebraic solution using only the four arithmetic operations. We will show how a new type of frieze pattern can be employed to arrange the measurement data. These friezes exhibit glide symmetry and a version of the Laurent phenomenon.
-particular, we describe a method which permits to describe all
-rational functions commuting with a given rational function.
+**15.10.2025**
+. Наталья Амбург, Пенлеве VI и детские рисунки.
+Я поделюсь своими скромными  размышлениями по  поводу алгебраических  решений Пенлеве VI. По мотивам курсовой работы Анны Михайловой расскажу о рисунках для решений 13 и 14.
+. Разное.
+**08.10.2025**
+George Shabat, Three versions of dessins d'enfants theory
+The three versions of dessins d'enfants, corresponding to the general, clean and very clean Belyi pairs, will be presented. The standards for drawing and painting of these pairs will be suggested and their ubiformizations discussed. The relation between the theories will be presented and examples given.
+**01.10.2025**
+. А. Юран,  Дискриминант четырёхчлена с симметричным носителем
+Аннотация: Мы вычислим дискриминант многочлена f(x)=a+bx^k+cx^l+dx^{k+l} (где a,b,c,d комплексные, k,l -- натуральные) и обсудим, как он связан с детскими рисунками на сфере, в которых одна вершина степени 3, одна вершина степени 1, а остальные имеют степень 2.
+. Разное
+**24.09.2025**
+. Г.Б. Шабат, Граф К5 и поле из 5 элементов (продолжение)
+. Разное
+**10.09.2025**
+. Г.Б. Шабат, Граф К5 и поле из 5 элементов
+. Разное
+----
+**[[[[:seminars_graphs_references|Полезные ссылки и другие ресурсы нашего семинара]]**
 **Архив**
+[[[[:seminars_graphs_24_25|2024 - 2025 учебный год]]
+[[[[:seminars_graphs_23_24|2023 - 2024 учебный год]]
+[[[[:seminars_graphs_22_23|2022 - 2023 учебный год]]
+[[[[:seminars_graphs_21_22|2021 - 2022 учебный год]]
+[[[[:seminars_graphs_20_21|2020 - 2021 учебный год]]
+[[[[:seminars_graphs_19_20|2019 - 2020 учебный год]]
 [[[[:seminars_graphs_18_19|2018 - 2019 учебный год]]