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Beijing-Moscow Mathematics Colloquium

Description

Organizing committee of Beijing-Moscow Mathematics Colloquium  

 

(1) Huijun Fan (SMS PKU, symplectic geometry and mathematical physics, geometric analysis)

(2) Sergey Gorchinskiy (MI RAS, algebra and geometry: algebraic geometry, K-theory)

(3) Hailiang Li (SMS CNU, fluid mechanics, partial differential equations, analysis)

(4) Jinsong Liu (AMSS, algebraic geometry: singularity theory)

(5) Yi Liu (BICMR, Topology of 3-manifolds, hyperbolic geometry)

(6) Denis Osipov (MI RAS, algebraic geometry, number theory, integrable system)

(7) Ye Tian (UCAS, AMSS, Number Theory, Arithmetic Geometry, Iwasawa Theory)

(8) Alexey Tuzhlin (MSU, geometry: Riemannian and metric geometry)

(9) Yue Yang (CE PKU, computation mathematics and mechanics)

(10) Ping Zhang (AMSS, P. D. E.: fluid equation and semi-classical analysis)

(11) Alexander Zheglov (MSU, geometry: algebraic geometry, integrable system)

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The lecture announcements will be continually updated. The arrangement of the upcoming lectures is as follows:

 

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Lecture Series 37 —— June 10, 2022 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/53480B83434362AFD4CB41F2AAB7FF7D
Valid Until: 2026-07-31 23:59

 

Lecture 1——Some topics in quantum control

Speaker: Prof. Alexander Pechen (Steklov Mathematical Institute of RAS)

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: Quantum control, that is control of individual quantum systems, attracts now high attention both due to fundamental interest and various existing and prospective applications in quantum technologies. In practical applications, controlled systems typically interact with the external environment, so that they are open quantum systems. We will discuss incoherent control of open quantum systems which uses spectral density of the environment as a tool to manipulate the system's dynamics, including a recent analysis of controllability and finding of unreachable sets of states for a qubit interacting with the environment. The controllability of controlled system is the first main question which should be answered. The next question is how difficult or easy to find optimal controls. This question is related to the analysis of quantum control landscapes. We will discuss various results on the analysis of quantum control landscapes, including a recent finding of trap-free behavior for single qubit phase-shift gate generation. In the context of gradient optimization for quantum technologies, we will discuss a convenient parametrization of quantum channels by points of the complex Stiefel manifold. Another topic is the control by measurements, including by back-action of non-selective measurements and feedback control, with possible applications to energy transfer in quantum photosynthesis.

Bio: Alexander Pechen is a Professor of the Russian Academy of Sciences. He is the head of the Department of Mathematical Methods for Quantum Technologies at Steklov Mathematical Institute of the Russian Academy of Sciences. He graduated from the Physical Department of Moscow State University in 2001. He obtained Ph.D. degree in Mathematical Physics from Steklov Mathematical Institute in 2004. From 2005 to 2010, he worked at Princeton University. Alexander Pechen is a laureate of the Blavatnik Award for Young Scientists (USA, 2009), and the Award of the Moscow Government for Young Scientists in Mathematics, Mechanics, and Informatics for "outstanding results in the theory of quantum control" (2013). His research interests include diverse topics in mathematics of quantum technologies, dynamics and control of quantum systems.

 

Lecture 2——On stochastic PDE control

Speaker: Prof. Xu Zhang (Sichuan University)

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: In this talk, I will give a short introduction to control theory for stochastic distributed parameter systems (governed by stochastic differential equations in infinite dimensions, typically by stochastic PDEs). I will explain the new phenomena and difficulties in the study of controllability and optimal control problems for these sorts of equations. In particular, I will show by some examples that both the formulation of corresponding stochastic control problems and the tools to solve them may differ considerably from their deterministic/finite-dimensional counterparts, and one has to develop new methods,  say, the stochastic transposition method introduced in our previous works, to solve some problems in this field.

Bio: Xu Zhang is a professor at the School of Mathematics, Sichuan University, Chengdu, China. He was an invited speaker at ICM (Control Theory & Optimization Section, 2010). He is/was the editor in chief/corresponding editor/associate editor for several journals including Mathematical Control and Related Fields, ESAIM: Control, Optimisation and Calculus of Variations, SIAM Journal on Control and Optimization, Annual Reviews in Control, etc. His research interests include mathematical control theory, related partial differential equations and stochastic analysis.

Slides: /pub/zesxzx2021/docs/20220613165040978280.pdf

 

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Lecture Series 36 —— May 27, 2022 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/297EE2DDEAF407BA14690A9EC8850B8E
Valid Until: 2026-06-30 23:59

 

Lecture 1——Product structure and regularity theorem for totally nonnegative flag varieties

Speaker: Xuhua He (CUHK)

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: The totally nonnegative flag variety was introduced by Lusztig. It has enriched combinatorial, geometric, and Lie-theoretic structures. In this talk, we introduce a (new) $J$-total positivity on the full flag variety of an arbitrary Kac-Moody group, generalizing the (ordinary) total positivity.

We show that the $J$-totally nonnegative flag variety has a cellular decomposition into totally positive $J$-Richardson varieties. Moreover, each totally positive $J$-Richardson variety admits a favorable decomposition, called a product structure. Combined with the generalized Poincare conjecture, we prove that the closure of each totally positive $J$-Richardson variety is a regular CW complex homeomorphic to a closed ball. Moreover, the $J$-total positivity on the full flag provides a model for the (ordinary) totally nonnegative partial flag variety. Combined with the generalized Poincare conjecture established by Smale, Freedman and Perelman, we prove that the closure of each (ordinary) totally positive Richardson variety is a regular CW complex homeomorphic to a closed ball, confirming conjectures of Galashin, Karp and Lam.

This talk is based on a joint work with Huanchen Bao.

Bio: Dr. Xuhua He is currently the Choh-Ming Li Professor of Mathematics at the Chinese University of Hong Kong (CUHK).  Prof. He received his B.S. degree in mathematics from Peking University in 2001, and Ph.D. degree from Massachusetts Institute of Technology in 2005. Before joining CUHK, he used to work at the State University of New York at Stony Brook (2006-2008), Hong Kong University of Science and Technology (2008-2014), and the University of Maryland (2014-2019). Moreover, he was a von Neumann Fellow at the Institute for Advanced Study for the academic year 2016–2017, and a Simons Visiting Professor at the Université Sorbonne Paris Nord (Paris 13 University) in 2017. For his outstanding achievements in the fields of algebraic groups, representation theory, and arithmetic geometry, he was an invited speaker at the ICM (2018) and was awarded the Morningside Gold Medal of Mathematics in 2013 and the AMS Chevalley Prize in Lie Theory in 2022.

 

Lecture 2——Group varieties and group structures

Speaker: Vladimir Popov (Steklov Mathematical Institute of RAS)

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: Since group operations of algebraic groups agree with the structure of their underlying varieties, there must be a dependence between them. A striking illustration of it is the classical theorem about commutativity of every connected algebraic group whose group variety is complete. In an explicit or implicit form, this problem was considered in the classical papers of A. Weil, C. Chevalley, A. Borel, A. Grothendieck, M. Rosenlicht, M. Lazard. This talk is aimed to discuss to what extent the group variety of a connected algebraic group or the group manifold of a connected real Lie group determines its group structure.

Bio: Prof. Vladimir Popov is a Chief Scientific Researcher at Steklov Mathematical Institute of RAS. He is a Corresponding Member of the Russian Academy of Sciences. His research interests include algebraic transformation groups, invariant theory, algebraic groups, Lie groups, Lie algebras and their representations, algebraic geometry, automorphism groups of algebraic varieties, and discrete reflection groups.

 

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Lecture Series 35 —— May 13, 2022 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/C48549B953F682393E90162B22FBE108
Valid Until: 2026-06-30 23:59

 

Lecture 1——Evolution of the spatial heterogeneity of metallic glasses and its correlation with the macroscopic visco-plasticity

Speaker: Xiaoding Wei (College of Engineering, Peking University)

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: Amorphous alloys (also known as metallic glasses) have no long-range order as crystalline counterparts, thus lacking traditional defects such as dislocations and grain boundaries to facilitate plastic deformation and strain hardening mechanisms. Instead, they have intrinsic hierarchical spatial heterogeneity inherited from the material preparation processes. More importantly, this spatial heterogeneity evolves with temperature and stress fields. In this study, we propose a chemo-mechanical constitutive law for metallic glasses that can describe the evolution of their spatial heterogeneity and establish the connection between this evolution with the macroscopic plastic deformation. Furthermore, our constitutive law reveals the underlying micro-mechanisms of metallic glasses under creep, relaxation, and fatigue.

Bio: Dr. Xiaoding Wei received his B.S. degree from the Department of Modern Mechanics at the University of Science and Technology of China in 2003, and Ph.D. degree from the Department of Mechanical Engineering at Columbia University in 2009. Then, Dr. Wei worked as a postdoc researcher at Northwestern University until he joined the department of Mechanics and Engineering Science at Peking University in 2016. His research interests include the fundamental mechanics of low-dimensional materials, crystalline and amorphous metals, and bio-inspired materials. His achievements include measuring the intrinsic strength of monolayer graphene for the first time in the world. Dr. Wei has published 55 peer-reviewed papers in Science, Nature Communications, Journal of the Mechanics and Physics of Solids, etc.

 

Lecture 2——Stability of the aneurysm in a membrane tube with localized wall thinning filled with a fluid with a non-constant velocity profile

Speaker:  Andrej Il'ichev (Steklov Mathematical Institute of RAS)

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: We perform the stability analysis of bulging localized structures on the wall of a fluid-filled axisymmetric membrane elastic tube. The wall of the tube is assumed to be subjected to localized thinning. The problem has no translational invariance anymore, hence the stability of a bulging wave centered in the point of the localization of imperfection is essential, and not orbital stability up to a shift as in the case of translationally invariant governing equations. Localized bulging motionless wave solutions of the governing equations are called aneurysm solutions. We assume that the fluid is subjected to the power law for viscous friction of a non-Newtonian fluid, though the viscosity of the fluid does not play a significant role and can be neglected. The velocity profile remains not constant along the cross section of the tube (even in the absence of the viscosity) because no-slip boundary conditions are performed on the tube walls. Stability is established by demonstrating the non-existence of the unstable eigenvalues of the linearized problem with a positive real part. This is achieved by constructing the Evans function depending only on the spectral parameter, analytic in the right half of the complex plane Ω+ and which zeroes in Ω+ coincide with the unstable eigenvalues of the problem. The non-existence of the zeroes of the Evans function is performed using the argument principle from the analysis of complex variables. Finally, we discuss the possibility of applying the results of the present analysis to the aneurysm formation in damaged human vessels under the action of internal pressure.

Bio: Professor Andrej Il'ichev is currently a Leading Scientific Researcher at Steklov Mathematical Institute of RAS and a Professor at Bauman Moscow State Technical University. He graduated from the Faculty of Mechanics and Mathematics of Lomonosov Moscow State University in 1981 and got his Ph.D. degree there in 1986. In 1996, he became Doctor of Sciences. Professor Il'ichev’s research field includes nonlinear waves, dissipative and dispersive systems, Hamiltonian systems, dynamical stability of bound states, solitary waves, and qualitative theory of differential equations. Also, he has published more than 100 papers and 3 monographs.

 

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Lecture Series 34 —— April 29, 2022 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/21483613E7EBAD10312B51853959F8A0
Valid Until: 2026-06-30 23:59

 

Lecture 1——Finiteness problem for hyper-Kähler varieties

Speaker: Zhiyuan Li

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: The classical Shafarevich conjecture is about the finiteness of isomorphism classes of curves of given genus defined over a number field with good reduction outside a finite collection of places. It plays an important role in Falting’s proof of the Mordell conjecture. Similar finiteness problems arise for higher dimensional varieties. In this talk, I will talk about finiteness problems for hyper-Kähler varieties in arithmetic geometry. This includes the unpolarized Shafarevich conjecture for hyper-Kähler varieties the cohomological generalization of the Shafarevich conjecture by replacing the good reduction condition with the unramifiedness of the cohomology. I will also explain how to generalize Orr and Skorobogatov’s finiteness result on K3 surfaces to hyper-Kähler varieties, i.e. the finiteness of geometric isomorphism classes of hyper-Kähler varieties of CM type in a given deformation type defined over a number field with bounded degree. This is a joint work with Lie Fu, Teppei Takamatsu and Haitao Zou.

Bio: Zhiyuan Li is an associated professor at Shanghai Center for Mathematical Sciences. His research interests are algebraic geometry and arithmetic geometry.

 

Lecture 2——Automorphisms of algebraic surfaces

Speaker: Сonstantin Shramov (Steklov Mathematical Institute of RAS)

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: I will discuss boundedness properties for finite subgroups in the groups of (birational) automorphisms of algebraic surfaces. The main focus will be on the Jordan property of such groups and its analogs suitable for fields of positive characteristics.

Bio: Constantin Shramov is a Leading Scientific Researcher at the Department of Algebraic Geometry of the Steklov Mathematical Institute of the Russian Academy of Sciences. His research interests are algebraic geometry, especially birational geometry.

 

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Lecture Series 33 —— April 15, 2022 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/A9CD1CB87FAFA66E664594E1F9E4CA14

Valid Until: 2026-05-31 23:59

 

Lecture 1——Fullerenes, geometric combinatorics and hyperbolic geometry.

Speaker: Victor Buchstaber (Steklov Mathematical Institute of RAS and Lomonosov Moscow State University)

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: At present, the fullerene classification problem is well-known and is important due to the applications in chemistry, physics, biology and nanotechnology. A mathematical fullerene is a three-dimensional convex simple polytope with all 2-faces being pentagons and hexagons. The talk is devoted to fundamental connections between the mathematical theory of fullerenes and geometric combinatorics, graph theory, the four-color problem, Coxeter groups, Pogorelov polyhedra, and Lobachevsky geometry. We present applications to the fullerene classification problem and to the classical problem of three-dimensional hyperbolic manifolds.

Bio: Prof. Victor Buchstaber is a Chief Scientific Researcher at Steklov Mathematical Institute of RAS and a Professor at Lomonosov Moscow State University. He is a Corresponding Member of the Russian Academy of Sciences. His research interests are geometry, topology and integrable systems.

 

Lecture 2——Exotic phenomena on 4-manifolds that survive a stabilization

Speaker: Jianfeng Lin

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: Starting in dimension 4, there is a significant difference between the category of smooth manifolds and the category of topological manifolds. Such phenomena are called the "exotic phenomena". In dimension 4,  there is an extra complication due to the failure of the h-cobordism theorem (in the smooth category). Stabilization on 4-manifolds means doing connected-sum with S2 cross S2. This operation naturally appears when one tries to adapt the proof of h-cobordism theorem in dimension 4. In the 1960s, Wall discovered an important principle: all exotic phenomena on orientable 4-manifolds will eventually disappear after sufficiently many stabilizations. Since then, it has been a fundamental problem to search for exotic phenomena that survive one stabilization. In this talk, we will discuss relevant backgrounds and show that such phenomena actually exist by proving the following two results (1) There exists a pair of diffeomorphisms on a 4-manifold that are topologically isotopic but not smoothly isotopic even after one stabilization. (2) There exists a pair of properly embedded surfaces in a 4-manifold with boundary which are topologically isotopic but not smoothly isotopic even after one stabilization (a part of the talk is based on the joint work with Anubhav Mukherjee).

Bio: Jianfeng Lin is an associate professor at Yau Mathematical Sciences Center, Tsinghua University. His research focuses on mathematical gauge theory, Floer homology and homotopy theory, and their applications in low dimensional topology.

 

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Lecture Series 32 —— April 1, 2022 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/EA0137B7FF3499884E6386E50694C639
Valid Until: 2026-05-31 23:59

 

Lecture 1——Quantum information related physics and mathematics

Speaker: Shaoming Fei

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: We introduce quantum information processing and the related physics and mathematics, including quantum coherence, quantum correlations, information masking, quantum uncertainty relations, as well as tensor network compressed sensing and machine learning.

Bio: Prof. Shao-Ming FEI, School of Mathematical Sciences, Capital Normal University, Beijing. Current research areas: quantum information & computation, and the related fundamental problems in quantum physics.

 

Lecture 2——On classical capacity of quantum channels

Speaker: Grigory Amosov (Steklov Mathematical Institute of RAS)

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: The quantum coding theorem proved in 1996 independently by A.S. Holevo, B. Schumacher and M.D. Westmoreland sets an upper bound on the number of states of a quantum system that can be used to encode classical information, so that the information can be asymptotically accurately restored after transmission. Such the quantity is known as a classical capacity of quantum channel. Due to the presence of entangled states in a composite quantum system that are not simple tensors, calculating the classical capacity turned out to be an extremely technically difficult task. An important example is given by channels generated by projective unitary representations of finite groups. This class includes Weyl channels, which, in turn, cover all unital qubit channels. Recently I found examples of channels belonging to this class for which the classical capacity can be calculated explicitly. The proof relies on the Karamata majorization method for probability distributions.

Bio: Dr. Grigory Amosov is a Leading Scientific Researcher at Steklov Mathematical Institute of RAS. His research interests are non-commutative probability theory and its applications in quantum theory of information and statistical decisions.

 

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Lecture Series 31 —— March 18, 2022 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/16EF94A12F9984919BAED5B0FEF3F4C7
Valid Until2026-04-30 23:59

 

Lecture 1——Presymplectic gauge PDEs and Batalin-Vilkovisky formalism

Speaker: Maxim Grigoriev

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: Gauge PDE is a geometrical object underlying what physicists call a local gauge field theory defined in terms of BV-BRST formalism. Although gauge PDE can be defined as a PDE equipped with extra structures, the generalization is not entirely straightforward as, for instance, two gauge PDEs can be equivalent even if the underlying PDEs are not. As far as Lagrangian gauge systems are concerned the powerful framework is provided by the Batalin-Vilkovisky (BV) formalism on jet-bundles. However, just like in the case of usual PDEs it is difficult to encode the BV extension of the Lagrangian in terms of the intrinsic geometry of the equation manifold while working on jet-bundles is often very restrictive, especially in analyzing boundary behavior, e.g., in the context of AdS/CFT correspondence. We show that BV Lagrangian (or its weaker analogs) can be encoded in the compatible graded presymplectic structure on the gauge PDE. In the case of genuine Lagrangian systems this presymplectic structure is related to a certain completion of the canonical BV symplectic structure. A presymplectic gauge PDE gives rise to the BV formulation through an appropriate generalization of the Alexandrov-Kontsevich-Schwarz-Zaboronsky (AKSZ) sigma-model construction followed by taking the symplectic quotient. The construction is illustrated on the standard examples of gauge theories with particular emphasis on the Einstein gravity, where this naturally leads to an elegant presymplectic AKSZ representation of the BV formulation for the Cartan-Weyl Lagrangian.

Bio: Maxim Grigoriev is the deputy director of Institute for Theoretical and Mathematical Physics, Lomonosov Moscow State University. Maxim Grigoriev's scientific interests include mathematical methods for describing gauge systems (dynamical constraints and symmetry, Batalin-Vilkovisky quantization), higher spin gauge theories, holography, sigma models in superstring theory, and noncommutative theories. He proposed the so-called parent formulation of gauge theories, which systematically combines the Batalin-Vilkovisky and Hamiltonian BRST approaches into a single formalism having the structure of the Aleksandrov-Kontsevich-Schwartz-Zaboronsky (AKSZ) (generalized) sigma model.

 

Lecture 2——Khovanov skein homology for links in the thickened torus

Speaker: Yi Xie

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: Khovanov homology is a powerful combinatorial invariant for links in the 3-sphere. Asaeda, Przytycki and Sikora defined a generalization of Khovanov homology for links in thickened compact surfaces.  In this talk, we will review their definition and show that the Asaeda-Przytycki-Sikora homology detects the unlink and torus links in the thickened torus. This is joint work with Boyu Zhang.

Bio: Yi Xie is an assistant professor at Beijing International Center for Mathematical Research, Peking University. His research focuses on mathematical gauge theory and its application in low-dimensional topology.

Slides:  ../../docs/20220322160158893897.pdf

 

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Lecture Series 30 —— March 4, 2022 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/0951A197D2D64E8E3847297BA19E5C4B
Valid Until2026-04-30 23:59

 

Lecture 1——Algebraic semantics for modal logic with propositional quantifiers

Speaker: Yifeng Ding

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: Algebraic semantics for modal logic with propositional quantifiers interpret formulas not just as true or false at some possible states, but directly as elements in a Boolean algebra, understood as an algebra of propositions. This general perspective allows us to study modal logics with propositional quantifiers that standard relational semantics based on states (possible worlds) cannot even define. In this talk, I will showcase the use of algebraic semantics in identifying conceptually significant modal logics with propositional quantifiers and also in proving mathematical/computational properties of such logics.

Bio: Yifeng Ding is an assistant professor at the Department of Philosophy at Peking University. He obtained his Ph.D. in Logic and the Methodology of Science from UC Berkeley in 2021. Before that, he received BA in philosophy and economics from Peking University in 2015.

He works mainly in modal logic, with serious interests also in decision theory and social choice theory. In modal logic, he has published works on logics for different kinds of knowledge, theories of non-normal modal logics, logics with propositional quantifiers, and comparative logics for probabilistic reasoning and set theory. In social choice, he is working on the axiomatization of several margin-graph-based voting methods.

 

Lecture 2——Circular proofs for non-classical logics

Speaker: Stepan Kuznetsov

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: Usually, in a logical proof a cycle, that is, using the statement we wish to prove as an argument towards proving it, is considered incorrect (circulus vitiosus). There is, however, a vividly developing field of study of circular proofs, where such cycles are allowed to be used, under certain conditions, without losing logical validity. In this talk, we survey several applications of this approach in non-classical logics, namely, modal logics and substructural logics with Kleene star.

Bio: Stepan Kuznetsov is a senior scientific researcher at Steklov Mathematical Institute, RAS. He currently offers courses in mathematical logic at MSU; and also courses in computer sciences at HSE University.

 

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Lecture Series 29 —— January 21, 2022 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/297519F065FD06FE91B6405B19FE9693
Valid Until: 2026-06-30 23:59

 

Lecture 1——Real algebraic and real pseudoholomorphic curves

Speaker: Stephan Orevkov (Steklov Mathematical Institute of RAS; Paul Sabatier University, Toulouse)

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: According to Gromov's theory, smooth symplectic 2-surfaces in CP^2 share many properties with complex algebraic curves. The same phenomenon takes place in the real case. Namely, smooth symplectic surfaces invariant under the complex conjugation (we call them real pseudoholomorphic curves) have many common properties with plane projective real algebraic curves.

An open question (Symplectic Isotopy Problem): does each connected component of the space of symplectic surfaces contain an algebraic curve? The same question can be asked in the real case and a negative answer will be given in the talk. We shall prove certain inequalities for the complex orientations of plane real algebraic curves which are not satisfied by an infinite series of real pseudoholomorphic curves.

Bio: Stephan Orevkov, PhD (Phys&Math), is a senior researcher at Steklov Institute of Mathematics, a lead researcher at MIPT, and also a researcher at Université Toulouse III - Paul Sabatier, France. His academic interests include topology of flat real algebraic curves and surfaces, the theory of braids, complex surface mapping (as applicable to the Jacobian hypothesis).

 

Lecture 2——On Ahlfors currents

Speaker:  Song-Yan Xie 

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: We answer a basic question in Nevanlinna theory that Ahlfors currents associated to the same entire curve may be nonunique. Indeed, we will construct one exotic entire curve which produces infinitely many cohomologically different Ahlfors currents. Moreover, concerning Siu's decomposition, for an arbitrary positive integer k or k=infinity, some of the obtained Ahlfors currents have singular parts supported on k irreducible curves. In addition, they can have nonzero diffuse parts as well, which answers a question of Brunella. This is joint work with Dinh Tuan Huynh.

Bio: Song-Yan Xie got his Ph.D. from Paris-Sud (Orsay) University in 2016. In his thesis he proved an ampleness conjecture of Debarre—— the cotangent bundles of a large class of complete intersections are ample. He is currently an associate professor at the Academy of Mathematics and Systems Science. His research interest is complex geometry, especially complex hyperbolicity and Nevanlinna theory.

 

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Lecture Series 28 —— December 17, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/63AB27F30444C926D8DADF2F74213506
Valid Until2026-04-30 23:59

 

Lecture 1——Quantization and Index Theory

Speaker: Si Li

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: In the first part, we introduce some basic ideas and various recent mathematical developments about quantization that arises from quantum field theory and string theory. In the second part, we discuss several applications to geometry and topology. In particular, we present an effective quantization theory for 2d chiral field theories, and explain its connection with elliptic chiral homology of chiral algebras and index theory.

Bio: Si Li got his Ph.D. in mathematics from Harvard University in 2011. He is currently professor at Yau Mathematical Sciences Center (YMSC), Tsinghua University. He works on algebraic and geometric aspects of quantum field theory and string theory.

 

Lecture 2——Korevaar–Schoen's energy on strongly rectifiable spaces

Speaker:  Alexander Tyulenev (Steklov Mathematical Institute of RAS)

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: We extend Korevaar-Schoen’s theory of metric valued Sobolev maps to cover the case of the source space being an RCD-space. When the target space is CAT(0) we establish that the corresponding energy functional is convex, lower semicontinuous and admits a unique minimizer, in line with the smooth situation. The talk is based on the joined work: Nicola Gigli, Alexander Tyulenev, “Korevaar–Schoen's energy on strongly rectifiable spaces”, Calc. Var. Partial Differential Equations, 60 (2021), 235, 54 pp., arXiv: 2002.07440
 

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Lecture Series 27 —— December 03, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/B1A478AB131AF84A7525B8A3083A54B1
Valid Until2026-04-30 23:59

 

Lecture 1——Tikhonov's solution to a class of linear systems equivalent within perturbations

Speaker: Eugene Tyrtyshnikov (INM RAS, Moscow)

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: A standard approach to incorrect problems suggests that a problem of interest is reformulated with the knowledge of some additional a priori information. This can be done by several well-known regularization techniques. Many practical problems are successfully solved on this way. What does not still look as completely satisfactory is that the new reset problem seems to appear rather implicitly in the very process of its solution.

In 1980, A.N. Tikhonov proposed a reformulation that arises explicitly before the discussion of the solution methods. He suggested a notion of normal solution to a family of linear algebraic systems described by a given individual system and its vicinity comprising perturbed systems, under the assumption that there are compatible systems in the class notwithstanding the compatibility property of the given individual system. Tikhovov proved that the normal solution exists and unique. However, a natural queston about the correctness of the reset problem was not answered. In this talk we address a question of correctness of the reformulated incorrect problems that seems to have been missed in all previous considerations. The main result is the proof of correctness for Tikhonov's normal solution. Possible generalizations and diffculties will be also discussed.

Bio: Marchuk Institute of Numerical Mathematics of RAS,director,  Academician of RAS.

 

Lecture 2— Liouville Properties of the Incompressible Navier-Stokes Equations

Speaker: Zhen Lei 

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract:  In this talk we will report recent results on the Liouville properties of bounded ancient solutions to the three-dimensional incompressible Navier-Stokes equations. These properties are crucial for excluding potential type I singularities  or understanding the structure of possible singulairites of local smooth solutions of the corresponding Cauchy problem.

Bio: Dr. Zhen Lei is a distinguished professor of School of Mathematical Sciences at Fudan University. His honors include: Second-prize Winner of the National Prize of Natural Sciences; Winner of Shanghai Peony Prize of Natural Science; National Science Foundation for Distinguished Young Scholars; Changjiang Distinguished Professor; National Special Support Program for Leading Talents in Science and Technology Innovation. He is the Vice President of China Society for Industry and Applied Mathematics. Professor Lei's research is focused on the theory of PDEs arising from fluid mechanics and methematical physics. He introduced the concept of strong null condition and proved the global well-posedness of classical solutions to the incompressible elastodynamics in 2D. He has also made significant contributions to the well-posedness theory and Liouville properties of the incompressible Navier-Stokesequations. Professor Lei holds the position of associate editor-in-chief of Chinese Annals of Mathematics; associate editor-in-chief of Journal of Fudan University (Natural Science). He also serves at the editorial board for several academic journals, such as Communications in Mathematical Sciences, Communications on Pure and Applied Mathematics, Fundamental Research, etc.

 

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Lecture Series 26 —— November 19, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/2DB90D3577355CD54F6DB04AAB1831AD
Valid Until2026-04-30 23:59

 

Lecture 1——Propagation of quasi-particles on singular spaces. Relation to the behavior of geodesics and to certain problems of analytic number theory

Speaker: Andrey Shafarevich

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: We study propagation of semi-classical localized solutions of Schroedinger or wave equations (Gaussian beams) on a certain class of singular spaces. These spaces are obtained by connecting of a number of smooth manifolds by several segments. Laplacians on such spaces are defined with the help of extension theory an depend on boundary conditions in the points of gluing. Statistics of a number of Gaussian packets is governed by the behavior of geodesics on manifolds and is connected with certain problems of analytic number theory -  in particular, with the problem of distribution of abstract primes.

Bio: Prof. A.I. Shafarevich is currently the Dean of the Faculty of Mechanics and Mathematics at Lomonosov Moscow State University. He is also the Corresponding Member of the Russian Academy of Sciences.

The main scientific interests of A.I.Shafarevich lie in the field of mathematical physics, asymptotic and geometric theory of linear and nonlinear partial differential equations, quantum mechanics and hydrodynamics. He solved the problem posed by V.P. Maslov and widely discussed in the scientific literature on the multiphase asymptotics for the equations of hydrodynamics.

 

Lecture 2——Toda equations and cyclic Higgs bundles over non-compact surfaces

Speaker: Qiongling Li 

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: For Higgs bundles over compact Kahler manifods, it is known by Hitchin and Simpson that the existence of Hermitian-Einstein metric is equivalent to the polystability of the Higgs bundle. There are some generalizations to non-compact cases. On a Riemann surface with a holomorphic r-differential, one can naturally define a Toda equation and a cyclic Higgs bundle with a grading. A solution of the Toda equation is equivalent to a Hermitian-Einstein metric of the Higgs bundle for which the grading is orthogonal. In this talk, we focus on a general non-compact Riemann surface with an r-differential which is not necessarily meromorphic at infinity. In particular, we discuss the Hermitian-Einstein metrics on the cyclic Higgs bundles determined by r-differentials. This is joint work with Takuro Mochizuki (Kyoto University).

Bio: Qiongling Li got her Ph.D. from Rice University in 2014. She is currently a research fellow at Chern Institute of Mathematics, Nankai University. Her main research fields are Higgs bundles, harmonic maps, and higher Teichmuller theory. Her recent works have been focused on understanding the non-abelian Hodge correspondence over Riemann surfaces.

 

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Lecture Series 25 ——November 05, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/75414BFD1162CE3C9CCC5376E2FE94F0
Valid Until2026-04-30 23:59


Lecture 1——On isochronous dynamics.

Speaker: Dmitry Treschev (Steklov Mathematical Institute of Russian Academy of Sciences).
Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)
Abstract: We propose a systematic approach to the problem of isochronicity in Hamiltonian dynamics. In particular, we present an explicit neccesary and sufficient condition for isochronicity in the case of 1DOF in terms of the Taylor expansion of the Hamiltonian function.
Bio: Dmitry Treschev: Director of Steklov Mathematical Institute of RAS, Academician of RAS (2016), Invited speaker at ICM (2002), Lyapunov prize of RAS (2007), Russian Federation prize for young scintists (1995).
 
 
Lecture 2——Smoothed particle hydrodynamics (SPH) for modeling fluid-structure interactions
Speaker: Moubin Liu
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Abstract: SPH, as a truly Lagrangian and meshfree particle method, is very attractive in modeling fluid-structure interaction (FSI) problems. This talk reports some recent developments of SPH method in modeling FSI problems with rigid, elastic and flexible structures, with granular materials, and with extremely intensive loadings.  
Bio: Moubin Liu is the Vice Dean and a Professor of the College of Engineering, Peking University. His areas of interest include computational fluid dynamics and computational fluid-structures interactions, using particle-based methods including SPH, and particle-grid coupling approaches including SPH-FEM, DEM-CFD and etc.

Weblink: 
http://www2.coe.pku.edu.cn/subpaget.asp?id=628

 

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Lecture Series 24 —— October 22, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/6108285A02ADB53008FDB05BEB66F6D6
Valid Until: 2026-06-30 23:59

 

Lecture 1——What we know and what we do not know about the zeros of Riemann zeta-function

Speaker: Prof. Maxim Korolev

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: In the talk, we will discuss from different points of view the connection between quite "transcendental" objects, that is, between zeros of the Riemann zeta-function, and purely arithmetic objects, that is, prime numbers.

Bio: Maxim Korolev is a Professor of the Russian Academy of Sciences. He has received the Vinogradov Prize of the Russian Academy of Sciences in 2019.

 

Lecture 2——Finiteness and Duality for the Cohomology of Prismatic Crystals

Speaker: Yichao Tian 

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: Prismatic site of a p-adic formal scheme was introduced in the recent pioneer work of Bhatt—Scholze. It provides a uniform framework for various p-adic cohomology theories. Prismatic crystals are natural analogues of classical crystalline crystals on prismatic sites. In this talk, after reviewing some basic definitions of the prismatic site, I will discuss some basic properties of the cohomology of prismatic crystals on smooth p-adic formal schemes. The key ingredient is an explicit local description of (reduced) prismatic crystals in terms of Higgs modules. 

Bio: Yichao Tian got his Ph. D. from University Paris in 2008. He is currently a professor in the Morningside Center of Mathematics at the Chinese Academy of Science. His main research fields are Arithmetic algebraic geometry: p-adic Hodge theory, Geometry of Shimura varieties in characteristic p > 0, p-divisible groups, and p-adic modular forms.

 

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Lecture Series 23 —— October 08, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/A57739A4E5705369970A3175767FC017
Valid Until2026-04-30 23:59


Lecture 1——Weighted graphs, tetrahedron equation and loop quantum gravity

Speaker: Prof. Dmitry Talalaev

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: Edge-weighted graphs are a combinatorial object parametrizing several archetypal models of statistical physics: the dimer model, the Ising model and the model of electrical networks. Each of these models describes some combinatorial problem, is associated with some solution of the tetrahedron equation, is associated with one of the versions of the completely positive Grassmannian. I will talk about these phenomena and how these problems are related to loop quantum gravity, namely spin foam evaluations. 
Bio: Dmitry Talalaev Graduated from the Faculty of Mechanics and Mathematics of Moscow State University, received a doctorate in Physics and Mathematics at the Steklov Institute, specializes in classical and quantum integrable systems, including models of statistical physics, applications in low-dimensional topology and cluster algebras.

Lecture 2——An invitation to categorical enumerative invariants.

Speaker: Junwu Tu

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Abstract: In this talk, we shall sketch the definition of categorical enumerative invariants following Costello (2004/2005) and Caldararu-T. (2020). Then we survey known calculations of these categorical invariants. In the end, we also discuss some research problems in this direction.
Bio: Junwu Tu got his Ph.D. from University of Wisconsin-Madison in 2011. He is currently an associate professor in the Institute of Mathematical Sciences (IMS) at ShanghaiTech University. His main research fields are homological algebras related to mirror symmetry. His recent works have been focused on understanding categorical enumerative invariants defined by Costello back in 2004. 

 

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Lecture Series 22 —— September 17, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/15C3899F5E087E67898778568B354DC0
Valid Until2026-04-30 23:59


Lecture 1——Liouville theorem for a class of semilinear elliptic equation on Heisenberg group

SPEAKER: Prof. Xinan Ma, University of Science and Technology of China. 

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: We obtain a Liouville type theorem  for a class of semilinear  subcritical elliptic equation on Heisenberg group. The proof is based on a'priori integral estimate from a generalized differential identity found by Jerison and Lee in 1988. We also get a point-wise estimate near the isolated singularity. This is a joint work with Qianzhong Ou.
Bio: Xinan Ma got Ph. D from Hangzhou University in 1996. He is now working at the School of Mathematical Sciences, University of Science and Technology of China.   His main research fields are nonlinear elliptic equation and geometry analysis.  

Lecture 2 ——Symplectic and Contact Geometry of Monge–Ampère equation: Introduction and application.
Speaker: Vladimir Rubtsov (Université d'Angers)
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract:  I am going to present an introduction into the geometric approach to Monge–Ampère operators and equations based on contact and symplectic structures of cotangent and the 1st jet bundles of a smooth manifold. This approach was developed by V. Lychagin and goes back to the ideas of E.Cartan and his successor T. Lepage. I shall try to make my talk self-contained. I also plan to discuss various applications and links with important geometric structures.
Bio: Vladimir (Volodya) Rubtsov graduated in Mathematics from the Moscow State University in 1974 with a MSc in Differential Geometry and Applications. He has a PhD in Higher Geometry and Topology (1983) and held research and teaching positions at various Mathematics and Applied Mathematics Laboratories in the former Soviet Union. Presently he is Professor at the Department of Mathematics, Université d'Angers, and a member of LAREMA (Anjou Research Mathematical Laboratory) of CNRS (France). Since 1993 he is a Senior Researcher at the Theory Division in the Alikhanov Institute for Theoretical and Experimental Physics (ITEP) in Moscow. He held visiting positions at Ecole Polytechnique (Palaiseau, France), Universities of Lyon, Lille and Strasbourg (France), University of Uppsala (Sweden), SISSA (Italy) and others. He was invited member at IHES, MPIM (Bonn), the Newton Institute (Cambridge, UK) and others. His research is in the area of Poisson geometry, quantum Groups, integrable systems, symplectic and contact geometric methods in non-linear differential equations and applications in hydrodynamics.

 

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Lecture Series 21 —— June 4, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/5D3D940A96DAC4AAF631D25AC6CA0288
Valid Until2026-04-30 23:59


Lecture 1——Integrable systems with elliptic dependence on momenta and related topics
Speaker: Andrei Zotov (Steklov Mathematical Institute of Russian Academy of Sciences)
Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)
Abstract: We discuss a family of integrable many-body systems of classical (and quantum) mechanics. Some interrelations (dualities) predict existence of integrable many-body systems with elliptic dependence on particles momenta – the most general representative of this family. We describe some recent results on this topic. Next, we discuss relations of the many-body systems to other families of integrable models including integrable tops and spin chains. Finally, some interesting open problems are formulated.
Bio: Andrei Zotov is a leading researcher at Steklov Mathematical Institute. Also, associative professor at Moscow Institute of Physics and Technology and researcher at ITEP and HSE – Skoltech International Laboratory of Representation Theory and Mathematical Physics. Main field of research is mathematical physics and integrable systems.


Lecture 2 ——Off-diagonal Bethe ansatz approach to quantum integrable models  
Speaker: Wenli Yang
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Abstract:  Applying the recent developed method-the off-diagonal Bethe ansatz method, we construct the exact solutions of the Heisenberg spin chain with various boundary conditions. The results allows us to calculate the boundary energy of the system in the thermo dynamic limit. The method used here can be generalized to study the thermodynamic properties and boundary energy of other high rank models with non-diagonal boundary fields.
Bio: Wenli Yang is a professor and PhD supervisor in the School of Physics at North-western University. He is currently the executive director of the Chinese Physical Society and a member of the National Committee on Condensed Matter Theory and Statistical Physics. He received his bachelor's degree from Xi'an Jiaotong University in 1990 and his Ph.D. degree from North-western University in 1996, and has worked at the University of Bonn, Germany, Kyoto University, Japan, and the University of Queensland, Australia. In 2009, he was selected as one of the first "Hundred Talents Plan" in Shaanxi Province, and in 2014, he was awarded the National Outstanding Youth Fund, and in 2015, he was selected as one of the Changjiang Distinguished Professors of the Ministry of Education. His achievements were awarded the Second Prize of Natural Science of the Ministry of Education in 2010 and the First Prize of Science and Technology of Shaanxi Province in 2012.

 

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Lecture Series 20 —— May 21, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)


Lecture 1 —— On the application of the Ważewski method to the problem of global stabilization
Speaker: Ivan Polekhin (Steklov Mathematical Institute of RAS).
Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)
Abstract: In 2000, S.P. Bhat and  D.S. Bernstein proved that if the configuration space of an autonomous control mechanical system is closed (compact without boundary), then the system cannot have a globally asymptotically stable equilibrium [1]. We will present a similar result for non-autonomous control systems defined on manifolds with non-empty boundaries. The talk is based on the paper [2].

[1] Bhat S.P., Bernstein D.S. A topological obstruction to continuous global stabilization of rotational motion and the unwinding phenomenon Systems Control Lett., 39 (1) (2000), pp. 63-70
[2] I. Polekhin, “On the application of the Ważewski method to the problem of global stabilization”, Systems & Control Letters, 153 (2021) Share Link: https://authors.elsevier.com/a/1d2Qoc8EXim67

Bio: Russian Academy of Sciences prize for young Russian scientists (2020)

Lecture 2 ——High Fidelity Simulations of High-Pressure Turbines Cascades for Data-Driven Model Development
Speaker: Yaomin Zhao, College of Engineering, Peking University
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Abstract: Gas turbines (GT) are, and will continue to be, the backbone of aircraft propulsion, as well as power generation and mechanical drive. A small GT performance improvement is expected to have a fuel-spend advantage of the billion-dollar order, together with a significant CO2 emission benefit. Part of the possible performance improvements can be enabled by continuously advancing the understanding of the GT flow physics and thus further reducing the inaccuracy of current design tools based on computational fluid dynamics (CFD). By exploiting the capability of our high-fidelity CFD solver on leadership GPU-accelerated supercomputers, we have been able to perform state-of-the-art high fidelity simulations of turbomachinery flows. The generated data, therefore, can shed light on the detailed fundamental flow physics, in particularly the behavior of transitional and turbulent boundary layers affected by large-scale violent freestream turbulence, under strong pressure gradient and curvature. Furthermore, machine learning methods are applied to the high-fidelity data to develop low order models readily applicable to GT designs. 
Bio: Dr. Yaomin Zhao is an Assistant Professor at Peking University, China. He obtained his B.Sc. in 2011 and then Ph.D. in 2017 both from Peking University. The Ph.D. thesis, Lagrangian investigation on transitional wall-bounded flows, was awarded the Outstanding PhD Thesis by Chinese Society of Theoretical and Applied Mechanics in 2018. From 2017 to late 2020, he was a post-doctocal research fellow at the University of Melboune, Australia. His research interests include high-fidelity simulations of turbomachinery flows, turbulence model development with machine learning methods, and boundary layer transition, etc.

 

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Lecture Series XIX —— May 14, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/00B707ED52223278BF9974EA3B1ED9DA
Valid Until2026-04-30 23:59


Lecture 1 —— Lorentz geometry and contact topology
Speaker: Stefan Nemirovski (MIAN).
Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)
Abstract: Roger Penrose observed four decades ago that the space of light rays of a reasonable spacetime carries a natural contact structure and raised the problem of describing the causality relation of the spacetime in its terms. The talk will survey the progress made in this direction from the seminal work of Robert Low to the more recent applications of global contact rigidity.
Bio: Corresponding member of the Russian Academy of Sciences, winner of the European Mathematical Society prize (2000).

Lecture 2 ——Gromov-Hausdorff limit of manifolds and some applications
Speaker: Wenshuai Jiang(Zhejiang University)
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Abstract: Gromov-Hausdorff distance is a distance between two metric spaces, which was introduced by Gromov 1981. From Gromov’s compactness theorem, we knew that any sequence of manifolds with uniform lower Ricci curvature bounds has a converging subsequence in Gromov-Hausdorff topology to a limit metric space.  The limit metric space in general may not be a manifold. The structure of such limit metric space has been studied by Cheeger, Colding, Tian, Naber and many others since 1990. It turns out that such theory has powerful application in geometry. In fact, the resolution of Yau-Tian-Donaldson conjecture was largely relied on the development of the study of the limit metric space.

In the first part of the talk, we will discuss some recent progress of the Gromov-Hausdorff limit of a sequence of manifolds with Ricci curvature bounds. In the second part, we will discuss some applications based on the study of Gromov-Hausdorff limits.

Bio: Wenshuai Jiang studied in the Department of mathematics of Nanjing University from 2007 to 2011 and obtained his bachelor's degree. From 2011 to 2016, he studied in school of Mathematical Sciences of Peking University and obtained a doctorate under the guidance of Professor Gang Tian. He has been working in Zhejiang University since 2016, and is currently an associate professor of Zhejiang University. His major research interest is geometric analysis.

 

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Lecture Series XVIII —— April 23, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/00B707ED52223278BF9974EA3B1ED9DA
Valid Until2026-04-30 23:59

 

Lecture 1 ——  VALUES OF PERMANENT AND POSITIVE SOLUTION OF WANG-KRÄUTER PROBLEM
Speaker: A.E. GUTERMAN (RUSSIA, MSU)
Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)
Abstract:


Lecture 2 ——  From Sphere Packings to Post-Quantum Cryptography 
Speaker: Chuanming Zong (Tianjin University)
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Abstract: 


Bio: Chuanming Zong obtained his PhD from Vienna University of Technology in 1993. He was a professor at the Chinese Academy of Sciences and Peking University. Currently, he is a distinguished professor at Tianjin University. He mainly works in number theory. He has made important contribution in Hilbert’s 18th problem and tiling theory. He has been awarded a Conant Prize by Amer Math Soc in 2015, a National Science Prize by the Chinese government in 2009, and a S. S. Chern Prize by the Chinese Math Soc in 2007. He was a plenary speaker at Asiacrypt2012, a author of two solicited papers in Bull AMS and three books at Springer and Cambridge University Press.

 

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Lecture Series XVII —— April 9, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/E6EB60DE09499782270BB3B51570DFA1
Valid Until2026-04-30 23:59


Lecture 1 ——  Mathematical methods of quantum key distribution.
Speaker: Anton Trushechkin (MIAN).
Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)
Abstract: Quantum key distribution and, more generally, quantum cryptography is a modern branch of science where methods of secure communication based on principles of quantum mechanics are studied. The rigorous proof of the security of quantum key distribution gave rise to a complex and  beautiful mathematical theory, which is based on methods of quantum information theory, namely, quantum entropic measures and entropic uncertainty relations. In particular, to estimate secret key rate, one needs to minimize the quantum relative entropy (a convex function) subject to linear constraints. The problem is, in general, infinite-dimensional, but symmetry properties of the problem reduces the dimensionality and allows one to solve this problem analytically. However, currently, an important task is to prove the security of quantum key distribution with imperfect (i.e., practical) devices. Imperfections introduce asymmetries and thus make the problem more complicated. In the talk, estimations for the secret key rate in the case of detection-efficiency mismatch will be presented. Using entropic uncertainty relations, an infinite-dimensional problem is reduced to a one-dimensional one.
Bio:Results of Anton Trushechkin in quantum cryptography were nominated as one of most important mathematical achievements of the Russian Academy of Sciences in 2020.


Lecture 2 ——A quantum leap in security.
Speaker: Prof. Feihu Xu, University of Science and Technology of China.
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Abstract: Quantum cryptography or quantum key distribution (QKD) offers information-theoretic security based on the laws of physics. This is the technology at the basis of the quantum satellite “Mozi”, put in orbit by the Chinese Academy of Sciences in 2016. In practice, however, the imperfections of realistic devices might introduce deviations from the idealized models used in the security proofs of QKD. Can quantum code breakers successfully hack real systems by exploiting the side channels? Can quantum code makers design innovative countermeasures to foil quantum code breakers? In this talk, I will talk about the theoretical and experimental progress in the practical security aspects of quantum code making and quantum code breaking. After numerous attempts over the past decades, researchers now thoroughly understand and are able to manage the practical imperfections. Recent advances, such as the decoy-state, measurement-device-independent (MDI) and twin-field (TF) protocols, have closed critical side channels in the physical implementations in a rigorous and practical manner. Further readings in [Xu et al., Rev. Mod. Phys. 92, 025002 (2020)].
Bio:Feihu Xu has been a Professor at USTC since Oct. 2017. Before joining USTC, he was a Postdoctoral Associate at MIT in 2015-2017. He received an M.A.Sc and Ph.D from University of Toronto in 2011 and 2015. He works on quantum information science and has co-authored more than 70 journal papers. As the first/corresponding author, he has published more than 40 journal papers in Rev. Mod. Phys. (1), Nat. Photon. (4), Nat. Phys. (1), etc. He is the recipient of Early Career Award by NJP in 2020, 35 Innovators Under 35 of China (by MIT Technology Review) in 2019, Outstanding Dissertation Award (by OCPA) in 2015, and Best Paper Award of QCrypt in 2014.

 

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Lecture Series  XVI ——March 26, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/C95AD535339960AB095CCE3E7C231216
Valid Until2026-04-30 23:59

 

Lecture 1 —— Transference principle in Diophantine approximation

Speaker: Oleg German (MSU)

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: The talk will be devoted to one of the fundamental principles in Diophantine approximation called transference principle. It reflects the relation of duality between certain problems. This principle is usually formulated in terms of Diophantine exponents - they generalise to the multidimensional case the measure of irrationality of a real number. We plan to give an account on the existing relations Diophantine exponents satisfy and try to reveal the geometric nature of those relations. After having described some basic geometric constructions, we shall look from this perspective at the famous linear independence criterion that belongs to Nesterenko. It appears that our approach provides an alternative proof of this criterion, which bases on rather simple geometric considerations.

Bio:Oleg German graduated from Moscow State University in 2001, defended the Candidate thesis in 2005 at MSU and the Doctorate thesis in 2013 at Steklov Mathematical Institute. He works at the Department of Number Theory, Faculty of Mechanics and Mathematics, MSU. His research interests include geometry of numbers, Diophantine approximation, multidimensional continued fractions.
 
Lecture 2 ——Introduction to p-adic Langlands program for GL_2

Speaker: Hu Yongquan

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract:  The p-adic and mod p Langlands program is an avatar of the classical Langlands program and has been first initiated by C. Breuil. In this colloquium talk, I will give a brief introduction to the program and survey some recent progress in the case of GL_2.

Bio:Yongquan Hu received PhD degree from University Paris-Sud in 2010. After that, he has worked at University of Rennes 1 (France) as a Maître de Conférence. Starting from 2015, he is a Professor at Morningside Center of Mathematics, Academy of Mathematics and Systems Science. His research interest lies in p-adic and mod p Langlands program.

 

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Lecture Series  XV —— March 12, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/35FAFAB495AAAB508AE966572F3DF218
Valid Until2026-04-30 23:59


Lecture 1 ——Mathematical problems in the theory of topological insulators

Speaker: Armen Sergeev (Steklov Mathematical Institute, Moscow).

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: The talk is devoted to the theory of topological insulators - a new and actively developing direction in solid state physics. To find a new topological object one have to look for the appropiate topological invariants and systems for which these invariants are non-trivial. The topological insulators are characterized by having wide energy gap stable for small deformations. A nice example is given by the quantum Hall spin insulator. It is a two-dimensional insulator invariant under the time reversal. It is characterized by the non-trivial topological Z_2-invariant introduced by Kane and Mele.
In our talk we consider the topological insulators invariant under time reversal. In the first part we present the physical basics of their theory while the second part deals with the mathematical aspects. These aspects are closely related to K-theory and non-commutative geometry.

 

Bio:Prof. Armen Glebovich Sergeev is a leading scientific researcher of the department of complex analysis in Steklov Mathematical Institute and a professor in Mechanical and Mathematical department of Moscow State University. He Got Ph. D in Moscow State University in 1975 and Doctor of Sciences in Steklov Mathematical Institute at Moscow in 1989. He is a foreign member of Armenian Academy of Sciences, member of the board of Moscow Mathematical Society and a member of Executive Committee of European Mathematical Society. He is the Chief-editor of many mathematical journals and published 106 papers and is the author of 10 books. His Principal fields of research include Pseudoconvex polyhedral, Invariant domains of holomorphy, Geometric quantization, Twistor quantization, Seiberg-Witten equations, Pseudoholomorphic curves and Vortex equations. He has been the scientific advisors of many doctors. Together with Prof. Xiangyu Zhou, they have organized a series of Sino-Russia Joint mathematical conferences for many years which has promoted greatly the mathematical cooperation between two countries. 

 

Lecture 2 ——Some recent applications of the strong openness property.
Speaker: Qi'an Guan
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract:  The multiplier ideal sheaf plays an important role in several complex variables, complex geometry and algebraic geometry. The strong openness property for multiplier ideal sheaves was conjectured by Demailly and proved by Guan-Zhou. In this talk, we will recall some recent applications of the strong openness property on the restriction formula and subadditivity property related to multiplier ideal sheaves. This is joint work with Professor Xiangyu Zhou.

 

Bio: Qi'an Guan graduated from the Institute of mathematics and systems science, Chinese Academy of Sciences in 2011 as a Ph.D, and his advisor is Professor Xiangyu Zhou.
After graduation, he worked as a postdoctoral researcher in Beijing International Center for Mathematics Research for two years, and his co-advisor is Professor Xiaobo Liu.
In 2013, he joined the School of Mathematical Sciences of Peking University and is now a professor.
Qi'an Guan is mainly engaged in the study of several complex variables.
Qi'an Guan has won the "outstanding postdoctoral Award" (2013) of Peking University, the "Young Teacher Award" (2016) of Huo Yingdong education foundation, and the "Chang Jiang Scholars Program - Young Scholars" (2016) and the "Science Research Famous Achievement
Award in Higher Institution – Youth Science Award" (2017) of the Ministry of Education, the "Qiu Shi Outstanding Young Scholars Award " (2016), the " National Award for Youth in Science and Technology--Special Prize" (2019) of the Chinese Association for science and technology, “The Tan Kah Kee Young Scientist Award in Mathematics & Physics” (2020).
Qi'an Guan was supported by the "Excellent Young Scientists Fund"(2015) and "National Science Fund for Distinguished Young Scholars" (2018) of the National Natural Science Foundation of China.
 

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Lecture Series  XIV —— January 29, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/0930E258DA1D1B986E4238DB4E21D826
Valid Until2026-04-30 23:59


Lecture 1 ——The Aerothermal Performance of Tip Leakage Flow in High Pressure Turbines.
Speaker: Prof. Chao Zhou, College of Engineering, Peking University, Beijing, China
Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)
Abstract: Future aero engines are expected to achieve higher efficiencies and lower emissions, which brings new challenges for turbine designers. In a high-pressure turbine, tip clearances exist between the turbine rotor blade tip and the casing to prevent rubbing. The pressure difference between the blade pressure side and the suction side drives the gas across this tip clearance gap. The high-temperature gas results in excessively high metal temperatures on the blade tip, which lead to thermal erosion and oxidation. Obtaining good aerothermal performance is the key to maintain the performance of the high pressure turbines. The current talk will present a combined experimental and numerical study, which aims to understand the performance of the tip leakage flow and to develop new tip configurations for higher engine efficiency. First, the aerodynamic and heat transfer performance of squealer tips will be discussed. The effects of the squealer height and thickness will be investigated. Then, the tips with
coolant injection are investigated to understand the effects of the cooling air on the loss mechanism and tip heat transfer. Finally, winglet configurations are used on blade tips to reduce the tip leakage loss. The results showed that by using the winglet tip developed in the current study, the turbine stage efficiency increases. 

Bio: Chao Zhou is a tenured associate professor and the director of turbomachinery laboratory at the college of Engineering in Peking University, China. Before join Peking University, he obtained his doctorate degree at the Whittle Laboratory of Cambridge University in 2010. He is also educated in Nanjing University of Aeronautics and Astronautics, China, and received his Master degree and Bachelor in 2006 and 2003 respectively. His main research area is the aerodynamic and heat transfer of turbomachinery, including aerothermal performance of high pressure turbines, high-lift low pressure turbines; inter-turbine duct flows, unsteady flows and loss mechanism of turbomachinery, advanced cooling methods and highly loaded compressors. He has published 9 papers on the Journal of Turbomachinery, which is the top Journal in the research area. Dr. Zhou is a member of ASME IGTI Tubomachinery committee. He serves as the review co-chair of 2020 GPPS (Global Power and Propulsion Society) conference. 

Lecture 2 —— Mathematical Models of Mediums in Continuum Mechanics.
Speaker: Dmitrii Georgievskii
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Abstract: Elements of the theory of constitutive relations. The tangent modulus and the tangent compliance. Physical nonlinearity, tensor linearity (quasilinearity), and nonlinearity. The material functions. Rheonomic and scleronomic media. Homogeneous and inhomogeneous media. Composites. Elastic bodies. Viscous liquids. Media with memory. Non-local media. Tensor functions and their invariants in the theory of constitutive relations. Potential media and conditions of potentiality. Incompressible materials (liquids).Nonlinear elastic-viscoplastic models. Classification of incompressible media (quasilinear models, Bingham bodies, perfectly plastic media, Newtonian viscous fluids). Statement of the linearized boundary value problem of flow stability with respect to small perturbations of the initial data.

Bio: Dmitrii Georgievskii received his PhD degree at MSU, 1989, and DSc degree at MSU, 1996. He is a Professor of Russian Academy of Sciences since 2015and is a Chair of Lab. of Elasticity and Plasticity in Institute of Mechanics (MSU) since 2020. His research interests include the Theory of constitutive relations in continuum mechanics, Phenomenological description of stress-strain state by multiscale simulation, Asymptotic methods in theory of thin solids, see also web-page http://mech.math.msu.su/~georgiev/first_e.htm for more details.

 

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Lecture Series  XIII —— January 15, 2021 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/9ED10161227A7A8F325E9F07F7388A80
Valid Until2026-04-30 23:59

 

Lecture 1 ——Linear stability of pipe Poiseuille flow at high Reynolds number regime

Speaker: Zhifei Zhang, School of Mathematical Sciences, Peking University

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: The linear stability of pipe Poiseuille flow is a long standing problem since Reynolds experiment in 1883. Joint with Qi Chen and Dongyi Wei, we solve this problem at high Reynolds regime. We first introduce a new formulation for the linearized 3-D Navier-Stokes equations around this flow. Then we establish the resolvent estimates of this new system under favorable artificial boundary conditions. Finally, we solve the original system by constructing a boundary layer corrector.

Bio: Zhifei Zhang received his PhD from Zhejiang university in 2003. Then he spent 2 years in Mathematics Institute of AMSS as a Postdoc. He joined Peking university in 2005. His research interest is in the mathematical problems in the fluid mechanics such as the well-posedness of the Navier-Stokes equations, free boundary problem, hydrodynamic stability.

 

Lecture 2 —— Partial spectral flow and the Aharonov–Bohm effect in graphene.

Speaker: Vladimir E. Nazaikinskii Ishlinsky Institute for Problems in Mechanics RAS

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: We study the Aharonov–Bohm effect in an open-ended tube made of a graphene sheet whose dimensions are much larger than the interatomic distance in graphene. An external magnetic field vanishes on and in the vicinity of the graphene sheet, and its flux through the tube is adiabatically switched on. It is shown that, in the process, the energy levels of the tight-binding Hamiltonian of π-electrons unavoidably cross the Fermi level, which results in the creation of electron–hole pairs. The number of pairs is proven to be equal to the number of magnetic flux quanta of the external field. The proof is based on the new notion of partial spectral flow, which generalizes the ordinary spectral flow introduced by Atiyah, Patodi, and Singer and  already having well-known applications (such as the Kopnin forces in superconductors and superfluids) in condensed matter physics.

Bio: Vladimir Nazaikinskii received PhD degree from Moscow Institute of Electronic Engineering in 1981 and DSc degree from Steklov Mathematical Institute of RAS in 2014 and was elected Corresponding Member of RAS in 2016. He works at Ishlinsky Institue for Problems in Mechanics of RAS as a principal researcher. His research interests include asymptotic methods in the theory of differential equations and mathematical physics; asymptotic methods in the statistics of many-particle systems and relations to number theory; C*-algebras and noncommutative geometry; elliptic theory and index theory.

 

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Lecture Series  Ⅻ —— December 18th, 2020 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)
 

Recording: https://disk.pku.edu.cn:443/link/E9B034DE79B98247C575EAFA19567D82
Valid Until:2026-04-30 23:59

 

Lecture 1 —— Polynomial structures in higher genus enumerative geometry
Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)
Speaker: Shuai Guo, School of Mathematical Sciences, Peking University).
Abstract: It is important to calculate the enumerative invariants from various moduli theories in mirror symmetry. The polynomial structure is often appeared in those quantum theories, including the Calabi-Yau type and the Fano type theories. Such conjectural structure is also called the finite generation conjecture in the literature. For each genus, it is conjectured that the computation of infinite many enumerative invariants can be converted to a finite computation problem. The original motivation of studying such structures will also be mentioned. This talk is based on the joint work with Janda-Ruan, Chang-Li-Li, Bousseau-Fan-Wu and Zhang respectively.
Bio: Shuai Guo got Ph. D in Tsinghua University, 2011 and now is an associate professor in SMS of Peking University.
Research interests: Higher genus enumerative geometry and mirror symmetry.
Honors: 2019 "QiuShi" Outstanding Youth Award (2019), Selected as the national youth talent support program of China (2019).
 
Lecture 2 ——Smooth compactifications of differential graded categories
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Speaker: Prof. Alexander Efimov, Steklov Mathematical Institute of Russian Academy of Sciences.
Abstract: We will give an overview of results on smooth categorical compactifications, the questions of theire existence and their construction. The notion of a smooth categorical compactification is closely related with the notion of homotopy finiteness of DG categories.
First, we will explain the result on the existence of smooth compactifications of derived categories of coherent sheaves on separated schemes of finite type over a field of characteristic zero. Namely, such a derived category can be represented as a quotient of the derived category of a smooth projective variety, by a triangulated subcategory generated by a single object. Then we will give an example of a homotopically finite DG category which does not have a smooth compactification: a counterexample to one of the Kontsevich's conjectures on the generalized Hodge to de Rham degeneration.
Finally, we will formulate a K-theoretic criterion for existence of a smooth categorical compactification, using DG categorical analogue of Wall's finiteness obstruction from topology.
Research interests: algebraic geometry, mirror symmetry, non-commutative geometry.
Honors: European Mathematical Society Prize (2020), Russian Academy of Sciences Medal with the Prize for Young Scientists (2017), Moscow Mathematical Society award (2016).
 

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Lecture Series Ⅺ ——December  4th, 2020 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)
 
Recording: https://disk.pku.edu.cn:443/link/40515B49A258749CAB6F1CC4CEE0D61D
Valid Until:2026-04-30 23:59
 
Lecture 1 —— On homology of Torelli groups
Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)
Speaker: Prof. Alexander Gaifullin, Steklov Mathematical Institute & Skolkovo Institute of Science and Technology, Russia.
Abstract: The mapping class groups of oriented surfaces are important examples of groups whose properties are closely related to geometry and topology of moduli spaces, topology of 3-manifolds, automorphisms of free groups. The mapping class group of a closed oriented surface contains two important subgroups, the Torelli group, which consists of all mapping classes that act trivially on the homology of the surface, and the Johnson kernel, which is the subgroup generated by all Dehn twists about separating curves. The talk will be devoted to results on homology of these two subgroups. Namely, we will show that the k-dimensional homology group of the genus g Torelli group is not finitely generated, provided that k is in range from 2g-3 and 3g-5 (the case 3g-5 was previously known by a result of Bestvina, Bux, and Margalit), and the (2g-3)-dimensional homology group the genus g Johnson kernel is also not finitely generated. The proof is based on a detailed study of the spectral sequences associated with the actions of these groups on the complex of cycles constructed by Bestvina, Bux, and Margalit.
Bio: Prof. Alexander Gaifullin is the Correspondent member of the Russian Academy of Sciences (since 2016). He got the following honours: Prize of the President of the Russian Federation in the field os science and innovations for young scientists (2016), Prize of the Moscow Mathematical Society (2012). He is the invited speaker at the 5th European Congress of Mathematics (Krakow, 2012); plenary speaker at the 6th European Congress of Mathematics (Berlin, 2016)
 
Lecture 2 ——Stable homotopy groups of spheres
Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Speaker: Prof. Guozhen Wang,  Shanghai Center for Mathematical Sciences, Fudan University.
Abstract: We will discuss the current state of knowledge of stable homotopy groups of spheres. We describe a computational method using motivic homotopy theory, viewed as a deformation of classical homotopy theory. This yields a streamlined computation of the first 61 stable homotopy groups and gives information about the stable homotopy groups in dimensions 62 through 90. As an application, we determine the groups of homotopy spheres that classify smooth structures on spheres through dimension 90, except for dimension 4. The method relies more heavily on machine computations than previous methods and is therefore less prone to error. The main mathematical tool is the Adams spectral sequence. 
Bio: Guozhen Wang received PhD degree from MIT in 2015. From 2016, he is working at Shanghai Center for Mathematical Sciences, Fudan University. His research field is algebraic topology, including stable and unstable homotopy groups, applications of computers in homotopy theory, motivic homotopy theory and topological cyclic homology.

 

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Lecture Series X —— November 20th, 2020 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/D258CE3FD7B6994E558251263993EFA6
Valid Until:2026-04-30 23:59

 

Lecture 1 —— Right-angled polytopes, hyperbolic manifolds and torus actions

Speaker:Taras Panov, Moscow State University, Russia

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract: A combinatorial 3-dimensional polytope P can be realized in Lobachevsky 3-space with right dihedral angles if and only if it is simple, flag and does not have 4-belts of facets. This criterion was proved in the works of A.Pogorelov and E.Andreev of the 1960s. We refer to combinatorial 3 polytopes admitting a right-angled realisation in Lobachevsky 3-space as Pogorelov polytopes. The Pogorelov class contains all fullerenes, i.e. simple 3-polytopes with only 5-gonal and 6-gonal facets. There are two families of smooth manifolds associated with Pogorelov polytopes. The first family consists of 3-dimensional small covers (in the sense of M.Davis and T.Januszkiewicz) of Pogorelov polytopes P, also known as hyperbolic3-manifolds of Loebell type. These are aspherical 3-manifolds whose fundamental groups are certain extensions of abelian 2-groups by hyperbolic right-angled reflection groups in the facets of P. The second family consists of 6-dimensional quasi toric manifolds over Pogorelov polytopes. These are simply connected 6-manifolds with a 3-dimensional torus action and orbit space P. Our main result is that both families are cohomologically rigid, i.e. two manifolds M and M' from either family are diffeomorphic if and only if their cohomology rings are isomorphic. We also prove that a cohomology ring isomorphism implies an equivalence of characteristic pairs; in particular, the corresponding polytopes P and P' are combinatorially equivalent. This leads to a positive solution of a problem of A.Vesnin (1991) on hyperbolic Loebell manifolds, and implies their full classification. Our results are intertwined with classical subjects of geometry and topology such as combinatorics of 3-polytopes, the Four Colour Theorem, aspherical manifolds, a diffeomorphism classification of 6-manifolds and invariance of Pontryagin classes. The proofs use techniques of toric topology.
This is a joint work with V. Buchstaber, N. Erokhovets, M. Masuda and S.Park.
 
Bio: Higher geometry and topology chair, Professor. Research interests: Algebraic and differential topology, cobordism theories, toric topology. Honors: I. I. Shuvalov Prize, 1st degree, Moscow State University (2013), Moscow Mathematical Society award (2004).

 

Lecture 2 —— Finite covers of 3-manifolds

Speaker:Yi Liu, Beijing International Center for Mathematical Research.

Time: 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Abstract: In this talk, I will discuss some developments in 3-manifold topology of this century regarding finite covering spaces. These developments led to the resolution of Thurston’s virtual Haken conjecture and other related conjectures around 2012. Since then, people have been seeking for new applications of those techniques and their combination with other branches of mathematics.

Bio:Yi Liu is a professor at Beijing International Center for Mathematical Research (BICMR) in Peking University. His research interest lies primarily in 3-manifold topology and hyperbolic geometry. He received his Ph.D. degree in 2012 in University of California at Berkeley. In 2017, he received the Qiushi Outstanding Young Scholar Award. He has been a principal investigator of the NSFC Outstanding Young Scholar since 2019. Below are some selected research works of Yi Liu: (1) proving J. Simon’s conjecture about knot groups (joint with I. Agol, 2012); (2) resolving fundamental properties of the L2 Alexander torsion for 3-manifolds,  (2017); (3) proving C. T. McMullen’s conjecture about virtual homological spectral radii of surface automorphisms (2020).

 

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Lecture Series Ⅸ ——November 6th, 2020 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/18091C862640B23DC5A05E771BACB4B9
Valid Until:2026-04-30 23:59

 

Lecture 1 —— Spectrum rigidity and integrability for Anosov diffeomorphisms.

Speaker:Assistant Prof. Yi Shi, School of Mathematical Sciences, Peking University

Time: 16:00-17:00 Beijing time (11:00-12:00 Moscow time)

Abstract:

Bio: Yi Shi obtained PhD from Peking University and Universite de Bourgogne in 2014, and then did postdoc in IMPA. He is now an assistant professor in School of Mathematical Sciences at Peking University. His research field is differentiable dynamical systems, including partially hyperbolic dynamics and singular star vector fields.

 

Lecture 2 —Аn application of algebraic topology and graph theory in microeconomics

Speaker:Lev Lokutsievskiy (Steklov Mathematical Institute of RAS)

Time:17:00-18:00 Beijing time (12:00-13:00 Moscow time)
Abstract:One of the important questions in mechanism design is the implementability of allocation rules. An allocation rule is called implementable if for any agent, benefit from revealing its true type is better than benefit from lying. I’ll show some illustrative examples.
Obviously, some allocation rules are not implementable. Rochet’s theorem states that an allocation rule is implementable iff it is cyclically monotone. During the talk, I’ll present a new convenient topological condition that guarantees that cyclic monotonicity is equivalent to ordinary monotonicity. The last one is easy to check (in contrary to cyclic one). Graph theory and algebraic topology appear to be very useful here.

Bio: Lokutsievskiy L.V. is a specialist in geometric optimal control theory. He proved his habilitation thesis in 2015. Starting from 2016 he works at Steklov Mathematical Institute as a leading researcher.

 

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Lecture Series Ⅷ ——October 23th, 2020 (18:15-20:15 Beijing time, 13:15-15:15 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/37E312BF51E4B5ACEEA83926427C8670
Valid Until:2026-04-30 23:59

 

Lecture 1 - Topological cyclic homology for p-adic local fields.

Speaker: Prof. Ruochuan Liu, School of Mathematical Sciences, Peking University

Time: 18:15-19:15 Beijing time (13:15-14:15 Moscow time)

Abstract: We introduce a new approach to compute topological cyclic homology using the descent spectral sequence and the algebraic Tate spectral sequence. We carry out computations in the case of a p-adic local field with coefficient Fp. Joint work with Guozhen Wang.

Bio: Ruochuan Liu is working on p-adic aspects of arithmetic geometry and number theory, especially p-adic Hodge theory, p-adic automophic forms and p-adic Langlands program. He got his PhD from MIT at 2008. After several postdoc experience at Paris 7, McGill, IAS and Michigan, he joined the Beijing International Center for Mathematical Research at 2012. Starting from this year, he holds professorship at the School of Mathematical Sciences of Peking University.

 

Lecture 2 — Additive divisor problem and Applications

Speaker: Dimitry Frolenkov, Steklov Mathematical Institute (Moscow) 

Time: 19:15-20:15 Beijing time (14:15-15:15 Moscow time)

Abstract: Additive Divisor Problem (ADP) is concerned with finding an asymptotic formula for the sum $\sum_{n<X}d(n)d(n+a)$, where $d(n)=\sum_{d|n}1$ is the divisor function. Surprisingly, the ADP arises naturally in quite different problems of number theory. For example, it is related to the investigation of the 4th moment of the Riemann zeta-function, the second moment of automorphic $L$-functions and the mean values of the length of continued fractions. In the talk, I will describe the ADP and its applications.

Bio: Dmitry Frolenkov received his PhD degree from Steklov Mathematical Institute in 2013. Starting from 2014 he works at Steklov Mathematical Institute as a senior researcher.  Besides he got the RAS award for young scientists of Russia. His research interests are centered around an analytic number theory with a special emphasis on the theory of L-functions associated to automorphic forms.

 
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Second activity: Online conference Algebraic geometry and arithmetic 
The conference is on the occassion of the 70-th anniversary of our friend and colleague Vyacheslav Valentinovich Nikulin, to celebrate his huge contributions to the theory of K3 surfaces and other areas of geometry and arithmetic including reflections groups, automorphic forms and infinite-dimensional Lie algebras. The topics covered at the conference reflect the mathematical interests of V.V. Nikulin.
Conference websitehttp://mathnet.ru/eng/conf1697
 

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Lecture Series Ⅶ - October 16th, 2020 
(17:30-19:30 Beijing time, 12:30-14:30 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/CD2C01E30B99227AAF28668DE073F517
Valid Until:2026-04-30 23:59


Lecture 1 -  Restriction of unitary representations of Spin(N,1) to parabolic subgroups
Speaker: Prof. Yu Jun, Beijing International Center for Mathematical Research
Time:17:30-18:30 Beijing time (12:30-13:30 Moscow time)
Abstract: The orbit method predicts a relation between restrictions of irreducible unitary representations and projections of corresponding coadjoint orbits. In this talk we will discuss branching laws for unitary representations of Spin(N,1) restricted to parabolic subgroups and the corresponding orbit geometry. In particular, we confirm Duflo's conjecture in this setting. This is a joint work with Gang Liu (Lorraine) and Yoshiki Oshima (Osaka).

Bio: Jun Yu obtained PhD from ETH Zurich in 2012, and then did postdoc in IAS Princeton and MIT. He is now an assistant professor in Beijing international center for mathematical research at Peking University. His research field is representation theory and Langlands program, including the branching rule problem, the orbit method philosophy, and the beyond endoscopy program. 

Lecture 2: Characterizing homogeneous rational projective varieties with Picard number 1 by their varieties of minimal rational tangents.

Speaker: Prof. Dmitry Timashev, Moscow State University
Time:18:30-19:30 Beijing time (13:30-14:30 Moscow Time)
Abstract: It is well known that rational algebraic curves play a key role in the geometry of complex projective varieties, especially of Fano manifolds. In particular, on Fano manifolds of Picard number (= the 2nd Betti number) one, which are sometimes called "unipolar", one may consider rational curves of minimal degree passing through general points. Tangent directions of minimal rational curves through a general point $x$ in a unipolar Fano manifold $X$ form a projective subvariety $\mathcal{C}_{x,X}$ in the projectivized tangent space $\mathbb{P}(T_xX)$, called the variety of minimal rational tangents (VMRT).

In 90-s J.-M. Hwang and N. Mok developed a philosophy declaring that the geometry of a unipolar Fano manifold is governed by the geometry of its VMRT at a general point, as an embedded projective variety. In support of this thesis, they proposed a program of characterizing unipolar flag manifolds in the class of all unipolar Fano manifolds by their VMRT. In the following decades a number of partial results were obtained by Mok, Hwang, and their collaborators.

Recently the program was successfully completed (J.-M. Hwang, Q. Li, and the speaker). The main result states that a unipolar Fano manifold $X$ whose VMRT at a general point is isomorphic to the one of a unipolar flag manifold $Y$ is itself isomorphic to $Y$. Interestingly, the proof of the main result involves a bunch of ideas and techniques from "pure" algebraic geometry, differential geometry, structure and representation theory of simple Lie groups and algebras, and theory of spherical varieties (which extends the theory of toric varieties).

 

Bio: Dmitry Timashev recieved PhD degree from Moscow State University in 1997. From 1997, he is working at the Department of Higher Algebra in the Faculty of Mathematics and Mechanics, Moscow State University, currently at the position of associate professor. His research interests include Lie groups and Lie algebras, algebraic transformation groups and equivariant algebraic geometry, representation theory and invariant theory.

 

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Lecture Series VI - September 25th, 2020 (16:00-18:00 Beijing time, 11:00-13:00 Moscow time)


Recording: https://disk.pku.edu.cn:443/link/9FA7C0224D4364D456419199A4373EF7
Valid Until:2026-04-30 23:59

Lecture 1 -  Geometric description of the Hochschild cohomology of Group Algebras
Speaker: A. S. Mishchenko (Lomonosov Moscow State University)
Time: 2020-09-25 16:00-17:00 Beijing time (11:00-12:00 Moscow time)
Abstract
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Bio
Professor A.S. Mischenko graduated from Moscow State University in 1965. He became a Professor of the Department of Higher Geometry and Topology, Faculty of Mechanics and Mathematics of this University in 1979. He also holds a position of Leading researcher at the Mathematical Steklov Institute. He is a Honored Professor of Moscow University since 2006. 
His research interests include geometry and topology and their applications. The main direction of his work is related to the study and application of algebraic and functional methods in the theory of smooth manifolds.

 

Lecture 2 -   Unipotent representations and quantization of classical nilpotent varieties
Speaker: Prof. Daniel Wong (黄家裕), Chinese University of Hongkong at Shenzhen. 

Time: 2020-09-25 17:00-18:00 Beijing time (12:00-13:00 Moscow time)

Bio: Graduated at Cornell University in 2013. Research area is on Representation theory of real reductive Lie groups.  

 

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Lecture Series V - July 10th, 2020 (20:00-22:00 Beijing time, 15:00-17:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/167BD5B7868DBD2425132A8F522E4B7C
Valid Until:2026-04-30 23:59


Lecture 1 - Limits of the Boltzmann equation.
Speaker: Feimin Huang, Academy of Mathematics and Systems Science, CAS, China
Time: 2020-07-10 20:00-21:00 Beijing time (15:00-16:00 Moscow time)
Abstract: In this talk, I will present recent works on the hydrodynamic limits to the generic Riemann solutions to the compressible Euler system from the Boltzmann equation.
Bio: Prof. Huang, Feimin got Ph. D in Chinese Academy Sinica in 1997,and then did postdoc in ICTP, Italy and Osaka University. His research field is hyperbolic equations and conservative laws, including fluid dynamical systems, Navier-Stokes equations, and other various Partial Differential Equations. He was awarded the SIAM Outstanding Paper Prize by Society of American Industrial and Applied Mathematics in 2004. He won the Second Prize of National Natural Science Award in 2013. 

Lecture 2 - On the geometric solutions of the Riemann problem for one class of systems of conservation laws.
Speaker: Vladimir Palin, Moscow State University
Time: 2020-07-10 21:00-22:00 Beijing time (16:00-17:00 Moscow time)
Abstract: We consider the Riemann problem for a system of conservation laws. For non-strictly hyperbolic in the sense of Petrovskii step-like systems, a new method of constructing a solution is described. The proposed method allows us to construct a unique solution to the Riemann problem, which for each $t$ is a picewise smooth function of $x$ with discontinuities of the first kind. Moreover, for the scalar conservation law, the solution constructed by the proposed method coincides with the known admissible solution.
Bio: Vladimir Palin recieved higher education degree from Moscow State University in 2005, PhD degree from Moscow State University in 2009. He is now a senior lecturer in the Faculty of Mathematics and Mechanics, Moscow State University. His research interests include hyperbolic equations and systems, conservation laws and matrix equations.

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Lecture Series IV - June 26th, 2020 (20:00-22:00 Beijing time, 15:00-17:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/A5C7E39DAC87BAEEAEBA5CD1EBED76E0
Valid Until:2026-04-30 23:59

 

Lecture 1 - Tying Knots in Fluids

Speaker: Prof. Yue Yang, Department of Mechanics and Engineering Science, College of Engineering, Peking University,Beijing
Time: 2020-06-26 20:00-21:00 Beijing time (15:00-16:00 Moscow time)
Abstract:
We develop a general method for constructing knotted vortex/magnetic tubes with the finite thickness, arbitrary shape, and tunable twist. The central axis of the knotted tubes is determined by a given smooth and non-degenerated parametric equation. The helicity of the knotted tubes can be explicitly decomposed into the writhe, localized torsion, and intrinsic twist. We construct several knotted vortex/magnetic tubes with various geometry and topology, and investigate the effect of twist on their evolution in hydrodynamic or magnetohydrodynamic flows using direct numerical simulation. In addition, we illustrate a knot cascade of magnetic field lines through the stepwise reconnection of a pair of orthogonal helical flux tubes with opposite chirality.
Bio:
Yue Yang received BE degree from Zhejiang University in 2004, MS degree from the Institute of Mechanics, Chinese Academy of Sciences in 2007, and PhD degree from California Institute of Technology in 2011, then he was sponsored by the CEFRC Fellowship for postdoc research at Princeton University and Cornell University. Yang joined the Department of Mechanics and Engineering Science in College of Engineering, Peking University in 2013, and was promoted to full professor in 2020. He received the “National Distinguished Young Researcher” award and “Qiu Shi Outstanding Young Scholar Award”. His research interests include turbulence, transition, and combustion.


Lecture 2 - Supercomputer simulations of aerodynamics and aeroacoustics problems using high-accuracy schemes on unstructured meshes.
Speaker: Prof. Andrey Gorobets, Keldysh Institute of Applied Mathematics of RAS, Moscow
Time: 2020-06-26 21:00-22:00 Beijing time (16:00-17:00 Moscow time)
Abstract:
This talk is devoted to scale-resolving simulations of compressible turbulent flows using edge-based high-accuracy methods on unstructured mixed-element meshes. The focus is on parallel computing. Firstly, the family of edge-based schemes that we are developing will be outlined. Then our simulation code NOISEtte will be presented. It has multilevel MPI+OpenMP+OpenCL parallelization for a wide range of hybrid supercomputer architectures. A description of the parallel algorithm will be provided. Finally, our supercomputer simulations of aerodynamics and aeroacoustics problems will be demonstrated. 
Bio:
Andrey Gorobets graduated from Moscow State University in 2003. He then outlived three thesis defenses: 2007, Candidate of Sciences (к. ф.-м. н., equivalent to Ph.D.) at IMM RAS; 2008, European Ph.D. degree at UPC, Barcelona, Spain; 2015, Doktor nauk (д. ф.-м. н., higher doctoral degree) at the Keldysh Institute of Applied Mathematics of RAS (KIAM), Moscow, Russia. He is now a leading researcher at KIAM. His work is focused on algorithms and software for large-scale supercomputer simulations of turbulent flows.

 

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Lecture Series III - June 12th, 2020 (20:00-22:00 Beijing time, 15:00-17:00 Moscow time)

 

Lecture 1 - Slopes of modular forms and ghost conjecture of Bergdall and Pollack

Speaker:Prof. Xiao Liang (Beijing International Center for Math. Research )
Time: 2020-06-12 20:00-21:00 Beijing time (15:00-16:00 Moscow time)
Abstract: In classical theory, slopes of modular forms are p-adic valuations of the eigenvalues of the Up-operator.  On the Galois side, they correspond to the p-adic valuations of eigenvalues of the crystalline Frobenius on the Kisin's crystabelian deformations space. I will report on a joint work in progress in which we seems to have proved a version of the ghost conjecture of Bergdall and Pollack. This has many consequences in the classical theory, such as some cases of Gouvea-Mazur conjecture, and some hope towards understanding irreducible components of eigencurves. On the Galois side, our theorem can be used to prove certain integrality statement on slopes of crystalline Frobenius on Kisin's deformation space, as conjectured by Breuil-Buzzard-Emerton.  This is a joint work with Ruochuan Liu, Nha Truong, and Bin Zhao.

 

Lecture 2 - Higher-dimensional Contou-Carrere symbols

Speaker:Prof. RAS Denis V. Osipov (Steklov Mathematical Institute of Russian Academy of Sciences)

Time: 2020-06-12 21:00-22:00 Beijing time (16:00-17:00 Moscow time)
Abstract: The classical Contou-Carrere symbol is the deformation of the tame symbol, so that residues and higher Witt symbols naturally appear from the Contou-Carrere symbol. This symbol was introduced by C. Contou-Carrere itself and by P. Deligne. It satisfies the reciprocity laws. In my talk I will survey on the higher-dimensional generalization of the Contou-Carrere symbol. The n-dimensional Contou-Carrere symbol naturally appears from the deformation of a full flag of subvarieties on an n-dimensional algebraic variety and it is also related with the Milnor K-theory of iterated Laurent series over a ring. The talk is based on joint papers with Xinwen Zhu (when n=2) and with Sergey Gorchinskiy (when n>2).

 

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Lecture Series II - May 29th 2020 (20:00-22:00 Beijing time, 15:00-17:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/D369C31F18FD26B1F910B4648F4F6C67
Valid Until2026-04-30 23:59

 

Lecture 1 - Geometry of Landau--Ginzburg models.

Speaker:Prof. Victor V. Przyjalkowski (Steklov Mathematical Institute of Russian Academy of Sciences)
Time:2020-05-29 20:00-21:00 Beijing time (15:00-16:00 Moscow time)

Abstract: We discuss geometric and numerical properties of Landau--Ginzburg models of Fano varieties that reflect geometric and numerical properties of the initial Fano varieties. The main example is the threefold case.

 

Lecture 2 - Deformation theory of Schroedinger equation arising from singularity theory

Speaker: Prof. Huijun Fan (Peking University)

Time:2020-05-29 21:00-22:00 Beijing time (16:00-17:00 Moscow time)

Abstract: Mirror symmetry phenomenon relates many mathematical branches in a mysterious way. For example, it is conjectured that the quantum geometry of a Calabi-Yau hypersurface is equivalent to the quantum singularity theory of the corresponding defining function. When we consider the complex structure deformation of the two sides, we get the B model mirror conjecture, where the exciting structures of deformation moduli space, Gauss Manin connection, period mapping and etc.will appear. In this lecture, I will report another way to study the deformation theory of singularity via Schroedinger equation. By study the spectral theory of Schroedinger equation, we can build the variation of Hodge theory, Gauss-Manin connection by wave function, Frobenius manifold for some cases and even BCOV type torsion invariants for singularity.
 

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Lecture Series I - May 15th 2020 (20:00-22:00 Beijing time, 15:00-17:00 Moscow time)

 

Recording: https://disk.pku.edu.cn:443/link/AC9C06289D33D936B486150C6AD3876F
Valid Until2026-04-30 23:59

 

Lecture 1 - Representation volumes and dominations of 3-manifolds

Speaker:Shicheng Wang (Peking University)
Time:2020-05-15 20:00-21:00 Beijing time (15:00-16:00 Moscow time)

Abstract: We will discuss recent results on virtual representation volumes and finiteness of the mapping degree set on 3-manifolds.

 

Lecture 2 - Topology of integrable systems on 4-manifolds

Speaker:Elena Kudryavtseva (Moscow State University)

Time:2020-05-15 21:00-22:00 Beijing time (16:00-17:00 Moscow time)

Abstract: We will give a survey on the topology of integrable Hamiltonian systems on 4-manifolds. Open questions and problems will be also discussed. Recall that, from a topological point of view, an integrable Hamiltonian system can be treated as a singular Lagrangian fibration on a smooth symplectic 2n-manifold whose generic fibres are n-dimensional tori. By a singularity, we mean either a singular point or a singular fibre of the fibration. The topological structure of such singularities is very important for understanding the dynamics of integrable systems both globally and locally. Our goal is to describe topological invariants of such singularities and obtain their classification up to fibrewise homeomorphism (for time being we forget about symplectic structure). The next step is to combine these singularities together to study the global structure of the fibration. For many integrable systems, this structure is completely determined by topological properties of singularities.

Slides:https://disk.pku.edu.cn:443/link/3FFA6A7EF0B27A568A9C20B99FA076F6 

 

 

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Organized by:

 

◆  Sino-Russian Mathematics Center
◆  Mathematics Department, School of Mathematical Sciences (SMS), Peking University
◆  Beijing International Center for Mathematical Research (BICMR), Peking University
◆  Department of Mechanics and Engineering Science, College of Engineering (EC), Peking University
◆  Mathematics Institute of Academy of Mathematics and Systems Science of Chinese Academy of Sciences (AMSS)
◆  Moscow State University (MSU)
◆  Steklov Mathematical Institute (MIAN)
◆  Steklov International Mathematical Center
◆  Moscow Center of Fundamental and Applied Mathematics
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https://mathcenter.ru/en

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