{"title":"Theory of homotopes with applications to mutually unbiased bases, harmonic analysis on graphs, and perverse sheaves","authors":"A. Bondal, I. Zhdanovskiy","doi":"10.1070/RM9983","DOIUrl":"https://doi.org/10.1070/RM9983","url":null,"abstract":"This paper is a survey of contemporary results and applications of the theory of homotopes. The notion of a well-tempered element of an associative algebra is introduced, and it is proved that the category of representations of the homotope constructed by a well-tempered element is the heart of a suitably glued -structure. The Hochschild and global dimensions of homotopes are calculated in the case of well-tempered elements. The homotopes constructed from generalized Laplace operators in Poincaré groupoids of graphs are studied. It is shown that they are quotients of Temperley–Lieb algebras of general graphs. The perverse sheaves on a punctured disc and on a 2-dimensional sphere with a double point are identified with representations of suitable homotopes. Relations of the theory to orthogonal decompositions of the Lie algebras into a sum of Cartan subalgebras, to classifications of configurations of lines, to mutually unbiased bases, to quantum protocols, and to generalized Hadamard matrices are discussed. Bibliography: 56 titles.","PeriodicalId":49582,"journal":{"name":"Russian Mathematical Surveys","volume":"76 1","pages":"195 - 259"},"PeriodicalIF":0.9,"publicationDate":"2020-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45792580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The Dickman–Goncharov distribution","authors":"S. Molchanov, V. Panov","doi":"10.1070/RM9976","DOIUrl":"https://doi.org/10.1070/RM9976","url":null,"abstract":"In the 1930s and 40s, one and the same delay differential equation appeared in papers by two mathematicians, Karl Dickman and Vasily Leonidovich Goncharov, who dealt with completely different problems. Dickman investigated the limit value of the number of natural numbers free of large prime factors, while Goncharov examined the asymptotics of the maximum cycle length in decompositions of random permutations. The equation obtained in these papers defines, under a certain initial condition, the density of a probability distribution now called the Dickman–Goncharov distribution (this term was first proposed by Vershik in 1986). Recently, a number of completely new applications of the Dickman–Goncharov distribution have appeared in mathematics (random walks on solvable groups, random graph theory, and so on) and also in biology (models of growth and evolution of unicellular populations), finance (theory of extreme phenomena in finance and insurance), physics (the model of random energy levels), and other fields. Despite the extensive scope of applications of this distribution and of more general but related models, all the mathematical aspects of this topic (for example, infinite divisibility and absolute continuity) are little known even to specialists in limit theorems. The present survey is intended to fill this gap. Both known and new results are given. Bibliography: 62 titles.","PeriodicalId":49582,"journal":{"name":"Russian Mathematical Surveys","volume":"75 1","pages":"1089 - 1132"},"PeriodicalIF":0.9,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41688728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Spinning tops and magnetic orbits","authors":"S. Novikov","doi":"10.1070/RM9977","DOIUrl":"https://doi.org/10.1070/RM9977","url":null,"abstract":"A number of directions were initiated by the author and his students in their papers of 1981–1982. However, one of them, concerning the properties of closed orbits on the sphere and in the groups and , has not been sufficiently developed. This paper revives the discussion of these questions, states unsolved problems, and explains what was regarded as fallacies in old papers. In general, magnetic orbits have been poorly discussed in the literature on dynamical systems and theoretical mechanics, but Grinevich has pointed out that in theoretical physics one encounters similar situations in the theory related to particle accelerators such as proton cyclotrons. It is interesting to look at Chap. III of Landau and Lifshitz’s Theoretical physics, vol. 2, Field theory (Translated into English as The classical theory of fields [12]. where mathematical relatives of our situations occur, but the physics is completely different and there are actual strong magnetic fields. Bibliography: 12 titles.","PeriodicalId":49582,"journal":{"name":"Russian Mathematical Surveys","volume":"75 1","pages":"1133 - 1141"},"PeriodicalIF":0.9,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44194390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Bifurcations in spatially distributed chains of two-dimensional systems of equations","authors":"S. Kaschenko","doi":"10.1070/RM9986","DOIUrl":"https://doi.org/10.1070/RM9986","url":null,"abstract":"u̇j = Auj + F (uj) + D[uj+1− 2uj + uj−1], j = 1, . . . , N ; u0 ≡ uN , uN+1 ≡ u1. (2) We associate the element uj(t) with the value of a function u(t, xj) of two variables, where xj = 2πjN−1 is the angular coordinate. The main assumption is that the number N of elements in (2) is sufficiently large, so that the parameter ε = 2πN−1 is sufficiently small: 0 < ε ≪ 1. This gives reason to switch from the discrete system (2) to the following system, which is continuous with respect to the spatial variable x:","PeriodicalId":49582,"journal":{"name":"Russian Mathematical Surveys","volume":"75 1","pages":"1153 - 1155"},"PeriodicalIF":0.9,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42177421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Braverman, V. Buchstaber, M. Gromov, V. Ivrii, Y. Kordyukov, P. Kuchment, V. Maz'ya, S. Novikov, T. Sunada, L. Friedlander, A. Khovanskii
{"title":"Mikhail Aleksandrovich Shubin","authors":"M. Braverman, V. Buchstaber, M. Gromov, V. Ivrii, Y. Kordyukov, P. Kuchment, V. Maz'ya, S. Novikov, T. Sunada, L. Friedlander, A. Khovanskii","doi":"10.1070/RM9968","DOIUrl":"https://doi.org/10.1070/RM9968","url":null,"abstract":"The prominent mathematician Mikhail Aleksandrovich Shubin passed away after a long illness on 13 May 2020. He was born on 19 December 1944 in Kuibyshev (now Samara) and raised by his mother and grandmother. His mother, Maria Arkadievna, was an engineer at the State Bearing Factory, where she was hired in 1941 after graduating from the Faculty of Mechanics and Mathematics at the Moscow State University. At that time the factory was evacuated from Moscow to Kuibyshev. She worked at the factory for many years as the Head of the Physics of Metals Laboratory. Later, she defended her Ph.D. thesis and moved to Kuibyshev Polytechnical Institute, where she worked as an associate professor. In his school years Shubin was mainly interested in music. He had absolute pitch. After finishing music school, he seriously considered entering a conservatory. However, in high school he developed an interest to mathematics, was successful in olympiads, and eventually decided to apply to the Faculty of Mechanics and Mathematics at the Moscow State University. He was admitted there in 1961. When the time came to choose an adviser, he became a student of M. I. Vishik. After graduating, he began postgraduate work there, and in 1969 defended his Ph.D. thesis. In the thesis he derived formulae for the index of matrix-valued Wiener–Hopf operators. In particular, for the study of families of such operators, he had to generalize a theorem of Birkhoff stating that a continuous matrix-valued function M(z) defined on the unit circle |z| = 1 can be factored as M(z) = A+(z)D(z)A−(z), where A+(z) and A−(z) are continuous and have analytic continuations to the interior of the unit circle and its exterior (infinity included), respectively, and D(z) is a diagonal matrix with entries zj on the diagonal, with integer nj . Shubin considered the problem of what happens when the matrix M depends continuously on an additional parameter t. The Birkhoff factorization cannot be made continuous","PeriodicalId":49582,"journal":{"name":"Russian Mathematical Surveys","volume":"75 1","pages":"1143 - 1152"},"PeriodicalIF":0.9,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46819886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Bolotin, A. V. Borisov, A. Karapetyan, B. Kashin, E. I. Kugushev, Anatolii Iserovich Neishtadt, Dmitri Orlov, D. Treschev
{"title":"Valerii Vasil’evich Kozlov","authors":"S. Bolotin, A. V. Borisov, A. Karapetyan, B. Kashin, E. I. Kugushev, Anatolii Iserovich Neishtadt, Dmitri Orlov, D. Treschev","doi":"10.1070/RM9949","DOIUrl":"https://doi.org/10.1070/RM9949","url":null,"abstract":"On 1 January 2020 the prominent researcher and academician of the Russian Academy of Sciences Valerii Vasil’evich Kozlov observed his 70th birthday. Kozlov has made fundamental contributions to diverse areas of mathematics and mechanics: the theory of Hamiltonian systems, stability theory, the mechanics of non-holonomic systems, statistical mechanics. He has published about 300 papers on mathematics and mechanics and 8 monographs which are now classical. In this one article it is impossible to give even a brief account of all the directions of his research. Kozlov was born on 1 January 1950 in the village of Kostyli, in the Mikhailovskoe District of the Ryazan Oblast. His mother Ol’ga Arkhipovna was a teacher of mathematics, and his father Vasilii Nestorovich was a train-driver, and a veteran of World War II, from the first days when the Soviet Union was attacked until Victory Day. Valerii started his early school education in his native small village (where nobody lives now). There was only a primary school there, with one female teacher, who gave simultaneous lessons to grades I and III in the morning and to grades II and IV in the afternoon. As an 8-year boy, Kozlov moved with his parents to Lyublino-Dachnaya, close to Moscow. When the Moscow Ring Road was built (in 1961) this settlement, like many others, found itself inside the expanding Moscow. In this way Kozlov became a Moscow resident. During his last two years in secondary school he became deeply interested in mathematics and physics. Three times a week he travelled to lessons at a volunteer physics-mathematics evening school under the auspices of the Bauman Moscow State Technical School (now Technical University). This proved to be a remarkable school! (It was founded in 1962 and still exists.) Most teachers were students","PeriodicalId":49582,"journal":{"name":"Russian Mathematical Surveys","volume":"75 1","pages":"1165 - 1180"},"PeriodicalIF":0.9,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49615312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Iterated Laurent series over rings and the Contou-Carrère symbol","authors":"S. Gorchinskiy, D. Osipov","doi":"10.1070/RM9975","DOIUrl":"https://doi.org/10.1070/RM9975","url":null,"abstract":"This article contains a survey of a new algebro-geometric approach for working with iterated algebraic loop groups associated with iterated Laurent series over arbitrary commutative rings and its applications to the study of the higher-dimensional Contou-Carrère symbol. In addition to the survey, the article also contains new results related to this symbol. The higher-dimensional Contou-Carrère symbol arises naturally when one considers deformation of a flag of algebraic subvarieties of an algebraic variety. The non-triviality of the problem is due to the fact that, in the case 1$?> , for the group of invertible elements of the algebra of -iterated Laurent series over a ring, no representation is known in the form of an ind-flat scheme over this ring. Therefore, essentially new algebro-geometric constructions, notions, and methods are required. As an application of the new methods used, a description of continuous homomorphisms between algebras of iterated Laurent series over a ring is given, and an invertibility criterion for such endomorphisms is found. It is shown that the higher- dimensional Contou-Carrère symbol, restricted to algebras over the field of rational numbers, is given by a natural explicit formula, and this symbol extends uniquely to all rings. An explicit formula is also given for the higher-dimensional Contou-Carrère symbol in the case of all rings. The connection with higher-dimensional class field theory is described. As a new result, it is shown that the higher-dimensional Contou-Carrère symbol has a universal property. Namely, if one fixes a torsion-free ring and considers a flat group scheme over this ring such that any two points of the scheme are contained in an affine open subset, then after restricting to algebras over the fixed ring, all morphisms from the -iterated algebraic loop group of the Milnor -group of degree to the above group scheme factor through the higher-dimensional Contou-Carrère symbol. Bibliography: 67 titles.","PeriodicalId":49582,"journal":{"name":"Russian Mathematical Surveys","volume":"75 1","pages":"995 - 1066"},"PeriodicalIF":0.9,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48732400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fan Yang, Shenglong Ling, Yingxin Zhou, Yanan Zhang, Pei Lv, Sanling Liu, Wei Fang, Wenjing Sun, Liaoyuan A Hu, Longhua Zhang, Pan Shi, Changlin Tian
{"title":"Different conformational responses of the β<sub>2</sub>-adrenergic receptor-Gs complex upon binding of the partial agonist salbutamol or the full agonist isoprenaline.","authors":"Fan Yang, Shenglong Ling, Yingxin Zhou, Yanan Zhang, Pei Lv, Sanling Liu, Wei Fang, Wenjing Sun, Liaoyuan A Hu, Longhua Zhang, Pan Shi, Changlin Tian","doi":"10.1093/nsr/nwaa284","DOIUrl":"10.1093/nsr/nwaa284","url":null,"abstract":"<p><p>G protein-coupled receptors (GPCRs) are responsible for most cytoplasmic signaling in response to extracellular ligands with different efficacy profiles. Various spectroscopic techniques have identified that agonists exhibiting varying efficacies can selectively stabilize a specific conformation of the receptor. However, the structural basis for activation of the GPCR-G protein complex by ligands with different efficacies is incompletely understood. To better understand the structural basis underlying the mechanisms by which ligands with varying efficacies differentially regulate the conformations of receptors and G proteins, we determined the structures of β<sub>2</sub>AR-Gα<sub>s</sub>[Formula: see text]γ bound with partial agonist salbutamol or bound with full agonist isoprenaline using single-particle cryo-electron microscopy at resolutions of 3.26 Å and 3.80 Å, respectively. Structural comparisons between the β<sub>2</sub>AR-Gs-salbutamol and β<sub>2</sub>AR-Gs-isoprenaline complexes demonstrated that the decreased binding affinity and efficacy of salbutamol compared with those of isoprenaline might be attributed to weakened hydrogen bonding interactions, attenuated hydrophobic interactions in the orthosteric binding pocket and different conformational changes in the rotamer toggle switch in TM6. Moreover, the observed stronger interactions between the intracellular loop 2 or 3 (ICL2 or ICL3) of β<sub>2</sub>AR and Gα<sub>s</sub> with binding of salbutamol versus isoprenaline might decrease phosphorylation in the salbutamol-activated β<sub>2</sub>AR-Gs complex. From the observed structural differences between these complexes of β<sub>2</sub>AR, a mechanism of β<sub>2</sub>AR activation by partial and full agonists is proposed to provide structural insights into β<sub>2</sub>AR desensitization.</p>","PeriodicalId":49582,"journal":{"name":"Russian Mathematical Surveys","volume":"52 1","pages":"nwaa284"},"PeriodicalIF":16.3,"publicationDate":"2020-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11261663/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80828902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The spectral radius of a certain parametric family of functional operators","authors":"N. B. Zhuravlev, L. Rossovskii","doi":"10.1070/RM9967","DOIUrl":"https://doi.org/10.1070/RM9967","url":null,"abstract":"K e−ihξ dν(h) is the characteristic function of the measure ν. It was also shown that when (2) fails, there can be an infinite-dimensional kernel in this problem. The problem (1) is a natural generalization of boundary-value problems for elliptic differential-difference equations [5], [6] and functional-differential equations with contracted/extended independent variables [2], [3]. We note a connection between (possibly degenerate) elliptic functional-differential operators and Kato’s well-known problem of the square root of a regular accretive operator [6], [7].","PeriodicalId":49582,"journal":{"name":"Russian Mathematical Surveys","volume":"62 1","pages":"971 - 973"},"PeriodicalIF":0.9,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59005123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}