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COMBINATORIAL Bn-ANALOGUES of SCHUBERT POLYNOMIALS 0
TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 348, Number 9, September 1996 COMBINATORIAL Bn-ANALOGUES OF SCHUBERT POLYNOMIALS SERGEY FOMIN AND ANATOL N. KIRILLOV Abstract. Combinatorial Bn-analogues of Schubert polynomials and corre- sponding symmetric functions are constructed and studied. The development is based on an exponential solution of the type B Yang-Baxter equation that involves the nilCoxeter algebra of the hyperoctahedral group. 0. Introduction This paper is devoted to the problem of constructing type B analogues of the Schubert polynomials of Lascoux and Sch¨utzenberger (see, e.g., [L2], [M] and the literature therein). We begin with reviewing the basic properties of the type A polynomials, stating them in a form that would allow subsequent generalizations to other types. Let W = Wn be the Coxeter group of type An with generators s1, ... ,sn (that is, the symmetric group Sn+1). Let x1, x2, ... be formal variables. Then W naturally acts on the polynomial ring C[x1,...,xn+1] by permuting the variables. Let IW denote the ideal generated by homogeneous non-constant W -symmetric polynomials. By a classical result [Bo], the cohomology ring H(F ) of the flag variety of type A can be canonically identified with the quotient C[x1,...,xn+1]/IW .This ring is graded by the degree and has a distinguished linear basis of homogeneous cosets Xw modulo IW , labelled by the elements w of the group. Let us state for the record that, for an element w W of length l(w), ∈ (0) Xw is a homogeneous polynomial of degree l(w); X1=1; the latter condition signifies proper normalization. -
Combinatorial Topology and Applications to Quantum Field Theory
Combinatorial Topology and Applications to Quantum Field Theory by Ryan George Thorngren A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Mathematics in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Vivek Shende, Chair Professor Ian Agol Professor Constantin Teleman Professor Joel Moore Fall 2018 Abstract Combinatorial Topology and Applications to Quantum Field Theory by Ryan George Thorngren Doctor of Philosophy in Mathematics University of California, Berkeley Professor Vivek Shende, Chair Topology has become increasingly important in the study of many-body quantum mechanics, in both high energy and condensed matter applications. While the importance of smooth topology has long been appreciated in this context, especially with the rise of index theory, torsion phenomena and dis- crete group symmetries are relatively new directions. In this thesis, I collect some mathematical results and conjectures that I have encountered in the exploration of these new topics. I also give an introduction to some quantum field theory topics I hope will be accessible to topologists. 1 To my loving parents, kind friends, and patient teachers. i Contents I Discrete Topology Toolbox1 1 Basics4 1.1 Discrete Spaces..........................4 1.1.1 Cellular Maps and Cellular Approximation.......6 1.1.2 Triangulations and Barycentric Subdivision......6 1.1.3 PL-Manifolds and Combinatorial Duality........8 1.1.4 Discrete Morse Flows...................9 1.2 Chains, Cycles, Cochains, Cocycles............... 13 1.2.1 Chains, Cycles, and Homology.............. 13 1.2.2 Pushforward of Chains.................. 15 1.2.3 Cochains, Cocycles, and Cohomology......... -
Arxiv:Math/9912128V1 [Math.RA] 15 Dec 1999 Iigdiagrams
TOTAL POSITIVITY: TESTS AND PARAMETRIZATIONS SERGEY FOMIN AND ANDREI ZELEVINSKY Introduction A matrix is totally positive (resp. totally nonnegative) if all its minors are pos- itive (resp. nonnegative) real numbers. The first systematic study of these classes of matrices was undertaken in the 1930s by F. R. Gantmacher and M. G. Krein [20, 21, 22], who established their remarkable spectral properties (in particular, an n × n totally positive matrix x has n distinct positive eigenvalues). Earlier, I. J. Schoenberg [41] discovered the connection between total nonnegativity and the following variation-diminishing property: the number of sign changes in a vec- tor does not increase upon multiplying by x. Total positivity found numerous applications and was studied from many dif- ferent angles. An incomplete list includes: oscillations in mechanical systems (the original motivation in [22]), stochastic processes and approximation theory [25, 28], P´olya frequency sequences [28, 40], representation theory of the infinite symmetric group and the Edrei-Thoma theorem [13, 44], planar resistor networks [11], uni- modality and log-concavity [42], and theory of immanants [43]. Further references can be found in S. Karlin’s book [28] and in the surveys [2, 5, 38]. In this paper, we focus on the following two problems: (i) parametrizing all totally nonnegative matrices; (ii) testing a matrix for total positivity. Our interest in these problems stemmed from a surprising representation-theoretic connection between total positivity and canonical bases for quantum groups, dis- covered by G. Lusztig [33] (cf. also the surveys [31, 34]). Among other things, he extended the subject by defining totally positive and totally nonnegative elements for any reductive group. -
The Yang-Baxter Equation, Symmetric Functions, and Schubert Polynomials
DISCRETE MATHEMATICS ELSEVIER Discrete Mathematics 153 (1996) 123 143 The Yang-Baxter equation, symmetric functions, and Schubert polynomials Sergey Fomin a'b'*, Anatol N. Kirillov c a Department of Mathematics, Room 2-363B, Massachusetts Institute of Technolooy, Cambridge, MA 02139, USA b Theory of Aloorithms Laboratory, SPIIRAN, Russia c Steklov Mathematical Institute, St. Petersbur9, Russia Received 31 August 1993; revised 18 February 1995 Abstract We present an approach to the theory of Schubert polynomials, corresponding symmetric functions, and their generalizations that is based on exponential solutions of the Yang-Baxter equation. In the case of the solution related to the nilCoxeter algebra of the symmetric group, we recover the Schubert polynomials of Lascoux and Schiitzenberger, and provide simplified proofs of their basic properties, along with various generalizations thereof. Our techniques make use of an explicit combinatorial interpretation of these polynomials in terms of configurations of labelled pseudo-lines. Keywords: Yang-Baxter equation; Schubert polynomials; Symmetric functions 1. Introduction The Yang-Baxter operators hi(x) satisfy the following relations (cf. [1,7]): hi(x)hj(y) = hj(y)hi(x) if li -j[ >_-2; hi(x)hi+l (x + y)hi(y) = hi+l (y)hi(x + y)hi+l(X); The role the representations of the Yang-Baxter algebra play in the theory of quantum groups [9], the theory of exactly solvable models in statistical mechanics [1], low- dimensional topology [7,27,16], the theory of special functions, and other branches of mathematics (see, e.g., the survey [5]) is well known. * Corresponding author. 0012-365X/96/$15.00 (~) 1996--Elsevier Science B.V. -
Arxiv:2104.14530V2 [Math.RT]
REFLECTION LENGTH WITH TWO PARAMETERS IN THE ASYMPTOTIC REPRESENTATION THEORY OF TYPE B/C AND APPLICATIONS MAREK BOZEJKO,˙ MACIEJ DOŁ ˛EGA, WIKTOR EJSMONT, AND SWIATOSŁAW´ R. GAL ABSTRACT. We introduce a two-parameter function φq+,q− on the infinite hyperoctahedral group, which is a bivariate refinement of the reflection length. We show that this signed reflection function φq+,q− is positive definite if and only if it is an extreme character of the infinite hyperoctahedralgroup and we classify the correspondingset of parameters q+, q−. We construct the corresponding representations through a natural action of the hyperoctahedral group B(n) on the tensor product of n copies of a vector space, which gives a two-parameter analog of the classical construction of Schur–Weyl. We apply our classification to construct a cyclic Fock space of type B generalizing the one- parameter construction in type A found previously by Bozejko˙ and Guta. We also construct a new Gaussian operator acting on the cyclic Fock space of type B and we relate its moments with the Askey–Wimp–Kerov distribution by using the notion of cycles on pair-partitions, which we introduce here. Finally, we explain how to solve the analogous problem for the Coxeter groups of type D by using our main result. 1. INTRODUCTION Positive definite functions on a group G play a prominent role in harmonic analysis, opera- tor theory, free probability and geometric group theory. When G has a particularly nice struc- ture of combinatorial/geometric origin one can use it to construct positive definite functions which leads to many interesting properties widely applied in these fields. -
Cluster Algebras and Classical Invariant Rings
Cluster algebras and classical invariant rings by Kevin Carde A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Mathematics) in the University of Michigan 2014 Doctoral Committee: Professor Sergey Fomin, Chair Professor Gordon Belot, Professor Thomas Lam, Professor Karen E. Smith, Professor David E. Speyer ACKNOWLEDGEMENTS I would first like to thank my advisor, Sergey Fomin, for his support these past several years. Besides introducing me to this beautiful corner of combinatorics and providing mathematical guidance throughout, he has been unfailingly supportive even of my pursuits outside of research. I am tremendously grateful on both counts. I would also like to thank David Speyer, whose insight and interest in my work has been one of the best parts of my time at the University of Michigan. I am also grateful to him for suggesting to me a much shorter proof of the irreducibility of mixed invariants. His suggestion, rather than my longer, much less elegant original effort, appears as the end of the proof of Proposition 4.1. Besides these two major mathematical inspirations, I would like to thank the University of Michigan math department at large. From the wonderful people of the graduate office whose patience and care kept me on track on a number of ad- ministrative matters, to the precalculus and calculus coordinators I've worked with who helped spark in me a love of teaching, to the professors whose friendliness and enthusiasm come through both in and out of the classroom, to the graduate students who are always willing to work together through difficult problems (mathematical or otherwise!), everyone I've met here has contributed to the warm, collaborative environment of the department. -
January 2007 Prizes and Awards
January 2007 Prizes and Awards 4:25 P.M., Saturday, January 6, 2007 MATHEMATICAL ASSOCIATION OF AMERICA DEBORAH AND FRANKLIN TEPPER HAIMO AWARDS FOR DISTINGUISHED COLLEGE OR UNIVERSITY TEACHING OF MATHEMATICS In 1991, the Mathematical Association of America instituted the Deborah and Franklin Tepper Haimo Awards for Distinguished College or University Teaching of Mathematics in order to honor college or university teachers who have been widely recognized as extraordinarily successful and whose teaching effectiveness has been shown to have had influence beyond their own institutions. Deborah Tepper Haimo was president of the Association, 1991–1992. Citation Jennifer Quinn Jennifer Quinn has a contagious enthusiasm that draws students to mathematics. The joy she takes in all things mathematical is reflected in her classes, her presentations, her publications, her videos and her on-line materials. Her class assignments often include nonstandard activities, such as creating time line entries for historic math events, or acting out scenes from the book Proofs and Refutations. One student created a children’s story about prime numbers and another produced a video documentary about students’ perceptions of math. A student who had her for six classes says, “I hope to become a teacher after finishing my master’s degree and I would be thrilled if I were able to come anywhere close to being as great a teacher as she is.” Jenny developed a variety of courses at Occidental College. Working with members of the physics department and funded by an NSF grant, she helped develop a combined yearlong course in calculus and mechanics. She also developed a course on “Mathematics as a Liberal Art” which included computer discussions, writing assignments, and other means to draw technophobes into the course. -
Research Statement
Research Statement Nicholas Ovenhouse My research is mainly in the area of algebraic combinatorics, with strong connections to geometry and dynamical systems. Specically, I am interested in problems related to, and inspired by, the theory of cluster algebras, in particular those having to do with Poisson geometry and integrable systems. Below are summaries of some of my published results, along with some background. Possible directions of future research are also discussed. Cluster Algebras Cluster algebras are special kinds of commutative algebras. They are subrings of a fraction eld Q(x1; : : : ; xn) whose generators are dened by a recursive combinatorial procedure called mutation [FZ02]. One of the earliest and most basic results in the theory is what is known as the Laurent Phenomenon. It says that each of the generators (called cluster variables), which are, by denition, rational functions, are in fact always Laurent polynomials. It is therefore a point of interest to explicitly describe, combinatorially, the terms that occur in these Laurent polynomial expressions. One interesting class of cluster algebras come from two-dimensional triangulated surfaces [FST08]. The clus- ter variables represent coordinate functions on the decorated Teichmüller space of the surface. In this case several combinatorial interpretations of the Laurent polynomial expansions are known [Sch08] [Yur19] [MSW11]. The simplest case is that of a triangulated polygon. The cluster variables correspond to the diagonals of the polygon. For a given diagonal, Schier proved that the terms in the Laurent expansion are indexed by combinatorial objects called “T -paths”, which are certain types of paths drawn on the triangulation, which begin and end at the same endpoints as the given diagonal [Sch08]. -
2018 Leroy P. Steele Prizes
AMS Prize Announcements FROM THE AMS SECRETARY 2018 Leroy P. Steele Prizes Sergey Fomin Andrei Zelevinsky Martin Aigner Günter Ziegler Jean Bourgain The 2018 Leroy P. Steele Prizes were presented at the 124th Annual Meeting of the AMS in San Diego, California, in January 2018. The Steele Prizes were awarded to Sergey Fomin and Andrei Zelevinsky for Seminal Contribution to Research, to Martin Aigner and Günter Ziegler for Mathematical Exposition, and to Jean Bourgain for Lifetime Achievement. Citation for Seminal Contribution to Research: Biographical Sketch: Sergey Fomin Sergey Fomin and Andrei Zelevinsky Sergey Fomin is the Robert M. Thrall Collegiate Professor The 2018 Steele Prize for Seminal Contribution to Research of Mathematics at the University of Michigan. Born in 1958 in Discrete Mathematics/Logic is awarded to Sergey Fomin in Leningrad (now St. Petersburg), he received an MS (1979) and Andrei Zelevinsky (posthumously) for their paper and a PhD (1982) from Leningrad State University, where “Cluster Algebras I: Foundations,” published in 2002 in his advisor was Anatoly Vershik. He then held positions at St. Petersburg Electrotechnical University and the Institute the Journal of the American Mathematical Society. for Informatics and Automation of the Russian Academy The paper “Cluster Algebras I: Foundations” is a of Sciences. Starting in 1992, he worked in the United modern exemplar of how combinatorial imagination States, first at Massachusetts Institute of Technology and can influence mathematics at large. Cluster algebras are then, since 1999, at the University of Michigan. commutative rings, generated by a collection of elements Fomin’s main research interests lie in algebraic com- called cluster variables, grouped together into overlapping binatorics, including its interactions with various areas clusters. -
Prizes and Awards
SAN DIEGO • JAN 10–13, 2018 January 2018 SAN DIEGO • JAN 10–13, 2018 Prizes and Awards 4:25 p.m., Thursday, January 11, 2018 66 PAGES | SPINE: 1/8" PROGRAM OPENING REMARKS Deanna Haunsperger, Mathematical Association of America GEORGE DAVID BIRKHOFF PRIZE IN APPLIED MATHEMATICS American Mathematical Society Society for Industrial and Applied Mathematics BERTRAND RUSSELL PRIZE OF THE AMS American Mathematical Society ULF GRENANDER PRIZE IN STOCHASTIC THEORY AND MODELING American Mathematical Society CHEVALLEY PRIZE IN LIE THEORY American Mathematical Society ALBERT LEON WHITEMAN MEMORIAL PRIZE American Mathematical Society FRANK NELSON COLE PRIZE IN ALGEBRA American Mathematical Society LEVI L. CONANT PRIZE American Mathematical Society AWARD FOR DISTINGUISHED PUBLIC SERVICE American Mathematical Society LEROY P. STEELE PRIZE FOR SEMINAL CONTRIBUTION TO RESEARCH American Mathematical Society LEROY P. STEELE PRIZE FOR MATHEMATICAL EXPOSITION American Mathematical Society LEROY P. STEELE PRIZE FOR LIFETIME ACHIEVEMENT American Mathematical Society SADOSKY RESEARCH PRIZE IN ANALYSIS Association for Women in Mathematics LOUISE HAY AWARD FOR CONTRIBUTION TO MATHEMATICS EDUCATION Association for Women in Mathematics M. GWENETH HUMPHREYS AWARD FOR MENTORSHIP OF UNDERGRADUATE WOMEN IN MATHEMATICS Association for Women in Mathematics MICROSOFT RESEARCH PRIZE IN ALGEBRA AND NUMBER THEORY Association for Women in Mathematics COMMUNICATIONS AWARD Joint Policy Board for Mathematics FRANK AND BRENNIE MORGAN PRIZE FOR OUTSTANDING RESEARCH IN MATHEMATICS BY AN UNDERGRADUATE STUDENT American Mathematical Society Mathematical Association of America Society for Industrial and Applied Mathematics BECKENBACH BOOK PRIZE Mathematical Association of America CHAUVENET PRIZE Mathematical Association of America EULER BOOK PRIZE Mathematical Association of America THE DEBORAH AND FRANKLIN TEPPER HAIMO AWARDS FOR DISTINGUISHED COLLEGE OR UNIVERSITY TEACHING OF MATHEMATICS Mathematical Association of America YUEH-GIN GUNG AND DR.CHARLES Y. -
Baxter Equation, Symmetric Functions and Grothendieck Polynomials
hep-th/9306005 YANG - BAXTER EQUATION, SYMMETRIC FUNCTIONS AND GROTHENDIECK POLYNOMIALS SERGEY FOMIN Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts av., Cambridge, MA 02139-4307, U.S.A. and Theory of Algorithm Laboratory SPIIRAN, St.Petersburg, Russia ANATOL N. KIRILLOV L.P.T.H.E., University Paris 6, 4 Place Jussieu, 75252 Paris Cedex 05, France and Steklov Mathematical Institute, Fontanka 27, St.Petersburg, 191011, Russia ABSTRACT New development of the theory of Grothendieck polynomials, basedonanexponential solution of the Yang-Baxter equation in the algebra of projectors are given. 1. Introduction. § The Yang-Baxter algebra is the algebra generated by operators hi(x) which satisfy the following relations (cf. [B], [F], [DWA]) h (x)h (y)=h (y)h (x); if i j 2; (1:1) i j j i | − |≥ hi(x)hi+1(x + y)hi(y)=hi+1(y)hi(x + y)hi+1(x): (1:2) The role the representations of the Yang-Baxter algebra play in the theory of quantum groups [Dr], [FRT], the theory of exactly solvable models in statistical mechanics [B], [F], [Ji], low-dimensional topology [DWA], [Jo], [RT], [KR], the theory of special functions [KR], [VK], and others branchers of mathematics (see, e.g., the survey [C]) is well-known. In this paper we continue to study (cf. [FK1], [FK2]) the connections between the Yang-Baxter algebra and the theory of symmetric functions and Schubert and Grothendieck polynomials. In fact, one can construct a family of symmetric functions 2 Sergey Fomin and Anatol N. Kirillov (in general with operator-valued coefficients) related with any integrable-by-quantum- inverse-scattering-method model [F]. -
Report for the Academic Year 2017–2018
Institute for Advanced Study Re port for 2 0 1 7–2 0 INSTITUTE FOR ADVANCED STUDY 1 8 EINSTEIN DRIVE PRINCETON, NEW JERSEY 08540 Report for the Academic Year (609) 734-8000 www.ias.edu 2017–2018 Cover: SHATEMA THREADCRAFT, Ralph E. and Doris M. Hansmann Member in the School of Social Science (right), gives a talk moderated by DIDIER FASSIN (left), James D. Wolfensohn Professor, on spectacular black death at Ideas 2017–18. Opposite: Fuld Hall COVER PHOTO: DAN KOMODA Table of Contents DAN KOMODA DAN Reports of the Chair and the Director 4 The Institute for Advanced Study 6 School of Historical Studies 8 School of Mathematics 20 School of Natural Sciences 30 School of Social Science 40 Special Programs and Outreach 48 Record of Events 57 80 Acknowledgments 88 Founders, Trustees, and Officers of the Board and of the Corporation 89 Administration 90 Present and Past Directors and Faculty 91 Independent Auditors’ Report THOMAS CLARKE REPORT OF THE CHAIR The Institute for Advanced Study’s independence and excellence led by Sanjeev Arora, Visiting Professor in the School require the dedication of many benefactors, and in 2017–18, of Mathematics. we celebrated the retirements of our venerable Vice Chairs The Board was delighted to welcome new Trustees Mark Shelby White and Jim Simons, whose extraordinary service has Heising, Founder and Managing Director of the San Francisco enhanced the Institute beyond measure. I am immensely grateful investment firm Medley Partners, and Dutch astronomer and and feel exceptionally privileged to have worked with both chemist Ewine Fleur van Dishoeck, Professor of Molecular Shelby and Jim in shaping and guiding the Institute into the Astrophysics at the University of Leiden.