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Mathematics Department - Colloquium - Fall 2009

Colloquium - Fall 2009



Mathematics Department Colloquia take place on Friday afternoons 4:00-5:00PM in Hill Center 705 , Busch Campus. Also, due to recent construction on Route 18, most on-line maps and driving instructions are out of date. Here are updated driving directions. If you need information on public transportation , you may want to check the New Jersey Transit page for information on fares and schedules for the Northeast Corridor Line. Taxis are available at the New Brunswick train station (fare about $7) and can take you to and from the Hill Center (Victory Cabs, (732) 545-6666). The Rutgers Campus Bus System provides free inter-campus transportation, with the A and H buses taking passengers between Busch Campus and College Avenue, with the A providing a faster ride from College Avenue and the H providing a faster ride from the Hill Center : please visit their website for bus schedules and maps, including real-time tracking of campus buses.

Unfortunately, colloquium cancellations do occur from time to time. Please feel free to call our department (732)-445-3921 before embarking on your journey.

Colloquium participants and hosts may wish to also consult the Rutgers University academic calendar, as well as its calendars of religious holidays and of weather emergencies and university closings.

Organizer(s)

Lisa Carbone, Konstantin Mischaikow, Anders Buch

Archive



Friday, December 4th

CONFERENCE ON MATH FINANCE AND PARTIAL DIFFERENTIAL EQUATIONS, TO BE HELD IN THE HELDRICH HOTEL, NEW BRUNSWICK, NJ

"IN THE NEILSON ROOM"

Time: 9:00 AM
Location: OFFSITE
Abstract: Friday December 4, 2009 Conference on Math Finance and Partial Differential Equations Time: Friday, December 4, 2009, 9:00am - 7:00pm Location: Neilson Room, Heldrich Hotel, New Brunswick, New Jersey


Friday, November 20th

None scheduled, N/A

"Due to 20th Birthday Celebration of DIMACS"

Time: 4:00 PM
Location: Hill 705


Friday, November 13th

Zhenghan Wang , Microsoft and UCSB

"Modeling and Classification of fractional quantum Hall states"

Time: 4:00 PM
Location: Hill 705
Abstract: Fractional quantum Hall (FQH) liquids are electrons in the plane immersed in strong perpendicular magnetic fields. They exhibit the fractional quantum Hall effect which was recognized by a Nobel prize in 1998. FQH liquids are new phases of matter, called topological phases of matter, which are proposed as hardware for large scale quantum computing. The ground states of such systems with N electrons can be modeled by translation-invariant anti-symmetric polynomials in N variables (N is about 10^11 per cm^2 in real materials). The famous examples are the Laughlin wave function and Pfaffian. Physical predictions from the polynomials include the existence of quasi-particles of charges e/3 and e/4, which are confirmed by experiments. I will discuss an elementary classification scheme of such polynomials, which are typically conformal blocks of primary fields in conformal field theories. This is an on-going joint work with physicist X.-G Wen of MIT.


Friday, November 6th

Hyam Rubinstein, University of Melbourne

" Minimal triangulations of 3-manifolds"

Time: 4:00 PM
Location: Hill 705
Abstract: This is joint work with Bus Jaco and Stephan Tillmann. I will give a survey of some recent results where the triangulations with minimum numbers of tetrahedra have been determined for some infinite classes of 3-manifolds which are spherical space forms. We have a program to also determine such minimal triangulations for some hyperbolic examples and also have general strong lower bounds on the number of tetrahedra, based on a Z_2 version of the well-known Thurston norm on homology.


Friday, October 30th

Ben Green, University of Cambridge and Radcliffe Institute at Harvard University

"The inverse conjectures for the Gowers norms"

Time: 4:00 PM
Location: Hill 705
Abstract: For the last 5 years or so Terry Tao and I have been working on a programme to prove certain conjectures of Hardy and Littlewood concerning the number of primes vectors p = (p_1,...,p_n) in some box which satisfy the equation Ap = b. The number of such solutions should be determined, asymptotically, by "local" considerations and our aim is to prove this provided that A is "nondegenerate" (which, sadly, means we do not propose to resolve the twin prime or Goldbach conjectures). In 2006 we reduced this task to that of proving two families of conjectures. We established the first of these in 2007, leaving the task of proving the second family of conjectures, known as the "inverse conjectures for the Gowers norms". There is one of these for each of the so-called Gowers norms U^2,U^3,U^4,... The inverse conjecture for the U^2 norm can be proved by about one line of harmonic analysis, and the inverse conjecture for the U^3 norm was proved in a 70-page paper of Tao and I. Recently, with Tammy Ziegler, we appear to have established the general case, although we have only worked out and written up all the details in the case of the U^4 norm. The paper handling this case is a mere 40 pages long, and I propose to talk about some aspects of this result. I shall not dwell on details of the proof, being more concerned with giving an overview of the area. I will not assume that the audience knows much (anything) about the subject at all (for example, I shall not be assuming the definition of Gowers norm).


Friday, October 23rd

Christian Rosendal, University of Illinois at Chicago

"Descriptive classification theory and separable Banach spaces"

Time: 4:00 PM
Location: Hill 705
Abstract: During the last 25 years, a considerable effort has been made by descriptive set theorist to develop a mathematically precise theory of what it means to classify a class of mathematical structures. This has led to the notion of Borel reducibility, which is a measure of the relative complexity of classes of mathematical structures up to isomorphism, e.g., countable groups, compact manifolds, or separable C*-algebras. We shall see how this theory plays out in a single example; namely, in the case of separable Banach spaces. As it turns out, the complexity of separable Banach spaces up to isomorphism is maximal, which indicates that there can be no meaningful classification by complete invariants. As an alternative, we follow the lead of W. T. Gowers and outline another coarser classification of separable Banach spaces by instead describing the ``irreducible'' subspaces that these spaces are built from. The talk will be based on joint work with V. Ferenczi and A. Louveau.


Friday, October 16th

Alex Feingold , Binghamton University

" Hyperbolic Weyl Groups and the Four Normed Division Algebras"

Time: 4:00 PM
Location: Hill 705
Abstract: Hyperbolic Weyl groups are the Weyl group symmetries of the hyperbolic Kac-Moody Lie algebras. Those infinite dimensional algebras have appeared in some theoretical physics papers on supergravity, a theory combining general relativity with supersymmetry. They have also been conjectured to play a role in string theory, especially the algebra known as E_10, and in the theory of extremal black holes. ���� This talk will give an introduction to recently published joint work with Hermann Nicolai and Axel Kleinschmidt on the Weyl groups of hyperbolic Kac-Moody algebras of� ranks 3, 4, 6 and 10. These are intimately linked to the four normed division algebras, K, real numbers, complex numbers, quaternions, and octonions, respectively. A crucial role is played by integral lattices of the division algebras and associated discrete matrix groups. Our findings can be summarized by saying that the even subgroups,� W^+, of the Kac--Moody Weyl groups, W, are isomorphic to generalized modular groups over K for the simply laced algebras, and to certain finite extensions thereof for the non-simply laced algebras.


Friday, October 9th

Mikhail Khovanov, Columbia University

"Categorification of quantum groups"

Time: 4:00 PM
Location: Hill 705
Abstract: I'll explain a categorification of the positive half of the quantum universal enveloping algebra of a simple Lie algebra. The weight spaces of the positive half become Grothendieck groups of projective modules over certain rings, while multiplication and comultiplication in the Hopf algebra come from induction and restriction functors.


Friday, October 2nd

Marty Golubitsky, Director MBI, Ohio State University

"Symmetry-Breaking; Synchrony Breaking"

Time: 4:00 PM
Location: Hill 705
Abstract: A coupled cell system is a network of interacting dynamical systems. Coupled cell models assume that the output from each cell is important and that signals from two or more cells can be compared so that patterns of synchrony can emerge. We ask: which part of the qualitative dynamics observed in coupled cells is the product of network architecture and which part depends on the specific equations? In our theory, local network symmetries replace symmetry as a way of organizing network dynamics, and synchrony-breaking replaces symmetry-breaking as a basic way in which transitions to complicated dynamics occur.


Friday, September 25th

Wing Li, Georgia Tech

"Eigenvalues of sums of self-adjoint operators, Horn inequalities, and intersection of Schubert varieties in a finite von Neumann algebras"

Time: 4:00 PM
Location: Hill 705
Abstract: Consider self-adjoint operators A,B,C on a finite-dimensional Hilbert space such that A+B+C=0. In 1962, A. Horn conjectured that the relations of eigenvalues of A, B, and C, can be characterized by a set of inequalities defined inductively. This problem was eventually solved by A. Klyachko and Knutson-Tao in the late 1990s. The proof requires tools from algebraic geometry, which unfortunately, are not available when one wants to study the analogous in the von Neumann algebra setting. In this talk I will discuss our recent result of Horn conjecture for self-adjoint operators in arbitrary finite factors. Our approach requires a good understanding of the combinatorial structure of honeycombs and producing elements in the intersection of three Schuber varieties by "bare hands" It is also known that a (`complete') matricial form of the Horn Conjecture will lead to an affirmative answer to the Connes' embedding problem.


Friday, September 18th

Victor H. Moll, Tulane University, http://www.math.tulane.edu/~vhm

"The many facets of definite integration"

Time: 4:00 PM
Location: Hill 705
Abstract: The question of evaluation of definite integrals is as old as Calculus itself. The talk will describe two problems that have appeared while developing integration algorithms. The first one is an interesting generalization of the classical Arithmetic Geometric Mean of Gauss and Legendre. The second example is on the discrete side�a simple integration formula has produced a sequence of integers. Its p-adic valuation and a combinatorial interpretation will be discussed.


Friday, September 11th

None

"WELCOME: DEPARTMENT RECEPTION"

Time: 3:30 PM
Location: Hill 705


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