Gjesteforelesninger og seminarer - Side 33

Makoto Yamashita, Ochanomizu University, will give a talk with title: Drinfeld center and representation theory for monoidal categories

Abstract: Motivated by the recently found relation between central completely positive multipliers and the spherical unitary representations of the Drinfeld double for discrete quantum groups, we construct and analyze the representations of fusion algebra of rigid C*-tensor category from the unitary half-braidings. Through the correspondence of Drinfeld center and the generalized Longo-Rehren construction in subfactor theory, these representations are also related to Popa’s theory of correspondences and subfactors. This talk is based on joint work with Sergey Neshveyev.

Håvard Rue ( Dept. of math., NTNU) gives a seminar in room 107, 1st floor N.H. Abels House at 14:15 February 10th: Penalising model component complexity: A principled practical approach to constructing priors

Helge Brunborg (Statistisk sentralbyrå)  holder et seminar i rom 107, 1. etasje N.H. Abels Hus kl. 14:15 tirsdag  3. februar: Hva skjer med verdens befolkningsutvikling?

Helge Maakestad gives the Seminar in Algebra and Algebraic Geometry:

Generalized enveloping algebras, connections and characteristic classes

Jan O. Kleppe, HiOA, gives the Seminar in Algebra and Algebraic Geometry:

On the Hilbert scheme of space curves

Geir Ellingsrud, UiO, gives the Seminar in Algebra and Algebraic Geometry:

Abelian varieties XV: Abelian varieties are quotients of Jacobian varieties

Christian Voigt (Glasgow) will give a talk with title: The structure of quantum permutation groups

Abstract: Quantum permutation groups, introduced by Wang, are a quantum analogue of permutation groups. These quantum groups have a surprisingly rich structure, and they appear naturally in a variety of contexts, including combinatorics, operator algebras, and free probability. In this talk I will give an introduction to these quantum groups, and review some results on their structure. I will then present a computation of the K-groups of the C*-algebras associated with quantum permutation groups, relying on methods from the Baum-Connes conjecture.  

Alfons van Daele, University of Leuven (Belgium), will give a talk with title: Separability idempotents and quantum groupoids

Andrea Riebler ( Dept. of math., NTNU) gives a seminar in room 107, 1st floor N.H. Abels House at 15:15 December 2nd: Projecting the future burden of cancer: Bayesian APC analysis made simple.

Modular forms are certain complex-analytic functions on the upper-half plane. They can also be interpreted as giving linear-algebraic invariants of elliptic curves, perhaps equipped with some extra structure, and in this way they reveal their algebraic-geometric nature. One of the most fundamental modular forms is the Dedekind eta function. However, it seems that only recently has it been pinned down precisely what extra structure on an elliptic curve is needed to define eta. Namely, Deligne was able to express this extra structure in terms of the 2- and 3-power torsion of the elliptic curve. Deligne's proof, apparently, is computational. In this talk I'll describe a conjectural reinterpretation of Deligne's result, together with some supporting results and a hint at a possible conceptual proof. The reinterpretation is homotopy theoretic, the key being to think of an elliptic curve as giving a class in framed cobordism. This directly connects the number "24" which often appears in the study of eta to the 3rd stable stem in topology. 

Johannes Kleppe, Høgskolen i Buskerud og Vestfold, gives the Seminar in Algebra and Algebraic Geometry:

Abelian varieties XII

I will discuss joint work in progress with David Gepner, computing the ring of endomorphisms of the equivariant motivic sphere spectrum, for a finite group. The result is a combination of the endomorphism ring of the equivariant topological sphere spectrum (which equals the Burnside ring by a result of Segal) and that of the motivic sphere spectrum (which equals the Grothendieck-Witt ring of quadratic forms by a result of Morel). This computation is a corollary of a tom Dieck style splitting for certain equivariant motivic homotopy groups.   

Martijn Caspers (Münster) will give a talk with title: The Haagerup property for arbitrary von Neumann algebras

Abstract: The Haagerup property is an approximation property for both groups and operator algebras that has important applications in for example the Baum-Connes conjecture or von Neumann algebra theory. In this talk we show that the Haagerup property is an intrinsic invariant of an arbitrary von Neumann algebra. We also discuss stability properties of the Haagerup property under constructions as free products, graph products and crossed products. Finally we discuss alternative characterizations in terms of the existence of suitable quadratic forms.

Jan Fredrik Bjørnstad (Statistics Norway and Dept. of Math.,UiO) gives a seminar in room 107, 1st floor N.H. Abels House at 14:15 November 18th: Survey sampling the way I see it.

This is a work we had done jointly with Garkusha (after Voevodsky) arXiv:1409.4372. Using the machinery of framed sheaves developed by Voevodsky, a triangulated category of framed motives is introduced and studied. To any smooth algebraic variety X in Sm/k, the framed motive M_fr(X) is associated in that category . Also, for any smooth scheme X in Sm/k an explicit quasi-fibrant motivic replacement of its suspension P1-spectrum is given. Moreover, it is shown that the bispectrum (M_fr(X),M_fr(X)(1),M_fr(X)(2), ... ), each term of which is a twisted framed motive of X, has motivic homotopy type of the suspension bispectrum of X. We also construct a compactly generated triangulated category of framed bispectra SH_fr(k) and show that it reconstructs the Morel-Voevodsky category SH(k). As a topological application, it is proved that the framed motive M_fr(pt)(pt) of the point pt = Speck evaluated at pt is a quasi-fibrant model of the classical sphere spectrum whenever the base field k is algebraically closed of characteristic zero.   

The goal of this talk is to present some recent computations of the Picard groups of several spectra of topological modular forms. The first part of the talk will introduce the toolbox, which consists of descent theory and a technical lemma allowing us to compare stable and unstable information in spectral sequences. This is joint work with Akhil Mathew.   

Tore Selland Kleppe (University of Stavanger) gives a seminar in room 107, 1st floor N.H. Abels House at 14:15 November 11th: Bandwidth Selection In Pre-Smoothed Particle Filters

Marco Matassa (UiO) will give a talk with title: Dirac Operators on Quantum Flag Manifolds

Abstract: I will review the paper "Dirac Operators on Quantum Flag Manifolds" by Ulrich Krähmer. The aim is to define Dirac operators on quantized irreducible flag manifolds. These will yield Hilbert space realizations of some distinguished covariant first-order differential calculi.

Jeg vil definere Singerkonstruksjonen R_+(M) og gjennomføre Adams-Gunawardena-Millers bevis av Lins teorem.  

The Lattice Boltzmann Method and its application in modeling of physiological  flows

Jeg vil snakke om de endelige underalgebraene A(n) i Steenrodalgebraen, analysere A(n)-modulstrukturen til den kontinuerlige kohomologien til Tatekonstruksjonen, og skissere Lin-Davis-Mahowald-Adams' bevis av Lins teorem. 

Adam Sørensen (UiO) will give a talk with title: Almost commuting matrices

Abstract: Two matrices A,B are said to almost commute if AB is close to BA (in a suitable norm). A question of Halmos, answered by Lin, asks if two almost commuting self-adjoint matrices are always close to two exactly commuting self-adjoint matrices. We will survey what is known about this and similar questions, and report on recent work with Loring concerning how the questions change if we look at real rather than complex matrices.

Kristan Ranestad (Dept. of Math, UiO) gives a seminar in room 107, 1st floor N.H. Abels House at 14:15 Tuesday October 14th. Algebra og statistics: Phylogenetic models from an algebraic geometric viewpoint

Jeg avslutter reduksjonen av Segalformodningen til et algebraisk spørsmål om en Ext-ekvivalens, og vil se i mer detalj på hvordan Pontryagin--Thom-konstruksjonen brukes til å bevise Wirthmüller- og Adams transfer-ekvivalensene i stabil ekvivariant homotopiteori.