Institut for Matematiske Fag > Kalender
Begivenheder onsdag den 20. juni 2012
Onsdag den 20. juni 2012 kl. 06:00-07:00. Sprog: engelsk.
This is a test of the calendar
Taler(e): Se nedenstående oversigt
Onsdag den 20. juni 2012 kl. 09:00-12:15. Sted: Aud. 4. Sprog: dansk.
9.15 Laura Hass Thomsen (vejledere Peter Erling Nielsen/ Steffen Lind, ØI)
10.00 Jennifer Niyonkuru (vejleder Peter Birch Sørensen, ØI)
10.45 Helene Thoresen (vejleder Michael Bergman, ØI)
11.30 Frederik Stampe (vejleder Hans Keiding, ØI)
Censor: Bodil Olai Hansen
Relations in the cohomology of classifying spaces of manifold bundles
Taler(e): Ilya Grigoriev
Onsdag den 20. juni 2012 kl. 13:15-14:15. Sted: Aud 8. Sprog: engelsk.
The n-th cohomology of the classifying space of surface bundles with fiber of genus g, denoted H^n(BDiff \Sigma_g), is known in the "stable range" (n <= (2g-2)/3) by theorems of Madsen-Weiss, Harer, and others. In this range, the map from a free algebra generated by the so-called "kappa-classes" to H^*(BDiff \Sigma_g) is an isomorphism. Recently,
Soren Galatius, Oscar Randal-Williams, Ib Madsen, and Alexander Berglund have obtained similar results for a high-dimensional generalization of this space, with the surface \Sigma_g replaced by the connect sum of g copies of the cross product S^k x S^k.
Outside the stable range, the kernel of the above-mentioned map for surfaces has been studied by Morita, Faber, Looijenga, Pandharipande and many others. In this talk, I will describe a method for producing a vast family of elements in the kernel that also works in the the high-dimensional case (for odd k >= 1). This method is based on a refinement of results in the surface case due to Oscar Randal-Williams. The kernel is large enough to imply that the image of this map ("the tautological subring") is finitely-generated for all odd k, rationally, even though there are infinitely many kappa classes. It also implies upper bounds on the stable range of cohomology for fixed g and k.
Organiseret af Alexander Berglund
Baby NCG Seminar
Taler(e): Henrik Densing Petersen, Adam Sørensen
Onsdag den 20. juni 2012 kl. 13:15-14:00. Sted: Aud 7. Sprog: engelsk.
Henrik will be presenting the following preprint:
Weak Exactness for C*-algebras and Application to Condition (AO) (arXiv:1206.0388)
We generalize Kirchberg's weak exactness to inclusions of C*-algebras in von Neumann algebras and study some characterizations and permanence properties which are similar to those of exact groups. We then consider a similar condition to Ozawa's condition (AO) with our weak exactness and generalize Ozawa's theorem for bi-exact groups. As a corollary, we give new examples of prime factors.
Adam will be presenting the following preprint:
The Cuntz semigroup of continuous fields (arXiv:1205.6608)
Ramon Antoine, Joan Bosa, Francesc Perera
In this paper we describe the Cuntz semigroup of continuous fields of C$^*$-algebras over one dimensional spaces whose fibers have stable rank one and trivial $K_1$ for each closed, two-sided ideal. This is done in terms of the semigroup of global sections on a certain topological space built out of the Cuntz semigroups of the fibers of the continuous field. When the fibers have furthermore real rank zero, and taking into account the action of the space, our description yields that the Cuntz semigroup is a classifying invariant if and only if so is the sheaf induced by the Murray-von Neumann semigroup.
Organiseret af Adam and Jamie
N - tuples of commuting operators and index theorems
Taler(e): Ryszard Nest
(University of Copenhagen)
Onsdag den 20. juni 2012 kl. 15:15-16:15. Sted: Aud 8. Sprog: engelsk.
We will recall basic facts about holomorphic functional calculus and homology of n - tuples of commuting operators, give some instances, when one can prove an associated index theorem and give some applications to multivariable Toeplitz operators.
Organiseret af SE
Taler(e): Se nedenstående oversigt
Onsdag den 20. juni 2012 kl. 15:15-17:30. Sted: Aud. 9. Sprog: dansk.
15.15 Magnus Skude
16.00 Rasmus Svensson
16.45 Martin Speirs
Vejleder: Søren Jøndrup
Censor: Henning Haahr Andersen