## Besøksadresse

Ullevål StadionSognsveien 77B

0855 OSLO

Tid og sted:
7. des. 2016 10:15 - 12:00,
NHA, seminarrom B81

John Quigg, Arizona State University (Tempe), USA, will give a talk with title "The Pedersen rigidity problem".

University of Abstract: If \alpha is an action of a locally compact abelian group G on a C*-algebra A, Takesaki-Takai duality recovers (A,\alpha) up to Morita equivalence from the dual action of \widehat{G} on the crossed product A\rtimes_\alpha G. Given a bit more information, Landstad duality recovers (A,\alpha) up to isomorphism. In between these, by modifying a theorem of Pedersen, (A,\alpha) is recovered up to outer conjugacy from the dual action and the position of A in M(A\rtimes_\alpha G). Our search (still unsuccessful, somehow irritating) for examples showing the necessity of this latter condition has led us to formulate the "Pedersen rigidity problem". We present numerous situations where the condition is redundant, including G discrete or A stable or commutative. The most interesting of these "no-go theorems" is for locally unitary actions on continuous-trace algebras. This is joint work with Steve Kaliszewski and Tron Omland.

Tid og sted:
6. des. 2016 15:00,
Undervisningsrom 108

Tittel:

*Sparse Matrix Storage Schemes with OpenCL for a Linear System arising from a Discrete Model of Elasticity*

Tid:
6. des. 2016 14:15

Riccardo De Bin (Department of Mathematics, University of Oslo) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.

Tid og sted:
6. des. 2016 10:15 - 12:00,
B 738

Framed correspondences were invented and studied by Voevodsky in the early 2000-s, aiming at the construction of a new model for motivic stable homotopy theory. Joint with Ivan Panin we introduce and study framed motives of algebraic varieties basing on Voevodsky's framed correspondences. Framed motives allow to construct an explicit model for the suspension P^{1}-spectrum of an algebraic variety. Framed correspondences also give a kind of motivic infinite loop space machine. They also lead to several important explicit computations such as rational motivic homotopy theory or recovering the celebrated Morel theorem that computes certain motivic homotopy groups of the motivic sphere spectrum in terms of Milnor-Witt K-theory. In these lectures we shall discuss basic facts on framed correspondences and related constructions.

Tid og sted:
5. des. 2016 13:15,
Aud. 4 Vilhelm Bjerknes' hus

M.Sc. Øyvind Bleka ved Matematisk institutt vil forsvare sin avhandling for graden ph.d.:

Improved analysis of complex DNA profiles and the interrogation of very large national DNA databases

Tid og sted:
5. des. 2016 10:15,
Aud. 4 Vilhelm Bjerknes' hus

M.Sc. Øyvind Bleka ved Matematisk institutt avholder prøveforelesning over oppgitt emne: "Penalized regression".

Tid og sted:
2. des. 2016 14:15,
Undervisningsrom 735

Tittel:

**Local risk minimizing strategy in a market driven by time-changed Lévy noises**

Tid og sted:
2. des. 2016 11:15 - 12:00,
NHA bygget 9 etg B91

**Stereolithography - A Powerful Tool to Create almost Everything**

Stereolithography or "SLA" printing is a powerful and widely used 3D printing technology for creating prototypes, models, and fully functional parts for production. This additive manufacturing process works by focusing an ultraviolet (UV) laser onto a vat of liquid resin. Layer by layer formation of a polymeric network allows printing parts that are almost impossible to create with other processes.At Formlabs, a startup that originated out of the MIT Media lab in 2011, we work on all aspects of SLA printing; we develop and manufacture 3D printers, resins, and software. In this talk, I will give a detailed overview of the printer technology, the chemistry of the materials, and how to use SLA for lots of exciting applications.

Tid og sted:
30. nov. 2016 10:15 - 12:00,
NHA B81

Abstract: We first discuss C*-simplicity and the unique trace property for discrete groups in light of recent years' development. In particular, we consider amalgamated free products, and give conditions for such to be (and fail to be) C*-simple. Then we define radical and residual classes of groups, and explain that there exists a radical detecting C*-simplicity, in a similar way as the amenable radical detects the unique trace property. The talk is based on joint work with Nikolay A. Ivanov from Sofia University, Bulgaria.

Tid og sted:
29. nov. 2016 10:15 - 12:00,
B 738

Hopkins, Kuhn, and Ravenel proved that, up to torsion, the Borel-equivariant cohomology of a G-space with coefficients in a height n-Morava E-theory is determined by its values on those abelian subgroups of G which are generated by n or fewer elements. When n=1, this is closely related to Artin's induction theorem for complex group representations. I will explain how to generalize the HKR result in two directions. First, we will establish the existence of a spectral sequence calculating the integral Borel-equivariant cohomology whose convergence properties imply the HKR theorem. Second, we will replace Morava E-theory with any L_n-local spectrum. Moreover, we can show, in some sense, a partial converse to this result: if an HKR style theorem holds for an E_\infty ring spectrum E, then K(n+j)_* E=0 for all j\geq 1. This partial converse has applications to the algebraic K-theory of structured ring spectra.

Tid og sted:
24. nov. 2016 14:15 - 16:00,
B638, NH Abels hus

Tid:
22. nov. 2016 14:15

Peter Müller (University of Texas at Austin) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.

Tid og sted:
22. nov. 2016 10:15 - 12:00,
B 738

We compute the generalized slices (as defined by Spitzweck-Østvær) of the motivic spectrum KQ in terms of motivic cohomology and generalized motivic cohomology, obtaining good agreement with the situation in classical topology and the results predicted by Markett-Schlichting.

Tid og sted:
16. nov. 2016 10:15 - 11:00,
Niels Henrik Abels hus, room 1036

Kristina Rognlien Dahl (University of Oslo) is giving her inaugural lecture with the title: Stochastic analysis meets risk and reliability theory.

Tid og sted:
14. nov. 2016 14:00 - 14:45,
Niels Henrik Abels hus, room 637

Olivier Menoukeu Pamen (African Institute for Mathematical Sciences, Ghana and University of Liverpool) gives a lecture with the title: Strong Rate of Convergence for the Euler-Maruyama Approximation of SDEs with Irregular Drift Coefficients.

Tid og sted:
14. nov. 2016 13:15 - 14:00,
Niels Henrik Abels hus, room 637

Rajeev Bhaskaran (Indian Statistical Institute, Bangalore, India) gives a lecture with the title: On the connection between SPDE’s and diffusions arising out of an SDE.

Tid og sted:
10. nov. 2016 14:15 - 16:00,
B735

Michael Whittaker from University of Glasgow will give a talk with title: New directions in self-similar group theory

Abstract: A self-similar group (G,X) consists of a group G acting faithfully on a homogeneous rooted tree such that the action satisfies a self-similar condition. In this talk I will generalise the above definition to faithful groupoid actions on the path space of more general graphs. This new definition allows us to work out the structure of the KMS state space of associated Toeplitz and Cuntz-Pimsner algebras. This is joint work with Marcelo Laca, Iain Raeburn, and Jacqui Ramagge.

Tid og sted:
10. nov. 2016 14:15 - 16:00,
B638, NH Abels hus

Tid og sted:
9. nov. 2016 10:15 - 12:00,
B81

Rasmus Bryder (University of Copenhagen) will give a talk with title: Twisted crossed products over C*-simple groups

Abstract: A twisted C*-dynamical system consists of a C*-algebra, a discrete group and a "twisted" action of the group on the C*-algebra, i.e., the group acts by automorphisms on the C*-algebra in a manner determined by a 2-cocycle of the group into the unitary group of the C*-algebra. Whenever the 2-cocycle (or twist) is trivial, the action is given by a group homomorphism of the group into the automorphism group of the C*-algebra. We consider twisted C*-dynamical systems over C*-simple groups (i.e.,groups whose reduced group C*-algebra is simple) and how C*-simplicity affects the ideal structure of reduced crossed products over such dynamical systems.

Tid og sted:
4. nov. 2016 11:15 - 12:00,
NHA 935

**Microfluidics of sugar transport in plants**

Plants can rightly be called masters of microengineering. Their survival and successful reproduction depends on their ability to overcome a series of physical challenges during growth and when transporting matter over great distances. In this talk, we focus on the microfluidic network responsible for energy distribution (the phloem). We combine experiments on living plants and biomimetic microfluidic devices to elucidate the basic physical principles that govern sugar transport in plants. We derive a scaling relation between the characteristic sizes of the plant organs, which optimizes the rate of sugar transport. Comparison with experimental data suggests that the pipe network is operating at or near the theoretical optimum. We further consider the coupling between photosynthesis and long-distance transport. While sap with high sugar concentration has the greatest transport potential, viscosity impedes flow, a phenomena analogous to congestion in traffic flows. The optimal sugar concentration for transport in plants is 25%, sweeter than Coke (10%) but much less viscous than maple syrup (65%). Although plants have generally evolved towards the theoretical optimum, a number of unusually sweet plants exist. This group consists primarily of crop plants such as corn (40%) and potato (50%), sugar junkies of the natural world.