## Visiting address

Ullevål StadionSognsveien 77B

0855 OSLO

Norway

Time and place:
Feb. 1, 2017 2:15 PM - 4:00 PM,
B 738

The Barratt nerve BSd X of the Kan subdivision Sd X of a simplicial set X \in sSet is a triangulation. The Barratt nerve is defined as taking the poset of non-degenerate simplices, thinking of it as a small category and then finally taking the nerve.Waldhausen, Jahren and Rognes (Piecewise linear manifolds and categories of simple maps) named this construction 'the improvement functor' because of the homotopical properties and because its target is non-singular simplicial sets. A simplicial set is said to be 'non-singular' if its non-degenerate simplices are embedded. There is a least drastic way of making a simplicial set non-singular called 'desingularization', which is a functor D:sSet -> nsSet that is left adjoint to the inclusion.
The functor DSd^{^2} is the left Quillen functor of a Quillen equivalence where the model structure on sSet is the standard one where the weak equivalences are those that induce weak homotopy equivalences and the fibrations are the Kan fibrations. I will talk about the main steps of the proof that the natural map DSd X -> BX is an isomorphism for regular X. This implies that DSd^{^2} is a triangulation and that the improvement functor is less ad hoc than it may seem. Furthermore, I will explain how the result provides evidence that any cofibrant non-singular simplicial set is the nerve of some poset.

Time:
Jan. 31, 2017 2:15 PM

Inge S. Helland (Professor emeritus at Department of Mathematics,UiO) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.

Time and place:
Jan. 26, 2017 11:00 AM -
Jan. 28, 2017 3:00 PM,
University of Oslo

A conference celebrating the work of Ragni Piene on the occasion of her 70th birthday.

Time and place:
Jan. 13, 2017 1:15 PM,
"Abels utsikt", 12. etasje Niels Henrik Abels hus

Siv.ing. Marie Lilleborge ved Matematisk institutt vil forsvare sin avhandling for graden ph.d.:

**Efficient Information Gathering in Bayesian Networks**

Time and place:
Jan. 13, 2017 10:15 AM,
"Abels utsikt", 12. etasje Niels Henrik Abels hus

Siv.ing. Marie Lilleborge ved Matematisk institutt avholder prøveforelesning over oppgitt emne: "Inference in Bayesian networks".

Time and place:
Jan. 10, 2017 10:15 AM - 12:00 PM,
B 738 NHA

Triangulated categories of motives over schemes are sort of the "universal derived categories" among various derived categories obtained by various cohomology theories like l-adic cohomology. Ayoub constructed them using the A1-homotopy equivalences and étale topology. I will introduce the construction of triangulated categories of motives over fs log schemes. Fs log schemes are kinds of "schemes with toroidal boundary," and A1-homotopy equivalences and étale topology are not enough to obtain all homotopy equivalences between fs log schemes. I will explain what extra homotopy equivalences and topologies are neeeded.

Time and place:
Jan. 9, 2017 8:30 AM -
Jan. 10, 2017 5:00 PM,
The Norwegian Academy of Science and Letters

The symposium is a follow-up of four highly successful previous symposia, held 14-15 October 2008 in the Norwegian Academy in Oslo, 1-2 November 2010 in RSE in Edinburgh, 2013 Oslo and 2015 Edinburgh. Topics of this year's symposium include: internal waves, waves and ice, freak waves and wave-structure interaction as well as related aspects of stratified and buoyancy-driven oceanic flows.

The scope of the programme will reflect the ongoing wave research projects in Norway and Scotland individually and in collaboration and it will include a special session celebrating the 6oth birthday of John Grue, the co-Director of the DNVA-RSE *Waves* symposia since their inception.

Time and place:
Jan. 5, 2017 12:00 PM -
Jan. 8, 2017 9:00 AM,
Lysebu (Oslo)

The 17th Danish-Norwegian workshop in Operator algebras will take place at Lysebu (Oslo), January 5 - 8, 2017, with support from the Foundation for Danish-Norwegian Cooperation. It will start with lunch on Thursday, January 5, and end after breakfast on Sunday, January 8.

One day of the workshop will be devoted to commemorate our dear colleague and friend, Ola Bratteli, who passed away in 2015 and would have turned 70 in October 2016. Ola’s nearest collaborators over the years (George Elliott, David Evans, Akitaka Kishimoto, Palle Jorgensen and Derek Robinson) will then give talks reflecting the great impact of Ola’s work within several topics (e.g. AF-algebras, derivations, C*-dynamical systems, mathematical physics, wavelets).

Participation is possible only by personal invitation from the organizing committee.

The programme will be made available around the beginning of December.

Time:
Dec. 20, 2016 2:15 PM

Daniel Roy (Department of Statistical Sciences, University of Toronto) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.

Time and place:
Dec. 16, 2016 1:15 PM,
Aud. 4 Vilhelm Bjerknes' hus

M.Sc. Olav Nikolai Breivik ved Matematisk institutt vil forsvare sin avhandling for graden ph.d.:

**Bayesian spatio-temporal hierarchical modeling**: Bycatch in the Barents Sea shrimp fishery and North Atlantic windiness

Time and place:
Dec. 16, 2016 10:15 AM,
Aud. 4 Vilhelm Bjerknes' hus

M.Sc. Olav Nikolai Breivik ved Matematisk institutt avholder prøveforelesning over oppgitt emne: "Models and methods for compositional data".

Time and place:
Dec. 15, 2016 10:15 AM - 12:00 PM,
GHS room 3514

Ulrik Bo Rufus Enstad (Oslo) will give a talk with title: Connections between Gabor frames and Noncommutative Tori

Abstract: A Gabor frame is a special type of frame in the Hilbert space of square-integrable functions on the real line. Gabor frames provide robust, basis-like representations of functions, and have applications in a wide range of areas. They have a duality theory which is deeply linked to Rieffel’s work on imprimitivity bimodules over noncommutative tori. We explore several links between Gabor frames and noncommutative tori, and show how operator algebras can be used to give alternative proofs of theorems from time-frequency analysis. This talk is based on my Master’s thesis written at NTNU, which reviews Franz Luef’s work on the connections between Gabor frames and modules over noncommutative tori, as well as some joint work with Franz Luef.

Time and place:
Dec. 12, 2016 1:15 PM - 2:00 PM,
Niels Henrik Abels hus, room 1036

Rodwell Kufakunesu (University of Pretoria, South Africa) gives a lecture with the title: Pricing and hedging quanto commodity options.

Time and place:
Dec. 12, 2016 12:15 PM - 1:00 PM,
Niels Henrik Abels hus, room 1036

Nacira Agram (University of Oslo) gives a lecture with the title: Model Uncertainty Stochastic Mean-Field Control.

Time and place:
Dec. 8, 2016 11:15 AM - 1:00 PM,
B 738

A continuation of part I.

Time and place:
Dec. 7, 2016 10:15 AM - 12:00 PM,
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.

Time:
Dec. 6, 2016 2:15 PM

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.

Time and place:
Dec. 6, 2016 10:15 AM - 12:00 PM,
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.

Time and place:
Dec. 5, 2016 1:15 PM,
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

Time and place:
Dec. 5, 2016 10:15 AM,
Aud. 4 Vilhelm Bjerknes' hus

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

Time and place:
Dec. 2, 2016 11:15 AM - 12:00 PM,
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.

Time and place:
Nov. 30, 2016 10:15 AM - 12:00 PM,
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.

Time and place:
Nov. 29, 2016 10:15 AM - 12:00 PM,
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.

Time and place:
Nov. 24, 2016 2:15 PM - 4:00 PM,
B638, NH Abels hus