## Visiting address

Ullevål StadionSognsveien 77B

0855 OSLO

Norway

Time and place:
May 20, 2016 2:30 PM - 3:30 PM,
Rest area 7.floor NHA

Continuing from last week, I will talk about Andrew Wiles' proof of the Taniyama-Shimura-Weil Conjecture, and why it implies Fermat's Last Theorem.

There will be served coffee, tea and biscuits from 14.00.

Time and place:
May 19, 2016 2:15 PM - 4:00 PM,
B738, NH Abels hus

Alessandro Oneto (Stockholm) gives the Seminar in Algebra and Algebraic Geometry:

**Ideals of points and Waring problems for polynomials**

Time and place:
May 19, 2016 2:15 PM - 4:00 PM,
NHA B735

Abstract: This talk addresses some of the fundamental barriers in the theory of computations. Many computational problems can be solved as follows: a sequence of approximations is created by an algorithm, and the solution to the problem is the limit of this sequence (think about computing eigenvalues of a matrix for example). However, as we demonstrate, for several basic problems in computations such as computing spectra of operators, solutions to inverse problems, roots of polynomials using rational maps, solutions to convex optimization problems, imaging problems etc. such a procedure based on one limit is impossible. Yet, one can compute solutions to these problems, but only by using several limits. This may come as a surprise, however, this touches onto the boundaries of computational mathematics. To analyze this phenomenon we use the Solvability Complexity Index (SCI). The SCI is the smallest number of limits needed in order to compute a desired quantity. The SCI phenomenon is independent of the axiomatic setup and hence any theory aiming at establishing the foundations of computational mathematics will have to include the so called SCI Hierarchy. We will specifically discuss the vast amount of classification problems in this non-collapsing complexity/computability hierarchy that occur in inverse problems, compressed sensing problems, l1 and TV optimization problems, spectral problems, PDEs and computational mathematics in general.

Time and place:
May 13, 2016 2:30 PM - 3:30 PM,
Rest area 7.floor NHA

In preparation for the Abel Prize week, I will talk about Fermat's Last Theorem and the Taniyama-Shimura-Weil Conjecture about the modularity of elliptic curves.

There will be served coffee, tea and biscuits from 14.00.

Time and place:
May 9, 2016 -
May 14, 2016,
Oslo and Akershus University College

The conference "Quantum groups: geometry, representations, and beyond" will take place on May 9-14, 2016.

Time and place:
May 4, 2016 2:15 PM - 4:00 PM,
NHA B735

Abstract: In a recent work with R. Conti (La Sapienza Univ., Rome), we have introduced a notion of positive definiteness for certain functions associated to a (unital, discrete) C*-dynamical system. We will sketch the proof of a Gelfand-Raikov type theorem for such functions and use it to construct complete positive maps on the full and the reduced C*-crossed products of the system. We will also explain how a natural definition of amenability for C*-dynamical systems emerges from our work.

Time and place:
Apr. 29, 2016 12:15 PM - 2:00 PM,
B 637 (B 63)

Time:
Apr. 26, 2016 2:15 PM

Timo Koski (Dept. of Mathematics, Royal Institute of Technology, Stockholm) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.

Time and place:
Apr. 21, 2016 9:30 AM -
Apr. 22, 2016 2:00 PM,
Niels Henrik Abels building

A Scandinavian Gathering Around Remarkable Discrete Mathematics

Time and place:
Apr. 20, 2016 2:15 PM - 3:15 PM,
NHA B735

Abstract: The talk will be on positive linear maps of the n x n matrices into itself, a topic which has become quite popular in quantum information theory. The maps closest to physics are the completely positive ones. I´ll discuss an approximation by a completely positive map to a positive map via the trace , called the “structural physical approximation”, the SPA of the map. Much of the talk will circle around a counter example to a conjecture on the SPA.

Time and place:
Apr. 19, 2016 2:15 PM - 4:00 PM,
B638, NH Abels hus

Sofia Tirabassi (UiB), gives the Seminar in Algebra and Algebraic Geometry:

**Title: Characterization of product of theta divisors**

Abstract: This is a joint work with Z. Jiang and M. Lahoz. We give a new cohomological characterization of product of theta divisors in principally polarized abelian varieties and we completely classify n-varieities with of maximal albanese dimension and with irregularity 2n-1 and euler characteristic 1, extending lower dimensional results of Hacon--Pardini. I will do my best to keep the first hour enjoyable and entertaining also for graduate students with background in algebraic geometry (and related areas).

Time:
Apr. 19, 2016 2:15 PM

Anders Holmberg (Statistics Norway, SSB) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.

Time and place:
Apr. 13, 2016 2:15 PM - 4:00 PM,
NHA B735

Abstract: In the classification program for C*-algebras some of the usual assumptions put on the algebras are that they are simple or have at most have finitely many ideals. We often also want algebras that have real rank 0. In this talk we will discuss how to classify certain graph algebras with uncountably many ideals and without real rank 0. There will be examples and applications. Joint work with S. Eilers, G. Restorff, and E. Ruiz

Time and place:
Apr. 7, 2016 2:15 PM - 4:00 PM,
B738, NH Abels hus

Jørgen Vold Rennemo (Oxford) gives the Seminar in Algebra and Algebraic Geometry:

**K3 surfaces seminar: The moduli spaces of polarized K3 surfaces**

Time and place:
Apr. 6, 2016 2:15 PM - 4:00 PM,
NHA B735

Abstract: There are many interesting examples of groups acting on trees, arising in various fields (e.g. combinatorial group theory, number theory, geometry). When a group acts on a tree, it necessarily also acts on the boundary of the tree, a (totally disconnected) compact Hausdorff space. The C*-algebras obtained from the crossed product construction include many fundamental examples. I will describe methods for analyzing such crossed products, developed in joint work with Nathan Brownlowe, Alex Mundey, David Pask and Anne Thomas.

Time:
Apr. 5, 2016 2:15 PM

Manuela Zucknick (Dept. of Biostatistics, UiO) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.

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

M.Sc. Martin Jullum ved Matematisk institutt vil forsvare sin avhandling for graden ph.d.:

New focused approaches to topics within model selection and approximate Bayesian inversion

Time and place:
Apr. 1, 2016 10:15 AM,
Aud. 4 Vilhelm Bjerknes' hus

M.Sc. Martin Jullum ved Matematisk institutt avholder prøveforelesning over oppgitt emne: "Empirical likelihood".

Time and place:
Mar. 31, 2016 2:15 PM - 4:00 PM,
B738, NH Abels hus

Arvid Siqveland (HBV), gives the Seminar in Algebra and Algebraic Geometry:

**K3 surfaces seminar: Endomorphism fields and Mumford–Tate groups II**

Time and place:
Mar. 16, 2016 2:15 PM - 4:00 PM,
NHA B735

Abstract: In this follow-up talk, I shall outline how the boundary quotient diagram may be useful for K-theoretic considerations. We start with the diagram within the context of integral dynamics, and then speculate about potentially promising directions of generalizations.

Time and place:
Mar. 11, 2016 1:15 PM,
Aud. 4 Vilhelm Bjerknes' hus

M.Sc. Erlend Briseid Storrøsten ved Matematisk institutt vil forsvare sin avhandling for graden ph.d.:

Convergence Rates for Stochastic and Degenerate-Parabolic Balance Laws

Time and place:
Mar. 11, 2016 11:15 AM - 12:00 PM,
B91, NHA bygget

**Zebrafish embryos: a useful tool for the study of nanoparticle behavior in real time in a vertebrate**

Time and place:
Mar. 11, 2016 10:15 AM,
Aud. 4 Vilhelm Bjerknes' hus

M.Sc. Erlend Briseid Storrøsten ved Matematisk institutt avholder prøveforelesning over oppgitt emne: "Mean field games".

Time and place:
Mar. 10, 2016 2:15 PM - 4:00 PM,
B738, NH Abels hus

Arvid Siqveland (HBV), gives the Seminar in Algebra and Algebraic Geometry:

**K3 surfaces seminar: Endomorphism fields and Mumford–Tate groups**

Time and place:
Mar. 9, 2016 2:15 PM - 4:00 PM,
NHA B735

Abstract: In this follow-up talk, we shall review the results on the structure of KMS states from the case studies of - the ax+b semigroup over the natural numbers (Laca-Raeburn and Brownlowe-an Huef-Laca-Raeburn), - integer dilation matrices (Laca-Raeburn-Ramagge), - self-similar actions (Laca-Raeburn-Ramagge-Whittaker), and - Baumslag-Solitair monoids (Clark-an Huef-Raeburn) from the perspective of the boundary quotient diagram for the respective right LCM semigroups. We will also discuss (to some extent) similarities and differences of the proofs among these cases.