## Visiting address

Ullevål StadionSognsveien 77B

0855 OSLO

Norway

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.

Time:
Mar. 8, 2016 2:15 PM

Thore Egeland (NMBU) will give a seminar in the lunch area, 8th floor Niels Henrik Abels hus at 14:15.

Time and place:
Mar. 3, 2016 2:00 PM - 2:45 PM,
Niels Henrik Abels hus, room 107

Emanuela Rosazza Gianin (University of Milano-Bicocca) gives a lecture with the title: Time-consistency for cash-subadditive risk measures

Time and place:
Mar. 3, 2016 1:15 PM - 2:00 PM,
Niels Henrik Abels hus, room 107

Christian Bender (Saarland University) gives a lecture with the title: Discretizing Malliavin calculus

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

Abstract: For the ax+b semigroup over the natural numbers, which is known to be part of a quasi-lattice ordered group, Laca and Raeburn considered its Nica-Toeplitz algebra and its Cuntz-Nica-Pimsner algebra, with a special appeal to nice presentations by generators and relations as well as the structure of KMS states for a natural dynamics. Shortly thereafter, Brownlowe-an Huef-Laca-Raeburn showed that there are two intermediate quotients between the Nica-Toeplitz algebra and the Cuntz-Nica-Pimsner algebra that exhibit interesting structural properties, especially with regards to KMS states. Since then, analogous quotients have been considered (partly in disguise) in a growing list of case studies on the KMS state structure, e.g. for dilation matrices, self-similar actions, and Baumslag-Solitair monoids. Somewhat surprisingly, all these case studies can be viewed from the perspective of semigroup C*-algebras of right LCM semigroups, and in this talk, I shall describe a unifying perspective on such boundary quotient diagrams. Thereby several questions concerning the general structure of right LCM semigroups are raised.

Time and place:
Feb. 25, 2016 2:30 PM - 3:30 PM,
Rest area 7.floor NHA

Abstract:

Let X=Spec(R) be a smooth affine variety and let Y be a closed subvariety corresponding to an ideal I in R. Finding a set of generators for I is in general a very hard problem, even in the case where X is an affine space over a field k. However, an easy application of Nakayama’s lemma shows that the number n of generators of I is at least the number m of generators of its conormal bundle and at most m+1. We will show how to actually determine when n=m using homotopical and cohomological methods, answering in particular a long standing conjecture of Murthy.

Coffee/Tea/Biscuit from 14.00