Events - Page 33

Ritwik Mukherjee (TIFR) gives the Seminar in Algebra and Algebraic Geometry:

Title: Enumerative Geometry of singular curves in a Linear System

Abstract: Enumerative geometry is a branch of mathematics that deals with the following question: "How many geometric objects satisfy certain constraints". A well known class of enumerative question is to count curves in a linear system H^0(X,L) that have some prescribed singularities. In this talk we will describe a topological method to approach this problem. We will express the enumerative numbers as the Euler class of an appropriate bundle. We will then go on to explain how we compute the degenerate contribution of the Euler class using a topological method.

We invite you to a one-day workshop celebrating Professor Bent Natvig's 70th anniversary. Invited speakers will present recent developments in some of the areas where Bent has made significant contributions, including reliability theory and mathematical statistics.

Bent Natvig has, since 1986, been a professor of mathematical statistics at the Department of Mathematics. He is the author of a long list of important papers published in top-ranked scientific journals as well as the recent book entitled "Multistate Systems Reliability Theory with Applications" (John Wiley & Sons). At our department, Bent has taken the leading role in the area of reliability theory. On August 1 this year, he turns 70.

Dr. Nacira Agram (University of Biskra, Algeria) gives a lecture with the title: Stochastic optimal control of McKean-Vlasov equations with anticipating law.

John Christian Ottem, UiO, gives the Seminar in Algebra and Algebraic Geometry:

Title: Moduli of K3s via Global Torelli

Abstract: I'll give a brief account of the Torelli theorems and the construction of the moduli space of K3 surfaces 

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

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

Ideals of points and Waring problems for polynomials​

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.

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

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. 

Abstract:

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.

A Scandinavian Gathering Around Remarkable Discrete Mathematics

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.

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).

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

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

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

K3 surfaces seminar: The moduli spaces of polarized K3 surfaces

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.

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

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

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

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.

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

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

K3 surfaces seminar: Endomorphism fields and Mumford–Tate groups

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.