Tidlegare gjesteforelesninger og seminarer - Side 66

Viggo Hansteen, Professor, ITA

Francesco Cavazzani, Harvard University, gives the Seminar in Algebra and Algebraic Geometry:

Complete twisted cubics

Prof. Alan Gelfand (Duke University, Dept. of Statistical Science) will give a seminar in room 108, ground floor N.H. Abel's Building at 15:15 October 13th.

Prof. Mike West (Duke University, Dept. of Statistical Science) will give a seminar in room 108, ground floor N.H. Abel's House at 14:15 October 13th.

Sven Wedemeyer, Researcher - Institute of Theoretical Astrophysics

Mathematical Institute, University of Oxford

Friday seminar by Chris Thomas from Department of Biology, University of York, UK

Geir Ellingsrud, Professor, Mathematics Department, UiO 

Martin Gulbrandsen, UiS, gives the Seminar in Algebra and Algebraic Geometry

The dual cell complex of Hilbert scheme degenerations  

Judith Packer, University of Colorado (Boulder), USA, will give a talk with title: Wavelets associated to representations of higher-rank graph C*-algebras

Abstract: Let $\Lambda$ denote a finite $k$-graph in the sense of A. Kumjian and D. Pask that is strongly connected, and let $\Lambda^{\infty}$ denote its infinite path space. I discuss some recent joint work with C. Farsi, E. Gillaspy, and S. Kang, where we construct a system of functions that we call ``wavelets" on a Hilbert space of square-integrable functions on $\Lambda^{\infty}.$ In so doing, we generalize work of M. Marcolli and A. Paolucci for finite directed graphs to the higher rank case. The key tool is the construction of a representation of the graph $C^*$-algebra $C^{\ast}(\Lambda)$ on $L^2(\Lambda^{\infty},M)$ for the appropriate measure $M.$ When the finite $k$-graph $\Lambda$ in question is strongly connected and aperiodic, the representation of $C^{\ast}(\Lambda)$ that we obtain is faithful.

Fabian Krüger (Heidelberg Institute for Theoretical Studies) will give a 30 min seminar in the lunch area, 8th floor N.H. Abel's House at 14:45 September 29th.

Monica Musio (University of Cagliari) will give a 30 min seminar in the lunch area, 8th floor N.H. Abel's House at 14:15 September 29th.

Shinji Mukohyama, Yukawa Institute for Theoretical Physics, Kyoto University

Antoine Julien, NTNU, will give a talk with title: Links between cut-and-project tilings and Diophantine approximation

Abstract: Cut-and-project tilings are obtained by cutting a slice of a higher dimensional lattice and projecting it on a lower dimensional space. The result is a point set which is regular enough (since it originates from a lattice), but is not periodic, provided the direction of the slice is irrational in a suitable sense. In one dimension, typical examples of this construction are Sturmian subshifts. It is known that some of their dynamical properties depend on the arithmetic properties of a certain parameter. In this talk, I will recall some known results by Hedlund and Morse on Sturmian subshifts. Then, I will describe how, even in higher dimensions, the repetition properties of some cut-and-project sets can be linked to problems of simultaneous Diophantine approximation. This is joint work with A. Haynes, H. Koivusalo and J. Walton. 

Dr. Terry Onsager, National Oceanic and Atmospheric Administration, USA/Space Weather Prediction Center, USA.

Kristian Ranestad, UiO, gives the Seminar in Algebra and Algebraic Geometry

EPW cubes

Friday seminar by Anna B. Neuheimer, Department of Oceanography, University of Hawai’i at Mānoa, USA

Luc Van Der Voort, Professor, ITA

Felipe Rincon, UiO, gives the Seminar in Algebra and Algebraic Geometry

Positroids and the totally nonnegative Grassmannian

Audun Mathias Øygard (Master student, Dept. of Mathematics, UiO) will give a seminar in the lunch area, 8th floor N.H. Abel's House at 14:15 September 15th: Measuring similarity of classified advertisements using images and text, with applications to recommendation and search at finn.no

Preserving traditions is important, not least barely born traditions, such as the Minglemøte, meant to be at the end of every month containing an ‘r’ (plus perhaps some more). In any case, we’re having another, next Friday Sepember 11 in the lobby. There will be cake and coffee, and there will be (only two this time, to give a chance of having some actual mingling going on) presentations. Notably a summary of the two SFF (Center of Excellence) proposals that the ITA will be sending in this fall: On the “Oslo Cosmology Center" and on  “The Rosseland Centre for Solar Physics” and what they could mean for the institute.

All are invited, we need critical acclaim and perhaps some constructive criticism as well.

Felipe Rincon, UiO, gives the Seminar in Algebra and Algebraic Geometry

Tropical Ideals

Max Gronke, PhD student, ITA

Nicolai Stammeier (Münster) will give a talk with title "Aiming for accuracy - boundary quotients of right LCM semigroups revisited "

Abstract: I will recall the notions of foundation sets and the boundary quotient for right LCM semigroups. This C*-algebra is obtained by modding out products of defect projections over foundation sets in the full semigroup C*-algebra of the right LCM semigroup. Observing that this is in stark contrast to the standard presentations of C*-algebras in the spirit of Cuntz algebras, where a summation relation gets used, we will discuss the possibility of replacing the product relation by a summation relation and arrive at the accurate refinement property. This feature turns out to be quite common among right LCM semigroups. In fact, we are yet to see an example of a right LCM semigroup that has an insufficient supply of accurate foundation sets. Time permitting, we will leave the realm of right LCM semigroups for the sake of finding semigroups without the accurate refinement property.