# Guest lectures and seminars - Page 12

Time and place: Oct. 15, 2015 2:15 PM - 4:00 PM, B738, NH Abels hus

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

Complete twisted cubics

Time and place: Oct. 13, 2015 3:15 PM,

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.

Time: Oct. 13, 2015 2:15 PM

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.

Time and place: Oct. 12, 2015 1:15 PM - 2:00 PM,

Ingrid Hobæk Haff is giving her inaugural lecture with the title: Parameter estimation for pair-copula constructions.

Time and place: Oct. 6, 2015 12:15 PM - 1:00 PM, NHA 935

Mathematical Institute, University of Oxford

Time and place: Oct. 1, 2015 2:15 PM - 4:00 PM, B738, NH Abels hus

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

The dual cell complex of Hilbert scheme degenerations

Time and place: Sep. 30, 2015 2:15 PM - 4:00 PM, B738

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.

Time and place: Sep. 29, 2015 2:45 PM, Lunch area

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.

Time and place: Sep. 29, 2015 2:15 PM,

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.

Time and place: Sep. 25, 2015 10:15 AM - 12:00 PM, B 735

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.

Time and place: Sep. 24, 2015 2:15 PM - 4:00 PM, B738, NH Abels hus

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

EPW cubes

Time and place: Sep. 17, 2015 2:15 PM - 4:00 PM, B738, NH Abels hus

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

Positroids and the totally nonnegative Grassmannian

Time and place: Sep. 15, 2015 2:15 PM,

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

Time and place: Sep. 10, 2015 2:15 PM - 4:00 PM, B738, NH Abels hus

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

Tropical Ideals

Time and place: Sep. 3, 2015 2:15 PM - 3:00 PM,

Paul Krühner (TU Wien) holds a lecture with the title: Affine processes with compact state space and counter-examples for polynomial processes.

Time and place: Sep. 2, 2015 2:15 PM - 4:00 PM, NHA 738

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.

Time and place: Sep. 1, 2015 2:15 PM, Room B81

Valeria Vitelli (Dept. of Biostatistics, UiO) will give a seminar in room 801 (B81), 8th floor N.H. Abels House at 14:15  September 1st: Probabilistic preference learning with the Mallows rank model

Time and place: Aug. 27, 2015 2:15 PM - 4:00 PM, B738, NH Abels hus

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

An introduction to tropical geometry

Time and place: Aug. 26, 2015 3:00 PM - 4:00 PM,

Andrey Pilipenko (Ukrainian National Academy of Sciences) gives a lecture with the title: Limits of Markov processes with irregular behavior at a fixed point.

Time and place: Aug. 24, 2015 1:15 PM - 2:00 PM,

Tijana Levajkovic (University of Innsbruck) holds a lecture with the title: Chaos expansions for stochastic evolution equations.

Time and place: Aug. 7, 2015 8:00 PM - Aug. 11, 2015 6:45 AM, Coastal Express (Hurtigruten), Norway

Please note that participation is by invitation only. Note also that there is an official homepage of the Abel Symposium 2015.

The Abel Symposium is administrated by the Norwegian Mathematical Society.

Time and place: June 24, 2015 10:15 AM - 12:00 PM, NHA B735

Klaus Thomsen, Aarhus Universitet, Denmark, will give a talk with title "KMS states and ground states for generalized gauge actions on graph C*-algebras"

Time and place: June 17, 2015 2:15 PM - 4:00 PM, NHA B735

John Quigg, Arizona State University at Tempe, USA, will give a talk with title: Landstad duality and a theorem of Pedersen

Abstract:

In joint work with Steve Kaliszewski and Tron Omland, we show how a theorem of Pedersen characterizing exterior equivalent actions on a C*-algebra can be parlayed into an equivalence between two equivariant categories of C*-algebras. In one category, isomorphisms correspond to outer conjugacies of actions, while isomorphisms in the other category are equivariant isomorphisms of the crossed products that respect the generalized fixed point algebras. This category equivalence is a variation of Landstad's original characterization of actions up to equivariant isomorphism, where we now allow more morphisms. Time permitting, we will compare our "outer duality" with Landstad duality and also with Imai-Takai crossed-product duality.

Time and place: June 9, 2015 2:15 PM - 4:00 PM, NHA Building B738

Alfons van Daele (University of Leuven, Belgium) will give a talk with title:  Constructing locally compact quantum groups from pairs of *-algebras

Abstract: Let (A,\Delta)  be a finite-dimensional Hopf *-algebra. The dual B of A is again a finite-dimensional Hopf *-algebra. The entire structure of these two Hopf *-algebras is encoded in the *-algebras A and B and the pairing between the two. We will explain how this works. This is in fact true in many more, and more general situations.  In particular, we give an example constructed from a pair of subroups H,K of a group G with the property that the map (h,k)-> hk is a bijection from HxK to G. This method is used in a joined paper with Magnus Landstad where we construct a pair of locally compact quantum groups from such pairs of subgroups of a locally compact group G.

Time and place: May 29, 2015 - May 30, 2015,

The statistics groups at the University of Oslo and the Norwegian University of Life Sciences invite all PhD-students and postdocs within statistics in the Oslo-region as well as their teachers and supervisors to a  2-days workshop.

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