Gjesteforelesninger, seminarer og konferanser

Kommende

Tid og sted: 11. jan. 2018 15:00 - 17:00, PRIO, Hausmannsgate 3, Oslo

This seminar is a part of the UiO-PRIO collaborative effort Oslo Lectures on Peace and Conflict

Tid og sted: 18. juni 2018 - 22. juni 2018, Sophus Lie Conference Center, Nordfjordeid, Norway.

Nordfjordeid Summer school 2018

Tid og sted: 6. des. 2018 11:00 - 8. des. 2018 15:00, University of Oslo

A conference in algebraic geometry on the occasion of Geir Ellingsrud’s 70th birthday

Tidligere

Tid og sted: 4. des. 2017 09:00 - 8. des. 2017 12:00, Room 108, N.H. Abel's House
Tid: 24. nov. 2017 11:30 - 12:00

Andreas Carlson og Jean Rabault

Nature has invented ingenious aerodynamic design solutions, some of which are critical for plants as wind dispersal of seeds and fruits is coupled to their flight performance. This formulates into an optimization problem for plants: large seed wings can lead to increased lift and more efficient dispersion, but are costly for the tree to build and can more easily be trapped in the canopy. Double winged seeds/fruits separate from their tree when a specific level of dessication is reached, and autorotate as they descend to the ground. This leads to the question: how is the wing curvature of seeds/fruits linked to their flight performance? To answer this, we develop a theoretical model that suggests the existence of an optimal wing curvature that yields maximal lift. To further understand the interplay between the flow and the wing geometry, we perform a synthetic seed adaptation by deploying 3D printing of double winged fruits that we use in flight experiments, where we span the phase space of aerial dynamics by changing the of wing curvature and seed/fruit weight. Experiments confirm that there is a sweet-spot in curvature to maximise the flight time consisted with geometrical measurements from a wide range of seeds in Nature. Our results highlights the importance of not curving too much or too little for helicopter fruits to have an optimal flight performance.

Tid: 24. nov. 2017 11:00 - 11:30

Elisabeth Seland

In my job as research adviser, I receive a lot of questions about rights, possibilities and problems in connection with scientific publishing and open access. Both EU and the Norwegian Research Council have rules about this, and there is also a UiO policy in place that is relevant for all employees. I will give a short presentation to try to clear up what you have to, must, may, could and should related to Open access. In my experience many of you have the same questions about these issues, so I hope you bring your questions with you and we can address them in the seminar.

Tid og sted: 22. nov. 2017 14:15 - 16:00, Desolation Row, Sognsveien 77 B

I will discuss the differential structure in the mod 2 Adams spectral sequence for tmf, leading to its E_\infty-term.  These calculations were known to Hopkins-Mahowald; in their current guise they are part of joint work with Bruner.

Tid og sted: 15. nov. 2017 14:30 - 16:00, Desolation Row, Sognveien 77 B

I will report on work in progress on calculations of the motivic homotopy groups of MGL (the algebraic cobordism spectrum) over number fields. It is known that pi_{2n,n}(MGL) is the Lazard ring, and pi_{-n,-n}(MGL) is Milnor K-theory of the base field. We will calculate all of pi_{*,*}(MGL) with the slice spectral sequence (motivic Atiyah-Hirzebruch spectral sequence) over a number field. I will give a brief review of the the tools and sketch the main parts of the calculation: The input from motivic cohomology, the use of C_2-equivariant Betti realization and comparison with Hill-Hopkins-Ravenel to determine the differentials, and settle most of the hidden extensions. 

Tid og sted: 8. nov. 2017 15:00 - 16:00, Hurricane, Sognsveien 77 b

I will discuss the algebra structure of the E_2-term of the mod 2 Adams spectral sequence for tmf, given by the cohomology Ext_{A(2)}(F_2, F_2) of A(2).  We (Bruner & Rognes) use Groebner bases to verify the presentation given by Iwai and Shimada, with 13 generators and 54 relations. Thereafter I will discuss the relationship between differentials and Steenrod operations in the Adams spectral sequence for E_\infty ring spectra.  

Welcome to the second FINEWSTOCH Networkshop. The workshop will bring together leading researchers in stochastics and probability theory to discuss recent developments with a particular focus on finance, insurance, energy and weather. 

Tid og sted: 6. nov. 2017 12:45 - 13:45, End of Line, Ullevål

Pawel Kasprzak (Warzaw) will give a talk with title " Quantum actions on discrete quantum spaces"

Abstract:

To any action of a compact quantum group on a von Neumann algebra which is a direct sum of factors we associate an equivalence relation corresponding to the partition of a space into orbits of the action. We show that in case all factors are finite-dimensional (i.e. when the action is on a discrete quantum space) the relation has finite orbits.  We then apply this

i) to generalize the classical theory of Clifford, concerning the restrictions of representations to normal subgroups, to the framework of quantum subgroups of discrete quantum groups, itself extending the context of closed normal quantum subgroups of compact quantum groups; ii) to the context of idempotent states showing that the  algebra of invariant elements is finite dimensional if and only if the corresponding state is normal. Joint work with K. De Commer, A. Skalski and P. Sołtan.

Tid og sted: 2. nov. 2017 10:15 - 11:00, Gates of Eden

When and how surface structure determines the dynamics of partial wetting  

Tid og sted: 1. nov. 2017 14:15 - 16:00, Desolation Row, Sognsveien 77 B

I will discuss machine computations in a finite range, using Bruner's ext-program, of Ext over A, the mod 2 Steenrod algebra, and over A(2), the subalgebra of A generated by Sq^1, Sq^2 and Sq^4. These are the E_2-terms of the mod 2 Adams spectral sequences for S and tmf, respectively.

Tid og sted: 30. okt. 2017 15:15 - 16:00, Hurricane

Sedimentation-diffusion equilibrium of Quincke rollers  

Tid og sted: 27. okt. 2017 13:00 - 14:00, hurricane

Iceberg drift on dead water

Tid og sted: 26. okt. 2017 14:15 - 16:00, Ullevål
Tid og sted: 23. okt. 2017 12:45 - 13:45, Gates of Eden

Erik Bedos (UiO) will give a talk with title "On Exel-Pardo algebras as Cuntz-Pimsner algebras"

Abstract:

In a joint work with S. Kaliszweski and J. Quigg (https://arxiv.org/pdf/1512.07302.pdf, to appear in JOT), we consider a continuous action of a locally compact group G on a topological graph E, equipped with a G-valued continuous cocycle, and show how to construct a C*-correspondence from these data, giving rise to a Toeplitz algebra and a Cuntz-Pimsner algebra. In the talk we will sketch this construction, but restrict ourselves to the discrete case. We will also describe these algebras in terms of generators and relations when E is row-finite. As a corollary we get that the associated Cuntz-Pimsner algebra coincides with the C*-algebra recently introduced by Exel and Pardo when E is finite and sourceless.  
 
Tid og sted: 20. okt. 2017 11:15 - 12:00, Hurricane

Reyna Ramirez

Tid og sted: 19. okt. 2017 14:15 - 16:00, Ullevål
Tid og sted: 16. okt. 2017 12:45 - 13:45, Gates of Eden, Ullevål

Nicolai Stammeier (Oslo) will give a talk with title: The inner structure of boundary quotients of right LCM semigroups  

Abstract: In joint work with Roberto Conti, Stefano Rossi, and Valeriano Aiello, we use semidirect products built from algebraic dynamical systems to model right LCM semigroups to study various structural aspects in connection with a selection of distinguished subalgebras of the associated boundary quotients. Our two guiding examples are integral dynamics as considered in work of Barlak - Omland - Stammeier, and exact injective group endomorphisms of discrete abelian groups with finite cokernel as studied by Cuntz and Vershik.

Tid og sted: 12. okt. 2017 14:15 - 16:00, Ullevål
Tid og sted: 11. okt. 2017 13:15 - 14:00, Seminar room: "Hurricane", Matematisk Institutt, Ullevål stadion (Sognsveien 77 B, 2nd floor)

Eric Schaanning (Norges Bank) gives a lecture with the title: Interbank contagion and systemic risk: How robust are estimates?

Tid og sted: 27. sep. 2017 14:15 - 16:00, B638, NH Abels hus
Tid og sted: 21. sep. 2017 14:15 - 16:00, B638, NH Abels hus
Tid og sted: 19. sep. 2017 12:45 - 13:45, Gates of Eden

Adam Sørensen (UiO) will give a talk with title: C*-stable groups.

Abstract: In this talk we will look at when group C*-algebra have stable relations, which loosely speaking means that any almost representation of the group in a C*-algebra will be close to an exact representation. A particularly interesting case is if we assume the C*-algebra is finite dimensional. I will mostly discuss a collection of examples. The talk is based on ongoing joint work with Søren Eilers and Tatiana Shulman.