Norwegian version of this page

Events - Page 6

Time and place: , NHA107

C*-algebra seminar talk by Makoto Yamashita (University of Oslo)

Time and place: , University of Oslo

You are cordially welcome to participate in this three-day workshop on energy, climate, and ESG. As last year, the workshop will gather academics and practitioners from the industry, discussing the latest advances on the stochastics of risk measuring, modelling and managing, with a focus on energy systems, climate, and finance (ESG).

Key topics involve modelling uncertainty in weather and climate, optimisation problems related to energy systems to control emissions, as well as measuring risk factors related to climate change. 

There will be several invited talks by leading researchers as well as selected contributed talks by participants.

Time and place: , NHA 723 and Online
Time and place: , Abels Utsikt (NHA 1259)
Time and place: , Niels Henrik Abels hus, 9th floor

We discuss discretizations and solvers for a class of numerical methods for convection diffusion equations in arbitrary spatial dimensions. Targeted applications include the Nernst-Plank equations for transport of species in a charged media. We illustrate how such exponentially fitted methods are derived. A main step in proving error estimates is showing unisolvence for the quasi-polynomial spaces of differential forms defined as weighted spaces of differential forms with polynomial coefficients. We show that the unisolvent set of functionals for such spaces on a simplex in any spatial dimension is the same as the set of such functionals used for the polynomial spaces. We are able to prove our results without the use of Stokes' Theorem, which is the standard tool in showing the unisolvence of functionals in polynomial spaces of differential forms.
This is joint work with Shuonan Wu (Beijing University)

Time and place: , NHA 723 and Online
Time and place: , NHA B1120

I will talk about some new examples of varieties where the coniveau and strong coniveau filtrations are different. This is joint work with Jørgen Vold Rennemo.

Time and place: , Niels Henrik Abels hus, 8th floor

Douglas Wiens (Department of Mathematics and Statistical Sciences, University of Alberta, CAN) will give a talk on Wednesday April 19th at 14:15 in the Erling Sverdrups plass, Niels Henrik Abels hus, 8th floor.

Time and place: , NHA107

Operator algebra seminar by Alexander Müller-Hermes (University of Oslo)

Time and place: , Erling Sverdrups plass, Niels Henrik Abels hus, 8th floor

Variable selection methods based on L0 penalties have excellent theoretical properties to select sparse models in a high-dimensional setting. There exist modifications of BIC which either control the family wise error rate (mBIC) or the false discovery rate (mBIC2) in terms of which regressors are selected to enter a model. However, the minimization of L0 penalties comprises a mixed integer problem which is known to be NP hard and therefore becomes computationally challenging with increasing numbers of regressor variables. This is one reason why alternatives like the LASSO have become so popular, which involve convex optimization problems which are easier to solve. The last few years have seen some real progress in developing new algorithms to minimize  L0 penalties. We will compare the performance of these algorithms in terms of minimizing L0 based selection criteria.
Simulation studies covering a wide range of scenarios which are inspired by genetic association studies are used to compare the values of selection criteria obtained with different algorithms. Additionally some statistical characteristics of the selected models and the runtime of algorithms are compared.

Time and place: , Abels Utsikt (Niels Henrik Abels hus) and Online

Lecturer: Christa Cuchiero (University of Vienna)

Time and place: , NHA107

QOMBINE seminar talk by Vebjørn Hallberg Bakkestuen (UiO)

Time and place: , room 1259 (Abels Utsikt) - Niels Henrik Abels hus

Doctoral candidate Bjørn Skauli at the Department of Mathematics will be defending the thesis Rationality Properties of Some Hypersurfaces and Complete Intersections for the degree of Philosophiae Doctor.

Time and place: , Niels Henrik Abels hus, 9th floor

Constructing fast solution schemes often involves deciding which errors are acceptable and which approximations can be made for the sake of computational efficiency. Herein, we consider a mixed formulation of Darcy flow in porous media and take the perspective that the physical law of mass conservation is significantly more important than the constitutive relationship, i.e. Darcy's law. From this point of view, we propose an inexact solution technique that nevertheless guarantees local mass conservation. The method is based on first solving the mass balance equation and then computing a solenoidal correction using the curl of a potential field. We extend the method to flows in fractured porous media and present numerical experiments that indicate the efficiency of the scheme.

Time and place: , NHA B1120

Fano manifolds are complex projective manifolds having positive first Chern class. The positivity condition on the first Chern class has far reaching geometric and arithmetic implications. For instance, Fano manifolds are covered by rational curves, and families of Fano manifolds over one dimensional bases always admit holomorphic sections. In recent years, there has been some effort towards defining suitable higher analogues of the Fano condition. Higher Fano manifolds are expected to enjoy stronger versions of several of the nice properties of Fano manifolds.

In this talk, I will discuss higher Fano manifolds which are defined in terms of positivity of higher Chern characters. After a brief survey of what is currently known, I will present recent joint work with Carolina Araujo, Roya Beheshti, Kelly Jabbusch, Svetlana Makarova, Enrica Mazzon and Nivedita Viswanathan, regarding toric higher Fano manifolds. I will explain a strategy towards proving that projective spaces are the only higher Fano manifolds among smooth projective toric varieties.

Time and place: , Abels utsikt, Niels Henrik Abels Hus,12th floor

For millennia, origami and kirigami artists have used folds and cuts to create beautiful shapes from a simple sheet of paper. I will describe our recent scientific attempts to catch up with these remarkably imaginative arts phrased as inverse problems in physical geometry that aim to control the shape and rigidity of a thin surface. Using discrete operations that vary the number, size, orientation and coordination of folds and cuts, I will show how to create piecewise isometric kirigami and origami tessellations and control their local and global morphology and mechanical response, mixing experimental, computational and theoretical approaches.

Time and place: , NHA B1119
Enriched enumerative geometry is a new area in which we take results in enumerative geometry over the complex numbers and refine them to give results over any base field. The "refinements" in question recover the classical results over algebraically closed fields but may also include arithmetic information about the base field. In this talk, I'll give an overview of a proof of an enriched refinement of the Yau-Zaslow formula for counting rational curves on K3 surfaces. Joint work with Jesse Pajwani.
Time and place: , NHA 723 and Online
Time and place: , Abels Utsikt (NHA 1259)
Time and place: , NHA 723 and Online
Time and place: , NHA107

QOMBINE seminar by Eric Bedos (UiO)

Time and place: , Niels Henrik Abels hus, 9th floor

After a brief introduction to the main physical characteristics of tsunami events, the recently developed Iterative Filtering technique is presented and applied to the decomposition of tsunami signals from pressure and tide gauges. It is shown how these signals are successfully decomposed into components of different physical origins. Then, the time-frequency representation of these time series is obtained by using the IMFogram algorithm, which computes instantaneous amplitudes and frequencies for the previously obtained components. Finally, possible applications to tsunami science are discussed, such as possible applications to real time detection in early warning context.

Time and place: , Erling Sverdrups plass, Niels Henrik Abels hus, 8th floor

Estimates of environmental extremes are needed for a multitude of applications. For example, buildings, roads, bridges and dams must be designed to withstand extreme precipitation and flooding events of a certain size. Obtaining such estimates requires a combination of statistical theory and environmental process understanding to overcome data deficiencies: data on extremes are by definition sparse and regulations often require estimates for events that have yet to be observed. We will present approaches to obtain consistent estimates across spatial locations and accumulation periods, and discuss a few open questions on this topic. 

Time and place: , Niels Henrik Abels hus, 9th floor

OceanSun’s floating solar island consists of a hydro elastic membrane attached to a flexible torus, providing a more cost-efficient alternative with natural cooling of the panels leading to increased efficiency. The current research focuses on the seakeeping characteristics of OceanSun’s FSPV concept specifically. Wave induced loads are of particular interest, as the feasibility of offshore installation strongly depends on environmental loads. Important responses of the membrane based FSPV are identified by the development of a global model based on linear potential flow theory, and linearly pre-tensioned membrane motions. Based on theory formulated by Grøn (2022), a modal analysis is used to describe the vertical displacement of the membrane-floater system. A numerical implementation of the theory in WAMIT is compared to experimental results from model-scaled tests.

Time and place: , NHA107

QOMBINE seminar talks by Delphine Martres (University of Oslo) and Alexander Müller-Hermes (University of Oslo)