Previous events - Page 22

Felleskollokvium by Prof. Sverre Holm, Dept. of Physics, UiO

This year's Hassel lecture is headed by Professor Veronique Van Speybroeck. The first day Professor Speybroeck will present the lecture "Operando modeling of functional nanostructured materials for sustainable chemistry, nanosensing and clean energy."

by

Bill Lukens

James Madison University (USA)

Hosted by Anne Hope Jahren

Online changepoint detection algorithms based on likelihood-ratio tests have excellent statistical properties. However, a simple exact online implementation is computationally infeasible as, at time T, it involves considering O(T) possible locations for the change. To improve on this, we use functional pruning ideas to reduce the set of changepoint locations that need to be stored at time T to approximately log T. Furthermore, we show how we need only maximise the likelihood-ratio test statistic over a small subset of these possible locations. Empirical results show that the resulting exact online algorithm, which can detect changes under a wide range of models, has a constant-per-iteration cost on average. We consider applications of this algorithm in the context of detecting increases in radiation count that represent astronomical or nuclear events of interest.

Title: Using simple integrated assessment models to explore human and earth system feedbacks

Speaker: Sibel Eker, Radboud University and International Institute for Applied Systems Analysis (IIASA)

The Kolmogorov N-width describes the best possible error one can achieve by elements of an N-dimensional linear space. Its decay has extensively been studied in Approximation Theory and for the solution of Partial Differential Equations (PDEs). Particular interest has occurred within Model Order Reduction (MOR) of parameterized PDEs e.g. by the Reduced Basis Method (RBM). While it is known that the N-width decays exponentially fast (and thus admits efficient MOR) for certain problems, there are examples of the linear transport and the wave equation, where the decay rate deteriorates to N^-1/2. On the other hand, it is widely accepted that a smooth parameter dependence admits a fast decay of the N-width. However, a detailed analysis of the influence of properties of the data (such as regularity or slope) on the rate of the N-width seems to lack. In this work, we use techniques from Fourier Analysis to derive exact representations of the N-width in terms of initial and boundary conditions of the linear transport equation modeled by some function g for half-wave symmetric data. For arbitrary functions g, we derive bounds and prove that these bounds are sharp. In particular, we prove that the N-width decays as c_r N^(-r-1/2) for functions in the Sobolev space, g ∈ H^r. Our theoretical investigations are complemented by numerical experiments which confirm the sharpness of our bounds and give additional quantitative insigh.

Employees at the University of Oslo (UiO) and Oslo University Hospital (OUS), who will relocate to the Life Sciences Building when it is completed in 2027, are invited to the seminar "How do we live together?"

The workshop Molecular Quantum Dynamics is organized as part of the Centre for Advanced Study (CAS) project Attosecond Quantum Dynamics Beyond the Born–Oppenheimer approximation, and will cover a broad range of topics. We welcome the participants to the beautiful and historical hotel Lysebu, situated at the rooftop of Oslo.

Every second Tuesday, CBA members gather for lunch and a talk. On May 23rd 2023, we have an early career presentation given by two PhD students Eira Carlsen and Elisabeth Wörner.

Doctoral candidate Alise Danielle Midtfjord at the Department of Mathematics will be defending the thesis Machine learning methods for safety-critical systems with time dependency for the degree of Philosophiae Doctor.

Audun Jøsang (DIS/SEC) and Magdalena Ivanovska (BI) will present the theory of subjective logic and applications of reasoning under uncertainty.

Welcome to our GEOHYD Lunch Seminar Friday 12th of May @ 12:15 in Aud. 2, Geology building, or via video link using Zoom. The seminar is held by Ugo Nanni, GEO, UiO.

Doctoral candidate Emilie Willoch Olstad at the Department of Pharmacy, Faculty of Mathematics and Natural Sciences, is  defending the thesis "Prenatal Medication Exposure, DNA Methylation and Child Neurodevelopment" for the degree of Philosophiae Doctor.

Gina Panopoulou, Assistant Professor at Division of Astronomy and Plasma Physics, Chalmers University of Technology, Gothenburg.

Is it difficult to set aside time to write? The Academic Writing Centre organsises structured writing sessions for doctoral students.

Donaldson-Thomas theory is a well-celebrated modern tool for studying Calabi-Yau threefolds. In this theory, one studies weighted Euler characteristics of moduli spaces of sheaves on threefolds. Elliptic genus on the other hand is a refinement of Euler characteristic motivated by a hypothesis of Witten. In this talk I will discuss and present evidence of a surprising relationship between the two. That is, a relationship between the Elliptic genus of sheaves surfaces and the Donaldson-Thomas theory of elliptically fibred threefolds.

Title: A Lagrangian view of MOSAIC, the largest polar expedition: one year of atmospheric transport in the Arctic seen through trajectories

Speaker: Silvia Bucci, University of Vienna

Each spring, near the date of Svein Rosseland's birthday, the Institute of Theoretical Astrophysics invites everyone to a guest lecture by an internationally renowned astrophysicist as a remembrance for our great astrophysicist Svein Rosseland (1894-1985), founder of our institute.

This talk will introduce a recent suite of research focussed on the statistical detection of anomalous structure in online data settings. The challenge of efficiently identifying anomalies in data sequences is an important statistical problem that now arises in many applications. Whilst there has been substantial work aimed at making statistical analyses robust to outliers, or point anomalies, there has been much less work on detecting anomalous segments, or collective anomalies, particularly in those settings where point anomalies might also occur. This is the challenge we seek to address, demonstrating theoretical results in both the offline and online settings as well as introducing some applied case studies.

Welcome to a new GeoWednesday. This month Adriano Mazzini will give a talk about the the Arctic permafrost.

The NorMIC series of workshops aims to teach biological researchers (PhD students, engineers, postdocs and young PIs) the principles of biological microscopes and image processing.

Title: Turbulent transport of momentum and heat in the atmospheric surface layer: new perspectives on an old subject

Speaker: Dan Li, Boston University

Welcome to our GEOHYD Lunch Seminar Friday 5th of May @ 12:15 in Aud. 2, Geology building, or via video link using Zoom. The seminar is held by Sebastian Westermann, GEO, UiO.