Tidlegare gjesteforelesninger og seminarer - Side 11

Dr. Lorenzo Amati, INAF - Astrophysics and Space Science Observatory of Bologna (OAS), Italy

QOMBINE seminar by Joel Rajakumar (University of Maryland)

Til minne om Norges fremste astrofysiker og grunnlegger av Institutt for teoretisk astrofysikk, professor Svein Rosseland (1894 – 1985), arrangerer Institutt for teoretisk astrofysikk en Rosselandforelesning hvert år.

Paolo Giordani is a professor of Financial Econometrics at the Norwegian Business School in Oslo.

His main research interests are statistical machine learning, Bayesian inference, and volatility

By Kristian Andersen and Herwig Leirs

QOMBINE seminar by Randy Lin (University of Amsterdam)

A morning seminar with short talks about the coastal ecosystem and the new MACROCOP project 

PhD candidate Aleksandr Berezovski at the Department of Biosciences, Faculty of Mathematics and Natural Sciences, is defending the thesis 'Optical effects and coastal darkening caused by terrestrially-derived dissolved organic matter' for the degree of PhD.

Uneven solid surfaces are ubiquitous in Nature and can significantly impact fluid flow over them. In this presentation I will discuss two different configurations were the wall unevenness govern fluid transport.
First, I will consider wet ceilings. When liquid is coated on an upside-down surface, it destabilizes to form pendant drops surrounded by a thin film of liquid. I will show that these pendant drops ‘feel’ surface defects even though they have no contact line. The defects induce a gravito-capillary pinning-like force that can be harnessed to control the drop motion.
Second, I will consider hairy pipes. Many biological surfaces are covered with long and elastic filaments or ‘hairs’. I will show that when a fluidic channel is covered with hairs, the hydraulic resistance can become non-linear. This non-linearity is mediated by the hair flexibility and degree of channel obstruction and can be rationalized with a multi-scale model.

Bo Andersen, Guest Researcher at Institute of Theoretical Astrophysics, UiO.

Boreal lakes: analogous of the ancient ocean?

Arnt-Børre Salberg is a Chief Research Scientist at the Norsk Regnesentral, affiliated with the Department of BAMJO (Image Analysis, Machine Learning and Earth Observation).  

His research primarily focuses on the developing deep learning, computer vision, and remote sensing methods to image data. This includes work on forest mapping and monitoring, marine science applications, coastal habitat mapping, foundation models, and analysis of data from various sensors like satellites, seismic, and marine echosounders.

It is time for our monthly mingle meeting. Students and employees at the institute will meet up for informal chat.

I will explain how to use the motivic volume formula and toric degenerations to study the rationality problem for complete intersections in Grassmannians, in particular Gr(2,5).

Hélène Ruffieux is a Senior Research Fellow at the MRC Biostatistics Unit, University of Cambridge. She holds a PhD in Mathematics from EPFL, Switzerland. Her research interests broadly lie in the development of Bayesian methods and their application to open problems in biomedicine, with a focus on scalable hierarchical modelling approaches for variable selection, latent structure discovery and network estimation, in high-dimensional or temporal data settings.

Nils Siemonsen, Associate Research Scholar in the Gravity Initiative at Princeton University.

We study rationality questions for the Fano schemes of non-maximal linear spaces on a smooth complete intersection X of two quadrics, especially over non-closed fields. We start by showing that they are all geometrically rational. We then ask their rationality over k and analyze in details the case of second maximal linear spaces. In particular, we generalize results of Hassett-Tschinkel and Benoist-Wittenberg when X has odd dimension, and extend work of Hassett-Kollár-Tschinkel when X has even dimension and k = R. This is joint work with Lena Ji.

Elena Mamonova, PhD fellow at the Centre for Planetary Habitability (PHAB), University of Oslo

In recent years there have been numerous studies on floating films of non-Newtonian fluids due to their application to model the stability of floating ice shelves. Sayag & Worster (2019) showed theoretically that expanding cylinders of shear-thinning fluids can become non-axisymmetrical at the advancing fluid edge, driven by their non-Newtonian rheology. This instability carries over to radially spreading, thinning films of the same material when that fluid floats on a deeper bath of less viscous, but denser, Newtonian fluid.

Experimentally validating these theoretical results has, however, been challenging. Initial experimental exploration using Xanthan gum floating on a dense bath of salt solution shows dramatic non-axisymmetrical patterns. These patterns have their origin in interfacial effects, rather than Sayag & Worster's instability, with the expanding film appearing to fracture under extensional stresses at the fluid edge (Ball et al., 2022).

In this talk, I will present a new set of experiments exploring the instability, in which spreading films of aqueous suspensions of Carbopol and Xanthan gum are floated on a bath of more dense perfluorinated oil. The immiscibility between the bath and floating film prevents the failure of the material under tension and allows comparison against theoretical predictions from a shallow film model (Ball & Balmforth, 2021; Ball & Balmforth 2025).

George Cherry, Rosseland Centre for Solar Physics, ITA, UiO