Gjesteforelesninger og seminarer - Side 8

QOMBINE seminar by Joel Rajakumar (University of Maryland)

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

QOMBINE seminar by Randy Lin (University of Amsterdam)

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.

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.

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.

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.

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).

The Tien Mai is currently a postdoc at FHI. He has held postdoc positions in statistics at NTNU (Trondheim) and in biostatistics at UiO (OCBE). His research spans statistics and machine learning, with a particular interest in PAC-Bayesian analysis. He holds a PhD in Statistics from CREST-ENSAE-ParisTech/Paris Saclay and University College Dublin.

Mauro Di Nasso, University of Pisa, will give a talk in the Logic Seminar

Anders Kvellestad is a Researcher in theoretical physics at the Department of Physics and head of the GAMBIT Collaboration. His research focuses on how to test new theories against results from the Large Hadron Collider and other experiments, using both frequentist and Bayesian approaches, and the computational challenges related to this work. Anders completed his PhD at the University of Oslo in 2015 and has since held postdoctoral positions at Nordita (Stockholm), Imperial College London and UiO.

Since 2021 he has lead the GAMBIT Collaboration, an international collaboration of physicists working on global fit analyses. He is also part of the PLUMBIN’ project at UiO, which aims to develop new computational and statistical tools for particle physics and beyond.

Multiphase flow in pipes is very complex due to the large number of parameters involved. Differences in phase combinations (e.g. gas-liquid-liquid) and inclination angle can significantly affect the flow regime within the pipe. This in turn can lead to differences in demand on pressure support systems or other facilities. Therefore, accurate estimation of the flow behaviour is crucial for equipment design and operational safety of the production. In this talk, various experimental measurement techniques for monitoring multiphase flow in pipes will be discussed that are currently in use at the Well Flow Loop installation at IFE, Kjeller. In addition, some results from the ongoing research project focusing on flow in steeply inclined pipes will be shown.

Based on the preprint Bhatt, Iyengar, Ma - Regular rings and perfectoid algebras. Notes for the lecture here.