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Recurrent Lorentzian Weyl Spaces
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-07-02)We find the local form of all non-closed Lorentzian Weyl manifolds (M,c,∇) with recurrent curvature tensor. The recurrent curvature tensor turns out to be weighted parallel, i.e., the obtained spaces provide certain generalization of locally symmetric affine spaces for the Weyl geometry. If the dimension of the manifold is greater than 3, then the conformal structure is flat, and the recurrent Weyl ... -
Basal Melting and Oceanic Observations Beneath Central Fimbulisen, East Antarctica
(Journal article; Tidsskriftartikkel; Peer reviewed, 2025-03-11)Basal melting of ice shelves is fundamental to Antarctic ice sheet mass loss, yet direct observations remain sparse. We present the first year-round melt record (2017–2021) from a phase-sensitive radar on Fimbulisen, one of the fastest flowing ice shelves in Dronning Maud Land, East Antarctica. The observed long-term mean ablation rate at 350 m depth below the central ice shelf was 1.0 ± 0.5 m ... -
Pigghåtoktet 2024 - Et samarbeidstokt mellom Havforskningsinstituttet og Måløy Videregående Skole, med opplæringsfartøyet MS Skulebas
(Research report; Forskningsrapport, 2025)Pigghå er en datafattig og rødlistet art som historisk har gitt grunnlag for et stort fiskeri med årlige landinger på mer enn 40 000 tonn i mer enn 40 år. Etter langvarig overfiske og etterfølgende bestandssammenbrudd har det nå i en del år vært tegn til vekst i bestanden. I 2020 tok Måløy videregående skole, som eier en autoline/garnbåt, kontakt med Havforskningsinstituttet og presenterte et ønske ... -
Identifying conditions leading to power quality events in Arctic Norway: Feature selection
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-26)Higher penetration of renewable energy and increased electricity consumption makes delivering a reliable power supply a complex task. Power system operators are nevertheless required to provide a reliable power supply with a power quality within specified limits. Power quality events can cause malfunctioning of sensitive equipment for consumers in the distribution network. Communities in the periphery ... -
Data on Physical Properties of Sea Ice in the Northern Barents Sea and Adjacent Arctic Basin From the Nansen Legacy Project
(Journal article; Tidsskriftartikkel; Peer reviewed, 2025-03-17)Recent decline of sea ice in the Barents Sea represents a clear manifestation of the ongoing Arctic warming. This study presents a compilation of data sets on sea ice physics acquired during 2018–2022 during Nansen Legacy—a Norwegian multidisciplinary national research programme that focused on the northern Barents Sea. The data were acquired using a variety of methods such as sea ice coring, thickness ... -
Unifying heterogeneous hyperspectral databases for in vivo human brain cancer classification: Towards robust algorithm development
(Journal article; Tidsskriftartikkel; Peer reviewed, 2025-02-18)Background and objective - Cancer is one of the leading causes of death worldwide, and early and accurate detection is crucial to improve patient outcomes. Differentiating between healthy and diseased brain tissue during surgery is particularly challenging. Hyperspectral imaging, combined with machine and deep learning algorithms, has shown promise for detecting brain cancer in vivo. The present ... -
Regulated Power Supply with High Power Factor for Hyperspectral Imaging Applications
(Journal article; Tidsskriftartikkel; Peer reviewed, 2025-01-22)Illumination is a crucial factor in hyperspectral imaging systems. In this respect, this work is focused on analyzing the influence of the light power source in acquiring hyperspectral images. To this end, a custom regulated power supply was designed and developed. This power supply was then integrated into a hyperspectral acquisition system, and several light stability measurements were conducted. ... -
Three-dimensional modeling of diffusion-gravity flows in ice-covered lakes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2025-03-03)When a solid inclined surface is submerged in a quiescent stratified fluid, the combined effects of buoyancy forces and diffusion generate an upward gravity flow along the slope. Thermally stratified ice-covered lakes remain in a nearly quiescent state and are potentially prone to this effect. We use three-dimensional hydrodynamic modeling to investigate the diffusion-gravity flow and its impact on ... -
REFLECTIONS ON ABSTRACTION IN A WORLD WHERE ATTACHMENT TO PLACE MATTERS
(Chapter; Bokkapittel, 2025-01)In an earlier reflection, we drew on our experiences, especially in Indigenous contexts, to consider how detachment connects with abstraction (Huru, Andersson & Wagner, 2023). We described abstraction as a process that attaches an idea to an experience—e.g., the realization that a line carved into a bone can represent a real thing, or five such lines, or the symbol 5 referring to the five lines. But ... -
Spin representations and binary numbers
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024)We consider a construction of the fundamental spin representations of the simple Lie algebras so(n) in terms of binary arithmetic of fixed width integers. This gives the spin matrices as a Lie subalgebra of a Z-graded associative algebra (rather than the usual N-filtered Clifford algebra). Our description gives a quick way to write down the spin matrices, and gives a way to encode some extra structure, ... -
Making the motivic group structure on the endomorphisms of the projective line explicit
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-12-13)We construct a group structure on the set of pointed naive homotopy classes of scheme morphisms from the Jouanolou device to the projective line. The group operation is defined via matrix multiplication on generating sections of line bundles and only requires basic algebraic geometry. In particular, it is completely independent of the construction of the motivic homotopy category. We show that ... -
Projections of precipitation and temperatures in Greenland and the impact of spatially uniform anomalies on the evolution of the ice sheet
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-12-12)Simulations of the Greenland ice sheet (GrIS) at millennial timescales and beyond often assume spatially and temporally uniform temperature anomalies and precipitation sensitivities over these timescales or rely on simple parameterisation schemes for the precipitation rates. However, there is no a priori reason to expect spatially and temporally uniform sensitivities across the whole GrIS. Precipitation ... -
Evaluating an accelerated forcing approach for improving computational efficiency in coupled ice sheet–ocean modelling
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-11-21)Coupled ice sheet–ocean models are increasingly being developed and applied to important questions pertaining to processes at the Greenland and Antarctic Ice Sheet margins, which play a pivotal role in ice sheet stability and sea level rise projections. One of the challenges of such coupled modelling activities is the timescale discrepancy between ice and ocean dynamics. This discrepancy, combined ... -
Equivariant algebraic and semi-algebraic geometry of infinite affine space
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-12-03)We study Sym(∞)-orbit closures of non-necessarily closed points in the Zariski spectrum of the infinite polynomial ring C[xij : i ∈ N, j ∈ [n]]. Among others, we characterize invariant prime ideals in this ring. Furthermore, we study projections of basic equivariant semi-algebraic sets defined by Sym(∞) orbits of polynomials in R[xij : i ∈ N, j ∈ [n]]. For n = 1 we prove a quantifier elimination ... -
Optimization of trigonometric polynomials with crystallographic symmetry and spectral bounds for set avoiding graphs
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-11-05)We provide a new approach to the optimization of trigonometric polynomials with crystallographic symmetry. This approach widens the bridge between trigonometric and polynomial optimization. The trigonometric polynomials considered are supported on weight lattices associated to crystallographic root systems and are assumed invariant under the associated reflection group. On one hand the invariance ... -
The consequences of tritium mix for simulated ion cyclotron emission spectra from deuterium-tritium plasmas
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-10-16)Measurements of ion cyclotron emission (ICE) are obtained from most large magnetically confined fusion plasma experiments, and may be used in future to quantify properties of the fusion-born alpha-particle population in deuterium-tritium (DT) plasmas in ITER. ICE is driven by spatially localised, strongly non-Maxwellian, minority energetic ion populations which relax collectively under the ... -
Liftable Point-Line Configurations: Defining Equations and Irreducibility of Associated Matroid and Circuit Varieties
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-09-28)We study point-line configurations through the lens of projective geometry and matroid theory. Our focus is on their realization spaces, where we introduce the concepts of liftable and quasi-liftable configurations, exploring cases in which an n-tuple of collinear points can be lifted to a nondegenerate realization of a point-line configuration. We show that forest configurations are liftable ... -
Comments on: Data integration via analysis of subspaces (DIVAS)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-06-06)We would like to start by saying that this is a very interesting paper that outlines a powerful tool that can be applied in a wide range of areas. In our discussion, we focus on how the novel approach potentially can improve classification results in hard tasks within e.g., medicine and geoscience. In such situations, where it is hard to make precise predictions, it is natural to acquire information ... -
Understanding Coherent Turbulence and the Roll-Cell Transition With Lagrangian Coherent Structures and Frame-Indifferent Fluxes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-09-18)We present the first analysis of frame-indifferent (objective) fluxes and material vortices in Large Eddy Simulations of atmospheric boundary layer turbulence. We extract rotating fluid features that maintain structural coherence over time for near-neutral, transitional, and convective boundary layers. In contrast to traditional analysis of coherent structures in turbulent boundary layers, we provide ... -
Lie Admissible Triple Algebras: The Connection Algebra of Symmetric Spaces
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-07-25)Associated to a symmetric space there is a canonical connection with zero torsion and parallel curvature. This connection acts as a binary operator on the vector space of smooth sections of the tangent bundle, and it is linear with respect to the real numbers. Thus the smooth section of the tangent bundle together with the connection form an algebra we call the connection algebra. The constraints ...
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