Department of Mathematics
Recent Submissions
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A 3-D numerical model of the influence of meanders on groundwater discharge to a gaining stream in an unconfined sandy aquifer
(Journal article, 2017)Groundwater discharge to streams depends on stream morphology and groundwater flow direction, but are not always well understood. Here a 3-D groundwater flow model is employed to investigate the impact of meandering stream ... -
Diagram spaces and multiplicative structures
(Doctoral thesis, 2022-01-14)This thesis explores diagrammatic E_n structures as models for E_n spaces. Paper A: Braided injections and double loop spaces. (Christian Schlichtkrull and Mirjam Solberg.) We consider a framework for representing ... -
A nonlinear multi-scale model for blood circulation in a realistic vascular system
(Journal article; Peer reviewed, 2021)In the last decade, numerical models have become an increasingly important tool in biological and medical science. Numerical simulations contribute to a deeper understanding of physiology and are a powerful tool for better ... -
Epistemic uncertainty quantification in deep learning classification by the Delta method
(Journal article; Peer reviewed, 2021)The Delta method is a classical procedure for quantifying epistemic uncertainty in statistical models, but its direct application to deep neural networks is prevented by the large number of parameters . We propose a low ... -
The Role of Wettability Alteration in Subsurface CO2 Storage: Modeling and Numerical Analysis
(Doctoral thesis, 2021-12-06)This dissertation is aimed to provide mathematical frameworks to assess the large-scale deployment of CO2 in a subsurface formation, where the formation wettability is assumed to be altering through exposure time to the ... -
Coherence for Monoidal and Symmetric Monoidal Groupoids in Homotopy Type Theory
(Doctoral thesis, 2021-12-03)Homotopy Type Theory (HoTT) is a variant of Martin-Löf Type Theory (MLTT) developed in such a way that types can be interpreted as infinity-groupoids, where the iterated construction of identity types represents the different ... -
A study of the influence of vorticity, capillarity and slope angle on the properties of shoaling and breaking waves
(Doctoral thesis, 2021-10-28)Fluid motion and wave patterns have fascinated humans for centuries if not millennia. Water waves have been studied out of curiosity such as observing the ripples created by a stone dropped in a pond as well as practical ... -
Effective permeability of deformation bands in fault damage zones – Can deformation bands reduce the risk of fault leakage?
(SINTEF Proceedings;7, Chapter, 2021)Faults are major geological structures that can dominate the flow paths in subsurface reservoirs by, e.g., connecting otherwise unconnected layers. In CO2 storage sites where the faults act as the main structural trap, the ... -
Robust Optimization for Sequential Field Development Planning
(Doctoral thesis, 2021-09-24)To achieve high profitability from an oil field, optimizing the field development strategy (e.g., well type, well placement, drilling schedule) before committing to a decision is critically important. The profitability at ... -
Improving Sequential Decisions – Efficiently Accounting for Future Learning
(Journal article; Peer reviewed, 2021)In sequential field development planning, past decisions not only directly affect the maximum achievable expected NPV but also influence the future information that can be used to reduce geological uncertainty. To act ... -
Brauer Groups of Bielliptic Surfaces and Twisted Derived Equivalences
(Doctoral thesis, 2021-08-30)This thesis focuses on two interrelated projects. The first project concerns the study of bielliptic surfaces, their Brauer groups and the pullback maps from their Brauer groups to those of their canonical covers. We prove ... -
Moduli of non-standard Nikulin surfaces in low genus
(Journal article; Peer reviewed, 2020)Primitively polarized genus g Nikulin surfaces (S, M, H) are of two types, that we call standard and non-standard depending on whether the lattice embedding Z[H] ⊕⊥ N ⊂ Pic S is primitive. Here H is the genus g polarization ... -
Conditioning reservoir models on vast data sets
(Doctoral thesis, 2021-09-09)History matching is a valuable process to obtain better models and a more reliable forecast in oil reservoir applications. In such processes, one conditions the simulation models on the observed data from the field. One ... -
Impact of parents' education on variation in hospital admissions for children: a population-based cohort study
(Journal article; Peer reviewed, 2021)Objectives To assess the impact of parental educational level on hospital admissions for children, and to evaluate whether differences in parents' educational level can explain geographic variation in admission rates. ... -
Fast robust optimization using bias correction applied to the mean model
(Peer reviewed; Journal article, 2021)Ensemble methods are remarkably powerful for quantifying geological uncertainty. However, the use of the ensemble of reservoir models for robust optimization (RO) can be computationally demanding. The straightforward ... -
Admissibility conditions for Riemann data in shallow water theory
(Journal article; Peer reviewed, 2020)Consideration is given to the shallow-water equations, a hyperbolic system modeling the propagation of long waves at the surface of an incompressible inviscible fluid of constant depth. It is well known that the solution ... -
Pairwise local Fisher and naive Bayes: Improving two standard discriminants
(Journal article; Peer reviewed, 2020)The Fisher discriminant is probably the best known likelihood discriminant for continuous data. Another benchmark discriminant is the naive Bayes, which is based on marginals only. In this paper we extend both discriminants ... -
Well-Posedness for a Whitham–Boussinesq System with Surface Tension
(Journal article; Peer reviewed, 2020)We regard the Cauchy problem for a particular Whitham–Boussinesq system modelling surface waves of an inviscid incompressible fluid layer. The system can be seen as a weak nonlocal dispersive perturbation of the shallow ... -
Nonlinear Spectral Analysis: A Local Gaussian Approach
(Journal article; Peer reviewed, 2020)The spectral distribution f(ω) of a stationary time series {Yt}t∈Z can be used to investigate whether or not periodic structures are present in {Yt}t∈Z, but f(ω) has some limitations due to its dependence on the autocovariances ... -
Extreme wave runup on a steep coastal profile
(Journal article; Peer reviewed, 2020)It is shown that very steep coastal profiles can give rise to unexpectedly large wave events at the coast. We combine insight from exact solutions of a simplified mathematical model with photographs from observations at ...
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