Siste publikasjoner

• Arumugam, Gurusamy & Erhardt, André Henrik (2020). Existence of weak solutions to a certain homogeneous parabolic Neumann problem involving variable exponents and cross-diffusion. Journal of Elliptic and Parabolic Equations.  ISSN 2296-9020. . doi: 10.1007/s41808-020-00078-6
• Zengaffinen, Thomas; Løvholt, Finn; Pedersen, Geir Kleivstul & Muhari, Abdul (2020). Modelling 2018 Anak Krakatoa Flank Collapse and Tsunami: Effect of Landslide Failure Mechanism and Dynamics on Tsunami Generation. Pure and Applied Geophysics.  ISSN 0033-4553. . doi: 10.1007/s00024-020-02489-x Vis sammendrag

  The 2018 Anak Krakatoa volcano flank collapse generated a tsunami that impacted the Sunda Strait coastlines. In the absence of a tsunami early warning system, it caused several hundred fatalities. There are ongoing discussions to understand how the failure mechanism of this event affected landslide dynamics and tsunami generation. In this paper, the sensitivity to different failure scenarios on the tsunami generation is investigated through numerical modelling. To this end, the rate of mass release, the landslide volume, the material yield strength, and orientation of the landslide failure plane are varied to shed light on the failure mechanism, landslide evolution, and tsunami generation. We model the landslide dynamics using the depth-averaged viscoplastic flow model BingClaw, coupled with depth-averaged long wave and shallow water type models to simulated tsunami propagation. We are able to match fairly well the observed tsunami surface elevation amplitudes and inundation heights in selected area with the numerical simulations. However, as observed by other authors, discrepancies in simulated and observed arrival times for some of the offshore gauges are found, which raises questions related to the accuracy of the available bathymetry. For this purpose, further sensitivity studies changing the bathymetric depth near the source area are carried out. With this alteration we are also able to match better the arrival times of the waves.

• Erhardt, André Henrik; Mardal, Kent-Andre & Schreiner, Jakob Emil (2020). Dynamics of a neuron-glia system: the occurrence of seizures and the influence of electroconvulsive stimuli. Journal of Computational Neuroscience.  ISSN 0929-5313.  48, s 229- 251 . doi: 10.1007/s10827-020-00746-5
• Stoltenberg, Emil Aas; Nordeng, Hedvig Marie Egeland; Ystrøm, Eivind & Samuelsen, Sven Ove (2020). The cure model in perinatal epidemiology. Statistical Methods in Medical Research.  ISSN 0962-2802. . doi: 10.1177/0962280220904092
• Kristiansen, Lars & Simonsen, Jakob Grue (2020). On the Complexity of Conversion between Classic Real Number Representations.. Lecture Notes in Computer Science (LNCS).  ISSN 0302-9743.
• Kristiansen, Lars & Murwanashyaka, Juvenal (2020). On Interpretability between some weak essential undecidable theories.. Lecture Notes in Computer Science (LNCS).  ISSN 0302-9743.
• Zengaffinen, Thomas; Løvholt, Finn; Pedersen, Geir Kleivstul & Harbitz, Carl Bonnevie (2020). Effects of rotational submarine slump dynamics on tsunami-genesis – new insight from idealized models and the 1929 Grand Banks event. Geological Society Special Publication.  ISSN 0305-8719. . doi: 10.1144/SP500-2019-201 Fulltekst i vitenarkiv. Vis sammendrag

  Sediment slumps are known to have generated important tsunamis such as the 1998 Papua New Guinea (PNG) and the 1929 Grand Banks events. Tsunami modellers commonly use solid blocks with short run-out distances to simulate these slumps. While such methods have the obvious advantage of being simple to use, they offer little or no insight into physical processes that drive the events. The importance of rotational slump motion to tsunamigenic potential is demonstrated in this study by employing a viscoplastic landslide model with Herschel-Bulkley rheology. A large number of simulations for different material properties and landslide configurations are carried out to link the slump's deformation, rheology, its translational and rotational kinematics, to its tsunami-genesis. The yield strength of the slump is shown to be the primary material property that determines the tsunami-genesis. This viscoplastic model is further employed to simulate the 1929 Grand Banks tsunami using updated geological source information. The results of this case study suggest that the viscoplastic model can be used to simulate complex slump induced tsunami. The simulations of the 1929 Grand Banks event also indicate that a pure slump mechanism is more tsunamigenic than a corresponding translational landslide mechanism.

• Kristiansen, Lars & Murwanashyaka, Juvenal (2020). First-Order Concatenation Theory with Bounded Quantifiers (Preprint). arXiv.org.  ISSN 2331-8422.
• Rauter, Matthias; Barker, T. & Fellin, W. (2020). Granular viscosity from plastic yield surfaces: The role of the deformation type in granular flows. Computers and geotechnics.  ISSN 0266-352X.  122 . doi: 10.1016/j.compgeo.2020.103492 Fulltekst i vitenarkiv. Vis sammendrag

  Numerical simulations of granular flows with Navier–Stokes type models emerged in the last decade, challenging the well established depth-averaged models. The structure of these equations allows for extension to general rheologies based on complex and realistic constitutive models. Substantial effort has been put into describing the effect of the shear rate, i.e. the magnitude of the velocity gradient, on the shear stress. Here we analyse the effect of the deformation type. We apply the theories of Mohr–Coulomb and Matsuoka–Nakai to calculate the stresses under different deformation types and compare results to the theory of Drucker–Prager, which is formulated independently of the deformation type. This model is particularly relevant because it is the basis for many granular rheologies, such as the –rheology. All models have been implemented into the open-source toolkit OpenFOAM® for a practical application. We found that, within the context of these models, the deformation type has a large influence on the stress. However, for the geometries considered here, these differences are limited to specific zones which have little influence on the landslide kinematics. Finally we are able to give indicators on when the deformation type should be considered in modelling of landslides and when it can be neglected.

• Støle-Hentschel, Susanne; Trulsen, Karsten; Nieto Borge, José Carlos & Olluri, Shkurte (2020). Extreme Wave Statistics in Combined and Partitioned Windsea and Swell. Water Waves.  ISSN 2523-367X.  2, s 169- 184 . doi: 10.1007/s42286-020-00026-w
• Normann, Dag & Sanders, Sam (2020). Pincherle's theorem in reverse mathematics and computability theory. Annals of Pure and Applied Logic.  ISSN 0168-0072.  171(5) . doi: 10.1016/j.apal.2020.102788
• Landet, Tormod; Mardal, Kent-Andre & Mortensen, Mikael (2020). Slope limiting the velocity field in a discontinuous Galerkin divergence-free two-phase flow solver. Computers & Fluids.  ISSN 0045-7930.  196 . doi: 10.1016/j.compfluid.2019.104322
• Kristiansen, Lars & Murwanashyaka, Juvenal (2020). First-Order Concatenation Theory with Bounded Quantifiers. Archive for Mathematical Logic.  ISSN 0933-5846. . doi: 10.1007/s00153-020-00735-6
• Patrizi, Francesco & Dokken, Tor (2020). Linear dependence of bivariate Minimal Support and Locally Refined B-splines over LR-meshes. Computer Aided Geometric Design.  ISSN 0167-8396.  77 . doi: 10.1016/j.cagd.2019.101803 Fulltekst i vitenarkiv. Vis sammendrag

  The focus on locally refined spline spaces has grown rapidly in recent years due to the need in Isogeometric Analysis (IgA) of spline spaces with local adaptivity: a property not offered by the strict regular structure of tensor product B-spline spaces. However, this flexibility sometimes results in collections of B-splines spanning the space that are not linearly independent. In this paper we address the minimal number of Minimal Support B-splines (MS B-splines) and of Locally Refined B-splines (LR B-splines) that can form a linear dependence relation. We show that such minimal numbers are six for MS B-splines and eight for LR B-splines. Further results are established to help detecting collections of B-splines that are linearly independent.

• Arumugam, Gurusamy; Erhardt, André Henrik; Eswaramoorthy, Indurekha & Krishnan, Balachandran (2020). Existence of weak solutions to the Keller-Segel chemotaxis system with additional cross-diffusion. Nonlinear Analysis: Real world applications.  ISSN 1468-1218.  54 . doi: 10.1016/j.nonrwa.2020.103090 Fulltekst i vitenarkiv.
• Rabault, Jean; Sutherland, Graig; Gundersen, Olav; Jensen, Atle; Marchenko, Aleksey & Breivik, Øyvind (2020). An open source, versatile, affordable waves in ice instrument for scientific measurements in the Polar Regions. Cold Regions Science and Technology.  ISSN 0165-232X.  170 . doi: 10.1016/j.coldregions.2019.102955
• Trulsen, Karsten; Raustøl, Anne; Jorde, Stian & Rye, Lisa Bæverfjord (2020). Extreme wave statistics of long-crested irregular waves over a shoal. Journal of Fluid Mechanics.  ISSN 0022-1120.  882 . doi: 10.1017/jfm.2019.861 Fulltekst i vitenarkiv. Vis sammendrag

  We report laboratory experiments of long-crested irregular water surface waves propagating over a shoal. For a sufficiently shallow shoal we find that the surface elevation can have a local maximum of skewness and kurtosis above the shallower part of the shoal close to the edge on the incoming side, and a local minimum of skewness over the downward slope on the lee side of the shoal. We find that the horizontal fluid velocity can have a local maximum and minimum of skewness at the same locations as those for the surface elevation. However, the kurtosis of the horizontal fluid velocity can have a local maximum over the downward slope on the lee side of the shoal, different from the location of the maximum of kurtosis of the surface elevation.

• Brualdi, R.A. & Dahl, Geir (2020). Alternating Sign Matrices: Extensions, König-properties, and Primary Sum-Sequences. Graphs and Combinatorics.  ISSN 0911-0119.  36, s 63- 92 . doi: https://doi.org/10.1007/s00373-019-02119-x Fulltekst i vitenarkiv.
• Aiello, Valeriano; Conti, Roberto; Rossi, Stefano & Stammeier, Nicolai (2020). The inner structure of boundary quotients of right LCM semigroups. Indiana University Mathematics Journal.  ISSN 0022-2518.  s 1- 29 Vis sammendrag

  We study distinguished subalgebras and automorphisms of boundary quo-tients arising from algebraic dynamical systems (G,P,θ). Our work includes a complete solution to the problem of extending Bogolubov automorphisms from the Cuntz algebra in 2≤p<∞ generators to the p-adic ring C*-algebra. For the case where P is abelian and C*(G) is a maximal abelian subalgebra, we establish a picture for the automorphisms of the boundary quotient that fix C*(G) pointwise. This allows us to show that they form a maximal abelian subgroup of the entire automorphism group.The picture also leads to the surprising outcome that, for integral dynamics, every automorphism that fixes one of the natural Cuntz subalgebras pointwise is necessarily a gauge automorphism. Many of the automorphisms we consider are shown to be outer.

• Bryder, Rasmus Sylvester; Ivanov, Nikolay A. & Omland, Tron (2020). C*-simplicity of HNN extensions and groups acting on trees. Annales de l'Institut Fourier.  ISSN 0373-0956.
• Shaw, Kristin & Kummer, Mario (2020). The separating semigroup of a real curve. Annales de la Faculté des Sciences de Toulouse (AFST).  ISSN 0240-2963.
• Christiansen, Snorre H & Licht, Martin Werner (2019). Poincaré-Friedrichs inequalities of complexes of discrete distributional differential forms. BIT Numerical Mathematics.  ISSN 0006-3835.  s 1- 27 . doi: 10.1007/s10543-019-00784-1
• Steinbakk, Gunnhildur Högnadóttir; Aarsnes, Lars Holterud; Aldrin, Magne Tommy; Astrup, Ole Christian; Haug, Ola; Storhaug, Gaute & Vanem, Erik (2019). Statistical Approximation to Synthetic Midship Hull Girder Stress Response. Journal of Ship Research.  ISSN 0022-4502. . doi: 10.5957/JOSR.02190008 Vis sammendrag

  Combined hydrodynamic and structural models are used to simulate structural responses on ship hulls in a seaway for design and risk assessment purposes. From a safety and inspection perspective, there is demand for continuously monitoring the ship hull conditions to estimate the structural utilization in real time. However, setting up the computer models and running the analysis are time consuming and costly, preventing such models from being used operationally. We developed a statistical model that approximates the wave bending moment output from the computer model, by linking the wave bending moment to ship design parameters and environmental information. This statistical model is computationally cheap and much faster to run than a hydrodynamic model, and may thus act as a virtual indicator sensor for structural condition monitoring. The approximated wave bending moment can also be used to compute fatigue damage for a ship as an indicator for crack risk. Although somewhat sensitive to the training dataset, a validation study reveals that the statistical model performs decently well. For fatigue rates, relative errors range from 1.4% to 60% for out-of-sample results with weighted least squares, which is deemed acceptable for an indicator model used for screening a fleet of vessels.

• Lyche, Tom & Muntingh, Agnar Georg P (2019). B-spline-like bases for C2 cubics on the Powell–Sabin 12-split. SMAI Journal of Computational Mathematics (SMAI j. comput. math.).  ISSN 2426-8399.  S5, s 129- 159 Vis sammendrag

  For spaces of constant, linear, and quadratic splines of maximal smoothness on the Powell–Sabin 12-split of a triangle, the so-called S-bases were recently introduced. These are simplex spline bases with B-spline-like properties on the 12-split of a single triangle, which are tied together across triangles in a Bézier-like manner. In this paper we give a formal definition of an S-basis in terms of certain basic properties. We proceed to investigate the existence of S-bases for the aforementioned spaces and additionally the cubic case, resulting in an exhaustive list. From their nature as simplex splines, we derive simple differentiation and recurrence formulas to other S-bases. We establish a Marsden identity that gives rise to various quasi-interpolants and domain points forming an intuitive control net, in terms of which conditions for C 0 -, C 1 -, and C 2 -smoothness are derived.

• Holter, Karl Erik; Kuchta, Miroslav & Mardal, Kent-Andre (2019). Sub-voxel Perfusion Modeling in Terms of Coupled 3d-1d Problem, In Florin Adrian Radu; Kundan Kumar; Inga Berre; Jan Martin Nordbotten & Iuliu Sorin Pop (ed.),  Numerical Mathematics and Advanced Applications ENUMATH 2017.  Springer Berlin/Heidelberg.  ISBN 978-3-319-96415-7.  Kapittel.  s 35 - 47
• Mongardi, Giovanni & Ottem, John Christian (2019). Curve classes on irreducible holomorphic symplectic varieties. Communications in Contemporary Mathematics.  ISSN 0219-1997. . doi: https://doi.org/10.1142/S0219199719500780 Fulltekst i vitenarkiv.
• Ottem, John Christian & Schreieder, Stefan (2019). On deformations of quintic and septic hypersurfaces. Journal des Mathématiques Pures et Appliquées.  ISSN 0021-7824.  135 . doi: 10.1016/j.matpur.2019.12.013 Fulltekst i vitenarkiv.
• Stoltenberg, Emil Aas & Hjort, Nils Lid (2019). Multivariate estimation of Poisson parameters. Journal of Multivariate Analysis.  ISSN 0047-259X.  175 . doi: https://doi.org/10.1016/j.jmva.2019.104545 Fulltekst i vitenarkiv.
• Claeskens, Gerda; Cunen, Celine Marie Løken & Hjort, Nils Lid (2019). Model Selection via Focused Information Criteria for Complex Data in Ecology and Evolution. Frontiers in Ecology and Evolution.  ISSN 2296-701X.  7 . doi: 10.3389/fevo.2019.00415
• Ciardo, Lorenzo (2019). A Fiedler center for graphs generalizing the characteristic set. Linear Algebra and its Applications.  ISSN 0024-3795.  584, s 197- 220 . doi: https://doi.org/10.1016/j.laa.2019.09.015 Fulltekst i vitenarkiv.
• Walløe, Lars; Hjort, Nils Lid & Thoresen, Marianne (2019). Why results from Bayesian Statistical analyses of clinical trials with a strong prior and small sample sixes may be misleading. Acta Paediatrica.  ISSN 0803-5253.  (108), s 1190- 1191 . doi: 10.111/apa.14800 Fulltekst i vitenarkiv.
• Malacarne, Sara & Neshveyev, Sergey (2019). Martin boundaries of the duals of free unitary quantum groups. Compositio Mathematica.  ISSN 0010-437X.  155(6), s 1171- 1193 . doi: https://doi.org/10.1112/S0010437X19007322 Fulltekst i vitenarkiv.
• Ayati, Anis Awal; Steiros, Konstantinos; Miller, A Mark; Duvvuri, Subrahmanyam & Hultmark, Marcus (2019). A double-multiple streamtube model for vertical axis wind turbines of arbitrary rotor loading. Wind Energy Science.  ISSN 2366-7443.  4(4), s 653- 662 . doi: 10.5194/wes-4-653-2019
• Rauter, Matthias & Köhler, Anselm (2019). Constraints on Entrainment and Deposition Models in Avalanche Simulations from High-Resolution Radar Data. Geosciences.  ISSN 2076-3263.  10(1) . doi: 10.3390/geosciences10010009 Fulltekst i vitenarkiv. Vis sammendrag

  Depth-integrated simulations of snow avalanches have become a central part of risk analysis and mitigation. However, the common practice of applying different model parameters to mimic different avalanches is unsatisfying. In here, we analyse this issue in terms of two differently sized avalanches from the full-scale avalanche test-site Vallée de la Sionne, Switzerland. We perform depth-integrated simulations with the toolkit OpenFOAM, simulating both events with the same set of model parameters. Simulation results are validated with high-resolution position data from the GEODAR radar. Rather than conducting extensive post-processing to match radar data to the output of the simulations, we generate synthetic flow signatures inside the flow model. The synthetic radar data can be directly compared with the GEODAR measurements. The comparison reveals weaknesses of the model, generally at the tail and specifically by overestimating the runout of the smaller event. Both issues are addressed by explicitly considering deposition processes in the depth-integrated model. The new deposition model significantly improves the simulation of the small avalanche, making it starve in the steep middle part of the slope. Furthermore, the deposition model enables more accurate simulations of deposition patterns and volumes and the simulation of avalanche series that are influenced by previous deposits

• Da Silva, Damiao N & Zhang, Li Chun (2019). A calibrated imputation method for secondary data analysis of survey data. Scandinavian Journal of Statistics.  ISSN 0303-6898.  s 1- 17 . doi: 10.1111/sjos.12435
• Pedersen, Christian; Niven, John; Salez, Thomas; Dalnoki-Veress, Kari & Carlson, Andreas (2019). Asymptotic regimes in elastohydrodynamic and stochastic leveling on a viscous film. Physical Review Fluids.  ISSN 2469-990X.  4(12) . doi: 10.1103/PhysRevFluids.4.124003 Fulltekst i vitenarkiv.
• Fornæss, John Erik & Wold, Erlend Fornæss (2019). An embedding of the unit ball that does not embed into a Loewner chain. Mathematische Zeitschrift.  ISSN 0025-5874.  s 1- 6 . doi: 10.1007/s00209-019-02413-7 Fulltekst i vitenarkiv.
• Enstad, Ulrik Bo Rufus (2019). The Balian-Low theorem for locally compact abelian groups and vector bundles. Journal des Mathématiques Pures et Appliquées.  ISSN 0021-7824. . doi: 10.1016/j.matpur.2019.12.005 Fulltekst i vitenarkiv.
• Salvatore, Stefania; Rand, Knut Dagestad; Grytten, Ivar; Ferkingstad, Egil; Domanska, Diana; Holden, Lars; Gheorghe, Marius; Mathelier, Anthony; Glad, Ingrid Kristine & Sandve, Geir Kjetil (2019). Beware the Jaccard: the choice of similarity measure is important and non-trivial in genomic colocalisation analysis. Briefings in Bioinformatics.  ISSN 1467-5463.  s 1- 8 . doi: 10.1093/bib/bbz083 Vis sammendrag

  The generation and systematic collection of genome-wide data is ever-increasing. This vast amount of data has enabled researchers to study relations between a variety of genomic and epigenomic features, including genetic variation, gene regulation and phenotypic traits. Such relations are typically investigated by comparatively assessing genomic co-occurrence. Technically, this corresponds to assessing the similarity of pairs of genome-wide binary vectors. A variety of similarity measures have been proposed for this problem in other fields like ecology. However, while several of these measures have been employed for assessing genomic co-occurrence, their appropriateness for the genomic setting has never been investigated. We show that the choice of similarity measure may strongly influence results and propose two alternative modelling assumptions that can be used to guide this choice. On both simulated and real genomic data, the Jaccard index is strongly altered by dataset size and should be used with caution. The Forbes coefficient (fold change) and tetrachoric correlation are less influenced by dataset size, but one should be aware of increased variance for small datasets. All results on simulated and real data can be inspected and reproduced at https://hyperbrowser.uio.no/sim-measure.

• Kohn, Kathlén & Ranestad, Kristian (2019). Projective Geometry of Wachspress Coordinates. Foundations of Computational Mathematics.  ISSN 1615-3375. . doi: 10.1007/s10208-019-09441-z
• Normann, Dag & Sanders, Sam (2019). Computability Theory, Nonstandard Analysis, and Their Connections. Journal of Symbolic Logic (JSL).  ISSN 0022-4812.  84(4), s 1422- 1465 . doi: 10.1017/jsl.2019.69 Fulltekst i vitenarkiv.
• Floater, Michael S. & Patrizi, Francesco (2019). Transfinite mean value interpolation over polygons. Numerical Algorithms.  ISSN 1017-1398.  s 1- 9 . doi: 10.1007/s11075-019-00849-w Fulltekst i vitenarkiv. Vis sammendrag

  Mean value interpolation is a method for fitting a smooth function to piecewise-linear data prescribed on the boundary of a polygon of arbitrary shape, and has applications in computer graphics and curve and surface modelling. The method generalizes to transfinite interpolation, i.e., to any continuous data on the boundary but a mathematical proof that interpolation always holds has so far been missing. The purpose of this note is to complete this gap in the theory.

• Carr, Magda; Sutherland, Peter; Haase, Andrea; Evers, Karl-Ulrich; Fer, Ilker; Jensen, Atle; Kalisch, Henrik; Berntsen, Jarle; Părău, Emilian I.; Thiem, Øyvind & Davies, Peter A. (2019). Laboratory experiments on internal solitary waves in ice-covered waters. Geophysical Research Letters.  ISSN 0094-8276.  46(21), s 12230- 12238 . doi: 10.1029/2019GL084710 Fulltekst i vitenarkiv.
• Arosio, Leandro & Wold, Erlend Fornæss (2019). Totally real embeddings with prescribed polynomial hulls.. Indiana University Mathematics Journal.  ISSN 0022-2518.  68(2) . doi: 10.1512/iumj.2019.68.7603
• Crisan, Dan & Ortiz-Latorre, Salvador (2019). A high order time discretization of the solution of the non-linear filtering problem. Stochastics and Partial Differential Equations: Analysis and Computations.  ISSN 2194-0401.  s 1- 68 . doi: 10.1007/s40072-019-00157-3
• Kaliszewski, S.; Omland, Tron & Quigg, John (2019). The Pedersen rigidity problem. Revista Colombiana de Matemáticas.  ISSN 0034-7426.  53(E), s 237- 244 . doi: 10.15446/recolma.v53nsupl.84095
• Ramos-Peon, Alexandre & Ugolini, Riccardo (2019). Parametric jet interpolation for Stein manifolds with the density property. International Journal of Mathematics.  ISSN 0129-167X.  30(8) . doi: 10.1142/S0129167X19500460
• Draouil, Olfa & Øksendal, Bernt (2019). A white noise approach to optimal insider control of systems with delay. Journal of Mathematical Analysis and Applications.  ISSN 0022-247X.  476(1), s 101- 119 . doi: https://doi.org/10.1016/j.jmaa.2019.02.065 Fulltekst i vitenarkiv.
• Belus, Vincent; Rabault, Jean; Viquerat, Jonathan; Che, Zhizhao; Hachem, Elie & Reglade, Ulysse Antoine (2019). Exploiting locality and translational invariance to design effective deep reinforcement learning control of the 1-dimensional unstable falling liquid film. AIP Advances.  ISSN 2158-3226.  9(12) . doi: 10.1063/1.5132378 Fulltekst i vitenarkiv.
• Hultgren, Jakob (2019). Coupled Kahler-Ricci solitons on Toric Fano Manifolds. Analysis & PDE.  ISSN 2157-5045.  12(8), s 2067- 2094 . doi: 10.2140/apde.2019.12.2067 Fulltekst i vitenarkiv.
• Kolderup, Håkon Andreas (2019). Homotopy invariance of Nisnevich sheaves with Milnor-Witt transfers. Documenta Mathematica.  ISSN 1431-0635.  24, s 2339- 2379 . doi: 10.25537/dm.2019v24.2339-2379 Fulltekst i vitenarkiv.
• Helle, Gard Olav & Rognes, John (2019). Boardman's Whole-Plane Obstruction Group for Cartan-Eilenberg Systems. Documenta Mathematica.  ISSN 1431-0635.  24, s 1855- 1878 . doi: 10.25537/dm.2019v24.1855-1878 Fulltekst i vitenarkiv.
• Ross, Emma; Astrup, Ole Christian; Bitner-Gregersen, Elzbieta; Bunn, Nigel; Feld, Graham; Gouldby, Ben; Huseby, Arne; Liu, Ye; Randell, David; Vanem, Erik & Jonathan, Philip (2019). On Environmental Contours for Marine and Coastal Design, In . ASME (ed.),  ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. Volume 7B: Ocean Engineering.  The American Society of Mechanical Engineers (ASME).  ISBN 978-0-7918-5885-1.  V07BT06A012.
• Magnusson, Anne Karin; Trulsen, Karsten; Bitner-Gregersen, Elzbieta M.; Aarnes, Ole Johan & Malila, Mika Petteri (2019). “Three Sisters” Measured as a Triple Rogue Wave Group, In . ASME (ed.),  ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. Volume 3: Structures, Safety, and Reliability.  The American Society of Mechanical Engineers (ASME).  ISBN 978-0-7918-5878-3.  KAPITTEL. Vis sammendrag

  On November 30, 2018, our attention was caught when analyzing wave profile time series measured by a platform mounted wave sensor (a SAAB REX radar) at Ekofisk, central North Sea. The 20-minute time series had not only one, but three consecutive waves with individual heights that all were more than twice the significant wave height, the two last of them being almost equally high with a factor 2.35 to the significant wave height of 4m (from 4σ(η), over 20 minutes). Counting three rogue waves in one sequence seems to be very rare. In this study we analyze how the shape is evolving in space and time using linear and non-linear propagation methods developed by Mark Donelan [1,2] and Karsten Trulsen [3,4]. Weather conditions and characteristics of the sea state with the ‘Three Sisters’ (named the “Justine Three Sisters”) are presented. It is found that the Three Sisters occurred in a crossing sea condition, with wind sea and swell coming from directions 60 degrees apart, with about same frequency, but very different energy.

• Coclite, Giuseppe Maria; Chatterjee, Neelabja & Risebro, Nils Henrik (2019). Well-posedness of the Initial Value Problem for the Ostrovsky–Hunter Equation with Spatially Dependent Flux. Milan Journal of Mathematics.  ISSN 1424-9286.  87(2), s 283- 301 . doi: 10.1007/s00032-019-00302-6 Fulltekst i vitenarkiv.
• Holden, Helge & Risebro, Nils Henrik (2019). Models for dense multilane vehicular traffic. SIAM Journal on Mathematical Analysis.  ISSN 0036-1410.  51(5), s 3694- 3713 . doi: 10.1137/19M124318X Fulltekst i vitenarkiv.
• Vollestad, Petter; Ayati, Anis Awal & Jensen, Atle (2019). Experimental investigation of intermittent airflow separation and microscale wave breaking in wavy two-phase pipe flow. Journal of Fluid Mechanics.  ISSN 0022-1120.  878, s 769- 819 . doi: 10.1017/jfm.2019.660 Fulltekst i vitenarkiv.
• Risebro, Nils Henrik & Ruf, Adrian Montgomery (2019). Numerical investigations into a model of partially incompressible two-phase flow in pipes. SeMA Journal - Boletin de la Sociedad Española de Matemática Aplicada.  ISSN 2254-3902.  s 1- 17 . doi: 10.1007/s40324-019-00207-9 Fulltekst i vitenarkiv.
• Karlsson, Cecilia (2019). A note on coherent orientations for exact Lagrangian cobordisms. Quantum Topology.  ISSN 1663-487X. . doi: 10.4171/QT/132 Fulltekst i vitenarkiv.
• De Bin, Riccardo; Boulesteix, Anne-Laure; Benner, Alex; Becker, Natalia & Sauerbrei, Willi (2019). Combining clinical and molecular data in regression prediction models: insights from a simulation study. Briefings in Bioinformatics.  ISSN 1467-5463. . doi: 10.1093/bib/bbz136
• Coclite, Giuseppe Maria & Risebro, Nils Henrik (2019). A difference method for the McKean–Vlasov equation. Zeitschrift für Angewandte Mathematik und Physik.  ISSN 0044-2275.  70(5), s 1- 24 . doi: 10.1007/s00033-019-1196-x Fulltekst i vitenarkiv.
• Halnes, Geir; Pettersen, Klas Henning; Øyehaug, Leiv; Rognes, Marie Elisabeth & Einevoll, Gaute (2019). Astrocytic Ion Dynamics: Implications for Potassium Buffering and Liquid Flow, In Hugues Berry & Maurizio De Pittà (ed.),  Computational Glioscience.  Springer Nature.  ISBN 978-3-030-00817-8.  Chapter.  s 363 - 391
• Hausmann, Jean-Claude & Jahren, Bjørn (2019). A simplification problem in manifold topology. L'Enseignement mathématique (LEM).  ISSN 0013-8584.  64(1/2), s 207- 248 . doi: 10.4171/LEM/64-1/2-8
• Cifuentes, Diego; Harris, Corey & Sturmfels, Bernd (2019). The geometry of SDP-exactness in quadratic optimization. Mathematical programming.  ISSN 0025-5610.  s 1- 30 . doi: 10.1007/s10107-019-01399-8
• Vanem, Erik & Brandsæter, Andreas (2019). Unsupervised anomaly detection based on clustering methods and sensor data on a marine diesel engine. Journal of Marine Engineering & Technology.  ISSN 2046-4177. . doi: 10.1080/20464177.2019.1633223 Fulltekst i vitenarkiv.
• Bielavsky, Pierre; Gayral, Victor; Neshveyev, Sergey & Tuset, Lars (2019). Addendum. On deformations of C*-algebras by actions of Kahlerian Lie groups. International Journal of Mathematics.  ISSN 0129-167X.  30(11) . doi: 10.1142/S0129167X19920022
• Mohammadi, Fatemeh & Shaw, Kristin (2019). Toric degenerations of Grassmannians from matching fields. Algebraic combinatorics.  ISSN 2589-5486.  2(6), s 1109- 1124 . doi: https://doi.org/10.5802/alco.77 Fulltekst i vitenarkiv.
• Galimberti, Luca & Karlsen, Kenneth Hvistendahl (2019). Well-posedness theory for stochastically forced conservation laws on Riemannian manifolds. Journal of Hyperbolic Differential Equations.  ISSN 0219-8916.  16(3), s 519- 593 . doi: 10.1142/S0219891619500188
• Lyche, Tom; Manni, Carla & Speleers, Hendrik (2019). Tchebycheffian B-Splines Revisited: An Introductory Exposition, In Carlotta Giannelli & Hendrik Speleers (ed.),  Advanced Methods for Geometric Modeling and Numerical Simulation.  Springer Nature.  ISBN 978-3-030-27330-9.  kapittel.  s 179 - 216 Fulltekst i vitenarkiv.
• Eide, Per Kristian; Valnes, Lars Magnus; Pripp, Are Hugo; Mardal, Kent-Andre & Ringstad, Geir (2019). Delayed clearance of cerebrospinal fluid tracer from choroid plexus in idiopathic normal pressure hydrocephalus. Journal of Cerebral Blood Flow and Metabolism.  ISSN 0271-678X.  s 1- 10 . doi: 10.1177/0271678X19874790
• Rennemo, Jørgen Vold & Segal, Ed (2019). Hori-mological projective duality. Duke mathematical journal.  ISSN 0012-7094.  168(11), s 2127- 2205 . doi: 10.1215/00127094-2019-0014 Fulltekst i vitenarkiv.
• Bounoua, Wahiba; Benkara, Amina B.; Kouadri, Abdelmalek & Bakdi, Azzeddine (2019). Online Monitoring Scheme Using PCA through Kullback-Leibler Divergence Analysis Technique for Fault Detection. Transactions of the Institute of Measurement and Control.  ISSN 0142-3312. . doi: 10.1177/0142331219888370 Fulltekst i vitenarkiv.
• Baadji, Bousaadia; Bentarzi, Hamid & Bakdi, Azzeddine (2019). Comprehensive learning bat algorithm for optimal coordinated tuning of power system stabilizers and static VAR compensator in power systems. Engineering optimization (Print).  ISSN 0305-215X.  s 1- 19 . doi: 10.1080/0305215X.2019.1677635 Fulltekst i vitenarkiv.
• Bakdi, Azzeddine; Bounoua, Wahiba; Mekhilef, Saad & Halabi, Laith M. (2019). Nonparametric Kullback-divergence-PCA for intelligent mismatchdetection and power quality monitoring in grid-connected rooftop PV. Energy.  ISSN 0360-5442.  189 . doi: 10.1016/j.energy.2019.116366 Fulltekst i vitenarkiv.
• ABDELMALEK, Samir; Rezazi, Sarah; Bakdi, Azzeddine & Bettayeb, Maamar (2019). VOLTAGE DIPS EFFECTS DETECTION AND COMPENSATION FOR DOUBLY-FED INDUCTION GENERATOR BASED WIND ENERGY CONVERSION SYSTEM. Revue Roumaine des Sciences Techniques - Serie Electrotechnique et Energetique.  ISSN 0035-4066.  64(3), s 199- 204
• Tveten, Martin (2019). Which principal components are most sensitive in the change detection problem?. Stat.  ISSN 2049-1573.  8(1) . doi: 10.1002/sta4.252 Fulltekst i vitenarkiv.
• Moss, Jonas & Tveten, Martin (2019). kdensity: An R package for kernel density estimation with parametric starts and asymmetric kernels. Journal of Open Source Software (JOSS).  ISSN 2475-9066. . doi: 10.21105/joss.01566 Fulltekst i vitenarkiv.
• Dubouloz, Adrien; Pauli, Sabrina & Østvær, Paul Arne (2019). A1-contractibility of affine modifications. International Journal of Mathematics.  ISSN 0129-167X. . doi: 10.1142/S0129167X19500691
• Ketcheson, David I.; Mortensen, Mikael; Parsani, Matteo & Schilling, Nathanael (2019). More efficient time integration for Fourier pseudospectral DNS of incompressible turbulence. International Journal for Numerical Methods in Fluids.  ISSN 0271-2091. . doi: 10.1002/fld.4773 Fulltekst i vitenarkiv.
• Biagini, Francesca & Zhang, Yinglin (2019). Reduced-form framework under model uncertainty. The Annals of Applied Probability.  ISSN 1050-5164.  29(4), s 2481- 2522 . doi: 10.1214/18-AAP1458 Fulltekst i vitenarkiv.
• Agrell, Christian (2019). Gaussian processes with linear operator inequality constraints. Journal of machine learning research.  ISSN 1532-4435.  20(135), s 1- 36 Fulltekst i vitenarkiv.
• Biagini, Francesca; Mazzon, Andrea & Meyer-Brandis, Thilo (2019). Financial asset bubbles in banking networks. SIAM Journal on Financial Mathematics.  ISSN 1945-497X.  10(2), s 430- 465 . doi: 10.1137/18M1193189 Fulltekst i vitenarkiv.

Se alle arbeider i Cristin

• Øksendal, Bernt (2020). A financial market with singular drift and no arbitrage.
• Øksendal, Bernt (2020). A financial market with singular drift and no arbitrage.
• Øksendal, Bernt (2019). Introduction to White Noise Theory and Applications.
• Øksendal, Bernt (2019). Introduction to Stochastic Control Theory for Jump Diffusions.
• Øksendal, Bernt (2019). Introduction to Stochastic Control of Jump Diffusions, with Applications to Mathematical Finance.
• Øksendal, Bernt (2019). A financial market with a local time drift term and delay.
• Øksendal, Bernt (2019). Introduction to White Noise Theory and Applications.
• Øksendal, Bernt (2019). Introduction to Stochastic Control Theory for Jump Diffusions.
• Øksendal, Bernt (2019). A financial market with a local time drift term and delay.
• Øksendal, Bernt (2019). Introduction to Stochastic Control of Jump Diffusions, with Applications to Mathematical Finance.
• Tvete, Ingunn Fride; Natvig, Bent; Gåsemyr, Jørund Inge; Klemp, Marianne & Binde, Caroline Ditlev (2019). Sammenligning av medikamenter for behandling av Parkinson pasienter. NR-notat. SAMBA/01/19.
• Boug, Pål; Cappelen, Ådne; Jansen, Eilev S & Swensen, Anders Rygh (2019). The consumption Euler equation or the Keynesian consumption function?. Discussion papers.  ISSN 1892-753X.  (No. 904) Vis sammendrag

  We formulate a general cointegrated vector autoregressive (CVAR) model that nests both a class of consumption Euler equations and various Keynesian type consumption functions. Using likelihoodbased methods and Norwegian data, we find support for cointegration between consumption, income and wealth once a structural break around the financial crisis is allowed for. That consumption cointegrates with both income and wealth and not only with income points to the empirical irrelevance of an Euler equation. Moreover, we find that consumption equilibrium corrects to changes in income and wealth and not that income equilibrium corrects to changes in consumption, which would be the case if an Euler equation is true. We also find that most of the parameters stemming from the class of Euler equations are not corroborated by the data when considering conditional expectations of future consumption and income in CVAR models. Only habit formation seems important in explaining the Norwegian consumer behaviour. Our preferred model is a dynamic Keynesian type consumption function with a first year marginal propensity to consume out of income close to 25 per cent.

• Natvig, Bent (2019). Is reliability a new science?. Applied Stochastic Models in Business and Industry.  ISSN 1524-1904.  35(2) . doi: 10.1002/asmb.2424
• Lindstrøm, Tom Louis (2019). Overgangen fra videregående skole til universitet og høyskole.
• Lindstrøm, Tom Louis (2019). Refleksjoner over refleksjon.
• Lindstrøm, Tom Louis (2019). Veien mot nye læreplaner.
• Lindstrøm, Tom Louis (2019). Komplekse tall.
• Dahl, Geir (2019). Majorization - some recent developments in matrix theory.

Se alle arbeider i Cristin