• Factorisation patterns of division polynomials 

      Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2004-05)
      The choice of an elliptic curve for the implementa- tion of an elliptic curve cryptosystem requires count- ing the number of points on such a curve over a fi- nite field. An improvement of Schoof’s algorithm for counting the number of rational points on an ellip- tic curve defined over a finite field takes advantage of some factor of the division polynomials. In this paper, we study the ...
    • Families of Gröbner Degenerations, Grassmannians and Universal Cluster Algebras 

      Bossinger, Lara; Mohammadi, Fatemeh; Nájera Chávez, Alfredo (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-10)
      Let V be the weighted projective variety defined by a weighted homogeneous ideal J and C a maximal cone in the Gröbner fan of J with m rays. We construct a flat family over A<sup>m</sup> that assembles the Gröbner degenerations of V associated with all faces of C. This is a multi-parameter generalization of the classical one-parameter Gröbner degeneration associated to a weight. We explain how our ...
    • Feedback Differential Invariants 

      Lychagin, Valentin V. (Journal article; Tidsskriftartikkel, 2008-12-07)
      The problem of feedback equivalence for control systems is considered. An algebra of differential invariants and criteria for the feedback equivalence for regular control systems are found.
    • Feedback Equivalence of 1-dimensional Control Systems of the 1-st Order 

      Lychagin, Valentin V. (Working paper; Arbeidsnotat, 2008-12-09)
      The problem of local feedback equivalence for 1-dimensional control systems of the 1-st order is considered. The algebra of differential invariants and criteria for the feedback equivalence for regular control systems are found.
    • Finite dimensional dynamics for nonlinear filtration equation 

      Akhmetzyanov, Atlas V.; Kushner, Alexei G.; Lychagin, Valentin (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-01)
      We construct new finite dimensional submanifolds in the solution space of nonlinear differential filtration equations and describe the corresponding evolutionary dynamics. This method is implemented in a computer program of symbolic computations Maple.
    • Finite Larmor radius influence on MHD solitary waves 

      Mjølhus, Einar (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)
    • A finite volume flux coordinate independent approach 

      Wiesenberger, Matthias; Held, Markus (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-03)
      We present a novel family of schemes as the merging between a one-dimensional advection scheme with the flux coordinate independent approach. The scheme can be used to discretize the field-aligned NavierStokes equations in three dimensions. Our approach consists of three major steps: (i) the formulation of the one-dimensional scheme in a locally field-aligned coordinate system, (ii) a numerical ...
    • Finite-sample properties of estimators for first and second order autoregressive processes 

      Sørbye, Sigrunn Holbek; Nicolau, Pedro Guilherme; Rue, Håvard (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-05)
      The class of autoregressive (AR) processes is extensively used to model temporal dependence in observed time series. Such models are easily available and routinely fitted using freely available statistical software like R. A potential problem is that commonly applied estimators for the coefficients of AR processes are severely biased when the time series are short. This paper studies the ...
    • Flags of almost affine codes and the two-party wire-tap channel of type II 

      Johnsen, Trygve; Verdure, Hugues (Journal article; Tidsskriftartikkel; Manuskript; Peer reviewed; Preprint, 2017-11-15)
      We describe a two-party wire-tap channel of type II in the framework of almost affine codes. Its cryptological performance is related to some relative profiles of a pair of almost affine codes. These profiles are analogues to relative generalized Hamming weights in the linear case.
    • Food recommendation using machine learning for physical activities in patients with type 1 diabetes 

      Ngo, Phuong; Tayefi, Maryam; Nordsletta, Anne Torill; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2019)
      Physical activities have a significant impact on blood glucose homeostasis of patients with type 1 diabetes. Regular physical exercise provides many proven health benefits and is recommended as part of a healthy lifestyle. However, one of the main side effects of physical activities is hypoglycemia (low blood glucose). Fear of hypoglycemia generally leads to the patients not participating in ...
    • Fractional Gaussian noise: Prior specification and model comparison 

      Sørbye, Sigrunn Holbek; Rue, Håvard (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-07)
      Fractional Gaussian noise (fGn) is a stationary stochastic process used to model anti-persistent or persistent dependency structures in observed time series. Properties of the autocovariance function of fGn are characterised by the Hurst exponent (<i>H)</i>, which in Bayesian contexts typically has been assigned a uniform prior on the unit interval. This paper argues why a uniform prior is ...
    • Frailty in Survival Analysis of Widowhood Mortality 

      Ytterstad, Elinor (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-02)
      Heterogeneity between individuals has attracted attention in the literature of survival analysis for several decades. Widowed individuals also differ; some are more frail than others and thereby have a higher risk of dying. The traditional hazard rate in a survival model is a measure of population risk and does not provide direct information on the unobservable individual risk. A frailty model is ...
    • A frame based approach to computing symmetries with non-trivial isotropy groups 

      McNutt, David Duncan; Coley, A.A.; Van Den Hoogen, Den (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-24)
      A frame approach to determining the most general solution admitting a desired symmetry group has previously been examined in Riemannian and teleparallel geometries with some success. In teleparallel geometries, one must determine the general form of the frame and spin connection to generate a general solution admitting the desired symmetry group. Current approaches often rely on the use of the ...
    • G(3)-supergeometry and a supersymmetric extension of the Hilbert–Cartan equation 

      Kruglikov, Boris; Santi, Andrea; The, Dennis (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-23)
      We realize the simple Lie superalgebra <i>G</i>(3) as supersymmetry of various geometric structures, most importantly super-versions of the Hilbert–Cartan equation (SHC) and Cartan's involutive PDE system that exhibit <i>G</i>(2) symmetry. We provide the symmetries explicitly and compute, via the first Spencer cohomology groups, the Tanaka–Weisfeiler prolongation of the negatively graded Lie ...
    • The gap phenomenon in parabolic geometries 

      Kruglikov, Boris; The, Dennis (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-09-14)
      The infinitesimal symmetry algebra of any Cartan geometry has maximum dimension realized by the flat model, but often this dimension drops significantly when considering non-flat geometries, so a gap phenomenon arises. For general (regular, normal) parabolic geometries of type (G,P), we use Tanaka theory to derive a universal upper bound on the submaximal symmetry dimension. We use Kostant’s version ...
    • A generalization of Kung’s theorem 

      Johnsen, Trygve; Shiromoto, Keisuke; Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-10-01)
      We give a generalization of Kung’s theorem on critical exponents of linear codes over a finite field, in terms of sums of extended weight polynomials of linear codes. For all i=k+1,…,ni=k+1,…,n, we give an upper bound on the smallest integer m such that there exist m codewords whose union of supports has cardinality at least i.
    • A generalization of weight polynomials to matroids 

      Johnsen, Trygve; Roksvold, Jan Nyquist; Verdure, Hugues (Tidsskriftartikkel; Journal article; Peer reviewed, 2015-11-11)
      Generalizing polynomials previously studied in the context of linear codes, we define weight polynomials and an enumerator for a matroid M. Our main result is that these polynomials are determined by Betti numbers associated with N0-graded minimal free resolutions of the Stanley-Reisner ideals of M and so-called elongations of M. Generalizing Greene’s the- orem from coding theory, we show that ...
    • Generalized eigenvalue methods for Gaussian quadrature rules 

      Blekherman, Grigoriy; Kummer, Mario; Riener, Cordian; Schweighofer, Markus; Vinzant, Cynthia (Journal article; Tidsskriftartikkel; Peer reviewed, 2020)
      A quadrature rule of a measure <i>µ</i> on the real line represents a conic combination of finitely many evaluations at points, called nodes, that agrees with integration against <i>µ</i> for all polynomials up to some fixed degree. In this paper, we present a bivariate polynomial whose roots parametrize the nodes of minimal quadrature rules for measures on the real line. We give two symmetric ...
    • Generalized Hamming Weights for Almost Affine Codes 

      Johnsen, Trygve; Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-17)
      We define generalized Hamming weights for almost affine codes. We show that this definition is natural since we can extend some well known properties of t he generalized Hamming weights for linear codes, to almost affine codes. In addition we discus s duality of almost affine codes, and of the smaller class of multilinear codes.
    • Generalized Teleparallel de Sitter geometries 

      Coley, Alan; Landry, Alexandre; van den Hoogen, Robert; McNutt, David Duncan (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-30)
      Theories of gravity based on teleparallel geometries are characterized by the torsion, which is a function of the coframe, derivatives of the coframe, and a zero curvature and metric compatible spin-connection. The appropriate notion of a symmetry in a teleparallel geometry is that of an affine symmetry. Due to the importance of the de Sitter geometry and Einstein spaces within General Relativity, ...