• Data-Driven Robust Control Using Reinforcement Learning 

      Ngo, Phuong; Tejedor Hernandez, Miguel Angel; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-21)
      This paper proposes a robust control design method using reinforcement learning for controlling partially-unknown dynamical systems under uncertain conditions. The method extends the optimal reinforcement learning algorithm with a new learning technique based on the robust control theory. By learning from the data, the algorithm proposes actions that guarantee the stability of the closed-loop system ...
    • De-identifying Swedish EHR text using public resources in the general domain 

      Chomutare, Taridzo; Yigzaw, Kassaye Yitbarek; Budrionis, Andrius; Makhlysheva, Alexandra; Godtliebsen, Fred; Dalianis, Hercules (Journal article; Tidsskriftartikkel; Peer reviewed, 2020)
      Sensitive data is normally required to develop rule-based or train machine learning-based models for de-identifying electronic health record (EHR) clinical notes; and this presents important problems for patient privacy. In this study, we add non-sensitive public datasets to EHR training data; (i) scientific medical text and (ii) Wikipedia word vectors. The data, all in Swedish, is used to train a ...
    • Decomposable (5, 6)-solutions in eleven-dimensional supergravity 

      Chi, Hanci; Chrysikos, Ioannis; Schneider, Eivind (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-08)
      We present decomposable (5, 6)-solutions M<sup>1,4</sup>×M<sup>6</sup> in eleven-dimensional supergravity by solving the bosonic supergravity equations for a variety of non-trivial flux forms. Many of the bosonic backgrounds presented here are induced by various types of null flux forms on products of certain totally Ricci-isotropic Lorentzian Walker manifolds and Ricci-flat Riemannian manifolds. ...
    • Deformation of big pseudoholomorphic disks and application to the Hanh pseudonorm 

      Kruglikov, Boris (Journal article; Tidsskriftartikkel; Peer reviewed, 2003-04-14)
      We simplify proof of the theorem that close to any pseudoholomorphic disk there passes a pseudoholomorphic disk of arbitrary close size with any pre-described sufficiently close direction. We apply these results to the Kobayashi and Hanh pseudodistances. It is shown they coincide in dimensions higher than four. The result is new even in the complex case.
    • DeltaProt : a software toolbox for comparative genomics 

      Thorvaldsen, Steinar; Flå, Tor; Willassen, Nils P (Journal article; Tidsskriftartikkel; Peer reviewed, 2010)
    • Density ridge manifold traversal 

      Myhre, Jonas Nordhaug; Kampffmeyer, Michael C.; Jenssen, Robert (Chapter; Bokkapittel, 2017-06-19)
      The density ridge framework for estimating principal curves and surfaces has in a number of recent works been shown to capture manifold structure in data in an intuitive and effective manner. However, to date there exists no efficient way to traverse these manifolds as defined by density ridges. This is unfortunate, as manifold traversal is an important problem for example for shape estimation in ...
    • Differential invariants of curves in G2 flag varieties 

      Kruglikov, Boris; Llabrés, Andreu (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-10)
      We compute the algebra of differential invariants of unparametrized curves in the homogeneous G<sub>2</sub> flag varieties, namely in G<sub>2</sub>/P. This gives a solution to the equivalence problem for such curves. We consider the cases of integral and generic curves and relate the equivalence problems for all three choices of the parabolic subgroup P.
    • Differential invariants of Einstein-Weyl structures in 3D 

      Kruglikov, Boris; Schneider, Eivind (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-22)
      Einstein–Weyl structures on a three-dimensional manifold <i>M</i> are given by a system <i>E</i> of PDEs on sections of a bundle over <i>M</i>. This system is invariant under the Lie pseudogroup <i>G</i> of local diffeomorphisms on <i>M</i>. Two Einstein–Weyl structures are locally equivalent if there exists a local diffeomorphism taking one to the other. Our goal is to describe the quotient equation ...
    • Differential invariants of Kundt spacetimes 

      Kruglikov, Boris; Schneider, Eivind (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-07)
      We find generators for the algebra of rational differential invariants for general and degenerate Kundt spacetimes and relate this to other approaches to the equivalence problem for Lorentzian metrics. Special attention is given to dimensions three and four.
    • Differential invariants of Kundt waves 

      Kruglikov, Boris; McNutt, David Duncan; Schneider, Eivind (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-17)
      Kundt waves belong to the class of spacetimes which are not distinguished by their scalar curvature invariants. We address the equivalence problem for the metrics in this class via scalar differential invariants with respect to the equivalence pseudo-group of the problem. We compute and finitely represent the algebra of those on the generic stratum and also specify the behavior for vacuum Kundt ...
    • Differential Invariants of Linear Symplectic Actions 

      Jensen, Jørn Olav; Kruglikov, Boris (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)
      We consider the equivalence problem for symplectic and conformal symplectic group actions on submanifolds and functions of symplectic and contact linear spaces. This is solved by computing differential invariants via the Lie-Tresse theorem.
    • Differential invariants of self-dual conformal structures 

      Kruglikov, Boris; Schneider, Eivind (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-06-17)
      We compute the quotient of the self-duality equation for conformal metrics by the action of the diffeomorphism group. We also determine Hilbert polynomial, counting the number of independent scalar differential invariants depending on the jet-order, and the corresponding Poincaré function. We describe the field of rational differential invariants separating generic orbits of the diffeomorphism ...
    • Differential invariants of the motion group actions 

      Kruglikov, Boris; Lychagin, Valentin V. (Working paper; Arbeidsnotat, 2007-12-20)
      Differential invariants of a (pseudo)group action can vary when restricted to invariant submanifolds (differential equations). The algebra is still governed by the Lie-Tresse theorem, but may change a lot. We describe in details the case of the motion group O(n) ⋉ R<sup>n</sup> acting on the full (unconstraint) jet-space as well as on some invariant equations.
    • Dimension of the solutions space of PDEs 

      Kruglikov, Boris; Lychagin, Valentin V. (Conference object; Konferansebidrag, 2006-10-26)
      We discuss the dimensional characterization of the solutions space of a formally integrable system of partial differential equations and provide certain formulas for calculations of these dimensional quantities.
    • Dispersionless integrable hierarchies and GL(2,R) geometry 

      Ferapontov, Evgeny V; Kruglikov, Boris (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10-08)
      Paraconformal or GL(2, ℝ) geometry on an <i>n</i>-dimensional manifold <i>M</i> is defined by a field of rational normal curves of degree <i>n</i> – 1 in the projectivised cotangent bundle <i>ℙT*M</i>. Such geometry is known to arise on solution spaces of ODEs with vanishing Wünschmann (Doubrov–Wilczynski) invariants. In this paper we discuss yet another natural source of <i>GL</i>(2, ℝ) structures, ...
    • Does proximity of women to facilities with better choice of contraceptives affect their contraceptive utilization in rural Ethiopia? 

      Shiferaw, Solomon; Spigt, Mark; Seme, Assefa; Amogne, Ayanaw; Skrøvseth, Stein Olav; Desta, Selamawit; Radloff, Scott; Tsui, Amy; Dinant, Geert-Jan (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-13)
      Background:<br>There is limited evidence of the linkage between contraceptive use, the range of methods available and level of contraceptive stocks at health facilities and distance to facility in developing countries. The present analysis aims at examining the influence of contraceptive method availability and distance to the nearby facilities on modern contraceptive utilization among married women ...
    • Double Schubert polynomials do have saturated Newton polytopes 

      Castillo, Federico; Cid-Ruiz, Yairon; Mohammadi, Fatemeh; Montaño, Jonathan (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-03)
      We prove that double Schubert polynomials have the saturated Newton polytope property. This settles a conjecture by Monical, Tokcan and Yong. Our ideas are motivated by the theory of multidegrees. We introduce a notion of standardization of ideals that enables us to study nonstandard multigradings. This allows us to show that the support of the multidegree polynomial of each Cohen–Macaulay prime ...
    • Dynamic self-organisation of haematopoiesis and (a)symmetric cell division 

      Måløy, Marthe; Måløy, Frode; Jakobsen, Per; Brandsdal, Bjørn Olav (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-05)
      A model of haematopoiesis that links self-organisation with symmetric and asymmetric cell division is presented in this paper. It is assumed that all cell divisions are completely random events, and that the daughter cells resulting from symmetric and asymmetric stem cell divisions are, in general, phenotypically identical, and still, the haematopoietic system has the flexibility to self-renew, ...
    • Dynamics and entropy in the Zhang model of Self-Organized Criticality 

      Kruglikov, Boris; Rypdal, Martin (Working paper; Arbeidsnotat, 2005-09-12)
      We give a detailed study of dynamical properties of the Zhang model, including evaluation of topological entropy and estimates for the Lyapunov exponents and the dimension of the attractor. In the thermodynamic limit the entropy goes to zero and the Lyapunov spectrum collapses.1
    • Dørene lukkes for klimamålene 

      Rypdal, Kristoffer (Chronicle; Kronikk, 2015-11-10)