• Codes, matroids and derived matroids 

      Knutsen, Teodor Dahl (Mastergradsoppgave; Master thesis, 2023-05-15)
      This thesis first introduces some theory on coding theory and matroids, and properties that are shared between these, and then we will investigate derived matroids. In 1979 Longyear made a construction of derived matroids for binary matroids, which illuminates "dependencies among dependencies". The construction was later generalized to representable matroids by Oxley and Wang, where the derived ...
    • A complex contour based perfectly matched layer applied to a pattern generating model equation. 

      Jenssen, Amund (Master thesis; Mastergradsoppgave, 2017-02-17)
      The observable universe consists of several non equilibrium systems that generate spatiotemporal behaviour in the form of various patterns. As the elementary laws of physics and chemistry are unable to explain the pattern forming behaviour of such systems, scientists have turned to desktop experiments and model equations to gain further insight. The model equations that generate numerical solutions ...
    • Deforming the vacuum. On the physical origin and numerical calculation of the Casimir effect. 

      Mikalsen, Karl Øyvind (Master thesis; Mastergradsoppgave, 2014-05-14)
      A new method for calculating the Casimir force between compact objects was introduced in May 2012 by Per Jakobsen and Isak Kilen. In this method a regularization procedure is used to reduce the pressure to the solution of an integral equation defined on the boundaries of the objects. In this thesis the method is further developed by extending from a 2D to a 3D massless scalar field, subject to ...
    • Differential invariants of the 2D conformal Lie algebra action 

      Høyem, Marte Rørvik (Master thesis; Mastergradsoppgave, 2008-02-15)
      In this thises we consider the Lie algebra that corresponds to the Lie pseudogroup of all conformal transformations on the plane. This conformal Lie algebra is canonically represented as a Lie algebra of vector fields on R^2. We will find all possible representations of vector fields in R^3=J^0R^2 which projects to the canonical representation and find the algebra of scalar differential invariants ...
    • Differential Invariants of Symplectic and Contact Lie Algebra Actions 

      Jensen, Jørn Olav (Master thesis; Mastergradsoppgave, 2020-06-23)
      In this thesis we consider the equivalence problem for symplectic and conformal symplectic group actions on submanifolds and functions. We solve the equivalence problem for general submanifolds by means of computing differential invariants and describing all the invariants of the associated group action by appealing to the Lie-Tresse theorem.
    • Distributing a private key generator in Ad hoc Networks 

      Stenberg, Eystein Måløy (Master thesis; Mastergradsoppgave, 2009-05-15)
      A Mobile Ad hoc Network (MANET) is a wireless network that does not rely on a fixed infrastructure. These characteristics make algorithms that route network traffic particularly vulnerable to attack. Mechanisms used to protect against such attacks often depend on cryptographic keys. Since the nodes in a MANET have limited resources, designing methods for cryptographic key management is ...
    • Effects of feedbacks for an energy balance model on a circle 

      Brynjulfsen, Synne (Mastergradsoppgave; Master thesis, 2022-05-31)
      A simple, North like, energy balance model on a circle is studied using boundary formulations derived with Green's functions for the stationary case, and a pseudo-spectral and finite difference solution for the time dependent case. The bifurcation software Auto-07p is also applied. The boundary formulation solution can be solved analytically in most cases, and is solved for bifurcation diagrams. ...
    • An Energy Balance Model on an Infinite Line 

      Elvevold, Ask (Master thesis; Mastergradsoppgave, 2022-06-01)
      The thesis is an expansion of the work Gerald R. North did in 1975 on an energy balance climate model. By considering a similar model on an infinite line, and allowing the heat diffusion coefficient to vary on the line, more complicated behaviour arose from the model. Much of Norths work was recreated on the infinite lines, but a lot of new discoveries were made. Among what was found were spontaneous ...
    • Extensions of groups and modules 

      Nermo, Catalina Nicole Vintilescu (Master thesis; Mastergradsoppgave, 2010)
      The main goal of this thesis is to build up detailed constructions and give complete proofs for the extension functors of modules and groups, which we define using cohomology functors. Further, we look at the relations that appear between these and short exact sequences of modules, respectively groups. We calculate also several concrete cohomology groups, and build extensions that are described by ...
    • The Four Faces of Hyperelliptic curves 

      Boyne, Marcus L. (Master thesis; Mastergradsoppgave, 2020-05-13)
      In this thesis we will look at elliptic and hyperelliptic curves. There are three abelian groups that are isomorphic to hyperelliptic curves. The Jacobian of hyperelliptic curves, the ideal class group and the form class group, will all be defined and given abelian group structure. We will give an algorithm for point addition and point doubling done exclusively in the jacobian of the curve. ...
    • Group Cohomology and Extensions 

      Breivik, Markus Nordvoll (Master thesis; Mastergradsoppgave, 2019-08-31)
      The goal of this thesis is to classify all extensions where the kernel has order p^s and the cokernel has order p^t, p is a prime, and 1 ≤ s,t ≤ 2. We determine (up to weak congruence) the different combinations of kernel, cokernel and operators, and for each case, calculate the second cohomology group. By comparing resolutions, we get an explicit correspondence between the second cohomology group ...
    • High frequency financial time series prediction: machine learning approach 

      Zankova, Ekaterina (Master thesis; Mastergradsoppgave, 2016-05-13)
      Machine learning is a rapidly evolving subfield of computer science. It has enormous amount of applications. One of the application domains is financial data analysis. Machine learning was usually applied for analysis and forecasting of daily financial time series. Availability of high frequency financial data became another challenge with its own specifics and difficulties. Regressors, being a ...
    • Homological methods applied to theory of codes and matroids 

      Karpova, Anna (Master thesis; Mastergradsoppgave, 2015-05-15)
      In this thesis we first give a survey of linear error-correcting codes, and how many of their most important properties only depend on the matroids derived from their parity check matrices. We also introduce the Stanley-Reisner ring associated to the simplicial complex of the independent sets of a matroid. We then recall in particular how some important properties of linear codes, including their ...
    • Hopf algebras and monoidal categories 

      Bakke, Tørris Koløen (Master thesis; Mastergradsoppgave, 2007-06-14)
      In this thesis we study the correspondence between categorical notions and bialgebra notions, and make a kind of dictionary and grammar book for translation between these notions. We will show how to obtain an antipode, and how to define braidings and quantizations. The construction is done in two ways. First we use the properties of a bialgebra to define a monoidal structure on (co)modules over ...
    • Ice-albedo tipping points in a diffusive energy-balance model with land and ocean 

      Hilbertsen, Kristian Bergum (Mastergradsoppgave; Master thesis, 2021-01-20)
      The ice-albedo feedback is associated with the nonlinearity in the climate system, due to the sudden change in albedo between ice-free and ice-covered surfaces. This nonlinearity can potentially cause abrupt and dramatic shifts in the climate, referred to as tipping points. It is also believed that this mechanism has contributed significantly to the precipitous losses of Arctic sea ice, which have ...
    • Individual-Based Modeling of COVID-19 Vaccine Strategies 

      Skagseth, Håvard Mikal (Master thesis; Mastergradsoppgave, 2021-06-01)
      COVID-19 is a respiratory disease with influenza-like symptoms originating from Wuhan, China, towards the end of 2019. There has been developed multiple vaccines to contain the virus and to protect the most vulnerable people in society. In this thesis we look at two different vaccination strategies to prevent most deaths and years of life lost. We conclude that the safest and most consistent strategy ...
    • Insulating the Vacuum. Calculating the Casimir force using the boundary integral method with von Neumann boundary conditions 

      Utheim, Marius (Master thesis; Mastergradsoppgave, 2016-08-15)
      In 2012, a new method for calculating the Casimir force between compact objects was developed, expressing the force in terms of a boundary integral equation. The case of perfectly conducting objects with Dirichlet boundary conditions in two dimensions was treated by Isak Kilen. The method was later extended to three dimensions by Karl Øyvind Mikalsen. The contribution of this thesis will be to ...
    • Joint Invariants of Symplectic and Contact Lie Algebra Actions 

      Andreassen, Fredrik (Master thesis; Mastergradsoppgave, 2020-06-23)
      By restricting generating functions of infinitesimal symmetries of symplectic and contact vector spaces to quadratic forms, we obtain a finite-dimensional Lie subalgebra, consisting of vector fields isomorphic to the linear symplectic or conformal symplectic algebra. This allows us to look for joint invariants of the diagonal action of g on product manifolds. We find an explicit recipe for creating ...
    • Killing Tensors in Koutras-McIntosh Spacetimes 

      Steneker, Wijnand (Mastergradsoppgave; Master thesis, 2022-05-15)
      This thesis is concerned with the (non)existence of Killing Tensors in Koutras-McIntosh spacetimes. Killing tensors are of particular interest in general relativity, because these correspond to conserved quantities for the geodesic motion. For instance, Carter found such a conserved quantity in the Kerr metric which he used to explicitly integrate the geodesic equations. The equation defining ...
    • Kompleksiteten til noen kryptologisk viktige algoritmer 

      Brattli, Tore (Master thesis; Mastergradsoppgave, 1990-04-04)
      Denne hovedfagsoppgaven har som mål å sammenligne teoretisk og praktisk kompleksitet til algoritmer som har stor kryptologisk betydning. Et av målene er å avsløre den skjulte konstanten bak O-notasjonen, slik at algoritmene kan sammenlignes på et reelt grunnlag. I tillegg er det sett på sammenheng mellom sikkerhet, størrelsen på tall, asymptotisk og praktisk kompleksitet. Spesielt algoritmer som ...