Institutt for matematiske fag
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Mathematics teaching practices at university level
(Chapter, 2021) 
A Duality Principle for Groups II: Multiframes Meet SuperFrames
(Peer reviewed; Journal article, 2020)The duality principle for group representations developed in Dutkay et al. (J Funct Anal 257:1133–1143, 2009), Han and Larson (Bull Lond Math Soc 40:685–695, 2008) exhibits a fact that the wellknown duality principle in ... 
A Regularized System for the Nonlinear Variational Wave Equation
(Doctoral theses at NTNU;2021:21, Doctoral thesis, 2021) 
A Verifiable and Practical LatticeBased Decryption Mix Net with External Auditing
(Peer reviewed; Journal article, 2020)Mix nets are often used to provide privacy in modern security protocols, through shuffling. Some of the most important applications, such as secure electronic voting, require mix nets that are verifiable. In the literature, ... 
How not to prove your election outcome
(Peer reviewed; Journal article, 2020)The Scytl/SwissPost evoting solution was intended to provide complete verifiability for Swiss government elections. We show failures in both individual verifiability and universal verifiability (as defined in Swiss Federal ... 
C∗uniqueness Results for Groupoids
(Peer reviewed; Journal article, 2020)For a 2ndcountable locally compact Hausdorff étale groupoid G with a continuous 2cocycle σ we find conditions that guarantee that ℓ1(G,σ) has a unique C∗norm. 
Discussion of "Virtual age, is it real?"
(Peer reviewed; Journal article, 2020)I congratulate the authors on this very interesting article discussing various aspects of the virtual age concept, which has been in active use in reliability and lifetime analyses for at least three decades. At the same ... 
Can students' attitudes and behaviors be changed by educational interventions? A comparative case study
(Peer reviewed; Journal article, 2020)This study examined engineering students’ attitudes and behaviors in a firstyear Calculus course. Not surprisingly, High School mathematics and physics grades correlated closely with selfreported Calculus grades, and a ... 
Contributions to the Theory of GoodnessofFit Testing and Change Point Detection
(Doctoral theses at NTNU;2021:20, Doctoral thesis, 2021) 
A converse to the Schwarz lemma for planar harmonic maps
(Peer reviewed; Journal article, 2021)A sharp version of a recent inequality of Kovalev and Yang on the ratio of the (H1)∗ and H4 norms for certain polynomials is obtained. The inequality is applied to establish a sharp and tractable sufficient condition for ... 
On Whitham's conjecture of a highest cusped wave for a nonlocal dispersive equation
(Peer reviewed; Journal article, 2019)We consider the Whitham equation ut + 2uux + Lux = 0, where L is the nonlocal Fourier multiplier operator given by the symbol m(ξ) = p tanh ξ/ξ. G. B. Whitham conjectured that for this equation there would be a highest, ... 
Universality and distribution of zeros and poles of some zeta functions
(Peer reviewed; Journal article, 2020)This paper studies zeta functions of the form P∞ n=1 χ(n)n −s , with χ a completely multiplicative function taking only unimodular values. We denote by σ(χ) the infimum of those α such that the Dirichlet series P∞ n=1 χ(n)n ... 
Optimal recovery of a radiating source with multiple frequencies along one line
(Peer reviewed; Journal article, 2020)We study an inverse problem where an unknown radiating source is observed with collimated detectors along a single line and the medium has a known attenuation. The research is motivated by applications in SPECT and beam ... 
Global bifurcation of waves with multiple critical layers
(Journal article; Peer reviewed, 2020)Analytic global bifurcation theory is used to construct a large variety of families of steady periodic twodimensional gravity water waves with realanalytic vorticity distributions, propagating in an incompressible fluid. ... 
On the Stability of Solitary Water Waves with a Point Vortex
(Journal article; Peer reviewed, 2020)This paper investigates the stability of traveling wave solutions to the free boundary Euler equations with a submerged point vortex. We prove that sufficiently small‐amplitude waves with small enough vortex strength are ... 
Enhanced existence time of solutions to the fractional Korteweg de Vries equation
(Peer reviewed; Journal article, 2019)We consider the fractional Korteweg–de Vries equation ut+ uux−D αux = 0 in the range of −1 < α < 1, α 6= 0. Using basic Fourier techniques in combination with the modified energy method we extend the existence time of ... 
Characterizing changes of dissolved organic matter composition with the use of distinct feeds in recirculating aquaculture systems via highresolution mass spectrometry
(Peer reviewed; Journal article, 2020)Recirculating aquaculture systems (RAS) are a new alternative to traditional aquaculture approaches, allowing full control over the fish production conditions, while reducing the water demand. The reduction of water exchange ... 
The Notion of Presence in a Telematic CrossDisciplinary Program for Music,Communication and Technology
(Chapter, 2020)This anthology presents research projects that examine the intersection between music, technology and education from a variety of perspectives. The contributors are from a range of educational programs within traditional ... 
Exponential decay of solitary waves to DegasperisProcesi equation
(Peer reviewed; Journal article, 2020)We improve the decay argument by Bona and Li (1997) [5] for solitary waves of general dispersive equations and illustrate it in the proof for the exponential decay of solitary waves to steady DegasperisProcesi equation ... 
Local Gorenstein duality for cochains on spaces
(Peer reviewed; Journal article, 2021)We investigate when a commutative ring spectrum R satisfies a homotopical version of local Gorenstein duality, extending the notion previously studied by Greenlees. In order to do this, we prove an ascent theorem for local ...