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  • 1.
    Jääskeläinen, Markku
    Dalarna University, School of Technology and Business Studies, Physics.
    Gravitational self-localization for spherical masses2012In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 86, no 5, article id 052105Article in journal (Refereed)
    Abstract [en]

    In this work, I consider the center-of-mass wave function for a homogenous sphere under the influence of the self-interaction due to Newtonian gravity. I solve for the ground state numerically and calculate the average radius as a measure of its size. For small masses, M≲10−17 kg, the radial size is independent of density, and the ground state extends beyond the extent of the sphere. For masses larger than this, the ground state is contained within the sphere and to a good approximation given by the solution for an effective radial harmonic-oscillator potential. This work thus determines the limits of applicability of the point-mass Newton Schrödinger equations for spherical masses. In addition, I calculate the fringe visibility for matter-wave interferometry and find that in the low-mass case, interferometry can in principle be performed, whereas for the latter case, it becomes impossible. Based on this, I discuss this transition as a possible boundary for the quantum-classical crossover, independent of the usually evoked environmental decoherence. The two regimes meet at sphere sizes R≈10−7 m, and the density of the material causes only minor variations in this value.

  • 2.
    Jääskeläinen, Markku
    Dalarna University, School of Technology and Business Studies, Physics.
    The wave function as matter density: ontological assumptions and experimental consequences2015In: Foundations of physics, ISSN 0015-9018, E-ISSN 1572-9516, Vol. 45, no 6, p. 591-610Article in journal (Refereed)
    Abstract [en]

    The wavefunction is the central mathematical entity of quantum mechanics, but it still lacks a universally accepted interpretation. Much effort is spent on attempts to probe its fundamental nature. Here I investigate the consequences of a matter ontology applied to spherical masses of constant bulk density. The governing equation for the center-of-mass wavefunction is derived and solved numerically. The ground state wavefunctions and resulting matter densities are investigated. A lowering of the density from its bulk value is found for low masses due to increased spatial spreading. A discussion of the possibility to experimentally observe these effects is given and the possible consequences for choosing an ontological interpretation for quantum mechanics are commented upon.

  • 3.
    Jääskeläinen, Markku
    et al.
    Dalarna University, School of Technology and Business Studies, Physics.
    Lagerkvist, Andreas
    Dalarna University, School of Technology and Business Studies, Mathematics.
    Why do they not answer and do they really learn?: A case study in analysing student response flows in introductory physics using an audience response system2017In: European journal of physics, ISSN 0143-0807, E-ISSN 1361-6404, Vol. 38, no 4, article id 045705Article in journal (Refereed)
    Abstract [en]

    In this paper we investigate teaching with a classroom response system in introductory physics with emphasis on two issues. First, we discuss retention between question rounds and the reasons why students avoid answering the question a second time. A question with declining response rate was followed by a question addressing the student reasons for not answering. We find that there appear to be several reasons for the observed decline, and that the students need to be reminded. We argue that small drops are unimportant as the process appears to work despite the drops. Second, we discuss the dynamics of learning in a concept-sequence in electromagnetism, where a majority of the students, despite poor statistics in a first round, manage to answer a followup question correctly. In addition, we analyse the response times for both situations to connect with research on student reasoning on situations with misconception-like answers. From the combination of the answer flows and response time behaviours we find it plausible that conceptual learning occurred during the discussion phase.

  • 4.
    Linnaeus, Staffan
    Dalarna University, School of Technology and Business Studies, Physics.
    Phase-integral solution of the radial Dirac equation2010In: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 51, no 3, article id 032304Article in journal (Refereed)
    Abstract [en]

    A phase-integral (WKB) solution of the radial Dirac equation is constructed, retaining perfect symmetry between the two components of the wave function and introducing no singularities except at the classical transition points. The potential is allowed to be the time component of a four-vector, a Lorentz scalar, a pseudoscalar, or any combination of these. The key point in the construction is the transformation from two coupled first-order equations constituting the radial Dirac equation to a single second-order Schroumldinger-type equation. This transformation can be carried out in infinitely many ways, giving rise to different second-order equations but with the same spectrum. A unique transformation is found that produces a particularly simple second-order equation and correspondingly simple and well-behaved phase-integral solutions. The resulting phase-integral formulas are applied to unbound and bound states of the Coulomb potential. For bound states, the exact energy levels are reproduced.

  • 5.
    Linnaeus, Staffan
    Dalarna University, School of Technology and Business Studies, Physics.
    Stokes constants for a singular wave equation2005In: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 45, no 5, article id 053505Article in journal (Refereed)
    Abstract [en]

    The Stokes constants for arbitrary-order phase-integral approximations are calculated when the square of the wave number has either two simple zeros close to a second-order pole or one simple zero close to a first-order pole. The treatment is based on uniform approximations. All parameters may assume general complex values.

  • 6. Oknyanskij, V. I
    et al.
    van Groningen, Ernst
    Dalarna University, School of Technology and Business Studies, Physics.
    Spectral Variability of NGC 4151 During 19901999In: Structure and Kinematics of Quasar Broad Line Regions, ASP Conference Series, 1999, Vol. 175Conference paper (Other academic)
  • 7. Thylwe, Karl-Erik
    et al.
    Linnaeus, Staffan
    Dalarna University, School of Technology and Business Studies, Physics.
    Semiclassical aspects and supersymmetry of bound Dirac states for central pseudo-scalar potentials2011In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 84, no 2, article id 025006Article in journal (Refereed)
    Abstract [en]

    Relativistic bound states for a linear, radial pseudo-scalar potential model are discussed. The two radial Dirac components are known to have a close connection to partner states in super-symmetric quantum mechanical theory. The pseudo-scalar potential plays the role of the 'super potential'. Hence, the Dirac components satisfy decoupled Schrodinger-type equations with isospectral, so-called, 'partner potentials' except possibly for a single state; the ground state corresponding to one of the partner potentials. The energy spectrum of a confining linear radial potential is discussed in some detail. Accurate amplitude-phase computations and a novel semiclassical (phase-integral) approach are presented.

  • 8. Wisotzki, L.
    et al.
    Jahnke, K.
    Kuhlbrodt, B.
    van Groningen, Ernst
    Dalarna University, School of Technology and Business Studies, Physics.
    Örndahl, E.
    Spectroscopy and Imaging of QSO Host Galaxies2000In: Stars, Gas and Dust in Galaxies: Exploring the Links, ASP Conference Proceedings / [ed] Olsen, Knut; Galaz, Gaspar; Alloin, Danielle, San Francisco: Astronomical Society of the Pacific, 2000, Vol. 221Conference paper (Other academic)
  • 9.
    Zivkovic, Marko
    et al.
    Stevens Institute of Technology.
    Jääskeläinen, Markku
    Dalarna University, School of Technology and Business Studies, Physics. Department of Physics and Engineering Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA.
    Search, Christopher P.
    Stevens Institute of Technology.
    Djuric, Ivana
    Stevens Institute of Technology.
    Sagnac rotational phase shifts in a mesoscopic electron interferometer with spin-orbit interactions2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 11, article id 115306Article in journal (Refereed)
    Abstract [en]

    The Sagnac effect is an important phase coherent effect in optical and atom interferometers where rotations of the interferometer with respect to an inertial reference frame result in a shift in the interference pattern proportional to the rotation rate. Here, we analyze the Sagnac effect in a mesoscopic semiconductor electron interferometer. We include in our analysis the Rashba spin-orbit interactions in the ring. Our results indicate that spin-orbit interactions increase the rotation-induced phase shift. We discuss the potential experimental observability of the Sagnac phase shift in such mesoscopic systems.

  • 10. Örndahl, E.
    et al.
    Rönnback, J.
    van Groningen, Ernst
    Dalarna University, School of Technology and Business Studies, Physics.
    An optical imaging study of 0.4 <= z <= 0.8 quasar host galaxies. I. Observations and reduction2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 404, p. 883-899Article in journal (Refereed)
    Abstract [en]

    We have conducted an optical imaging study aimed at resolving the host galaxies of 79 radio-loud and radio-quiet quasars at z=0.4-0.8, extending the number of investigated objects in this redshift range by ~ 45%. Observations were performed mainly in the R band but also in V and I band using the Nordic Optical Telescope on La Palma. In this paper we discuss the sample composition and observations and the reduction techniques used. The quasars were selected in pairs of radio-loud and radio-quiet objects matched in the z-V plane in order to facilitate a statistical comparison. The radio-loud part of the sample contains comparable numbers of flat and steep radio spectrum sources which also are matched in redshift and V magnitude. Point spread function subtraction was performed using one-dimensional luminosity profiles both on the quasar image and on a field star, and subtracted images and luminosity profiles are shown for each quasar field. The detection rate is 60% for the radio-quiet host galaxies and 80% for radio-loud hosts. The host galaxies have magnitudes which make them brighter than an L* galaxy by a factor of 1.5-4 at the low end of the redshift range, which increases by 2-3 times towards the higher end of the redshift range. Both radio-quiet and radio-loud hosts follow the radio galaxy R-z Hubble relation well. Analysis and discussion of colours and morphology is presented in \citet{orn}. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

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