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  • 1. Aarnio, A
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Measurement of the mass and width of the Zo particle from multihadron final states produced in e+e--annihilations1989In: Physics Letters, no 231, p. p 539-Article in journal (Other academic)
  • 2. Aarnio, A
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Study of the hadronic decays of the Zo boson1990In: Physics Letters, no 240, p. p 271-Article in journal (Other academic)
  • 3. Aarnio, A
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Study of the leptonic decays of the Zo boson1990In: Physics Letters, no 241, p. p 425-Article in journal (Other academic)
  • 4. Abdollahi, S.
    et al.
    Acero, F.
    Ackermann, M.
    Ajello, M.
    Atwood, W. B.
    Axelsson, M.
    Baldini, L.
    Ballet, J.
    Larsson, Stefan
    Dalarna University, School of Education, Health and Social Studies, Natural Science. KTH Royal Inst Technol / AlbaNova, Oskar Klein Ctr Cosmoparticle Phys.
    Zaharijas, G.
    Fermi Large Area Telescope Fourth Source Catalog2020In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 247, no 1, article id 33Article in journal (Refereed)
    Abstract [en]

    We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range from 50 MeV to 1 TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse gamma-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4 sigma significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.

  • 5. Abdollahi, S.
    et al.
    Acero, F.
    Ackermann, M.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science. Department of Physics, KTH Royal Institute of Technology, AlbaNova, Stockholm; The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, Stockholm.
    Zaharijas, G.
    Search for New Cosmic-Ray Acceleration Sites within the 4FGL Catalog Galactic Plane Sources2022In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 933, no 2, article id 204Article in journal (Refereed)
    Abstract [en]

    Cosmic rays are mostly composed of protons accelerated to relativistic speeds. When those protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma-rays. This offers a compelling way to identify the acceleration sites of protons. A characteristic hadronic spectrum, with a low-energy break around 200 MeV, was detected in the gamma-ray spectra of four supernova remnants (SNRs), IC 443, W44, W49B, and W51C, with the Fermi Large Area Telescope. This detection provided direct evidence that cosmic-ray protons are (re-)accelerated in SNRs. Here, we present a comprehensive search for low-energy spectral breaks among 311 4FGL catalog sources located within 5° from the Galactic plane. Using 8 yr of data from the Fermi Large Area Telescope between 50 MeV and 1 GeV, we find and present the spectral characteristics of 56 sources with a spectral break confirmed by a thorough study of systematic uncertainty. Our population of sources includes 13 SNRs for which the proton-proton interaction is enhanced by the dense target material; the high-mass gamma-ray binary LS I+61 303; the colliding wind binary η Carinae; and the Cygnus star-forming region. This analysis better constrains the origin of the gamma-ray emission and enlarges our view to potential new cosmic-ray acceleration sites. © 2022. The Author(s). Published by the American Astronomical Society.

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  • 6. Abdollahi, S.
    et al.
    Acero, F.
    Baldini, L.
    Ballet, J.
    Bastieri, D.
    Bellazzini, R.
    Berenji, B.
    Berretta, A.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science.
    Zaharijas, G.
    Incremental Fermi Large Area Telescope Fourth Source Catalog2022In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 260, no 2, article id 53Article in journal (Refereed)
    Abstract [en]

    We present an incremental version (4FGL-DR3, for Data Release 3) of the fourth Fermi Large Area Telescope (LAT) catalog of 3-ray sources. Based on the first 12 years of science data in the energy range from 50 MeV to 1 TeV, it contains 6658 sources. The analysis improves on that used for the 4FGL catalog over eight years of data: more sources are fit with curved spectra, we introduce a more robust spectral parameterization for pulsars, and we extend the spectral points to 1 TeV. The spectral parameters, spectral energy distributions, and associations are updated for all sources. Light curves are rebuilt for all sources with 1 yr intervals (not 2 month intervals). Among the 5064 original 4FGL sources, 16 were deleted, 112 are formally below the detection threshold over 12 yr (but are kept in the list), while 74 are newly associated, 10 have an improved association, and seven associations were withdrawn. Pulsars are split explicitly between young and millisecond pulsars. Pulsars and binaries newly detected in LAT sources, as well as more than 100 newly classified blazars, are reported. We add three extended sources and 1607 new point sources, mostly just above the detection threshold, among which eight are considered identified, and 699 have a plausible counterpart at other wavelengths. We discuss the degree-scale residuals to the global sky model and clusters of soft unassociated point sources close to the Galactic plane, which are possibly related to limitations of the interstellar emission model and missing extended sources. © 2022. The Author(s). Published by the American Astronomical Society.

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  • 7. Ajello, M.
    et al.
    Angioni, R.
    Axelsson, M.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Becerra Gonzalez, J.
    Bellazzini, R.
    Larsson, Stefan
    Dalarna University, School of Education, Health and Social Studies, Natural Science. KTH Royal Inst Technology / AlbaNova, Oskar Klein Ctr Cosmoparticle Phys.
    Yassine, M.
    The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope2020In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 892, no 2, article id 105Article in journal (Refereed)
    Abstract [en]

    The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) between 2008 August 4 and 2016 August 2 contains . It includes 85% more sources than the previous 3LAC catalog based on 4 yr of data. AGNs represent at least 79% of the high-latitude sources in the fourth Fermi-Large Area Telescope Source Catalog (4FGL), which covers the energy range from 50 MeV to 1 TeV. In addition, gamma-ray AGNs are found at low Galactic latitudes. Most of the 4LAC AGNs are blazars (98%), while the remainder are other types of AGNs. The blazar population consists of 24% Flat Spectrum Radio Quasars (FSRQs), 38% BL Lac-type objects, and 38% blazar candidates of unknown types (BCUs). On average, FSRQs display softer spectra and stronger variability in the gamma-ray band than BL Lacs do, confirming previous findings. All AGNs detected by ground-based atmospheric Cerenkov telescopes are also found in the 4LAC.

  • 8.
    Ajello, M.
    et al.
    Clemson Univ, Kinard Lab Phys, Dept Phys & Astron, Clemson, SC 29634 USA..
    Arimoto, M.
    Kanazawa Univ, Inst Sci & Engn, Fac Math & Phys, Kanazawa, Ishikawa 9201192, Japan..
    Asano, K.
    Univ Tokyo, Inst Cosm Ray Res, 5-1-5 Kashiwanoha, Kashiwa, Chiba 2778582, Japan..
    Axelsson, M.
    Stockholm Univ, AlbaNova, Dept Phys, SE-10691 Stockholm, Sweden.;KTH Royal Inst Technol, Dept Phys, AlbaNova, SE-10691 Stockholm, Sweden..
    Baldini, L.
    Univ Pisa, I-56127 Pisa, Italy.;Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Barbiellini, G.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy..
    Bastieri, D.
    Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy.;Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    Bellazzini, R.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Larsson, Stefan
    Dalarna University, School of Education, Health and Social Studies, Natural Science. KTH / The Oskar Klein Centre for Cosmoparticle Physics.
    Tajima, H.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA.;Nagoya Univ, Solar Terr Environm Lab, Nagoya, Aichi 4648601, Japan..
    Bright Gamma-Ray Flares Observed in GRB 131108A2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 886, no 2, article id L33Article in journal (Refereed)
    Abstract [en]

    GRB 131108A is a bright long gamma-ray burst (GRB) detected by the Large Area Telescope and the Gamma-ray Burst Monitor on board the Fermi Gamma-ray Space Telescope. Dedicated temporal and spectral analyses reveal three ?-ray flares dominating above 100 MeV, which are not directly related to the prompt emission in the Gamma-ray Burst Monitor band (10 keV?10 MeV). The high-energy light curve of GRB 131108A (100 MeV?10 GeV) shows an unusual evolution: a steep decay, followed by three flares with an underlying emission, and then a long-lasting decay phase. The detailed analysis of the ?-ray flares finds that the three flares are 6?20 times brighter than the underlying emission and are similar to each other. The fluence of each flare, (1.6?2.0)10(?6) erg cm(?2), is comparable to that of emission during the steep decay phase, 1.710(?6) erg cm(?2). The total fluence from three ?-ray flares is 5.310(?6) erg cm(?2). The three ?-ray flares show properties similar to the usual X-ray flares that are sharp flux increases, occurring in ?50% of afterglows, in some cases well after the prompt emission. Also, the temporal and spectral indices during the early steep decay phase and the decaying phase of each flare show the consistency with a relation of the curvature effect (<CDATA<i=2 + <CDATA<i), which is the first observational evidence of the high-latitude emission in the GeV energy band.

  • 9. Ajello, M.
    et al.
    Arimoto, M.
    Axelsson, M.
    Baldini, L.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Berretta, A.
    Larsson, Stefan
    Dalarna University, School of Education, Health and Social Studies, Natural Science. KTH / The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova.
    De Pasquale, M.
    Fermi and Swift Observations of GRB 190114C: Tracing the Evolution of High-energy Emission from Prompt to Afterglow2020In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 890, no 1, article id 9Article in journal (Refereed)
    Abstract [en]

    We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory. The prompt gamma-ray emission was detected by the Fermi GRB Monitor (GBM), the Fermi Large Area Telescope (LAT), and the Swift Burst Alert Telescope (BAT) and the long-lived afterglow emission was subsequently observed by the GBM, LAT, Swift X-ray Telescope (XRT), and Swift UV Optical Telescope. The early-time observations reveal multiple emission components that evolve independently, with a delayed power-law component that exhibits significant spectral attenuation above 40 MeV in the first few seconds of the burst. This power-law component transitions to a harder spectrum that is consistent with the afterglow emission observed by the XRT at later times. This afterglow component is clearly identifiable in the GBM and BAT light curves as a slowly fading emission component on which the rest of the prompt emission is superimposed. As a result, we are able to observe the transition from internal-shock- to external-shock-dominated emission. We find that the temporal and spectral evolution of the broadband afterglow emission can be well modeled as synchrotron emission from a forward shock propagating into a wind-like circumstellar environment. We estimate the initial bulk Lorentz factor using the observed high-energy spectral cutoff. Considering the onset of the afterglow component, we constrain the deceleration radius at which this forward shock begins to radiate in order to estimate the maximum synchrotron energy as a function of time. We find that even in the LAT energy range, there exist high-energy photons that are in tension with the theoretical maximum energy that can be achieved through synchrotron emission from a shock. These violations of the maximum synchrotron energy are further compounded by the detection of very high-energy (VHE) emission above 300 GeV by MAGIC concurrent with our observations. We conclude that the observations of VHE photons from GRB 190114C necessitates either an additional emission mechanism at very high energies that is hidden in the synchrotron component in the LAT energy range, an acceleration mechanism that imparts energy to the particles at a rate that is faster than the electron synchrotron energy-loss rate, or revisions of the fundamental assumptions used in estimating the maximum photon energy attainable through the synchrotron process. © 2020. The American Astronomical Society..

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  • 10. Ajello, M
    et al.
    Atwood, W B
    Axelsson, M
    Bagagli, R
    Bagni, M
    Baldini, L
    Bastieri, D
    Bellardi, F
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science.
    Zaharijas, G.
    Fermi Large Area Telescope Performance after 10 Years of Operation2021In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 256, no 1, article id 12Article in journal (Refereed)
    Abstract [en]

    The Large Area Telescope (LAT), the primary instrument for the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from 30 MeV to more than 300 GeV. We describe the performance of the instrument at the 10 yr milestone. LAT performance remains well within the specifications defined during the planning phase, validating the design choices and supporting the compelling case to extend the duration of the Fermi mission. The details provided here will be useful when designing the next generation of high-energy gamma-ray observatories.

  • 11. Ajello, M.
    et al.
    Atwood, W. B.
    Axelsson, M.
    Baldini, L.
    Barbiellini, G.
    Baring, M. G.
    Bastieri, D.
    Bellazzini, R.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science. KTH Royal Inst Technol / Oskar Klein Ctr Cosmoparticle Phys.
    Zaharijas, G.
    High-energy emission from a magnetar giant flare in the Sculptor galaxy2021In: Nature Astronomy, E-ISSN 2397-3366, Vol. 5, no 4, p. 385-391Article in journal (Refereed)
    Abstract [en]

    Magnetars are the most highly magnetized neutron stars in the cosmos (with magnetic field 10(13)-10(15) G). Giant flares from magnetars are rare, short-duration (about 0.1 s) bursts of hard X-rays and soft gamma rays(1,2). Owing to the limited sensitivity and energy coverage of previous telescopes, no magnetar giant flare has been detected at gigaelectronvolt (GeV) energies. Here, we report the discovery of GeV emission from a magnetar giant flare on 15 April 2020 (refs. (3,4) and A. J. Castro-Tirado et al., manuscript in preparation). The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected GeV gamma rays from 19 s until 284 s after the initial detection of a signal in the megaelectronvolt (MeV) band. Our analysis shows that these gamma rays are spatially associated with the nearby (3.5 megaparsecs) Sculptor galaxy and are unlikely to originate from a cosmological gamma-ray burst. Thus, we infer that the gamma rays originated with the magnetar giant flare in Sculptor. We suggest that the GeV signal is generated by an ultra-relativistic outflow that first radiates the prompt MeV-band photons, and then deposits its energy far from the stellar magnetosphere. After a propagation delay, the outflow interacts with environmental gas and produces shock waves that accelerate electrons to very high energies; these electrons then emit GeV gamma rays as optically thin synchrotron radiation. This observation implies that a relativistic outflow is associated with the magnetar giant flare, and suggests the possibility that magnetars can power some short gamma-ray bursts.

  • 12. Ajello, M.
    et al.
    Atwood, W. B.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Berretta, A.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science.
    Zaharijas, G.
    A gamma-ray pulsar timing array constrains the nanohertz gravitational wave background2022In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 376, no 6592, p. 521-523Article in journal (Refereed)
  • 13.
    Ajello, M.
    et al.
    Clemson Univ, Dept Phys & Astron, Kinard Lab Phys, Clemson, SC 29634 USA..
    Baldini, L.
    Univ Pisa, I-56127 Pisa, Italy.;Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Ballet, J.
    Univ Paris, Univ Paris Saclay, CNRS, AIM,CEA, F-91191 Gif Sur Yvette, France..
    Barbiellini, G.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy..
    Bastieri, D.
    Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy.;Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    Bellazzini, R.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Berretta, A.
    Univ Perugia, Dipartimento Fis, I-06123 Perugia, Italy..
    Bissaldi, E.
    Univ & Politecn Bari, Dipartimento Fis M Merlin, Via Amendola 173, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science. KTH Royal Inst Technol; AlbaNova, Oskar Klein Ctr Cosmoparticle Phys.
    Zrake, J.
    Clemson Univ, Dept Phys & Astron, Kinard Lab Phys, Clemson, SC 29634 USA..
    Gamma Rays from Fast Black-hole Winds2021In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 921, no 2, article id 144Article in journal (Refereed)
    Abstract [en]

    Massive black holes at the centers of galaxies can launch powerful wide-angle winds that, if sustained over time, can unbind the gas from the stellar bulges of galaxies. These winds may be responsible for the observed scaling relation between the masses of the central black holes and the velocity dispersion of stars in galactic bulges. Propagating through the galaxy, the wind should interact with the interstellar medium creating a strong shock, similar to those observed in supernovae explosions, which is able to accelerate charged particles to high energies. In this work we use data from the Fermi Large Area Telescope to search for the gamma-ray emission from galaxies with an ultrafast outflow (UFO): a fast (v similar to 0.1 c), highly ionized outflow, detected in absorption at hard X-rays in several nearby active galactic nuclei (AGN). Adopting a sensitive stacking analysis we are able to detect the average gamma-ray emission from these galaxies and exclude that it is due to processes other than UFOs. Moreover, our analysis shows that the gamma-ray luminosity scales with the AGN bolometric luminosity and that these outflows transfer similar to 0.04% of their mechanical power to gamma-rays. Interpreting the observed gamma-ray emission as produced by cosmic rays (CRs) accelerated at the shock front, we find that the gamma-ray emission may attest to the onset of the wind-host interaction and that these outflows can energize charged particles up to the transition region between galactic and extragalactic CRs.

  • 14. Ajello, M.
    et al.
    Baldini, L.
    Bastieri, D.
    Bellazzini, R.
    Berretta, A.
    Bissaldi, E.
    Blandford, R. D.
    Bonino, R.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science. KTH Royal Institute of Technology, AlbaNova, Stockholm; The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, Stockholm.
    Zaharijas, G.
    First fermi-LAT solar flare catalog2021In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 252, no 2, article id abd32eArticle in journal (Refereed)
  • 15. Askebjer, P
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    AMANDA: Status Report from the 1993/94 Campaign and Optical Properties of the South Pole Ice1995In: Nuclear Physics, no 38, p. 287-292Article in journal (Refereed)
  • 16. Askebjer, P
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    First Data and Future Prospects for AMANDA, the Antarctic Muon and Neutrino Detector1994In: Antarctic Journal of the United States, no 29, p. 337-339Article in journal (Other academic)
  • 17. Askebjer, P
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Remote Surveys of AMANDA1995In: Contribution to the XXIV International Cosmic Ray Conference, Rome 1995, 1995Conference paper (Other academic)
  • 18. Bergström, Lars
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Detection of High Energy Neutrinos in PAN1992In: Proceedings of the Workshop on High Energy Neutrino Astrophysics, Univ. Hawaai at Manoa, Honolulu, Hawaii, March 23-26, 1992., 1992Conference paper (Other academic)
  • 19.
    Bernad, Joszef Zsolt
    et al.
    Massey University.
    Jääskeläinen, Markku
    Dalarna University. Institute of Fundamental Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, Massey University, Palmerston North, New Zealand.
    Zulicke, Ulrich
    Massey University.
    Effects of a quantum measurement on the electric conductivity: Application to graphene2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 7, article id 073403Article in journal (Refereed)
    Abstract [en]

    We generalize the standard linear-response (Kubo) theory to obtain the conductivity of a system that is subject to a quantum measurement of the current. Our approach can be used to specifically elucidate how back-action inherent to quantum measurements affects electronic transport. To illustrate the utility of our general formalism, we calculate the frequency-dependent conductivity of graphene and discuss the effect of measurement-induced decoherence on its value in the dc limit. We are able to resolve an ambiguity related to the parametric dependence of the minimal conductivity.

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  • 20. Burns, M
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Physics aspects of the DELPHI vertex detector1988Conference paper (Other (popular science, discussion, etc.))
  • 21. Dijkstra, F
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Physics aspects of the DELPHI vertex detector1989In: Nuclear Instruments and Methods, no 277, p. p 160-Article in journal (Refereed)
  • 22.
    Dutta, Omjyoti
    et al.
    University of Arizona.
    Jääskeläinen, Markku
    Department of Physics and College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, USA.
    Meystre, Pierre
    University of Arizona.
    Polarizing beam splitter for dipolar molecules2005In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 71, no 5, article id 051601(R)Article in journal (Refereed)
    Abstract [en]

    We propose a coherent beam splitter for polarized heteronuclear molecules based on a stimulated Raman adiabatic passage scheme that uses a tripod linkage of electrotranslational molecular states. We show that for strongly polarized molecules the rotational dynamics imposes significantly larger Rabi frequencies than would otherwise be expected, but within this limitation, a full transfer of the molecules to two counterpropagating ground-state wave packets is possible.

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  • 23.
    Dutta, Omjyoti
    et al.
    University of Arizona.
    Jääskeläinen, Markku
    Department of Physics and College of Optical Sciences, The University of Arizona.
    Meystre, Pierre
    University of Arizona.
    Single-mode acceleration of matter waves in circular waveguides2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, no 2, article id 023609Article in journal (Refereed)
    Abstract [en]

    Ultracold gases in ring geometries hold promise for significant improvements of gyroscopic sensitivity. Recent experiments have realized atomic and molecular storage rings with radii in the centimeter range, sizes whose practical use in inertial sensors requires velocities significantly in excess of typical recoil velocities. We use a combination of analytical and numerical techniques to study the coherent acceleration of matter waves in circular waveguides, with particular emphasis on its impact on single-mode propagation. In the simplest case we find that single-mode propagation is best maintained by the application of time-dependent acceleration force with the temporal profile of a Blackmann pulse. We also assess the impact of classical noise on the acceleration process.

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  • 24.
    Dutta, Omjyoti
    et al.
    University of Arizona.
    Jääskeläinen, Markku
    Department of Physics and College of Optical Sciences, The University of Arizona, Tucson, Arizona 85721, USA.
    Meystre, Pierre
    University of Arizona.
    Thomas-Fermi ground state of dipolar fermions in a circular storage ring2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 73, no 4, article id 043610Article in journal (Refereed)
    Abstract [en]

    Recent developments in the field of ultracold gases has led to the production of degenerate samples of polar molecules. These have large static electric-dipole moments, which in turn causes the molecules to interact strongly. We investigate the interaction of polar particles in waveguide geometries subject to an applied polarizing field. For circular waveguides, tilting the direction of the polarizing field creates a periodic inhomogeneity of the interparticle interaction. We explore the consequences of geometry and interaction for stability of the ground state within the Thomas-Fermi model. Certain combinations of tilt angles and interaction strengths are found to preclude the existence of a stable Thomas-Fermi ground state. The system is shown to exhibit different behavior for quasi-one-dimensional and three-dimensional trapping geometries.

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  • 25. Erlandsson, Bengt
    et al.
    Johansson, Sverker
    Dalarna University, Not School affiliated. Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Measurements of the Absorption Length of the Ice at the South Pole in the Wavelength Interval 410 nm to 610 nm1995In: The XXIV International Cosmic Ray Conference, Rome 1995, 1995Conference paper (Other academic)
  • 26. Fermi-Lat Collaboration, T.
    et al.
    Baldini, L.
    Ballet, J.
    Bastieri, D.
    Becerra Gonzalez, J.
    Bellazzini, R.
    Berretta, A.
    Bissaldi, E.
    Larsson, Stefan
    Dalarna University, School of Teacher Education, Natural Science. KTH Royal Institute of Technology, Stockholm; The Oskar Klein Centre for Cosmoparticle Physics, Stockholm.
    Cavazzuti, E.
    Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data2021In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 256, no 1, article id 13Article in journal (Refereed)
  • 27.
    Fritsch, Katarina
    Dalarna University, School of Education, Health and Social Studies, Educational Work.
    Meningsskapande samtal om fysikens begrepp: Att utgå från elevernas erfarenheter och förförståelse2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med studien är att undersöka vad tidigare forskning säger om hur lärare kan organisera fysikundervisningen för att stödja elever, i årskurs 4 – 9, till meningsskapande samtal om fysikens begrepp. I denna systematiska litteraturstudie presenteras resultat utifrån litteratur som noggrant valts ut genom en systematisk sökningsprocess i databaserna Summon, ERIC, Nordina och avhandlingar.se där all litteratur har genomgått peer review. Studiens resultat visar att elever tillsammans bidrar till meningsskapande samtal genom att tillföra egna erfarenheter och förkunskaper om fysikens begrepp. Studien visar hur eleverna kan diskutera fritt så länge de har något att diskutera utifrån, exempelvis praktiska experiment, bilder, artefakter eller texter. Lärarens roll är sedan att stödja eleverna till att använda och förstå de korrekta vetenskapliga begreppen. Studien visar att läraren kan göra detta genom att koppla till vardagliga objekt och företeelser, ställa utmanande frågor, synliggöra nyckelbegrepp och elevers förförståelse samt återkoppla till elevers lärande. Med dessa olika metoder agerar läraren som en riktningsgivare som guidar eleven i en kunskapsutvecklande riktning. Genom att utgå från samt synliggöra elevernas förförståelse får både elever och lärare kunskap om eventuella missuppfattningar. Detta bidrar i sin tur till meningsskapande samtal då eleverna börjar ifrågasätta samt förändra och utveckla sin förståelse för fysiken begrepp. 

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    Examensarbete
  • 28. Geng, X.
    et al.
    Zeng, W.
    Rani, B.
    Britto, R. J.
    Zhang, G.
    Wen, T.
    Hu, W.
    Larsson, Stefan
    Dalarna University, School of Education, Health and Social Studies, Natural Science. Department of Physics, KTH Royal Institute of Technology;Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, Stockholm.
    Thompson, D. J.
    Dai, B.
    Exploring high-energy emission from the bl lacertae object s5 0716+714 with the fermi large area telescope2020In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 904, no 1, article id abb603Article in journal (Refereed)
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  • 29. Gray, P
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    The Design of a Neutrino Telescope Using Natural Deep Ice as a Particle Detector1995In: The XXIV International Cosmic Ray Conference, Rome 1995, 1995Conference paper (Other academic)
  • 30. Halzen, Francis
    et al.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Status of the AMANDA South Pole Neutrino Detector1996In: The International Workshop on Aspects of Dark Matter in Astrophysics and Particle Physics, Heidelberg, Germany, September 1996, 1996Conference paper (Other academic)
  • 31.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    A study of mu-mu- and e-mu-pairs produced in 450 GeV/c p-Be--collisions in HELIOS, and software development for DELPHI.1990Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The main part of this thesis treats measurements in the HELIOS experiment of the production of e-mu and mu+mu-pairs in 450 GeV/c p-Be collisions. The mumu measurement covers the kinematical covers the kinematical range of 2Mmu < M < 1.5 GeV, 0.03 < xF < 0.25, and 0 < pT < 2 GeV. Production of the vector mesons rho, omega , and phi is observed. The branching ratio omega to mu+mu- is for the first time experimentally measured. The continuum at masses below the mu mass is studied, and compared with the contributions from known sources, normalized to the vector meson peaks in the mu+mu- mass spectrum, and to measurements in this experiment of the mu cross section. The res ult is compared with that of other experiments, discussed in terms of different background estimates used. A significant signal of unlike-sign e-mu-pairs is observed, forming a continuum peaking at a mass below 500 MeV. Correlations between e-mu and neutrino production are studied. The shape of the e-mu mass and missng-energy spectra indicate significant non-charm contributions. A search for lepton-number-violating decays is made, resulting in upper limits on a number of branching ratios. Also discussed here is the author's work in the DELPHI experiment, contributions that are related to analysis of heavy quark production. Keywords: muon. pair, dimuon, dilepton, lepton, low mass, continuum, eta, rho, omega, branching ratio, emu, e-mu, mue, mu-e, muon-electron, electron-muon, electron, charm, neutrino, missing energy

  • 32.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Cosmic rays and free neutrinos affect decay rates2005In: The Counter-Creationism handbook, Westport: Greenwood Publishing , 2005Chapter in book (Other (popular science, discussion, etc.))
  • 33.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Dimuon production in 450 GeV/c p-Be collisions1990In: Proceedings of the Pittsburgh Workshop on Soft Lepton Pair and Photon Production, Sept 6-8, 1990, 1990Conference paper (Other academic)
  • 34.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, Medie-, litteratur- och språkdidaktik.
    Från ostkupan till den stora smällen2004Book (Other academic)
  • 35.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Measuring the energy of multi-TeV muons with a water Cherenkov detector1991In: Proceedings of the 22nd International Cosmic Ray Conference, Dublin, Aug 11-23, 1991, 1991Conference paper (Refereed)
  • 36.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Sagan om hur allting började1996Other (Other (popular science, discussion, etc.))
  • 37.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    The Cathedral of Physics1997In: Vetenskapens ansikten / [ed] Hans-Albin Larsson, Jönköping: Jönköping University Press , 1997Chapter in book (Other academic)
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  • 38.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    The Solar FAQ: Solar Neutrinos and Other Solar Oddities1998Other (Other (popular science, discussion, etc.))
  • 39.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    The Solar Neutrino Problem is Not a Solar Problem1999Report (Other (popular science, discussion, etc.))
  • 40.
    Johansson, Sverker
    Högskolan i Jönköping.
    The transverse energy distribution in 16O-nucleus collisions at 60 and 200 GeV per nucleon1988In: Zeitschrift für Physik C, Vol. 38, p. 383-395Article in journal (Refereed)
  • 41.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Transverse energy distribution in 16O -nucleus collisions1987In: 6th International conference on ultra-relativistic nucleus-nucleus collisions: Nordkirchen, FR Germany, 24 - 28 Aug 1987, 1987, p. 15-18Conference paper (Other academic)
  • 42.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Transverse energy distribution in 16O -nucleus collisions1988In: Zeitschrift für Physik C, no 38, p. 15-18Article in journal (Other academic)
  • 43.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Universums mörka hemlighet1993In: Högskriften: (personaltidning för Högskolan i Jönköping), Vol. april/majArticle in journal (Other (popular science, discussion, etc.))
  • 44.
    Johansson, Sverker
    Högskolan för lärande och kommunikation, Högskolan i Jönköping, HLK, Ämnesforskning.
    Vackrare värld med fysik2006In: Lärandets konst: betraktelser av estetiska dimensioner i lärandet, Lund: Studentlitteratur , 2006, p. 105-126Chapter in book (Other academic)
  • 45.
    Jonsson, Anna
    et al.
    Linköpings universitet.
    Andersson, Lotta
    Swedish Meteorological Hydrological Institute.
    Alkan Olsson, Johanna
    Lunds universitet.
    Johansson, Madelaine
    Linköpings universitet.
    Defining goals in participatory water management: merging local visions and expert judgements2011In: Journal of Environmental Planning and Management, ISSN 0964-0568, E-ISSN 1360-0559, Vol. 54, no 7, p. 909-935Article in journal (Refereed)
    Abstract [en]

    Management by objectives is intrinsic to the EU Water Framework Directive (WFD) and Swedish environmental policy. We describe three approaches to formulating objectives via model-assisted dialogue with local stakeholders concerning eutrophication in a coastal drainage area in south-eastern Sweden: a WFD eco-centred approach based on ‘natural state’; Swedish environmental policy reformulated into quantified reduction goals; and a participatory approach based on local stakeholder definitions of desirable environmental status. Despite problems with representation, we conclude that local stakeholder participation in formulating local goals could increase goal functionality and robustness when adapting and implementing national and EU WFD goals at the local level.

  • 46.
    Junkala, Hannele
    Dalarna University, School of Education, Health and Social Studies, Natural Science.
    Fysik, formler, förkroppsligande och förståelse2016In: Forskning i Naturvetenskapernas Didaktik: Konferenstema: Kroppsligt lärande i den naturvetenskapliga undervisningen, 2016Conference paper (Refereed)
    Abstract [sv]

    Vad kan barn och elever vinna i förståelse genom att uppleva olika begrepp med kroppen och sinnena? Vi utför några försök inom naturvetenskap och teknik och diskuterar hur kroppsliga upplevelser kan leda till ökad förståelse av bland annat tyngdpunkt, balans, krafter, enkla maskiner och temperatur. Genom att jämföra några laborativa moment, som utförs med material som man ofta hittar i traditionella NO-salar, med försök där man medvetet använder kroppen och sinnena, får vi gemensamma upplevelser att diskutera vidare kring. Vilka fler fenomen och begrepp behöver vi hitta och utveckla försök till, som kan bidra till att fördjupa elevernas förståelse?  Vi delar med oss av våra erfarenheter och frågor, tolkningar av styrdokument samt vad vi eventuellt känner till från aktuell forskning.

  • 47.
    Junkala, Hannele
    Dalarna University, School of Education, Health and Social Studies, Natural Science.
    Lekplatsfysik som ett moment i utomhuspedagogik för Erasmusstudenter2016Conference paper (Refereed)
    Abstract [sv]

    Lekplatsfysik som ett moment i utomhuspedagogik för Erasmusstudenter

    Sedan vårterminen 2013 ger Högskolan Dalarna kursen Outdoor Education för internationella studenter inom Erasmusprogrammet. Efter kursen ska studenterna bland annat visa kunskap om hur utomhusdidaktik kan användas i naturvetenskapsundervisningen samt reflektera över utomhusdidaktik i ett jämförande internationellt perspektiv. De flesta av studenterna läser till lärare men några studerar till ingenjör, kurator eller jurist.

    Undervisningen i lekplatsfysik äger rum på en lekplats mellan Lugnets camping och riksskidstadion i Falun, belägen nära Högskolan Dalarna. I försöken ingår moment med eld, balans, gravitation, fritt fall, gungor, karuseller, burktelefoner och ballonger. Aktiviteterna pågår under en halv dag och följs upp med en hemuppgift som består av några ytterligare experiment kopplade till gungbräda, balans, rullande burkar, pendel samt teori. Avslutningsvis följer frågor om vad läroplanen i hemlandet anger om fysikundervisning och hur studenterna anser att de kan använda lekplatsfysik i sina framtida yrken samt om de kan hitta användbara hemsidor på nätet på deras eget språk. En del av svaren visar att studenterna uppfattar fysik som svårt från sin egen skolgång på grund av tonvikt på teori. De ser efter kursen möjlighet att väcka intresse för ämnet hos elever i framtiden genom upplevelser av fysik med kroppens sinnen utanför det traditionella klassrummet.

  • 48.
    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.

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  • 49.
    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.

  • 50.
    Jääskeläinen, Markku
    et al.
    Department of Physics and Engineering Physics, Stevens Institute of Technology, Castle Point on the Hudson, Hoboken, New Jersey 07030, USA.
    Corvino, Frank
    Search, Christopher P.
    Fessatidis, Vassilios
    Quantum pumping of electrons by a moving modulated potential2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 15, p. 155319-Article in journal (Refereed)
    Abstract [en]

    Quantum pumping holds great potential for future applications in microtechnology and nanotechnology. Its main feature, which is the dissipationless charge transport, is theoretically possible via several different mechanisms. However, since no unambiguous verification has been experimentally demonstrated, the question of finding a viable mechanism for pumping remains open. Here, we study quantum pumping in an one dimensional electron waveguide with a single time-dependent barrier. The quantum pumping of electrons by using a potential barrier whose height and position are harmonically varied is analytically analyzed and by numerically solving the time-dependent Schrodinger equation. The pumped charge is analytically modeled by including two contributions in linear response theory. First, the scattering of electrons off a potential moving slowly through matter waves gives a contribution independent of the translational velocity of the potential. Second, Doppler-shifted scattering events give rise to a velocity dependent contribution, which is found in general to be small in comparison with the first one. The relative phase between the oscillations of the height and position is found to be the factor that determines to what extent either contribution is present.

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