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Fredriksson, Sverker
Publications (10 of 73) Show all publications
Johansson, M., Sheridan, J. & Fredriksson, S. (2010). The effect of oscillatory boat-tail flaps on the near wake of a prototypical heavy vehicle (ed.). In: (Ed.), (Ed.), Proceedings of the ASME Fluids Engineering Division summer conference 2010: presented at ASME 2010 3rd Joint US-European Fluids Engineering Division summer meeting, August 1 - 5, 2010, Montreal, Canada ; [jointly with the 8th International Conference on Nanochannels, Microchannels, and Minichannels (ICNMM), and the 7th International Symposium on Fluid Structure Interactions, Flow-Sound Interations, and Flow-Induced Vigrations & Noise (FSI2 & FIV+N)]. Paper presented at ASME 2010 Joint US-European Fluids Engineering Summer Meeting : 01/08/2010 - 05/08/2010 (pp. 2641-2647). New York: American Society of Mechanical Engineers, 1, Symposia – Parts A, B, and C
Open this publication in new window or tab >>The effect of oscillatory boat-tail flaps on the near wake of a prototypical heavy vehicle
2010 (English)In: Proceedings of the ASME Fluids Engineering Division summer conference 2010: presented at ASME 2010 3rd Joint US-European Fluids Engineering Division summer meeting, August 1 - 5, 2010, Montreal, Canada ; [jointly with the 8th International Conference on Nanochannels, Microchannels, and Minichannels (ICNMM), and the 7th International Symposium on Fluid Structure Interactions, Flow-Sound Interations, and Flow-Induced Vigrations & Noise (FSI2 & FIV+N)], New York: American Society of Mechanical Engineers , 2010, Vol. 1, Symposia – Parts A, B, and C, p. 2641-2647Conference paper, Published paper (Refereed)
Abstract [en]

Due to the increased interest in the aerodynamics of truck /trailer combinations as a means to reduce their fuel consumption, experiments have been conducted on a model of a trailer to study possible changes in its near wake arising form attached aft-flaps. The model was fitted with vertical flaps on both sides of the back plate, which were set to oscillate at given frequencies and amplitudes. Experiments were carried out using the PIV system in a Water Channel at Monash University. The oscillation of the flaps perturbed the flow in such a way that the shear layer was significantly changed and the roll up of vortices was moved further upstream, causing a rise in the rate of entrainment and a shorter reattachment length. It also had the effect of a reduced wake size and higher velocities within the wake. These are all effects that are consistent with an increase in the base pressure at the back plate of the trailer and therefore also a reduced drag coefficient, since they are strongly connected

Place, publisher, year, edition, pages
New York: American Society of Mechanical Engineers, 2010
National Category
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Research subject
Fysik
Identifiers
urn:nbn:se:ltu:diva-35692 (URN)10.1115/FEDSM-ICNMM2010-30629 (DOI)80055023704 (Scopus ID)a56d8c2c-15b8-4888-94a0-a5b470287373 (Local ID)978-0-7918-4948-4 (ISBN)a56d8c2c-15b8-4888-94a0-a5b470287373 (Archive number)a56d8c2c-15b8-4888-94a0-a5b470287373 (OAI)
Conference
ASME 2010 Joint US-European Fluids Engineering Summer Meeting : 01/08/2010 - 05/08/2010
Note
Godkänd; 2011; 20111114 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Elfgren, E. & Fredriksson, S. (2008). Mass limits for heavy neutrinos (ed.). Paper presented at . Astronomy and Astrophysics, 479(2), 347-353
Open this publication in new window or tab >>Mass limits for heavy neutrinos
2008 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 479, no 2, p. 347-353Article in journal (Refereed) Published
Abstract [en]

Context. Neutrinos heavier than MZ/2 ∼ 45 GeV are not excluded by particle physics data. Stable neutrinos heavier than this might contribute to the cosmic gamma ray background through annihilation in distant galaxies, as well as to the dark matter content of the universe.Aims. We calculate the evolution of the heavy neutrino density in the universe as a function of its mass, MN, and then the subsequent gamma ray spectrum from annihilation of distant N ¯N (from 0 < z < 5).Methods. The evolution of the heavy neutrino density in the universe is calculated numerically. To obtain the enhancement due to structure formation in the universe, we approximate the distribution of N to be proportional to that of dark matter in the GalICS model. The calculated gamma ray spectrum is compared to the measured EGRET data.Results. A conservative exclusion region for the heavy neutrino mass is 100 to 200 GeV, both fromEGRET data and our re-evalutation of the Kamiokande data. The heavy neutrino contribution to dark matter is found to be at most 15%.

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Identifiers
urn:nbn:se:ltu:diva-8956 (URN)10.1051/0004-6361:20078898 (DOI)783538a0-be05-11dc-a8ca-000ea68e967b (Local ID)783538a0-be05-11dc-a8ca-000ea68e967b (Archive number)783538a0-be05-11dc-a8ca-000ea68e967b (OAI)
Note
Validerad; 2008; 20080108 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-02Bibliographically approved
Gahn, G. F., Grenman, T., Fredriksson, S. & Kristen, H. (2007). Globulettes as seeds of brown dwarfs and free-floating planetary-mass objects (ed.). Paper presented at . Astronomical Journal, 133(4), 1795-1809
Open this publication in new window or tab >>Globulettes as seeds of brown dwarfs and free-floating planetary-mass objects
2007 (English)In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 133, no 4, p. 1795-1809Article in journal (Refereed) Published
Abstract [en]

Some H II regions surrounding young stellar clusters contain tiny dusty clouds, which on photos look like dark spots or teardrops against a background of nebular emission. From our collection of Hα images of 10 H II regions gathered at the Nordic Optical Telescope, we found 173 such clouds, which we call "globulettes," since they are much smaller than normal globules and form a distinct class of objects. Many globulettes are quite isolated and located far from the molecular shells and elephant trunks associated with the regions. Others are attached to the trunks (or shells), suggesting that globulettes may form as a consequence of erosion of these larger structures. None of our objects appear to contain stellar objects. The globulettes were measured for position, dimension, and orientation, and we find that most objects are smaller than 10 kAU. The Rosette Nebula and IC 1805 are particularly rich in globulettes, for which the size distributions peak at mean radii of ∼2.5 kAU, similar to what was found by Reipurth and coworkers and De Marco and coworkers for similar objects in other regions. We estimate total mass and density distributions for each object from extinction measures and conclude that a majority contain <13 MJ, corresponding to planetary-mass objects. We then estimate the internal thermal and potential energies and find, when also including the effects from the outer pressure, that a large fraction of the globulettes could be unstable and would contract on short timescales, < 106 yr. In addition, the radiation pressure and ram pressure exerted on the side facing the clusters would stimulate contraction. Since the globulettes are not screened from stellar light by dust clouds farther in, one would expect photoevaporation to dissolve the objects. However, surprisingly few objects show bright rims or teardrop forms. We calculate the expected lifetimes against photoevaporation. These lifetimes scatter around 4 × 10 6 yr, much longer than estimated in previous studies and also much longer than the free-fall time. We conclude that a large number of our globulettes have time to form central low-mass objects long before the ionization front, driven by the impinging Lyman photons, has penetrated far into the globulette. Hence, the globulettes may be one source in the formation of brown dwarfs and free-floating planetary-mass objects in the galaxy.

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Fysik
Identifiers
urn:nbn:se:ltu:diva-16089 (URN)10.1086/512036 (DOI)facaeea0-6b3e-11dc-9e58-000ea68e967b (Local ID)facaeea0-6b3e-11dc-9e58-000ea68e967b (Archive number)facaeea0-6b3e-11dc-9e58-000ea68e967b (OAI)
Note
Validerad; 2007; 20070925 (bajo)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-04-09Bibliographically approved
Oztas, A., Blacshke, D., Grigorian, H. & Fredriksson, S. (2005). Diquark condensation effects on hot quark star configurations (ed.). In: (Ed.), (Ed.), Superdense QCD matter and compact stars: proceedings of the NATO advanced research workshop on superdense QCD matter and compact stars, Tsachkadzor, Armenia, from 2 to 7 October 2003. Paper presented at NATO Advanced Research Workshop on Superdense QCD Matter and Compact Stars : 27/09/2003 - 04/10/2003 (pp. 341-351). Dordrecht: Encyclopedia of Global Archaeology/Springer Verlag
Open this publication in new window or tab >>Diquark condensation effects on hot quark star configurations
2005 (English)In: Superdense QCD matter and compact stars: proceedings of the NATO advanced research workshop on superdense QCD matter and compact stars, Tsachkadzor, Armenia, from 2 to 7 October 2003, Dordrecht: Encyclopedia of Global Archaeology/Springer Verlag, 2005, p. 341-351Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Dordrecht: Encyclopedia of Global Archaeology/Springer Verlag, 2005
Series
NATO Science Series II: Mathematics, Physics and Chemistry ; 197
National Category
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Research subject
Fysik
Identifiers
urn:nbn:se:ltu:diva-34456 (URN)10.1007/1-4020-3430-X_20 (DOI)8a97e0f0-8d24-11db-8975-000ea68e967b (Local ID)8a97e0f0-8d24-11db-8975-000ea68e967b (Archive number)8a97e0f0-8d24-11db-8975-000ea68e967b (OAI)
Conference
NATO Advanced Research Workshop on Superdense QCD Matter and Compact Stars : 27/09/2003 - 04/10/2003
Note
Validerad; 2003; 20061216 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Carlsson, E., Fedorov, A., Budnik, E., Barabash, S. & Fredriksson, S. (2005). First results from ASPERA-3 Ion Mass Analyzer (IMA) on CO2+ escape (ed.). Paper presented at General Assembly of the European Geosciences Union : 24/04/2005 - 29/04/2005. Paper presented at General Assembly of the European Geosciences Union : 24/04/2005 - 29/04/2005.
Open this publication in new window or tab >>First results from ASPERA-3 Ion Mass Analyzer (IMA) on CO2+ escape
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2005 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Other Physics Topics Aerospace Engineering
Research subject
Fysik; Space Technology
Identifiers
urn:nbn:se:ltu:diva-34288 (URN)87286340-f16a-11db-bb1b-000ea68e967b (Local ID)87286340-f16a-11db-bb1b-000ea68e967b (Archive number)87286340-f16a-11db-bb1b-000ea68e967b (OAI)
Conference
General Assembly of the European Geosciences Union : 24/04/2005 - 29/04/2005
Note
Godkänd; 2005; Bibliografisk uppgift: Titel på proceedings: Geophysical Research Abstracts Volume: Vol. 7, 06351; 20070423 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Blaschke, D., Fredriksson, S., Grigorian, H., Öztas, A. & Sandin, F. (2005). The Phase diagram of three-flavor quark matter under compact star constraints (ed.). Paper presented at . Physical Review D. Particles and fields, 72(6)
Open this publication in new window or tab >>The Phase diagram of three-flavor quark matter under compact star constraints
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2005 (English)In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 72, no 6Article in journal (Refereed) Published
Abstract [en]

The phase diagram of three-flavor quark matter under compact star constraints is investigated within a Nambu-Jona-Lasinio model. Global color and electric charge neutrality is imposed for beta-equilibrated superconducting quark matter. The constituent quark masses and the diquark condensates are determined self-consistently in the plane of temperature and quark chemical potential. Both strong and intermediate diquark coupling strengths are considered. We show that in both cases, gapless superconducting phases do not occur at temperatures relevant for compact star evolution, i.e., below T~50 MeV. The stability and structure of isothermal quark star configurations are evaluated. For intermediate coupling, quark stars are composed of a mixed phase of normal (NQ) and two-flavor superconducting (2SC) quark matter up to a maximum mass of 1.21 M[sun]. At higher central densities, a phase transition to the three-flavor color flavor locked (CFL) phase occurs and the configurations become unstable. For the strong diquark coupling we find stable stars in the 2SC phase, with masses up to 1.33 M[sun]. A second family of more compact configurations (twins) with a CFL quark matter core and a 2SC shell is also found to be stable. The twins have masses in the range 1.30...1.33 M[sun]. We consider also hot isothermal configurations at temperature T=40 MeV. When the hot maximum mass configuration cools down, due to emission of photons and neutrinos, a mass defect of 0.1 M[sun] occurs and two final state configurations are possible

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Identifiers
urn:nbn:se:ltu:diva-5930 (URN)10.1103/PhysRevD.72.065020 (DOI)41ea5ac0-8d1c-11db-8975-000ea68e967b (Local ID)41ea5ac0-8d1c-11db-8975-000ea68e967b (Archive number)41ea5ac0-8d1c-11db-8975-000ea68e967b (OAI)
Note
Validerad; 2005; Bibliografisk uppgift: Paper id:: 065020; 20061216 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-04Bibliographically approved
Blaschke, D., Fredriksson, S., Grigorian, H. & Oztas, A. (2004). Diquark condensation effects on hot quark star configurations (ed.). Paper presented at . Nuclear Physics A, 736(1-2), 203-219
Open this publication in new window or tab >>Diquark condensation effects on hot quark star configurations
2004 (English)In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 736, no 1-2, p. 203-219Article in journal (Refereed) Published
Abstract [en]

The equation of state for quark matter is derived for a nonlocal, chiral quark model within the mean field approximation. We investigate the effects of a variation of the formfactors of the interaction on the phase diagram of quark matter. Special emphasis is on the occurrence of a diquark condensate which signals a phase transition to color superconductivity and its effects on the equation of state under the condition of β-equilibrium and charge neutrality. We calculate the quark star configurations by solving the Tolman-Oppenheimer-Volkoff equations and obtain for the transition from a hot, normal quark matter core of a protoneutron star to a cool diquark condensed one a release of binding energy of the order of ΔMc2˜1053 erg. We find that this energy could not serve as an engine for explosive phenomena since the phase transition is not first order. Contrary to naive expectations the mass defect increases when for a given temperature we neglect the possibility of diquark condensation.

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Identifiers
urn:nbn:se:ltu:diva-11596 (URN)10.1016/j.nuclphysa.2004.02.022 (DOI)a99e3b20-8d24-11db-8975-000ea68e967b (Local ID)a99e3b20-8d24-11db-8975-000ea68e967b (Archive number)a99e3b20-8d24-11db-8975-000ea68e967b (OAI)
Note
Validerad; 2004; 20061216 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Fredriksson, S. (2003). Preon prophecies by the standard model (ed.). In: (Ed.), Hans Volker Klapdor-Kleingrothaus (Ed.), Beyond the desert 2003: proceedings of the Fourth Tegernsee International Conference on Particle Physics Beyond the Standard Model, Beyond 2003, Castle Ringberg, Tegernsee, Germany, 9 - 14 June 2003. Paper presented at International Conference on Physics Beyond the Standard Model : 09/06/2003 - 14/06/2003 (pp. 211-223). Berlin: Encyclopedia of Global Archaeology/Springer Verlag
Open this publication in new window or tab >>Preon prophecies by the standard model
2003 (English)In: Beyond the desert 2003: proceedings of the Fourth Tegernsee International Conference on Particle Physics Beyond the Standard Model, Beyond 2003, Castle Ringberg, Tegernsee, Germany, 9 - 14 June 2003 / [ed] Hans Volker Klapdor-Kleingrothaus, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2003, p. 211-223Conference paper, Published paper (Refereed)
Abstract [en]

The Standard Model of quarks and leptons is, at first sight, nothing but a set of ad hoc rules, with no connections, and no clues to their true background. At a closer look, however, there are many inherent prophecies that point in the same direction: Compositeness in terms of three stable preons.

Place, publisher, year, edition, pages
Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2003
Series
Springer Proceedings in Physics, ISSN 0930-8989 ; 92
National Category
Other Physics Topics
Research subject
Fysik
Identifiers
urn:nbn:se:ltu:diva-33050 (URN)7cd3a7b0-8d1f-11db-8975-000ea68e967b (Local ID)3-540-21843-2 (ISBN)7cd3a7b0-8d1f-11db-8975-000ea68e967b (Archive number)7cd3a7b0-8d1f-11db-8975-000ea68e967b (OAI)
Conference
International Conference on Physics Beyond the Standard Model : 09/06/2003 - 14/06/2003
Note
Godkänd; 2003; Bibliografisk uppgift: Invited talk; 20061216 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Dugne, J.-J., Fredriksson, S. & Hansson, J. (2002). Preon trinity: a schematic model of leptons, quarks and heavy vector bosons (ed.). Paper presented at . Europhysics letters, 60(2), 188-194
Open this publication in new window or tab >>Preon trinity: a schematic model of leptons, quarks and heavy vector bosons
2002 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 60, no 2, p. 188-194Article in journal (Refereed) Published
Abstract [en]

Quarks, leptons and heavy vector bosons are suggested to be composed of stable spin- (1/2) preons, existing in three flavours, combined according to simple rules. Straightforward consequences of an SU(3) preon-flavour symmetry are the conservation of three lepton numbers, oscillations and decays between some neutrinos, and the mixing of the d and s quarks, as well as of the vector fields W0 and B0. We find a relation between the Cabibbo and Weinberg mixing angles, and predict new (heavy) leptons, quarks and vector bosons, some of which might be observable at the Fermilab Tevatron and the future CERN LHC. A heavy neutrino might even be visible in existing data from the CERN LEP facility.

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Fysik
Identifiers
urn:nbn:se:ltu:diva-3974 (URN)10.1209/epl/i2002-00337-8 (DOI)1d3c0cf0-8d26-11db-8975-000ea68e967b (Local ID)1d3c0cf0-8d26-11db-8975-000ea68e967b (Archive number)1d3c0cf0-8d26-11db-8975-000ea68e967b (OAI)
Note
Validerad; 2002; 20061216 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Blaschke, D., Fredriksson, S. & Oztas, A. M. (2001). Diquark properties and the TOV equations (ed.). In: (Ed.), Rachid Ouyed ... (Ed.), Proceedings of the Conference on Compact Stars in the QCD Phase Diagram (CSQCD), Copenhagen, Denmark, August 15 - 18, 2001: . Paper presented at Conference on Compact Stars in the QCD Phase Diagram : 15/08/2001 - 18/08/2001 (pp. 167-173).
Open this publication in new window or tab >>Diquark properties and the TOV equations
2001 (English)In: Proceedings of the Conference on Compact Stars in the QCD Phase Diagram (CSQCD), Copenhagen, Denmark, August 15 - 18, 2001 / [ed] Rachid Ouyed ..., 2001, p. 167-173Conference paper, Published paper (Refereed)
Abstract [en]

We present various results from including diquark properties and the gap equations into the TOV equations for compact quark objects. One such property is the diquark form factor, which has a strong influence on various quantities. We discuss the consequences for quark stars.

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Fysik
Identifiers
urn:nbn:se:ltu:diva-29416 (URN)2e336fa0-8d29-11db-8975-000ea68e967b (Local ID)2e336fa0-8d29-11db-8975-000ea68e967b (Archive number)2e336fa0-8d29-11db-8975-000ea68e967b (OAI)
Conference
Conference on Compact Stars in the QCD Phase Diagram : 15/08/2001 - 18/08/2001
Note
Godkänd; 2001; 20061216 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
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