| 1. |
- Ameur, Adam, et al.
(författare)
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SweGen : a whole-genome data resource of genetic variability in a cross-section of the Swedish population
- 2017
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Ingår i: European Journal of Human Genetics. - : NATURE PUBLISHING GROUP. - 1018-4813 .- 1476-5438. ; 25:11, s. 1253-1260
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Tidskriftsartikel (refereegranskat)abstract
- Here we describe the SweGen data set, a comprehensive map of genetic variation in the Swedish population. These data represent a basic resource for clinical genetics laboratories as well as for sequencing-based association studies by providing information on genetic variant frequencies in a cohort that is well matched to national patient cohorts. To select samples for this study, we first examined the genetic structure of the Swedish population using high-density SNP-array data from a nation-wide cohort of over 10 000 Swedish-born individuals included in the Swedish Twin Registry. A total of 1000 individuals, reflecting a cross-section of the population and capturing the main genetic structure, were selected for whole-genome sequencing. Analysis pipelines were developed for automated alignment, variant calling and quality control of the sequencing data. This resulted in a genome-wide collection of aggregated variant frequencies in the Swedish population that we have made available to the scientific community through the website https://swefreq.nbis.se. A total of 29.2 million single-nucleotide variants and 3.8 million indels were detected in the 1000 samples, with 9.9 million of these variants not present in current databases. Each sample contributed with an average of 7199 individual-specific variants. In addition, an average of 8645 larger structural variants (SVs) were detected per individual, and we demonstrate that the population frequencies of these SVs can be used for efficient filtering analyses. Finally, our results show that the genetic diversity within Sweden is substantial compared with the diversity among continental European populations, underscoring the relevance of establishing a local reference data set.
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| 2. |
- Marklund, Mattias, 1970-, et al.
(författare)
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High intensity physics current and future possibilities
- 2009
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X .- 1551-7616. ; 1188:1, s. 301-314
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Tidskriftsartikel (refereegranskat)abstract
- The capability to produce high field strengths, and thereby obtain a new means for doing fundamental physics, has over the last thirty years taken great leaps forward. Both superconducting cavities as well ultra-intense lasers can now reach field strengths of the order 50 MV/m (stationary) and 1012 V/m (peak value, time-dependent field), respectively. Here we will describe a collection of problems that catches the flavor of the nonlinear quantum vacuum and the possibility to use high field strengths as a low-energy probe of fundamental physics.
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| 3. |
- Lundin, Joakim, 1978-
(författare)
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An effective action approach to photon propagation on a magnetized background
- 2009
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 87:3, s. 31001-31005
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Tidskriftsartikel (refereegranskat)abstract
- A new explicit analytical form of the dispersion relation for photon propagation in the presence of a strong background magnetic field is derived within the effective action framework. The dispersion relation is expressed in terms of well-known special functions, and the treatment is exact within the linearization procedure, the one-loop approximation, and the soft photon approximation. The results are incorporated in a kinetic spin plasma description for the purpose of studying quantum electrodynamical effects of strongly magnetized plasmas. The results are applied to astrophysical examples.
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| 4. |
- Lundin, Joakim, 1978-, et al.
(författare)
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Analysis of four-wave mixing of high-power lasers for the detection of elastic photon-photon scattering
- 2006
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : The American Physical Society. - 1050-2947 .- 1094-1622. ; 74:4, s. 043821-043831
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Tidskriftsartikel (refereegranskat)abstract
- We derive expressions for the coupling coefficients for electromagnetic four-wave mixing in the nonlinear quantum vacuum. An experimental setup for detection of elastic photon-photon scattering is suggested, where three incoming laser pulses collide and generate a fourth wave with a new frequency and direction of propagation. An expression for the number of scattered photons is derived and, using beam parameters for the Astra Gemini system at the Rutherford Appleton Laboratory, it is found that the signal can reach detectable levels. Problems with shot-to-shot reproducibility are reviewed, and the magnitude of the noise arising from competing scattering processes is estimated. It is found that detection of elastic photon-photon scattering may be achieved.
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| 5. |
- Lundin, Joakim, 1978-, et al.
(författare)
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Circularly polarized waves in a plasma with vacuum polarization effects
- 2007
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Ingår i: Physics of Plasmas. - : American Institute of Physics. - 1070-664X .- 1089-7674. ; 14:6, s. 064503-3 sidor
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Tidskriftsartikel (refereegranskat)abstract
- The theory for large amplitude circularly polarized waves propagating along an external magnetic field is extended in order to also include vacuum polarization effects. A general dispersion relation, which unites previous results, is derived.
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| 6. |
- Lundin, Joakim, 1978-, et al.
(författare)
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Linearized kinetic theory of spin-1/2 particles in magnetized plasmas
- 2010
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - : APS physics. - 1063-651X .- 1095-3787. ; 82:5, s. 054607-10 pages
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Tidskriftsartikel (refereegranskat)abstract
- We have considered linear kinetic theory, including the electron-spin properties in a magnetized plasma. The starting point is a mean-field Vlasov-like equation, derived from a fully quantum-mechanical treatment, where effects from the electron-spin precession and the magnetic dipole force are taken into account. The general conductivity tensor is derived, including both the free current contribution and the magnetization current associated with the spin contribution. We conclude the paper with an extensive discussion of the quantummechanical boundary where we list parameter conditions that must be satisfied for various quantum effects to be influential.
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| 7. |
- Lundin, Joakim, 1978-, et al.
(författare)
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Modified Jeans instability criteria for magnetized systems
- 2008
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 15:7, s. 072116-072121
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Tidskriftsartikel (refereegranskat)abstract
- The Jeans instability is analyzed for dense magnetohydrodynamic plasmas with intrinsic magnetization, the latter due to collective electron spin effects. Furthermore, the effects of electron tunneling as well as the Fermi pressure are included. It is found that the intrinsic magnetization of the plasma will enhance the Jeans instability, and can significantly modify the structure of the instability spectra. Implications and limitations of our results are discussed, as well as possible generalizations.
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| 8. |
- Lundin, Joakim, 1978-
(författare)
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QED and collective effects in vacuum and plasmas
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The theory of quantum electrodynamics (QED) was born out of an attempt to merge Einsteins theory of special relativity and quantum mechanics. Einsteins energy/mass equivalence together with Heisenberg's uncertainty principle allows for particle pairs to be spontaneously created and annihilated in vacuum. These spontaneous fluctuations gives the quantum vacuum properties analogous to that of a nonlinear medium. Although these fluctuations in general does not give note of themselves, effects due to their presence can be stimulated or enhanced through external means, such as boundary conditions or electromagnetic fields. Whereas QED has been very well tested in the high-energy, low-intensity regime using particle accelerators, the opposite regime where the photon energy is low but instead the intensity is high is still to a large degree not investigated. This is expected to change with the rapid progress of modern high-power laser-systems. In this thesis we begin by studying the QED effect of photon-photon scattering. This process has so far not been successfully verified experimentally, but we show that this may change already with present day laser powers. We also study QED effects due to strong magnetic fields. In particular, we obtain an analytical description for vacuum birefringence valid at arbitrary field strengths. Astrophysics already offer environments where QED processes may be influential, e.g. in neutron star and magnetar environments. For astrophysical purposes we investigate how effects of QED can be implemented in plasma models. In particular, we study QED dispersive effects due to weak rapidly oscillating fields, nonlinear effects due to slowly varying strong fields, as well as QED effects in strongly magnetized plasmas. Effects of quantum dispersion and the electron spin has also been included in an extended plasma description, of particular interest for dense and/or strongly magnetized systems.
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| 9. |
- Lundin, Joakim, 1978-, et al.
(författare)
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Short wavelength electromagnetic propagation in magnetized quantum plasmas
- 2007
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Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 14:6
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Tidskriftsartikel (refereegranskat)abstract
- The quantum electrodynamical (QED) short wavelength correction on plasma wave propagation for a nonrelativistic quantum plasma is investigated. A general dispersion relation for a thermal multicomponent quantum plasma is derived. It is found that the classical dispersion relation for any wave mode can be modified to include quantum and short wavelength QED effects by simple substitutions of the thermal velocity and the plasma frequency. Furthermore, the dispersion relation has been modified to include QED effects of strong magnetic fields. It is found that strong magnetic fields together with the short wavelength QED correction will induce dispersion both in vacuum and in otherwise nondispersive plasma modes. Applications to laboratory and astrophysical systems are discussed.
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| 10. |
- Lundin, Joakim, 1978-, et al.
(författare)
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Short wavelength quantum electrodynamical correction to cold plasma-wave propagation
- 2006
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Ingår i: Physics of Plasmas. - : American Institute of Physics. - 1070-664X .- 1089-7674. ; 13:10, s. 102102-102107
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Tidskriftsartikel (refereegranskat)abstract
- The effect of short wavelength quantum electrodynamic (QED) correction on plasma-wave propagation is investigated. The effect on plasma oscillations and on electromagnetic waves in an unmagnetized as well as a magnetized plasma is investigated. The effects of the short wavelength QED corrections are most evident for plasma oscillations and for extraordinary modes. In particular, the QED correction allow plasma oscillations to propagate, and the extraordinary mode loses its stop band. The significance of our results is discussed.
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| 11. |
- Lundström, E., et al.
(författare)
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Using high-power lasers for detection of elastic photon-photon scattering.
- 2006
-
Ingår i: Physical Review Letters. - : The American Physical Society. - 0031-9007 .- 1079-7114. ; 96:8, s. 083602-083605
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Tidskriftsartikel (refereegranskat)abstract
- The properties of four-wave interaction via the nonlinear quantum vacuum is investigated. The effect of the quantum vacuum is to generate photons with new frequencies and wave vectors, due to elastic photon-photon scattering. An expression for the number of generated photons is derived, and using state-of-the-art laser data it is found that the number of photons can reach detectable levels. In particular, the prospect of using the high-repetition Astra Gemini system at the Rutherford Appleton Laboratory is discussed. The problem of noise sources is reviewed, and it is found that the noise level can be reduced well below the signal level. Thus, detection of elastic photon-photon scattering may for the first time be achieved.
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| 12. |
- Marklund, Mattias, 1970-, et al.
(författare)
-
Nonlinear propagation of partially coherent dispersive Alfvén waves.
- 2006
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Ingår i: Physica Scripta. - : INSTITUTE OF PHYSICS PUBLISHING. - 0031-8949 .- 1402-4896. ; 74:3, s. 373-376
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Tidskriftsartikel (refereegranskat)abstract
- The effects of partial coherence on the propagation of dispersive Alfvén waves in a magnetoplasma are investigated. In particular, nonlinear interactions between dispersive Alfvén waves and ion-acoustic perturbations are considered by means of a Wigner formalism. A set of governing equations consisting of a kinetic equation for dispersive Alfvén waves coupled nonlinearly to a ponderomotive force driven ion-acoustic wave equation is obtained. The governing nonlinear equations are used to derive a nonlinear dispersion relation that is appropriate for investigating the modulational instability of broadband Alfvén wavepackets. The spectral broadening of the Alfvén waves gives rise to new regimes for the growth rate of the modulational instability.
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| 13. |
- Marklund, Mattias, 1970-, et al.
(författare)
-
Quantum vacuum experiments using high intensity lasers
- 2009
-
Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 55, s. 319-326
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Tidskriftsartikel (refereegranskat)abstract
- The quantum vacuum constitutes a fascinating medium of study, in particular since near-future laser facilities will be able to probe the nonlinear nature of this vacuum. There has been a large number of proposed tests of the low-energy, high intensity regime of quantum electrodynamics (QED) where the nonlinear aspects of the electromagnetic vacuum come into play, and we will here give a short description of some of these. Such studies can shed light, not only on the validity of QED, but also on certain aspects of nonperturbative effects, and thus also give insights for quantum field theories in general.
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