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Gravitational perturbations in plasmas and cosmology
Umeå University, Faculty of Science and Technology, Department of Physics.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Gravitational perturbations can be in the form of scalars, vectors or tensors. This thesis focuses on the evolution of scalar perturbations in cosmology, and interactions between tensor perturbations, in the form of gravitational waves, and plasma waves.

The gravitational waves studied in this thesis are assumed to have small amplitudes and wavelengths much shorter than the background length scale, allowing for the assumption of a flat background metric. Interactions between gravitational waves and plasmas are described by the Einstein-Maxwell-Vlasov, or the Einstein-Maxwell-fluid equations, depending on the level of detail required. Using such models, linear wave excitation of various waves by gravitational waves in astrophysical plasmas are studied, with a focus on resonance effects. Furthermore, the influence of strong magnetic field quantum electrodynamics, leading to detuning of the gravitational wave-electromagnetic wave resonances, is considered. Various nonlinear phenomena, including parametric excitation and wave steepening are also studied in different astrophysical settings.

In cosmology the evolution of gravitational perturbations are of interest in processes such as structure formation and generation of large scale magnetic fields. Here, the growth of density perturbations in Kantowski-Sachs cosmologies with positive cosmological constant is studied.

Place, publisher, year, edition, pages
Umeå: Institutionen för Fysik , 2010. , 48 p.
Keyword [en]
general relativity, cosmology, gravitational waves, plasma, electromagnetic waves, nonlinear waves
National Category
Fusion, Plasma and Space Physics Other Physics Topics Astronomy, Astrophysics and Cosmology
Research subject
Theoretical Physics
Identifiers
URN: urn:nbn:se:umu:diva-38387ISBN: 978-91-7459-125-5 (print)OAI: oai:DiVA.org:umu-38387DiVA: diva2:376489
Public defence
2011-01-04, Naturvetarhuset, N430, Umeå Universitet, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2010-12-14 Created: 2010-12-10 Last updated: 2010-12-14Bibliographically approved
List of papers
1. Nonlinear interactions between gravitational radiation and modified Alfvén modes in astrophysical dusty plasmas
Open this publication in new window or tab >>Nonlinear interactions between gravitational radiation and modified Alfvén modes in astrophysical dusty plasmas
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2006 (English)In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 74, 064014-064014-5 p.Article in journal (Refereed) Published
Abstract [en]

We present an investigation of nonlinear interactions between gravitational radiation and modified Alfvén modes in astrophysical dusty plasmas. Assuming that stationary charged dust grains form neutralizing background in an electron-ion-dust plasma, we obtain the three-wave coupling coefficients and calculate the growth rates for parametrically coupled gravitational radiation and modified Alfvén-Rao modes. The threshold value of the gravitational wave amplitude associated with convective stabilization is particularly small if the gravitational frequency is close to twice the modified Alfvén wave frequency. The implication of our results to astrophysical dusty plasmas is discussed.

Place, publisher, year, edition, pages
American Physical Society, 2006
Identifiers
urn:nbn:se:umu:diva-11936 (URN)10.1103/PhysRevD.74.064014 (DOI)
Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2017-12-14Bibliographically approved
2. Harmonic generation of gravitational wave induced Alfven waves
Open this publication in new window or tab >>Harmonic generation of gravitational wave induced Alfven waves
2008 (English)In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 77, no 2, 024050-024050-6 p.Article in journal (Refereed) Published
Abstract [en]

Here we consider the nonlinear evolution of Alfvén waves that have been excited by gravitational waves from merging binary pulsars. We derive a wave equation for strongly nonlinear and dispersive Alfvén waves. Because of the weak dispersion of the Alfvén waves, significant wave steepening can occur, which in turn implies strong harmonic generation. We find that the harmonic generation is saturated due to dispersive effects, and use this to estimate the resulting spectrum. Finally we discuss the possibility of observing the above process.

Place, publisher, year, edition, pages
American Physical Society, 2008
Identifiers
urn:nbn:se:umu:diva-10375 (URN)10.1103/PhysRevD.77.024050 (DOI)
Available from: 2008-08-27 Created: 2008-08-27 Last updated: 2017-12-14Bibliographically approved
3. Interaction between gravitational waves and plasma waves in the Vlasov description
Open this publication in new window or tab >>Interaction between gravitational waves and plasma waves in the Vlasov description
2010 (English)In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, no 76, 345-353 p.Article in journal (Refereed) Published
Abstract [en]

The nonlinear interaction between electromagnetic, electrostatic and gravitational waves in a Vlasov plasma is reconsidered. By using a orthonormal tetrad description the three-wave coupling coefficients are computed. Comparing with previous results, it is found that the present theory leads to algebraic expression that are much reduced, as compared to those computed using a coordinate frame formalism. Furthermore, here we calculate the back reaction on the gravitational waves, and a simple energy conservation law is deduced in the limit of a cold plasma.

Place, publisher, year, edition, pages
Cambridge University Press, 2010
Identifiers
urn:nbn:se:umu:diva-38386 (URN)10.1017/S0022377809990535 (DOI)000278169300013 ()
Available from: 2010-12-10 Created: 2010-12-10 Last updated: 2017-12-11Bibliographically approved
4. Influence of strong field vacuum polarization on gravitational-electromagnetic wave interaction
Open this publication in new window or tab >>Influence of strong field vacuum polarization on gravitational-electromagnetic wave interaction
2010 (English)In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 82, no 2, 024001-024001-7 p.Article in journal (Refereed) Published
Abstract [en]

The interaction between gravitational and electromagnetic waves in the presence of a static magnetic field is studied. The field strength of the static field is allowed to surpass the Schwinger critical field, such that the QED effects of vacuum polarization and magnetization are significant. Equations governing the interaction are derived and analyzed. It turns out that the energy conversion from gravitational to electromagnetic waves can be significantly altered due to the QED effects. The consequences of our results are discussed.

Identifiers
urn:nbn:se:umu:diva-38385 (URN)10.1103/PhysRevD.82.024001 (DOI)000279474100001 ()
Available from: 2010-12-10 Created: 2010-12-10 Last updated: 2017-12-11Bibliographically approved

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