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C-infinity perturbations of FRW models with a cosmological constant
Umeå University, Faculty of Science and Technology, Physics.
2005 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, Vol. 431, no 2, 415-421 p.Article in journal (Refereed) Published
Abstract [en]

Spatially homogeneous and isotropic cosmological models, with a perfect fluid matter source and non-vanishing cosmological constant, are studied. The equations governing linear perturbations of the space-time and the variation of energy density are given. The complete solution of the problem is obtained for C∞ perturbations, using a comoving time. The Sachs-Wolfe fluctuations of the temperature of the cosmic background radiation are obtained for the relatively growing density perturbations. It is found that the observable celestial microwave fluctuation pattern underwent a reversal approximately two billion years ago. What is observed today is a negative image of the last scattering surface with an attenuation of the fluctuations, due to the presence of the cosmological constant.

Place, publisher, year, edition, pages
2005. Vol. 431, no 2, 415-421 p.
Keyword [en]
cosmology: cosmic microwave background, cosmology: large scale structure of Universe
URN: urn:nbn:se:umu:diva-2890DOI: 10.1051/0004-6361:20041472OAI: diva2:141216
Available from: 2008-01-16 Created: 2008-01-16 Last updated: 2009-10-02Bibliographically approved
In thesis
1. Perturbative Methods in General Relativity
Open this publication in new window or tab >>Perturbative Methods in General Relativity
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Einstein's theory of general relativity is a cornerstone in the process of gaining increased understanding about problems of gravitational nature. It can be applied to problems on the huge length scales of cosmology and as far as we know it does not break down before the Planck scale is approached. Irrespective of scale, a perturbative approach is often a very useful way to reduce the Einstein system to manageable complexity and size.

The projects included in this thesis can be divided into three subcategories. In the first category the keyword is photon-photon scattering. General relativity predicts that scattering can take place on a flat background due to the curvature of space-time caused by the photons themselves. The coupling equations and cross-section are found and a comparison with the corresponding quantum field theoretical results is done to leading order. Moreover, photon-photon scattering due to exchange of virtual electron-positron pairs is considered as an effective field theory in terms of the Heisenberg-Euler Lagrangian resulting in a possible setup for experimental detection of this phenomenon using microwave cavities. The second category of projects is related to cosmology. Here linear perturbations around a flat FRW universe with a cosmological constant are considered and the corresponding temperature variations of the cosmic microwave background radiation are found. Furthermore, cosmological models of Bianchi type V are investigated using a method based on the invariant scheme for classification of metrics by Karlhede. The final category is slowly rotating stars. Here the problem of matching a perfect fluid interior of Petrov type D to an exterior axisymmetric vacuum solution is treated perturbatively up to second order in the rotational parameter.

Place, publisher, year, edition, pages
Umeå: Fysik, 2008. 53 p.
General relativity, perturbation theory, photon-photon scattering, cosmology, FRW models with cosmological constant, Bianchi type V, slowly rotating stars, Hartle formalism
National Category
Physical Sciences
urn:nbn:se:umu:diva-1488 (URN)978-91-7264-493-9 (ISBN)
Public defence
2008-02-07, N420, Naturvetarhuset, Umeå, 14:00
Available from: 2008-01-16 Created: 2008-01-16Bibliographically approved

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