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Friction forces in cosmological models
Stockholm University, Faculty of Science, Department of Physics. Albert Einstein Inst, Max Planck Inst Gravitat Phys,Potsdam, Germany.
2013 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 73, no 2, 2334- p.Article in journal (Refereed) Published
Abstract [en]

We investigate the dynamics of test particles undergoing friction forces in a Friedmann-Robertson-Walker (FRW) spacetime. The interaction with the background fluid is modeled by introducing a Poynting-Robertson-like friction force in the equations of motion, leading to measurable (at least in principle) deviations of the particle trajectories from geodesic motion. The effect on the peculiar velocities of the particles is investigated for various equations of state of the background fluid and different standard cosmological models. The friction force is found to have major effects on particle motion in closed FRW universes, where it turns the time-asymptotic value (approaching the recollapse) of the peculiar particle velocity from ultra-relativistic (close to light speed) to a co-moving one, i.e., zero peculiar speed. On the other hand, for open or flat universes the effect of the friction is not so significant, because the time-asymptotic peculiar particle speed is largely non-relativistic also in the geodesic case.

Place, publisher, year, edition, pages
2013. Vol. 73, no 2, 2334- p.
Keyword [en]
National Category
Physical Sciences
URN: urn:nbn:se:su:diva-90802DOI: 10.1140/epjc/s10052-013-2334-9ISI: 000318289600034OAI: diva2:627644
EU, FP7, Seventh Framework Programme, 2011-1640


Available from: 2013-06-12 Created: 2013-06-11 Last updated: 2014-09-04Bibliographically approved
In thesis
1. Cosmological models, nonideal fluids and viscous forces in general relativity
Open this publication in new window or tab >>Cosmological models, nonideal fluids and viscous forces in general relativity
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis addresses the open questions of providing a cosmological model describing an accelerated expanding Universe without violating the energy conditions or a model that contributes to the physical interpretation of the dark energy. The former case is analyzed considering a closed model based on a regular lattice of black holes using the Einstein equation in vacuum. In the latter case I will connect the dark energy to the Shan-Chen equation of state. A comparison between these two proposals is then discussed. As a complementary topic I will discuss the motion of test particles in a general relativistic spacetime undergoing friction effects. This is modeled following the formalism of Poynting-Robertson whose link with the Stokes’ formula is presented. The cases of geodesic and non-geodesic motion are compared and contrasted for Schwarzschild, Tolman, Pant-Sah and Friedman metrics respectively.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2014. 94 p.
gravity, exact model, black hole, friction
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Theoretical Physics
urn:nbn:se:su:diva-107130 (URN)978-91-7447-982-9 (ISBN)
Public defence
2014-11-07, room FP41, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Available from: 2014-10-14 Created: 2014-09-03 Last updated: 2015-03-17Bibliographically approved

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Gregoris, Daniele
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