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Dark energy from cosmological fluids obeying a Shan-Chen nonideal equation of state
Stockholm University, Faculty of Science, Department of Physics.
2013 (English)In: Physical Review D, ISSN 1550-7998, Vol. 88, no 6, 063007- p.Article in journal (Refereed) Published
Abstract [en]

We consider a Friedmann-Robertson-Walker universe with a fluid source obeying a nonideal equation of state with asymptotic freedom, namely ideal gas behavior (pressure changes directly proportional to density changes) both at low and high density regimes, following a fluid dynamical model due to Shan and Chen. It is shown that, starting from an ordinary energy density component, such fluids naturally evolve towards a universe with a substantial dark energy component at the present time, with no need of invoking any cosmological constant. Moreover, we introduce a quantitative indicator of darkness abundance, which provides a consistent picture of the actual matter-energy content of the Universe.

Place, publisher, year, edition, pages
2013. Vol. 88, no 6, 063007- p.
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-94731DOI: 10.1103/PhysRevD.88.063007ISI: 000324237800001OAI: diva2:655133


Funding Agencies:

EACEA of the European Commission 2011-1640 

Available from: 2013-10-10 Created: 2013-10-09 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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