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Issue A&A
Volume 415, Number 3, March I 2004
Page(s) 813 - 820
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20031693



A&A 415, 813-820 (2004)
DOI: 10.1051/0004-6361:20031693

Two-fluid matter-quintessence FLRW models: Energy transfer and the equation of state of the universe

A. Gromov1, 2, Yu. Baryshev3, 2 and P. Teerikorpi4

1  Centre for Advanced Studies of the Saint-Petersburg State Technical University, 195251 St. Petersburg, Russia
2  Isaac Newton Institute of Chile, St. Petersburg Branch
3  Astronomical Institute of the Saint-Petersburg University, 198904 St. Petersburg, Russia
4  Tuorla Observatory, University of Turku, 21500 Piikkiö, Finland,

(Received 28 August 2002 / Accepted 6 November 2003)

Abstract
The dark energy - dark matter interaction has recently been proposed as a solution of the CDM crisis at galactic halo scales. We have made a study of general properties of two-fluid FLRW models with energy transfer between DE and matter, independently of the specific mechanism of interaction. A mixture of quintessence with negative pressure ( $p_{\rm Q} = w\epsilon_{\rm Q}$) and matter with positive pressure ( $p = \beta \epsilon_{\rm m}$) define the associated one-fluid model ( $p = \gamma \epsilon$). It is shown that, for given  w and  $\beta$, the energy transfer defines  $\gamma$ and, therefore, the total gravitating mass and dynamics of the model. The behaviour of the energy content, gravitating mass, pressure, and energy transfer are given as functions of the scale factor for interesting examples from different two-fluid classes, defined by the presence/absence of energy transfer and by the stationarity/non-stationarity of the equations of state. Three characteristic scales  $a_{\cal E}$, $a_{\cal P}$, $a_{\cal M}$ separate periods of time in which quintessence energy, pressure and gravitating mass dominate. Sequences of the scales define six evolution types.


Key words: cosmology: theory -- cosmology: dark matter

Offprint request: P. Teerikorpi, pekkatee@astro.utu.fi




© ESO 2004


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