Dark Energy Anisotropic Stress and Large Scale Structure Formation
By Tomi Koivisto, D. Mota. 2005
257 citations recorded by the source corpus.
We investigate the consequences of an imperfect dark energy fluid on the large scale structure. A phenomenological three parameter fluid description is used to study the effect of dark energy on the cosmic microwave background radiation (CMBR) and matter power spectrum. In addition to the equation of state and the sound speed, we allow a nonzero viscosity parameter for the fluid. Then anisotropic stress perturbations are generated in dark energy. In general, we find that this possibility is not excluded by the present day cosmological observations. In the simplest case when all of the three parameters are constant, we find that the observable effects of the anisotropic stress can be closely mimicked by varying the sound speed of perfect dark energy. However, now also negative values for the sound speed, as expected for adiabatic fluid model, are tolerable and in fact could explain the observed low quadrupole in the CMBR spectrum. We investigate also structure formation of imperfect fluid dark energy characterized by an evolving equation of state. In particular, we study models unifying dark energy with dark matter, such as the Chaplygin gas or the Cardassian expansion, with a shear perturbation included. This can stabilize the growth of inhomogeneitiesmore » in these models, thus somewhat improving their compatibility with large scale structure observations.« less
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/4910d652c4b08627987a595edfff9497f242e329
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Citations in the corpus
- Accelerating Cosmologies with an Anisotropic Equation of State (2007, background): “Previous studies anisotropic dark energy have mainly considered the anisotropic properties of the inhomogeneous perturbations (Koivisto and Mota 2006; Battye and Moss 2006) whereas our approach here is to focus on a smooth cosmology with the anisotropic pressure field.”
- Imperfect Dark Energy from Kinetic Gravity Braiding (2010, background): “Other authors have also considered phenomenological models of dark energy which include deviations of the energy-momentum tensor away from the perfect-fluid form such as anisotropic stress [92, 93, 94].”
- Observational probes of cosmic acceleration (2012, background): “…on GR-deviations described by the G9 and ∆γ parameters that characterize structure growth (§2.2), but an alternative approach parametrizes the ratios of Ψ and Φ to their GR-predicted values (see Koivisto and Mota 2006; Bean and Tangmatitham 2010; Daniel and Linder 2010, and references therein).”
- Vector field models of inflation and dark energy (2008, background): “Indeed, it has been proposed that dark energy might have such a characteristic [5], and the possibilities to distinguish it observationally have been examined recently [6, 7].”