ﻻ يوجد ملخص باللغة العربية
The effect of quintessence perturbations on the ISW effect is studied for a mixed dynamical scalar field dark energy (DDE) and pressureless perfect fluid dark matter. A new and general methodology is developed to track the growth of the perturbations, which uses only the equation of state (EoS) parameter $w_{rm DDE} (z) equiv p_{rm DDE}/rho_{rm DDE}$ of the scalar field DDE, and the initial values of the the relative entropy perturbation (between the matter and DDE) and the intrinsic entropy perturbation of the scalar field DDE as inputs. We also derive a relation between the rest frame sound speed $hat{c}_{s,{rm DDE}}^2$ of an arbitrary DDE component and its EoS $w_{rm DDE} (z)$. We show that the ISW signal differs from that expected in a $Lambda$CDM cosmology by as much as +20% to -80% for parameterizations of $w_{rm DDE}$ consistent with SNIa data, and about $pm$ 20% for parameterizations of $w_{rm DDE}$ consistent with SNIa+CMB+BAO data, at 95% confidence. Our results indicate that, at least in principle, the ISW effect can be used to phenomenologically distinguish a cosmological constant from DDE.
Any Dark Energy (DE) or Modified Gravity (MG) model that deviates from a cosmological constant requires a consistent treatment of its perturbations, which can be described in terms of an effective entropy perturbation and an anisotropic stress. We ha
We show that in clustering dark energy models the growth index of linear matter perturbations, $gamma$, can be much lower than in $Lambda$CDM or smooth quintessence models and present a strong variation with redshift. We find that the impact of dark
We present the cross-correlation of the density map of LRGs and the temperature fluctuation in the CMB as measured by the WMAP5 observations. The LRG samples were extracted from imaging data of the SDSS based on two previous spectroscopic redshift su
In this paper we study the evolution of cosmological perturbations in the presence of dynamical dark energy, and revisit the issue of dark energy perturbations. For a generally parameterized equation of state (EoS) such as w_D(z) = w_0+w_1frac{z}{1+z
We show that a general late-time interaction between cold dark matter and vacuum energy is favoured by current cosmological datasets. We characterize the strength of the coupling by a dimensionless parameter $q_V$ that is free to take different value