اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدImproved parametrization of the growth index for dark energy and DGP models
181
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We propose two improved parameterized form for the growth index of the linear matter perturbations: (I) $gamma(z)=gamma_0+(gamma_{infty}-gamma_0){zover z+1}$ and (II) $gamma(z)=gamma_0+gamma_1 frac{z}{z+1}+(gamma_{infty}-gamma_1-gamma_0)(frac{z}{z+1})^{alpha}$. With these forms of $gamma(z)$, we analyze the accuracy of the approximation the growth factor $f$ by $Omega^{gamma(z)}_m$ for both the $omega$CDM model and the DGP model. For the first improved parameterized form, we find that the approximation accuracy is enhanced at the high redshifts for both kinds of models, but it is not at the low redshifts. For the second improved parameterized form, it is found that $Omega^{gamma(z)}_m$ approximates the growth factor $f$ very well for all redshifts. For chosen $alpha$, the relative error is below 0.003% for the $Lambda$CDM model and 0.028% for the DGP model when $Omega_{m}=0.27$. Thus, the second improved parameterized form of $gamma(z)$ should be useful for the high precision constraint on the growth index of different models with the observational data. Moreover, we also show that $alpha$ depends on the equation of state $omega$ and the fractional energy density of matter $Omega_{m0}$, which may help us learn more information about dark energy and DGP models.
قيم البحث
اقرأ أيضاً
We derive an analytical expression for the growth rate of matter density perturbations on the phantom brane (which is the normal branch of the Dvali-Gabadadze-Porrati model). This model is characterized by a phantomlike effective equation of state fo
r dark energy at the present epoch. It agrees very well with observations. We demonstrate that the traditional parametrization $f=Omega_m^gamma$ with a quasiconstant growth index $gamma$ is not successful in this case. Based on a power series expansion at large redshifts, we propose a different parametrization for this model: $f=Omega_m^gammaleft(1+frac{b}{ell H}right)^beta$, where $beta$ and $b$ are constants. Our numerical simulations demonstrate that this new parametrization describes the growth rate with great accuracy - the maximum error being $leq 0.1%$ for parameter values consistent with observations.
We study the phase space of the quintom cosmologies for a class of exponential potentials. We combine normal forms expansions and the center manifold theory in order to describe the dynamics near equilibrium sets. Furthermore, we construct the unstab
le and center manifold of the massless scalar field cosmology motivated by the numerical results given in Lazkoz and Leon (Phys Lett B 638:303. arXiv:astro-ph/0602590, 2006). We study the role of the curvature on the dynamics. Several monotonic functions are defined on relevant invariant sets for the quintom cosmology. Finally, conservation laws of the cosmological field equations and algebraic solutions are determined by using the symmetry analysis and the singularity analysis.
We describe a new class of dark energy (DE) models which behave like cosmological trackers at early times. These models are based on the $alpha$-attractor set of potentials, originally discussed in the context of inflation. The new models allow the c
urrent acceleration of the universe to be reached from a wide class of initial conditions. Prominent examples of this class of models are the potentials $cothvarphi$ and $coshvarphi$. A remarkable feature of this new class of models is that they lead to large enough negative values of the equation of state at the present epoch, consistent with the observations of accelerated expansion of the universe, from a very large initial basin of attraction. They therefore avoid the fine tuning problem which afflicts many models of DE.
In this work, we analyzed the effect of different prescriptions of the IR cutoffs, namely the Hubble horizon cutoff, particle horizon cutoff, Granda and Oliveros horizon cut off, and the Ricci horizon cutoff on the growth rate of clustering for the T
sallis holographic dark energy (THDE) model in an FRW universe devoid of any interactions between the dark Universe. Furthermore, we used the concept of configurational entropy to derive constraints (qualitatively) on the model parameters for the THDE model in each IR cutoff prescription from the fact that the rate of change of configurational entropy hits a minimum at a particular scale factor $a_{DE}$ which indicate precisely the epoch of dark energy domination predicted by the relevant cosmological model as a function of the model parameter(s). By using the current observational constraints on the redshift of transition from a decelerated to an accelerated Universe, we derived constraints on the model parameters appearing in each IR cutoff definition and on the non-additivity parameter $delta$ characterizing the THDE model and report the existence of simple linear dependency between $delta$ and $a_{DE}$ in each IR cutoff setup.
The origin of accelerating expansion of the Universe is one the biggest conundrum of fundamental physics. In this paper we review vacuum energy issues as the origin of accelerating expansion - generally called dark energy - and give an overview of al
ternatives, which a large number of them can be classified as interacting scalar field models. We review properties of these models both as classical field and as quantum condensates in the framework of non-equilibrium quantum field theory. Finally, we review phenomenology of models with the goal of discriminating between them.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
