Growth of spherical overdensities in scalar–tensor cosmologies

Nazari-Pooya, N.; Malekjani, M.; Pace, Francesco; Jassur, D. M. Z.

doi:10.1093/mnras/stw582

Cited by 26 publications

(25 citation statements)

References 97 publications

(157 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This equation has been used to study the dark sector phenomenology in a number of works, see e.g. [47] for f (R) gravity and [29,106,107] for other classes of Horndeski theories. Here we present the redshift evolution of the modified gravity parameters in Horndeski theories.…”

Section: The Time Evolution Of the Modified Gravity Parametersmentioning

confidence: 99%

Dark sector evolution in Horndeski models

Pace

Battye

Bolliet

et al. 2019

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

We use the Equation of State (EoS) approach to study the evolution of the dark sector in Horndeski models, the most general scalar-tensor theories with second order equations of motion. By including the effects of the dark sector into our code EoS_class, we demonstrate the numerical stability of the formalism and excellent agreement with results from other publicly available codes for a range of parameters describing the evolution of the function characterising the perturbations for Horndeski models, α x , with x = {K, B, M, T}. After demonstrating that on sub-horizon scales (k 10 −3 Mpc −1 at z = 0) velocity perturbations in both the matter and the dark sector are typically subdominant with respect to density perturbations in the equation of state for perturbations, we find an attractor solution for the dark sector gauge-invariant density perturbation ∆ ds . Using this result, we provide simplified expressions for the equation-of-state functions: the dark sector entropy perturbations w ds Γ ds and anisotropic stress w ds Π ds . From this we derive a growth factor-like equation for both matter and dark sector and are able to capture the relevant physics for several observables with great accuracy. We finally present new analytical expressions for the well-known modified gravity phenomenological functions µ, η and Σ for a generic Horndeski model as functions of α x . We show that on small scales they reproduce expressions presented in previous works, but on large scales, we find differences with respect to other works.

show abstract

Section: The Time Evolution Of the Modified Gravity Parametersmentioning

confidence: 99%

Dark sector evolution in Horndeski models

Pace

Battye

Bolliet

et al. 2019

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

show abstract

“…We focus our analysis at sub-horizon scales, where the results of Pseudo Newtonian dynamics are well consistent with those of General Relativity (GR) paradigm (see Abramo et al 2007). In this context, two different scenarios have been studied in literature (Armendariz-Picon et al 1999;Garriga & Mukhanov 1999;Armendariz-Picon et al 2000;Erickson et al 2002;Bean & Doré 2004;Hu & Scranton 2004;Abramo et al 2007Abramo et al , 2008Bean & Doré Bal;Abramo et al 2009;Basilakos et al 2009a;de Putter et al 2010;Pace et al 2010;Akhoury et al 2011;Sapone & Majerotto 2012;Pace et al 2012;Batista & Pace 2013;Dossett & Ishak 2013;Batista 2014;Basse et al 2014;Pace et al 2014b,a,c;Malekjani et al 2015;Naderi et al 2015;Mehrabi et al 2015a,b,c;Nazari-Pooya et al 2016;Malekjani et al 2017). In the first scenario the DE component is homogeneous and only the corresponding non-relativistic matter is allowed to clump, while in the second scenario the whole system clusters (both matter and DE).…”

Section: Growth Of Perturbationsmentioning

confidence: 99%

Model selection and constraints from holographic dark energy scenarios

Akhlaghi

Malekjani

Basilakos

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

In this study we combine the expansion and the growth data in order to investigate the ability of the three most popular holographic dark energy models, namely event future horizon, Ricci scale and Granda-Oliveros IR cutoffs, to fit the data. Using a standard χ 2 minimization method we place tight constraints on the free parameters of the models. Based on the values of the Akaike and Bayesian information criteria we find that two out of three holographic dark energy models are disfavored by the data, because they predict a non-negligible amount of dark energy density at early enough times. Although the growth rate data are relatively consistent with the holographic dark energy models which are based on Ricci scale and Granda-Oliveros IR cutoffs, the combined analysis provides strong indications against these models. Finally, we find that the model for which the holographic dark energy is related with the future horizon is consistent with the combined observational data.

show abstract

“…where it has been used (155). For more details about the density linear perturbations see [46][47][48].…”

Section: Sub-horizon Approximation In St and F (R) Theories Under Conmentioning

confidence: 99%

Equivalence between Scalar-Tensor theories and f(R)-gravity: from the action to cosmological perturbations

Joel

Castañeda

2020

J. Phys. Commun.

View full text Add to dashboard Cite

In this paper we calculate the field equations for Scalar-Tensor from a variational principle, taking into account the Gibbons-York-Hawking type boundary term. We do the same for the theories f (R), following (Guarnizo (2010), Gen. Rel. Grav. 42, 2713-2728. Then, we review the equivalences between both theories in the metric formalism. Thus, starting from the perturbations for Scalar-Tensor theories, we find the perturbations for f (R) gravity under the equivalences. Working with two specific models of f (R), we explore the equivalences between the theories under conformal-Newtonian gauge. Further, we show the perturbations for both theories under the sub-horizon approach. IntroductionRecent observations of the CMB show that the Universe is in accelerated expansion [1,2]. The broadly used model is the Λ-Cold-Dark-Matter (ΛCDM). However, this model introduces an exotic term of energy, called Dark Energy (DE), associated to the cosmological constant term Λ. Assuming that the theory of general relativity (GR) is not entirely correct at cosmological scales, it is possible that a cosmological constant term is not necessary to explain the accelerated expansion of the Universe. The alternative theories to the Einstein's proposal are known as modified gravity theories (MG). One set of these theories is known as Scalar-Tensor gravity theories (ST) [3][4][5], where the gravitational action in these theories, in addition to the metric, to contain a scalar field which intervenes in the generation of the space-time curvature, associated to the metric. This scalar field is not directly coupled to the matter and, therefore, the matter responds only to the metric. It should be noted that the Brans-Dicke theory (BD), [6] proposed by C.H. Brans y R.H. Dicke in 1961, is a particular case of theories ST, where the parameter ω(f) is independent of the scalar field.Another type of generalization to GR are the theories of gravity f (R) [7][8][9], where the lagrangian of Einstein-Hilbert is generalized, replacing the scalar curvature R by a more general function of it, f (R). The gravitational field in this theory is represented by the metric like GR does.The equivalence between theories ST and f (R) has been studied e.g., in [10][11][12][13][14][15]. It is, starting from the ST action, without the kinetic term of the scalar field, we arrive at the action of the gravity theories f (R). In this paper, in addition to the above, we show these equivalences for the field equations, the Friedmann equations of the homogeneous and isotropic universe and the Friedmann's perturbations in any gauge. Further, we show two specific examples of theories f (R) under the conformal-Newtonian gauge.The paper is organized as following: in the section 2 we get the field equations for RG, ST and f (R) theories starting from the variational principle, taking into account the Gibbons-York-Hawking (GYH) boundary term type, for every of the above theories. It is found that the consideration to obtain the field equations for ST, under the equivalence of the theor...

show abstract

Growth of spherical overdensities in scalar–tensor cosmologies

Cited by 26 publications

References 97 publications

Dark sector evolution in Horndeski models

Dark sector evolution in Horndeski models

Model selection and constraints from holographic dark energy scenarios

Equivalence between Scalar-Tensor theories and f(R)-gravity: from the action to cosmological perturbations

Contact Info

Product

Resources

About