Testing ΛCDM cosmology at turnaround:<i>where</i>to look for violations of the bound?

Tanoglidis, Dimitrios; Pavlidou, V.; Tomaras, T.N.

doi:10.1088/1475-7516/2015/12/060

Cited by 26 publications

(37 citation statements)

References 35 publications

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“…(20) is relevant to study the effect of the Brans-Dicke field on the maximum turn around radius [24][25][26] of cosmic structures. In its region of validity one may insert (20) into Eq.…”

Section: Spherical Star Solutionsmentioning

confidence: 99%

Brans-Dicke Theory withΛ>0: Black Holes and Large Scale Structures

et al. 2015

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A step-by-step approach is followed to study cosmic structures in the context of Brans-Dicke theory with positive cosmological constant Λ and parameter ω. First, it is shown that regular stationary black-hole solutions not only have constant Brans-Dicke field φ, but can exist only for ω = ∞, which forces the theory to coincide with the General Relativity. Generalizations of the theory in order to evade this black-hole no-hair theorem are presented. It is also shown that in the absence of a stationary cosmological event horizon in the asymptotic region, a stationary black hole horizon can support a non-trivial Brans-Dicke hair. Even more importantly, it is shown next, that the presence of a stationary cosmological event horizon rules out any regular stationary solution, appropriate for the description of a star. Thus, to describe a star one has to assume that there is no such stationary horizon in the faraway asymptotic region. Under this implicit assumption generic spherical cosmic structures are studied perturbatively and is shown that only for ω > 0 or ω −5 their predicted maximum sizes are consistent with observations. We also point out how, many of the conclusions of this work differ qualitatively from the Λ = 0 spacetimes.

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“…(20) is relevant to study the effect of the Brans-Dicke field on the maximum turn around radius [24][25][26] of cosmic structures. In its region of validity one may insert (20) into Eq.…”

Section: Spherical Star Solutionsmentioning

confidence: 99%

Brans-Dicke Theory withΛ>0: Black Holes and Large Scale Structures

et al. 2015

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“…Focusing on R t defined in this way, we have studied the properties of turnaround in the context of ΛCDM and in the HS model [30]. Our results show that the density contrast at the turnaround moment, δ t , can decrease by 18%, and the turnaround radius can increase by 6.4%, at redshift z = 0 for a mass of 10 13 h −1 M , with the MG parameter f R0 = 10 −6 (these are, respectively, the optimal scale of mass for comparing R t measurements [31], and the weakest value of the modified gravity parameter considered in Ref. [30]).…”

Section: Introductionmentioning

confidence: 78%

“…We focus on the mass 10 13 h −1 M (galaxy groups) because it seems well suited to study the effects on the turnaround radius [21]: in fact, tests involving the turnaround are more sensitive around small structures, where the effects of MG are enhanced. On the other hand, it is also important to consider structures whose turnarounds can be estimated with good accuracy -which is again the case for small galaxy groups [21]. For the plots of Fig.…”

Section: Ratio Between the Turnaround Radius And Virial Radiusmentioning

confidence: 99%

Relation between the turnaround radius and virial mass in f(R) model

Lopes¹,

Voivodic²,

Abramo³

et al. 2019

J. Cosmol. Astropart. Phys.

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We investigate the relationship between the turnaround radius R t and the virial mass M v of cosmic structures in the context of ΛCDM model and in an f (R) model of modified gravity -namely, the Hu-Sawicki model. The turnaround radius is the distance from the center of the cosmic structure to the shell that is detaching from the Hubble flow at a given time, while the virial mass is defined, for this work, as the mass enclosed within the volume where the density is 200 times the background density. We employ a new approach by considering that, on average, gravitationally bound astrophysical systems (e.g., galaxies, groups and clusters of galaxies) follow, in their innermost region, a Navarro-Frenk-White density profile, while beyond the virial radius (R v ) the profile is well approximated by the 2-halo term of the matter correlation function. By combining these two properties together with the information drawn from solving the spherical collapse for the structures, we are able to connect two observables that can be readily measured in cosmic structures: the turnaround radius and the virial mass. In particular, we show that, in ΛCDM, the turnaround mass at z = 0 is related to the virial mass of that same structure by M t 3.07 M v , while in terms of the radii we have that R t 3.7 R v (for virial masses of 10 13 h −1 M ). In the f (R) model, on the other hand, we have M t 3.43 M v and R t 4.1 R v , for |f R0 | = 10 −6 and the same mass scale. Therefore, the difference between ΛCDM and f (R) in terms of these observable relations is of order ∼ 10−20% even for a relatively mild strength of the modification of gravity (|f R0 | = 10 −6 ). For the turnaround radius itself we find a difference of ∼ 9% between the weakly modification in gravity considered in this work (|f R0 | = 10 −6 ) and ΛCDM for a mass of 10 13 h −1 M . Once observations allow precisions of this order or better in measurements of the turnaround R t , as well as the virial mass M v (and/or the virial radius R v ), these quantities will become powerful tests of modified gravity.

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“…is tiny compared to the inverse of the Planck length squared, it is natural to expect that its effect would be observable at large space-time scales only, as for instance imprinted in the light coming from some high redshift supernovae or in the data for the early universe. However, a novel potential local check of the dark energy was proposed recently [4][5][6], pertaining to the stability of large scale structures. The idea is simple, based on the observation that the maximum size of an e.g.…”

Section: Introduction and Overviewmentioning

confidence: 99%

“…Given that the process of virialization of a structure typically enhances any non-sphericity in its initial profile, a spherical model for a structure is more appropriate when it is away from virialization. Furthermore, it was shown using the Press-Schechter mass function in [6,10] that there exists a transitional mass scale ∼10 13 M , above which the structures are not virialized today. Thus, in order to challenge a dark energy model using the maximum size versus mass criterion, it is most effective to look into structures which lie above that transitional mass scale.…”

Section: Introduction and Overviewmentioning

confidence: 99%

Cosmic structure sizes in generic dark energy models

Bhattacharya

Tomaras

2017

Eur. Phys. J. C

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The maximum allowable size of a spherical cosmic structure as a function of its mass is determined by the maximum turn around radius R TA,max , the distance from its center where the attraction on a radial test particle due to the spherical mass is balanced with the repulsion due to the ambient dark energy. In this work, we extend the existing results in several directions. (a) We first show that, for w = −1, the expression for R TA,max found earlier, using the cosmological perturbation theory, can be derived using a static geometry as well. (b) In the generic dark energy model with arbitrary time dependent state parameter w(t), taking into account the effect of inhomogeneities upon the dark energy as well, it is shown that the data constrain w(t = today) > −2.3. (c) We address the quintessence and the generalized Chaplygin gas models, both of which are shown to predict structure sizes consistent with observations.

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Testing ΛCDM cosmology at turnaround:whereto look for violations of the bound?

Cited by 26 publications

References 35 publications

Brans-Dicke Theory withΛ>0: Black Holes and Large Scale Structures

Brans-Dicke Theory withΛ>0: Black Holes and Large Scale Structures

Relation between the turnaround radius and virial mass in f(R) model

Cosmic structure sizes in generic dark energy models

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