Perfect fluids with<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" display="inline" id="mml1" overflow="scroll"><mml:mi>ω</mml:mi><mml:mo>=</mml:mo><mml:mi mathvariant="normal">const</mml:mi></mml:math>as sources of scalar cosmological perturbations

Eingorn, Maxim; Brilenkov, Ruslan

doi:10.1016/j.dark.2017.08.003

Cited by 17 publications

(26 citation statements)

References 49 publications

(96 reference statements)

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“…According to (37), at this evolution stageδρ substantially grows below the characteristic comoving scale k −1 = 2a/(5κρc 2 ) = λ eff /a. This means that, strictly speaking, λ eff (and not λ, as claimed in [6,12], although the values of λ eff and λ are of the same order) defines the size of a spatial domain where cosmic structures may grow. A hypothesis offered in [6] interprets λ as the upper bound for the dimensions of a solitary structure.…”

Section: Effective Screening Length To Rule Them Allmentioning

confidence: 97%

“…On the contrary, in Eq. (3) the inconvenient velocity-dependent source is left unconverted, but Φ is singled out from δε [6,12]:…”

Section: Screening Length In Linear Perturbation Theorymentioning

confidence: 99%

“…This function represents the dominant solution of Eq. (30) from [12], derived specifically forδρ(η, k) with the regard for the cosmological screening. On the contrary, if one obliterated the term ∝ ν in Eq.…”

Section: Screening Length In Linear Perturbation Theorymentioning

confidence: 99%

“…With all due respect, this function does not satisfy Eq. (30) from [12] and is unsuitable unless a κρc 2 /k 2 (this inequality holds true at sufficiently small distances where the cosmological screening does not come into play, so the expressions (37) and (38) coincide with each other).…”

Section: Screening Length In Linear Perturbation Theorymentioning

confidence: 99%

“…Hereinafter this Yukawa-type screening is sometimes called "cosmological" or "cosmic", since it originates from the presence of the cosmological background.Both cosmic screening approaches have been formulated in the framework of the standard ΛCDM (Λ cold dark matter) model, which is consistent with the observational data [8], though it is noteworthy that currently there is tension between the direct local measurement of the Hubble constant and the value of this very constant following from the Planck data on cosmic microwave background temperature and polarization (see, e.g., [9,10,11]). Furthermore, both original papers [6,7] focus on the matter-and Λ-dominated stages of the Universe evolution, so radiation and relativistic neutrinos are disregarded (though the results of [6] have been subsequently generalized to the case of additional perfect fluids with linear and nonlinear equations of state [12,13,14], as well as to the cases of nonzero spatial curvature [15], f (R) gravity [16] and the phantom braneworld model [17]). From the mathematical point of view, the cosmological Yukawa screening inevitably comes into play when the Einstein equation for the gravitational potential (scalar perturbation) is reduced to the Helmholtz equation, which replaces its popular rival of Poisson type.…”

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Duel of cosmological screening lengths

Canay

Eingorn

2020

Physics of the Dark Universe

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Two distinct perturbative approaches have been recently formulated within General Relativity, arguing for the screening of gravity in the ΛCDM Universe. In this paper we compare them and show that the offered screening concepts, each characterized by its own interaction range, can peacefully coexist. Accordingly, we advance a united scheme, determining the gravitational potential at all scales, including regions of nonlinear density contrasts, by means of a simple Helmholtz equation with the effective cosmological screening length. In addition, we claim that cosmic structures may not grow at distances above this Yukawa range and confront its current value with dimensions of the largest known objects in the Universe.As the science rapidly progresses, higher and higher accuracy of observations is achieved. For instance, such a future space mission as Euclid [3,4,5] is designed to probe the Universe expansion with unprecedented precision and impose new restrictions on dark energy, dark matter, and various cosmological parameters. In this connection, the legitimate demand for an advanced theory soars up too. In particular, it is quite natural to expect that Newtonian gravity is modified at large distances and ultimately reconciled with the standard relativistic perturbation theory. By dint of our narration, we aim at sparking interest in two distinct approaches [6,7] relying on General Relativity, which argue that gravity is actually screened, ceasing to be longrange far enough from its every single source. Hereinafter this Yukawa-type screening is sometimes called "cosmological" or "cosmic", since it originates from the presence of the cosmological background.Both cosmic screening approaches have been formulated in the framework of the standard ΛCDM (Λ cold dark matter) model, which is consistent with the observational data [8], though it is noteworthy that currently there is tension between the direct local measurement of the Hubble constant and the value of this very constant following from the Planck data on cosmic microwave background temperature and polarization (see, e.g., [9,10,11]). Furthermore, both original papers [6,7] focus on the matter-and Λ-dominated stages of the Universe evolution, so radiation and relativistic neutrinos are disregarded (though the results of [6] have been subsequently generalized to the case of additional perfect fluids with linear and nonlinear equations of state [12,13,14], as well as to the cases of nonzero spatial curvature [15], f (R) gravity [16] and the phantom braneworld model [17]).From the mathematical point of view, the cosmological Yukawa screening inevitably comes into play when the Einstein equation for the gravitational potential (scalar perturbation) is reduced to the Helmholtz equation, which replaces its popular rival of Poisson type. Meanwhile, the underlying physical reasons and resulting screening ranges are different in [6] and [7]. The scheme of [6] (see additionally [18,19]) is rooted in the so-called discrete cosmology studying how discrete gravitating mass...

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Section: Effective Screening Length To Rule Them Allmentioning

confidence: 97%

“…On the contrary, in Eq. (3) the inconvenient velocity-dependent source is left unconverted, but Φ is singled out from δε [6,12]:…”

Section: Screening Length In Linear Perturbation Theorymentioning

confidence: 99%

Section: Screening Length In Linear Perturbation Theorymentioning

confidence: 99%

Section: Screening Length In Linear Perturbation Theorymentioning

confidence: 99%

mentioning

confidence: 99%

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Duel of cosmological screening lengths

Canay

Eingorn

2020

Physics of the Dark Universe

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Analytic expressions for the second-order scalar perturbations in theΛCDM Universe within the cosmic screening approach

Eingorn

Guran

Zhuk

2019

Physics of the Dark Universe

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We study the second-order scalar perturbations in the conventional ΛCDM Universe within the cosmic screening approach. The analytic expressions for both the velocity-independent and velocity-dependent second-order scalar perturbations are derived. We demonstrate how the Yukawa screening effect, which is inherent in the first-order metric corrections, manifests itself in the second-order ones. It is shown that the obtained formulas for the second-order perturbations are reduced to the known post-Newtonian expressions at distances much smaller than the Yukawa screening length. In the era of precision cosmology, these analytic formulas play an important role since the second-order metric corrections may affect the interpretation of observational data (e.g., the luminosity-redshift relation, gravitational lensing, baryon acoustic oscillations). IntroductionAccording to the cosmological principle [1, 2], our Universe is isotropic and homogeneous at large enough scales. This follows from the natural assumption that the laws of physics should be the same wherever in the Universe we are. Starting from a certain scale, the distribution of inhomogeneities (e.g., galaxies and groups of galaxies) should be statistically homogeneous. As a result, such statistically homogeneous Universe has the Friedmann-Lemaître-Robertson-Walker (FLRW) metric, and its dynamics is described by the Friedmann equations. This is the zero-order/background approach. Obviously, inhomogeneities disturb this background resulting in first-and higher-order perturbations. They play a crucial role in the investigation of the large scale structure formation. Evidently (by definition!), the average values of the first-order perturbations should be equal to zero (see, e.g., [3]). On the other hand, the average values of the second-order perturbations are different from zero and can affect the background spacetime and matter. This effect is called backreaction (see, e.g., [4,5,6,7,8,9] and references therein). It is important to determine how strong the backreaction is and to what extent we may use the standard FLRW metric as a background one. As an example, the backreaction may affect the baryon acoustic oscillations [5,10]. The second-order perturbations also contribute to the luminosity-redshift relation [11] and gravitational lensing [12,13].Within the cosmic screening approach, the theory of the first-order perturbations was developed in the papers [14,15,16,17,18]. In its framework, inhomogeneities in the Universe (e.g., galaxies and their groups) are considered as point-like gravitating masses. These masses disturb the background spacetime and matter. For example, the energy density fluctuation reads δε ≈ (c 2 /a 3 )δρ + (3ρc 2 /a 3 )Φ, where c denotes the speed of light, a is the scale factor of the Universe, and we singled out the gravitational potential Φ. Consequently, the

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