<i>N</i>-body simulations of<i>γ</i>gravity

Santos, Marcelo V. dos; Winther, Hans A.; Mota, David F.; Waga, I.

doi:10.1051/0004-6361/201527645

Cited by 10 publications

(12 citation statements)

References 67 publications

(64 reference statements)

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“…[3]) that cosmological kinematical tests (those that depend only on the background evolution) alone cannot distinguish between the standard cosmological constant model (ΛCDM) and any viable f (R) gravity theory. Indeed, one of the strongest constraints comes from the growth of perturbations in the nonlinear regime [4,5]. In the linear regime, on the other hand, only weak constraints are obtained [6].…”

Section: Introductionmentioning

confidence: 99%

Calculation of the critical overdensity in the spherical-collapse approximation

2017

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Critical overdensity δc is a key concept in estimating the number count of halos for different redshift and halo-mass bins, and therefore, it is a powerful tool to compare cosmological models to observations. There are currently two different prescriptions in the literature for its calculation, namely, the differential-radius and the constant-infinity methods. In this work we show that the latter yields precise results only if we are careful in the definition of the so-called numerical infinities. Although the subtleties we point out are crucial ingredients for an accurate determination of δc both in general relativity and in any other gravity theory, we focus on f (R) modified-gravity models in the metric approach; in particular, we use the so-called large (F = 1/3) and small-field (F = 0) limits. For both of them, we calculate the relative errors (between our method and the others) in the critical density δc, in the comoving number density of halos per logarithmic mass interval n ln M and in the number of clusters at a given redshift in a given mass bin N bin , as functions of the redshift. We have also derived an analytical expression for the density contrast in the linear regime as a function of the collapse redshift zc and Ωm0 for any F .

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Section: Introductionmentioning

confidence: 99%

Calculation of the critical overdensity in the spherical-collapse approximation

2017

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“…The thermal transport properties of the PE/BNN nanocomposite lms were evaluated in terms of in-plane thermal diffusivity (TD) measurements on a commercially acquired instrument based on the modied Angstrom's method. 17,18 The TD is correlated with thermal conductivity (TC) in the following relationship:…”

Section: Resultsmentioning

confidence: 99%

Dispersion of high-quality boron nitride nanosheets in polyethylene for nanocomposites of superior thermal transport properties

et al. 2020

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High-quality boron nitride nanosheets (BNNs) characterized by large aspect ratios and less defective surfaces and structures are in demand for thermal management and other uses that exploit the uniquely advantageous properties of boron nitride, such as being highly thermally conductive yet electrically insulating and extreme chemical and thermal stabilities. In this study, an ammonia-assisted exfoliation processing method was developed and applied to the preparation of high-quality BNNs. As a demonstration of the excellent potential of these nanomaterials, the BNNs were dispersed in polyethylene polymers for nanocomposite films of superior thermal transport performance at levels significantly beyond the state of the art in the literature. Effects of crosslinking in the nanocomposite film structure on thermal transport were also explored and favorable outcomes were achieved. Fig. 6 SEM images for the crosslinked PE/BNN film with a 30 wt% BNN loading. (A) The film surface; (B) the fractured edge from mechanically ripping apart the film; and (C & D) fractured cross-sections from breaking the film at liquid nitrogen temperature.

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“…It is well known that f (R) viable models can not currently be distinguished from GR's ΛCDM at the background level [26]. Further, in these models, both f R (z) ∼ 0 and H ∼ H ΛCDM above a certain redshift.…”

Section: Gravitational Wave Propagation In Alternative Theories Of Gr...mentioning

confidence: 99%

Gravitational wave propagation in $f(R)$ models: New parametrizations and observational constraints

Matos,

Calvão,

Waga

2021

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Modified gravity (MG) theories predict, in general, that the ratio of gravitational wave (GW) to electromagnetic (EM) luminosity distances, Ξ, differs from its general relativity (GR) value of unity at cosmological scales, thus providing another perturbative probe to MG. In this paper, we introduce new phenomenological parametrizations for both the Friedmann-Lemaître-Robertson-Walker (FLRW) background evolution of f (R) models, via the dark energy equation of state parameter, wDE, and for Ξ in this class of theories. We simulate a mock dataset for the Einstein Telescope (ET) of 1000 GW signals from binary neutron star (BNS) mergers and redshift information from their EM counterpart, exploring the consequent constraints on the relevant gravitational, cosmological and phenomenological parameters. As a model of particular interest, we take γ-gravity theory and investigate whether it could be distinguished from GR's ΛCDM model. We then combine our results with actual data from type Ia supernovae (SNIa) and combined baryon acoustic oscillations (BAO) and cosmic microwave background (CMB) observations. Additionally, we also investigate the potential bounds to fR0 for any viable f (R) whose background evolution is indistinguishable from the standard model of cosmology above a certain redshift, showing that, for a ΛCDM fiducial model, ET data would provide |fR0| < 10 −2 at a 95% level. We conclude altogether that probing the redshift evolution of the GW luminosity distance from detections of the ET in its first running decade will not substantially help constraining f (R) theories of gravity.

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N-body simulations ofγgravity

Cited by 10 publications

References 67 publications

Calculation of the critical overdensity in the spherical-collapse approximation

Calculation of the critical overdensity in the spherical-collapse approximation

Dispersion of high-quality boron nitride nanosheets in polyethylene for nanocomposites of superior thermal transport properties

Gravitational wave propagation in $f(R)$ models: New parametrizations and observational constraints

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