On the least action principle in cosmology

Nusser, Adi; Branchini, E.

doi:10.1046/j.1365-8711.2000.03261.x

Cited by 65 publications

(72 citation statements)

References 41 publications

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“…The reason for this is the strict criteria we have applied in selecting the "LG observer" in the mock catalogs, aimed at matching the quietness and moderate density environment of the observed LG. Removing these selection criteria boosts the error to > ∼ 300km s −1 , consistent with previous studies (Nusser & Branchini 2000). Nonlinear dynamical reconstruction methods can potentially reduce LG actors + four external groups.…”

Section: Cosmological Constraints On 20-100 Mpc Scalessupporting

confidence: 87%

Dynamics of The Tranquil Cosmic Web

Nusser¹

2014

Proc. IAU

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Abstract. The phase space distribution of matter out to ∼ 100Mpc is probed by two types of observational data: galaxy redshift surveys and peculiar motions of galaxies. Important information on the process of structure formation and deviations from standard gravity have been extracted from the accumulating data. The remarkably simple Zel'dovich approximation is the basis for much of our insight into the dynamics of structure formation and the development of data analyses methods. Progress in the methodology and some recent results is reviewed.

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Section: Cosmological Constraints On 20-100 Mpc Scalessupporting

confidence: 87%

Dynamics of The Tranquil Cosmic Web

Nusser¹

2014

Proc. IAU

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“…The bias produces an undesired smoothing of density field along the radial direction. The smoothing width (in km s −1 ) is equal to the rms random error in the velocities ∼200–300 km s −1 (Branchini, Eldar & Nusser 2002; Nusser & Branchini 2000). Therefore, the bias is more pronounced in non‐linear methods which aim at probing small scales.…”

Section: Discussionmentioning

confidence: 99%

Local gravity versus local velocity: solutions for β and non-linear bias

Davis¹,

Nusser²,

Masters³

et al. 2011

Monthly Notices of the Royal Astronomical Society

167

143

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We perform a reconstruction of the cosmological large‐scale flows in the nearby Universe using two complementary observational sets. The first, the SFI++ sample of Tully–Fisher (TF) measurements of galaxies, provides a direct probe of the flows. The second, the whole sky distribution of galaxies in the 2MASS (Two Micron All Sky Survey) redshift survey (2MRS), yields a prediction of the flows given the cosmological density parameter, Ω, and a biasing relation between mass and galaxies. We aim at an unbiased comparison between the peculiar velocity fields extracted from the two data sets and its implication on the cosmological parameters and the biasing relation. We expand the fields in a set of orthonormal basis functions, each representing a plausible realization of a cosmological velocity field smoothed in such a way as to give a nearly constant error on the derived SFI++ velocities. The statistical analysis is done on the coefficients of the modal expansion of the fields by means of the basis functions. Our analysis completely avoids the strong error covariance in the smoothed TF velocities by the use of orthonormal basis functions and employs elaborate mock data sets to extensively calibrate the errors in 2MRS predicted velocities. We relate the 2MRS galaxy distribution to the mass density field by a linear bias factor, b, and include a luminosity‐dependent, ∝Lα, galaxy weighting. We assess the agreement between the fields as a function of α and β=f(Ω)/b, where f is the growth factor of linear perturbations. The agreement is excellent with a reasonable χ2 per degree of freedom. For α= 0, we derive 0.28 < β < 0.37 and 0.24 < β < 0.43, respectively, at the 68.3 per cent and 95.4 per cent confidence levels (CLs). For β= 0.33, we get α < 0.25 and α < 0.5, respectively, at the 68.3 per cent and 95.4 per cent CLs. We set a constraint on the fluctuation normalization, finding σ8= 0.66 ± 0.10, which is only 1.5σ deviant from Wilkinson Microwave Anisotropy Probe (WMAP) results. It is remarkable that σ8 determined from this local cosmological test is close to the value derived from the cosmic microwave background, an indication of the precision of the standard model.

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“…This point remains to be further studied and quantified. The linear component can be accurately traced back in time on large scales ≳5 h −1 Mpc from Eulerian to Lagrangian coordinates yielding fields that are more correlated with the initial conditions than the Eulerian representation. This implies that Eulerian grid‐based methods (as opposed to particle‐based methods; see Peebles ; Nusser & Branchini ; Branchini, Eldar & Nusser ; Eisenstein et al ; Lavaux et al ) could be used to recover BAO or other physical signals. We have demonstrated that one can compute the non‐linear component from the linear component with LPT.…”

Section: Discussionmentioning

confidence: 99%

Linearization with cosmological perturbation theory

Kitaura¹,

Angulo

2012

Monthly Notices of the Royal Astronomical Society

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We propose a new method to linearize cosmological mass density fields using higher order Lagrangian perturbation theory (LPT). We demonstrate that a given density field can be expressed as the sum of a linear and a non‐linear component which are tightly coupled to each other by the tidal field tensor within the LPT framework. The linear component corresponds to the initial density field in Eulerian coordinates, and its mean relation with the total field can be approximated by a logarithm (giving theoretical support to recent attempts to find such a component). We also propose to use a combination of the linearization method and the continuity equation to find the mapping between Eulerian and Lagrangian coordinates. In addition, we note that this method opens the possibility of using directly higher order LPT on non‐linear fields. We test our linearization scheme by applying it to the z ∼ 0.5 density field from an N‐body simulation. We find that the linearized version of the full density field can be successfully recovered on ≳5 h−1 Mpc, reducing the skewness and kurtosis of the distribution by about one and two orders of magnitude, respectively. This component can also be successfully traced back in time, converging towards the initial unevolved density field at z ∼ 100. We anticipate a number of applications of our results, from predicting velocity fields to estimates of the initial conditions of the Universe, passing by improved constraints on cosmological parameters derived from galaxy clustering via reconstruction methods.

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On the least action principle in cosmology

Cited by 65 publications

References 41 publications

Dynamics of The Tranquil Cosmic Web

Dynamics of The Tranquil Cosmic Web

Local gravity versus local velocity: solutions for β and non-linear bias

Linearization with cosmological perturbation theory

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