Cosmic Background Anisotropies in Cold Dark Matter Cosmology

Sugiyama, Naoshi

doi:10.1086/192220

Cited by 432 publications

(442 citation statements)

References 21 publications

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“…In these expressions, Γ is Sugiyama's shape parameter [50]. Given an initial spectrum (e.g., Harrison-Zeldovich), the power spectrum today can be obtained by integrating the coupled system of equations for the evolution of the Universe and the Boltzmann equations.…”

Section: Power Spectrum and Transfer Functionmentioning

confidence: 99%

Density perturbations for a running cosmological constant

Fabris

Shapiro

Solà

2007

J. Cosmol. Astropart. Phys.

152

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The dynamics of density and metric perturbations is investigated for the previously developed model where the decay of the vacuum energy into matter (or vice versa) is due to the renormalization group (RG) running of the cosmological constant (CC) term. The evolution of the CC depends on the single parameter ν, which characterizes the running of the CC produced by the quantum effects of matter fields of the unknown high energy theory below the Planck scale. The sign of ν indicates whether bosons or fermions dominate in the running. The spectrum of perturbations is computed assuming an adiabatic regime and an isotropic stress tensor. Moreover, the perturbations of the CC term are generated from the simplest covariant form suggested by the RG model under consideration. The corresponding numerical analysis shows that for ν > 0 there is a depletion of the matter power spectrum at low scales (large wave numbers) as compared to the standard ΛCDM model, whereas for ν < 0 there is an excess of power at low scales. We find that the LSS data rule out the range |ν| > 10 −4 while the values |ν| ≤ 10 −6 look perfectly acceptable. For ν < 0 the excess of power at low scales grows rapidly and the bound is more severe. From the particle physics viewpoint, the values |ν| ≃ 10 −6 correspond to the "desert" in the mass spectrum above the GUT scale M X ∼ 10 16 GeV . Our results are consistent with those obtained in other dynamical models admitting an interaction between dark matter and dark energy. We find that the matter power spectrum analysis is a highly efficient method to discover a possible scale dependence of the vacuum energy.

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Section: Power Spectrum and Transfer Functionmentioning

confidence: 99%

Density perturbations for a running cosmological constant

Fabris

Shapiro

Solà

2007

J. Cosmol. Astropart. Phys.

152

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“…The three-dimensional power spectrum of matter density fluctuations P δδ is further specified by the primordial slope n s = 1, the normalization σ 8 = 0.9 and the shape parameter Γ, calculated according to Sugiyama (1995) with Ω b = 0.05. Using the transfer function of Eisenstein & Hu (1998) (without baryonic wiggles), the non-linear power spectrum is computed by means of the fit formula of Peacock & Dodds (1996).…”

Section: Lensing Power Spectramentioning

confidence: 99%

The removal of shear-ellipticity correlations from the cosmic shear signal

Joachimi¹,

Schneider²

2009

A&A

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Aims. Cosmic shear, the gravitational lensing on cosmological scales, is regarded as one of the most powerful probes for revealing the properties of dark matter and dark energy. To fully utilize its potential, one has to be able to control systematic effects down to below the level of the statistical parameter errors. Particularly worrisome in this respect is the intrinsic alignment of galaxies, causing considerable parameter biases via correlations between the intrinsic ellipticities of galaxies and the gravitational shear, which mimic lensing. Since our understanding of the underlying processes of intrinsic alignment is still poor, purely geometrical methods are required to control this systematic. In an earlier work we proposed a nulling technique that downweights this systematic, only making use of its well-known redshift dependence. We assess the practicability of nulling, given realistic conditions on photometric redshift information. Methods. For several simplified intrinsic alignment models and a wide range of photometric redshift characteristics, we calculate an average bias before and after nulling. Modifications of the technique are introduced to optimize the bias removal and minimize the information loss by nulling. We demonstrate that one of the presented versions of nulling is close to optimal in terms of bias removal, given the high quality of photometric redshifts. Although the nulling weights depend on cosmology, being composed of comoving distances, we show that the technique is robust against an incorrect choice of cosmological parameters when calculating the weights. Moreover, general aspects such as the behavior of the Fisher matrix under parameter-dependent transformations and the range of validity of the bias formalism are discussed in an appendix. Results. Given excellent photometric redshift information, i.e. at least 10 bins with a dispersion σ ph 0.03, a negligible fraction of catastrophic outliers, and precise knowledge about the bin-wise redshift distributions as characterized by a scatter of 0.001 or less on the median redshifts, one version of nulling is capable of reducing the shear-intrinsic ellipticity contamination by at least a factor of 100. Alternatively, we describe a robust nulling variant which suppresses the systematic signal by about 10 for a very broad range of photometric redshift configurations, provided basic information about σ ph in each of 10 photometric redshift bins is available. Irrespective of the photometric redshift quality, a loss of statistical power is inherent to nulling, which amounts to a decrease of the order 50% in terms of our figure of merit under conservative assumptions.

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“…The sCDM transfer function is given approximatively by the following numerical fit [40] T (k) = ln(1 + 2.34q) 2.34q 1 + 3.89q + (16.1q) 2 + (5.46q) 3 + (6.71q…”

Section: Calculation Of the Power Spectrummentioning

confidence: 99%

Single field inflation and non-Gaussianity

2002

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We study non-Gaussian signatures on the cosmic microwave background (CMB) radiation predicted within inflationary models with non-vacuum initial states for cosmological perturbations. The model incorporates a privileged scale, which implies the existence of a feature in the primordial power spectrum. This broken-scale-invariant model predicts a vanishing three-point correlation function for the CMB temperature anisotropies (or any other odd-numbered-point correlation function) whilst an intrinsic non-Gaussian signature arises for any even-numbered-point correlation function. We thus focus on the first non-vanishing moment, the CMB four-point function at zero lag, namely the kurtosis, and compute its expected value for different locations of the primordial feature in the spectrum, as suggested in the literature to conform to observations of large scale structure. The excess kurtosis is found to be negative and the signal to noise ratio for the dimensionless excess kurtosis parameter is equal to |S/N | ≃ 4 × 10 −4 , almost independently of the free parameters of the model. This signature turns out to be undetectable. We conclude that, subject to current tests, Gaussianity is a generic property of single field inflationary models. The only uncertainty concerning this prediction is that the effect of back-reaction has not yet been properly incorporated. The implications for the trans-Planckian problem of inflation are also briefly discussed.

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Cosmic Background Anisotropies in Cold Dark Matter Cosmology

Cited by 432 publications

References 21 publications

Density perturbations for a running cosmological constant

Density perturbations for a running cosmological constant

The removal of shear-ellipticity correlations from the cosmic shear signal

Single field inflation and non-Gaussianity

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