Predictions of Mixed Non‐Gaussian Cosmological Density Fields for the Cosmic Microwave Background Radiation

Andrade, A. P. A.; Wuensche, Carlos Alexandre; Ribeiro, Andre Luiz B.

doi:10.1086/381177

Cited by 7 publications

(7 citation statements)

References 39 publications

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“…After the first serious constraints on an uncorrelated mixed model [29], and after ruling out pure CDM isocurvature [30], various mixtures of the adiabatic and isocurvature modes have been tested. In particular, since the release of the Wilkinson Microwave Anisotropy Probe (WMAP) data, observational constraints have been obtained, e.g., by [10,27,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45] for WMAP1 [46], by [47,48,49,50,51,52] for WMAP3 [53] and most recently for WMAP5 [54] by [28], and by [55] in the particular case of axion (uncorrelated, n iso = 1). In [28] it is shown that the CDM isocurvature mode is not required by a combination of current data if flatness is assumed.…”

Section: Introductionmentioning

confidence: 99%

Constraints on primordial isocurvature perturbations and spatial curvature by Bayesian model selection

Väliviita

Giannantonio

2009

Phys. Rev. D

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We present posterior likelihoods and Bayesian model selection analysis for generalized cosmological models where the primordial perturbations include correlated adiabatic and cold dark matter isocurvature components. We perform nested sampling with flat and, for the first time, curved spatial geometries of the Universe, using data from the cosmic microwave background (CMB) anisotropies, the Union supernovae (SN) sample and a combined measurement of the integrated Sachs-Wolfe (ISW) effect. The CMB alone favors a 3% (positively correlated) isocurvature contribution in both the flat and curved cases. The non-adiabatic contribution to the observed CMB temperature variance is 0 < αT < 7% at 98% CL in the curved case. In the flat case, combining the CMB with SN data artificially biases the result towards the pure adiabatic ΛCDM concordance model, whereas in the curved case the favored level of non-adiabaticity stays at 3% level with all combinations of data. However, the ratio of Bayes factors, or ∆ ln(evidence), is more than 5 points in favor of the flat adiabatic ΛCDM model, which suggests that the inclusion of the 5 extra parameters of the curved isocurvature model is not supported by the current data. The results are very sensitive to the second and third acoustic peak regions in the CMB temperature angular power: therefore a careful calibration of these data will be required before drawing decisive conclusions on the nature of primordial perturbations. Finally, we point out that the odds for the flat non-adiabatic model are 1:3 compared to the curved adiabatic model. This may suggest that it is not much less motivated to extend the concordance model with 4 isocurvature degrees of freedom than it is to study the spatially curved adiabatic model, though at the moment the model selection disfavors both of these models.

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Section: Introductionmentioning

confidence: 99%

Constraints on primordial isocurvature perturbations and spatial curvature by Bayesian model selection

Väliviita

Giannantonio

2009

Phys. Rev. D

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“…The effects of such mixed models in the CMBR power spectrum, combining a Gaussian adiabatic field with a second nonGaussian isocurvature fluctuation field to produce a positive skewness density field, was discussed by Andrade et al (2004) (hereafter AWR04). In this approach, they adopted a scaledependent mixture parameter and a power-law initial spectrum to simulate the CMBR temperature and polarization power spectra for a flat Λ-CDM model, generating a large grid of cosmological-parameter combination.…”

Section: The Mixture Modelmentioning

confidence: 99%

High order correction terms for the peak-peak correlation function in nearly-Gaussian models

Andrade

Ribeiro

Wuensche³

2006

A&A

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Context. One possible way to investigate the nature of the primordial power spectrum fluctuations is by investigating the statistical properties of the local maximum in the density fluctuation fields.Aims. In this work we present a study of the mean correlation function, ξ r , and the correlation function for high-amplitude fluctuations (peak-peak correlation) in a slighlty non-Gaussian context. Methods. From the definition of the correlation excess, we computed the Gaussian two-point correlation function and, using an expansion in generalized Hermite polynomials, we estimated the correlation of high-density peaks in a non-Gaussian field with a generic distribution and power spectrum. We also applied the results to a scale-mixed distribution model, which corresponds to a nearly Gaussian model. Results. The results reveal that, even for a small deviation from Gaussianity, we can expect high-density peaks to be much more correlated than in a Gaussian field with the same power spectrum. In addition, the calculations reveal how the amplitude of the peaks in the fluctuation field is related to the existing correlations. Conclusions. Our results may be used as an additional tool for investigating the behavior of the N-point correlation function, to understand how non-Gaussian correlations affect the peak-peak statistics, and extract more information about the statistics of the density field.

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“…A number of realizations of CMBR temperature power spectra were made and the mean temperature fluctuations combining Gaussian, Exponential, Lognormal, Rayleigh, Maxwellian and a Chi-squared distributions was estimated (Andrade et al 2004). The simulations show that the influence of the specific statistics of the second component in the mixed field is not so important as the cross-correlation between the amplitudes of both fields.…”

Section: B the Evolution Of The Mixed Fieldmentioning

confidence: 99%

“…Andrade et al (2004) have suggested a new mixed scenario describing a correlated mixture of two fields, one of them being a dominant Gaussian adiabatic process to which is added a small contribution of an isocurvature field. In a previous work, Ribeiro, Wuensche & Letelier (2000) used such mixed scenario to probe the galaxy cluster abundance evolution in the universe and found that even a very small level of nonGaussianity in the mixed field may introduce significant changes in the cluster abundance rate.…”

Section: Introductionmentioning

confidence: 99%

“…In a previous work, Ribeiro, Wuensche & Letelier (2000) used such mixed scenario to probe the galaxy cluster abundance evolution in the universe and found that even a very small level of nonGaussianity in the mixed field may introduce significant changes in the cluster abundance rate. Andrade, Wuensche and Ribeiro (2004) showed the effects of mixed models in the CMBR power spectrum, combining a Gaussian (adiabatic) field with a second isocurvature field to produce a positive skewness mixed density fluctuation field. This approach adopted a scale dependent mixture parameter and a power-law initial spectrum to simulate the CMBR temperature and polarization power spectra for a flat Λ-CDM model, generating quite a large grid of cosmological parameters combination.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Correlated mixture between adiabatic and isocurvature fluctuations and recent CMB observations

Andrade

Wuensche

Ribeiro³

2005

Phys. Rev. D

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This work presents a reduced χ 2 ν test to search for non-gaussian signals in the CMBR TT power spectrum of recent CMBR data, WMAP, ACBAR and CBI data sets, assuming a mixed density field including adiabatic and isocurvature fluctuations. We assume a skew positive mixed model with adiabatic inflation perturbations plus additional isocurvature perturbations possibly produced by topological defects. The joint probability distribution used in this context is a weighted combination of Gaussian and non-Gaussian random fields. Results from simulations of CMBR temperature for the mixed field show a distinct signature in CMB power spectrum for very small deviations (∼ 0.1%) from a pure Gaussian field, and can be used as a direct test for the nature of primordial fluctuations. A reduced χ 2 ν test applied on the most recent CMBR observations reveals that an isocurvature fluctuations field is not ruled out and indeed permits a very good description for a flat geometry Λ-CDM universe, χ

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Predictions of Mixed Non‐Gaussian Cosmological Density Fields for the Cosmic Microwave Background Radiation

Cited by 7 publications

References 39 publications

Constraints on primordial isocurvature perturbations and spatial curvature by Bayesian model selection

Constraints on primordial isocurvature perturbations and spatial curvature by Bayesian model selection

High order correction terms for the peak-peak correlation function in nearly-Gaussian models

Correlated mixture between adiabatic and isocurvature fluctuations and recent CMB observations

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