Correlated mixture between adiabatic and isocurvature fluctuations and recent CMB observations

Andrade, A. P. A.; Wuensche, Carlos Alexandre; Ribeiro, André

doi:10.1103/physrevd.71.043501

Cited by 5 publications

(4 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Constraints from the Boomerang 2003 flight were derived in [206] and from Cosmic Background Imager (CBI) observations in [207]. The WMAP first-year data [208] were used in [7,8,25,43,105,107,157,[209][210][211][212][213][214][215][216][217][218] to constrain various mixtures of adiabatic and isocurvature perturbations in a spatially flat Universe. The focus in [219] was in testing how much the (possible) presence of isocurvature modes affects the determination of the geometry (spatial curvature) of the Universe.…”

Section: Comparison To Older Resultsmentioning

confidence: 99%

Constraints on Scalar and Tensor Perturbations in Phenomenological and Two-Field Inflation Models: Bayesian Evidences for Primordial Isocurvature and Tensor Modes

Väliviita¹,

Савелайнен²,

Talvitie³

et al. 2012

ApJ

View full text Add to dashboard Cite

We constrain cosmological models where the primordial perturbations have both an adiabatic and a (possibly correlated) cold dark matter (CDM) or baryon isocurvature component. We use both a phenomenological approach, where the power spectra of primordial perturbations are parametrized with amplitudes and spectral indices, and a slow-roll two-field inflation approach where slow-roll parameters are used as primary parameters determining the spectral indices and the tensor-to-scalar ratio. In the phenomenological case, with cosmic microwave background (CMB) data, the upper limit to the CDM isocurvature fraction α is 6.4% at k = 0.002 Mpc −1 and 15.4% at k = 0.01 Mpc −1 . At smaller scales (larger k) larger isocurvature fractions are allowed, and therefore large values of the isocurvature spectral index, niso ≈ 2, are formally favored. The median 95% range for the non-adiabatic contribution to the CMB temperature variance is −0.030 < αT < 0.049. Including the supernova (or large-scale structure, LSS) data, these limits become: α < 7.0%, 13.7%, and −0.048 < αT < 0.042 (or α < 10.2%, 16.0%, and −0.071 < αT < 0.024). The CMB constraint on the tensor-to-scalar ratio, r 0.26 at k = 0.01 Mpc −1 , is not affected by the nonadiabatic modes. In the slow-roll two-field inflation approach, the spectral indices are constrained close to 1. This leads to tighter limits on the isocurvature fraction, with the CMB data α < 2.6% at k = 0.01 Mpc −1 , but since the non-adiabatic contribution to the CMB temperature variance comes mostly from larger scales its median 95% range is not much affected, −0.058 < αT < 0.045. Including supernova (or LSS) data, these limits become: α < 3.2% and −0.056 < αT < 0.030 (or α < 3.4% and −0.063 < αT < −0.008). When all spectral indices are close to each other the isocurvature fraction is somewhat degenerate with the tensor-to-scalar ratio. In addition to the generally correlated models, we study also special cases where the adiabatic and isocurvature modes are uncorrelated or fully (anti)correlated. We calculate Bayesian evidences (model probabilities) in 21 different cases for our nonadiabatic models and for the corresponding adiabatic models, and find that in all cases the current data support the pure adiabatic model. 98.80.Cq, 98.70.Vc

show abstract

Section: Comparison To Older Resultsmentioning

confidence: 99%

Constraints on Scalar and Tensor Perturbations in Phenomenological and Two-Field Inflation Models: Bayesian Evidences for Primordial Isocurvature and Tensor Modes

Väliviita¹,

Савелайнен²,

Talvitie³

et al. 2012

ApJ

View full text Add to dashboard Cite

show abstract

“…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

View full text Add to dashboard Cite

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.

show abstract

“…They also allow one to quantify the contribution of the second component. By applying a χ 2 test on recent CMBR observations, the contribution of the isocurvature field was estimated by Andrade, Wuensche & Ribeiro (2005) (hereafter AWR05) as α 0 = 0.0004 ± 0.00030 with 68% confidence limit. In the present work, we also investigate the predictions of scaledependent mixed non-Gaussian cosmological density fields for the peak-peak correlation function.…”

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

View full text Add to dashboard Cite

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.

show abstract

Correlated mixture between adiabatic and isocurvature fluctuations and recent CMB observations

Cited by 5 publications

References 25 publications

Constraints on Scalar and Tensor Perturbations in Phenomenological and Two-Field Inflation Models: Bayesian Evidences for Primordial Isocurvature and Tensor Modes

Constraints on Scalar and Tensor Perturbations in Phenomenological and Two-Field Inflation Models: Bayesian Evidences for Primordial Isocurvature and Tensor Modes

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

Contact Info

Product

Resources

About