Weighing neutrinos in the presence of a running primordial spectral index

Feng, Baojie; Xia, Jun-Qing; Yokoyama, J.; Zhang, Xinmin; Zhao, Gong-Bo

doi:10.1088/1475-7516/2006/12/011

Cited by 13 publications

(16 citation statements)

References 37 publications

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“…), which is consistent with the recent results from WMAP5 group [8,9]. However, there are degeneracies between the neutrino mass and other cosmological parameters, such as the EoS parameters of dark energy [45] and the running of spectral index [46]. Due to the degeneracy among dark energy parameters and the neutrino mass [2,45,47], in the framework of dynamical dark energy models, the limit on the neutrino mass can be relaxed to m ν < 0.974 eV (95% C.L.)…”

Section: Neutrino Masssupporting

confidence: 91%

Determining cosmological parameters with the latest observational data

Xia

Zhao

et al. 2008

Phys. Rev. D

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In this paper, we combine the latest observational data, including the WMAP five-year data (WMAP5), BOOMERanG, CBI, VSA, ACBAR, as well as the Baryon Acoustic Oscillations (BAO) and Type Ia Supernoave (SN) "Union" compilation (307 sample), and use the Markov Chain Monte Carlo method to determine the cosmological parameters, such as the equation-of-state (EoS) of dark energy, the curvature of universe, the total neutrino mass and the parameters associated with the power spectrum of primordial fluctuations. Our results show that the ΛCDM model remains a good fit to the current data. In a flat universe, we obtain the tight limit on the constant EoS of dark energy as, w = −0.977 ± 0.056 (1 σ). For the dynamical dark energy models with time evolving EoS parameterized as w de (a) = w0 + w1(1 − a), we find that the best-fit values are w0 = −1.08 and w1 = 0.368, implying the preference of Quintom model whose EoS gets across the cosmological constant boundary during evolution. For the curvature of universe Ω k , our results give −0.012 < Ω k < 0.009 (95% C.L.) when fixing w de = −1. When considering the dynamics of dark energy, the flat universe is still a good fit to the current data, −0.015 < Ω k < 0.018 (95% C.L.). Regarding the neutrino mass limit, we obtain the upper limits, mν < 0.533 eV (95% C.L.) within the framework of the flat ΛCDM model. When adding the SDSS Lyman-α forest power spectrum data, the constraint on mν can be significantly improved, mν < 0.161 eV (95% C.L.). However, these limits can be weakened by a factor of 2 in the framework of dynamical dark energy models, due to the obvious degeneracy between neutrino mass and the EoS of dark energy model. Assuming that the primordial fluctuations are adiabatic with a power law spectrum, within the ΛCDM model, we find that the upper limit on the ratio of the tensor to scalar is r < 0.200 (95% C.L.) and the inflationary models with the slope ns ≥ 1 are excluded at more than 2 σ confidence level. However, in the framework of dynamical dark energy models, the allowed region in the parameter space of (ns,r) is enlarged significantly. Finally, we find no strong evidence for the large running of the spectral index, αs = −0.019 ± 0.017 (1 σ) for the ΛCDM model and αs = −0.023 ± 0.019 (1 σ) for the dynamical dark energy model, respectively.

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Section: Neutrino Masssupporting

confidence: 91%

Determining cosmological parameters with the latest observational data

Xia

Zhao

et al. 2008

Phys. Rev. D

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“…while the amount of running allowed comes out as α s = −0.062 ± 0.02 in agreement with the findings of the WMAP team using the 3-year data. This result, although at odds with the findings in [38], is expected given the signficantly higher values of Ω m that are preferred in the presence of α s than in the case of constant n s . Without the SN data to restrict the matter density, small-scale structure suppression can be offset by an increase in the matter density.…”

Section: Running Spectral Index?contrasting

confidence: 59%

“…Given that significant running of the spectral index is still under debate and has implications on neutrino mass constraints, it seems worthwhile to explore. In recent work [38] the neutrino mass constraints were found to be lowered in the presence of a scale-variant n when the CMB, LSS and SN data was used. The SN data prefers a lower value of Ω m which means that the effect of increased m ν can not be absorbed by an slight increase in the matter density.…”

Section: Running Spectral Index?mentioning

confidence: 99%

Conservative estimates of the mass of the neutrino from cosmology

Zunckel

Ferreira

2007

J. Cosmol. Astropart. Phys.

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A range of experimental results point to the existence of a massive neutrino. The recent high precision measurements of the cosmic microwave background and the large scale surveys of galaxies can be used to place an upper bound on this mass. In this letter we perform a thorough analysis of all assumptions that go into obtaining a credible limit on mν. In particular we explore the impact of a cosmological parameters, the importance of priors, the uncertainties due to biasing in large scale structure and the dependence on choice of initial conditions. We find that the mass constraints are independent of the choice of parameterization as well as the inclusion of spatial curvature. Yet the difference between an upperbound of 2.2 eV, assuming generic initial conditions, and an upper bound of 0.63 eV, assuming adiabaticity and b = 1, demonstrate the dependence of such a constraint on the assumptions in the analysis.The neutrino is an integral component of the standard model of particle physics. Until recently it was assumed to be massless. With the new advances in non-accelerator particle physics there is now definitive evidence that this cannot be so: neutrinos must have mass. Tritium decay measurements have been able to place an upper limit on the electron neutrino mass of 2.3 eV at the 95% confidence level (CL) [1]. When the neutrino flavour transitions measured in atmospheric, solar and accelerator experiments [2] are interpreted within the 3-neutrino type scenario of the standard model, their masses are required to be in the 0.05 − 0.1 eV range. The claimed direct detection of neutrinoless double-β decay in the HeidelbergMoscow experiment tightens this range to 0.1 − 0.9 eV [3].Although it is unlikely that massive neutrinos are the dark matter it appears conceivable that they may still affect the growth of density perturbations in a measurable way. Neutrinos with a mass less than 2 eV are still relativistic when entering the horizon for scales of k = 0.1 h Mpc −1 and are quasi-relativistic at recombination. Therefore they cannot be treated as a non-relativistic component of the CMB and are not entirely degenerate with the other relativistic components [4]. In a matter dominated universe, a modicum of massive neutrinos will free-stream on scales of clusters and galaxies and therefore suppress the rate of growth of density perturbations from being proportional to the scale factor a to being proportional to a 1−ǫ where ǫ =, where the neutrino mass, m ν is related through the expression: Ω ν = m ν /(93.5h 2 ). Indeed it has been proposed that a mixed model with a combination of cold dark matter and massive neutrinos might be a viable alternative to the currently favoured Λ-Cold Dark Matter model (where Λ is the cosmological constant).The effect on the growth of structure supplies us with a useful method for constraining Ω ν and as a result, m ν . By measuring the amplitude of clustering on large scales (above the free streaming scale) and comparing it to the level of clustering on small scales (below the free streami...

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“…CMB and LSS present data do not require the introduction of the running to drastically improve the χ 2 , but substantial values at 95 per cent CL for the running are allowed and also weakly favoured by different and independent analyses of current data (Finelli, Rianna & Mandolesi 2006; Feng, Xia & Yokoyama 2007; Lesgourgues & Valkenburg 2007; Kilbinger et al 2009; Finelli et al 2010). These allowed values for the running might be just due to the degeneracy in cosmological parameters (Efstathiou & Bond 1999), but at the time being cosmological scenarios with and without running provide a very similar explanation of current observations.…”

Section: Introductionmentioning

confidence: 79%

Primordial density perturbations with running spectral index: impact on non-linear cosmic structures

Fedeli¹,

Finelli⋆²,

Moscardini³

2010

Monthly Notices of the Royal Astronomical Society

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We explore the statistical properties of non-linear cosmic structures in a flat cold dark matter ( CDM) cosmology in which the index n S of the primordial power spectrum for scalar perturbations is allowed to depend on the scale. Within the inflationary paradigm, the running of the scalar spectral index can be related to the properties of the inflation potential, and it is hence of critical importance to test it with all kinds of observations, which cover the linear and non-linear regime of gravitational instability. We focus on the amount of running α S,0 (≡ dn S /d ln(k/k p )) allowed by an updated combination of cosmic microwave background (CMB) anisotropy data and the 2dF Galaxy Redshift Survey. Our analysis constrains α S,0 = −0.051 +0.047 −0.053 (−0.034 +0.039 −0.040 ) at 95 per cent Confidence Level when (not) taking into account primordial gravitational waves in a ratio as predicted by canonical single field inflation, in agreement with other works. For the cosmological models best fitting the data both with and without running we studied the abundance of galaxy clusters and of rare objects, the halo bias, the concentration of dark matter haloes, the Baryon Acoustic Oscillation, the power spectrum of cosmic shear and the Integrated Sachs-Wolfe effect. We find that counting galaxy clusters in future X-ray and Sunyaev-Zel'dovich surveys could discriminate between the two models, more so if broad redshift information about the cluster samples will be available. Likewise, measurements of the power spectrum of cosmological weak lensing as performed by planned all-sky optical surveys such as EUCLID could detect a running of the primordial spectral index, provided the uncertainties about the source redshift distribution and the underlying matter power spectrum are well under control.

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Weighing neutrinos in the presence of a running primordial spectral index

Cited by 13 publications

References 37 publications

Determining cosmological parameters with the latest observational data

Determining cosmological parameters with the latest observational data

Conservative estimates of the mass of the neutrino from cosmology

Primordial density perturbations with running spectral index: impact on non-linear cosmic structures

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