The WiggleZ Dark Energy Survey: mapping the distance-redshift relation with baryon acoustic oscillations

Current data from the Planck satellite and the BICEP2 telescope favor, at around the 2σ level, negative running of the spectral index of curvature perturbations from inflation. We show that for negative running α < 0, the curvature perturbation amplitude has a maximum on scales larger than our current horizon size. A condition for the absence of eternal inflation is that the curvature perturbation amplitude always remain below unity on superhorizon scales. For current bounds on nS from Planck, this corresponds to an upper bound of the running α < −4 × 10 −5 , so that even tiny running of the scalar spectral index is sufficient to prevent eternal inflation from occurring, as long as the running remains negative on scales outside the horizon. In single-field inflation models, negative running is associated with a finite duration of inflation: we show that eternal inflation may not occur even in cases where inflation lasts as long as 10 4 e-folds.

“…The fit assumes a flat universe [43], the 6dF Galaxy Survey [44], and the WiggleZ Dark Energy Survey [45] (dashed contours). The pivot scale is taken to be k = 0.05h MpC −1 .…”

Section: Evidence For Running Of the Spectral Indexmentioning

confidence: 99%

Negative running can prevent eternal inflation

Kinney¹,

Freese²

2015

“…We also use Cosmic Microwave Background (CMB) [14,15] and Large-Scale Structure (LSS) data [16,17] to help break the degeneracy between the scalar field parameters and the matter density parameter Ω m0 . For SNe Ia data, we use the publicly available latest Union2.1 compilation [13] which consists of 580 data points.…”

Section: A Observational Analysismentioning

confidence: 99%

Constraining thawing and freezing models with cluster number counts

Devi¹,

González²,

Alcaniz³

2014

Measurements of the cluster abundance as a function of mass and redshift provide an important cosmological test that probe not only the expansion rate but also the growth of perturbations. In this paper we adopt a scalar field scenario which admits both thawing and freezing solutions from an appropriate choice of the model parameters and derived all relevant expressions to calculate the mass function and the cluster number density. We discuss the ability of cluster observations to distinguish between these scalar field behaviors and the standard ΛCDM scenario by considering the eROSITA and SPT cluster surveys.PACS numbers: 98.80.Es, 95.36.+x

“…In Ref. [4] the correlation between the measurements at z = 0.44 and 0.73 was assumed to be zero since it was not available in the original reference [15]. We also used the results from WMAP9-year [18]: l A = 302.35±0.65, r s (z d ) = 152.3±1.3 and r s (z * ) = 145.8 ± 1.2 which gives …”

Section: Baryon Acoustic Oscillations and Cosmic Microwave Backgroundmentioning

confidence: 99%

“…We use the following datasets: a) observations of type Ia supernovae from the Joint Lightcurve Analysis (JLA) of the Sloan Digital Sky Survey (SDSS-II) and the Supernova Legacy Survey (SNLS) samples [12]; b) observations of baryon acoustic oscillations in the SDSS DR7 [13] and SDSS DR9 [14], in the WiggleZ Survey [15] and in the 6dF Galaxy Survey (6dFGRS) [16]; c) measurements of cosmic microwave background temperature anisotropy from 2015 Planck [17] and WMAP9-year [18]; d) observations of the Hubble rate H(z) from [19][20][21][22][23][24]. In the following subsections, the statistical analysis used to deal with those observables is briefly described.…”

Section: Observational Datamentioning

confidence: 99%

Constraining the cosmic deceleration-acceleration transition with type Ia supernova, BAO/CMB and H(z) data

Santos

Reis

Waga

2016

Abstract. We revisit the kink-like parametrization of the deceleration parameter q(z) [1], which considers a transition, at redshift z t , from cosmic deceleration to acceleration. In this parametrization the initial, at z z t , value of the q-parameter is q i , its final, z = −1, value is q f and the duration of the transition is parametrized by τ . By assuming a flat space geometry we obtain constraints on the free parameters of the model using recent data from type Ia supernovae (SN Ia), baryon acoustic oscillations (BAO), cosmic microwave background (CMB) and the Hubble parameter H(z). The use of H(z) data introduces an explicit dependence of the combined likelihood on the present value of the Hubble parameter H 0 , allowing us to explore the influence of different priors when marginalizing over this parameter. We also study the importance of the CMB information in the results by considering data from WMAP7, WMAP9 (Wilkinson Microwave Anisotropy Probe -7 and 9 years) and Planck 2015. We show that the contours and best fit do not depend much on the different CMB data used and that the considered new BAO data is responsible for most of the improvement in the results. Assuming a flat space geometry, q i = 1/2 and expressing the present value of the deceleration parameter q 0 as a function of the other three free parameters, we obtain z t = 0.67 +0.10 −0.08 , τ = 0.26 +0.14 −0.10 and q 0 = −0.48 +0.11 −0.13 , at 68% of confidence level, with an uniform prior over H 0 . If in addition we fix q f = −1, as in flat ΛCDM, DGP and Chaplygin quartessence that are special models described by our parametrization, we get z t = 0.66 +0.03 −0.04 , τ = 0.33 +0.04 −0.04 and q 0 = −0.54 +0.05 −0.07 , in excellent agreement with flat ΛCDM for which τ = 1/3. We also obtain for flat wCDM, another dark energy model described by our parametrization, the constraint on the equation of state parameter −1.22 < w < −0.78 at more than 99% confidence level.