Primordial features and Planck polarization

Abstract

Abstract. With the Planck 2015 Cosmic Microwave Background (CMB) temperature and polarization data, we search for possible features in the primordial power spectrum (PPS). We revisit the Wiggly Whipped Inflation (WWI) framework and demonstrate how generation of some particular primordial features can improve the fit to Planck data. WWI potential allows the scalar field to transit from a steeper potential to a nearly flat potential through a discontinuity either in potential or in its derivatives. WWI offers the inflaton potential parametrizations that generate a wide variety of features in the primordial power spectra incorporating most of the localized and non-local inflationary features that are obtained upon reconstruction from temperature and polarization angular power spectrum. At the same time, in a single framework it allows us to have a background parameter estimation with a nearly free-form primordial spectrum. Using Planck 2015 data, we constrain the primordial features in the context of Wiggly Whipped Inflation and present the features that are supported both by temperature and polarization. WWI model provides more than 13 improvement in χ 2 fit to the data with respect to the best fit power law model considering combined temperature and polarization data from Planck and B-mode polarization data from BICEP and Planck dust map. We use 2-4 extra parameters in the WWI model compared to the featureless strict slow roll inflaton potential. We find that the differences between the temperature and polarization data in constraining background cosmological parameters such as baryon density, cold dark matter density are reduced to a good extent if we use primordial power spectra from WWI. We also discuss the extent of bispectra obtained from the best potentials in arbitrary triangular configurations using the BI-spectra and Non-Gaussianity Operator (BINGO).

Robust predictions for an oscillatory bispectrum in Planck 2015 data from transient reductions in the speed of sound of the inflaton

“…The mode 800 is restricted to the first acoustic peak and fits a small number of apparent wiggles in the data. The maximum a posteriori (MAP) of 1000 tries to fit the dip in temperature at ≈ 20 and the following peak at ≈ 40, at the cost of raising the power at ≈ 10 and below (a similar feature in 2015 data has been reported in [2,[41][42][43][44]). Despite the goodness of the fit, this is in conflict with the apparent lack of power at very small multipoles seen in Planck's data, and may impose an even more stringent upper limit on the relative amplitude r of the tensor primordial power spectrum.…”

Probing features in the primordial perturbation spectrum with large-scale structure data

“…Due to the excellent accuracy with which the standard ΛCDM 6-parameter model fits the Planck data with l > 40, we restrict ourselves to models which, first, produce localised features in the PPS and, second, fit the smooth small-scale part of the PPS outside the features as well as possible in terms of the PPS slope n s ≈ 0.965 measured by Planck. Characteristic examples of such models are the Wiggly-wipped inflationary (WWI) models introduced in Hazra et al (2014aHazra et al ( , 2016. These models produce a better fit to the CMB data than the powerlaw model, and are thus not currently distinguishable from each other using the CMB data alone.…”

From non-trivial geometries to power spectra and vice versa

“…Figure 3: The left hand figure shows the Hubble parameter and the right shows the first slow-roll parameter for a model with features. This model which was proposed [21,22] to explain the observed features in the scalar power spectrum at ℓ ≈ 22 and ℓ ≈ 40 which are visible in the data reported from both WMAP [16,17,18] and PLANCK [19,20]. Note that the feature has little impact on H(n) but it does lead to a distinct bump in ǫ(n).…”