Ruling out the power-law form of the scalar primordial spectrum

Hazra, Dhiraj Kumar; Shafieloo, Arman; Smoot, George F.; Starobinsky, Alexei A.

doi:10.1088/1475-7516/2014/06/061

Cited by 45 publications

(41 citation statements)

References 70 publications

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“…There was in fact even some indication of a preference over a power-law spectrum [512][513][514][515][516]. However, this conclusion had to be revised after the re-evaluation of the BICEP2 data using additional information from Planck and the Keck array [517] which showed that the B-mode signal originally attributed to primordial tensor perturbations can be explained in terms of polarised galactic dust emission.…”

Section: Models With a Large Scale Power Suppressionmentioning

confidence: 99%

Features and new physical scales in primordial observables: Theory and observation

Chluba

Hamann

Patil

2015

Int. J. Mod. Phys. D

212

233

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June 22, 20152 All cosmological observations to date are consistent with adiabatic, Gaussian and nearly scale invariant initial conditions. These findings provide strong evidence for a particular symmetry breaking pattern in the very early universe (with a close to vanishing order parameter, ), widely accepted as conforming to the predictions of the simplest realizations of the inflationary paradigm. However, given that our observations are only privy to perturbations, in inferring something about the background that gave rise to them, it should be clear that many different underlying constructions project onto the same set of cosmological observables. Features in the primordial correlation functions, if present, would offer a unique and discriminating window onto the parent theory in which the mechanism that generated the initial conditions is embedded. In certain contexts, simple linear response theory allows us to infer new characteristic scales from the presence of features that can break the aforementioned degeneracies among different background models, and in some cases can even offer a limited spectroscopy of the heavier degrees of freedom that couple to the inflaton. In this review, we offer a pedagogical survey of the diverse, theoretically well grounded mechanisms which can imprint features into primordial correlation functions in addition to reviewing the techniques one can employ to probe observations. These observations include cosmic microwave background anisotropies and spectral distortions as well as the matter two and three point functions as inferred from large-scale structure and potentially, 21 cm surveys.

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Section: Models With a Large Scale Power Suppressionmentioning

confidence: 99%

Features and new physical scales in primordial observables: Theory and observation

Chluba

Hamann

Patil

2015

Int. J. Mod. Phys. D

212

233

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“…The WWI model was introduced in [16] in order to address two major issues. Firstly with the BICEP2 B-mode signal, assuming to be primordial, we ruled out the power law form of scalar power spectrum with more than 3σ confidence [13]. We needed a strong suppression of scalar power at large scales and at the same time large tensors with low non-Gaussianities.…”

Section: Wiggly Whipped Inflationary Scenariomentioning

confidence: 99%

Primordial features and Planck polarization

Hazra

Shafieloo

Smoot

et al. 2016

J. Cosmol. Astropart. Phys.

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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).

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“…Moreover, as we have just discussed, the running of the scalar power spectrum cannot be used within slow-roll inflation to alleviate the above-mentioned tension, precisely because it cannot take large enough values. Solely in slow-roll violating models of inflation, such an explanation may be relevant [137][138][139][140][141].…”

Section: From This Equation One Hasmentioning

confidence: 99%

Compatibility of Planck and BICEP2 results in light of inflation

et al. 2014

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We investigate the implications for inflation of the detection of B-modes polarization in the Cosmic Microwave Background (CMB) by BICEP2. We show that the hypothesis of primordial origin of the measurement is favored only by the first four bandpowers, while the others would prefer unreasonably large values of the tensor-to-scalar ratio. Using only those four bandpowers, we carry out a complete analysis in the cosmological and inflationary slow-roll parameter space using the BICEP2 polarization measurements alone and extract the Bayesian evidences and complexities for all the Encyclopaedia Inflationaris models. This allows us to determine the most probable and simplest BICEP2 inflationary scenarios. Although this list contains the simplest monomial potentials, it also includes many other scenarios, suggesting that focusing model building efforts on large field models only is unjustified at this stage. We demonstrate that the sets of inflationary models preferred by Planck alone and BICEP2 alone are almost disjoint, indicating a clear tension between the two data sets. We address this tension with a Bayesian measure of compatibility between BICEP2 and Planck. We find that for models favored by Planck the two data sets tend to be incompatible, whereas there is a moderate evidence of compatibility for the BICEP2 preferred models. As a result, it would be premature to draw any conclusion on the best Planck models, such as Starobinsky and/or Kähler moduli inflation. For the subset of scenarios not exhibiting data sets incompatibility, we update the evidences and complexities using both data sets together.

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Ruling out the power-law form of the scalar primordial spectrum

Cited by 45 publications

References 70 publications

Features and new physical scales in primordial observables: Theory and observation

Features and new physical scales in primordial observables: Theory and observation

Primordial features and Planck polarization

Compatibility of Planck and BICEP2 results in light of inflation

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