Suppressing the lower multipoles in the CMB anisotropies

Abstract. Combining Planck CMB temperature [1] and BICEP2 B-mode polarization data [2,3] we show qualitatively that, assuming inflationary consistency relation, the power-law form of the scalar primordial spectrum is ruled out at more than 3σ CL. This is an important finding, since the power-law form of the scalar primordial spectrum is one of the main assumptions of concordance model of cosmology and also a direct prediction of many inflationary scenarios. We show that a break or step in the form of the primordial scalar perturbation spectrum, similar to what we studied recently analyzing Planck data [4], can address both Planck and BICEP2 results simultaneously. Our findings also indicate that the data may require more flexibilities than what running of scalar spectral index can provide. Finally we show that an inflaton potential, originally appeared in [5], can generate both the step and the break model of scalar primordial spectrum in two different limits. The discussed potential is found to be favored by Planck data but marginally disfavored by BICEP2 results as it produces slightly lower amplitude of tensor primordial spectrum. Hence, if the tensor-to-scalar ratio (r) quoted by BICEP2 persists, it is of importance that we generate inflationary models with large r and at the same time provide suppression in scalar primordial spectrum at large scales.

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“…In turn, this model is a simplified and smoothed version of the exact scalar PPS derived in [12]. A similar PPS was also studied in [13].…”

Section: Formalismmentioning

confidence: 99%

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

Hazra

Shafieloo

Smoot

et al. 2014

J. Cosmol. Astropart. Phys.

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“…[6,7,8,9] and references therein), there has also been constant activity to understand possible underlying physical reasons for the outliers (see, for an inexhaustive list, Refs. [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32]). …”

Section: Introductionmentioning

confidence: 99%

“…Within the inflationary scenario, a variety of single and two field models have been constructed to produce such a drop in power at the large scales [10,12,18,19,20,27,29,30,32]. However, in single field inflationary models, in order to produce such a spectrum, we find that many of the scenarios either assume a specific pre-inflationary regime, say, a radiation dominated epoch, or special initial conditions for the background scalar field, such as an initial period of fast roll [18,19,29,30]. Moreover, some of them impose the initial conditions on the perturbations when the largest scales are outside the Hubble radius during the pre-inflationary or the fast roll regime [18,29,30].…”

Section: Introductionmentioning

confidence: 99%

Punctuated inflation and the low CMB multipoles

Jain

Chingangbam

Gong

et al. 2009

J. Cosmol. Astropart. Phys.

148

172

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Abstract. We investigate inflationary scenarios driven by a class of potentials which are similar in form to those that arise in certain minimal supersymmetric extensions of the standard model. We find that these potentials allow a brief period of departure from inflation sandwiched between two stages of slow roll inflation. We show that such a background behavior leads to a step like feature in the scalar power spectrum. We set the scales such that the drop in the power spectrum occurs at a length scale that corresponds to the Hubble radius today-a feature that seems necessary to explain the lower power observed in the quadrupole moment of the Cosmic Microwave Background (CMB) anisotropies. We perform a Markov Chain Monte Carlo analysis to determine the values of the model parameters that provide the best fit to the recent WMAP 5-year data for the CMB angular power spectrum. We find that an inflationary spectrum with a suppression of power at large scales that we obtain leads to a much better fit (with just one extra parameter, χ 2 eff improves by 6.62) of the observed data when compared to the best fit reference ΛCDM model with a featureless, power law, primordial spectrum.

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“…They include a cut off in the primordial power spectrum [18,19,20,21,22,23,24,25,26,27,28,29,30,31], a small universe [2,32,33,34,35] and perturbations in the dark energy [36,37,38,39,40]. The cut-off and small Universe models work by reducing the Sachs Wolfe effect in the quadrupole.…”

Section: Introductionmentioning

confidence: 99%

Low CMB quadrupole from dark energy isocurvature perturbations

2004

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We explicate the origin of the temperature quadrupole in the adiabatic dark energy model and explore the mechanism by which scale invariant isocurvature dark energy perturbations can lead to its sharp suppression. The model requires anticorrelated curvature and isocurvature fluctuations and is favored by the WMAP data at about the 95% confidence level in a flat scale invariant model. In an inflationary context, the anticorrelation may be established if the curvature fluctuations originate from a variable decay rate of the inflaton; such models however tend to overpredict gravitational waves. This isocurvature model can in the future be distinguished from alternatives involving a reduction in large scale power or modifications to the sound speed of the dark energy through the polarization and its cross correlation with the temperature. The isocurvature model retains the same polarization fluctuations as its adiabatic counterpart but reduces the correlated temperature fluctuations. We present a pedagogical discussion of dark energy fluctuations in a quintessence and k-essence context in the Appendix.

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Suppressing the lower multipoles in the CMB anisotropies

Cited by 402 publications

References 60 publications

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

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

Punctuated inflation and the low CMB multipoles

Low CMB quadrupole from dark energy isocurvature perturbations

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