Low CMB quadrupole from dark energy isocurvature perturbations

Gordon, Chris; Hu, Wayne

doi:10.1103/physrevd.70.083003

Cited by 155 publications

(180 citation statements)

References 72 publications

(96 reference statements)

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“…It is noteworthy that the substantial improvements (most recently [119]) in dark energy measurements since the first discovery [120,121] have not established any departures from "vanilla" [122,123]. However, improved dark energy observations are clearly crucial, since the fact that messy inflation may already explain ρ Λ = 0 and its rough magnitude does not in any way preclude the existence of additional physics producing non-vanilla dark energy at late times, and there are interesting hints at modest statistical significance (e.g., [124]). As shown in Figure 3, improved dark energy observations also complement CMB polarization observations by measuring the exact same curve ρ(a) at a vastly lower density.…”

Section: Vanilla or Not?mentioning

confidence: 99%

What does inflation really predict?

Tegmark

2005

J. Cosmol. Astropart. Phys.

188

232

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If the inflaton potential has multiple minima, as may be expected in, e.g., the string theory "landscape", inflation predicts a probability distribution for the cosmological parameters describing spatial curvature (Ωtot), dark energy (ρΛ, w, etc.), the primordial density fluctuations (Q, ns, dns/d ln k, etc.) and primordial gravitational waves (r, nt, etc.). We compute this multivariate probability distribution for various classes of single-field slow-roll models, exploring its dependence on the characteristic inflationary energy scales, the shape of the potential V and and the choice of measure underlying the calculation. We find that unless the characteristic scale ∆φ on which V varies happens to be near the Planck scale, the only aspect of V that matters observationally is the statistical distribution of its peaks and troughs. For all energy scales and plausible measures considered, we obtain the predictions Ωtot ≈ 1 ± 10 −5 , w = −1 and ρΛ in the observed ballpark but uncomfortably high. The high energy limit predicts ns ≈ 0.96, dns/d ln k ≈ −0.0006, r ≈ 0.15 and nt ≈ −0.02, consistent with observational data and indistinguishable from eternal V ∝ φ 2 inflation. The low-energy limit predicts 5 parameters but prefers larger Q and redder ns than observed. We discuss the coolness problem, the smoothness problem and the pothole paradox, which severely limit the viable class of models and measures. Predictions insensitive to pre-inflationary conditions can arise either from eternal inflation attractor behavior or from anthropic selection effects probing merely a tiny non-special part of the initial distribution. We argue that these two mechanisms are severely challenged by the coolness problem and the smoothness problem, respectively. Our findings bode well for detecting an inflationary gravitational wave signature with future CMB polarization experiments, with the arguably best-motivated single-field models favoring the detectable level r ∼ 0.03.

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Section: Vanilla or Not?mentioning

confidence: 99%

What does inflation really predict?

Tegmark

2005

J. Cosmol. Astropart. Phys.

188

232

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“…In addition, dark energy perturbations also affect the cold dark matter power spectrum at large scale [307]. This can be used to distinguish dark energy models [308].…”

Section: Dark Energy Perturbationsmentioning

confidence: 99%

Dark Energy

Li¹,

Li²,

Wang³

et al. 2011

Commun. Theor. Phys.

755

560

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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%

Punctuated inflation and the low CMB multipoles

Jain

Chingangbam

Gong

et al. 2009

J. Cosmol. Astropart. Phys.

149

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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Low CMB quadrupole from dark energy isocurvature perturbations

Cited by 155 publications

References 72 publications

What does inflation really predict?

What does inflation really predict?

Dark Energy

Punctuated inflation and the low CMB multipoles

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