Fine features in the primordial power spectrum

Kumazaki, Kohei; Yokoyama, Shuichiro; Sugiyama, Naoshi

doi:10.1088/1475-7516/2011/12/008

Cited by 17 publications

(11 citation statements)

References 38 publications

(69 reference statements)

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“…More complex models generating deviations from scale invariance include those with features on the potential (Starobinsky 1992;Adams et al 2001;Wang et al 2005;Hunt & Sarkar 2004Joy et al 2008;Pahud et al 2009;Lerner & McDonald 2009;Kumazaki et al 2011;Meerburg et al 2012;Ashoorioon & Krause 2006;Ashoorioon et al 2009), a small number of e-folds (Contaldi et al 2003;Powell & Kinney 2007;Nicholson & Contaldi 2008), or other exotic inflationary models (Lesgourgues 2000;Feng & Zhang 2003;Mathews et al 2004;Jain et al 2009;Romano & Sasaki 2008;Piao et al 2004;Choudhury et al 2013;Choudhury & Mazumdar 2014). Therefore, determining the shape of the primordial power spectrum will allow us to evaluate how well these models of the early Universe compare to the observations, rule out some of the proposed models, and thus will give us a better intuition into the conditions of the primordial Universe.…”

Section: Introductionmentioning

confidence: 99%

PRISM: Sparse recovery of the primordial power spectrum

Paykari

Lanusse

Starck

et al. 2014

A&A

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Aims. The primordial power spectrum describes the initial perturbations in the Universe which eventually grew into the large-scale structure we observe today, and thereby provides an indirect probe of inflation or other structure-formation mechanisms. Here, we introduce a new method to estimate this spectrum from the empirical power spectrum of cosmic microwave background maps. Methods. A sparsity-based linear inversion method, named PRISM, is presented. This technique leverages a sparsity prior on features in the primordial power spectrum in a wavelet basis to regularise the inverse problem. This non-parametric approach does not assume a strong prior on the shape of the primordial power spectrum, yet is able to correctly reconstruct its global shape as well as localised features. These advantages make this method robust for detecting deviations from the currently favoured scale-invariant spectrum. Results. We investigate the strength of this method on a set of WMAP nine-year simulated data for three types of primordial power spectra: a near scale-invariant spectrum, a spectrum with a small running of the spectral index, and a spectrum with a localised feature. This technique proves that it can easily detect deviations from a pure scale-invariant power spectrum and is suitable for distinguishing between simple models of the inflation. We process the WMAP nine-year data and find no significant departure from a near scaleinvariant power spectrum with the spectral index n s = 0.972. Conclusions. A high-resolution primordial power spectrum can be reconstructed with this technique, where any strong local deviations or small global deviations from a pure scale-invariant spectrum can easily be detected.

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Section: Introductionmentioning

confidence: 99%

PRISM: Sparse recovery of the primordial power spectrum

Paykari

Lanusse

Starck

et al. 2014

A&A

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“…See[156][157][158][159][160][161][162][163][164][165][166][167][168][169][170][171][172][173] for various extensions and applications of this method and[174][175][176][177][178][179][180][181][182][183][184][185][186] for other related methods.…”

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confidence: 99%

Frame-dependence of higher-order inflationary observables in scalar-tensor theories

2017

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In the context of scalar-tensor theories of gravity we compute the third-order corrected spectral indices in the slow-roll approximation. The calculation is carried out by employing the Green's function method for scalar and tensor perturbations in both the Einstein and Jordan frames. Then, using the interrelations between the Hubble slow-roll parameters in the two frames we find that the frames are equivalent up to third order. Since the Hubble slow-roll parameters are related to the potential slowroll parameters, we express the observables in terms of the latter which are manifestly invariant. Nevertheless, the same inflaton excursion leads to different predictions in the two frames since the definition of the number of e-folds differs. To illustrate this effect we consider a nonminimal inflationary model and find that the difference in the predictions grows with the nonminimal coupling and it can actually be larger than the difference between the first and third order results for the observables. Finally, we demonstrate the effect of various end-of-inflation conditions on the observables. These effects will become important for the analyses of inflationary models in view of the improved sensitivity of future experiments.Keywords: scalar-tensor theory, slow-roll inflation, conformal frames, invariants, number of e-folds 1 alkaram@cc.uoi.gr 2 thpap@cc.uoi.gr 3 tamvakis@uoi.gr 1 See however [9]. 2 See also [95][96][97][98] for considerations on the quantum equivalence of the frames.

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“…The temperature spectrum [44], temperature non-Gaussianity [45][46][47], and polarization [48] can all be scanned for this purpose. Usually, fine features are inserted ad hoc in the power spectrum [43,49] or generated by inflationary dynamics [43,[50][51][52], while in the present case they arise purely from geometry. Since features can even improve the fit of Planck 2015 data [52], the issue at stake here is not just how to constrain the parameters of one or more quantum-gravity models, but also whether these models can account for some details of the CMB multipole spectrum better than the standard ΛCDM model of general relativity.…”

Section: Can We Observe Complex Dimensions?mentioning

confidence: 96%

Complex dimensions and their observability

Calcagni

2017

Phys. Rev. D

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We show that the dimension of spacetime becomes complex-valued when its short-scale geometry is invariant under a discrete scaling symmetry. This characteristic can generically arise in quantum gravities, for instance, in those based on combinatorial or multifractal structures or as the partial breaking of continuous dilation symmetry in any conformal-invariant theory. With its infinite scale hierarchy, discrete scale invariance overlaps with the traditional separation between ultraviolet and infrared physics and it can leave an all-range observable imprint, such as a pattern of log oscillations and sharp features in the cosmic microwave background primordial power spectrum.Comment: 6 pages, 1 figure. v2: discussion slightly expande

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Fine features in the primordial power spectrum

Cited by 17 publications

References 38 publications

PRISM: Sparse recovery of the primordial power spectrum

PRISM: Sparse recovery of the primordial power spectrum

Frame-dependence of higher-order inflationary observables in scalar-tensor theories

Complex dimensions and their observability

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