CMB $μT$ cross-correlations as a probe of PBH scenarios

Özsoy, Ogan; Tasinato, Gianmassimo

doi:10.48550/arxiv.2104.12792

Cited by 8 publications

(22 citation statements)

References 34 publications

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“…If the dip feature occurs at relatively large scales, say 10 Mpc −1 ≤ k dip ≤ 10 4 Mpc −1 , the properties of the resulting curvature spectrum can be probed through CMB µ−distortions, using well controlled CMB physics in the linear regime [58,59] (see [60,61] for a review). This possibility was suggested in [20], building on the ideas first developed in [21]. In this section we further develop and extend these arguments.…”

Section: Cmb µ-Distortions and Non-gaussianity Around The Dipmentioning

confidence: 75%

“…First, the spectrum as a function of momentum does not grow faster than k 4 in its way towards the peak [18], see for example Fig 1. Second, the growth of the spectrum is preceded by a pronounced dip, whose position is controlled by the total enhancement of the spectrum [19]. In [20], building on the original idea of [21], we showed that large squeezed non-Gaussianity in proximity of the dip of the spectrum induces sizeable cross-correlations between CMB µ-distortions and temperature fluctuations, which can be used as a test of PBH scenarios based on single-field inflation. Interestingly, this proposal is based only on well understood perturbation theory at large cosmological scales, and does not need to consider complex non-linear phenomena occurring at PBH formation.…”

Section: Introductionmentioning

confidence: 88%

“…We begin by the squeezed limit of the scale dependent non-linearity parameter 3 . For scales that exit the horizon during the initial slow-roll era, noting the scale invariance of P R (τ k ) factors, we take the squeezed limit k 3 → 0 (k 1 k 2 ≡ q) of (3.14) which yields [20,47]…”

Section: Bispectrum In the Squeezed Limit: A Consistency Relation Aro...mentioning

confidence: 99%

“…[54][55][56]). As we mentioned earlier in [20], the gradient expansion formalism has the advantage of analytic control that allows us to transparently capture the features of n-point scalar correlation functions using a few parameters such as the duration of the transient…”

Section: Trispectrum In the Collapsed Limit And Its Consistency Relationmentioning

confidence: 99%

“…In section 4, we study the implications of our findings for CMB µ-distortions. In this respect, we go beyond the analysis carried in [20] by developing the following points: First, we show how the information provided by the consistency relations allows us to carry on a more detailed analysis of µT correlators, whose quantitative and qualitative features depend on the properties of the scale-dependent squeezed bispectrum. Then, we study for the first time the implications for the µµ self-correlator of a scale-dependent collapsed trispectrum around the dip.…”

Section: Introductionmentioning

confidence: 99%

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Consistency conditions and primordial black holes in single field inflation

Özsoy,

Tasinato

2021

Preprint

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We discuss new consistency relations for single field models of inflation capable of generating primordial black holes (PBH), and their observational implications for CMB µ-space distortions. These inflationary models include a short period of non-attractor evolution: the scale-dependent profile of curvature perturbation is characterised by a pronounced dip, followed by a rapid growth leading to a peak responsible for PBH formation. We investigate the squeezed and the collapsed limits of three and four point functions of curvature perturbation around the dip, showing that they satisfy consistency relations connecting their values to the total amplification of the curvature spectrum, and to the duration of the non-attractor era.Moreover, the corresponding non-Gaussian parameters are scale-dependent in proximity of the dip, with features that again depend on the amplification of the spectrum. For typical PBH scenarios requiring an order O(10 7 ) enhancement of the spectrum from large towards small scales, we generally find values f sq NL = O(10) and τ col NL = O(10 3 ) in a range of scales that can be probed by CMB µ-space distortions. Using these consistency relations, we carefully analyse how the scale-dependence of non-Gaussian parameters leads to characteristic features in µT and µµ correlators, providing distinctive probes of inflationary PBH scenarios that can be tested using well-understood CMB physics.

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Section: Cmb µ-Distortions and Non-gaussianity Around The Dipmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 88%

Section: Bispectrum In the Squeezed Limit: A Consistency Relation Aro...mentioning

confidence: 99%

Section: Trispectrum In the Collapsed Limit And Its Consistency Relationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Consistency conditions and primordial black holes in single field inflation

Özsoy,

Tasinato

2021

Preprint

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Primordial tensor bispectra in μ-CMB cross-correlations

Orlando

Meerburg

Patil

2022

J. Cosmol. Astropart. Phys.

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Cross-correlations between Cosmic Microwave Background (CMB) temperature and polarization anisotropies and μ-spectral distortions have been considered to measure (squeezed) primordial scalar bispectra in a range of scales inaccessible to primary CMB bispectra. In this work we address whether it is possible to constrain tensor non-Gaussianities with these cross-correlations. We find that only primordial tensor bispectra with statistical anisotropies leave distinct signatures, while isotropic tensor bispectra leave either vanishing or highly suppressed signatures. We discuss how the angular dependence of squeezed bispectra in terms of the short and long momenta determine the non-zero cross-correlations. We also discuss how these non-vanishing configurations are affected by the way in which primordial bispectra transform under parity. By employing the so-called BipoSH formalism to capture the observational effects of statistical anisotropies, we make Fisher-forecasts to assess the detection prospects from μ T, μ E and μ B cross-correlations. Observing statistical anisotropies in squeezed ⟨γγγ⟩ and ⟨γγζ⟩ bispectra is going to be challenging as the imprint of tensor perturbations on μ-distortions is subdominant to scalar perturbations, therefore requiring a large, independent amplification of the effect of tensor perturbations in the μ-epoch. In absence of such a mechanism, statistical anisotropies in squeezed ⟨ζζγ⟩ bispectrum are the most relevant sources of μ T, μ E and μ B cross-correlations. In particular, we point out that in anisotropic inflationary models where ⟨ζζζ⟩ leaves potentially observable signatures in μ T and μ E, the detection prospects of ⟨ζζγ⟩ from μ B are enhanced.

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Revisiting small-scale fluctuations in α-attractor models of inflation

Iacconi

Assadullahi

Fasiello

et al. 2022

J. Cosmol. Astropart. Phys.

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Cosmological α-attractors stand out as particularly compelling models to describe inflation in the very early universe, naturally meeting tight observational bounds from cosmic microwave background (CMB) experiments. We investigate α-attractor potentials in the presence of an inflection point, leading to enhanced curvature perturbations on small scales. We study both single- and multi-field models, driven by scalar fields living on a hyperbolic field space. In the single-field case, ultra-slow-roll dynamics at the inflection point is responsible for the growth of the power spectrum, while in the multi-field set-up we study the effect of geometrical destabilisation and non-geodesic motion in field space. The two mechanisms can in principle be distinguished through the spectral shape of the resulting scalar power spectrum on small scales. These enhanced scalar perturbations can lead to primordial black hole (PBH) production and second-order gravitational wave (GW) generation. Due to the existence of universal predictions in α-attractors, consistency with current CMB constraints on the large-scale spectral tilt implies that PBHs can only be produced with masses smaller than 108 g and are accompanied by ultra-high frequency GWs, with a peak expected to be at frequencies of order 10 kHz or above.

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CMB $μT$ cross-correlations as a probe of PBH scenarios

Cited by 8 publications

References 34 publications

Consistency conditions and primordial black holes in single field inflation

Consistency conditions and primordial black holes in single field inflation

Primordial tensor bispectra in μ-CMB cross-correlations

Revisiting small-scale fluctuations in α-attractor models of inflation

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