Multi-field inflation with large scalar fluctuations: non-Gaussianity and perturbativity

Iacconi, Laura; Mulryne, David J.

doi:10.1088/1475-7516/2023/09/033

Cited by 22 publications

(6 citation statements)

References 129 publications

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“…In equation (2.3), W(kR f ) is the window function, P R the primordial spectrum of curvature fluctuations R and in the last step we use the relation between density fluctuations and curvature fluctuations on superhorizon scales in a radiation dominated Universe [5]. The 11 See [176][177][178][179][180][181][182][183][184][185][186][187][188][189][190] for an interesting ongoing discussion on the impact of one loop quantum effects.…”

Section: Gw Signals Of Black Holes From the Early Universementioning

confidence: 99%

Probing primordial black hole scenarios with terrestrial gravitational wave detectors

Domènech,

Sasaki

2024

Class. Quantum Grav.

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It is possible that primordial black holes constitute (or constituted) a significant fraction of the energy budget of our universe. Terrestrial gravitational wave detectors offer the opportunity to test the existence of primordial black holes in two different mass ranges, from $10^2\,{\rm g}-10^{16}\,{\rm g}$ to $10^{-6}\,M_\odot-100 \,M_\odot$. The first mass window is open via induced gravitational waves, and the second one is by gravitational waves from binary mergers. In this review, we outline and explain the different gravitational wave signatures of primordial black holes that may be probed by terrestrial gravitational wave detectors, such as the current LIGO/Virgo/KAGRA and future ones like Einstein Telescope and Cosmic Explorer. We mainly focus on the associated GW background signals and provide rough estimates for their typical frequency and amplitude. We also discuss complementary probes for these primordial black hole mass ranges.

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Section: Gw Signals Of Black Holes From the Early Universementioning

confidence: 99%

Probing primordial black hole scenarios with terrestrial gravitational wave detectors

Domènech,

Sasaki

2024

Class. Quantum Grav.

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“…). These models have been considered, e.g., in primoridal black hole formation scenarios [31,70] (see [71] for the analysis of non-Gaussianity). The universal predictions derived within exponential and polynomial α-attractors are different [69].…”

Section: Future Prospectsmentioning

confidence: 99%

Novel CMB constraints on the α parameter in alpha-attractor models

Iacconi,

Fasiello,

Väliviita

et al. 2023

J. Cosmol. Astropart. Phys.

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Cosmological α-attractors are a compelling class of inflationary models. They lead to universal predictions for large-scale observables, broadly independent from the functional form of the inflaton potential. In this work we derive improved analytical predictions for the large-scale observables, whose dependence on the duration of reheating and the parameter α is made explicit. We compare these with Planck and BICEP/Keck 2018 data in the framework of a Bayesian study, employing uniform logarithmic and linear priors for α. Our improved universal predictions allow direct constraints on the duration of reheating. Furthermore, while it is well-known that CMB constraints on the tensor-to-scalar ratio can be used to place an upper bound on the α parameter, we demonstrate that including the α-dependence of the scalar spectral tilt yields novel constraints on α. In particular, for small α, the scalar spectral tilt scales with log10 α, regardless of the specific potential shape. For decreasing α, this eventually puts the models in tension with CMB measurements, bounding the magnitude of α from below. Therefore, in addition to the upper bound from the tensor-to-scalar ratio, we derive the first lower bound on the magnitude of α for α-attractor T-models, log10 α = -4.2+5.4 -8.6 at 95% C.L.

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“…The study of an amplification of scalar power spectrum has also been extended to multifield models. Multi-field inflationary models have been widely explored for the production of PBHs [56][57][58][59][60][61][62][63][64][65][66][67][68]. Models with a non-canonical kinetic term in the Lagrangian can lead to a significant enhancement in the scalar power spectrum [62][63][64][65][66][67][68][69][70].…”

Section: Introductionmentioning

confidence: 99%

Mechanisms for Producing Primordial Black Holes from Inflationary Models beyond Fine-Tuning

Stamou

2024

Universe

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In this study, we present an analysis of the fine-tuning required in various inflationary models in order to explain the production of Primordial Black Holes (PBHs). We specifically examine the degree of fine-tuning necessary in two prominent single-field inflationary models: those with an inflection point and those with step-like features in the potential. Our findings indicate that models with step-like features generally require less fine-tuning compared to those with an inflection point, making them more viable for consistent PBH production. An interesting outcome of these models is that, in addition to improved fine-tuning, they may also predict low-frequency signals that can be detected by pulsar timing array (PTA) collaborations. Additionally, we extend our analysis to multifield inflationary models to assess whether the integration of additional fields can further alleviate the fine-tuning demands. The study also explores the role of a spectator field and its impact on the fine-tuning process. Our results indicate that although mechanisms involving a spectator field can circumvent the issue of fine-tuning parameters for PBH production, both multifield models and models with step-like features present promising alternatives. While fine-tuning involves multiple considerations, our primary objective is to evaluate various inflationary models to identify the one that most naturally explains the formation of PBHs. Hence, this study introduces a novel approach by categorizing existing PBH mechanisms, paving the way for subsequent research to prioritize models that minimize the need for extensive fine-tuning.

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Multi-field inflation with large scalar fluctuations: non-Gaussianity and perturbativity

Cited by 22 publications

References 129 publications

Probing primordial black hole scenarios with terrestrial gravitational wave detectors

Probing primordial black hole scenarios with terrestrial gravitational wave detectors

Novel CMB constraints on the α parameter in alpha-attractor models

Mechanisms for Producing Primordial Black Holes from Inflationary Models beyond Fine-Tuning

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