32 research outputs found

    Strongly scale-dependent polyspectra from curvaton self-interactions

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    We study the scale dependence of the non-linearity parameters f_NL and g_NL in curvaton models with self-interactions. We show that the spectral indices n_fNL=d ln|f_NL|/(d ln k) and n_gNL=d ln |g_NL|/(d ln k) can take values much greater than the slow--roll parameters and the spectral index of the power spectrum. This means that the scale--dependence of the bi and trispectrum could be easily observable in this scenario with Planck, which would lead to tight additional constraints on the model. Inspite of the highly non-trivial behaviour of f_NL and g_NL in the curvaton models with self-interactions, we find that the model can be falsified if g_NL(k) is also observed.Comment: 19 pages, many figures. v2: Figure 4 replaced with a corrected normalisation, conclusions unchanged. Matches version published in JCA

    Feeding your Inflaton: Non-Gaussian Signatures of Interaction Structure

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    Primordial non-Gaussianity is generated by interactions of the inflaton field, either self-interactions or couplings to other sectors. These two physically different mechanisms can lead to nearly indistinguishable bispectra of the equilateral type, but generate distinct patterns in the relative scaling of higher order moments. We illustrate these classes in a simple effective field theory framework where the flatness of the inflaton potential is protected by a softly broken shift symmetry. Since the distinctive difference between the two classes of interactions is the scaling of the moments, we investigate the implications for observables that depend on the series of moments. We obtain analytic expressions for the Minkowski functionals and the halo mass function for an arbitrary structure of moments, and use these to demonstrate how different classes of interactions might be distinguished observationally. Our analysis casts light on a number of theoretical issues, in particular we clarify the difference between the physics that keeps the distribution of fluctuations nearly Gaussian, and the physics that keeps the calculation under control.Comment: 33 pages (plus appendices), 3 figures. V2: references added, some minor clarifications. Accepted for publication in JCA

    Primordial Non-Gaussianity

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    Our current understanding of the Universe is established through the pristine measurements of structure in the cosmic microwave background (CMB) and the distribution and shapes of galaxies tracing the large scale structure (LSS) of the Universe. One key ingredient that underlies cosmological observables is that the field that sources the observed structure is assumed to be initially Gaussian with high precision. Nevertheless, a minimal deviation from Gaussianityis perhaps the most robust theoretical prediction of models that explain the observed Universe; itis necessarily present even in the simplest scenarios. In addition, most inflationary models produce far higher levels of non-Gaussianity. Since non-Gaussianity directly probes the dynamics in the early Universe, a detection would present a monumental discovery in cosmology, providing clues about physics at energy scales as high as the GUT scale

    Primordial Non-Gaussianity

    Get PDF
    Our current understanding of the Universe is established through the pristine measurements of structure in the cosmic microwave background (CMB) and the distribution and shapes of galaxies tracing the large scale structure (LSS) of the Universe. One key ingredient that underlies cosmological observables is that the field that sources the observed structure is assumed to be initially Gaussian with high precision. Nevertheless, a minimal deviation from Gaussianityis perhaps the most robust theoretical prediction of models that explain the observed Universe; itis necessarily present even in the simplest scenarios. In addition, most inflationary models produce far higher levels of non-Gaussianity. Since non-Gaussianity directly probes the dynamics in the early Universe, a detection would present a monumental discovery in cosmology, providing clues about physics at energy scales as high as the GUT scale

    Seeding primordial black holes in multifield inflation

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    The inflationary origin of primordial black holes (PBHs) relies on a large enhancement of the power spectrum Δζ\Delta_\zeta of the curvature fluctuation ζ\zeta at wavelengths much shorter than those of the cosmic microwave background anisotropies. This is typically achieved in models where ζ\zeta evolves without interacting significantly with additional (isocurvature) scalar degrees of freedom. However, quantum gravity inspired models are characterized by moduli spaces with highly curved geometries and a large number of scalar fields that could vigorously interact with ζ\zeta (as in the cosmological collider picture). Here we show that isocurvature fluctuations can mix with ζ\zeta inducing large enhancements of its amplitude. This occurs whenever the inflationary trajectory experiences rapid turns in the field space of the model leading to amplifications that are exponentially sensitive to the total angle swept by the turn, which induce characteristic observable signatures on Δζ\Delta_\zeta. We derive accurate analytical predictions and show that the large enhancements required for PBHs demand non-canonical kinetic terms in the action of the multifield system.Comment: 7 pages, 1 figure; v2: added clarifications around the analytic solution and references. Version accepted in PRL; v3: typo corrected, matches published versio

    Baryon acoustic oscillations and primordial non-Gaussianities with weak lensing

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    This work introduces two investigations on possible new weak lensing applications. In the first part, I present a study on the possibility of detecting baryon acoustic oscillations by means of 3d weak lensing (3dWL). Basing our analysis on a Fisher matrix approach, we quantify the uncertainty on inferring the amplitude of the power spectrum wiggles with 3dWL. Ultimately, we find that surveys like Euclid and DES should be able to detect, respectively, the first four and three oscillations, with errors reaching the 1% or 10% of the amplitude for the first two wiggles in the case of Euclid. The second part of this work focuses on the study of primordial non-Gaussianities with a classical weak lensing approach. We study inflationary bi- and trispectra, the strentgh of their signals, and the consequences of fitting data with a wrong type of bispectrum on the inferred on fNL. We conclude that contraints on fNL are not competitive with the ones from CMB, but nonetheless valuable in case of a scale-dependent fNL. Lastly, we quantify lensing ability to test the Suyama-Yamaguchi inequality, and ascertain that Euclid could give evidence in favour or against the inequality for large non-Gaussianity values (tauNL > 10^5 or fNL > 10^2)
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