32 research outputs found
Strongly scale-dependent polyspectra from curvaton self-interactions
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
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
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
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
The inflationary origin of primordial black holes (PBHs) relies on a large
enhancement of the power spectrum of the curvature fluctuation
at wavelengths much shorter than those of the cosmic microwave
background anisotropies. This is typically achieved in models where
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 (as in the cosmological
collider picture). Here we show that isocurvature fluctuations can mix with
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
. 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
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)