58 research outputs found
Possible Signatures of Inflationary Particle Content: Spin-2 Fields
We study the imprints of a massive spin-2 field on inflationary observables,
and in particular on the breaking of consistency relations. In this setup, the
minimal inflationary field content interacts with the massive spin-2 field
through dRGT interactions, thus guaranteeing the absence of Boulware-Deser
ghostly degrees of freedom. The unitarity requirement on spinning particles,
known as Higuchi bound, plays a crucial role for the size of the observable
signal.Comment: 24 pages, 6 figure
Gravitational Waves and Scalar Perturbations from Spectator Fields
The most conventional mechanism for gravitational waves (gw) production
during inflation is the amplification of vacuum metric fluctuations. In this
case the gw production can be uniquely related to the inflationary expansion
rate . For example, a gw detection close to the present experimental limit
(tensor-to-scalar ratio ) would indicate an inflationary expansion
rate close to . This conclusion, however, would be
invalid if the observed gw originated from a different source. We construct and
study one of the possible covariant formulations of the mechanism suggested in
[43], where a spectator field with a sound speed acts as
a source for gw during inflation. In our formulation is described by a
so-called Lagrangian and a non-minimal coupling to gravity. This field
interacts only gravitationally with the inflaton, which has a standard action.
We compute the amount of scalar and tensor density fluctuations produced by
and find that, in our realization, is not enhanced with respect to
the standard result but it is strongly sensitive to , thus breaking the
direct connection.Comment: 22 page
Constraint of Void Bias on Primordial non-Gaussianity
We study the large-scale bias parameter of cosmic voids with primordial
non-Gaussian (PNG) initial conditions of the local type. In this scenario, the
dark matter halo bias exhibits a characteristic scale dependence on large
scales, which has been recognized as one of the most promising probes of the
local PNG. Using a suite of -body simulations with Gaussian and non-Gaussian
initial conditions, we find that the void bias features scale-dependent
corrections on large scales, similar to its halo counterpart. We find excellent
agreement between the numerical measurement of the PNG void bias and the
general peak-background split prediction. Contrary to halos, large voids
anti-correlate with the dark matter density field, and the large-scale Gaussian
void bias ranges from positive to negative values depending on void size and
redshift. Thus, the information in the clustering of voids can be complementary
to that of the halos. Using the Fisher matrix formalism for multiple tracers,
we demonstrate that including the scale-dependent bias information from voids,
constraints on the PNG parameter can be tightened by a factor of
two compared to the accessible information from halos alone, when the sampling
density of tracers reaches .Comment: 7 pages, 4 figures; dn/dlnsigma_8 prediction implemented and
excellent agreement with simulation results obtained. Matched to published
versio
Testing the Running of non-Gaussianity through the CMB mu-distortion and the Halo Bias
The primordial non-Gaussianity parameters fNL and tauNL may be
scale-dependent. We investigate the capability of future measurements of the
CMB mu-distortion, which is very sensitive to small scales, and of the
large-scale halo bias to test the running of local non-Gaussianity. We show
that, for an experiment such as PIXIE, a measurement of the mu-temperature
correlation can pin down the spectral indices n_fNL and n_tauNL to values of
the order of 0.3 if fNL = 20 and tauNL = 5000. A similar value can be achieved
with an all-sky survey extending to redshift z ~ 1. In the particular case in
which the two spectral indices are equal, as predicted in models where the
cosmological perturbations are generated by a single-field other than the
inflaton, then the 1-sigma error on the scale-dependence of the non-linearity
parameters goes down to 0.2.Comment: 11 pages, 7 figure
Primordial Gravitational Waves from Galaxy Intrinsic Alignments
Galaxy shapes have been observed to align with external tidal fields
generated by the large-scale structures of the Universe. While the main source
for these tidal fields is provided by long-wavelength density perturbations,
tensor perturbations also contribute with a non-vanishing amplitude at linear
order. We show that parity-breaking gravitational waves produced during
inflation leave a distinctive imprint in the galaxy shape power spectrum which
is not hampered by any scalar-induced tidal field. We also show that a certain
class of tensor non-Gaussianities produced during inflation can leave a
signature in the density-weighted galaxy shape power spectrum. We estimate the
possibility of observing such imprints in future galaxy surveys.Comment: 24+23 pages, 6 figures, code available at
https://gitlab.com/mbiagetti/tensor_fossil, updated to published versio
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