159 research outputs found
Horizon-Flow off-track for Inflation
Inflation can be parameterized by means of truncated flow equations. In this
"horizon-flow" setup, generic results have been obtained, such as typical
values for . They are sometimes referred to as intrinsic
features of inflation itself. In this paper we first show that the
phenomenological class of inflationary potentials sampled by horizon-flow is
directly responsible for such predictions. They are therefore anything but
generic. Furthermore, the horizon-flow setup is shown to rely on trajectories
in phase space that differ from the slow-roll. For a given potential, we
demonstrate that this renders horizon-flow blind to entire relevant
inflationary regimes, for which the horizon-flow trajectory is shown to be
unstable. This makes horizon-flow a biased parameterization of inflation.Comment: 26 pages, 20 figures. Matches published versio
Bell's Inequalities for Continuous-Variable Systems in Generic Squeezed States
Bell's inequality for continuous-variable bipartite systems is studied. The
inequality is expressed in terms of pseudo-spin operators and quantum
expectation values are calculated for generic two-mode squeezed states
characterized by a squeezing parameter and a squeezing angle .
Allowing for generic values of the squeezing angle is especially relevant when
is not under experimental control, such as in cosmic inflation, where
small quantum fluctuations in the early Universe are responsible for structures
formation. Compared to previous studies restricted to and to a
fixed orientation of the pseudo-spin operators, allowing for
and optimizing the angular configuration leads to a completely new and rich
phenomenology. Two dual schemes of approximation are designed that allow for
comprehensive exploration of the squeezing parameters space. In particular, it
is found that Bell's inequality can be violated when the squeezing parameter
is large enough, , and the squeezing angle is
small enough, .Comment: 9 pages without appendices (38 pages total), 16 figures, matches
published version in Physical Review
Correlation Functions in Stochastic Inflation
Combining the stochastic and formalisms, we derive non
perturbative analytical expressions for all correlation functions of scalar
perturbations in single-field, slow-roll inflation. The standard, classical
formulas are recovered as saddle-point limits of the full results. This yields
a classicality criterion that shows that stochastic effects are small only if
the potential is sub-Planckian and not too flat. The saddle-point approximation
also provides an expansion scheme for calculating stochastic corrections to
observable quantities perturbatively in this regime. In the opposite regime, we
show that a strong suppression in the power spectrum is generically obtained,
and comment on the physical implications of this effect.Comment: 20 pages plus appendix, 4 figures, published in EPJC, typo corrected
in Eq. (3.37
Encyclopaedia Curvatonis
We investigate whether the predictions of single-field models of inflation
are robust under the introduction of additional scalar degrees of freedom, and
whether these extra fields change the potentials for which the data show the
strongest preference. We study the situation where an extra light scalar field
contributes both to the total curvature perturbations and to the reheating
kinematic properties. Ten reheating scenarios are identified, and all necessary
formulas allowing a systematic computation of the predictions for this class of
models are derived. They are implemented in the public library ASPIC, which
contains more than 75 single-field potentials. This paves the way for a
forthcoming full Bayesian analysis of the problem. A few representative
examples are displayed and discussed.Comment: 16 pages without appendices (total 55 pages), 93 figures. matches the
published version (JCAP
Recursive Stochastic Effects in Valley Hybrid Inflation
Hybrid Inflation is a two-field model where inflation ends by a tachyonic
instability, the duration of which is determined by stochastic effects and has
important observational implications. Making use of the recursive approach to
the stochastic formalism presented in Ref. [1], these effects are consistently
computed. Through an analysis of back-reaction, this method is shown to
converge in the valley but points toward an (expected) instability in the
waterfall. It is further shown that quasi-stationarity of the auxiliary field
distribution breaks down in the case of a short-lived waterfall. It is found
that the typical dispersion of the waterfall field at the critical point is
then diminished, thus increasing the duration of the waterfall phase and
jeopardizing the possibility of a short transition. Finally, it is found that
stochastic effects worsen the blue tilt of the curvature perturbations by an
order one factor when compared with the usual slow-roll contribution.Comment: 26 pages, 6 figure
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