1,166 research outputs found
A non-Gaussian landscape
Primordial perturbations with wavelengths greater than the observable universe shift the effective background fields in our observable patch from their global averages over the inflating space. This leads to a landscape picture where the properties of our observable patch depend on its location and may significantly differ from the expectation values predicted by the underlying fundamental inflationary model. We show that if multiple fields are present during inflation, this may happen even if our horizon exit would be preceded by only a few e-foldings of inflation. Non-Gaussian statistics are especially affected: for example models of local non-Gaussianity predicting |f_NL|>> 10 over the entire inflating volume can have a probability up to a few tens of percent to generate a non-detectable bispectrum in our observable patch |fNL^{obs.}|<10. In this work we establish systematic connections between the observable local properties of primordial perturbations and the global properties of the inflating space which reflect the underlying high energy physics. We study in detail the implications of both a detection and non-detection of primordial non-Gaussianity by Planck, and discover novel ways of characterising the naturalness of different observational configurations
Scale-Dependent Non-Gaussianity as a Generalization of the Local Model
We generalize the local model of primordial non-Gaussianity by promoting the
parameter fNL to a general scale-dependent function fNL(k). We calculate the
resulting bispectrum and the effect on the bias of dark matter halos, and thus
the extent to which fNL(k) can be measured from the large-scale structure
observations. By calculating the principal components of fNL(k), we identify
scales where this form of non-Gaussianity is best constrained and estimate the
overlap with previously studied local and equilateral non-Gaussian models.Comment: Accepted to JCAP. 22 pages, 4 figure
Valuation study for a preference-based quality of life measure for dental caries (Dental Caries Utility Index - DCUI) among Australian adolescents - study protocol.
IntroductionA new health state classification system has been developed for dental caries - Dental Caries Utility Index (DCUI) to facilitate the assessment of oral health interventions in the cost-utility analysis (CUA). This paper reports the protocol for a valuation study, which aims to generate a preference-based algorithm for the classification system for the DCUI.Methods and analysisDiscrete choice experiments (DCEs) will be conducted to value health states generated by the DCUI classification system and preferences for these health states will be modelled to develop a utility algorithm. DCEs produce utility values on a latent scale and these values will be anchored into the full health-dead scale to calculate the quality-adjusted life years in CUA. There is no previous evidence for the most suitable anchoring method for dental caries health state valuation. Hence, we will first conduct pilot studies with two anchoring approaches; DCE including duration attribute and DCE anchoring to worst heath state in Visual Analogue Scale. Based on the pilot studies, the most suitable anchoring method among two approaches will be used in the main valuation survey, which will be conducted as an online survey among a representative sample of 2000 adults from the Australian general population. Participants will be asked to complete a set of DCE choice tasks along with anchoring tasks, basic social-demographic questions, DCUI, a generic preference-based measure and oral health quality of life instrument.Ethics and disseminationEthical approval for this study was obtained from the Human Research Ethics Committee, Griffith University (reference number HREC/2019/550). The generated algorithm will facilitate the use of the new dental caries preference-based measure in economic evaluations of oral health interventions. The results will be disseminated through journal articles and professional conferences
The Trispectrum in the Multi-brid Inflation
The trispectrum is at least as important as the bispectrum and its size can
be characterized by two parameters and . In this short
paper, we focus on the Multi-brid inflation, in particular the two-brid
inflation model in arXiv.0805.0974, and find that is always
positive and roughly equals to for the low scale
inflation, but can be negative or positive and its order of magnitude
can be the same as that of or even largerComment: 12 pages; minor correction, refs added; further refs added, version
for publication in JCA
Linearization of nonlinear connections on vector and affine bundles, and some applications
A linear connection is associated to a nonlinear connection on a vector
bundle by a linearization procedure. Our definition is intrinsic in terms of
vector fields on the bundle. For a connection on an affine bundle our procedure
can be applied after homogenization and restriction. Several applications in
Classical Mechanics are provided
Non-Gaussian bubbles in the sky
We point out a possible generation mechanism of non-Gaussian bubbles in the
sky due to bubble nucleation in the early universe. We consider a curvaton
scenario for inflation and assume that the curvaton field phi, whose energy
density is subdominant during inflation but which is responsible for the
curvature perturbation of the universe, is coupled to another field sigma which
undergoes false vacuum decay through quantum tunneling. For this model, we
compute the skewness of the curvaton fluctuations due to its interaction with
sigma during tunneling, that is, on the background of an instanton solution
that describes false vacuum decay. We find that the resulting skewness of the
curvaton can become large in the spacetime region inside the bubble. We then
compute the corresponding skewness in the statistical distribution of the
cosmic microwave background (CMB) temperature fluctuations. We find a
non-vanishing skewness in a bubble-shaped region in the sky. It can be large
enough to be detected in the near future, and if detected it will bring us
invaluable information about the physics in the early universe.Comment: 6 pages, 6 figure
The Berwald-type linearisation of generalised connections
We study the existence of a natural `linearisation' process for generalised
connections on an affine bundle. It is shown that this leads to an affine
generalised connection over a prolonged bundle, which is the analogue of what
is called a connection of Berwald type in the standard theory of connections.
Various new insights are being obtained in the fine structure of affine bundles
over an anchored vector bundle and affineness of generalised connections on
such bundles.Comment: 25 page
Beauty is Distractive: Particle production during multifield inflation
We consider a two-dimensional model of inflation, where the inflationary
trajectory is "deformed" by a grazing encounter with an Extra Species/Symmetry
Point (ESP) after the observable cosmological scales have left the Hubble
radius. The encounter entails a sudden production of particles, whose
backreaction causes a bending of the trajectory and a temporary decrease in
speed, both of which are sensitive to initial conditions. This "modulated"
effect leads to an additional contribution to the curvature perturbation, which
can be dominant if the encounter is close. We compute associated
non-Gaussianities, the bispectrum and its scale dependence as well as the
trispectrum, which are potentially detectable in many cases. In addition, we
consider a direct modulation of the coupling to the light field at the ESP via
a modulaton field, a mixed scenario whereby the modulaton is identified with a
second inflaton, and an extended Extra Species Locus (ESL); all of these
scenarios lead to similar additional contributions to observables. We conclude
that inflaton interactions throughout inflation are strongly constrained if
primordial non-Gaussianities remain unobserved in current experiments such as
PLANCK. If they are observed, an ESP encounter leaves additional signatures on
smaller scales which may be used to identify the model.Comment: 41 pages, 6 figures; v2: references and minor clarifications added,
conclusions unchange
- …