116 research outputs found
Nongaussianity from Tachyonic Preheating in Hybrid Inflation
In a previous work we showed that large nongaussianities and
nonscale-invariant distortions in the CMB power spectrum can be generated in
hybrid inflation models, due to the contributions of the tachyon (waterfall)
field to the second order curvature perturbation. Here we clarify, correct, and
extend those results. We show that large nongaussianity occurs only when the
tachyon remains light throughout inflation, whereas n=4 contamination to the
spectrum is the dominant effect when the tachyon is heavy. We find constraints
on the parameters of warped-throat brane-antibrane inflation from
nongaussianity. For F-term and D-term inflation models from supergravity, we
obtain nontrivial constraints from the spectral distortion effect. We also
establish that our analysis applies to complex tachyon fields.Comment: 16 pages, 2 figures. Comments added to introductio
On a homeomorphism between orbit spaces of linear systems and matrix polynomials
AbstractThe orbit space of controllable systems under system similarity and the orbit space of matrix polynomials with determinant degree equal to the order of the state matrix under right equivalence are proved to be homeomorphic when the quotient compactâopen topology is considered in the latter. As a consequence, the variation of the finite and left WienerâHopf structures under small perturbations of matrix polynomials with fixed degree for their determinants is described
Local WienerâHopf factorization and indices over arbitrary fields
AbstractIn this paper, a generalization to arbitrary fields of the usual WienerâHopf equivalence of complex valued rational matrix functions is given and the left local WienerâHopf factorization indices defined in our previous work [A. Amparan, S. Marcaida, I. Zaballa, Local realizations and local polynomial matrix representations of systems, Linear Algebra Appl. 425 (2007) 757â775] are proved to form a complete system of invariants for this equivalence relation. For the case when the field is algebraically closed a reduced form of a controllable matrix pair under the feedback equivalence is presented for which the controllability indices can be written as sums of the local controllability indices [A. Amparan, S. Marcaida, I. Zaballa, On the existence of linear systems with prescribed invariants for system similarity, Linear Algebra Appl. 413 (2006) 510â533]
Fields Annihilation and Particles Creation in DBI inflation
We consider a model of DBI inflation where two stacks of mobile branes are
moving ultra relativistically in a warped throat. The stack closer to the tip
of the throat is annihilated with the background anti-branes while inflation
proceeds by the second stack. The effects of branes annihilation and particles
creation during DBI inflation on the curvature perturbations power spectrum and
the scalar spectral index are studied. We show that for super-horizon scales,
modes which are outside the sound horizon at the time of branes collision, the
spectral index has a shift to blue spectrum compared to the standard DBI
inflation. For small scales the power spectrum approaches to its background DBI
inflation value with the decaying superimposed oscillatory modulations.Comment: First revision: minor changes, the background spectral index is
corrected, new references are added. Second revision: minor changes, new
references are added, accepted for publication in JCA
Non-Gaussianities in two-field inflation
We study the bispectrum of the curvature perturbation on uniform energy
density hypersurfaces in models of inflation with two scalar fields evolving
simultaneously. In the case of a separable potential, it is possible to compute
the curvature perturbation up to second order in the perturbations, generated
on large scales due to the presence of non-adiabatic perturbations, by
employing the -formalism, in the slow-roll approximation. In this
case, we provide an analytic formula for the nonlinear parameter . We
apply this formula to double inflation with two massive fields, showing that it
does not generate significant non-Gaussianity; the nonlinear parameter at the
end of inflation is slow-roll suppressed. Finally, we develop a numerical
method for generic two-field models of inflation, which allows us to go beyond
the slow-roll approximation and confirms our analytic results for double
inflation.Comment: 29 pages, 6 figures. v2, comparison with previous estimates. v3, JCAP
version; Revisions based on Referee's comment, corrected typos, added few eqs
and refs, conclusions unchange
Parental willingness to have children vaccinated against COVID-19 in Geneva, Switzerland: a cross-sectional population-based study.
We aimed to examine factors associated with parental willingness to vaccinate their children against COVID-19.
We surveyed adults included in a digital longitudinal cohort study composed of participants in previous SARS-CoV-2 serosurveys conducted in Geneva, Switzerland. In February 2022, an online questionnaire collected information on COVID-19 vaccination acceptance, parental willingness to vaccinate their children aged â„5 years and reasons for vaccination preference. We used multivariable logistic regression to assess the demographic, socioeconomic and health-related factors associated with being vaccinated and with parental intention to vaccinate their children.
We included 1,383 participants (56.8% women; 69.3% aged 35-49 years). Parental willingness to vaccinate their children increased markedly with the child's age: 84.0%, 60.9% and 21.2%, respectively, for parents of adolescents aged 16-17 years, 12-15 years and 5-12 years. For all child age groups, unvaccinated parents more frequently indicated not intending to vaccinate their children than vaccinated parents. Refusal to vaccine children was associated with having a secondary education (1.73; 1.18-2.47) relative to a tertiary education and with middle (1.75; 1.18-2.60) and low (1.96; 1.20-3.22) household income relative to high income. Refusal to vaccine their children was also associated with only having children aged 12-15 years (3.08; 1.61-5.91), aged 5-11 years (19.77; 10.27-38.05), or in multiple age groups (6.05; 3.22-11.37), relative to only having children aged 16-17 years.
Willingness to vaccinate children was high for parents of adolescents aged 16-17 years but decreased significantly with decreasing child age. Unvaccinated, socioeconomically disadvantaged parents and those with younger children were less likely to be willing to vaccinate their children. These results are important for vaccination programs and developing communication strategies to reach vaccine-hesitant groups, both in the context of COVID-19 and in the prevention of other diseases and future pandemics
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