188 research outputs found
Dark matter haloes in modified gravity and dark energy: interaction rate, small-, and large-scale alignment
We study the properties of dark matter haloes in a wide range of modified
gravity models, namely, , DGP, and interacting dark energy models. We
study the effects of modified gravity and dark energy on the internal
properties of haloes, such as the spin and the structural parameters. We find
that gravity enhance the median value of the Bullock spin parameter, but
could not detect such effects for DGP and coupled dark energy. also
yields a lower median sphericity and oblateness, while coupled dark energy has
the opposite effect. However, these effects are very small. We then study the
interaction rate of haloes in different gravity, and find that only strongly
coupled dark energy models enhance the interaction rate. We then quantify the
enhancement of the alignment of the spins of interacting halo pairs by modified
gravity. Finally, we study the alignment of the major axes of haloes with the
large-scale structures. The alignment of the spins of interacting pairs of
haloes in DGP and coupled dark energy models show no discrepancy with GR, while
shows a weaker alignment. Strongly coupled dark energy shows a stronger
alignment of the halo shape with the large-scale structures.Comment: 11 pages, 6 figures, MNRAS Accepte
High-order Harmonic Generation and Dynamic Localization in a driven two-level system, a non-perturbative solution using the Floquet-Green formalism
We apply the Floquet-Green operator formalism to the case of a
harmonically-driven two-level system. We derive exact expressions for the
quasi-energies and the components of the Floquet eigenstates with the use of
continued fractions. We study the avoided crossings structure of the
quasi-energies as a function of the strength of the driving field and give an
interpretation in terms of resonant multi-photon processes. From the Floquet
eigenstates we obtain the time-evolution operator. Using this operator we study
Dynamic Localization and High-order Harmonic Generation in the non-perturbative
regime
Two-photon double ionization of neon using an intense attosecond pulse train
We present the first demonstration of two-photon double ionization of neon
using an intense extreme ultraviolet (XUV) attosecond pulse train (APT) in a
photon energy regime where both direct and sequential mechanisms are allowed.
For an APT generated through high-order harmonic generation (HHG) in argon we
achieve a total pulse energy close to 1 J, a central energy of 35 eV and a
total bandwidth of eV. The APT is focused by broadband optics in a
neon gas target to an intensity of Wcm. By tuning
the photon energy across the threshold for the sequential process the double
ionization signal can be turned on and off, indicating that the two-photon
double ionization predominantly occurs through a sequential process. The
demonstrated performance opens up possibilities for future XUV-XUV pump-probe
experiments with attosecond temporal resolution in a photon energy range where
it is possible to unravel the dynamics behind direct vs. sequential double
ionization and the associated electron correlation effects
Influence of the medium length on high-order harmonic generation
We study high-order harmonic generation using a 110 fs Ti:sapphire laser loosely focused into a variable-length gas cell filled with neon or argon at 5 mbar pressure. The harmonic intensity is recorded as a function of the medium length, varying between 2 and 21 mm. Several cases are examined, the 17th and the 29th harmonic in argon, and the 29th and 51st harmonic in neon, at the same intensity 4 x 10(14) W cm(-2). We find that the length which maximizes the harmonic yield varies from 10 mm to more than 20 mm. We discuss the different effects affecting the photon yield of the high-order harmonics
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 ≥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
Rho-Nucleon Tensor Coupling and Charge-Exchange Resonances
The Gamow-Teller resonances are discussed in the context of a self-consistent
RPA, based on the relativistic mean field theory. We inquire on the possibility
of substituting the phenomenological Landau-Migdal force by a microscopic
nucleon-nucleon interaction generated from the rho-nucleon tensor coupling. The
effect of this coupling turns out to be very small when the short range
correlations are not taken into account, but too large when these correlations
are simulated by the simple extraction of the contact terms from the resulting
nucleon-nucleon interaction.Comment: 15 pages, LaTeX, 2 figures; extended text, improved figures, new
references added, the version appearing in Phys.Lett.
- …