Nonequilibrium dynamics of quantum fields

The nonequilibrium effective equation of motion for a scalar background field in a thermal bath is studied numerically. This equation emerges from a microscopic quantum field theory derivation and it is suitable to a Langevin simulation on the lattice. Results for both the symmetric and broken phases are presented.Comment: To appear in the proceedings of 5th International Conference on Perspectives in Hadronic Physics: International Conference on Particle-Nucleus and Nucleus-Nucleus Scattering at Relativistic Energies, Trieste, Italy, 22-26 May 2006. V2:reference correcte

Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath

The effects of bulk viscosity are examined for inflationary dynamics in which dissipation and thermalization are present. A complete stability analysis is done for the background inflaton evolution equations, which includes both inflaton dissipation and radiation bulk viscous effects. Three representative approaches of bulk viscous irreversible thermodynamics are analyzed: the Eckart noncausal theory, the linear and causal theory of Israel-Stewart and a more recent nonlinear and causal bulk viscous theory. It is found that the causal theories allow for larger bulk viscosities before encountering an instability in comparison to the noncausal Eckart theory. It is also shown that the causal theories tend to suppress the radiation production due to bulk viscous pressure, because of the presence of relaxation effects implicit in these theories. Bulk viscosity coefficients derived from quantum field theory are applied to warm inflation model building and an analysis is made of the effects to the duration of inflation. The treatment of bulk pressure would also be relevant to the reheating phase after inflation in cold inflation dynamics and during the radiation dominated regime, although very little work in both areas has been done, the methodology developed in this paper could be extended to apply to these other problems.Comment: 27 pages, 14 figures, Published version JCA

Adaptation and validation of the Digital Health Literacy Instrument for Portuguese university students

Publisher Copyright: © 2022 Australian Health Promotion Association.Background: Health literacy is an important skill to deal with information and positively influences individual and community health. Information concerning health is available from a plethora of online resources. The concept of digital health literacy has gained prominence with the pandemic. The absence of valid tools to analyse digital literacy levels are scant. This study aims to translate, adapt and validate the Portuguese version of the Digital Health Literacy Instrument (DHLI) as used in the global COVID-HL Network. Methods: Participants were mostly students from social sciences, psychology, education and health sciences. The Portuguese version of the DHLI contained five dimensions each consisting of three items. An online survey with university students (n = 1815, 75.1% female, average age: 24.15 years) was administered to test the validity of the Portuguese version of the DHLI. Data were analysed using exploratory and confirmatory factor analysis. Pearson correlations were also studied. Results: Two items revealed symmetry and kurtosis problems. We chose to eliminate them from the analysis. Different exploratory factor analysis attempts were made, obtaining two possible models to be tested in the confirmatory factor analysis: a three-factor model and a four-factor model. A four-factor structure of the instrument (information searching, adding self-generated content, evaluating reliability, determining relevance) was supported by confirmatory factor analysis and had good internal consistency. Conclusions: The Portuguese version of the Digital Health Literacy Instrument met adequate psychometric criteria. Therefore, it can be confidently used in Portuguese students' assessment of digital health literacy. Representative studies are needed to shed light on different target groups and their COVID-19–related DHLI.publishersversionpublishe

Chaotic scalar fields as models for dark energy

We consider stochastically quantized self-interacting scalar fields as suitable models to generate dark energy in the universe. Second quantization effects lead to new and unexpected phenomena is the self interaction strength is strong. The stochastically quantized dynamics can degenerate to a chaotic dynamics conjugated to a Bernoulli shift in fictitious time, and the right amount of vacuum energy density can be generated without fine tuning. It is numerically observed that the scalar field dynamics distinguishes fundamental parameters such as the electroweak and strong coupling constants as corresponding to local minima in the dark energy landscape. Chaotic fields can offer possible solutions to the cosmological coincidence problem, as well as to the problem of uniqueness of vacua.Comment: 30 pages, 3 figures. Replaced by final version accepted by Phys. Rev.

Infrared Gas Phase Intensity Measurements, Polar Tensors, And Effective Charges Of Vinylidene Fluoride And Its Deuterated Modifications

All gas phase fundamental vibrational intensities for vinylidene fluoride and its deuterated modifications have been measured. Isotopic invariance, G sum rule, and quantum chemical information have been used in selecting preferred experimental values for the dipole moment derivatives and polar tensor elements of these molecules. The values of these intensity parameters are compared with those found for other molecules. The experimental values are interpreted in terms of electronic charge distortions occurring in these molecules for the various vibrations. © 1982 American Institute of Physics.7731099110

Opening the GATE : systems thinking from the global assistive technology alliance

Purpose: This paper describes international actions to collaborate in the assistive technology (AT) arena and provides an update of programmes supporting AT globally. Methods: The World Health Organisation (WHO) identifies the severe global uneven distribution of resources, expertise and extensive unmet need for AT, as well the optimistic substantial capability for innovations and developments in appropriate and sustainable AT design, development and delivery. Systems thinking and market shaping are identified as means to address these challenges and leverage the ingenuity and expertise of AT stakeholders. Results: This paper is a ‘call to action’, showcasing emerging AT networks as exemplars of a distributed, but integrated mechanism for addressing AT needs globally, and describing the Global Alliance of Assistive Technology Organisations (GAATO) as a vehicle to facilitate this global networking. Conclusion: Partners in this Global Alliance aim to advance the field of assistive technology by promoting shared research, policy advocacy, educating people and organisations within and outside the field, teaching, training and knowledge transfer by pulling together broad-based membership organisations

Flavor SU(3) breaking effects in the chiral unitary model for meson-baryon scatterings

We examine flavor SU(3) breaking effects on meson-baryon scattering amplitudes in the chiral unitary model. It turns out that the SU(3) breaking, which appears in the leading quark mass term in the chiral expansion, can not explain the channel dependence of the subtraction parameters of the model, which are crucial to reproduce the observed scattering amplitudes and resonance properties.Comment: RevTeX4, 4 pages, 3 figures, 2 table

Chiral dynamics of p-wave in K^- p and coupled states

We perform an evaluation of the p-wave amplitudes of meson-baryon scattering in the strangeness S=-1 sector starting from the lowest order chiral Lagrangians and introducing explicitly the Sigma^* field with couplings to the meson-baryon states obtained using SU(6) symmetry. The N/D method of unitarization is used, equivalent, in practice, to the use of the Bethe-Salpeter equation with a cut-off. The procedure leaves no freedom for the p-waves once the s-waves are fixed and thus one obtains genuine predictions for the p-wave scattering amplitudes, which are in good agreement with experimental results for differential cross sections, as well as for the width and partial decay widths of the Sigma^*(1385).Comment: LaTeX, 18 pages, 6 figure

Fine-Tuning Solution for Hybrid Inflation in Dissipative Chaotic Dynamics

We study the presence of chaotic behavior in phase space in the pre-inflationary stage of hybrid inflation models. This is closely related to the problem of initial conditions associated to these inflationary type of models. We then show how an expected dissipative dynamics of fields just before the onset of inflation can solve or ease considerably the problem of initial conditions, driving naturally the system towards inflation. The chaotic behavior of the corresponding dynamical system is studied by the computation of the fractal dimension of the boundary, in phase space, separating inflationary from non-inflationary trajectories. The fractal dimension for this boundary is determined as a function of the dissipation coefficients appearing in the effective equations of motion for the fields.Comment: 10 pages, 4 eps figures (uses epsf), Revtex. Replaced with version to match one in press Physical Review

Warming up for Planck

The recent Planck results and future releases on the horizon present a key opportunity to address a fundamental question in inflationary cosmology of whether primordial density perturbations have a quantum or thermal origin, i.e. whether particle production may have significant effects during inflation. Warm inflation provides a natural arena to address this issue, with interactions between the scalar inflaton and other degrees of freedom leading to dissipative entropy production and associated thermal fluctuations. In this context, we present relations between CMB observables that can be directly tested against observational data. In particular, we show that the presence of a thermal bath warmer than the Hubble scale during inflation decreases the tensor-to-scalar ratio with respect to the conventional prediction in supercooled inflation, yielding $r< 8|n_t|$, where $n_t$ is the tensor spectral index. Focusing on supersymmetric models at low temperatures, we determine consistency relations between the observables characterizing the spectrum of adiabatic scalar and tensor modes, both for generic potentials and particular canonical examples, and which we compare with the WMAP and Planck results. Finally, we include the possibility of producing the observed baryon asymmetry during inflation through dissipative effects, thereby generating baryon isocurvature modes that can be easily accommodated by the Planck data.Comment: 14 pages, 10 figures. Published in JCA