368 research outputs found
Inflation and Reheating in Spontaneously Generated Gravity
Inflation is studied in the context of induced gravity (IG) , where is the Ricci scalar, a scalar field and a
dimensionless constant, and diverse symmetry-breaking potentials
are considered. In particular we compared the predictions for Landau-Ginzburg
(LG) and Coleman-Weinberg (CW) type potentials and their possible
generalizations with the most recent data. We find that large field inflation
generally leads to fewer constraints on the parameters and the shape of the
potential whereas small field inflation is more problematic and, if viable,
implies more constraints, in particular on the parameter . We also
examined the reheating phase and obtained an accurate analytical solution for
the dynamics of inflaton and the Hubble parameter by using a multiple scale
analysis (MSA). The solutions were then used to study the average expansion of
the Universe, the average equation of state for the scalar field and both the
perturbative and resonant decays of the inflaton field.Comment: 15 pages, 10 figures, to be published in Phys. Rev.
Radion Induced Spontaneous Baryogenesis
We describe a possible scenario for the baryogenesis arising when matter is
added on the branes of a Randall-Sundrum model with a radion stabilizing
potential. We show that the radion field can naturally induce spontaneous
baryogenesis when the cosmological evolution for the matter on the branes is
taken into account.Comment: LaTeX 2e, 8 pages and no figures, minor corrections to match version
to appear in MPL
The networked researcher, the editorial manager, and the traveller: The profiles of international political scientists and the determinants of internationalisation
This is the final version. Available on open access from Palgrave Macmillan via the DOI in this recordThe concept of internationalisation, when referring to the work of social scientists within academic institutions, takes on different meanings and involves different activities. This contribution aims to shed light on the international activities of political scientists across Europe and to investigate the various meanings and practices of internationalisation. The analysis relies on the PROSEPS survey, involving some 1,800 political scientists across 37 European countries. We identify three distinct profiles of international scholars : the networked researcher, the editorial manager, and the traveller. These profiles differ according to 1) the building of international research networks, 2) the involvement in the activities of the international publishing industry, 3) the research and teaching exchanges with foreign academic institutions. Determinants such as gender, family status, career stage, availability of institutional and financial support, and geographical location, are considered as potential drivers or inhibitors of internationalisation. Our analysis shows that the internationalisation of academic practices follows contrasting paths according to the type of international profile.European Commissio
Direct electrification of Rh/Al2O3 washcoated SiSiC foams for methane steam reforming: An experimental and modelling study
Electrified methane steam reforming (eMSR) is a promising concept for low-carbon hydrogen production. We investigate an innovative eMSR reactor where SiSiC foams, coated with Rh/Al2O3 catalyst, act as electrical resistances to generate the reaction heat via the Joule effect. The novel system was studied at different temperatures, space velocities, operating pressures and catalyst loadings. Thanks to efficient heating, active catalyst and optimal substrate geometry, complete methane conversions were observed even at a high space velocity of 200000 Nl/h/kgcat. A specific energy demand as low as 1.24 kWh/Nm3H2, with an unprecedented energy efficiency of 81%, was achieved on a washcoated foam with catalyst density of 86.3 g/L (GHSV = 150000 Nl/h/kgcat, S/C = 4.1, ambient pressure). A mathematical model was validated against measured performance indicators and used to design an intensified eMSR unit for small scale H2 production.(c) 2023 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/)
Dark Energy, Induced Gravity and Broken Scale Invariance
We study the cosmological evolution of an induced gravity model with a
self-interacting scalar field and in the presence of matter and
radiation. Such model leads to Einstein Gravity plus a cosmological constant as
a stable attractor among homogeneous cosmologies and is therefore a viable
dark-energy (DE) model for a wide range of scalar field initial conditions and
values for its positive coupling to the Ricci curvature .Comment: 6 pages, 5 figures, 1 table: final version accepted for publication
in PL
Inflation and Reheating in Induced Gravity
Inflation is studied in the context of induced gravity (IG) , where is the Ricci scalar, a scalar field and a
dimensionless constant. We study in detail cosmological perturbations in IG and
examine both a Landau-Ginzburg (LG) and a Coleman-Weinberg (CW) potential toy
models for small field and large field (chaotic) inflation and find that small
field inflationary models in IG are constrained to by WMAP 5 yrs data. Finally we describe the regime of coherent
oscillations in induced gravity by an analytic approximation, showing how the
homogeneous inflaton can decay in its short-scale fluctuations when it
oscillates around a non-zero value .Comment: 5 pages, 2 figure
Fatal poisoning of four workers in a farm: Distribution of hydrogen sulfide and thiosulfate in 10 different biological matrices
We evaluate the distribution of sulfide and thiosulfate (TS) in biological samples of four dairy farmers died inside a pit connected to a manure lagoon. Autopsies were performed 4 days later. Toxicological analyses of sulfide and TS were made using an extractive alkylation technique combined with gas chromatography/mass spectrometry (GC/MS). Autopsies revealed: multiorgan congestion; pulmonary edema; manure inside distal airways of three of the four victims. Sulfide concentrations were cardiac blood: 0.5–3.0 μg/mL, femoral blood: 0.5–1.2 μg/mL, bile: <0.1–2.2 μg/mL; liver 2.8–8.3 μg/g, lung: 5.0–9.4 μg/g, brain: 2.7–13.9 μg/g, spleen: 3.3–6.3 μg/g, fat: <0.1–1.5 μg/g, muscle: 2.6–3.5 μg/g. TS concentrations were cardiac blood: 2.1–4.9 μg/mL, femoral blood: 2.1–2.3 μg/mL, bile: 2.5–4.4 μg/mL, urine: <0.5–1.8 μg/mL; liver <0.5–2.6, lung: 2.8–5.4 μg/g, brain: <0.5–1.9 μg/g, spleen: 1.2–2.9 μg/g, muscle: <0.5–5.6 μg/g. The cause of death was assessed to be acute poisoning by hydrogen sulfide (H2S) for all the victims. Manure inhalation contributed to the death of three subjects. The measurement of sulfide and TS concentrations in biological samples contributed to better understand the sequence of the events. Subjects 3 provided the highest concentration of sulfide in brain, thus, supporting the hypothesis of a rapid loss of consciousness and respiratory depression. One by one, the other farmers entered the pit in attempts to rescue the coworkers but collapsed. Despite the rapid death, subject 3 was the only one with TS detectable in urine. This could be due to differences in metabolism of H2S
The Inflaton and Time in the Matter-Gravity System
The emergence of time in the matter-gravity system is addressed within the
context of the inflationary paradigm. A quantum minisuperspace-homogeneous
minimally coupled inflaton system is studied with suitable initial conditions
leading to inflation and the system is approximately solved in the limit for
large scale factor. Subsequently normal matter (either non homogeneous inflaton
modes or lighter matter) is introduced as a perturbation and it is seen that
its presence requires the coarse averaging of a gravitational wave function
(which oscillates at trans-Planckian frequencies) having suitable initial
conditions. Such a wave function, which is common for all types of normal
matter, is associated with a ``time density'' in the sense that its modulus is
related to the amount of time spent in a given interval (or the rate of flow of
time). One is then finally led to an effective evolution equation (Schroedinger
Schwinger-Tomonaga) for ``normal'' matter. An analogy with the emergence of a
temperature in statistical mechanics is also pointed out.Comment: 14 pages, late
Energy-Momentum Tensor of Cosmological Fluctuations during Inflation
We study the renormalized energy-momentum tensor (EMT) of cosmological scalar
fluctuations during the slow-rollover regime for chaotic inflation with a
quadratic potential and find that it is characterized by a negative energy
density which grows during slow-rollover. We also approach the back-reaction
problem as a second-order calculation in perturbation theory finding no
evidence that the back-reaction of cosmological fluctuations is a gauge
artifact. In agreement with the results on the EMT, the average expansion rate
is decreased by the back-reaction of cosmological fluctuations.Comment: 19 pages, no figures.An appendix and references added, conclusions
unchanged, version accepted for publication in PR
Local representative democracy and protest politics:the case of the Five-star Movement
In recent years, protest politics has become a relevant phenomenon in various European countries. Italy has witnessed the rise of the Five-star Movement (M5S), an anti-establishment party, which, at the 2013 general election, obtained one-fourth of the total votes. However, the story of this ‘party-movement’ started at the local level, as a civic network aimed at changing administrative practices in municipal government. By using an original dataset on representation in 671 Italian municipalities from 2010 to 2014, this article aims to explain not only the subnational political success of the M5S but also the challenges and contradictions that a newly formed movement faces in multi-level electoral arenas
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