3,597 research outputs found
Gravitino Production After Inflation
We investigate the production of gravitinos in a cosmological background.
Gravitinos can be produced during preheating after inflation due to a combined
effect of interactions with an oscillating inflaton field and absence of
conformal invariance. In order to get insight on conformal properties of
gravitino we reformulate phenomenological supergravity in SU(2,2|1)-symmetric
way. The Planck mass and F- and D-terms appear via the gauge-fixed value of a
superfield that we call conformon. We find that in general the probability of
gravitino production is not suppressed by the small gravitational coupling.
This may lead to a copious production of gravitinos after inflation. Efficiency
of the new non-thermal mechanism of gravitino production is very sensitive to
the choice of the underlying theory. This may put strong constraints on certain
classes of inflationary models.Comment: 18 pages, v2: the version to be published in Phys. Rev.D; v3:
matching notations with longer paper hep-th/000617
Patterns and persistence of behavioural and psychological symptoms in those with cognitive impairment: the importance of apathy.
OBJECTIVE: To study the stability and emergence of a range of behavioural and psychological symptoms (BPS), their association with mortality and the effect of covariates on these transitions in a population-based study of cognitively impaired older people with a long follow-up period and large sample size, with a particular focus on apathy. METHODS: Data were from a population-based, longitudinal cohort study of ageing. Interviews were conducted at 0, 2, 6, 8 and 10 years with 3626 participants aged 65+. The persistence of 11 BPS and their association with mortality in those with cognitive impairment (MMSE 25 or below) was investigated using multi-state models, allowing us to take into account estimations of the probability of transitions that occurred in the time between interviews. RESULTS: Most BPS were persistent. Apathy was one of the most stable symptoms; in those with apathy, the probability of still having apathy after 1 year is 62%. Apathy, sleep problems, depression, irritability and wandering were most likely to develop. BPS are associated with mortality; in those with apathy, mortality is 3.1 times more likely than in those without apathy. Low cognitive function and dementia were associated with emergence of new symptoms. CONCLUSIONS: This population-based, multi-centre study with a follow-up period of 10 years showed that BPS are associated with mortality and most symptoms are persistent. Apathy was characterised by a high prevalence, a high persistence and a strong association with mortality, and has a negative impact on disability, management of other disease and caregiver burden.RvdL received a studentship from the National Institute for Health Research (NIHR) and the Collaborations for Leadership in Applied Health Research and Care (CLAHRC) for Cambridgeshire & Peterborough.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/gps.446
Quantum Cosmology and Higher-Order Lagrangian Theories
In this paper the quantum cosmological consequences of introducing a term
cubic in the Ricci curvature scalar into the Einstein--Hilbert action are
investigated. It is argued that this term represents a more generic
perturbation to the action than the quadratic correction usually considered. A
qualitative argument suggests that there exists a region of parameter space in
which neither the tunneling nor the no-boundary boundary conditions predict an
epoch of inflation that can solve the horizon and flatness problems of the big
bang model. This is in contrast to the --theory.Comment: 13 pages, LaTeX, preprint FERMILAB-Pub-94/XXX-A, March 199
Recycling universe
If the effective cosmological constant is non-zero, our observable universe
may enter a stage of exponential expansion. In such case, regions of it may
tunnel back to the false vacuum of an inflaton scalar field, and inflation with
a high expansion rate may resume in those regions. An ``ideal'' eternal
observer would then witness an infinite succession of cycles from false vacuum
to true, and back. Within each cycle, the entire history of a hot universe
would be replayed. If there were several minima of the inflaton potential, our
ideal observer would visit each one of these minima with a frequency which
depends on the shape of the potential. We generalize the formalism of
stochastic inflation to analyze the global structure of the universe when this
`recycling' process is taken into account.Comment: 43 pages, 10 figure
The burden of proof: the current state of atrial fibrillation prevention and treatment trials
Atrial fibrillation (AF) is an age-related arrhythmia of enormous socioeconomic significance. In recent years, our understanding of the basic mechanisms that initiate and perpetuate AF has evolved rapidly, catheter ablation of AF has progressed from concept to reality, and recent studies suggest lifestyle modification may help prevent AF recurrence. Emerging developments in genetics, imaging, and informatics also present new opportunities for personalized care. However, considerable challenges remain. These include a paucity of studies examining AF prevention, modest efficacy of existing antiarrhythmic therapies, diverse ablation technologies and practice, and limited evidence to guide management of high-risk patients with multiple comorbidities. Studies examining the long-term effects of AF catheter ablation on morbidity and mortality outcomes are not yet completed. In many ways, further progress in the field is heavily contingent on the feasibility, capacity, and efficiency of clinical trials to incorporate the rapidly evolving knowledge base and to provide substantive evidence for novel AF therapeutic strategies. This review outlines the current state of AF prevention and treatment trials, including the foreseeable challenges, as discussed by a unique forum of clinical trialists, scientists, and regulatory representatives in a session endorsed by the Heart Rhythm Society at the 12th Global CardioVascular Clinical Trialists Forum in Washington, DC, December 3–5, 2015
Origin Of The Far Off-Axis GRB171205A
We show that observed properties of the low luminosity GRB171205A and its
afterglow, like those of most other low-luminosity (LL) gamma ray bursts (GRBs)
associate with a supernova (SN), indicate that it is an ordinary SN-GRB, which
was produced by inverse Compton scattering of glory light by a highly
relativistic narrowly collimated jet ejected in a supernova explosion and
viewed from a far off-axis angle. As such, VLA/VLBI follow-up radio
observations of a superluminal displacement of its bright radio afterglow from
its parent supernova, will be able to test clearly whether it is an ordinary
SN-GRB viewed from far off-axis or it belongs to a distinct class of GRBs,
which are different from ordinary GRBs, and cannot be explained by standard
fireball models of GRBs as ordinary GRBsComment: 5 pages, 6 figures, updated data in Fig. 3, Corrected GRB angular
distance used in Fig.
KKF-Model Platform Coupling : summary report KKF01b
Nederland bereidt zich voor op een sneller stijgende zeespiegel en een veranderend klimaat. Hiervoor is het Deltaprogramma gestart. Dit deltaprogramma voorziet een serie beslissingen die grote gevolgen zullen hebben voor het beheer van het water in Nederland. Om deze beslissingen zorgvuldig te nemen is informatie nodig over hoe het klimaat en de stijgende zeespiegel dit waterbeheer zullen beïnvloeden. De modellen die de gevolgen van klimaatverandering berekenen zullen daarom met dezelfde klimaat forcering en gekoppeld aan elkaar moeten worden gebruikt. In dit onderzoek is gekeken naar het linken van hydrologische en hydrodynamische modellen – en daaraan gekoppelde modellen die de ontwikkelingen in natuur en landgebruik modelleren -- die het gebied van de Alpen tot en met de Noordzee inclusief Nederland beschrijven
Accidental Inflation in String Theory
We show that inflation in type IIB string theory driven by the volume modulus
can be realized in the context of the racetrack-based Kallosh-Linde model (KL)
of moduli stabilization. Inflation here arises through the volume modulus
slow-rolling down from a flat hill-top or inflection point of the scalar
potential. This situation can be quite generic in the landscape, where by
uplifting one of the two adjacent minima one can turn the barrier either to a
flat saddle point or to an inflection point supporting eternal inflation. The
resulting spectral index is tunable in the range of 0.93 < n_s < 1, and there
is only negligible production of primordial gravitational waves r < 10^{-6}.
The flatness of the potential in this scenario requires fine-tuning, which may
be justified taking into account the exponential reward by volume factors
preferring the regions of the universe with the maximal amount of slow-roll
inflation. This consideration leads to a tentative prediction of the spectral
index or depending on whether the
potential has a symmetry phi -> - phi or not.Comment: 15 pages, 6 figures, LaTeX, uses RevTex
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