7,820 research outputs found
Fresh inflation: a warm inflationary model from a zero temperature initial state
A two-components mixture fluid which complies with the gamma law is
considered in the framework of inflation with finite temperature. The model is
developed for a quartic scalar potential without symmetry breaking. The
radiation energy density is assumed to be zero when inflation starts and
remains below the GUT temperature during the inflationary stage. Furthermore,
provides the necessary number of e-folds and sufficient radiation energy
density to GUT baryogenesis can take place near the minimum energetic
configuration.Comment: 11 pages, no figures, to be published in Phys. Rev.
The evolution of the universe from noncompact Kaluza-Klein theory
We develope a 5D mechanism inspired in the Campbell's theorem, to explain the
(neutral scalar field governed) evolution of the universe from a initially
inflationary expansion that has a change of phase towards a decelerated
expansion and thereinafter evolves towards the present day observed celerated
(quintessential) expansion.Comment: version accepted in Eur. Phys. J.
Constraints on deviations from CDM within Horndeski gravity
Recent anomalies found in cosmological datasets such as the low multipoles of
the Cosmic Microwave Background or the low redshift amplitude and growth of
clustering measured by e.g., abundance of galaxy clusters and redshift space
distortions in galaxy surveys, have motivated explorations of models beyond
standard CDM. Of particular interest are models where general
relativity (GR) is modified on large cosmological scales. Here we consider
deviations from CDM+GR within the context of Horndeski gravity, which
is the most general theory of gravity with second derivatives in the equations
of motion. We adopt a parametrization in which the four additional Horndeski
functions of time are proportional to the cosmological density of
dark energy . Constraints on this extended parameter space
using a suite of state-of-the art cosmological observations are presented for
the first time. Although the theory is able to accommodate the low multipoles
of the Cosmic Microwave Background and the low amplitude of fluctuations from
redshift space distortions, we find no significant tension with CDM+GR
when performing a global fit to recent cosmological data and thus there is no
evidence against CDM+GR from an analysis of the value of the Bayesian
evidence ratio of the modified gravity models with respect to CDM,
despite introducing extra parameters. The posterior distribution of these extra
parameters that we derive return strong constraints on any possible deviations
from CDM+GR in the context of Horndeski gravity. We illustrate how our
results can be applied to a more general frameworks of modified gravity models.Comment: 22 pages; 4 figures; 9 tables. The constraints have been revised to
match the precision required according to the recently released hi_class
pape
Heralded noiseless amplification and attenuation of non-gaussian states of light
We examine the behavior of non-Gaussian states of light under the action of
probabilistic noiseless amplification and attenuation. Surprisingly, we find
that the mean field amplitude may decrease in the process of noiseless
amplification -- or increase in the process of noiseless attenuation, a
counterintuitive effect that Gaussian states cannot exhibit. This striking
phenomenon could be tested with experimentally accessible non-Gaussian states,
such as single-photon added coherent states. We propose an experimental scheme,
which is robust with respect to the major experimental imperfections such as
inefficient single-photon detection and imperfect photon addition. In
particular, we argue that the observation of mean field amplification by
noiseless attenuation should be feasible with current technology
Extra force and extra mass from noncompact Kaluza-Klein theory in a cosmological model
Using the Hamilton-Jacobi formalism, we study extra force and extra mass in a
recently introduced noncompact Kaluza-Klein cosmological model. We examine the
inertial 4D mass of the inflaton field on a 4D FRW bulk in two examples.
We find that has a geometrical origin and antigravitational effects on a
non inertial 4D bulk should be a consequence of the motion of the fifth
coordinate with respect to the 4D bulk.Comment: final version to be published in EPJ
Effect of intraoperative constant rate infusion of lidocaine on short-term survival of dogs with septic peritonitis: 75 cases (2007-2011)
OBJECTIVE To investigate whether intraoperative administration of a lidocaine infusion to dogs with septic peritonitis was associated with short-term (48 hours) survival after surgery. DESIGN Retrospective case series. ANIMALS 75 dogs with septic peritonitis. PROCEDURES Medical records of dogs with septic peritonitis that underwent laparotomy between January 2007 and December 2011 at the Royal Veterinary College were reviewed. Select variables during the preoperative, intraoperative, and postoperative periods and short-term survival after surgery were compared between dogs that received an opioid only (group O; n = 33) and dogs that received lidocaine (50 \u3bcg/kg/min [22.7 \u3bcg/kg/min], IV; group L; 42) in addition to an opioid during surgery. RESULTS The proportion of dogs that survived for 48 hours after surgery was significantly greater for group L (35/42) than for group O (20/33). Intraoperative infusion of lidocaine increased the odds of short-term survival (OR, 8.77; 95% CI, 1.94 to 39.57). No significant differences were observed between the 2 treatment groups for variables assessed during the preoperative and postoperative periods. During the intraoperative period, more dogs in group L received an IV bolus of a synthetic colloid than did dogs in group O, but the number of IV boluses administered was not associated with short-term survival. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that IV infusion of lidocaine might improve the short-term survival of dogs with septic peritonitis. Prospective clinical trials are necessary to determine the efficacy of lidocaine as a supportive treatment for dogs with septic peritonitis
Warm inflation and scalar perturbations of the metric
A second-order expansion for the quantum fluctuations of the matter field was
considered in the framework of the warm inflation scenario. The friction and
Hubble parameters were expended by means of a semiclassical approach. The
fluctuations of the Hubble parameter generates fluctuations of the metric.
These metric fluctuations produce an effective term of curvature. The power
spectrum for the metric fluctuations can be calculated on the infrared sector.Comment: 10 pages, no figures, to be published in General Rel. and Gravitatio
Phantom cosmology with a decaying cosmological function induced from five-dimensional (5D) geometrical vacuum
Introducing a variable cosmological function in a geometrical
manner from a 5D Riemann-flat metric, we investigate the possibility of having
a geometrical criterion to choose a suitable cosmological function for every 4D dynamical hypersurface capable of generate phantom
cosmologies.Comment: final versio
Absolute proper motion of the Galactic open cluster M67
We derived the absolute proper motion (PM) of the old, solar-metallicity
Galactic open cluster M67 using observations collected with CFHT (1997) and
with LBT (2007). About 50 galaxies with relatively sharp nuclei allow us to
determine the absolute PM of the cluster. We find (mu_alpha
cos(delta),mu_delta)_J2000.0 = (-9.6+/-1.1,-3.7+/-0.8) mas/yr. By adopting a
line-of-sight velocity of 33.8+/-0.2 km/s, and assuming a distance of 815+/-50
pc, we explore the influence of the Galactic potential, with and without the
bar and/or spiral arms, on the galactic orbit of the cluster.Comment: 7 pages, 5 figures, and 3 tables. Published in Astronomy and
Astrophysics, Volume 513, id.A51
A Double White-Dwarf Cooling Sequence in {\omega} Centauri
We have applied our empirical-PSF-based photometric techniques on a large
number of calibration-related WFC3/UVIS UV-B exposures of the core of {\omega}
Cen, and found a well-defined split in the right part of the white-dwarf
cooling sequence (WDCS). The redder sequence is more populated by a factor of
~2. We can explain the separation of the two sequences and their number ratio
in terms of the He-normal and He-rich subpopulations that had been previously
identified along the cluster main sequence. The blue WDCS is populated by the
evolved stars of the He-normal component (~0.55 Msun CO-core DA objects) while
the red WDCS hosts the end-products of the He-rich population (~0.46 Msun
objects, ~10% CO-core and ~90% He-core WDs). The He-core WDs correspond to
He-rich stars that missed the central He-ignition, and we estimate their
fraction by analyzing the population ratios along the cluster horizontal
branch.Comment: 6 pages, 4 figures, accepted for publication in ApJ Letters. Fixed a
typo in the metadat
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