5,591 research outputs found
The Effect of Repetitive Feedings on the Acceptability of Selected Metabolic Diets
Effect of repetitive feeding over extended periods of time on acceptability of selected metabolic diet
Strong Gravitational Lensing and Dark Energy Complementarity
In the search for the nature of dark energy most cosmological probes measure
simple functions of the expansion rate. While powerful, these all involve
roughly the same dependence on the dark energy equation of state parameters,
with anticorrelation between its present value w_0 and time variation w_a.
Quantities that have instead positive correlation and so a sensitivity
direction largely orthogonal to, e.g., distance probes offer the hope of
achieving tight constraints through complementarity. Such quantities are found
in strong gravitational lensing observations of image separations and time
delays. While degeneracy between cosmological parameters prevents full
complementarity, strong lensing measurements to 1% accuracy can improve
equation of state characterization by 15-50%. Next generation surveys should
provide data on roughly 10^5 lens systems, though systematic errors will remain
challenging.Comment: 7 pages, 5 figure
The Limits of Quintessence
We present evidence that the simplest particle-physics scalar-field models of
dynamical dark energy can be separated into distinct behaviors based on the
acceleration or deceleration of the field as it evolves down its potential
towards a zero minimum. We show that these models occupy narrow regions in the
phase-plane of w and w', the dark energy equation-of-state and its
time-derivative in units of the Hubble time. Restricting an energy scale of the
dark energy microphysics limits how closely a scalar field can resemble a
cosmological constant. These results, indicating a desired measurement
resolution of order \sigma(w')\approx (1+w), define firm targets for
observational tests of the physics of dark energy.Comment: 4 pages, 2 figure
Comparison of organoleptic acceptability of liquid and fresh diets
Organoleptic acceptability of liquid and fresh diets for space flight feedin
Constraining Modified Gravity with Euclid
Future proposed satellite missions as Euclid can offer the opportunity to
test general relativity on cosmic scales through mapping of the galaxy weak
lensing signal. In this paper we forecast the ability of these experiments to
constrain modified gravity scenarios as those predicted by scalar-tensor and
theories. We found that Euclid will improve constraints expected from
the PLANCK satellite on these modified gravity models by two orders of
magnitude. We discuss parameter degeneracies and the possible biases introduced
by modified gravity
Observational Bounds on Cosmic Doomsday
Recently it was found, in a broad class of models, that the dark energy
density may change its sign during the evolution of the universe. This may lead
to a global collapse of the universe within the time t_c ~ 10^{10}-10^{11}
years. Our goal is to find what bounds on the future lifetime of the universe
can be placed by the next generation of cosmological observations. As an
example, we investigate the simplest model of dark energy with a linear
potential V(\phi) =V_0(1+\alpha\phi). This model can describe the present stage
of acceleration of the universe if \alpha is small enough. However, eventually
the field \phi rolls down, V(\phi) becomes negative, and the universe
collapses. The existing observational data indicate that the universe described
by this model will collapse not earlier than t_c > 10 billion years from the
present moment. We show that the data from SNAP and Planck satellites may
extend the bound on the "doomsday" time to t_c > 40 billion years at the 95%
confidence level.Comment: 11 pages, 6 figures, revtex
Multiple imaging by gravitational waves
Gravitational waves act like lenses for the light propagating through them.
This phenomenon is described using the vector formalism employed for ordinary
gravitational lenses, which was proved to be applicable also to a
non-stationary spacetime, with the appropriate modifications. In order to have
multiple imaging, an approximate condition analogous to that for ordinary
gravitational lenses must be satisfied. Certain astrophysical sources of
gravitational waves satisfy this condition, while the gravitational wave
background, on average, does not. Multiple imaging by gravitational waves is,
in principle, possible, but the probability of observing such a phenomenon is
extremely low.Comment: 23 pages, LaTeX, no figures, to appear in Int. J. Mod. Phys.
Quinstant Dark Energy Predictions for Structure Formation
We explore the predictions of a class of dark energy models, quinstant dark
energy, concerning the structure formation in the Universe, both in the linear
and non-linear regimes. Quinstant dark energy is considered to be formed by
quintessence and a negative cosmological constant. We conclude that these
models give good predictions for structure formation in the linear regime, but
fail to do so in the non-linear one, for redshifts larger than one.Comment: 9 pages, 14 figures, "Accepted for publication in Astrophysics &
Space Science
The biochemical, physiological, and metabolic evaluation of human subjects in a life support systems evaluator and on a liquid food diet Final report, 12 Jun. 1964 - 23 Feb. 1965
Biochemical, physiological, and metabolic analysis of subjects in life support system on liquid food diets during space environment simulatio
Reducing Zero-point Systematics in Dark Energy Supernova Experiments
We study the effect of filter zero-point uncertainties on future supernova
dark energy missions. Fitting for calibration parameters using simultaneous
analysis of all Type Ia supernova standard candles achieves a significant
improvement over more traditional fit methods. This conclusion is robust under
diverse experimental configurations (number of observed supernovae, maximum
survey redshift, inclusion of additional systematics). This approach to
supernova fitting considerably eases otherwise stringent mission calibration
requirements. As an example we simulate a space-based mission based on the
proposed JDEM satellite; however the method and conclusions are general and
valid for any future supernova dark energy mission, ground or space-based.Comment: 30 pages,8 figures, 5 table, one reference added, submitted to
Astroparticle Physic
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