393 research outputs found
Extending the Coyote emulator to dark energy models with standard - parametrization of the equation of state
We discuss an extension of the Coyote emulator to predict non-linear matter
power spectra of dark energy (DE) models with a scale factor dependent equation
of state of the form w = w_0 + ( 1 - a )w_a . The extension is based on the
mapping rule between non-linear spectra of DE models with constant equation of
state and those with time varying one originally introduced in ref. [40]. Using
a series of N-body simulations we show that the spectral equivalence is
accurate to sub-percent level across the same range of modes and redshift
covered by the Coyote suite. Thus, the extended emulator provides a very
efficient and accurate tool to predict non-linear power spectra for DE models
with w_0 - w_a parametrization. According to the same criteria we have
developed a numerical code, and we have implemented in a dedicated module for
the CAMB code, that can be used in combination with the Coyote Emulator in
likelihood analyses of non-linear matter power spectrum measurements. All codes
can be found at https://github.com/luciano-casarini/PKequalComment: All codes can be found at https://github.com/luciano-casarini/PKequa
Tomographic weak lensing shear spectra from large N-body and hydrodynamical simulations
Forthcoming experiments will enable us to determine tomographic shear spectra
at a high precision level. Most predictions about them have until now been
biased on algorithms yielding the expected linear and non-linear spectrum of
density fluctuations. Even when simulations have been used, so-called Halofit
(Smith et al 2003) predictions on fairly large scales have been needed. We wish
to go beyond this limitation. We perform N-body and hydrodynamical simulations
within a sufficiently large cosmological volume to allow a direct connection
between simulations and linear spectra. While covering large length-scales, the
simulation resolution is good enough to allow us to explore the high-l
harmonics of the cosmic shear (up to l ~ 50000), well into the domain where
baryon physics becomes important. We then compare shear spectra in the absence
and in presence of various kinds of baryon physics, such as radiative cooling,
star formation, and supernova feedback in the form of galactic winds. We
distinguish several typical properties of matter fluctuation spectra in the
different simulations and test their impact on shear spectra. We compare our
outputs with those obtainable using approximate expressions for non--linear
spectra, and identify substantial discrepancies even between our results and
those of purely N-body results. Our simulations and the treatment of their
outputs however enable us, for the first time, to obtain shear results taht are
fully independent of any approximate expression, also in the high-l range,
where we need to incorporate a non-linear power spectrum of density
perturbations, and the effects of baryon physics. This will allow us to fully
exploit the cosmological information contained in future high--sensitivity
cosmic shear surveys, exploring the physics of cosmic shears via weak lensing
measurements.Comment: 13 pages, 19 figures, A&A in pres
High precision spectra at large redshift for dynamical DE cosmologies
The next generation mass probes will investigate DE nature by measuring
non-linear power spectra at various z, and comparing them with high precision
simulations. Producing a complete set of them, taking into account baryon
physics and for any DE state equation w(z), would really be numerically
expensive. Regularities reducing such duty are essential. This paper presents
further n-body tests of a relation we found, linking models with DE state
parameter w(z) to const.-w models, and also tests the relation in hydro
simulations.Comment: PASCOS 2010, the 16th International Symposium on Particles, Strings
and Cosmology, Valencia (Spain), July 19th - 23rd, 201
CMB and matter power spectra with non-linear dark-sector interactions
An interaction between dark matter and dark energy, proportional to the
product of their energy densities, results in a scaling behavior of the ratio
of these densities with respect to the scale factor of the Robertson-Walker
metric. This gives rise to a class of cosmological models which deviate from
the standard model in an analytically tractable way. In particular, it becomes
possible to quantify the role of potential dark-energy perturbations. We
investigate the impact of this interaction on the structure formation process.
Using the (modified) CAMB code we obtain the CMB spectrum as well as the linear
matter power spectrum. It is shown that the strong degeneracy in the parameter
space present in the background analysis is considerably reduced by considering
\textit{Planck} data. Our analysis is compatible with the CDM model at
the confidence level with a slightly preferred direction of the
energy flow from dark matter to dark energy.Comment: 22 pages, 8 figures, analysis enlarged, comments and references
added, accepted for publication in JCA
On general features of warm dark matter with reduced relativistic gas
Reduced Relativistic Gas (RRG) is a useful approach to describe the warm dark
matter (WDM) or the warmness of baryonic matter in the approximation when the
interaction between the particles is irrelevant. The use of Maxwell
distribution leads to the complicated equation of state of the J\"{u}ttner
model of relativistic ideal gas. The RRG enables one to reproduce the same
physical situation but in a much simpler form. For this reason RRG can be a
useful tool for the theories with some sort of a "new Physics". On the other
hand, even without the qualitatively new physical implementations, the RRG can
be useful to describe the general features of WDM in a model-independent way.
In this sense one can see, in particular, to which extent the cosmological
manifestations of WDM may be dependent on its Particle Physics background. In
the present work RRG is used as a complementary approach to derive the main
observational exponents for the WDM in a model-independent way. The only
assumption concerns a non-negligible velocity for dark matter particles
which is parameterized by the warmness parameter . The relatively high
values of ( ) erase the radiation (photons and
neutrinos) dominated epoch and cause an early warm matter domination after
inflation. Furthermore, RRG approach enables one to quantify the lack of power
in linear matter spectrum at small scales and in particular, reproduces the
relative transfer function commonly used in context of WDM with accuracy of
. A warmness with (equivalent to ) does not alter significantly the CMB power spectrum and is in
agreement with the background observational tests.Comment: 15 pages, 8 figures. Essential improvements in style and presentatio
Impact of gene polymorphisms of gonadotropins and their receptors on human reproductive success
Gonadotropins and their receptors' genes carry several single-nucleotide polymorphisms resulting in endocrine genotypes modulating reproductive parameters, diseases, and lifespan leading to important implications for reproductive success and potential relevance during human evolution. Here we illustrate common genotypes of the gonadotropins and gonadotropin receptors' genes and their clinical implications in phenotypes relevant for reproduction such as ovarian cycle length, age of menopause, testosterone levels, polycystic ovary syndrome, and cancer. We then discuss their possible role in human reproduction and adaptation to the environment. Gonadotropins and their receptors' variants are differently distributed among human populations. Some hints suggest that they may be the result of natural selection that occurred in ancient times, increasing the individual chance of successful mating, pregnancy, and effective post-natal parental cares. The gender-related differences in the regulation of the reproductive endocrine systems imply that many of these genotypes may lead to sex-dependent effects, increasing the chance of mating and reproductive success in one sex at the expenses of the other sex. Also, we suggest that sexual conflicts within the FSH and LH-choriogonadotropin receptor genes contributed to maintain genotypes linked to subfertility among humans. Because the distribution of polymorphic markers results in a defined geographical pattern due to human migrations rather than natural selection, these polymorphisms may have had only a weak impact on reproductive success. On the contrary, such genotypes could acquire relevant consequences in the modern, developed societies in which parenthood attempts often occur at a later age, during a short, suboptimal reproductive window, making clinical fertility treatments necessary
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