3,144 research outputs found
Designing Horndeski and the effective fluid approach
We present a family of designer Horndeski models, i.e. models that have a
background exactly equal to that of the CDM model but perturbations
given by the Horndeski theory. Then, we extend the effective fluid approach to
Horndeski theories, providing simple analytic formulae for the equivalent dark
energy effective fluid pressure, density and velocity. We implement the dark
energy effective fluid formulae in our code EFCLASS, a modified version of the
widely used Boltzmann solver CLASS, and compare the solution of the
perturbation equations with those of the code hi_CLASS which already includes
Horndeski models. We find that our simple modifications to the vanilla code are
accurate to the level of with respect to the more complicated
hi_CLASS code. Furthermore, we study the kinetic braiding model both on and off
the attractor and we find that even though the full case has a proper
CDM model limit for large , it is not appropriately smooth, thus
causing the quasistatic approximation to break down. Finally, we focus on our
designer model (HDES), which has both a smooth CDM limit and
well-behaved perturbations, and we use it to perform Markov Chain Monte Carlo
analyses to constrain its parameters with the latest cosmological data. We find
that our HDES model can also alleviate the soft tension between the
growth data and Planck 18 due to a degeneracy between and one of its
model parameters that indicates the deviation from the CDM model.Comment: 31 pages, 9 figures, 5 tables, comments welcome. The codes used in
the analysis of this paper can be found at
https://members.ift.uam-csic.es/savvas.nesseris/efclass.html and at
https://github.com/wilmarcardonac/EFCLAS
The traces of anisotropic dark energy in light of Planck
We study a dark energy model with non-zero anisotropic stress, either linked
to the dark energy density or to the dark matter density. We compute
approximate solutions that allow to characterise the behaviour of the dark
energy model and to assess the stability of the perturbations. We also
determine the current limits on such an anisotropic stress from the cosmic
microwave background data by the Planck satellite, and derive the corresponding
constraints on the modified growth parameters like the growth index, the
effective Newton's constant and the gravitational slip.Comment: 29 pages, 10 figures; matches version accepted for publication in
JCA
Making Political Tourism As an Alternative Model for Hawaii Indigenous Development
The current tourism business model, which is visitor-centered, shows how tourism has strong negative impacts to the host and the place. It happens in many places in the world where tourism business is run by outsiders or with outside capital, and creating conflict with local population. Political tourism is an alternative to the current business model because it looks at the business from the other side: the host-place-centered. Political tourism can be seen as the first step in "indigenizing" capitalism based on local values. The proposed model addresses subsystems in tourism business components, i.e. the transaction, transfer, and treatment systems. It suggests several strategies to make political tourism happen with reference to Native Hawaiians tourism development. It offers some lessons that can be applicable to other places in Asia and the Pacific
New Types of Protein Tyrosine Phosphatase 1B Inhibitors from Marine and Terrestrial Organisms
東北医科薬科大学平成28年
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