The Cluster Lensing And Supernova survey with Hubble (CLASH) is a 524-orbit multi-cycle treasury program to use the gravitational lensing properties of 25 galaxy clusters to accurately constrain their mass distributions. The survey, described in detail in this paper, will definitively establish the degree of concentration of dark matter in the cluster cores, a key prediction of structure formation models. The CLASH cluster sample is larger and less biased than current samples of space-based imaging studies of clusters to similar depth, as we have minimized lensing-based selection that favors systems with overly dense cores. Specifically, twenty CLASH clusters are solely X-ray selected. The X-ray selected clusters are massive (kT > 5 keV) and, in most cases, dynamically relaxed. Five additional clusters are included for their lensing strength (θ Ein > 35 at z s = 2) to optimize the likelihood of finding highly magnified high-z (z > 7) galaxies. A total of 16 broadband filters, spanning the near-UV to near-IR, are employed for each 20-orbit campaign on each cluster. These data are used to measure precise (σ z ∼ 0.02(1+z)) photometric redshifts for newly discovered arcs. Observations of each cluster are spread over 8 epochs to enable a search for Type Ia supernovae at z > 1 to improve constraints on the time dependence of the dark energy equation of state and the evolution of supernovae. We present newly re-derived X-ray luminosities, temperatures, and Fe abundances for the CLASH clusters as well as a representative source list for MACS1149.6+2223 (z = 0.544).

Dark energy and dark matter are the dominant sources in the evolution of the late universe. They are currently only indirectly detected via their gravitational effects, and there could be a coupling between them without violating observational constraints. We investigate the background dynamics when dark energy is modelled as exponential quintessence, and is coupled to dark matter via simple models of energy exchange. We introduce a new form of dark sector coupling, which leads to a more complicated dynamical phase space and has a better physical motivation than previous mathematically similar couplings.Comment: 11 pages, 4 figures, revtex, references adde

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In this paper we analyze the effect of recently proposed classes of sudden future singularities on causal geodesics of FLRW spacetimes. Geodesics are shown to be extendible and just the equations for geodesic deviation are singular, although tidal forces are not strong enough to produce a Big Rip. For the sake of completeness, we compare with the typical sudden future singularities of phantom cosmologies.PACS numbers: 04.20. Dw, 98.80.Jk Recently it has been suggested [1] that in an expanding FLRW universe a curvature singularity may appear at a finite time before Big Crunch for matter contents that satisfy both weak and strong energy conditions. This family of models has been further enlarged [2], and the same sort of behavior has also been found in inhomogeneous models [3]. It has been remarked, however, that the dominant energy condition must be violated in order to produce such sudden singularities [4], and that the inclusion of quantum corrections may appease their strength [5].In these models, the energy density of the formal perfect fluid is finite at the singularity, but the pressure is infinite. More specifically, in the models proposed in [1, 2] the scale factor and its first derivative are also finite, whereas second and higher order derivatives become infinite (in the models presented in [5] the singularity does not appear in the scale factor and its first three derivatives are finite).These sorts of sudden future singularities are quite different from those in phantom cosmologies [6], because for the latter not only does the second derivative of the scale factor blow up at the singularity, but also do the energy density, the scale factor and its derivatives from the first order up.In this paper we want to analyze the behavior of the sudden future singularities in [1, 2, 3, 4, 5] from a different point of view. Instead of regarding the curvature scalar polynomials we shall take a look at causal geodesics, since they describe the trajectories and the fate of nonaccelerated observers on these universes. This * lfernandez@etsin.upm.es; http://debin.etsin.upm.es/ilfj.htm † wtplasar@lg.ehu.es is not a difficult task since FLRW cosmologies,are homogeneous and isotropic and therefore have a sixdimensional group of isometries generated, for instance, by the Killing fieldswhich yield six different constants of geodesic motion, i.e. three linear momenta and three angular momenta:f (r) sin θ cos φṙ} , P 2 = a(t) r f (r) cos θ sin φθ + sin θ cos φφ +(3b) f (r) sin θ sin φṙ} ,P 3 = a(t) f (r) cos θṙ − r f (r) sin θθ ,L 1 = a(t)r 2 cos φθ − sin θ cos θ sin φφ ,L 2 = a(t)r 2 sin φθ + sin θ cos θ cos φφ ,L 3 = a(t)r 2 sin 2 θφ,

General Relativity and the ΛCDM framework are currently the standard lore and constitute the concordance paradigm. Nevertheless, long-standing open theoretical issues, as well as possible new observational ones arising from the explosive development of cosmology the last two decades, offer the motivation and lead a large amount of research to be devoted in constructing various extensions and modifications.All extended theories and scenarios are first examined under the light of theoretical consistency, and then are applied to various geometrical backgrounds, such as the cosmological and the spherical symmetric ones. Their predictions at both the background and perturbation levels, and concerning cosmology at early, intermediate and late times, are then confronted with the huge amount of observational data that astrophysics and cosmology are able to offer recently. Theories, scenarios and models that successfully and efficiently pass the above steps are classified as viable and are candidates for the description of Nature.We list the recent developments in the fields of gravity and cosmology, presenting the state of the art, high-lighting the open problems, and outlining the directions of future research.