We study a holographic cosmological model in which the infrared cutoff is set by the Ricci's length and dark matter and dark energy do not evolve on their own but interact non-gravitationally with each other. This greatly alleviates the cosmic coincidence problem because the ratio between both components does not vanish at any time. We constrain the model with observational data from supernovae, cosmic background radiation, baryon acoustic oscillations, gas mass fraction in galaxy clusters, the history of the Hubble function, and the growth function.

We propose, and constrain with the latest observational data, three model-independent parametrizations of the cosmic deceleration parameter q(z). They are well behaved and stay finite at all redshifts. We construct them by fixing the value of q at high redshift, q(z ≫ 1) = 1/2 (as demanded by cosmic structure formation), and at the far future, q(z = −1) = −1, and smoothly interpolating q(z) between them. The fixed point at z = −1 is not arbitrarily chosen; it readily follows from the second law of thermodynamics. This fairly reduces the ample latitude in parameterizing q(z). a

We constrain an interacting, holographic dark energy model, first proposed by two of us in [1], with observational data from supernovae, CMB shift, baryon acoustic oscillations, x-rays, and the Hubble rate.The growth function for this model is also studied. The model fits the data reasonably well but still the conventional ΛCDM model fares better. Nevertheless, the holographic model greatly alleviates the coincidence problem and shows compatibility at 1σ confidence level with the age of the old quasar APM

This article examines the influence of economic crisis on voting preferences for the emerging Spanish parties (Podemos and Ciudadanos). We develop a multinomial model that tests their voting antecedents, and we find three results that may be relevant for the literature on the emergence of parties. First, a negative evaluation of the country’s economic situation has a major impact on votes for the two parties. Second, the perception of corruption also plays a crucial role in understanding support for the two emerging parties. And third, both the evaluation of the country’s economic situation and the perception of corruption interact to account for the emergence of both Podemos and Ciudadanos. We conclude that the emergence of new parties has an economic basis, but political factors – such as corruption – are not suppressed by this. Conversely, the two factors interact in order to finally give rise to the new parties.

We consider holographic cosmological models of dark energy in which the infrared cutoff is set by the Hubble's radius. We show that any interacting dark energy model with a matter like term able to alleviate the coincidence problem (i.e., with a positive interaction term, regardless of its detailed form) can be recast as a noninteracting model in which the holographic parameter c 2 evolves slowly with time. Two specific cases are analyzed. First, the interacting model presented in [1] is considered, and its corresponding noninteracting version found. Then, a new noninteracting model, with a specific c 2 (z) expression, is proposed and analyzed along with its corresponding interacting version. We constrain the parameters of both models using observational data, and show that they can be told apart at the perturbative level.