Miguel Quartin

Challenges for scaling cosmologies

A cosmological model that aims at solving the coincidence problem should show that dark energy and dark matter follow the same scaling solution from some time onward. At the same time, the model should contain a sufficiently long matter-dominated epoch that takes place before acceleration in order to guarantee a decelerated epoch and structure formation. So a successful cosmological model requires the occurrence of a sequence of epochs, namely a radiation era, a matter-dominated era and a final accelerated scaling attractor with

Dark interactions and cosmological fine-tuning

\Omega_{\phi} \simeq 0.7

Beyond ΛCDM: Problems, solutions, and the road ahead

. In this paper we derive the generic form of a scalar-field Lagrangian that possesses scaling solutions in the case where the coupling

Viable singularity-free f(R) gravity without a cosmological constant.

Q

Real-time Cosmology

between dark energy and dark matter is a free function of the field

Large-scale inhomogeneities may improve the cosmic concordance of supernovae.

\phi

Measuring our peculiar velocity on the CMB with high-multipole off-diagonal correlations

. We then show, rather surprisingly, that the aforementioned sequence of epochs cannot occur for a vast class of generalized coupled scalar field Lagrangians that includes, to our knowledge, all scaling models in the current literature.

Accurate weak lensing of standard candles. I. Flexible cosmological fits

Cosmological models involving an interaction between dark matter and dark energy have been proposed in order to solve the so-called coincidence problem. Different forms of coupling have been studied, but there have been claims that observational data seem to narrow (some of) them down to something annoyingly close to the

Accurate Weak Lensing of Standard Candles. II. Measuring sigma8 with Supernovae

\Lambda

Breaking the spell of Gaussianity: forecasting with higher order Fisher matrices

CDM model, thus greatly reducing their ability to deal with the problem in the first place. The smallness problem of the initial energy density of dark energy has also been a target of cosmological models in recent years. Making use of a moderately general coupling scheme, this paper aims to unite these different approaches and shed some light as to whether this class of models has any true perspective in suppressing the aforementioned issues that plague our current understanding of the universe, in a quantitative and unambiguous way.