Related papers: Interacting dark sector: Lagrangian formulation ba…
The standard model of cosmology relies on the existence of two components, "dark matter" and "dark energy", which dominate the expansion of the Universe. There is no direct proof of their existence, and their nature is still unknown. Many…
We discuss models for the cosmological dark sector in which the energy density of a scalar field approximates Einstein's cosmological constant and the scalar field value determines the dark matter particle mass by a Yukawa coupling. A model…
We discuss two lagrangian interacting dark energy models in the context of the holographic principle. The potentials of the interacting fields are constructed. The models are compared with CMB distance information, baryonic acoustic…
In this work we investigate the evolution of a Universe consisted of a scalar field, a dark matter field and non-interacting baryonic matter and radiation. The scalar field, which plays the role of dark energy, is non-minimally coupled to…
We propose that dark energy in the form of a scalar field could effectively couple to dark matter inhomogeneities. Through this coupling energy could be transferred to/from the scalar field, which could possibly enter an accelerated regime.…
Cosmological background observations cannot fix the dark energy equation of state, which is related to a degeneracy in the definition of the dark sector components. Here we show that this degeneracy can be broken at perturbation level by…
Interacting dark energy-dark matter models have been widely analyzed in the literature in an attempt to find traces of new physics beyond the usual cosmological ($\Lambda$CDM) models. Such a coupling between both dark components is usually…
We consider an extended scalar-tensor theory of gravity where the action has two interacting scalar fields, a Brans-Dicke field which makes the effective Newtonian constant a function of coordinates and a Higgs field which has derivative…
We consider the cosmological dynamics of the cubic Galileon field model interacting with dark matter, where the interaction between the cosmic dark sectors is proportional to Hubble parameter and dark energy density. The background field…
We investigate the cosmological applications of new gravitational scalar-tensor theories, which are novel modifications of gravity possessing 2+2 propagating degrees of freedom, arising from a Lagrangian that includes the Ricci scalar and…
Considering the general Lagrangian of k-essence models, we study and classify them through variables connected to the fluid equation of state parameter w_\kappa. This allows to find solutions around which the scalar field describes a…
We present cosmological perturbation theory in neutrinos probe interacting dark-energy models, and calculate cosmic microwave background anisotropies and matter power spectrum. In these models, the evolution of the mass of neutrinos is…
The transient acceleration which the current cosmic acceleration is not eternal is possible by introducing the interaction between dark matter and dark energy. If the energy transfer is from dark energy to dark matter, then it is possible…
Dark matter, the major component of the matter content of the Universe, played a significant role at early stages during structure formation. But at present the Universe is dark energy dominated as well as accelerating. Here, the presence…
We present a new approach to build models of quintessence interacting with dark or baryonic matter. We use a variational approach for relativistic fluids to realize an effective description of matter fields at the Lagrangian level. The…
Cosmological models with two interacting fluids, each satisfying the strong energy condition, are studied in the framework of classical General Relativity. If the interactions are phenomenologically described by a power law in the scale…
In this study, motivated by recent results from DESI DR2 suggesting the existence of evolving/interacting dark energy, we analyze spatially flat FLRW interacting scalar-tensor cosmological models with non-minimal coupling (NMC) between the…
We introduce a family of phenomenological cosmological models featuring an interacting dark sector modulated by a sparseness scale parameter, in order to describe the late-time accelerated expansion of the universe. The sparseness scale,…
Currently there is no definitive description for the accelerated expansion of the Universe at both early and late times; we know these two periods as the epochs of inflation and dark energy. Contained within this Thesis are two studies of…
The evolution of scalar linear perturbations is studied in gauge-invariant approach for 2-component models with nonrelativistic matter and minimally coupled scalar fields, the potentials of which were constructed for either constant dark…