相关论文: Imperfect Dark Energy from Kinetic Gravity Braidin…

The present paper deals with cylindrically symmetric metric in the form of Marder (1958) with Saez-Ballester theory of gravitation in the presence of perfect fluid and dark energy. In order to obtain the deterministic solution of the field…

The paper proposes a novel cosmological model based on a two-field scenario, where the two fields are independently coupled with a specific invariant, based on cubic contractions of the Riemann tensor. After obtaining the modified Friedmann…

Motivated by the apparent discrepancy between Cosmic Microwave Background measurements of the Hubble constant and measurements from Type-Ia supernovae, we construct a model for Dark Energy with equation of state $w = p / \rho < -1$,…

We reflect on the possibility of having a matter action that is invariant only under transverse diffeomorphisms. This possibility is particularly interesting for the dark sector, where no restrictions arise based on the weak equivalence…

A dual component made of non-relativistic particles and a scalar field, exchanging energy, naturally falls onto an attractor solution, making them a (sub)dominant part of the cosmic energy during the radiation dominated era, provided that…

We study scalar-tensor theory, k-essence and modified gravity with Lagrange multiplier constraint which role is to reduce the number of degrees of freedom. Dark Energy cosmology of different types ($\Lambda$CDM, unified inflation with DE,…

We construct a class of 4D `yoga' (naturally relaxed) models for which the gravitational response of heavy-particle vacuum energies is strongly suppressed. The models contain three ingredients: (i) a relaxation mechanism, (ii) a very…

Realizing dark energy and the observed de Sitter spacetime in quantum gravity has proven to be obstructed in most every usual approach. We argue that additional degrees of freedom of the left- and right-movers in string theory and a…

Boson stars in zero-, one-, and two-node equilibrium states are modeled numerically within the framework of Scalar-Tensor Gravity. The complex scalar field is taken to be both massive and self-interacting. Configurations are formed in the…

Physical effects in brane worlds models emerge by the incorporation of field modes coming from extra dimensions with the usual four dimensional ones. Such effects can be tested with well established experiments to set bounds on the…

In this paper, we study a triad of inhomogeneous scalar fields, known as "solid", as a source of homogeneous but anisotropic dark energy. By using a dynamical system approach, we find that anisotropic accelerated solutions can be realized…

We address the fine-tuning problem of dark energy cosmologies which arises when the dark energy density needs to initially lie in a narrow range in order for its present value to be consistent with observations. As recently noticed, this…

The scalar-vector-tensor theories with second-order equations of motion can accommodate both Horndeski and generalized Proca theories as specific cases. In the presence of a perfect fluid, we study the cosmology in such a most general…

The expansion history of the Universe reconstructed from a combination of recent data indicates a preference for a changing Dark Energy (DE) density. Moreover, the DE density appears to be increasing with cosmic time, with its equation of…

The chapter expounds a theory based on the interpretation of the dark energy as a strain energy of a physical continuum. The theory is based on the analogy that exists between the properties of space-time and the properties of elastic…

We introduce and carefully define an entire class of field theories based on non-standard spinors. Their dominant interaction is via the gravitational field which makes them naturally dark; we refer to them as Dark Spinors. We provide a…

We study the autonomous system for a scalar-tensor model of dark energy with Gauss-Bonnet and non-minimal couplings. The critical points describe important stable asymptotic scenarios including quintessence, phantom and de Sitter attractor…

The latest DESI DR2 results, when combined with other independent cosmological data on the Cosmic Microwave Background and supernovas, suggest a preference for dynamical dark energy. We propose a novel cosmological scenario, which features…

In the general context of scalar-tensor theories, we consider a model in which a scalar field coupled to the Ricci scalar in the gravitational sector of the Lagrangian, is also playing the role of an ``Extended Quintessence'' field,…

We study the late-time cosmological dynamics of a two-field dark energy model consisting of a canonical quintessence scalar field and a phantom scalar field in a spatially flat FLRW universe. The fields are minimally coupled to gravity and…