Scalar fields have played an important role in the development of fundamental theories physics as well other branches such gravitation and cosmology. For a long time these escaped detection until 2012 year when Higgs boson was observed for first time. Since then alternatives to general theory relativity like Brans-Dicke theory, scalar-tensor gravity their higher derivative generalizations -- collectively known Horndeski acquired renewed interest. In present review we discuss on several...

Here we investigate the cosmic dynamics of Friedmann-Robertson-Walker universes---flat spatial sections---which are driven by nonlinear electrodynamics (NLED) Lagrangians. We pay special attention to check sign square sound speed since, whenever latter quantity is negative, corresponding cosmological model classically unstable against small perturbations background energy density. Besides, based on causality arguments, one has require that mentioned should propagate at most local light. also...

We explore quintessence models of dark energy which exhibit non-minimal coupling between the matter and components cosmic fluid. The kind chosen is inspired by scalar–tensor theories gravity. impose a suitable dynamics expansion allowing us to derive exact Friedmann–Robertson–Walker solutions once function given as input. Self-interaction potentials single double exponential types emerge result our choice function. stability existence are discussed in some detail. Although, general, with...

A class of braneworld models can lead to phantom-like acceleration the late universe, but without need for any phantom matter. In simplest models, universe contains only cold dark matter and a cosmological constant. We generalize these by introducing quintessence field. The new feature in our is that leads crossing divide, w = −1. This purely gravitational effect, there no instability. Furthermore, Hubble parameter always decreasing, big rip singularity future.

The main aim of this paper is to present the multiscalar field components as candidates for dark energy Universe and their observational constraints. We start with canonical quintessence phantom fields quadratic potentials show that a more complex model should satisfy current cosmological observations. Then, we some implications combination two fields, called quintom models. consider types models: one sum potentials, including an interacting term between fields. find adding extra degree...

Models of the universe with arbitrary (non gravitational) interaction between components cosmic fluid: phantom energy and background, are investigated.A general form that is inspired in scalar-tensor theories gravity considered.No specific model for fluid assumed.We concentrate our investigation on solutions free coincidence problem.We found a wide region parameter space where big rip singularity also.Physical arguments, together arguments based analysis observational evidence, suggest...

The dynamics of a cosmological model fueled by scalar field dark matter with cosh-like potential plus constant is investigated in detail. It revealed that the late-time attractor always de Sitter solution, and that, depending on values free parameters, oscillating solution -- modeling cold mediates between some early stage (say, radiation-dominated solution) accelerating attractor.

In this paper, we perform a dynamical systems study of the purely kinetic k-essence. Although these models have been studied in past, full dynamics phase space incorporating stability conditions for theoretical consistency is lacking. Our results confirm very rigorous and clear way that i) can not explain unified dark matter energy components cosmic fluid ii) are adequate to existing observational evidence, particular observed amount structure.

The theory of dynamical systems is a very complex subject that has produced several surprises in the recent past connection with chaos and fractals. application tools cosmological settings less known, spite number published scientific papers on this subject. In paper, mostly pedagogical introduction to basic presented. It shown that, their amazing simplicity, these allow us extract essential information asymptotic dynamics wide variety models. power illustrated within context so-called...

In this paper we discuss on the phenomenological viability of nonmetricity theories gravity which are based in class generalized Weyl spacetimes -- denoted by $W_4$ where arbitrary is allowed. This geometry includes so called teleparallel spaces $Z_4$, geometric basement symmetric (STTs). The guiding principle our discussion gauge symmetry (WGS), a manifest spaces. Here derive master equation that drives invariant variations length vectors during parallel transport $W_4$. mathematical basis...

The main aim of this paper is to analyse minimally-coupled scalar-fields -- quintessence and phantom as the candidates explain accelerated expansion universe compare its observables current cosmological observations; a byproduct we present python module. This work includes parameter $\epsilon$ which allows incorporate both fields within same analysis. Examples potentials, so far included, are $V(\phi)=V_0\phi^{\mu}e^{\beta \phi^\alpha}$ $V(\phi)=V_0(\cosh(\alpha \phi)+\beta)$ with $\alpha$,...

In this work we present a model of the universe in which dark energy is modeled explicitly with both dynamical quintessence field and cosmological constant. Our results confirm possibility future collapsing (for given region parameter space), necessary for consistent formulation string quantum theories. The predictions distance modulus supernovae are similar to those standard $\ensuremath{\Lambda}\mathrm{CDM}$ model.

We apply the dynamical systems tools to study linear dynamics of a self-interacting scalar field trapped in braneworld, for wide variety self-interaction potentials. focus on Randall-Sundrum and Dvali-Gabadadze-Porrati braneworld models exclusively. These are complementary each other: while brane produces UV) corrections general relativity, modifies Einstein's theory at large scales, i e., IR modifications relativity. This asymptotic properties both models, shows---in phase space---the way...

A method for deriving Friedmann-Robertson-Walker (FRW) solutions developed in Int.J. Mod.Phys.D5(1996)71-84, is generalized to account models with non-minimal coupling between the dark energy and matter.New quintessence phantom (flat) FRW are found.Their physical significance discussed.Additionally, aforementioned modified so that, "coincidence free" can be readily derived.Besides, we review some aspects of barrier crossing.In this regard present a model which free from coincidence problem...

In this work we study a scenario with warped 5D smooth braneworld 4D Minkowski geometry builded from bulk scalar matter non-minimally coupled to gravity an additional Gauss-Bonnet term. We present exact solutions for the full configuration in contrast previous results where only approximate were constructed due highly non-linear character of relevant differential equations. These allow us necessary conditions finiteness Planck mass and additionally, enables perform more rigorous analysis...

In this paper we investigate to which extent noncommutativity, a intrinsically quantum property, may influence the Friedmann-Robertson-Walker cosmological dynamics at late times/large scales. To our purpose it will be enough explore asymptotic properties of model in phase space. Our recipe build noncommutativity into is based approach reference [Phys. Rev. Lett. {\bf 88} (2002) 161301], and can summarized following steps: i) Hamiltonian derived from Einstein-Hilbert action (plus...

We investigate the cosmological dynamics of an up to cubic curvature correction general relativity (GR) known as Einsteinian gravity, whose vacuum spectrum consists graviton exclusively. Its cosmology is well posed initial value problem. are able uncover global asymptotic structure phase space this theory. It revealed that inflationary, matter-dominated big bang past attractor, which means inflation starting point any physically meaningful cosmic history. Given higher-order corrections GR...

We investigate in detail the asymptotic properties of tachyon cosmology for a broad class self-interaction potentials. The present approach relies on an appropriate re-definition field, which, conjunction with method formerly applied bibliography different context allows us to generalize dynamical systems study wider potentials beyond (inverse) square-law one. It is revealed that independent functional form potential, matter-dominated solution and ultra-relativistic (also matter-dominated)...