Related papers: Some studies on k essence Lagrangian
Early universe equations of state including realistic interactions between constituents are built up. Under certain reasonable assumptions, these equations are able to generate an inflationary regime prior to the nucleosynthesis period. The…
The Gleyzes-Langlois-Piazza-Vernizzi (GLPV) theories up to quartic order are the general scheme of scalar-tensor theories allowing the possibility for realizing the tensor propagation speed $c_t$ equivalent to 1 on the isotropic…
The `Little Bangs' made in particle collider experiments reproduce the conditions in the Big Bang when the age of the Universe was a fraction of a second. It is thought that matter was generated, the structures in the Universe were formed…
The present paradigm in cosmology is the usual Big-Bang Cosmology in which two stages of accelerated expansion are incorporated: the inflationary phase in the very early universe which produces the classical inhomogeneities observed in the…
The paper investigates the collapse of the generalized emergent Vaidya spacetime in the setting of $f(\bar{R}, \bar{T})$ gravity, specifically in K-essence theory. In this study, the Dirac-Born-Infeld type non-standard Lagrangian is used to…
The current understanding of structure formation in the early universe is mainly built on a magnification of quantum fluctuations in an initial vacuum state during an early phase of accelerated universe expansion. One usually describes this…
By incorporating the holographic principle in a time-depending Lambda-term cosmology, new physical bounds on the arbitrary parameters of the model can be obtained. Considering then the dark energy as a purely geometric entity, for which no…
A general framework for an emergent universe scenario has been given which makes use of an equation of state. The general features of the model have also been studied and possible primordial composition of the universe have been suggested.
The cosmic evolution of a dark matter model which behaves relativistically in the early Universe is explored. Dark matter is described as a complex scalar field, whose earliest evolution is characterized by a stiff equation of state ($p…
Observational evidence indicating that the expansion of the universe is accelerating has surprised cosmologists in recent years. Cosmological models have sought to explain this acceleration by incorporating `dark energy', of which the…
We investigate how the Raychaudhuri equation behaves in the $k$-essence geometry. As far as we are concerned, both the early and current epochs of the universe are relevant to the $k$-essence theory. Here, we have studied the $k$-essence…
In this paper it is suggested that inclusion of mutual gravitational interactions among the particles in the early dense universe can lead to a 'pre-big bang' scenario, with particle masses greater than the Planck mass implying an…
Recent analysis of the observation data indicates that the equation of state of the dark energy might be smaller than -1, which leads to the introduction of phantom models featured by its negative kinetic energy to account for the regime of…
The expansion of the universe has been accepted by scientists for more than a century. However, since the 1990s, observations have suggested that the universe is expanding at an accelerating rate. Although the source of this acceleration is…
Inverse decays are an interesting avenue for producing dark matter in the early universe. We study in detail various phases of dark matter parameter space where inverse decays control its abundance, expanding on our work of INDY dark matter…
We show that phantom dark energy, if it is described by a K-essence theory, has three fundamental problems: first, its hamiltonian is unbounded from below. Second, classical stability precludes the equation of state from crossing the…
In this paper we review a part of the approaches that have been considered to explain the extraordinary discovery of the late time acceleration of the Universe. We discuss the arguments that have led physicists and astronomers to accept…
In this study, we investigate the late-time accelerated expansion of the universe within the framework of non-minimally coupled $f(Q,L_m)$ gravity, where $Q$ is the non-metricity scalar and $L_m$ is the matter Lagrangian. We derive modified…
This paper is devoted to study the accelerated expansion of the universe by exploring the Brans-Dicke parameter in different eras. For this purpose, we take FRW universe model with viscous fluid (without potential) and Bianchi type I…
We generalize some of those results reported by Gonz\'{a}lez-D\'{i}az by further tuning the parameter ($\beta$) which is closely related to the canonical kinetic term in $k$-essence formalism. The scale factor $a(t)$ could be negative and…