k-essence and the coincidence problem

  title={k-essence and the coincidence problem},
  author={Michael Malquarti and Edmund J. Copeland and Andrew R. Liddle},
  journal={Physical Review D},
$k$-essence has been proposed as a possible means of explaining the coincidence problem of the Universe beginning to accelerate only at the present epoch. We carry out a comprehensive dynamical systems analysis of the k-essence models given so far in the literature. We numerically study the basin of attraction of the tracker solutions and we highlight the behavior of the field close to sound speed divergences. We find that, when written in terms of parameters with a simple dynamical… 

Figures and Tables from this paper

The phase space of k-Essence f(R) gravity theory
Among the remaining viable theories that can successfully describe the late-time era is the $k$-Essence theory and in this work we study in detail the phase space of $k$-Essence $f(R)$ gravity in
Quintessence as k-essence
Quintessence and k-essence have been proposed as candidates for the dark energy component of the universe that would be responsible of the currently observed accelerated expansion. In this Letter we
We investigate a k-essence field localized on the brane evolving linearly with the cosmological time for some kinetic functions and consider the atypical k-essence model for linear and nonlinear
K-chameleon and the coincidence problem
In this paper we present a hybrid model of k-essence and chameleon, named as k-chameleon. In this model, due to the chameleon mechanism, the directly strong coupling between the k-chameleon field and
On the dynamics of k-essence models
We investigate cosmological dynamics of models with higher-order corrections to the canonical (second-order) kinetic lagrangian for a scalar field, which have been termed k-essence. We study the
k-essence and extended tachyons in brane-worlds
We study a k-essence field evolving linearly with the cosmic time and the atypical k-essence model on a homogeneous and isotropic flat 3-brane. We show that the k-field is driven by an inverse
A stringy perspective on the coincidence problem
Abstract We argue that, for string compactifications broadly consistent with swampland constraints, dark energy is likely to signal the beginning of the end of our universe as we know it, perhaps
We study spatially flat isotropic universes driven by k-essence. It is shown that Friedmann and k-field equations may be analytically integrated for arbitrary k-field potentials during evolution with
f(R) gravity k-Essence late-time phenomenology
In this work we shall study the late-time behavior of $k$-Essence $f(R)$ gravity without scalar potential, in the presence of matter and radiation perfect fluids. We quantify the late-time study by
Dark energy, curvature, and cosmic coincidence
The fact that the energy densities of dark energy and matter are similar currently, known as the coincidence problem, is one of the main unsolved problems of cosmology. We present here a model in


Essentials of k essence
We recently introduced the concept of ``k-essence'' as a dynamical solution for explaining naturally why the universe has entered an epoch of accelerated expansion at a late stage of its evolution.
A New view of k-essence
K-essence models, relying on scalar fields with non-canonical kinetic terms, have been proposed as an alternative to quintessence in explaining the observed acceleration of the Universe. We consider
Dynamical solution to the problem of a small cosmological constant and late-time cosmic acceleration
In the theories considered, the dynamics causes the scalar field to lock automatically into a negative pressure state at the onset of matter domination such that the present epoch is the earliest possible time consistent with nucleosynthesis restrictions when it can start to dominate.
Quintessence, cosmic coincidence, and the cosmological constant
Recent observations suggest that a large fraction of the energy density of the Universe has negative pressure. One explanation is vacuum energy density; another is quintessence in the form of a
Perturbations in k-inflation
Abstract We extend the theory of cosmological perturbations to the case when the “matter” Lagrangian is an arbitrary function of the scalar field and its first derivatives. In particular, this
Cosmological consequences of a rolling homogeneous scalar field.
  • Ratra, Peebles
  • Physics, Medicine
    Physical review. D, Particles and fields
  • 1988
It is argued that a number of models in which the energy density of the scalar field red-shifts in a specific manner are studied could reconcile the low dynamical estimates of the mean mass density with the negligibly small spatial curvature preferred by inflation.
Cosmological imprint of an energy component with general equation of state
We examine the possibility that a significant component of the energy density of the Universe has an equation of state different from that of matter, radiation, or cosmological constant ({Lambda} ).
Kinetically driven quintessence
Abstract Recently, a novel class of models for inflation has been found in which theinflationary dynamics is driven solely by (non-canonical) kinetic terms ratherthan by potential terms. As an obvious
Abstract We discuss the cosmological constant problem in the light of dilatation symmetry and its possible anomaly. For dilatation symmetric quantum theories realistic asymptotic cosmology is
The Case for a positive cosmological Lambda term
Recent observations of Type 1a supernovae indicating an accelerating universe have once more drawn attention to the possible existence, at the present epoch, of a small positive Lambda-term