Abstract:
I briefly review our current understanding of dark matter and dark energy. The first part of this paper focusses on issues pertaining to dark matter including observational evidence for its existence, current constraints and the `abundance of substructure' and `cuspy core' issues which arise in CDM. I also briefly describe MOND. The second part of this review focusses on dark energy. In this part I discuss the significance of the cosmological constant problem which leads to a predicted value of the cosmological constant which is almost $10^{123}$ times larger than the observed value $\la/8\pi G \simeq 10^{-47}$GeV$^4$. Setting $\la$ to this small value ensures that the acceleration of the universe is a fairly recent phenomenon giving rise to the `cosmic coincidence' conundrum according to which we live during a special epoch when the density in matter and $\la$ are almost equal. Anthropic arguments are briefly discussed but more emphasis is placed upon dynamical dark energy models in which the equation of state is time dependent. These include Quintessence, Braneworld models, Chaplygin gas and Phantom energy. Model independent methods to determine the cosmic equation of state and the Statefinder diagnostic are also discussed. The Statefinder has the attractive property $\atridot/a H^3 = 1 $ for LCDM, which is helpful for differentiating between LCDM and rival dark energy models. The review ends with a brief discussion of the fate of the universe in dark energy models.

Abstract:
It is a puzzle why the densities of dark matter and dark energy are nearly equal today when they scale so differently during the expansion of the universe. This conundrum may be solved if there is a coupling between the two dark sectors. In this paper we assume that dark matter is made of cold relics with masses depending exponentially on the scalar field associated to dark energy. Since the dynamics of the system is dominated by an attractor solution, the dark matter particle mass is forced to change with time as to ensure that the ratio between the energy densities of dark matter and dark energy become a constant at late times and one readily realizes that the present-day dark matter abundance is not very sensitive to its value when dark matter particles decouple from the thermal bath. We show that the dependence of the present abundance of cold dark matter on the parameters of the model differs drastically from the familiar results where no connection between dark energy and dark matter is present. In particular, we analyze the case in which the cold dark matter particle is the lightest supersymmetric particle.

Abstract:
We study the quantum remnant of a scalar field protected by the uncertainty principle. The quantum remnant that survived the later stage of evolution of the universe may provide dark energy and dark matter depending on the potential. Though the quantum remnant shares some useful property of complex scalar field (spintessence) dark energy model, % However although it avoids the formation of Q-ball, quantum fluctuations are still unstable to the linear perturbations for $V \sim \phi^q$ with $q<1$ as in the spintessence model.

Abstract:
We study the quantum remnant of a scalar field protected by the uncertainty principle. The quantum remnant that survived the later stage of evolution of the universe may provide dark energy and dark matter depending on the potential. Though the quantum remnant shares some useful property of complex scalar field (spintessence) dark energy model, % However although it avoids the formation of Q-ball, quantum fluctuations are still unstable to the linear perturbations for $V \sim \phi^q$ with $q<1$ as in the spintessence model.

Abstract:
Velocity-dependent interactions in a fundamental-string dominated universe lead quite naturally, with reasonable assumptions on initial conditions, to an accelerating expanding universe without assuming the existence of a cosmological constant. This result also holds generically for a universe dominated by moving extremal black holes, owing to a repulsive velocity- dependent force. This interaction, however, does not preclude structure formation. Here we discuss a toy model including both ordinary and extremal matter, in which the latter accounts for dark matter while simultaneously acting as effective dark energy. Eternal acceleration is once more seen to arise in this case.

Abstract:
A model concerning particle theory and cosmology is proposed. Matter field, dark matter and dark energy are created by an energy flow from space to primordial matter fields at the phase transition in the early universe.

Abstract:
Dark energy in the universe is assumed to be vacuum energy. The energy-momentum of vacuum is described by a scale-dependent cosmological constant. The equations of motion imply for the density of matter (dust) the sum of the usual matter density (luminous matter) and an additional matter density (dark matter) similar to the dark energy. The scale-dependent cosmological constant is given up to an exponent which is approximated by the experimentally decided density parameters of dark matter and dark energy. This yields that dark matter is one third of dark energy for all times implying an explanation of the coincidence of dark matter and dark energy. In the final state, the universe becomes dark, consisting of dark matter and dark energy.

Abstract:
The paper introduces Planck scale into the Newtonian law of gravity for
the model simplification. The terms of Newtonian gravitational force can be
separated into two parts, namely Dark Matter and Dark Energy respectively. They
are inverse relation to the distance. In the very early Universe, the novel
model gives the sum “attractive force” of all matters in the cosmos. It
indicates that Inflationary Universe firstly and then Universe expands slowly
on condition that the accelerated velocity is slowing down for ever. In the
galaxy scale, the paper gets the local “attractive force” of different galaxies
by using the novel interaction model. It shows the intercommunity property in
the formation process of different galaxies, where the matter suppresses
firstly, sharp inflates secondly, slowly expands finally. Otherwise, the novel interaction
model solves the problem about the flat rotation curves of galaxy by considering
the change of the mass ratio of Dark Energy and Dark Matter. All results of
simulation show that the core of our Universe is hollow now.