Related papers: Evolution of dark matter velocity dispersion
Can local fluctuations of a ``Quintessence'' scalar field play a dynamical role in the gravitational clustering and cosmic structure formation process? We address this question in the general framework of scalar-tensor theories of gravity.…
We present a simple model for the shape of the distribution function of galaxy peculiar velocities. We show how both nonlinear and linear theory terms combine to produce a distribution which has an approximately Gaussian core with…
We propose a new scenario for the onset of positive acceleration of our Universe based on symmetry breaking in coupled dark energy scalar field model. In a symmetry breaking process where the scalar field rolls down its own potential, the…
Models with vector fields acquiring a non-vanishing vacuum expectation value along one spatial direction have been proposed to sustain a prolonged stage of anisotropic accelerated expansion. Such models have been used for realizations of…
In the framework of teleparallel equivalent of general relativity, we study a gravity theory where a scalar field beyond its minimal coupling, is also coupled with the vector torsion through a non-minimal derivative coupling. After a…
String effective theories contain a dilaton scalar field which couples to gravity, matter and radiation. In general, particle masses will have different dilaton couplings. We can always choose a conformal frame in which baryons have…
The dissipation of energy from local velocity perturbations in the cosmological fluid affects the time evolution of spatially averaged fluid dynamic fields and the cosmological solution of Einstein's field equations. We show how this…
We study the evolution of linear density perturbations in a large spherical void universe which accounts for the acceleration of the cosmic volume expansion without introducing dark energy. The density contrast of this void is not large…
The traditional "explanation" for the observed acceleration of the universe is the existence of a positive cosmological constant. However, this can hardly be a truly convincing explanation, as an expanding universe is not expected to have a…
In a previous paper (Ref. [1]) the presence of dark energy in our universe was explained as the fingerprint of a comprehensive, much older and expanding multiverse with positive spatial curvature, whose space-time is spanned by this energy,…
In this paper we show that a universe dominated by two components, namely domain walls and dissipative dark matter such that the former slowly decays into the latter may drive power law cosmological acceleration consistent with the high…
We analyze a toy model describing an empty spacetime in which the motion of a test mass (and the trajectories of photons) evidence the presence of a continuous and homogeneous distribution of matter; however, since the energy-momentum…
We investigate whether interaction between massive neutrinos and quintessence scalar field is the origin of the late time accelerated expansion of the universe. We present cosmological perturbation theory in neutrinos probe interacting…
All observational evidence for dark matter and dark energy is so far exclusively gravitational. Hence, the dark sector may be equivalently described by a theory of the spacetime metric whose dynamics is affected by interactions with an…
We propose a simple model in which the cosmological dark matter consists of particles whose mass increases with the scale factor of the universe. The particle mass is generated by the expectation value of a scalar field which does not have…
Observations provide increasingly strong evidence that the universe is accelerating. This revolutionary advance in cosmological observations confronts theoretical cosmology with a tremendous challenge, which it has so far failed to meet.…
We propose a new class of quintessence models in which late times oscillations of a scalar field give rise to an effective equation of state which can be negative and hence drive the observed acceleration of the universe. Our ansatz…
On the basis of hypotheses, that a density of weakly interacting particles in the Universe has an order of nuclear matter density or more the Lagrangian is offered, through which one can be obtained a propagator of a vector boson with a…
Effects of velocity dispersion of dark matter particles on the CMB TT power spectrum and on the matter linear power spectrum are investigated using a modified CAMB code. Cold dark matter originated from thermal equilibrium processes does…
We extend mass scale sequence to a mass tree. From mass tree, the evolution of the universe is described by three stages: chaos, inflation and expansion. The first two stages have c mutations and the inflation appears as a step by step…