Related papers: Gravitational Merging as a Possible Source for the…
In 'modified' gravity the observed acceleration of the universe is explained by changing the gravitational force law or the number of degrees of freedom in the gravitational sector. Both possibilities can be tested by measurements of…
We consider f(R,T) modified theory of gravity in which, in general, the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor. We indicate that in this type of the theory,…
With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realized. We show that a confirmation of equality to the speed of…
The Universe is modeled as a binary mixture whose constituents are described by a van der Waals fluid and by a dark energy density. The dark energy density is considered either as the quintessence or as the Chaplygin gas. The irreversible…
The generalized Chaplygin gas (GCG) model allows for an unified description of the cosmologically recent accelerated expansion of the Universe and of the evolution of energy density perturbations. This dark energy - dark matter unification…
Possibility of gravitational repulsion in General Relativity is discussed and astronomical data in favor of cosmological acceleration are described. The problem of vacuum energy is emphasized and possible ways of its solution are indicated.…
The properties of cosmic shock waves are studied through numerical simulations in two cosmological scenarios (SCDM and LCDM). The scaling relations for the average radius and velocity associated with the accretion shocks are somewhat…
We consider a possible connection between matter and cosmological constant $\Lambda$ via the Newtonian cosmic potential of the matter within the expanding particle horizon. Consistent with GR, an increasing potential may drive the metric…
We present a mechanism for the emergence of cosmic acceleration within the mean-field approximation of Group Field Theory models of quantum gravity. Depending on the interaction type, the resulting cosmological dynamics can either feature a…
There is marginal evidence that the quintessential form of matter responsible for the acceleration of the universe observed today has ratio between pressure and energy density $w<-1$. Such a regime, called superacceleration, cannot be…
The equation of state of an energy density may be significantly modified by coupling it to another energy density. In the light of this observation we check the possibility of producing cosmic accelerated expansion in this way. In…
We obtain a solution for the hydrodynamic outflow of the polytropic gas from the gravitating center, in presence of the uniform Dark Energy (DE). The antigravity of DE is enlightening the outflow and make the outflow possible at smaller…
Observations suggest that nearly seventy per cent of the energy density in the universe is unclustered and exerts negative pressure. Theoretical understanding of this component (`dark energy'), which is driving an accelerated expansion of…
Recently we proposed that the acceleration of the Universe could be due to gravity leaking to extra dimensions. This scenario gives an alternative to the cosmological constant or quintessence. In [astro-ph/0106274] the authors claimed that…
Growing neutrino quintessence solves the coincidence problem for dark energy by a growing cosmological value of the neutrino mass which emerges from a cosmon-neutrino interaction stronger than gravity. The cosmon-mediated attraction between…
While the standard model accurately describes data at the electroweak scale without inclusion of gravity, beyond the standard model physics is increasingly intertwined with gravitational phenomena and cosmology. Thus gravity mediated…
We perform a phase space analysis of a generalized modified gravity theory with nonminimally coupling between geometry and matter. We apply the dynamical system approach to this generalized model and find that in the cosmological context,…
A mechanism for suppressing the cosmological constant is described, using a superconducting analogy in which fermions coupled to gravitons are in an unstable false vauum. The coupling of the fermions to gravitons and a screened attractive…
Most of the models leading to a current state of cosmic accelerated expansion fail to address the coincidence problem, i.e., that the dark energy density and the energy density of the matter fluid are of the same order precisely today. We…
We consider a hypothesis that the closed Universe was formed on the other side of the event horizon of a black hole existing in another universe. That black hole appears in the Universe as a boundary white hole, and its rest frame in…