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General Relativity receives quantum corrections relevant at macroscopic distance scales and near event horizons. These arise from the conformal scalar degrees of freedom in the extended effective field theory of gravity generated by the…
We discuss the possibility that accreting black hole systems can be sources for dark matter flux through several different mechanisms. We firstly discuss two types of systems: coronal thermal plasmas around supermassive black holes in…
We study the origin of dark matter based on the ghost-free bigravity theory with twin matter fluids. The present cosmic acceleration can be explained by the existence of graviton mass, while dark matter is required in several cosmological…
We consider the possibility of getting accelerated expansion and w=-1 crossing in the context of a braneworld cosmological setup, endowed with a bulk energy-momentum tensor. For a given ansatz of the bulk content, we demonstrate that the…
The particles of a dark matter due to gravitational interaction deviate from straight trajectories in the vicinity of a massive body. This causes their density to become inhomogeneous. The developed density contrast causes a gravitation…
We present some cosmological solutions of Brans-Dicke theory, characterized by a decaying vacuum energy density and by a constant relative matter density. With these features, they shed light on the cosmological constant problems, leading…
In the standard cosmological model the dark energy (DE) and nonrelativistic (NR) matter densities are observationally determined to be comparable at the present time, in spite of their greatly different evolution histories. This `cosmic…
The rotation curves of some star forming massive galaxies at redshift two decline over the radial range of a few times the effective radius, indicating a significant deficit of dark matter (DM) mass in the galaxy centre. The DM mass deficit…
The evolution of the dark matter distribution at the Galactic center is analyzed, which is caused by the combination of gravitational scattering on Galactic bulge stars and absorption by a supermassive black hole at the center of the bulge.…
The observed late-time acceleration of the cosmic expansion constitutes a fundamental problem in modern theoretical physics and cosmology. In an attempt to weight the validity of a large number of dark energy models, I use the recent…
In a recent work we have argued that nosy energy momentum diffusion due to space-time discreteness at the Planck scale (naturally expected to arise from quantum gravity) can be responsible for the generation of a cosmological constant…
A recent study by Farnes (2018) proposed an alternative cosmological model in which both dark matter and dark energy are replaced with a single fluid of negative mass. This paper presents a critical review of that model. A number of…
In this work we investigate the accretion of cosmological fluids onto an intermediate-mass black hole at the centre of a globular cluster, focusing on the influence of the parent stellar system on the accretion flow. We show that the…
The behavior of the angular velocity of a test particle moving in a stable circular orbit in the vacuum on the brane is considered. In the brane world scenario, the four dimensional effective Einstein equation acquire extra terms, called…
The effective Friedmann equation describing the evolution of the brane Universe in the cosmology of the Randall-Sundrum model includes a dark (or mirage or Weyl) radiation term. The brane evolution can be interpreted as the motion of the…
The mysterious `dark energy' needed to explain the current observations, poses a serious confrontation between fundamental physics and cosmology. The present crisis may be an outcome of the (so far untested) prediction of the general theory…
Mounting observational data confirm that about 73% of the energy density consists of dark energy which is responsible for the current accelerated expansion of the Universe. We present observational evidences and dark energy projects. We…
Observationally, the universe appears virtually critical. Yet, there is no simple explanation for this state. In this article we advance and explore the premise that the dynamics of the universe always seeks equilibrium conditions.…
The accelerating expansion of the universe is the most surprising cosmological discovery in many decades. In this short review, we briefly summarize theories for the origin of cosmic acceleration and the observational methods being used to…
The assumption that our Universe is close to a late time fixed point of the equations of cosmology, leads to a modification of the latter to include energy exchange between the matter and the "dark energy". The brane-world scenario provides…