The currently observed accelerated expansion of the Universe suggests that cosmic flow dynamics is dominated by some unknown form of dark energy characterized by a large negative pressure. This picture comes out when such a new ingredient, beside baryonic and dark matter, is considered as a source in the r.h.s. of the field equations. Essentially, it should be some form of un-clustered, non-zer...

We develop a parameterized post-Friedmann (PPF) framework which describes three regimes of modified gravity models that accelerate the expansion without dark energy. On large scales, the evolution of scalar metric and density perturbations must be compatible with the expansion history defined by distance measures. On intermediate scales in the linear regime, they form a scalar-tensor theory wit...

Emergent gravity can be applied to a large $N$ matrix model by considering the vacuum of noncommutative (NC) Coulomb branch that satisfies Heisenberg algebra. Due fact IR fluctuations in NC always pair with UV fluctuations, this UV/IR mixing is extendable macroscopic scale. These are described four-dimensional $U(1)$ gauge theory. The order parameter for given random four-vectors have their own...

We explore a new horizon of modified gravity from the viewpoint of the particle physics. As a concrete example, we take the F (R) gravity to raise a question: can a scalar particle (“scalaron”) derived from the F (R) gravity be a dark matter candidate? We place the limit on the form of function F (R) from the constraint on the scalaron as a dark matter. The role of the screening mechanism and c...

We point out that extended gravity theories, the Lagrangian of which is an arbitrary function of scalar curvature R, are equivalent to a class of the scalar tensor theories of gravity. The corresponding gravity theory is ω = 0 BransDicke gravity with a potential for the Brans-Dicke scalar field, which is not compatible with solar system experiments if the field is very light: the case when such...

The dark energy problem is studied based on the approach associated with the cosmological term in General Relativity that is considered as a dynamic quantity. It is shown that a quantum field theory of the Early Universe (Planck scales) and its limiting transition at low energy play a significant role. Connection of this problem with Verlinde’s new (entropic) approach to gravity is revealed wit...

We show that there is a generic transport of energy between the scalar field generated by the conformal transformation of higher order gravity theories and the matter component. We give precise relations of this exchange and show that, unless we are in a stationary spacetime, slice energy is not generically conserved. These results translate into statements about the relative behaviour of ordin...

Article history: Received 18 October 2015 Received in revised form 25 January 2016 Accepted 17 February 2016 Available online 23 February 2016 Editor: M. Cvetič The non-relativistic versions of the generalized Poincaré algebras and generalized AdS-Lorentz algebras are obtained. These non-relativistic algebras are called, generalized Galilean algebras of type I and type II and denoted by GBn and...