相关论文: Mass-Varying Massive Gravity with k-essence

We analytically and numerically show that the acceleration of the cosmic expansion could be explained by a Quadratic Gravity model which is known to be able to trigger sufficient inflation, with neither negative pressure matter nor…

K-essence Lagrangian is studied in the context of an early universe epoch when time is very small. Equation of state parameter as well as deceleration parameter , indicates an accelerated expansion of the universe at an early epoch of time…

We consider a modified gravity model with a massive graviton, but which nevertheless only propagates two gravitational degrees of freedom and which is free of ghosts. We show that non-singular bouncing cosmological background solutions can…

The late-time cosmic acceleration may be due to infra-red modifications of General Relativity. In particular, we consider a maximal extension of the Hilbert-Einstein action and analyze several interesting features of the theory. Generally,…

We show how, by considering the cumulative effect of tiny quantum gravitational fluctuations over very large distances, it may be possible to: ($a$) reconcile nucleosynthesis bounds on the density parameter of the Universe with the…

We introduce a cosmological model in the framework of Generalised Massive Gravity. This theory is an extension of non-linear massive gravity with a broken translation symmetry in the St\"uckelberg space. In a recent work, we showed the…

In this presentation prepared for a general audience, we briefly mention the shortcomings of standard model of universe. We then focus on the late time inconsistency of the model dubbed age crisis whose resolution requires the presence of a…

For variable gravity models the strength of gravity, as measured by Newton's ``constant'' or the Planck mass, depends on the value of a scalar field, the cosmon. We discuss two simple four-parameter models with a quadratic or constant…

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…

Scalar-tensor theories of gravity that embrace conformal coupling to the scalar curvature are the focal point of cosmology on discussions of inflation and late-time accelerating universe. Although there exists a stringent nucleo-synthesis…

I briefly discuss some attempts to construct a consistent modification to General Relativity (GR) that might explain the observed late-time acceleration of the universe and provide an alternative to dark energy. I mention the issues facing…

We find that the quantum of gravity, the graviton, has time-varying mass (the gomidium), and radius (the somium); both vary with the inverse of R; and its frequency is given by Hubble's parameter. Dark matter can be made of such gravitons.…

Here, non-minimally coupled tachyon to gravity is considered as a source of "dark energy". It is demonstrated that with expansion of the universe, tachyon dark energy decays to "dark matter" providing a solution to "cosmic coincidence…

We discuss that it is quite possible to realize the smooth transition of the universe between a matter/radiation dominated deceleration and a dark energy dominated acceleration, even with a variation of proton-to-electron mass ratio. The…

The simplest gauge gravitation theory in Riemann-Cartan space-time leading to the solution of the problem of cosmological singularity and dark energy problem is investigated with purpose to solve the dark matter problem. It is shown that…

In cosmology it has become usual to introduce new entities as dark matter and dark energy in order to explain otherwise unexplained observational facts. Here, we propose a different approach treating spacetime as a continuum endowed with…

Gravitational waves (GWs) provide a new tool to probe the nature of dark energy (DE) and the fundamental properties of gravity. We review the different ways in which GWs can be used to test gravity and models for late-time cosmic…

We consider a model of dark energy/matter unification based on a k-essence type of theory similar to tachyon condensate models. Using an extension of the general relativistic spherical model which incorporates the effects of both pressure…

The general k-essence Lagrangian for the existence of cosmological scaling solutions is derived in the presence of multiple scalar fields coupled to a barotropic perfect fluid. In addition to the scaling fixed point associated with the…

There is evidence that Newton and Einstein's theories of gravity cannot explain the dynamics of a universe made up solely of baryons and radiation. To be able to understand the properties of galaxies, clusters of galaxies and the universe…