Related papers: Is Cosmic Acceleration Really Recent?
The current standard cosmological model is constructed within the framework of general relativity with a cosmological constant $\Lambda$, which is often associated with dark energy, and phenomenologically explains the accelerated cosmic…
As shown by Parker and Raval, quantum field theory in curved spacetime gives a possible mechanism for explaining the observed recent acceleration of the universe. This mechanism, which differs in its dynamics from quintessence models,…
The cosmographic expansion history of the universe is investigated by using the 557 type Ia supernovae from the Union2 Compilation set along with the current estimates involving the product of the CMB acoustic scale $\ell_{A}$ and the BAO…
This study investigates the cosmological dynamics of an accelerating universe within the framework of teleparallel gravity using an exponential f(T) functional form. To obtain exact cosmological solutions, a hybrid scale factor is employed…
The homogeneous expansion history H(z) of our universe measures only kinematic variables, but cannot fix the underlying dynamics driving the recent acceleration: cosmographic measurements of the homogeneous universe, are consistent with…
We provide a consistency relation between cosmological observables in general relativity with the cosmological constant. Breaking of this relation at any redshift would imply the breakdown of the hypothesis of the cosmological constant as…
In this paper we provide both a diagnosis and resolution of the cosmological constant problem, one in which a large (as opposed to a small) cosmological constant $\Lambda$ can be made compatible with observation. We trace the origin of the…
We show that cosmic acceleration can arise due to very tiny corrections to the usual gravitational action of General Relativity of the form $R^n$, with $n<0$. This eliminates the need for dark energy, though it does not address the…
A new expression to the total age of the Universe is derived in terms of the average deceleration parameter. This kinematic result holds regardless of the curvature of the universe as well as of the underlying gravity theory. It remains…
The main argument that Universe is currently expanding is observed redshift increase by distance. However, this conclusion may not be correct, because cosmological redshift depends only on the scaling factors, the change in the size of the…
We probe the recent cosmic expansion by directly reconstructing the deceleration parameter $q(z)$ at recent times with a linear expansion at $z=0$ using the low redshift SNIa and BAO data. Our results show that the observations seem to…
It is shown here that a dynamical Planck mass can drive the scale factor of the universe to accelerate. The negative pressure which drives the cosmic acceleration is identified with the unusual kinetic energy density of the Planck field. No…
General relativistic entropic acceleration theory may explain the present cosmic acceleration from first principles without the need of introducing a cosmological constant. Following the covariant formulation of non-equilibrium phenomena in…
It is generally argued that the present cosmological observations support the accelerating models of the universe, as driven by the cosmological constant or `dark energy'. We argue here that an alternative model of the universe is possible…
Astronomical observations have shown that the expansion of the universe is at present accelerating, in a way consistent with the presence of a positive cosmological constant. This is a major puzzle, because we do not understand: why the…
The strong equivalence principle is extended in application to averaged dynamical fields in cosmology to include the role of the average density in the determination of inertial frames. The resulting cosmological equivalence principle is…
From an observational perspective cosmology is today in excellent shape - advances in instrumentation and data processing have enabled us to study the universe in detail back to when the first galaxies formed, map the fluctuations in the…
The present rate of the expansion of our Universe, the Hubble constant, can be predicted from the cosmological model using measurements of the early Universe, or more directly measured from the late Universe. But as these measurements…
We use standard general relativity to illustrate and clarify several common misconceptions about the expansion of the Universe. To show the abundance of these misconceptions we cite numerous misleading, or easily misinterpreted, statements…
So far there is only indirect evidence that the Universe is undergoing an accelerated expansion. The evidence for cosmic acceleration is based on the observation of different objects at different distances, and requires invoking the…