Related papers: The Accelerated Universe and the Moon
Modified Newtonian dynamics (MOND) and similar proposals can (at least partially) explain the excess rotation of galaxies or the equivalent mass-discrepancy acceleration, without (or by reducing) the requirement of dark matter halos. This…
After a short history of the $\Lambda$-term it is explained why the (effective) cosmological constant is expected to obtain contributions from short-distance-physics, corresponding to an energy scale of at least 100 GeV. The actual tiny…
We discuss the idea that the accelerated Universe could be the result of the gravitational leakage into extra dimensions on Hubble distances rather than the consequence of non-zero cosmological constant.
It has been only ~15 years since the discovery of dark energy (although some may argue there were strong indications even earlier). In the short time since measurements of type Ia supernovae indicated an accelerating universe, many other…
Cosmological observations are beginning to reach a level of precision that allow us to test some of the most fundamental assumptions in our working model of the Universe. One such an assumption is that gravity is governed by the General…
In this contribution to the conference "Beyond Einstein: Historical Perspectives on Geometry, Gravitation and Cosmology in the Twentieth Century", we give a critical status report of attempts to explain the late accelerated expansion of the…
Two recent findings necessitate a closer look at the existing standard models of Particle Physics and Cosmology. These are the discovery of Neutrino oscillation, and hence a non zero mass on the one hand and, on the other, observations of…
If our Universe is allowed to absorb baby universes, one obtains a modified Friedmann equation that can explain the late time acceleration of our Universe and there is no need for a cosmological constant. In addition the modified Friedmann…
The Galileon model is a modified gravity theory that may provide an explanation for the accelerated expansion of the Universe. This model does not suffer from instabilities or ghost problems (normally associated with higher-order derivative…
Accelerating universe or the existence of a small and positive cosmological constant is probably the most pressing obstacle as well as opportunity to significantly improving the models of four-dimensional cosmology from fundamental theories…
The Lorentzian spacetime metric is replaced by an area metric which naturally emerges as a generalized geometry in quantum string and gauge theory. Employing the area metric curvature scalar, the gravitational Einstein-Hilbert action is…
Cosmic acceleration may be the result of unknown physical processes involving either new fields in high energy physics or modifications of gravitation theory. In the latter case, such modifications are usually related to the existence of…
During the past century Einstein's theory of General Relativity gave rise to an experimental triumph, however, there are still aspects of this theory to be measured or more accurately tested. One of the main challenges in experimental…
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,…
The search for the physical mechanism underlying the observational evidence for the acceleration of the recent universe is a compelling goal of modern fundamental cosmology. Here we quantitatively study a class of homogeneous and isotropic…
Recent astronomical observations indicate that the universe is accelerating. We argue that generic quintessence models that accommodate the present day acceleration tend to accelerate eternally. As a consequence the resulting spacetimes…
Understanding the space of possible theoretical explanations for the observed cosmic acceleration is a central challenge of modern cosmology. This brief document sketches selected aspects of approaches to this problem, focusing on the…
A major recent evelopment in observational cosmology has been an accurate measurement of the luminosity distance-redshift relation out to redshifts z=0.8 from Type Ia supernova standard candles. The results have been argued as evidence for…
We present a bi-metric theory of gravity containing a length scale of galactic size. For distances less than this scale the theory satisfies the standard tests of General Relativity. For distances greater than this scale the theory yields…
This paper describes how the non-gravitational contribution to Galactic Velocity Rotation Curves can be explained in terms of a negative Cosmological Constant ($\Lambda$). It will be shown that the Cosmological Constant leads to a velocity…