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GGR News: -we hear that..., by David Garfinkle -Network of gravitational-wave detectors, by Stan Whitcomb Research Briefs: -New tests of general relativity, by Quentin Bailey Conference Reports: -Theory meets data analysis, by Steve…
In this paper we present a general, model independent analysis of a recently detected apparent cosmic repulsion, and discuss its potential implications for gravitational theory. In particular, we show that a negatively spatially curved…
Swift opened up a new era in the study of gamma-ray burst sources (GRB). Among a variety of discoveries made possible by Swift, here we focus on GRB090423, the event at z=8.2 which currently holds the record of the most distant celestial…
The concept of Gravitational Dipole is introduced starting from the recent discovery of negative gravitational mass (gr-qc/0005107 and physics/0205089). A simple experiment, a gravitational wave transmitter, to test this new concept of…
In creating his gravitational field equations Einstein unjustifiedly assumed that inertial mass, and its energy equivalent, is a source of gravity. Denying this assumption allows modifying the field equations to a form in which a positive…
We show that a suitably chosen position-momentum commutator can elegantly describe many features of gravity, including the IR/UV correspondence and dimensional reduction (`holography'). Using the most simplistic example based on dimensional…
A history of the problem of mathematical and physical definition for the energy-momentum of the gravity field is reviewed. As it was noted 90 years ago by Hilbert (1917), Einstein (1918), Schrodinger (1918) and Bauer (1918) within…
A brief account of the development of the concept of the gravitational constant and the debate around in in Britain at the end of the 19th century.
The historical significance of the problem of relativistic rigid rotation is reviewed in light of recently published correspondence between Einstein and the mathematician Vladimir Varicak from the years 1909 to 1913.
Exactly one hundred years ago, in May 1922, Alexander Friedmann discovered that General Relativity (GR) predicts non-stationary Universe. His equation describing the evolution of the Universe is now named after him. In this paper we briefly…
The Weak Gravity Conjecture (WGC) asserts a powerful consistency condition on gauge theories coupled to gravity, and it is widely believed that its proof will shed light on the quantum origin of gravitational interactions. Holography, and…
The light that we receive from clusters of galaxies is redshifted by the presence of the clusters' gravitational potential. This effect, known as gravitational redshift, was first detected from a sample of stacked clusters in 2011, by…
We derive new representations of the Einstein-Hilbert action in which graviton perturbation theory is immensely simplified. To accomplish this, we recast the Einstein-Hilbert action as a theory of purely cubic interactions among gravitons…
A challenge in teaching about special relativity is that a number of the theory's effects are at odds with the intuition of classical physics, as well as student's everyday experience. The relativity of simultaneity, time dilation and…
Newton's theorem of revolving orbits states that one can multiply the angular speed of a Keplerian orbit by a factor $k$ by applying a radial inverse cubed force proportional to $(1-k^2)$. In this paper we derive an extension of this…
The gravitational back-reaction on a certain type of rigidly-rotating cosmic string loop, first discovered by Allen, Casper and Ottewill, is studied at the level of the weak-field approximation. The near-field metric perturbations are…
We consider general curvature-invariant modifications of the Einstein-Hilbert action that become important only in regions of extremely low space-time curvature. We investigate the far future evolution of the universe in such models,…
The reported anomalous acceleration may be explained as the recoil of radiated waste RTG heat scattered by the back of the high gain antenna.
A metric-field approach to gravitation is presented. It is based on an idea of dependency of space-time properties on measuring instruments. Some bimetric equations that realize this idea are considered. They were tested by the binary…
In 2008 a group of NASA scientists reported an anomalous change in the speed of six spacecraft flybys of the Earth. The reported speed change for the NEAR spacecraft flyby is 13.46+-0.01 mm/s. It is known that general relativity theory…