Relationship between the speed of gravity cg and the speed of light ce in the bi-metric theory of gravity is discussed. We reveal that the speed of light is a function of the speed of gravity which is a primary fundamental constant. Thus, experimental measurement of relativistic bending of light propagating in time-dependent gravitational field directly compares the speed of gravity versus the ...

Gravity drives the evolution of the Universe and is at the heart of its complexity. Einstein's field equations can be used to work out the detailed dynamics of space and time and to calculate the emergence of large-scale structure in the distribution of galaxies and radiation. Over the past few years, it has become clear that cosmological observations can be used not only to constrain different...

We study Chern-Simons (CS) gravity in the parametrized post-Newtonian (PPN) framework through a weak-field solution of the modified field equations. We find that CS gravity possesses the same PPN parameters as general relativity, except for the inclusion of a new term, proportional to the CS coupling and the curl of the PPN vector potential. This new term leads to a modification of frame draggi...

Quantum theory of dilaton gravity is studied in 2+ ǫ dimensions. Divergences are computed and renormalized at one-loop order. The mixing between the Liouville field and the dilaton field eliminates 1/ǫ singularity in the Liouville-dilaton propagator. This smooth behavior of the dilaton gravity theory in the ǫ → 0 limit solves the oversubtraction problem which afflicted the higher orders of the ...

In the context of the AdS/CFT correspondence, an explicit relation between the physical degrees of freedom of 2+1d gravity and the stress tensor of 1+1d conformal field theory is exhibited. Gravity encodes thermodynamic state variables of conformal field theory, but does not distinguish among different CFT states with the same expectation value for the stress tensor. Simply put, gravity is ther...

Until the middle of the 1990’s, string theory had a reputation for being a rather ambitious formalism that, while being the most promising candidate for unifying gravity with the Standard Model, had provided few concrete, testable predictions or applications. This changed following Maldacena’s proposal, the AdS/CFT correspondence or gauge/gravity duality [36, 2], in 1997; building on holographi...

This is an introduction to spin foam models for non-perturbative quantum gravity, an approach that lies at the point of convergence of many different research areas, including loop quantum gravity, topological quantum field theories, path integral quantum gravity, lattice field theory, matrix models, category theory, statistical mechanics. We describe the general formalism and ideas of spin foa...