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Scalar–tensor–vector gravity (STVG) [1] is a modified theory of gravity developed by John Moffat, a researcher at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario. The theory is also often referred to by the acronym MOG ( MO dified G ravity ).
Indeed, the theory he finally arrived at in 1915, general relativity, is a tensor theory, not a scalar theory, with a 2-tensor, the metric, as the potential. Unlike his 1913 scalar theory, it is generally covariant, and it does take into account the field energy–momentum–stress of the electromagnetic field (or any other nongravitational field).
An action of such a gravitational scalar–tensor theory can be written as follows: = [() () + (,)], where is the metric determinant, is the Ricci scalar constructed from the metric , is a coupling constant with the dimensions , () is the scalar-field potential, is the material Lagrangian and represents the non-gravitational fields.
Tensor–vector–scalar gravity (TeVeS), [1] developed by Jacob Bekenstein in 2004, is a relativistic generalization of Mordehai Milgrom's Modified Newtonian dynamics (MOND) paradigm. [2] [3] The main features of TeVeS can be summarized as follows: As it is derived from the action principle, TeVeS respects conservation laws;
As the electromagnetic field is characterized by an antisymmetric rank-2 tensor, there is an obvious possibility for a unified theory: a nonsymmetric tensor composed of a symmetric part representing gravity, and an antisymmetric part that represents electromagnetism. Research in this direction ultimately proved fruitless; the desired classical ...
Step 1: Identify the variables, which may include: (a) dynamical gravitational variables such as the metric , scalar field , vector field , tensor field and so on; (b) prior-geometrical variables such as a flat background metric , cosmic time function , and so on; (c) matter and non-gravitational field variables.
Vector fields are contravariant rank one tensor fields. Important vector fields in relativity include the four-velocity, = ˙, which is the coordinate distance travelled per unit of proper time, the four-acceleration = ¨ and the four-current describing the charge and current densities. Other physically important tensor fields in relativity ...
Bi-scalar tensor vector gravity theory (BSTV) [1] is an extension of the tensor–vector–scalar gravity theory . [2] TeVeS is a relativistic generalization of Mordehai Milgrom's Modified Newtonian Dynamics MOND paradigm proposed by Jacob Bekenstein. [3] BSTV was proposed by R.H.Sanders.