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Modified Newtonian dynamics (MOND) is a theory that proposes a modification of Newton's laws to account for observed properties of galaxies. Modifying Newton's law of gravity results in modified gravity, while modifying Newton's second law results in modified inertia. The latter has received little attention compared to the modified gravity ...
The gauge-invariant perturbation theory is based on developments by Bardeen (1980), [7] Kodama and Sasaki (1984) [8] building on the work of Lifshitz (1946). [9] This is the standard approach to perturbation theory of general relativity for cosmology. [10]
Depending on which features of general relativity and quantum theory are accepted unchanged, and on what level changes are introduced, [204] there are numerous other attempts to arrive at a viable theory of quantum gravity, some examples being the lattice theory of gravity based on the Feynman Path Integral approach and Regge calculus, [191 ...
The Einstein field equations (EFE) may be written in the form: [5] [1] + = EFE on the wall of the Rijksmuseum Boerhaave in Leiden, Netherlands. where is the Einstein tensor, is the metric tensor, is the stress–energy tensor, is the cosmological constant and is the Einstein gravitational constant.
Both Brans–Dicke theory and general relativity are examples of a class of relativistic classical field theories of gravitation, called metric theories.In these theories, spacetime is equipped with a metric tensor, , and the gravitational field is represented (in whole or in part) by the Riemann curvature tensor, which is determined by the metric tensor.
The theory claims to be consistent with both the macro-level observations of Newtonian gravity as well as Einstein's theory of general relativity and its gravitational distortion of spacetime. Importantly, the theory also explains (without invoking the existence of dark matter and tweaking of its new free parameters ) why galactic rotation ...
Assuming SI units, F is measured in newtons (N), m 1 and m 2 in kilograms (kg), r in meters (m), and the constant G is 6.674 30 (15) × 10 −11 m 3 ⋅kg −1 ⋅s −2. [12] The value of the constant G was first accurately determined from the results of the Cavendish experiment conducted by the British scientist Henry Cavendish in 1798 ...
In physics, f(R) is a type of modified gravity theory which generalizes Einstein's general relativity. f(R) gravity is actually a family of theories, each one defined by a different function, f, of the Ricci scalar, R. The simplest case is just the function being equal to the scalar; this is general relativity.