Extended theories of gravity are alternative theories of gravity developed from the exact starting points investigated first by Albert Einstein and Hilbert. These are theories describing gravity, which are metric theory, "a linear connection" or related affine theories, or metric-affine gravitation theory. Rather than trying to discover correct calculations for the matter side of the Einstein field equations; which include inflation, dark energy, dark matter, large-scale structure, and possibly

quantum gravity Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics; it deals with environments in which neither gravitational nor quantum effects can be ignored, such as in the vi ...

; it is proposed, instead, to change the gravitational side of the equation.

Proposed theories

Hernández et al.

One such theory is also an extension to general relativity and Newton's Universal gravity law (

f(\chi)=\chi^\frac

), first proposed in 2010 by the Mexican astronomers Xavier Hernández Doring, Sergio Mendoza Ramos et al., researchers at the Astronomy Institute, at the

National Autonomous University of Mexico The National Autonomous University of Mexico ( es, Universidad Nacional Autónoma de México, UNAM) is a public research university in Mexico. It is consistently ranked as one of the best universities in Latin America, where it's also the bigges ...

. This theory is in accordance with observations of kinematics of the solar system, extended binary stars, and all types of galaxies and galactic groups and clouds. It also reproduces the gravitational lensing effect without the need of postulating dark matter. There is some evidence that it could also explain the dark energy phenomena and give a solution to the initial conditions problem. These results can be classified as a metric f(R) gravity theory, more properly an f(R,T) theory, derived from an action principle. This approach to solve the dark matter problem takes into account the

Tully–Fisher relation In astronomy, the Tully–Fisher relation (TFR) is an empirical relationship between the mass or intrinsic luminosity of a spiral galaxy and its asymptotic rotation velocity or emission line width. It was first published in 1977 by astronomers ...

as an empirical law that applies always at scales larger than the

Milgrom radius Milgrom is a surname derived from the Yiddish word for pomegranate ( מילגרוים, Milgroim) and may refer to: * Allen "Al" Milgrom (born 1950), American comic book writer * Felix Milgrom (1919-2007), Jewish Polish-American microbiologist * ...

Proposed theories

Hernández et al.

See also

References

Further reading

External links

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