Modified Gravity Theories and Applications to Astrophysics and Cosmology

Dear Colleagues,

The general theory of relativity is considered today as being highly successful because of its verification in many experiments and its applications to cosmology and astrophysics. Since its initial formulation more than a century ago, a plethora of extended and modified theories have appeared.

This trend has not diminished with time, but, on the other hand, it seems to be increasing with additional difficulties in astronomical observations.

More prominently, we have the lingering problem of the anomalous rotation curves of galaxies and the extra lensing effects, not accounted for luminous matter. This problem is, apparently, solved in the context of standard cosmology by the so-called dark matter but it could equally be understood by modified gravity hypothesis such as MOND, scalar-vector-tensor theories and other.

In the solar system we have some unsolved problems, as follows: We have the lingering problem of the anomalous increase of the eccentricity of the moon’s orbit, as determined by lunar laser ranging techniques. The dissipative processes of a tidal origin have, to date, been unable to explain this anomaly. The flyby anomaly, that is, the anomalous orbital energy changes of spacecraft in planetary flybys, have also been discussed since the early 1990s. More recently, a breakdown of Kepler’s laws, similar to that found in the rotation curves of galaxies, has also been disclosed for wide binary stars.

The purpose of this Special Issue is to publish conventional and unconventional, but well-founded, approaches to the solution of these or any other new phenomena related to gravity. In particular, we are seeking papers in which new and original perspectives to these issues are provided as a way to stimulate the discussion in the astronomy and physics communities, in order to search for the solution of the riddle posed by many of these anomalies.

Topics of interest include (not exhaustively) the following:

Flyby anomalies

The secular increase of the eccentricity of the orbit of the moon

The faint young Sun paradox

Application of geopotential models for the Earth and other planets

Lunar laser ranging and radar ranging in the solar system

Conventional radiation effects in spacecraft navigation

Wide binaries as tests of classical gravity

Modified gravity models

Dark energy and cosmological accelerated expansion

Applications of gravity models to the anomalous rotation curves of galaxies

Bullet cluster and gravitational lensing

Modified Newtonian dynamics and applications in the solar system

Gravitational waves and tests of general relativity in strong gravity

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• Flyby anomalies
• The secular increase of the eccentricity of the orbit of the moon
• The faint young
• Sun paradox Application of geopotential models for the Earth and other planets Lunar laser ranging and radar ranging in the solar system
• Conventional radiation effects in spacecraft navigation
• Wide binaries as tests of classical gravity Modified gravity models
• Dark energy and cosmological accelerated expansion
• Applications of gravity models to the anomalous rotation curves of galaxies
• Bullet cluster and gravitational lensing
• Modified Newtonian dynamics and applications in the solar system
• Gravitational waves and tests of general relativity in strong gravity