A Suggested Alternative to Dark Matter in Galaxies: I. Theoretical Considerations. (arXiv:2008.01819v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Sabat_H/0/1/0/all/0/1">Hanna A. Sabat</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Bani_Abdoh_R/0/1/0/all/0/1">Raed Z. Bani-Abdoh</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Mousa_M/0/1/0/all/0/1">Marwan S. Mousa</a> (2) ((1) Regional Center for Space Science &amp; Technology Education for Western Asia (RCSSTE-WA), Amman, Jordan, (2) Mutah University, Department of Physics, Karak, Jordan)

Dark matter is the generally accepted paradigm in astrophysics and cosmology
as a solution to the higher rate of rotation in galaxies, among other things.
But since there are still some problems encountered by the standard dark matter
paradigm at this scale, we have resorted to an alternative solution, similar to
Milgrom’s MOND. Here, we have assumed that: (i) either the gravitational
constant, G, is a function of distance (scale): G = G(r), or, (ii) the
gravitational-to-inertial mass ratio, mg/mi, is a function of distance (scale):
f(r). We have used a linear approximation of each function, from which two new
parameters appeared that have to be determined: G1, the first-order coefficient
of gravitational coupling, and C1, the first-order coefficient of
gravitational-to-inertial mass ratio. In the current part of this research, we
have generated simplified theoretical rotation curves for galaxies by varying
the parameters. We have concluded that our model gives a qualitatively and
quantitatively acceptable behavior of the galactic rotation curves. The values
of the 1st-order coefficients that give quantitatively acceptable description
of galactic rotation curves are: G1 between around 10^-31 to 10^-30 m^2 s^-2
kg^-1; and, C1 between 10^-21 to 10^-20 m^-1. Furthermore, our model implies
the existence of a critical distance at which the MOND effects become
significant rather than a critical acceleration. In fact, Milgrom’s MOND
converges with our model if the critical acceleration is not a constant but a
linear function of mass.

Dark matter is the generally accepted paradigm in astrophysics and cosmology
as a solution to the higher rate of rotation in galaxies, among other things.
But since there are still some problems encountered by the standard dark matter
paradigm at this scale, we have resorted to an alternative solution, similar to
Milgrom’s MOND. Here, we have assumed that: (i) either the gravitational
constant, G, is a function of distance (scale): G = G(r), or, (ii) the
gravitational-to-inertial mass ratio, mg/mi, is a function of distance (scale):
f(r). We have used a linear approximation of each function, from which two new
parameters appeared that have to be determined: G1, the first-order coefficient
of gravitational coupling, and C1, the first-order coefficient of
gravitational-to-inertial mass ratio. In the current part of this research, we
have generated simplified theoretical rotation curves for galaxies by varying
the parameters. We have concluded that our model gives a qualitatively and
quantitatively acceptable behavior of the galactic rotation curves. The values
of the 1st-order coefficients that give quantitatively acceptable description
of galactic rotation curves are: G1 between around 10^-31 to 10^-30 m^2 s^-2
kg^-1; and, C1 between 10^-21 to 10^-20 m^-1. Furthermore, our model implies
the existence of a critical distance at which the MOND effects become
significant rather than a critical acceleration. In fact, Milgrom’s MOND
converges with our model if the critical acceleration is not a constant but a
linear function of mass.

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