Radial acceleration for spherically symmetric systems in GR

In summary, the conversation was about modified gravity theories and their use in understanding galaxies with no dark matter. The author used four theories and provided a radial acceleration relation for each. The results were compared with those of GR, but the individual was looking for a single equation for the acceleration in GR for spherically symmetric systems. It was suggested to consult the books "Gravitation" and "Gravity: An Introduction to Einstein's General Relativity" as well as the website Hyperphysics for possible resources.
  • #1
FluteGuy
1
0
Hello, I was reading few papers discussing modified gravity theories and their use in understanding galaxies with no dark matter by checking for anomalous velocity dispersion. Now, the author was using 4 gravity theories MOND, Weyl, MOG and Emergent gravity. The thing is he had provided the radial acceleration relation that he had used for all of them. After finding the result, he had plotted it along with GR (for no dark matter) as well. Now, I have been looking for resources to get a single radial acceleration relation in GR for spherically symmetric system. All I could find was a set of equations in different book. If you know some literature with that, do tell me. I am trying to reproduce the results of that paper myself. Thank you.

Paper: [1908.07160] Modified Gravity Theories in Light of the Anomalous Velocity Dispersion of NGC1052-DF2 (arxiv.org)
 
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  • #2
I recommend looking into the book "Gravitation" by Charles W. Misner, Kip S. Thorne, and John A. Wheeler for an equation for the acceleration in GR for a spherically symmetric system. This book is widely regarded as the classic text on general relativity. It provides a comprehensive treatment of the subject and includes equations for the acceleration in GR for a spherically symmetric system. Additionally, the book "Gravity: An Introduction to Einstein's General Relativity" by James B. Hartle also features a section on GR and its application to spherically symmetric systems. Finally, the website Hyperphysics (http://hyperphysics.phy-astr.gsu.edu/hbase/gr.html) provides a discussion of the equations of motion in GR and includes an equation for the radial acceleration in a spherically symmetric system.
 

1. What is radial acceleration in the context of GR?

Radial acceleration refers to the acceleration experienced by an object moving in a straight line towards or away from the center of a spherically symmetric system, such as a black hole or a star, in the framework of General Relativity (GR). This acceleration is caused by the curvature of spacetime around massive objects and is a fundamental concept in understanding the behavior of objects in the presence of strong gravitational fields.

2. How is radial acceleration calculated in GR?

In GR, radial acceleration is calculated using the Einstein field equations, which describe the relationship between the curvature of spacetime and the distribution of matter and energy. The equation for radial acceleration involves the mass and radius of the spherically symmetric system, as well as the speed and distance of the object from the center of the system. It also takes into account the effects of the system's gravitational potential on the object's motion.

3. What are some real-world examples of radial acceleration in GR?

One example of radial acceleration in GR is the motion of planets around the sun. The curvature of spacetime caused by the sun's mass results in the planets experiencing a radial acceleration towards the sun, keeping them in orbit. Another example is the motion of stars in a galaxy, where the gravitational potential of the galaxy's central mass causes the stars to experience radial acceleration towards the center.

4. How does radial acceleration in GR differ from Newtonian physics?

In Newtonian physics, radial acceleration is solely dependent on the mass and distance of the object from the center of the system. However, in GR, the equation for radial acceleration also takes into account the curvature of spacetime caused by the system's mass and the object's velocity. This means that in strong gravitational fields, such as those near black holes, the predictions of GR may differ significantly from those of Newtonian physics.

5. Can radial acceleration be observed or measured?

Yes, radial acceleration can be observed and measured in various astrophysical contexts, such as the motion of stars and galaxies. In fact, the discovery of the accelerated expansion of the universe in the late 1990s was made possible by measuring the radial acceleration of distant supernovae. However, measuring radial acceleration in GR can be challenging, as it requires precise measurements and calculations of the mass and distance of the objects involved.

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