Solving the Spherically Symmetric Einstein Equation

In summary, the simpler form of the Einstein equation can be obtained when the mass-energy is distributed only spherically symmetrically, but not necessarily stationary. This can be done by assuming that the metric is diagonal and taking the areal radius of the event's 2-sphere as one of the coordinates. The article provides a brief explanation of the Einstein tensor and how it can be applied to the non-vacuum case.
  • #1
Tomas Vencl
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TL;DR Summary
When suppose only spherically symmetric distribution of mass-energy, how it simpify the Einstein equation ?
Can be Einstein equation rewrited into some simpler form, when suppose only spherically symmetric (but not necessarily stationary) distribution of mass-energy ?
If yes, is there some source to learn more about it ?
Thank you.
edit: by simpler form I mean something with rather expressed derivatives, than more compact form (if this makes sense)
 
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  • #3
Tomas Vencl said:
Can be Einstein equation rewrited into some simpler form, when suppose only spherically symmetric (but not necessarily stationary) distribution of mass-energy ?

Yes. For the spherically symmetric case, there are only two unknown functions of the coordinates in the metric (a general metric with no symmetry has ten unknown functions of the coordinates, one for each of the independent metric components). The most common way of treating this case is to choose coordinates such that the metric is diagonal and the areal radius ##r## (given by ##r = \sqrt{A / 4 \pi}##, where ##A## is the radius of the 2-sphere containing the event in spacetime whose coordinates one is evaluating) is one of the coordinates. The general form of the metric with these assumptions, along with the significant components of the Einstein tensor, is given in this Insights article:

https://www.physicsforums.com/insights/short-proof-birkhoffs-theorem/

The article only considers the actual solution of the EFE for the vacuum case; but one can easily generalize what is done there to the non-vacuum case by simply putting the appropriate stress-energy tensor components (as functions of ##t## and ##r##) on the RHS of the equations.
 
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Likes vanhees71
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Thank you both, I will look at the links.
 

1. What is the Spherically Symmetric Einstein Equation?

The Spherically Symmetric Einstein Equation is a mathematical expression that describes the curvature of spacetime in a spherically symmetric system. It is a fundamental equation in general relativity and is used to study the behavior of gravity in the presence of massive objects.

2. What is the significance of solving the Spherically Symmetric Einstein Equation?

Solving the Spherically Symmetric Einstein Equation allows us to understand the behavior of gravity in the presence of massive objects, such as stars and black holes. It also helps us to make predictions about the structure of the universe and the behavior of objects within it.

3. How is the Spherically Symmetric Einstein Equation solved?

The Spherically Symmetric Einstein Equation is solved using advanced mathematical techniques, such as tensor calculus and differential geometry. It involves solving a system of partial differential equations, which can be complex and require advanced computational methods.

4. What are some applications of the Spherically Symmetric Einstein Equation?

The Spherically Symmetric Einstein Equation has many applications in astrophysics, including predicting the behavior of stars and black holes, studying the expansion of the universe, and understanding the formation of galaxies. It also has practical applications in fields such as GPS technology and satellite communication.

5. Are there any current challenges or limitations in solving the Spherically Symmetric Einstein Equation?

Yes, there are still many challenges and limitations in solving the Spherically Symmetric Einstein Equation. One major challenge is the complexity of the equations and the need for advanced mathematical techniques. Additionally, the equation does not account for quantum effects, which may be necessary for a complete understanding of gravity.

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