Weak Gravitational Field: Solving Einstein Field Eqs

Click For Summary

Discussion Overview

The discussion revolves around the application of Einstein's Field Equations (EFE) in the context of weak gravitational fields, specifically exploring the implications of a gravitational force that varies inversely with the cube of the distance (##1/r^3##). Participants are examining the theoretical framework and dimensional considerations necessary to achieve such a potential.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about the conditions required for the EFE to approximate a weak gravitational field with a ##1/r^3## dependence.
  • Another participant suggests that the question pertains more to solutions of the Laplace equation rather than general relativity (GR), noting that achieving a ##1/r^3## potential would necessitate additional spatial dimensions.
  • A participant reiterates the need for extra dimensions to obtain a ##1/r^3## potential and expresses interest in starting with a non-Newtonian gravitational law (##F = GMm/r^3##) to find a corresponding curved spacetime in 5+1 dimensions.
  • It is stated that in 5+1 dimensions, the potential behaves as ##1/r^3##, while in the conventional 3+1 dimensions, the potential behaves as ##1/r##.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the feasibility of achieving a ##1/r^3## gravitational potential within the framework of 3+1 dimensions, with some asserting the necessity of higher dimensions while others explore the implications of their proposals.

Contextual Notes

The discussion highlights the dependence on dimensionality for gravitational potentials and the unresolved nature of how to reconcile non-Newtonian laws with general relativity in lower dimensions.

deRoy
Messages
37
Reaction score
5
What do I have to do if I want the EFE's to approximate a weak gravitational field, where for example, an inversely proportional to the cube ( ##1 / r^3## ) of the distance law between the masses applies?
 
Physics news on Phys.org
What should go as ##1/r^3##? This is not really a question of GR, it is a question of the solutions to the Laplace equation, which depends on the number of dimensions. For example, to get a potential that goes as ##\sim 1/r^3## you would need to add two additional spatial dimensions.
 
Orodruin said:
What should go as ##1/r^3##? This is not really a question of GR, it is a question of the solutions to the Laplace equation, which depends on the number of dimensions. For example, to get a potential that goes as ##\sim 1/r^3## you would need to add two additional spatial dimensions.
Yes, that's exactly what I mean, I want to begin with a non-Newtonian law of universal gravitation let's say: ## F = GMm/r^3 ## then find a curved spacetime (5 + 1 dimensions) to approximate this law in weak gravitational fields.

Can I do the same for 3+1 dimensions?
 
In 5+1 dimensions the potential goes as ##1/r^3##. In 3+1 dimensions the potential goes as ##1/r##.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 0 ·
Replies
0
Views
993
  • · Replies 31 ·
2
Replies
31
Views
2K
  • · Replies 57 ·
2
Replies
57
Views
4K
  • · Replies 16 ·
Replies
16
Views
1K
  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 186 ·
7
Replies
186
Views
13K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K