I'm sorry, I don't understand what you are asking for. Could you please clarify?

Click For Summary
SUMMARY

The forum discussion centers on solving the Einstein Field Equations, specifically the (0,0) component, which relates the Einstein Tensor to the Stress-Energy Tensor. The participants establish that the energy density (T(0,0)) corresponds to mass density under the assumption of c=1, leading to the equation Einstein Tensor (upper,0,0)=8*pi*G*ρ. They also explore the relationship between the Ricci tensor and Poisson's equation, concluding that the zero-zero component of the Einstein Tensor is analogous to the second partial derivatives of the gravitational potential. The discussion emphasizes the importance of understanding the nuances of tensor notation and the implications of pressure in gravitational fields.

PREREQUISITES
  • Understanding of Einstein Field Equations (EFE)
  • Familiarity with tensor notation and operations
  • Knowledge of gravitational potential and Poisson's equation
  • Basic concepts of General Relativity and metric tensors
NEXT STEPS
  • Study the derivation of the Einstein Field Equations in General Relativity
  • Learn about the implications of the Ricci tensor in cosmology
  • Explore the relationship between gravitational potential and mass density
  • Investigate the role of pressure in the dynamics of gravitational fields
USEFUL FOR

Students and researchers in theoretical physics, particularly those focusing on General Relativity, cosmology, and gravitational theory. This discussion is beneficial for anyone looking to deepen their understanding of the mathematical foundations of Einstein's equations and their physical interpretations.

  • #121
As far as I can tell 109 isn't even close. However, it is unnecessarily cluttered with all of the G and c and M and R terms. You should just stick with A and B.
 
Physics news on Phys.org
  • #122
^
OK, I feel that there is something wrong with it. Can you check it with your Mathematica?

Also, there other non-zero Gammas which I haven't mentioned.
 
  • #123
GRstudent said:
Also, there other non-zero Gammas which I haven't mentioned.
Well, there are the obvious symmetries:
\Gamma^{\theta}_{r \theta}=\Gamma^{\theta}_{\theta r} and \Gamma^{\phi}_{r \phi}=\Gamma^{\phi}_{\phi r} and \Gamma^{\phi}_{\theta \phi}=\Gamma^{\phi}_{\phi \theta}

Beyond those the following terms are also non-zero:
\Gamma^{t}_{r t} = \Gamma^{t}_{t r}
\Gamma^{r}_{t t}
\Gamma^{r}_{\phi \phi}
 
  • #124
PeterDonis said:
Also, I'm not sure that the Gammas have to match at the boundary. The metric components themselves do, but I'm not sure the Gammas do. I'll have to check further on that.

You'll definitely see jumps in the christoffel symbols, and in the metric, if you have pressurized shells - for instance, if if you have a ball or radiation trapped in a box. They'll be sudden jumps only in the limit of very thin shells IIRC.

I suspect you won't see any jumps matching interior to exterior solutions lacking such pressure differences, but it's worth checking to be sure.

It'd be wrong to try and match an interior solution to an exterior solution where the interior pressure wasn't equal to the exterior pressure (i.e. zero for a vacuum exterior) without adding some sort of shell to acount for the pressure difference.
 
  • #125
pervect said:
It'd be wrong to try and match an interior solution to an exterior solution where the interior pressure wasn't equal to the exterior pressure (i.e. zero for a vacuum exterior) without adding some sort of shell to acount for the pressure difference.

In the particular solution in question (constant density spherical massive body surrounded by vacuum--it's discussed, for example, in MTW), the pressure is continuous at the boundary (the surface of the body)--at least, I'm pretty sure that's right--but the density is not; it jumps from its interior value to zero at the boundary. The jump in density causes a jump in the radial derivative of g_rr (g_rr itself is continuous), which shows up as a jump in \Gamma^{r}_{rr}. As far as I can tell, that is the only Christoffel symbol that is affected.
 
  • #126
Others so far:

\Gamma^{r}_{\phi\phi}=\sin^2\theta r (Br^2-1)

\Gamma^{r}_{tt}=\dfrac{0.5r(\sqrt{1-r^2B}-3 \sqrt{1-A})B(1-Br^2)}{2 \sqrt{1-r^2B}}

Please check them!
 
Last edited:
  • #127
GRstudent said:
Please check them!
Those are correct.
 
  • #128
List of Gammas:

\Gamma^{r}_{rr}=\dfrac{-rB}{(Br^2 -1)}

\Gamma^{\theta}_{\theta r }=\dfrac{1}{r}

\Gamma^{\phi}_{\phi r}=\dfrac{1}{r}

\Gamma^{\phi}_{\phi \theta} = \dfrac{1}{\tan \theta}

\Gamma^{r}_{\theta \theta}=-r(Br^2-1)

\Gamma^{\theta}_{\phi\phi}=-\sin\theta \cos\theta

\Gamma^{r}_{\phi\phi}=\sin^2\theta r (Br^2-1)

\Gamma^{r}_{tt}=\dfrac{0.5r(\sqrt{1-r^2B}-3 \sqrt{1-A})B(1-Br^2)}{2 \sqrt{1-r^2B}}
 
  • #129
I think those are correct except for \Gamma^r_{tt}
{\Gamma^r}_{tt}=-\frac{r\,B\,\sqrt{1-{r}^{2}\,B}\,\left( \sqrt{1-{r}^{2}\,B}-3\,\sqrt{A}\right) }{4}

and {\Gamma^t}_{rt} is not in the list. Calculated by Maxima ctensor package.
 
  • #130
^
Can you calculate Einstein Tensor of my Gammas?
 
  • #131
Mentz114 said:
I think those are correct except for \Gamma^r_{tt}
{\Gamma^r}_{tt}=-\frac{r\,B\,\sqrt{1-{r}^{2}\,B}\,\left( \sqrt{1-{r}^{2}\,B}-3\,\sqrt{A}\right) }{4}

and {\Gamma^t}_{rt} is not in the list. Calculated by Maxima ctensor package.
I think those are the same. The expression that Mathematica gives seems to be about halfway in-between both your expression and GRstudent's:
{\Gamma^r}_{tt}=\frac{1}{4} B r \left(3 \sqrt{1-A} \sqrt{1-B r^2}+B r^2-1\right)
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
1K
  • · Replies 8 ·
Replies
8
Views
1K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 186 ·
7
Replies
186
Views
12K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 38 ·
2
Replies
38
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 1 ·
Replies
1
Views
732