Angular velocity calculation from Schwarzschild metric

In summary, the conversation discusses calculating the angular velocity using the Schwarzschild metric. Two different methods are suggested, one using the Lagrangian over the t variable and the other using a new variable, τ. Both methods result in the same equation for dφ/dt, showing that the angular velocity does not depend on dr/dt. However, the speaker is unsure if their calculations are correct and requests clarification on the problem statement.
  • #1
fourvector
1
0
Hello,

I need to find the angular velocity using Schwarzschild metric.
At first I wrote the metric in general form and omitted the co-latitude:
ds2=T*dt2+R*dr2+Φ*dφ2

and wrote a Lagrangian over t variable:
L = √(T+R*(dr/dt)2+Φ*(dφ/dt)2)

now I can use the Euler–Lagrange equations for φ variable and note that L does not depend on φ.
dL/d(dφ/dt) = const => Φ*(dφ/dt) / L = const => dφ/dt = const * L / Φ

The result is that dφ/dt depends on dr/dt because L contains dr/dt term.

But there is one more way that I can calculate the dφ/dt.
I can write the Lagrangian over new τ variable:
L = √(T*(dt/dτ)2+R*(dr/dτ)2+Φ*(dφ/dτ)2)

I can do the same calculations for dφ/dτ and dt/dτ variables:

dL/d(dφ/dτ) = const => Φ*(dφ/dτ) / L = const => dφ/dτ = const * L / Φ
dL/d(dt/dτ) = const => T*(dt/dτ) / L = const => dt/dτ = const * L / T

Now I can divide one over another and get
dφ/dt = const * T / Φ

The result is that the angular velocity does not depend on dr/dt.

Could someone help me what is wrong with one of my calculation?
 
Physics news on Phys.org
  • #2
The angular velocity of what?
Please give the full and exact problem statement.
 

Related to Angular velocity calculation from Schwarzschild metric

1. What is the Schwarzschild metric?

The Schwarzschild metric is a mathematical representation of the curvature of spacetime around a non-rotating, spherically symmetric mass. It is a solution to Einstein's field equations in general relativity, and it describes the geometry of space and time in the vicinity of a massive object.

2. How is angular velocity calculated from the Schwarzschild metric?

The angular velocity can be calculated from the Schwarzschild metric by taking the derivative of the metric with respect to the azimuthal coordinate and then dividing by the metric coefficient for the azimuthal coordinate. This calculation yields the angular velocity at a specific radial distance from the mass.

3. What is the significance of calculating angular velocity from the Schwarzschild metric?

The calculation of angular velocity from the Schwarzschild metric is significant because it allows us to understand the behavior of objects in the vicinity of a massive object, such as a black hole. This calculation helps us understand the effects of gravity and how it affects the motion of objects in space.

4. Can angular velocity be calculated for any mass using the Schwarzschild metric?

Yes, the Schwarzschild metric can be used to calculate the angular velocity for any non-rotating, spherically symmetric mass. This includes objects like planets, stars, and even black holes. However, the calculation may become more complex for rotating masses.

5. Are there any limitations to using the Schwarzschild metric for calculating angular velocity?

Yes, there are limitations to using the Schwarzschild metric for calculating angular velocity. This metric assumes a non-rotating, spherically symmetric mass, so it may not accurately describe the behavior of objects with different shapes or rotation. Additionally, at very small distances from the mass, the effects of quantum mechanics become important and the Schwarzschild metric is no longer accurate.

Similar threads

  • Introductory Physics Homework Help
Replies
13
Views
1K
  • Special and General Relativity
Replies
1
Views
2K
  • Special and General Relativity
Replies
2
Views
810
  • Calculus and Beyond Homework Help
Replies
1
Views
2K
  • Calculus and Beyond Homework Help
Replies
6
Views
580
  • Special and General Relativity
Replies
9
Views
1K
  • Special and General Relativity
2
Replies
42
Views
3K
  • Special and General Relativity
2
Replies
50
Views
3K
  • Special and General Relativity
Replies
7
Views
1K
Replies
6
Views
2K
Back
Top