Please give me some clues about the calculations for a non-rotating black hole

In summary, there is a discrepancy in the dimensions of the right-hand side of equation (8.13) in the given conversation. It is suggested that the argument of the ##ln## function should be adjusted to ##|r/r^* - 1|## instead of ##|r - r^*|## for consistency. The conversation also mentions the use of Kruskal coordinates in general relativity, with reference to Sean Carroll's notes on the subject. It is noted that Carroll's notation for the coordinates is similar to that used in the conversation, with minor differences in the symbols used.
  • #1
park
5
0
Homework Statement
non-rotating black holes
Relevant Equations
Kruskal coordinates
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  • #2
242237


The right-hand side doesn't look dimensionally consistent to me. Could it be that the argument of the ##ln## function should be something like ##|r/r^* - 1|## instead of ##|r - r^*|##?

It's a bit hard to check your work since you haven't indicated how ##p## and ##q## are defined.
 
  • #3
oops! my mistake! p and q is defined ...
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  • #4
i finally got a clue with your comment about dimensions!
For consistency of dimension, i think r-r* of (8.13) should be r/r*-1
 
  • #5
park said:
i finally got a clue with your comment about dimensions!
For consistency of dimension, i think r-r* of (8.13) should be r/r*-1
Yes, things seem to work out better with the r/r*-1 form.

I'm not very familiar with Kruskal coordinates. Sean Carroll's notes on GR are freely available on the internet.
https://www.preposterousuniverse.com/grnotes/

He discusses Kruskal coordinates in this chapter:
https://preposterousuniverse.com/wp-content/uploads/grnotes-seven.pdf
The relevant material starts around page 182. Note equation (7.74) on page 186. I think his ##\tilde u## and ##\tilde v## are similar to your ##p## and ##q##, and his ##u'## and ##v'## are essentially your ##p'## and ##q'##. (But I believe Carroll is missing an overall negative sign in his expressions for ##v'## in (7.75) and (7.76). He corrects this in his published textbook.).
 

Related to Please give me some clues about the calculations for a non-rotating black hole

What is the formula for calculating the event horizon of a non-rotating black hole?

The formula for calculating the event horizon of a non-rotating black hole is given by: Rs = 2GM/c2, where Rs is the Schwarzschild radius, G is the gravitational constant, M is the mass of the black hole, and c is the speed of light.

How do you calculate the escape velocity of a non-rotating black hole?

The escape velocity of a non-rotating black hole can be calculated using the formula: ve = √(2GM/R), where ve is the escape velocity, G is the gravitational constant, M is the mass of the black hole, and R is the distance from the center of the black hole.

What is the equation for calculating the gravitational time dilation near a non-rotating black hole?

The equation for calculating the gravitational time dilation near a non-rotating black hole is given by: t0 = tf√(1-Rs/r), where t0 is the time measured by an observer at a distance r from the black hole, tf is the time measured by an observer at infinity, and Rs is the Schwarzschild radius.

How do you calculate the angular size of the shadow of a non-rotating black hole?

The angular size of the shadow of a non-rotating black hole can be calculated using the formula: θ = 2√(27/4)Rs/D, where θ is the angular size, Rs is the Schwarzschild radius, and D is the distance from the black hole to the observer.

What is the equation for calculating the gravitational redshift of light near a non-rotating black hole?

The equation for calculating the gravitational redshift of light near a non-rotating black hole is given by: z = √(1-Rs/r), where z is the redshift, Rs is the Schwarzschild radius, and r is the distance from the black hole to the observer.

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