Verifying Equations 9.45 & 9.46 in Schutz, pg. 224

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SUMMARY

This discussion focuses on verifying equations 9.45 and 9.46 from Schutz's "A First Course in GR." The original equation 9.45 is identified as potentially incorrect, with the proposed correction being R = \frac{1}{2}l_{0}\Omega^{2}A/[(\omega_{0}{}^{2} - \Omega^{2})^2 + 4\Omega^{2}\gamma^{2}]^{1/2}. The justification for this correction is supported by analyzing equation 9.46, which relates to the tangent and cosine of the angle phi. Participants confirm that the corrected equation works effectively.

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This discussion is beneficial for students and educators in physics, particularly those studying general relativity, as well as researchers verifying mathematical models in theoretical physics.

Jimmy Snyder
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This question is just for those who have a copy of Schutz, A First Course in GR. I have tried to plug equations 9.43 and 9.44 into equation 9.42 in order to verify equations 9.45 and 9.46. So far, I have not been successful. However, I have come to the conclusion that probably 9.45 is incorrect. The book has:
[tex] R = \frac{1}{2}l_{0}\Omega^{2}A/[(\omega_{0} - \Omega)^2 + 4\Omega^{2}\gamma^{2}]^{1/2}[/tex]
But I believe it should be the following:
[tex] R = \frac{1}{2}l_{0}\Omega^{2}A/[(\omega_{0}{}^{2} - \Omega^{2})^2 + 4\Omega^{2}\gamma^{2}]^{1/2}[/tex]
Unfortunately, I haven't been able to successfully justify either equation. The reason I think that my version may be the correct one is by looking at equation 9.46
[tex] tan \phi = 2\gamma \Omega / (\omega_{0}{}^{2} - \Omega^{2})[/tex]
which implies:
[tex] cos \phi = (\omega_{0}{}^{2} - \Omega^{2}) / [(\omega_{0}{}^{2} - \Omega^{2})^2 + 4\Omega^{2}\gamma^{2}]^{1/2}[/tex]
 
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jimmysnyder said:
This question is just for those who have a copy of Schutz, A First Course in GR. I have tried to plug equations 9.43 and 9.44 into equation 9.42 in order to verify equations 9.45 and 9.46. So far, I have not been successful. However, I have come to the conclusion that probably 9.45 is incorrect. The book has:
[tex] R = \frac{1}{2}l_{0}\Omega^{2}A/[(\omega_{0} - \Omega)^2 + 4\Omega^{2}\gamma^{2}]^{1/2}[/tex]
But I believe it should be the following:
[tex] R = \frac{1}{2}l_{0}\Omega^{2}A/[(\omega_{0}{}^{2} - \Omega^{2})^2 + 4\Omega^{2}\gamma^{2}]^{1/2}[/tex]
Unfortunately, I haven't been able to successfully justify either equation. The reason I think that my version may be the correct one is by looking at equation 9.46
[tex] tan \phi = 2\gamma \Omega / (\omega_{0}{}^{2} - \Omega^{2})[/tex]
which implies:
[tex] cos \phi = (\omega_{0}{}^{2} - \Omega^{2}) / [(\omega_{0}{}^{2} - \Omega^{2})^2 + 4\Omega^{2}\gamma^{2}]^{1/2}[/tex]
Yes I get it to work out with your correction
[tex] R = \frac{1}{2}l_{0}\Omega^{2}A/[(\omega_{0}{}^{2} - \Omega^{2})^2 + 4\Omega^{2}\gamma^{2}]^{1/2}[/tex]
and the additional correction that
[tex] tan \phi = -2\gamma \Omega / (\omega_{0}{}^{2} - \Omega^{2})[/tex]
 
mitchellmckain said:
and the additional correction that
[tex] tan \phi = -2\gamma \Omega / (\omega_{0}{}^{2} - \Omega^{2})[/tex]
Thank you, thank you, thank you, thank you. I have spent hours on this one equation trying many different tricks, but somehow this one escaped me.
 

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