How to reduce the integral equation for light deflection?

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SUMMARY

The discussion centers on the reduction of integral equations for light deflection as presented in Hartle's book (2003). Specifically, it examines the approximation of equation 9.80, represented as $$ΔΦ=\int_0^{w_1}\frac{(1+\frac{M}{b}w)}{(1+\frac{2M}{b}w-w^2)^\frac{1}{2}}dw$$, to equation 9.81, $$ΔΦ≈\pi+4M/b$$. The participants seek clarification on expressing the variable $$w_1$$ in terms of $$m$$ and $$B$$ to validate the approximation. The discussion emphasizes the need for a detailed explanation of the steps involved in this mathematical reduction.

PREREQUISITES
  • Understanding of integral calculus, particularly definite integrals.
  • Familiarity with the concepts of light deflection in general relativity.
  • Knowledge of the variables $$M$$, $$b$$, and their physical significance.
  • Access to Hartle's book, "Gravity: An Introduction to Einstein's General Relativity" (2003).
NEXT STEPS
  • Research the derivation of light deflection equations in general relativity.
  • Study the mathematical techniques for approximating definite integrals.
  • Explore the significance of the variables $$M$$ and $$b$$ in gravitational contexts.
  • Review additional literature on integral equations and their applications in physics.
USEFUL FOR

This discussion is beneficial for physicists, mathematicians, and students studying general relativity, particularly those interested in the mathematical foundations of light deflection phenomena.

Bishal Banjara
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1. At pg.212, Hartle book (2003) writes equation 9.81 as an approximation of 9.80, directly. 2. $$ΔΦ=\int_0^{w_1}\frac{(1+\frac{M}{b}w)}{(1+\frac{2M}{b}w-w^2)^\frac{1}{2}}dw$$ equation(9.80)
$$ΔΦ≈\pi+4M/b$$ equation(9.81)
3. I am expecting anyone to give me a well-explained reference particularly with this method or clarify me without scaping proper steps.
 
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Unless you can express w1 as w1(m,B) I don't think the definite integral can be approximated as shown.
 
$$w$$ is defined as $$b/r$$. You could see the book. Otherwise, I will write a few steps back.
 

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