Taylor Expansion of 1/(r-r'): Explained

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SUMMARY

The Taylor expansion of the function 1/(r - r') is derived using the 3D Taylor expansion formula, specifically applied to the function φ(r + a) = 1/|r - r'|. The resulting series expansion includes terms such as 1/r, (r'·r)/r^3, and (3(r·r')^2 - r^2r'^2)/2r^5, demonstrating how the function behaves around the point r. This expansion is crucial for simplifying calculations in fields such as physics and engineering where distance interactions are analyzed.

PREREQUISITES
  • Understanding of Taylor series and their applications in multivariable calculus.
  • Familiarity with vector notation and operations, particularly in three-dimensional space.
  • Knowledge of the concept of gradients and their role in Taylor expansions.
  • Basic principles of potential theory, especially in the context of physics.
NEXT STEPS
  • Study the derivation of Taylor series in multiple dimensions, focusing on vector functions.
  • Learn about the application of Taylor expansions in physics, particularly in potential fields.
  • Explore the implications of the expansion in computational simulations involving distance calculations.
  • Investigate the convergence properties of Taylor series and their limitations in various contexts.
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Students in mathematics and physics, researchers in computational modeling, and professionals working with potential theory and distance interactions in engineering applications.

captainjack2000
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Homework Statement


Could someone please explain how the taylor expansion of 1/(r-r') turns into
( 1/r+(r'.r)/r^3 + (3(r.r')^2-r^2r'^2)/2r^5 +...)


Homework Equations





The Attempt at a Solution

 
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i think it should be [itex]\frac{1}{|\vec{r}-\vec{r'}|}[/itex] yes?

use the 3d taylor expansion formula

[itex]\phi(\vec{r}+\vec{a})=\sum_{n=0}^{\infty} \frac{1}{n!} (\vec{a} \cdot \nabla)^n \phi(\vec{r})[/itex] with [itex]\phi(\vec{r}+\vec{a})=\frac{1}{|\vec{r}-\vec{r'}|}[/itex]
 

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