QM- Why is the separation constant +/-l(l+1) ?

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SUMMARY

The discussion centers on the separation constant in quantum mechanics, specifically in Griffith's "Introduction to Quantum Mechanics" (3rd Edition). The separation constant, denoted as +/-l(l+1), changes sign due to the requirement that the terms in the associated equations sum to zero. This is illustrated in equations 4.16 and 4.17, where the relationship between the constants is essential for maintaining the integrity of the mathematical framework. Understanding this concept is crucial for grasping the implications of separation of variables in quantum mechanics.

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jinksys
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This isn't a HW problem, it's more of a general question. I'm reading Griffith's Intro to QM 3rd Edition. On page 134 he uses separation of variables, of which I'm familiar (but by no means an expert). Could someone explain why the separation constant in equations 4.16 and 4.17 changes sign?

The equations in question : http://imgur.com/8OKqz"
 
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If you look at the equation above those two, you see the terms sum to 0, so if one is positive, the other one is negative.
 
vela said:
If you look at the equation above those two, you see the terms sum to 0, so if one is positive, the other one is negative.

Jeez, that should have been obvious!
Thanks for your help.
 

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