Is it possible to find complex numbers Cn, so that both equations are satisfied?

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Discussion Overview

The discussion revolves around the possibility of finding complex numbers \(C_n\) that satisfy two specific equations involving infinite series. The context includes theoretical exploration related to wave functions in quantum mechanics, particularly concerning the infinite potential well.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant questions whether it is possible to find complex numbers \(C_n\) such that \(\sum^{\infty}_{n=1}nC_n=0\) and \(\sum^{\infty}_{n=1}|C_n|^2=1\).
  • Another participant proposes specific values for \(C_1\) and \(C_2\), with \(C_{n>2}=0\), as a potential solution.
  • A subsequent post raises an additional question about finding constants that satisfy three conditions, including an alternating series term.
  • One participant expresses concern about whether they are assisting with homework and asks for the context of the exercises.
  • A participant clarifies that they are attempting to find a wave function for an infinite potential well, which requires satisfying the three equations mentioned.
  • Another participant asserts that there is a jump in the derivative for an infinite well.
  • A later reply suggests that for finite wells, the derivative must not jump.
  • Another proposed set of values for \(C_n\) is presented, with specific values for \(C_1\), \(C_2\), and \(C_3\), while stating that \(C_n=0\) for \(n>3\).

Areas of Agreement / Disagreement

Participants express differing views on the nature of the wave function and the behavior of derivatives in infinite versus finite potential wells. There is no consensus on the possibility of finding the required constants or the implications of the proposed solutions.

Contextual Notes

Some assumptions regarding the nature of the wave functions and the conditions for continuity of derivatives are not fully explored. The discussion also does not resolve the mathematical steps necessary to validate the proposed solutions.

LagrangeEuler
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Is it possible two find complex numbers ##C_n##, so that both equations are satisfied
\sum^{\infty}_{n=1}nC_n=0
and
\sum^{\infty}_{n=1}|C_n|^2=1?
 
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##C_1=2/\sqrt 5,\quad C_2 = -1/\sqrt 5,\quad C_{n>2}=0##
 
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Thanks a lot. One more question. Is it possible to find constants that satisfy three conditions
\sum^{\infty}_{n=1}|C_n|^2=1
\sum^{\infty}_{n=1}nC_n=0
\sum^{\infty}_{n=1}(-1)^nnC_n=0
 
Are we doing your homework for you ? What is the context of these exercises ?
 
No. I am trying to find wave function of infinite potential well which derivative does not have jump in the boundaries. To my mind this is only possible if we constants that satisfy those three equation. I do not have idea how to find them.
 
With an infinite well there is a jump in the derivative
 
BvU said:
With an infinite well there is a jump in the derivative
and for finite wells, the derivative must not jump right?
 
How about ##C_1=3/\sqrt{10}, C_2=0, C_3=-1/\sqrt{10}## and ##C_n=0## for ##n>3##?
 

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