Is y(x) Identically Zero in This ODE Given Specific Initial Conditions?

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Discussion Overview

The discussion revolves around the ordinary differential equation (ODE) given by y''(x) + V(x)y(x) + const y(x) = 0, specifically examining whether the function y(x) must be identically zero everywhere if it satisfies certain initial conditions at a point x_0, namely y(x_0) = 0 and y'(x_0) = 0. The scope includes theoretical exploration of ODEs and the implications of initial conditions on solutions.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions if y(x) must be zero everywhere given the initial conditions at x_0.
  • Another participant suggests that y(x) does not have to be zero everywhere, providing an example function y(x) = tanh(x)²(1 - tanh(x)²) that satisfies the limit condition as x approaches infinity.
  • A third participant confirms the limit condition and references a specific time segment from a video for further exploration of the topic.
  • Another participant notes that the function V(x) in the provided example diverges at zero, yet the product V(x)y(x) still exists.

Areas of Agreement / Disagreement

Participants do not reach a consensus; there are competing views regarding whether y(x) must be identically zero, with at least one example provided that suggests it need not be.

Contextual Notes

The discussion includes assumptions about the behavior of V(x) and the implications of the initial conditions, but these aspects remain unresolved and depend on further clarification of V(x).

LagrangeEuler
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For ordinary differential equation
y''(x)+V(x)y(x)+const y(x)=0
for which ##\lim_{x \to \pm \infty}=0## if we have that in some point ##x_0## the following statement is true
##y(x_0)=y'(x_0)=0## is then function ##y(x)=0## everywhere?
 
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I suppose you mean ## \lim_{x=\pm \infty} y(x) = 0 ##? And no the function doesn't have to be ## 0 ## everywhere. An example is ## y(x) = \tanh(x)^{2}(1-\tanh(x)^{2}) ##. (You will have to work out ## V(x) ## yourself.)
 
Yes ##\lim_{x \to \pm \infty}y(x)=0##. Interesting example. Look here

from 2:46 - 4:09.
 
Well ## V(x) ## in the above solution is divergent in ## 0 ##. The product of ## V(x)y(x) ## still exists.
 

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