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

In summary, the discussion is about an ordinary differential equation with the form y''(x)+V(x)y(x)+const y(x)=0, which has a limit of zero as x approaches positive or negative infinity. The question is whether, if a point x0 exists where y(x0)=y'(x0)=0, the function y(x) will be equal to zero everywhere. The answer is no, as demonstrated by the example y(x) = tanh(x)^2(1-tanh(x)^2), with a divergent V(x) at x=0.
  • #1
LagrangeEuler
717
20
For ordinary differential equation
[tex]y''(x)+V(x)y(x)+const y(x)=0[/tex]
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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  • #2
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.)
 
  • #3
Yes ##\lim_{x \to \pm \infty}y(x)=0##. Interesting example. Look here

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

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

What are derivatives of functions in ODE?

Derivatives of functions in ODE (Ordinary Differential Equations) represent the rate of change of a function with respect to its independent variable. They are used to model how a system evolves over time.

How are derivatives of functions in ODE calculated?

Derivatives of functions in ODE can be calculated using various methods, including the power rule, product rule, quotient rule, and chain rule. These rules involve taking the derivative of each term in the function and combining them using mathematical operations.

What is the significance of derivatives of functions in ODE?

Derivatives of functions in ODE have many applications in science and engineering, such as modeling the behavior of physical systems, predicting future values, and optimizing processes. They also help in understanding the relationship between different variables in a system.

Can derivatives of functions in ODE be negative?

Yes, derivatives of functions in ODE can be negative. A negative derivative indicates that the function is decreasing at a certain point or that the rate of change is decreasing. This can have implications in real-world scenarios, such as predicting the decay of a substance or the decrease in temperature over time.

Are there any limitations to using derivatives of functions in ODE?

While derivatives of functions in ODE have many useful applications, they do have some limitations. They may not accurately model every system, and there may be cases where the function is not differentiable. Additionally, the accuracy of the derivatives can be affected by errors in data or simplifications in the model.

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