How can the stability of this numerical method be proven?

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Discussion Overview

The discussion focuses on proving the stability of a specific numerical method related to the differential equation \( u'(t) = u^2 \). Participants are attempting to analyze the method's formulation and its implications for stability, with a particular emphasis on the mathematical expressions involved.

Discussion Character

  • Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant presents a numerical method expressed as \( \frac{u^{n+1} - u^{n}}{\vartriangle t} = (u^{n+1}u^n) \) and seeks assistance in proving its stability.
  • Another participant expresses confusion regarding the notation used in the initial equation, questioning its clarity and meaning.
  • A participant clarifies that the right side of the equation represents the product of iterations, specifically \( (u^{n+1})(u^n) \).
  • Concerns are raised about the dimensional correctness of the initial equation, with one participant stating that it appears to be dimensionally wrong.
  • There is a lack of consensus on the interpretation of the notation, with multiple participants expressing uncertainty about the meaning of specific terms.

Areas of Agreement / Disagreement

Participants do not appear to agree on the clarity and correctness of the notation used in the proposed numerical method. Multiple competing interpretations of the expressions exist, and the discussion remains unresolved regarding the stability proof.

Contextual Notes

Limitations include unclear notation and potential dimensional inconsistencies in the presented equations, which may affect the analysis of stability.

juaninf
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Please anyone help me with stability proof this next numerical method \dfrac{u^{n+1} - u^{n}}{\vartriangle t} = (u^{n+1}u^n)I am trying make :

<br /> \begin{equation*}<br /> \begin{split}<br /> u_2^{n+1} - u_1^{n+1} &amp; = \displaystyle\frac{u_2^{n}}{1-\vartriangle tu_2^{n}} - \displaystyle\frac{u_1^{n}}{1-\vartriangle tu_1^{n}} \\<br /> &amp; = \displaystyle\frac{u_2^{n}-u_1^{n}}{(1-\vartriangle tu_1^{n})(1-\vartriangle tu_2^{n})}\\<br /> &amp; \geq{\displaystyle\frac{u_2^{n}-u_1^{n}}{e^{-\vartriangle t(u_2^{n}+u_1^{n})}}}\\<br /> \end{split}<br /> \end{equation*}<br />

but I not have more idea :( please help me
 
Last edited:
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Your notation is confusing. I don't know what the right side of your first equation is supposed to mean.
 
product <br /> \dfrac{u^{n+1} - u^{n}}{\vartriangle t} = (u^{n+1}u^n)<br /> this numerical method is from u&#039;(t)=u^2
 
I don't know what (un+1un) is supposed to mean!
 
is product of iterations (u^{n+1})*(u^n)
 
Last edited:
On the face of it the first equation doesn't make any sense. Dimensionally, it looks completely wrong.
 

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