Wronskian and Linear Independence of y1 = t2 and y2 = t|t| in Second Order ODEs

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SUMMARY

The discussion centers on the Wronskian of the functions y1 = t² and y2 = t|t|, which is zero for all t in the interval [-1, 1]. Despite this, the functions are not linearly dependent, as neither is a scalar multiple of the other. This indicates that the Wronskian alone does not conclusively determine linear independence in all contexts, particularly for second-order ordinary differential equations (ODEs). Stronger conditions, such as analyticity, are often required to ensure the Wronskian serves as a sufficient test for linear independence.

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  • Understanding of Wronskian determinants in linear algebra
  • Familiarity with second-order ordinary differential equations (ODEs)
  • Knowledge of linear independence and dependence of functions
  • Concept of analytic functions and their properties
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Mathematicians, students of differential equations, and anyone studying linear algebra and its applications in ODEs will benefit from this discussion.

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For y1 = t2 and y2 = t|t| (y2'' is not defined at t = 0), the Wronskian is 0 for all t over the interval [-1,1]. However, the two functions are not linearly dependent over this interval in the sense that one is not a unique multiple of the other. Does this imply that the Wronskian tells linear independence only in a particular space that is specific to the solution set, in which the solution set to a second order ODE would be a 2-space?
 
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The Wronskian is not a conclusive test. That is when the Wronskian is identically zero we draw no conclusion. Often we impose stonger conditionns on the functions (like being analytic or normal solutions of a differential equation) so that the test becomes sufficient.
 
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