Sturm - Liouville Parseval proof












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Consider the expansion $𝑓(𝑥)=sum_{n=0}^{infty}A_𝑛phi_𝑛(𝑥)$
where $phi_𝑛(𝑥)$ is the set of eigenfunctions of the Sturm-Liouville problem, and $𝑓(𝑥)$ is any piecewise differentiable function on the interval $(𝑎,𝑏)$. Show that $int_{a}^{b}[𝑓(𝑥)]^2𝑤(𝑥)𝑑𝑥=sum_{n=0}^{infty}𝐴_𝑛^2𝑁_𝑛$
where $w(x)$ is weight function and $𝑁_𝑛$ is the normalization integrals of the eigenfunctions $phi_𝑛(𝑥)$. $(𝑁𝑛=〈phi_𝑛(𝑥),phi_𝑛(𝑥)〉)$










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  • $begingroup$
    The simplest case would be a regular problem on a finite interval $[a,b]$. In that case, the eigenfunctions form a complete orthogonal basis of $L^2_w[a,b]$, which is equivalent to the Parseval relation you state. However, the proof would be too long for a post in this forum, even for the simplest case of $sin$ and $cos$ functions.
    $endgroup$
    – DisintegratingByParts
    Jan 9 at 6:44
















0












$begingroup$


Consider the expansion $𝑓(𝑥)=sum_{n=0}^{infty}A_𝑛phi_𝑛(𝑥)$
where $phi_𝑛(𝑥)$ is the set of eigenfunctions of the Sturm-Liouville problem, and $𝑓(𝑥)$ is any piecewise differentiable function on the interval $(𝑎,𝑏)$. Show that $int_{a}^{b}[𝑓(𝑥)]^2𝑤(𝑥)𝑑𝑥=sum_{n=0}^{infty}𝐴_𝑛^2𝑁_𝑛$
where $w(x)$ is weight function and $𝑁_𝑛$ is the normalization integrals of the eigenfunctions $phi_𝑛(𝑥)$. $(𝑁𝑛=〈phi_𝑛(𝑥),phi_𝑛(𝑥)〉)$










share|cite|improve this question









$endgroup$












  • $begingroup$
    The simplest case would be a regular problem on a finite interval $[a,b]$. In that case, the eigenfunctions form a complete orthogonal basis of $L^2_w[a,b]$, which is equivalent to the Parseval relation you state. However, the proof would be too long for a post in this forum, even for the simplest case of $sin$ and $cos$ functions.
    $endgroup$
    – DisintegratingByParts
    Jan 9 at 6:44














0












0








0





$begingroup$


Consider the expansion $𝑓(𝑥)=sum_{n=0}^{infty}A_𝑛phi_𝑛(𝑥)$
where $phi_𝑛(𝑥)$ is the set of eigenfunctions of the Sturm-Liouville problem, and $𝑓(𝑥)$ is any piecewise differentiable function on the interval $(𝑎,𝑏)$. Show that $int_{a}^{b}[𝑓(𝑥)]^2𝑤(𝑥)𝑑𝑥=sum_{n=0}^{infty}𝐴_𝑛^2𝑁_𝑛$
where $w(x)$ is weight function and $𝑁_𝑛$ is the normalization integrals of the eigenfunctions $phi_𝑛(𝑥)$. $(𝑁𝑛=〈phi_𝑛(𝑥),phi_𝑛(𝑥)〉)$










share|cite|improve this question









$endgroup$




Consider the expansion $𝑓(𝑥)=sum_{n=0}^{infty}A_𝑛phi_𝑛(𝑥)$
where $phi_𝑛(𝑥)$ is the set of eigenfunctions of the Sturm-Liouville problem, and $𝑓(𝑥)$ is any piecewise differentiable function on the interval $(𝑎,𝑏)$. Show that $int_{a}^{b}[𝑓(𝑥)]^2𝑤(𝑥)𝑑𝑥=sum_{n=0}^{infty}𝐴_𝑛^2𝑁_𝑛$
where $w(x)$ is weight function and $𝑁_𝑛$ is the normalization integrals of the eigenfunctions $phi_𝑛(𝑥)$. $(𝑁𝑛=〈phi_𝑛(𝑥),phi_𝑛(𝑥)〉)$







sturm-liouville parsevals-identity






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asked Jan 8 at 23:15









SquanchSquanch

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  • $begingroup$
    The simplest case would be a regular problem on a finite interval $[a,b]$. In that case, the eigenfunctions form a complete orthogonal basis of $L^2_w[a,b]$, which is equivalent to the Parseval relation you state. However, the proof would be too long for a post in this forum, even for the simplest case of $sin$ and $cos$ functions.
    $endgroup$
    – DisintegratingByParts
    Jan 9 at 6:44


















  • $begingroup$
    The simplest case would be a regular problem on a finite interval $[a,b]$. In that case, the eigenfunctions form a complete orthogonal basis of $L^2_w[a,b]$, which is equivalent to the Parseval relation you state. However, the proof would be too long for a post in this forum, even for the simplest case of $sin$ and $cos$ functions.
    $endgroup$
    – DisintegratingByParts
    Jan 9 at 6:44
















$begingroup$
The simplest case would be a regular problem on a finite interval $[a,b]$. In that case, the eigenfunctions form a complete orthogonal basis of $L^2_w[a,b]$, which is equivalent to the Parseval relation you state. However, the proof would be too long for a post in this forum, even for the simplest case of $sin$ and $cos$ functions.
$endgroup$
– DisintegratingByParts
Jan 9 at 6:44




$begingroup$
The simplest case would be a regular problem on a finite interval $[a,b]$. In that case, the eigenfunctions form a complete orthogonal basis of $L^2_w[a,b]$, which is equivalent to the Parseval relation you state. However, the proof would be too long for a post in this forum, even for the simplest case of $sin$ and $cos$ functions.
$endgroup$
– DisintegratingByParts
Jan 9 at 6:44










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