Difference between revisions of "Associated Laguerre L"

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Let $\alpha \in \mathbb{R}$. The associated Laguerre polynomials, $L_n^{(\alpha)}(x)$ are solutions of the differential equation
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__NOTOC__
$$x\dfrac{d^2y}{dx^2} + (1-x)\dfrac{dy}{dx} + ny=0.$$
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Let $\lambda \in \mathbb{R}$. The associated Laguerre polynomials, $L_n^{(\lambda)}(x)$ are solutions of the differential equation
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$$x\dfrac{d^2y}{dx^2} + (\lambda+1-x)\dfrac{dy}{dx} + ny=0.$$
  
 
The first few Laguerre polynomials are given by
 
The first few Laguerre polynomials are given by
 
$$\begin{array}{ll}
 
$$\begin{array}{ll}
L_0^{(\alpha)}(x) &= 1 \\
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L_0^{(\lambda)}(x) &= 1 \\
L_1^{(\alpha)}(x) &= -x+\alpha+1 \\
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L_1^{(\lambda)}(x) &= -x+\lambda+1 \\
L_2^{(\alpha)}(x) &= \dfrac{x^2}{2} -(\alpha+2)x+\dfrac{(\alpha+2)(\alpha+1)}{2} \\
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L_2^{(\lambda)}(x) &= \dfrac{x^2}{2} -(\lambda+2)x+\dfrac{(\lambda+2)(\lambda+1)}{2} \\
L_3^{(\alpha)}(x) &= -\dfrac{x^3}{6} + \dfrac{(\alpha+3)x^2}{2} - \dfrac{(\alpha+2)(\alpha+3)x}{2} + \dfrac{(\alpha+1)(\alpha+2)(\alpha+3)}{6} \\
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L_3^{(\lambda)}(x) &= -\dfrac{x^3}{6} + \dfrac{(\lambda+3)x^2}{2} - \dfrac{(\lambda+2)(\lambda+3)x}{2} + \dfrac{(\lambda+1)(\lambda+2)(\lambda+3)}{6} \\
 
\vdots
 
\vdots
 
\end{array}$$
 
\end{array}$$
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<div align="center">
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<gallery>
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File:Associatedlaguerrealpha=1.png|Graph of $L_n^{(1)}$ on $[-2,10]$.
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</gallery>
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</div>
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=Properties=
 
=Properties=
<div class="toccolours mw-collapsible mw-collapsed" style="width:800px">
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<strong>Theorem:</strong> The following formula holds:
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=See also=
$$L_n^{(\alpha)}(x) = \displaystyle\sum_{k=0}^n (-1)^k {n+\alpha \choose n-k} \dfrac{x^k}{k!}.$$
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[[Laguerre L]]<br />
<div class="mw-collapsible-content">
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<strong>Proof:</strong> █
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=References=
</div>
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</div>
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{{:Orthogonal polynomials footer}}
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[[Category:SpecialFunction]]

Latest revision as of 13:38, 15 March 2018

Let $\lambda \in \mathbb{R}$. The associated Laguerre polynomials, $L_n^{(\lambda)}(x)$ are solutions of the differential equation $$x\dfrac{d^2y}{dx^2} + (\lambda+1-x)\dfrac{dy}{dx} + ny=0.$$

The first few Laguerre polynomials are given by $$\begin{array}{ll} L_0^{(\lambda)}(x) &= 1 \\ L_1^{(\lambda)}(x) &= -x+\lambda+1 \\ L_2^{(\lambda)}(x) &= \dfrac{x^2}{2} -(\lambda+2)x+\dfrac{(\lambda+2)(\lambda+1)}{2} \\ L_3^{(\lambda)}(x) &= -\dfrac{x^3}{6} + \dfrac{(\lambda+3)x^2}{2} - \dfrac{(\lambda+2)(\lambda+3)x}{2} + \dfrac{(\lambda+1)(\lambda+2)(\lambda+3)}{6} \\ \vdots \end{array}$$

Properties

See also

Laguerre L

References

Orthogonal polynomials