Difference between revisions of "Jacobi P"
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<strong>Theorem:</strong> ([[Rodrigues' formula]]) The following formula holds: | <strong>Theorem:</strong> ([[Rodrigues' formula]]) The following formula holds: | ||
$$P_n^{(\alpha,\beta)}(z)=\dfrac{(-1)^n}{2^nn!} (1-z)^{-\alpha}(1+z)^{-\beta} \dfrac{d^n}{dz^n} \left[(1-z)^{\alpha}(1+z)^{\beta}(1-z^2)^n \right].$$ | $$P_n^{(\alpha,\beta)}(z)=\dfrac{(-1)^n}{2^nn!} (1-z)^{-\alpha}(1+z)^{-\beta} \dfrac{d^n}{dz^n} \left[(1-z)^{\alpha}(1+z)^{\beta}(1-z^2)^n \right].$$ | ||
| + | <div class="mw-collapsible-content"> | ||
| + | <strong>Proof:</strong> █ | ||
| + | </div> | ||
| + | </div> | ||
| + | |||
| + | <div class="toccolours mw-collapsible mw-collapsed"> | ||
| + | <strong>Theorem:</strong> (Orthogonality) The following formula holds: | ||
| + | $$\displaystyle\int_{-1}^1 (-1-x)^{\alpha}(1+x)^{\beta}P_n^{(\alpha,\beta)}(x)P_m^{(\alpha,\beta)}(x)dx=\dfrac{2^{\alpha+\beta+1}\Gamma(n+\alpha+1)\Gamma(n+\beta+1)}{(2n+\alpha+\beta+1)n! \Gamma(n+\alpha+\beta+1)}\delta_{mn},$$ | ||
| + | where $\delta_{mn}$ denotes the [[Dirac delta]]. | ||
| + | <div class="mw-collapsible-content"> | ||
| + | <strong>Proof:</strong> █ | ||
| + | </div> | ||
| + | </div> | ||
| + | |||
| + | <div class="toccolours mw-collapsible mw-collapsed"> | ||
| + | <strong>Theorem:</strong> The $P_n^{(\alpha,\beta)}$ functions satisfy the differential equation | ||
| + | $$(1-x^2)\dfrac{d^2y}{dx^2}+(\beta-\alpha-(\alpha+\beta+2)x)\dfrac{dy}{dx}+n(n+\alpha+\beta+1)y=0.$$ | ||
<div class="mw-collapsible-content"> | <div class="mw-collapsible-content"> | ||
<strong>Proof:</strong> █ | <strong>Proof:</strong> █ | ||
Revision as of 06:49, 10 June 2015
The Jacobi polynomial $P_n^{(\alpha,\beta)}$ are defined by $$P_n^{(\alpha,\beta)}(z)=\dfrac{(\alpha+1)^{\overline{n}}}{n!} {}_2F_1 \left(-n, 1+\alpha+\beta+n;\alpha+1; \dfrac{1}{2}(1-z) \right),$$ where ${}_2F_1$ is the generalized hypergeometries series.
Properties
Theorem: (Rodrigues' formula) The following formula holds: $$P_n^{(\alpha,\beta)}(z)=\dfrac{(-1)^n}{2^nn!} (1-z)^{-\alpha}(1+z)^{-\beta} \dfrac{d^n}{dz^n} \left[(1-z)^{\alpha}(1+z)^{\beta}(1-z^2)^n \right].$$
Proof: █
Theorem: (Orthogonality) The following formula holds: $$\displaystyle\int_{-1}^1 (-1-x)^{\alpha}(1+x)^{\beta}P_n^{(\alpha,\beta)}(x)P_m^{(\alpha,\beta)}(x)dx=\dfrac{2^{\alpha+\beta+1}\Gamma(n+\alpha+1)\Gamma(n+\beta+1)}{(2n+\alpha+\beta+1)n! \Gamma(n+\alpha+\beta+1)}\delta_{mn},$$ where $\delta_{mn}$ denotes the Dirac delta.
Proof: █
Theorem: The $P_n^{(\alpha,\beta)}$ functions satisfy the differential equation $$(1-x^2)\dfrac{d^2y}{dx^2}+(\beta-\alpha-(\alpha+\beta+2)x)\dfrac{dy}{dx}+n(n+\alpha+\beta+1)y=0.$$
Proof: █
