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29 Lamé FunctionsLamé Functions

§29.6 Fourier Series

Contents

§29.6(i) Function \mathop{\mathit{Ec}^{{2m}}_{{\nu}}\/}\nolimits\!\left(z,k^{2}\right)

When \nu\neq 2n, where n is a nonnegative integer, it follows from §2.9(i) that for any value of H the system (29.6.4)–(29.6.6) has a unique recessive solution A_{0},A_{2},A_{4},\dots; furthermore

In addition, if H satisfies (29.6.2), then (29.6.3) applies.

In the special case \nu=2n, m=0,1,\dots,n, there is a unique nontrivial solution with the property A_{{2p}}=0, p=n+1,n+2,\dots. This solution can be constructed from (29.6.4) by backward recursion, starting with A_{{2n+2}}=0 and an arbitrary nonzero value of A_{{2n}}, followed by normalization via (29.6.5) and (29.6.6). Consequently, \mathop{\mathit{Ec}^{{2m}}_{{\nu}}\/}\nolimits\!\left(z,k^{2}\right) reduces to a Lamé polynomial; compare §§29.12(i) and 29.15(i).

An alternative version of the Fourier series expansion (29.6.1) is given by

Here \mathop{\mathrm{dn}\/}\nolimits\left(z,k\right) is as in §22.2, and

29.6.9(\beta_{0}-H)C_{0}+\alpha_{0}C_{2}=0,
29.6.10\gamma_{p}C_{{2p-2}}+(\beta_{p}-H)C_{{2p}}+\alpha_{p}C_{{2p+2}}=0,p\geq 1,

with \alpha_{p},\beta_{p}, and \gamma_{p} now defined by

29.6.11
\alpha_{p}=\begin{cases}\nu(\nu+1)k^{2},&p=0,\\
\frac{1}{2}(\nu-2p)(\nu+2p+1)k^{2},&p\geq 1,\end{cases}
\beta_{p}=4p^{2}(2-k^{2}),
\gamma_{p}=\tfrac{1}{2}(\nu-2p+1)(\nu+2p)k^{2},

and

29.6.13\tfrac{1}{2}C_{0}+\sum_{{p=1}}^{{\infty}}C_{{2p}}>0,

§29.6(ii) Function \mathop{\mathit{Ec}^{{2m+1}}_{{\nu}}\/}\nolimits\!\left(z,k^{2}\right)

Also,

where

29.6.24(\beta_{0}-H)C_{1}+\alpha_{0}C_{3}=0,
29.6.25\gamma_{p}C_{{2p-1}}+(\beta_{p}-H)C_{{2p+1}}+\alpha_{p}C_{{2p+3}}=0,p\geq 1,

with

29.6.26
\alpha_{p}=\tfrac{1}{2}(\nu-2p-1)(\nu+2p+2)k^{2},
\beta_{p}=\begin{cases}2-k^{2}+\frac{1}{2}\nu(\nu+1)k^{2},&p=0,\\
(2p+1)^{2}(2-k^{2}),&p\geq 1,\end{cases}
\gamma_{p}=\tfrac{1}{2}(\nu-2p)(\nu+2p+1)k^{2},

and

29.6.28\sum_{{p=0}}^{{\infty}}C_{{2p+1}}>0,

§29.6(iii) Function \mathop{\mathit{Es}^{{2m+1}}_{{\nu}}\/}\nolimits\!\left(z,k^{2}\right)

Also,

where

29.6.39(\beta_{0}-H)D_{1}+\alpha_{0}D_{3}=0,
29.6.40\gamma_{p}D_{{2p-1}}+(\beta_{p}-H)D_{{2p+1}}+\alpha_{p}D_{{2p+3}}=0,p\geq 1,

with

29.6.41
\alpha_{p}=\tfrac{1}{2}(\nu-2p-1)(\nu+2p+2)k^{2},
\beta_{p}=\begin{cases}2-k^{2}-\frac{1}{2}\nu(\nu+1)k^{2},&p=0,\\
(2p+1)^{2}(2-k^{2}),&p\geq 1,\end{cases}
\gamma_{p}=\tfrac{1}{2}(\nu-2p)(\nu+2p+1)k^{2},

and

29.6.43\sum_{{p=0}}^{{\infty}}(2p+1)D_{{2p+1}}>0,

§29.6(iv) Function \mathop{\mathit{Es}^{{2m+2}}_{{\nu}}\/}\nolimits\!\left(z,k^{2}\right)

Also,

where

29.6.54(\beta_{0}-H)D_{2}+\alpha_{0}D_{4}=0,
29.6.55\gamma_{p}D_{{2p}}+(\beta_{p}-H)D_{{2p+2}}+\alpha_{p}D_{{2p+4}}=0,p\geq 1,

with

29.6.56
\alpha_{p}=\tfrac{1}{2}(\nu-2p-2)(\nu+2p+3)k^{2},
\beta_{p}=(2p+2)^{2}(2-k^{2}),
\gamma_{p}=\tfrac{1}{2}(\nu-2p-1)(\nu+2p+2)k^{2},

and

29.6.58\sum_{{p=0}}^{{\infty}}(2p+2)D_{{2p+2}}>0,