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29 Lamé FunctionsLamé Functions

§29.6 Fourier Series

Contents
  1. §29.6(i) Function 𝐸𝑐ν2⁢m⁡(z,k2)
  2. §29.6(ii) Function 𝐸𝑐ν2⁢m+1⁡(z,k2)
  3. §29.6(iii) Function 𝐸𝑠ν2⁢m+1⁡(z,k2)
  4. §29.6(iv) Function 𝐸𝑠ν2⁢m+2⁡(z,k2)

§29.6(i) Function 𝐸𝑐ν2⁢m⁡(z,k2)

With ϕ=12⁢π−am⁡(z,k), as in (29.2.5), we have

29.6.1 𝐸𝑐ν2⁢m⁡(z,k2)=12⁢A0+∑p=1∞A2⁢p⁢cos⁡(2⁢p⁢ϕ).

Here

29.6.2 H=2⁢aν2⁢m⁡(k2)−ν⁢(ν+1)⁢k2,
29.6.3 (β0−H)⁢A0+α0⁢A2=0,
29.6.4 γp⁢A2⁢p−2+(βp−H)⁢A2⁢p+αp⁢A2⁢p+2=0,
p≥1,

with αp, βp, and γp as in (29.3.11) and (29.3.12), and

29.6.5 12⁢A02+∑p=1∞A2⁢p2=1,
29.6.6 12⁢A0+∑p=1∞A2⁢p>0.

When ν≠2⁢n, 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 A0,A2,A4,…; furthermore

29.6.7 limp→∞A2⁢p+2A2⁢p=k2(1+k′)2,
ν≠2⁢n, or ν=2⁢n and m>n.

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

In the special case ν=2⁢n, m=0,1,…,n, there is a unique nontrivial solution with the property A2⁢p=0, p=n+1,n+2,…. This solution can be constructed from (29.6.4) by backward recursion, starting with A2⁢n+2=0 and an arbitrary nonzero value of A2⁢n, followed by normalization via (29.6.5) and (29.6.6). Consequently, 𝐸𝑐ν2⁢m⁡(z,k2) 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

29.6.8 𝐸𝑐ν2⁢m⁡(z,k2)=dn⁡(z,k)⁢(12⁢C0+∑p=1∞C2⁢p⁢cos⁡(2⁢p⁢ϕ)).

Here dn⁡(z,k) is as in §22.2, and

29.6.9 (β0−H)⁢C0+α0⁢C2=0,
29.6.10 γp⁢C2⁢p−2+(βp−H)⁢C2⁢p+αp⁢C2⁢p+2=0,
p≥1,

with αp,βp, and γp now defined by

29.6.11 αp ={ν⁢(ν+1)⁢k2,p=0,12⁢(ν−2⁢p)⁢(ν+2⁢p+1)⁢k2,p≥1,
βp =4⁢p2⁢(2−k2),
γp =12⁢(ν−2⁢p+1)⁢(ν+2⁢p)⁢k2,

and

29.6.12 (1−12⁢k2)⁢(12⁢C02+∑p=1∞C2⁢p2)−12⁢k2⁢∑p=0∞C2⁢p⁢C2⁢p+2=1,
29.6.13 12⁢C0+∑p=1∞C2⁢p>0,
29.6.14 limp→∞C2⁢p+2C2⁢p=k2(1+k′)2,
ν≠2⁢n+1, or ν=2⁢n+1 and m>n,

§29.6(ii) Function 𝐸𝑐ν2⁢m+1⁡(z,k2)

29.6.16 𝐸𝑐ν2⁢m+1⁡(z,k2)=∑p=0∞A2⁢p+1⁢cos⁡((2⁢p+1)⁢ϕ).

Here

29.6.17 H=2⁢aν2⁢m+1⁡(k2)−ν⁢(ν+1)⁢k2,
29.6.18 (β0−H)⁢A1+α0⁢A3=0,
29.6.19 γp⁢A2⁢p−1+(βp−H)⁢A2⁢p+1+αp⁢A2⁢p+3=0,
p≥1,

with αp, βp, and γp as in (29.3.13) and (29.3.14), and

29.6.20 ∑p=0∞A2⁢p+12=1,
29.6.21 ∑p=0∞A2⁢p+1>0,
29.6.22 limp→∞A2⁢p+1A2⁢p−1=k2(1+k′)2,
ν≠2⁢n+1, or ν=2⁢n+1 and m>n.

Also,

29.6.23 𝐸𝑐ν2⁢m+1⁡(z,k2)=dn⁡(z,k)⁢∑p=0∞C2⁢p+1⁢cos⁡((2⁢p+1)⁢ϕ),

where

29.6.24 (β0−H)⁢C1+α0⁢C3=0,
29.6.25 γp⁢C2⁢p−1+(βp−H)⁢C2⁢p+1+αp⁢C2⁢p+3=0,
p≥1,

with

29.6.26 αp =12⁢(ν−2⁢p−1)⁢(ν+2⁢p+2)⁢k2,
βp ={2−k2+12⁢ν⁢(ν+1)⁢k2,p=0,(2⁢p+1)2⁢(2−k2),p≥1,
γp =12⁢(ν−2⁢p)⁢(ν+2⁢p+1)⁢k2,

and

29.6.27 (1−12⁢k2)⁢∑p=0∞C2⁢p+12−12⁢k2⁢(12⁢C12+∑p=0∞C2⁢p+1⁢C2⁢p+3)=1,
29.6.28 ∑p=0∞C2⁢p+1>0,
29.6.29 limp→∞C2⁢p+1C2⁢p−1=k2(1+k′)2,
ν≠2⁢n+2, or ν=2⁢n+2 and m>n,

§29.6(iii) Function 𝐸𝑠ν2⁢m+1⁡(z,k2)

29.6.31 𝐸𝑠ν2⁢m+1⁡(z,k2)=∑p=0∞B2⁢p+1⁢sin⁡((2⁢p+1)⁢ϕ).

Here

29.6.32 H=2⁢bν2⁢m+1⁡(k2)−ν⁢(ν+1)⁢k2,
29.6.33 (β0−H)⁢B1+α0⁢B3=0,
29.6.34 γp⁢B2⁢p−1+(βp−H)⁢B2⁢p+1+αp⁢B2⁢p+3=0,
p≥1,

with αp, βp, and γp as in (29.3.15), (29.3.16), and

29.6.35 ∑p=0∞B2⁢p+12=1,
29.6.36 ∑p=0∞(2⁢p+1)⁢B2⁢p+1>0,
29.6.37 limp→∞B2⁢p+1B2⁢p−1=k2(1+k′)2,
ν≠2⁢n+1, or ν=2⁢n+1 and m>n.

Also,

29.6.38 𝐸𝑠ν2⁢m+1⁡(z,k2)=dn⁡(z,k)⁢∑p=0∞D2⁢p+1⁢sin⁡((2⁢p+1)⁢ϕ),

where

29.6.39 (β0−H)⁢D1+α0⁢D3=0,
29.6.40 γp⁢D2⁢p−1+(βp−H)⁢D2⁢p+1+αp⁢D2⁢p+3=0,
p≥1,

with

29.6.41 αp =12⁢(ν−2⁢p−1)⁢(ν+2⁢p+2)⁢k2,
βp ={2−k2−12⁢ν⁢(ν+1)⁢k2,p=0,(2⁢p+1)2⁢(2−k2),p≥1,
γp =12⁢(ν−2⁢p)⁢(ν+2⁢p+1)⁢k2,

and

29.6.42 (1−12⁢k2)⁢∑p=0∞D2⁢p+12+12⁢k2⁢(12⁢D12−∑p=0∞D2⁢p+1⁢D2⁢p+3)=1,
29.6.43 ∑p=0∞(2⁢p+1)⁢D2⁢p+1>0,
29.6.44 limp→∞D2⁢p+1D2⁢p−1=k2(1+k′)2,
ν≠2⁢n+2, or ν=2⁢n+2 and m>n,

§29.6(iv) Function 𝐸𝑠ν2⁢m+2⁡(z,k2)

29.6.46 𝐸𝑠ν2⁢m+2⁡(z,k2)=∑p=1∞B2⁢p⁢sin⁡(2⁢p⁢ϕ).

Here

29.6.47 H=2⁢bν2⁢m+2⁡(k2)−ν⁢(ν+1)⁢k2,
29.6.48 (β0−H)⁢B2+α0⁢B4=0,
29.6.49 γp⁢B2⁢p+(βp−H)⁢B2⁢p+2+αp⁢B2⁢p+4=0,
p≥1,

with αp, βp, and γp as in (29.3.17), and

29.6.50 ∑p=1∞B2⁢p2=1,
29.6.51 ∑p=0∞(2⁢p+2)⁢B2⁢p+2>0,
29.6.52 limp→∞B2⁢p+2B2⁢p=k2(1+k′)2,
ν≠2⁢n+2, or ν=2⁢n+2 and m>n.

Also,

where

29.6.54 (β0−H)⁢D2+α0⁢D4=0,
29.6.55 γp⁢D2⁢p+(βp−H)⁢D2⁢p+2+αp⁢D2⁢p+4=0,
p≥1,

with

29.6.56 αp =12⁢(ν−2⁢p−2)⁢(ν+2⁢p+3)⁢k2,
βp =(2⁢p+2)2⁢(2−k2),
γp =12⁢(ν−2⁢p−1)⁢(ν+2⁢p+2)⁢k2,

and

29.6.57 (1−12⁢k2)⁢∑p=1∞D2⁢p2−12⁢k2⁢∑p=1∞D2⁢p⁢D2⁢p+2=1,
29.6.58 ∑p=0∞(2⁢p+2)⁢D2⁢p+2>0,
29.6.59 limp→∞D2⁢p+2D2⁢p=k2(1+k′)2,
ν≠2⁢n+3, or ν=2⁢n+3 and m>n,