Digital Library of Mathematical Functions
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29 Lamé FunctionsLamé Functions

§29.7 Asymptotic Expansions

Contents

§29.7(i) Eigenvalues

As ν,

29.7.1 aνm(k2)pκ-τ0-τ1κ-1-τ2κ-2-,

where

29.7.2 κ =k(ν(ν+1))1/2,
p =2m+1,
29.7.3 τ0 =123(1+k2)(1+p2),
29.7.4 τ1 =p26((1+k2)2(p2+3)-4k2(p2+5)).

The same Poincaré expansion holds for bνm+1(k2), since

29.7.5 bνm+1(k2)-aνm(k2)=O(νm+32(1-k1+k)ν),
ν.

See also Volkmer (2004b).

29.7.6 τ2=1210(1+k2)(1-k2)2(5p4+34p2+9),
29.7.7 τ3=p214((1+k2)4(33p4+410p2+405)-24k2(1+k2)2(7p4+90p2+95)+16k4(9p4+130p2+173),)
29.7.8 τ4=1216((1+k2)5(63p6+1260p4+2943p2+486)-8k2(1+k2)3(49p6+1010p4+2493p2+432)+16k4(1+k2)(35p6+760p4+2043p2+378).)

Formulas for additional terms can be computed with the author’s Maple program LA5; see §29.22.

§29.7(ii) Lamé Functions

Müller (1966a, b) found three formal asymptotic expansions for a fundamental system of solutions of (29.2.1) (and (29.11.1)) as ν, one in terms of Jacobian elliptic functions and two in terms of Hermite polynomials. In Müller (1966c) it is shown how these expansions lead to asymptotic expansions for the Lamé functions Ecνm(z,k2) and Esνm(z,k2). Weinstein and Keller (1985) give asymptotics for solutions of Hill’s equation (§28.29(i)) that are applicable to the Lamé equation.