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11: 18.14 Inequalities
Ultraspherical
18.14.4 | C n ( λ ) ( x ) | C n ( λ ) ( 1 ) = ( 2 λ ) n n ! , 1 x 1 , λ > 0 .
18.14.5 | C 2 m ( λ ) ( x ) | | C 2 m ( λ ) ( 0 ) | = | ( λ ) m m ! | , 1 x 1 , 1 2 < λ < 0 ,
18.14.6 | C 2 m + 1 ( λ ) ( x ) | < 2 ( λ ) m + 1 ( ( 2 m + 1 ) ( 2 λ + 2 m + 1 ) ) 1 2 m ! , 1 x 1 , 1 2 < λ < 0 .
18.14.7 ( n + λ ) 1 λ ( 1 x 2 ) 1 2 λ | C n ( λ ) ( x ) | < 2 1 λ Γ ( λ ) , 1 x 1 , 0 < λ < 1 .
12: 18.5 Explicit Representations
Table 18.5.1: Classical OP’s: Rodrigues formulas (18.5.5).
p n ( x ) w ( x ) F ( x ) κ n
C n ( λ ) ( x ) ( 1 x 2 ) λ 1 2 1 x 2 ( 2 ) n ( λ + 1 2 ) n n ! ( 2 λ ) n
See (Erdélyi et al., 1953b, §10.9(37)) for a related formula for ultraspherical polynomials. …
18.5.11 C n ( λ ) ( cos θ ) = = 0 n ( λ ) ( λ ) n ! ( n ) ! cos ( ( n 2 ) θ ) = e i n θ ( λ ) n n ! F 1 2 ( n , λ 1 λ n ; e 2 i θ ) .
Similarly in the cases of the ultraspherical polynomials C n ( λ ) ( x ) and the Laguerre polynomials L n ( α ) ( x ) we assume that λ > 1 2 , λ 0 , and α > 1 , unless stated otherwise. …
13: 1.10 Functions of a Complex Variable
Ultraspherical polynomials have generating function
1.10.28 F ( x , λ ; z ) = ( 1 2 x z + z 2 ) λ = n = 0 C n ( λ ) ( x ) z n , | z | < 1 .
1.10.29 n = 0 d d x C n ( λ ) ( x ) z n = 2 λ z ( 1 2 x z + z 2 ) λ 1 = n = 0 2 λ C n ( λ + 1 ) ( x ) z n + 1 ,
and hence d d x C n ( λ ) ( x ) = 2 λ C n 1 ( λ + 1 ) ( x ) , that is (18.9.19). The recurrence relation for C n ( λ ) ( x ) in §18.9(i) follows from ( 1 2 x z + z 2 ) z F ( x , λ ; z ) = 2 λ ( x z ) F ( x , λ ; z ) , and the contour integral representation for C n ( λ ) ( x ) in §18.10(iii) is just (1.10.27).
14: 10.23 Sums
10.23.8 𝒞 ν ( w ) w ν = 2 ν Γ ( ν ) k = 0 ( ν + k ) 𝒞 ν + k ( u ) u ν J ν + k ( v ) v ν C k ( ν ) ( cos α ) , ν 0 , 1 , , | v e ± i α | < | u | ,
where C k ( ν ) ( cos α ) is Gegenbauer’s polynomial18.3). …
10.23.9 e i v cos α = Γ ( ν ) ( 1 2 v ) ν k = 0 ( ν + k ) i k J ν + k ( v ) C k ( ν ) ( cos α ) , ν 0 , 1 , .
15: 18.11 Relations to Other Functions
Ultraspherical
18.11.1 𝖯 n m ( x ) = ( 1 2 ) m ( 2 ) m ( 1 x 2 ) 1 2 m C n m ( m + 1 2 ) ( x ) = ( n + 1 ) m ( 2 ) m ( 1 x 2 ) 1 2 m P n m ( m , m ) ( x ) , 0 m n .
16: 15.9 Relations to Other Functions
Gegenbauer (or Ultraspherical)
This is a generalization of Gegenbauer (or ultraspherical) polynomials18.3). …
17: 18.28 Askey–Wilson Class
§18.28(v) Continuous q -Ultraspherical Polynomials
18.28.13 C n ( cos θ ; β | q ) = = 0 n ( β ; q ) ( β ; q ) n ( q ; q ) ( q ; q ) n e i ( n 2 ) θ = ( β ; q ) n ( q ; q ) n e i n θ ϕ 1 2 ( q n , β β 1 q 1 n ; q , β 1 q e 2 i θ ) .
18.28.25 P n ( λ 1 2 , λ 1 2 ) ( x | q ) = q 1 2 n λ ( q λ + 1 / 2 ; q ) n ( q 2 λ ; q ) n C n ( x ; q λ | q ) .
18.28.31 lim q 1 C n ( x ; q λ | q ) = C n ( λ ) ( x ) .
18.28.32 lim β 0 C n ( x ; β | q ) = H n ( x | q ) ( q ; q ) n .
18: 18.35 Pollaczek Polynomials
The type 2 polynomials reduce for a = b = 0 to ultraspherical polynomials, see (18.35.8). …
18.35.8 P n ( λ ) ( x ; 0 , 0 ) = C n ( λ ) ( x ) ,
For the ultraspherical polynomials C n ( λ ) ( x ) , the Meixner–Pollaczek polynomials P n ( λ ) ( x ; ϕ ) and the associated Meixner–Pollaczek polynomials 𝒫 n λ ( x ; ϕ , c ) see §§18.3, 18.19 and 18.30(v), respectively. …
19: 18.15 Asymptotic Approximations
§18.15(ii) Ultraspherical
18.15.10 C n ( λ ) ( cos θ ) = 2 2 λ Γ ( λ + 1 2 ) π 1 2 Γ ( λ + 1 ) ( 2 λ ) n ( λ + 1 ) n ( m = 0 M 1 ( λ ) m ( 1 λ ) m m ! ( n + λ + 1 ) m cos θ n , m ( 2 sin θ ) m + λ + O ( 1 n M ) ) ,
Asymptotic expansions for C n ( λ ) ( cos θ ) can be obtained from the results given in §18.15(i) by setting α = β = λ 1 2 and referring to (18.7.1). … For asymptotic approximations of Jacobi, ultraspherical, and Laguerre polynomials in terms of Hermite polynomials, see López and Temme (1999a). These approximations apply when the parameters are large, namely α and β (subject to restrictions) in the case of Jacobi polynomials, λ in the case of ultraspherical polynomials, and | α | + | x | in the case of Laguerre polynomials. …
20: 10.60 Sums
Then with P n again denoting the Legendre polynomial of degree n ,
10.60.1 cos w w = n = 0 ( 2 n + 1 ) 𝗃 n ( v ) 𝗒 n ( u ) P n ( cos α ) , | v e ± i α | < | u | .
10.60.2 sin w w = n = 0 ( 2 n + 1 ) 𝗃 n ( v ) 𝗃 n ( u ) P n ( cos α ) .
10.60.7 e i z cos α = n = 0 ( 2 n + 1 ) i n 𝗃 n ( z ) P n ( cos α ) ,
10.60.8 e z cos α = n = 0 ( 2 n + 1 ) 𝗂 n ( 1 ) ( z ) P n ( cos α ) ,