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DLMF: §18.22 Hahn Class: Recurrence Relations and Differences ‣ Askey Scheme ‣ Chapter 18 Orthogonal Polynomials
§18.22 Hahn Class: Recurrence Relations and
Differences
Contents
§18.22(i) Recurrence Relations in n
§18.22(ii) Difference Equations in x
§18.22(iii) x -Differences
§18.22(i) Recurrence Relations in n
Hahn
With
18.22.1
p n ( x ) = Q n ( x ; α , β , N ) ,
18.22.2
− x p n ( x ) = A n p n + 1 ( x ) − ( A n + C n ) p n ( x ) + C n p n − 1 ( x ) ,
where
18.22.3
A n
= ( n + α + β + 1 ) ( n + α + 1 ) ( N − n ) ( 2 n + α + β + 1 ) ( 2 n + α + β + 2 ) ,
C n
= n ( n + α + β + N + 1 ) ( n + β ) ( 2 n + α + β ) ( 2 n + α + β + 1 ) .
Krawtchouk, Meixner, and Charlier
These polynomials satisfy (18.22.2 ) with p n ( x ) , A n ,
and C n as in Table 18.22.1 .
Table 18.22.1: Recurrence relations (18.22.2 ) for Krawtchouk,
Meixner, and Charlier polynomials.
Continuous Hahn
With
18.22.4
q n ( x ) = p n ( x ; a , b , a ¯ , b ¯ ) / p n ( i a ; a , b , a ¯ , b ¯ ) ,
18.22.5
( a + i x ) q n ( x ) = A ~ n q n + 1 ( x ) − ( A ~ n + C ~ n ) q n ( x ) + C ~ n q n − 1 ( x ) ,
where
18.22.6
A ~ n
= − ( n + 2 ℜ ( a + b ) − 1 ) ( n + a + a ¯ ) ( n + a + b ¯ ) ( 2 n + 2 ℜ ( a + b ) − 1 ) ( 2 n + 2 ℜ ( a + b ) ) ,
C ~ n
= n ( n + b + a ¯ − 1 ) ( n + b + b ¯ − 1 ) ( 2 n + 2 ℜ ( a + b ) − 2 ) ( 2 n + 2 ℜ ( a + b ) − 1 ) .
Meixner–Pollaczek
With
18.22.7
p n ( x ) = P n ( λ ) ( x ; ϕ ) ,
18.22.8
( n + 1 ) p n + 1 ( x ) = 2 ( x sin ϕ + ( n + λ ) cos ϕ ) p n ( x ) − ( n + 2 λ − 1 ) p n − 1 ( x ) .
§18.22(ii) Difference Equations in x
Hahn
With
18.22.9
p n ( x ) = Q n ( x ; α , β , N ) ,
18.22.10
A ( x ) p n ( x + 1 ) − ( A ( x ) + C ( x ) ) p n ( x ) + C ( x ) p n ( x − 1 ) − n ( n + α + β + 1 ) p n ( x ) = 0 ,
where
18.22.11
A ( x )
= ( x + α + 1 ) ( x − N ) ,
C ( x )
= x ( x − β − N − 1 ) .
Krawtchouk, Meixner, and Charlier
18.22.12
A ( x ) p n ( x + 1 ) − ( A ( x ) + C ( x ) ) p n ( x ) + C ( x ) p n ( x − 1 ) + λ n p n ( x ) = 0 .
For A ( x ) , C ( x ) , and λ n in (18.22.12 ) see Table
18.22.2 .
Table 18.22.2: Difference equations (18.22.12 ) for Krawtchouk,
Meixner, and Charlier polynomials.
Continuous Hahn
With
18.22.13
p n ( x ) = p n ( x ; a , b , a ¯ , b ¯ ) ,
18.22.14
A ( x ) p n ( x + i ) − ( A ( x ) + C ( x ) ) p n ( x ) + C ( x ) p n ( x − i ) + n ( n + 2 ℜ ( a + b ) − 1 ) p n ( x ) = 0 ,
where
18.22.15
A ( x )
= ( x + i a ¯ ) ( x + i b ¯ ) ,
C ( x )
= ( x − i a ) ( x − i b ) .
Meixner–Pollaczek
With
18.22.16
p n ( x ) = P n ( λ ) ( x ; ϕ ) ,
18.22.17
A ( x ) p n ( x + i ) − ( A ( x ) + C ( x ) ) p n ( x ) + C ( x ) p n ( x − i ) + 2 n sin ϕ p n ( x ) = 0 ,
where
18.22.18
A ( x )
= e i ϕ ( x + i λ ) ,
C ( x )
= e − i ϕ ( x − i λ ) .
§18.22(iii) x -Differences
Hahn
18.22.19
Δ x Q n ( x ; α , β , N )
= − n ( n + α + β + 1 ) ( α + 1 ) N Q n − 1 ( x ; α + 1 , β + 1 , N − 1 ) ,
18.22.20
∇ x ( ( α + 1 ) x ( β + 1 ) N − x x ! ( N − x ) ! Q n ( x ; α , β , N ) )
= N + 1 β ( α ) x ( β ) N + 1 − x x ! ( N + 1 − x ) ! Q n + 1 ( x ; α − 1 , β − 1 , N + 1 ) .
Krawtchouk
18.22.21
Δ x K n ( x ; p , N )
= − n p N K n − 1 ( x ; p , N − 1 ) ,
18.22.22
∇ x ( ( N x ) p x ( 1 − p ) N − x K n ( x ; p , N ) )
= ( N + 1 x ) p x ( 1 − p ) N − x K n + 1 ( x ; p , N + 1 ) .
Meixner
18.22.23
Δ x M n ( x ; β , c ) = − n ( 1 − c ) β c M n − 1 ( x ; β + 1 , c ) ,
18.22.24
∇ x ( ( β ) x c x x ! M n ( x ; β , c ) ) = ( β − 1 ) x c x x ! M n + 1 ( x ; β − 1 , c ) .
Charlier
18.22.25
Δ x C n ( x ; a )
= − n a C n − 1 ( x ; a ) ,
18.22.26
∇ x ( a x x ! C n ( x ; a ) )
= a x x ! C n + 1 ( x ; a ) .
Continuous Hahn
18.22.27
δ x ( p n ( x ; a , b , a ¯ , b ¯ ) ) = ( n + 2 ℜ ( a + b ) − 1 ) p n − 1 ( x ; a + 1 2 , b + 1 2 , a ¯ + 1 2 , b ¯ + 1 2 ) ,
18.22.28
δ x ( w ( x ; a + 1 2 , b + 1 2 , a ¯ + 1 2 , b ¯ + 1 2 ) p n ( x ; a + 1 2 , b + 1 2 , a ¯ + 1 2 , b ¯ + 1 2 ) ) = − ( n + 1 ) w ( x ; a , b , a ¯ , b ¯ ) p n + 1 ( x ; a , b , a ¯ , b ¯ ) .
Meixner–Pollaczek
18.22.29
δ x ( P n ( λ ) ( x ; ϕ ) ) = 2 sin ϕ P n − 1 ( λ + 1 2 ) ( x ; ϕ ) ,
18.22.30
δ x ( w ( λ + 1 2 ) ( x ; ϕ ) P n ( λ + 1 2 ) ( x ; ϕ ) ) = − ( n + 1 ) w ( λ ) ( x ; ϕ ) P n + 1 ( λ ) ( x ; ϕ ) .