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DLMF: §10.6 Recurrence Relations and Derivatives ‣ Bessel and Hankel Functions ‣ Chapter 10 Bessel Functions
§10.6 Recurrence Relations and Derivatives
Contents
§10.6(i) Recurrence Relations
§10.6(ii) Derivatives
§10.6(iii) Cross-Products
§10.6(i) Recurrence Relations
With 𝒞 ν ( z ) defined as in §10.2(ii) ,
10.6.1
𝒞 ν − 1 ( z ) + 𝒞 ν + 1 ( z )
= ( 2 ν / z ) 𝒞 ν ( z ) ,
𝒞 ν − 1 ( z ) − 𝒞 ν + 1 ( z )
= 2 𝒞 ν ′ ( z ) .
10.6.2
𝒞 ν ′ ( z )
= 𝒞 ν − 1 ( z ) − ( ν / z ) 𝒞 ν ( z ) ,
𝒞 ν ′ ( z )
= − 𝒞 ν + 1 ( z ) + ( ν / z ) 𝒞 ν ( z ) .
10.6.3
J 0 ′ ( z )
= − J 1 ( z ) ,
Y 0 ′ ( z )
= − Y 1 ( z ) ,
H 0 ( 1 ) ′ ( z )
= − H 1 ( 1 ) ( z ) ,
H 0 ( 2 ) ′ ( z )
= − H 1 ( 2 ) ( z ) .
If f ν ( z ) = z p 𝒞 ν ( λ z q ) , where p , q , and
λ (≠ 0 ) are real or complex constants, then
10.6.4
f ν − 1 ( z ) + f ν + 1 ( z )
= ( 2 ν / λ ) z − q f ν ( z ) ,
( p + ν q ) f ν − 1 ( z ) + ( p − ν q ) f ν + 1 ( z )
= ( 2 ν / λ ) z 1 − q f ν ′ ( z ) .
10.6.5
z f ν ′ ( z )
= λ q z q f ν − 1 ( z ) + ( p − ν q ) f ν ( z ) ,
z f ν ′ ( z )
= − λ q z q f ν + 1 ( z ) + ( p + ν q ) f ν ( z ) .
For results on modified quotients of the form z 𝒞 ν ± 1 ( z ) / 𝒞 ν ( z ) see
Onoe (1955 ) and Onoe (1956 ) .
§10.6(ii) Derivatives
For k = 0 , 1 , 2 , … ,
10.6.6
( 1 z d d z ) k ( z ν 𝒞 ν ( z ) )
= z ν − k 𝒞 ν − k ( z ) ,
( 1 z d d z ) k ( z − ν 𝒞 ν ( z ) )
= ( − 1 ) k z − ν − k 𝒞 ν + k ( z ) .
10.6.7
𝒞 ν ( k ) ( z ) = 1 2 k ∑ n = 0 k ( − 1 ) n ( k n ) 𝒞 ν − k + 2 n ( z ) .
§10.6(iii) Cross-Products
Let
10.6.8
p ν
= J ν ( a ) Y ν ( b ) − J ν ( b ) Y ν ( a ) ,
q ν
= J ν ( a ) Y ν ′ ( b ) − J ν ′ ( b ) Y ν ( a ) ,
r ν
= J ν ′ ( a ) Y ν ( b ) − J ν ( b ) Y ν ′ ( a ) ,
s ν
= J ν ′ ( a ) Y ν ′ ( b ) − J ν ′ ( b ) Y ν ′ ( a ) ,
where a and b are independent of ν . Then
10.6.9
p ν + 1 − p ν − 1
= − 2 ν a q ν − 2 ν b r ν ,
q ν + 1 + r ν
= ν a p ν − ν + 1 b p ν + 1 ,
r ν + 1 + q ν
= ν b p ν − ν + 1 a p ν + 1 ,
s ν
= 1 2 p ν + 1 + 1 2 p ν − 1 − ν 2 a b p ν ,
and
10.6.10
p ν s ν − q ν r ν = 4 / ( π 2 a b ) .