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10 Bessel FunctionsBessel and Hankel Functions

§10.6 Recurrence Relations and Derivatives

Contents
  1. §10.6(i) Recurrence Relations
  2. §10.6(ii) Derivatives
  3. §10.6(iii) Cross-Products

§10.6(i) Recurrence Relations

With \mathscr{C}_{\nu}\left(z\right) defined as in §10.2(ii),

10.6.1
\mathscr{C}_{\nu-1}\left(z\right)+\mathscr{C}_{\nu+1}\left(z\right)=(2\nu/z)%
\mathscr{C}_{\nu}\left(z\right),
\mathscr{C}_{\nu-1}\left(z\right)-\mathscr{C}_{\nu+1}\left(z\right)=2\mathscr{%
C}_{\nu}'\left(z\right).
10.6.2
\mathscr{C}_{\nu}'\left(z\right)=\mathscr{C}_{\nu-1}\left(z\right)-(\nu/z)%
\mathscr{C}_{\nu}\left(z\right),
\mathscr{C}_{\nu}'\left(z\right)=-\mathscr{C}_{\nu+1}\left(z\right)+(\nu/z)%
\mathscr{C}_{\nu}\left(z\right).

If f_{\nu}(z)=z^{p}\mathscr{C}_{\nu}\left(\lambda z^{q}\right), where p,q, and \lambda (\neq 0) are real or complex constants, then

10.6.4
f_{\nu-1}(z)+f_{\nu+1}(z)=(2\nu/\lambda)z^{-q}f_{\nu}(z),
(p+\nu q)f_{\nu-1}(z)+(p-\nu q)f_{\nu+1}(z)=(2\nu/\lambda)z^{1-q}f_{\nu}^{%
\prime}(z).
10.6.5
zf_{\nu}^{\prime}(z)=\lambda qz^{q}f_{\nu-1}(z)+(p-\nu q)f_{\nu}(z),
zf_{\nu}^{\prime}(z)=-\lambda qz^{q}f_{\nu+1}(z)+(p+\nu q)f_{\nu}(z).

For results on modified quotients of the form \ifrac{z\mathscr{C}_{\nu\pm 1}\left(z\right)}{\mathscr{C}_{\nu}\left(z\right)} see Onoe (1955) and Onoe (1956).

§10.6(ii) Derivatives

For k=0,1,2,\dotsc,

10.6.6
\left(\frac{1}{z}\frac{\mathrm{d}}{\mathrm{d}z}\right)^{k}\left(z^{\nu}%
\mathscr{C}_{\nu}\left(z\right)\right)=z^{\nu-k}\mathscr{C}_{\nu-k}\left(z%
\right),
\left(\frac{1}{z}\frac{\mathrm{d}}{\mathrm{d}z}\right)^{k}(z^{-\nu}\mathscr{C}%
_{\nu}\left(z\right))=(-1)^{k}z^{-\nu-k}\mathscr{C}_{\nu+k}\left(z\right).
10.6.7 {\mathscr{C}_{\nu}}^{(k)}\left(z\right)=\frac{1}{2^{k}}\sum_{n=0}^{k}(-1)^{n}%
\genfrac{(}{)}{0.0pt}{}{k}{n}\mathscr{C}_{\nu-k+2n}\left(z\right).

§10.6(iii) Cross-Products

Let

10.6.8
p_{\nu}=J_{\nu}\left(a\right)Y_{\nu}\left(b\right)-J_{\nu}\left(b\right)Y_{\nu%
}\left(a\right),
q_{\nu}=J_{\nu}\left(a\right)Y_{\nu}'\left(b\right)-J_{\nu}'\left(b\right)Y_{%
\nu}\left(a\right),
r_{\nu}=J_{\nu}'\left(a\right)Y_{\nu}\left(b\right)-J_{\nu}\left(b\right)Y_{%
\nu}'\left(a\right),
s_{\nu}=J_{\nu}'\left(a\right)Y_{\nu}'\left(b\right)-J_{\nu}'\left(b\right)Y_{%
\nu}'\left(a\right),

where a and b are independent of \nu. Then

10.6.9
p_{\nu+1}-p_{\nu-1}=-\frac{2\nu}{a}q_{\nu}-\frac{2\nu}{b}r_{\nu},
q_{\nu+1}+r_{\nu}=\frac{\nu}{a}p_{\nu}-\frac{\nu+1}{b}p_{\nu+1},
r_{\nu+1}+q_{\nu}=\frac{\nu}{b}p_{\nu}-\frac{\nu+1}{a}p_{\nu+1},
s_{\nu}=\tfrac{1}{2}p_{\nu+1}+\tfrac{1}{2}p_{\nu-1}-\frac{\nu^{2}}{ab}p_{\nu},

and