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10 Bessel FunctionsBessel and Hankel Functions

§10.19 Asymptotic Expansions for Large Order

Contents

§10.19(ii) Debye’s Expansions

For error bounds for the first of (10.19.3) see Olver (1997b, p. 382).

§10.19(iii) Transition Region

As \nu\to\infty, with a(\in\Complex) fixed,

with sectors of validity -\tfrac{1}{2}\pi+\delta\leq\pm\mathop{\mathrm{ph}\/}\nolimits\nu\leq\tfrac{3}{%
2}\pi-\delta. Here \mathop{\mathrm{Ai}\/}\nolimits and \mathop{\mathrm{Bi}\/}\nolimits are the Airy functions (§9.2), and

10.19.10
\mathop{P_{{0}}\/}\nolimits\!\left(a\right)=1,
\mathop{P_{{1}}\/}\nolimits\!\left(a\right)=-\tfrac{1}{5}a,
\mathop{P_{{2}}\/}\nolimits\!\left(a\right)=-\tfrac{9}{100}a^{5}+\tfrac{3}{35}%
a^{2},
\mathop{P_{{3}}\/}\nolimits\!\left(a\right)=\tfrac{957}{7000}a^{6}-\tfrac{173}%
{3150}a^{3}-\tfrac{1}{225},
\mathop{P_{{4}}\/}\nolimits\!\left(a\right)=\tfrac{27}{20000}a^{{10}}-\tfrac{2%
3573}{1\;47000}a^{7}+\tfrac{5903}{1\;38600}a^{4}+\tfrac{947}{3\;46500}a,
10.19.11
\mathop{Q_{{0}}\/}\nolimits\!\left(a\right)=\tfrac{3}{10}a^{2},
\mathop{Q_{{1}}\/}\nolimits\!\left(a\right)=-\tfrac{17}{70}a^{3}+\tfrac{1}{70},
\mathop{Q_{{2}}\/}\nolimits\!\left(a\right)=-\tfrac{9}{1000}a^{7}+\tfrac{611}{%
3150}a^{4}-\tfrac{37}{3150}a,
\mathop{Q_{{3}}\/}\nolimits\!\left(a\right)=-\tfrac{549}{28000}a^{8}-\tfrac{1%
\;10767}{6\;93000}a^{5}+\tfrac{79}{12375}a^{2}.

For proofs and also for the corresponding expansions for second derivatives see Olver (1952).

For higher coefficients in (10.19.8) in the case a=0 (that is, in the expansions of \mathop{J_{{\nu}}\/}\nolimits\!\left(\nu\right) and \mathop{Y_{{\nu}}\/}\nolimits\!\left(\nu\right)), see Watson (1944, §8.21), Temme (1997), and Jentschura and Lötstedt (2012). The last reference also includes the corresponding expansions for {\mathop{J_{{\nu}}\/}\nolimits^{{\prime}}}\!\left(\nu\right) and {\mathop{Y_{{\nu}}\/}\nolimits^{{\prime}}}\!\left(\nu\right).