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10 Bessel FunctionsBessel and Hankel Functions

§10.19 Asymptotic Expansions for Large Order

Contents
  1. §10.19(i) Asymptotic Forms
  2. §10.19(ii) Debye’s Expansions
  3. §10.19(iii) Transition Region

§10.19(ii) Debye’s Expansions

If \nu\to\infty through positive real values with \beta\left(\in\left(0,\tfrac{1}{2}\pi\right)\right) fixed, and

10.19.5 \xi=\nu(\tan\beta-\beta)-\tfrac{1}{4}\pi,

then

In these expansions U_{k}(p) and V_{k}(p) are the polynomials in p of degree 3k defined in §10.41(ii).

For error bounds for the first of (10.19.6) see Olver (1997b, p. 382).

§10.19(iii) Transition Region

As \nu\to\infty, with a(\in\mathbb{C}) fixed,

10.19.8
J_{\nu}\left(\nu+a\nu^{\frac{1}{3}}\right)\sim\frac{2^{\frac{1}{3}}}{\nu^{%
\frac{1}{3}}}\operatorname{Ai}\left(-2^{\frac{1}{3}}a\right)\sum_{k=0}^{\infty%
}\frac{P_{k}(a)}{\nu^{2k/3}}+\frac{2^{\frac{2}{3}}}{\nu}\operatorname{Ai}'%
\left(-2^{\frac{1}{3}}a\right)\sum_{k=0}^{\infty}\frac{Q_{k}(a)}{\nu^{2k/3}},|\operatorname{ph}\nu|\leq\tfrac{1}{2}\pi-\delta,
Y_{\nu}\left(\nu+a\nu^{\frac{1}{3}}\right)\sim-\frac{2^{\frac{1}{3}}}{\nu^{%
\frac{1}{3}}}\operatorname{Bi}\left(-2^{\frac{1}{3}}a\right)\sum_{k=0}^{\infty%
}\frac{P_{k}(a)}{\nu^{2k/3}}-\frac{2^{\frac{2}{3}}}{\nu}\operatorname{Bi}'%
\left(-2^{\frac{1}{3}}a\right)\sum_{k=0}^{\infty}\frac{Q_{k}(a)}{\nu^{2k/3}},|\operatorname{ph}\nu|\leq\tfrac{1}{2}\pi-\delta.

Also,

10.19.9 \rselection{{H^{(1)}_{\nu}}\left(\nu+a\nu^{\frac{1}{3}}\right)\\
{H^{(2)}_{\nu}}\left(\nu+a\nu^{\frac{1}{3}}\right)}\sim\frac{2^{\frac{4}{3}}}{%
\nu^{\frac{1}{3}}}e^{\mp\pi i/3}\operatorname{Ai}\left(e^{\mp\pi i/3}2^{\frac{%
1}{3}}a\right)\sum_{k=0}^{\infty}\frac{P_{k}(a)}{\nu^{2k/3}}+\frac{2^{\frac{5}%
{3}}}{\nu}e^{\pm\pi i/3}\operatorname{Ai}'\left(e^{\mp\pi i/3}2^{\frac{1}{3}}a%
\right)\sum_{k=0}^{\infty}\frac{Q_{k}(a)}{\nu^{2k/3}},

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

10.19.10
P_{0}(a)=1,
P_{1}(a)=-\tfrac{1}{5}a,
P_{2}(a)=-\tfrac{9}{100}a^{5}+\tfrac{3}{35}a^{2},
P_{3}(a)=\tfrac{957}{7000}a^{6}-\tfrac{173}{3150}a^{3}-\tfrac{1}{225},
P_{4}(a)=\tfrac{27}{20000}a^{10}-\tfrac{23573}{1\;47000}a^{7}+\tfrac{5903}{1\;%
38600}a^{4}+\tfrac{947}{3\;46500}a,
10.19.11
Q_{0}(a)=\tfrac{3}{10}a^{2},
Q_{1}(a)=-\tfrac{17}{70}a^{3}+\tfrac{1}{70},
Q_{2}(a)=-\tfrac{9}{1000}a^{7}+\tfrac{611}{3150}a^{4}-\tfrac{37}{3150}a,
Q_{3}(a)=\tfrac{549}{28000}a^{8}-\tfrac{1\;10767}{6\;93000}a^{5}+\tfrac{79}{12%
375}a^{2}.

with sectors of validity -\tfrac{1}{2}\pi+\delta\leq\operatorname{ph}\nu\leq\tfrac{3}{2}\pi-\delta and -\tfrac{3}{2}\pi+\delta\leq\operatorname{ph}\nu\leq\tfrac{1}{2}\pi-\delta, respectively. Here

10.19.14
R_{0}(a)=1,
R_{1}(a)=-\tfrac{4}{5}a,
R_{2}(a)=-\tfrac{9}{100}a^{5}+\tfrac{57}{70}a^{2},
R_{3}(a)=\tfrac{699}{3500}a^{6}-\tfrac{2617}{3150}a^{3}+\tfrac{23}{3150},
R_{4}(a)=\tfrac{27}{20000}a^{10}-\tfrac{46631}{1\;47000}a^{7}+\tfrac{3889}{462%
0}a^{4}-\tfrac{1159}{1\;15500}a,
10.19.15
S_{0}(a)=\tfrac{3}{5}a^{3}-\tfrac{1}{5},
S_{1}(a)=-\tfrac{131}{140}a^{4}+\tfrac{1}{5}a,
S_{2}(a)=-\tfrac{9}{500}a^{8}+\tfrac{5437}{4500}a^{5}-\tfrac{593}{3150}a^{2},
S_{3}(a)=\tfrac{369}{7000}a^{9}-\tfrac{9\;99443}{6\;93000}a^{6}+\tfrac{31727}{%
1\;73250}a^{3}+\tfrac{947}{3\;46500}.

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 J_{\nu}\left(\nu\right) and Y_{\nu}\left(\nu\right)), see Watson (1944, §8.21), Temme (1997), and Jentschura and Lötstedt (2012). The last reference also includes the corresponding expansions for J_{\nu}'\left(\nu\right) and Y_{\nu}'\left(\nu\right).

See also §10.20(i).