About the Project
9 Airy and Related FunctionsAiry Functions

§9.9 Zeros

Contents
  1. §9.9(i) Distribution and Notation
  2. §9.9(ii) Relation to Modulus and Phase
  3. §9.9(iii) Derivatives With Respect to k
  4. §9.9(iv) Asymptotic Expansions
  5. §9.9(v) Tables

§9.9(i) Distribution and Notation

On the real line, \operatorname{Ai}\left(x\right), \operatorname{Ai}'\left(x\right), \operatorname{Bi}\left(x\right), \operatorname{Bi}'\left(x\right) each have an infinite number of zeros, all of which are negative. They are denoted by a_{k}, a^{\prime}_{k}, b_{k}, b^{\prime}_{k}, respectively, arranged in ascending order of absolute value for k=1,2,\ldots.

\operatorname{Ai}\left(z\right) and \operatorname{Ai}'\left(z\right) have no other zeros. However, \operatorname{Bi}\left(z\right) and \operatorname{Bi}'\left(z\right) each have an infinite number of complex zeros. They lie in the sectors \tfrac{1}{3}\pi<\operatorname{ph}z<\tfrac{1}{2}\pi and -\tfrac{1}{2}\pi<\operatorname{ph}z<-\tfrac{1}{3}\pi, and are denoted by \beta_{k}, \beta^{\prime}_{k}, respectively, in the former sector, and by \overline{\beta_{k}}, \overline{\beta^{\prime}_{k}}, in the conjugate sector, again arranged in ascending order of absolute value (modulus) for k=1,2,\ldots. See §9.3(ii) for visualizations.

For the distribution in \mathbb{C} of the zeros of \operatorname{Ai}'\left(z\right)-\sigma\operatorname{Ai}\left(z\right), where \sigma is an arbitrary complex constant, see Muraveĭ (1976) and Gil and Segura (2014).

§9.9(ii) Relation to Modulus and Phase

9.9.3
\operatorname{Ai}'\left(a_{k}\right)=\frac{(-1)^{k-1}}{\pi M\left(a_{k}\right)},
\operatorname{Bi}'\left(b_{k}\right)=\frac{(-1)^{k-1}}{\pi M\left(b_{k}\right)},
9.9.4
\operatorname{Ai}\left(a^{\prime}_{k}\right)=\frac{(-1)^{k-1}}{\pi N\left(a^{%
\prime}_{k}\right)},
\operatorname{Bi}\left(b^{\prime}_{k}\right)=\frac{(-1)^{k}}{\pi N\left(b^{%
\prime}_{k}\right)}.

§9.9(iii) Derivatives With Respect to k

If k is regarded as a continuous variable, then

9.9.5
\operatorname{Ai}'\left(a_{k}\right)=(-1)^{k-1}\left(-\frac{\mathrm{d}a_{k}}{%
\mathrm{d}k}\right)^{-1/2},
\operatorname{Ai}\left(a^{\prime}_{k}\right)=(-1)^{k-1}\left(a^{\prime}_{k}%
\frac{\mathrm{d}a^{\prime}_{k}}{\mathrm{d}k}\right)^{-1/2}.

See Olver (1954, Appendix).

§9.9(iv) Asymptotic Expansions

For large k

9.9.6 a_{k}=-T\left(\tfrac{3}{8}\pi(4k-1)\right),
9.9.8 a^{\prime}_{k}=-U\left(\tfrac{3}{8}\pi(4k-3)\right),
9.9.10 b_{k}=-T\left(\tfrac{3}{8}\pi(4k-3)\right),
9.9.12 b^{\prime}_{k}=-U\left(\tfrac{3}{8}\pi(4k-1)\right),

Here

9.9.18 T(t)\sim t^{2/3}\left(1+\frac{5}{48}t^{-2}-\frac{5}{36}t^{-4}+\frac{77125}{829%
44}t^{-6}-\frac{1080\;56875}{69\;67296}t^{-8}+\frac{16\;23755\;96875}{3344\;30%
208}t^{-10}-\cdots\right),
9.9.19 U(t)\sim t^{2/3}\left(1-\frac{7}{48}t^{-2}+\frac{35}{288}t^{-4}-\frac{1\;81223%
}{2\;07360}t^{-6}+\frac{186\;83371}{12\;44160}t^{-8}-\frac{9\;11458\;84361}{19%
11\;02976}t^{-10}+\cdots\right),
9.9.20 V(t)\sim\pi^{-1/2}t^{1/6}\left(1+\frac{5}{48}t^{-2}-\frac{1525}{4608}t^{-4}+%
\frac{23\;97875}{6\;63552}t^{-6}-\frac{7\;48989\;40625}{8918\;13888}t^{-8}+%
\frac{14419\;83037\;34375}{4\;28070\;66624}t^{-10}-\cdots\right),
9.9.21 W(t)\sim\pi^{-1/2}t^{-1/6}\left(1-\frac{7}{96}t^{-2}+\frac{1673}{6144}t^{-4}-%
\frac{843\;94709}{265\;42080}t^{-6}+\frac{78\;02771\;35421}{1\;01921\;58720}t^%
{-8}-\frac{20444\;90510\;51945}{6\;52298\;15808}t^{-10}+\cdots\right).

For higher terms see Fabijonas and Olver (1999).

For error bounds for the asymptotic expansions of a_{k}, b_{k}, a^{\prime}_{k}, and b^{\prime}_{k} see Pittaluga and Sacripante (1991), and a conjecture given in Fabijonas and Olver (1999).

§9.9(v) Tables

Tables 9.9.1 and 9.9.2 give 10D values of the first ten real zeros of \operatorname{Ai}, \operatorname{Ai}', \operatorname{Bi}, \operatorname{Bi}', together with the associated values of the derivative or the function. Tables 9.9.3 and 9.9.4 give the corresponding results for the first ten complex zeros of \operatorname{Bi} and \operatorname{Bi}' in the upper half plane.

Table 9.9.1: Zeros of \operatorname{Ai} and \operatorname{Ai}'.
k a_{k} \operatorname{Ai}'\left(a_{k}\right) a^{\prime}_{k} \operatorname{Ai}\left(a^{\prime}_{k}\right)
1 −2.33810 74105 0.70121 08227 −1.01879 29716 0.53565 66560
2 −4.08794 94441 −0.80311 13697 −3.24819 75822 −0.41901 54780
3 −5.52055 98281 0.86520 40259 −4.82009 92112 0.38040 64686
4 −6.78670 80901 −0.91085 07370 −6.16330 73556 −0.35790 79437
5 −7.94413 35871 0.94733 57094 −7.37217 72550 0.34230 12444
6 −9.02265 08533 −0.97792 28086 −8.48848 67340 −0.33047 62291
7 −10.04017 43416 1.00437 01227 −9.53544 90524 0.32102 22882
8 −11.00852 43037 −1.02773 86888 −10.52766 03970 −0.31318 53910
9 −11.93601 55632 1.04872 06486 −11.47505 66335 0.30651 72939
10 −12.82877 67529 −1.06779 38592 −12.38478 83718 −0.30073 08293
Table 9.9.2: Real zeros of \operatorname{Bi} and \operatorname{Bi}'.
k b_{k} \operatorname{Bi}'\left(b_{k}\right) b^{\prime}_{k} \operatorname{Bi}\left(b^{\prime}_{k}\right)
1 −1.17371 32227 0.60195 78880 −2.29443 96826 −0.45494 43836
2 −3.27109 33028 −0.76031 01415 −4.07315 50891 0.39652 28361
3 −4.83073 78417 0.83699 10126 −5.51239 57297 −0.36796 91615
4 −6.16985 21283 −0.88947 99014 −6.78129 44460 0.34949 91168
5 −7.37676 20794 0.92998 36386 −7.94017 86892 −0.33602 62401
6 −8.49194 88465 −0.96323 44302 −9.01958 33588 0.32550 97364
7 −9.53819 43793 0.99158 63705 −10.03769 63349 −0.31693 46537
8 −10.52991 35067 −1.01638 96592 −11.00646 26677 0.30972 59408
9 −11.47695 35513 1.03849 42860 −11.93426 16450 −0.30352 76648
10 −12.38641 71386 −1.05847 18444 −12.82725 83092 0.29810 49111
Table 9.9.3: Complex zeros of \operatorname{Bi}.
e^{-\pi i/3}\beta_{k} \operatorname{Bi}'\left(\beta_{k}\right)
k modulus phase modulus phase
1 2.35387 33809 0.09533 49591 0.99310 68457 2.64060 02521
2 4.09328 73094 0.04178 55604 1.13612 83345 −0.51328 28720
3 5.52350 35011 0.02668 05442 1.22374 37881 2.62462 83591
4 6.78865 95301 0.01958 69751 1.28822 92493 −0.51871 63829
5 7.94555 90160 0.01547 08228 1.33979 47726 2.62185 44560
6 9.02375 63663 0.01278 34808 1.38303 39005 −0.52040 69437
7 10.04106 73680 0.01089 12610 1.42042 53456 2.62071 41895
8 11.00926 72579 0.00948 68445 1.45346 64633 −0.52122 87219
9 11.93664 76131 0.00840 31785 1.48313 45656 2.62009 35195
10 12.82932 39388 0.00754 16607 1.51010 46383 −0.52171 41947
Table 9.9.4: Complex zeros of \operatorname{Bi}'.
e^{-\pi i/3}\beta^{\prime}_{k} \operatorname{Bi}\left(\beta^{\prime}_{k}\right)
k modulus phase modulus phase
1 1.12139 32942 0.33072 66208 0.75004 14897 0.46597 78930
2 3.25690 82266 0.05938 99367 0.59221 66315 −2.63235 40329
3 4.82400 26102 0.03278 56423 0.53787 06321 0.51549 32992
4 6.16568 66408 0.02266 24588 0.50611 02160 −2.62362 85920
5 7.37383 79870 0.01731 96481 0.48406 00643 0.51928 28169
6 8.48973 85596 0.01401 65283 0.46734 68449 −2.62149 05716
7 9.53644 07072 0.01177 19311 0.45398 23240 0.52066 02139
8 10.52847 37502 0.01014 71783 0.44290 25018 −2.62052 78353
9 11.47574 11237 0.00891 66153 0.43347 44668 0.52137 15495
10 12.38537 59341 0.00795 22843 0.42529 25837 −2.61998 05803