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9 Airy and Related FunctionsRelated Functions

§9.12 Scorer Functions

Contents
  1. §9.12(i) Differential Equation
  2. §9.12(ii) Graphs
  3. §9.12(iii) Initial Values
  4. §9.12(iv) Numerically Satisfactory Solutions
  5. §9.12(v) Connection Formulas
  6. §9.12(vi) Maclaurin Series
  7. §9.12(vii) Integral Representations
  8. §9.12(viii) Asymptotic Expansions
  9. §9.12(ix) Zeros

§9.12(i) Differential Equation

9.12.1 \frac{{\mathrm{d}}^{2}w}{{\mathrm{d}z}^{2}}-zw=\frac{1}{\pi}.

Solutions of this equation are the Scorer functions and can be found by the method of variation of parameters (§1.13(iii)). The general solution is given by

9.12.2 w(z)=Aw_{1}(z)+Bw_{2}(z)+p(z),

where A and B are arbitrary constants, w_{1}(z) and w_{2}(z) are any two linearly independent solutions of Airy’s equation (9.2.1), and p(z) is any particular solution of (9.12.1). Standard particular solutions are

where

9.12.4 \operatorname{Gi}\left(z\right)=\operatorname{Bi}\left(z\right)\int_{z}^{%
\infty}\operatorname{Ai}\left(t\right)\,\mathrm{d}t+\operatorname{Ai}\left(z%
\right)\int_{0}^{z}\operatorname{Bi}\left(t\right)\,\mathrm{d}t,
9.12.5 \operatorname{Hi}\left(z\right)=\operatorname{Bi}\left(z\right)\int_{-\infty}^%
{z}\operatorname{Ai}\left(t\right)\,\mathrm{d}t-\operatorname{Ai}\left(z\right%
)\int_{-\infty}^{z}\operatorname{Bi}\left(t\right)\,\mathrm{d}t.

\operatorname{Gi}\left(z\right) and \operatorname{Hi}\left(z\right) are entire functions of z.

§9.12(ii) Graphs

See Figures 9.12.1 and 9.12.2.

See accompanying text
Figure 9.12.1: \operatorname{Gi}\left(x\right), \operatorname{Gi}'\left(x\right). Magnify
See accompanying text
Figure 9.12.2: \operatorname{Hi}\left(x\right), \operatorname{Hi}'\left(x\right). Magnify

§9.12(iii) Initial Values

§9.12(iv) Numerically Satisfactory Solutions

-\operatorname{Gi}\left(x\right) is a numerically satisfactory companion to the complementary functions \operatorname{Ai}\left(x\right) and \operatorname{Bi}\left(x\right) on the interval 0\leq x<\infty. \operatorname{Hi}\left(x\right) is a numerically satisfactory companion to \operatorname{Ai}\left(x\right) and \operatorname{Bi}\left(x\right) on the interval -\infty<x\leq 0.

§9.12(v) Connection Formulas

9.12.11 \operatorname{Gi}\left(z\right)+\operatorname{Hi}\left(z\right)=\operatorname{%
Bi}\left(z\right),

§9.12(vi) Maclaurin Series

9.12.17 \operatorname{Hi}\left(z\right)=\frac{3^{-2/3}}{\pi}\sum_{k=0}^{\infty}\Gamma%
\left(\frac{k+1}{3}\right)\frac{(3^{1/3}z)^{k}}{k!},

§9.12(vii) Integral Representations

Mellin–Barnes Type Integral

where the integration contour separates the poles of \Gamma\left(\tfrac{1}{3}+\tfrac{1}{3}t\right) from those of \Gamma\left(-t\right).

§9.12(viii) Asymptotic Expansions

Functions and Derivatives

As z\to\infty, and with \delta denoting an arbitrary small positive constant,

For other phase ranges combine these results with the connection formulas (9.12.11)–(9.12.14) and the asymptotic expansions given in §9.7. For example, with the notation of §9.7(i),

Integrals

9.12.30 \int_{0}^{z}\operatorname{Gi}\left(t\right)\,\mathrm{d}t\sim\frac{1}{\pi}\ln z%
+\frac{2\gamma+\ln 3}{3\pi}-\frac{1}{\pi}\sum_{k=1}^{\infty}\frac{(3k-1)!}{k!(%
3z^{3})^{k}},|\operatorname{ph}z|\leq\tfrac{1}{3}\pi-\delta.
9.12.31 \int_{0}^{z}\operatorname{Hi}\left(-t\right)\,\mathrm{d}t\sim\frac{1}{\pi}\ln z%
+\frac{2\gamma+\ln 3}{3\pi}+\frac{1}{\pi}\sum_{k=1}^{\infty}(-1)^{k-1}\frac{(3%
k-1)!}{k!(3z^{3})^{k}},|\operatorname{ph}z|\leq\tfrac{2}{3}\pi-\delta,

where \gamma is Euler’s constant (§5.2(ii)).

§9.12(ix) Zeros

All zeros, real or complex, of \operatorname{Gi}\left(z\right) and \operatorname{Hi}\left(z\right) are simple.

Neither \operatorname{Hi}\left(z\right) nor \operatorname{Hi}'\left(z\right) has real zeros.

\operatorname{Gi}\left(z\right) has no nonnegative real zeros and \operatorname{Gi}'\left(z\right) has exactly one nonnegative real zero, given by z=0.60907\;54170\;7\dotsc. Both \operatorname{Gi}\left(z\right) and \operatorname{Gi}'\left(z\right) have an infinity of negative real zeros, and they are interlaced.

For the above properties and further results, including the distribution of complex zeros, asymptotic approximations for the numerically large real or complex zeros, and numerical tables see Gil et al. (2003c).

For graphical illustration of the real zeros see Figures 9.12.1 and 9.12.2.