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15 Hypergeometric FunctionProperties

§15.10 Hypergeometric Differential Equation

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§15.10(i) Fundamental Solutions

This is the hypergeometric differential equation. It has regular singularities at z=0,1,\infty, with corresponding exponent pairs \{0,1-c\}, \{0,c-a-b\}, \{a,b\}, respectively. When none of the exponent pairs differ by an integer, that is, when none of c, c-a-b, a-b is an integer, we have the following pairs f_{1}(z), f_{2}(z) of fundamental solutions. They are also numerically satisfactory (§2.7(iv)) in the neighborhood of the corresponding singularity.

Singularity z=\infty

(a) If c equals n=1,2,3,\dots, and a=1,2,\dots,n-1, then fundamental solutions in the neighborhood of z=0 are given by (15.10.2) with the interpretation (15.2.5) for f_{2}(z).

(b) If c equals n=1,2,3,\dots, and a\neq 1,2,\dots,n-1, then fundamental solutions in the neighborhood of z=0 are given by \mathop{F\/}\nolimits\!\left(a,b;n;z\right) and

Moreover, in (15.10.9) and (15.10.10) the symbols a and b are interchangeable.

(c) If the parameter c in the differential equation equals 2-n=0,-1,-2,\dots, then fundamental solutions in the neighborhood of z=0 are given by z^{{n-1}} times those in (a) and (b), with a and b replaced throughout by a+n-1 and b+n-1, respectively.

(d) If a+b+1-c equals n=1,2,3,\dots, or 2-n=0,-1,-2,\dots, then fundamental solutions in the neighborhood of z=1 are given by those in (a), (b), and (c) with z replaced by 1-z.

(e) Finally, if a-b+1 equals n=1,2,3,\dots, or 2-n=0,-1,-2,\dots, then fundamental solutions in the neighborhood of z=\infty are given by z^{{-a}} times those in (a), (b), and (c) with b and z replaced by a-c+1 and \ifrac{1}{z}, respectively.

§15.10(ii) Kummer’s 24 Solutions and Connection Formulas

The three pairs of fundamental solutions given by (15.10.2), (15.10.4), and (15.10.6) can be transformed into 18 other solutions by means of (15.8.1), leading to a total of 24 solutions known as Kummer’s solutions.

The \binom{6}{3}=20 connection formulas for the principal branches of Kummer’s solutions are: