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17 q-Hypergeometric and Related FunctionsProperties

§17.6 {{}_{2}\phi_{1}} Function

Contents
  1. §17.6(i) Special Values
  2. §17.6(ii) {{}_{2}\phi_{1}} Transformations
  3. §17.6(iii) Contiguous Relations
  4. §17.6(iv) Differential Equations
  5. §17.6(v) q-Integral Representations
  6. §17.6(vi) Continued Fractions

Analytic Continuation

Note that for several of the equations below, the constraints are included to guarantee that the infinite series representation (17.4.1) of the {{}_{2}\phi_{1}} functions converges. These equations can also be used as analytic continuation of these {{}_{2}\phi_{1}} functions.

§17.6(i) Special Values

q-Gauss Sum

17.6.1 {{}_{2}\phi_{1}}\left({a,b\atop c};q,\ifrac{c}{(ab)}\right)=\frac{\left(c/a,c/%
b;q\right)_{\infty}}{\left(c,c/(ab);q\right)_{\infty}},\left|c\right|<\left|ab\right|.

Second q-Chu–Vandermonde Sum

Andrews–Askey Sum

Related formulas are (17.7.3), (17.8.8) and

17.6.4_5 {{}_{2}\phi_{1}}\left({b^{2},\ifrac{b^{2}}{c}\atop cq^{2}};q^{2},\ifrac{cq^{3}%
}{b^{2}}\right)=\frac{1}{2b}\frac{\left(b^{2},q;q^{2}\right)_{\infty}}{\left(%
cq^{2},\ifrac{cq}{b^{2}};q^{2}\right)_{\infty}}\left(\frac{\left(\ifrac{cq}{b}%
;q\right)_{\infty}}{\left(b;q\right)_{\infty}}-\frac{\left(\ifrac{-cq}{b};q%
\right)_{\infty}}{\left(-b;q\right)_{\infty}}\right),\left|cq^{3}\right|<\left|b^{2}\right|.

For similar formulas see Verma and Jain (1983).

§17.6(ii) {{}_{2}\phi_{1}} Transformations

Heine’s Second Tranformation

Heine’s Third Transformation

Three-Term {{}_{2}\phi_{1}} Transformations

17.6.16 {{}_{2}\phi_{1}}\left({a,b\atop c};q,z\right)=\frac{\left(b,c/a,az,q/(az);q%
\right)_{\infty}}{\left(c,b/a,z,q/z;q\right)_{\infty}}{{}_{2}\phi_{1}}\left({a%
,aq/c\atop aq/b};q,cq/(abz)\right)+\frac{\left(a,c/b,bz,q/(bz);q\right)_{%
\infty}}{\left(c,a/b,z,q/z;q\right)_{\infty}}{{}_{2}\phi_{1}}\left({b,bq/c%
\atop bq/a};q,cq/(abz)\right),\left|z\right|<1, \left|cq\right|<\left|abz\right|.

For a similar result for q-confluent hypergeometric functions see Morita (2013).

§17.6(iii) Contiguous Relations

Heine’s Contiguous Relations

§17.6(iv) Differential Equations

q-Differential Equation

(17.6.27) reduces to the hypergeometric equation (15.10.1) with the substitutions a\to q^{a}, b\to q^{b}, c\to q^{c}, followed by \lim_{q\to 1-}.

§17.6(v) q-Integral Representations

where \left|z\right|<1, |\operatorname{ph}\left(-z\right)|<\pi, and the contour of integration separates the poles of \left(q^{1+\zeta},cq^{\zeta};q\right)_{\infty}/\sin\left(\pi\zeta\right) from those of 1/\left(aq^{\zeta},bq^{\zeta};q\right)_{\infty}, and the infimum of the distances of the poles from the contour is positive.

§17.6(vi) Continued Fractions

For continued-fraction representations of the {{}_{2}\phi_{1}} function, see Cuyt et al. (2008, pp. 395–399).