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16 Generalized Hypergeometric Functions & Meijer G-FunctionTwo-Variable Hypergeometric Functions

§16.13 Appell Functions

The following four functions of two real or complex variables x and y cannot be expressed as a product of two {{}_{2}F_{1}} functions, in general, but they satisfy partial differential equations that resemble the hypergeometric differential equation (15.10.1):

16.13.1 {F_{1}}\left(\alpha;\beta,\beta^{\prime};\gamma;x,y\right)=\sum_{m,n=0}^{%
\infty}\frac{{\left(\alpha\right)_{m+n}}{\left(\beta\right)_{m}}{\left(\beta^{%
\prime}\right)_{n}}}{{\left(\gamma\right)_{m+n}}m!n!}x^{m}y^{n},\max\left(|x|,|y|\right)<1,
16.13.2 {F_{2}}\left(\alpha;\beta,\beta^{\prime};\gamma,\gamma^{\prime};x,y\right)=%
\sum_{m,n=0}^{\infty}\frac{{\left(\alpha\right)_{m+n}}{\left(\beta\right)_{m}}%
{\left(\beta^{\prime}\right)_{n}}}{{\left(\gamma\right)_{m}}{\left(\gamma^{%
\prime}\right)_{n}}m!n!}x^{m}y^{n},|x|+|y|<1,
16.13.3 {F_{3}}\left(\alpha,\alpha^{\prime};\beta,\beta^{\prime};\gamma;x,y\right)=%
\sum_{m,n=0}^{\infty}\frac{{\left(\alpha\right)_{m}}{\left(\alpha^{\prime}%
\right)_{n}}{\left(\beta\right)_{m}}{\left(\beta^{\prime}\right)_{n}}}{{\left(%
\gamma\right)_{m+n}}m!n!}x^{m}y^{n},\max\left(|x|,|y|\right)<1,
16.13.4 {F_{4}}\left(\alpha,\beta;\gamma,\gamma^{\prime};x,y\right)=\sum_{m,n=0}^{%
\infty}\frac{{\left(\alpha\right)_{m+n}}{\left(\beta\right)_{m+n}}}{{\left(%
\gamma\right)_{m}}{\left(\gamma^{\prime}\right)_{n}}m!n!}x^{m}y^{n},\sqrt{|x|}+\sqrt{|y|}<1.

Here and elsewhere it is assumed that neither of the bottom parameters \gamma and \gamma^{\prime} is a nonpositive integer.

For large parameter asymptotics see López et al. (2013a, b), and Ferreira et al. (2013a, b).