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►In his paper Lauricella’s hypergeometric function
(1963), he defined the -function, a multivariate hypergeometric function that is homogeneous in its variables, each variable being paired with a parameter.
If some of the parameters are equal, then the -function is symmetric in the corresponding variables.
…Also, the homogeneity of the -function has led to a new type of mean value for several variables, accompanied by various inequalities.
►The foregoing matters are discussed in Carlson’s book Special Functions of Applied Mathematics, published by Academic Press in 1977.
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►With two real variables, special functions are depicted as 3D surfaces, with vertical height corresponding to the value of the function, and coloring added to emphasize the 3D nature.
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►Special functions with a complex variable are depicted as colored 3D surfaces in a similar way to functions of two real variables, but with the vertical height corresponding to the modulus (absolute value) of the function.
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►The main functions treated in this chapter are the multivariate gamma and beta functions, respectively and , and the special functions of matrix argument: Bessel (of the first kind) and (of the second kind) ; confluent hypergeometric (of the first kind) or and (of the second kind) ; Gaussian hypergeometric or ; generalized hypergeometric or .
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►When the path of integration excludes the origin and does not cross the negative real axis (8.19.2) defines the principal value of , and unless indicated otherwise in the DLMF principal values are assumed.
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►In Figures 8.19.2–8.19.5, height corresponds to the absolute value of the function and color to the phase.
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Derivable by starting with (25.11.1), replacing
, pulling out a factor of and performing a change of sum
index with and , which through Euclidean division
converts the single sum into a double sum of the correct form.