Core Concepts
Multivariable hypergeometric functions are analyzed for analytic continuations and numerical evaluations in the context of Feynman integrals.
Abstract
The content delves into the investigation of Appell F1, F3, Lauricella F (3) D, and Lauricella-Saran F (3) S series for their analytic continuations and numerical evaluations. The study aims to cover the real (x, y, z) space, excluding singular loci, crucial for Feynman integral calculations. Mathematica packages are provided for practical use, showcasing physical applications and comparisons with other methods. The article is structured into sections discussing definitions, the method of Olsson for analytic continuations, algorithm strategies for efficient evaluation, and demonstration of the packages with commands.
Definitions
Appell F1, F3, Lauricella F (3) D, and Lauricella-Saran F (3) S series are explored for their properties and representations.
Euler integral representations and singular loci of these functions are highlighted.
The Method of Olsson
Analytic continuations are derived using the method of Olsson, leveraging known properties of hypergeometric functions.
Symmetry relations and strategies for efficient evaluation are discussed.
Algorithm of the Packages
Strategies for selecting suitable analytic continuations, efficient summation techniques, and handling non-generic parameter values are outlined.
Demonstration of the Packages
Commands for numerical evaluation, exposing analytic continuations, finding all valid series, and visualizing regions of convergence are demonstrated for Appell F1.
Stats
"The values of Appell F1 for various points are obtained using Eq. (4) and Eq. (36). The Pochhammer parameters are a = 123/100, b1 = 234/100, b2 = 398/100, c = 47/10. The values are displayed with 20 significant digits. N is the maximum value of each index for finite summation, and t is the time in seconds for the evaluation in a typical run."
"Table of values obtained for various points obtained using Eq. (15) and Eq. (39). Pochhammer parameters used are a = 13/10, b1 = 1/5, b2 = 1/7, b3 = 1/11, c = 11/13. Values are shown up to 20 significant digits, N denotes the maximum value of each of the indices used for finite summation, and t denotes the time taken to complete the evaluation in seconds for a typical run."
Quotes
"The analytic continuations of Gauss 2F1 around x = 1 and x = ∞ are well-known."
"The hypergeometric functions have a long history of appearing in the evaluation of Feynman integrals."