Hypergeometric Functions and Feynman Diagrams Mikhail Kalmykov, Vladimir Bytev, Bernd Kniehl, Sven-Olaf Moch, Bennie Ward, and Scott Yost Abstract The relationship between Feynman diagrams and hypergeometric functions is discussed. Special attention is devoted to existing techniquesfor the constructionof the Y-expansion. As an example, we present a detailed discussion of the construction of the Y-expansion of the Appell function 3 around rational values of parameters via an iterative solution of differential equations. As a by-product,we have found that the one-loop massless pentagon diagram in dimension 3 = 3 2n is not expressible in terms of multiple polylogarithms. Another interesting example− is the Puiseux-type solution involving a differential operator generated by a hypergeometric function of three variables. The holonomic properties of the # hypergeometric functions are briefly discussed. Mikhail Kalmykov JINR, Dubna, Russia, e-mail:
[email protected] Vladimir Bytev BLTP JINR, 141980 Dubna, Moscow region, Russia e-mail:
[email protected] Bernd A. Kniehl, II. Institut fuer Theoretische Physik, Universitaet Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany e-mail:
[email protected] Sven-Olaf Moch II. Institut fuer Theoretische Physik, Universitaet Hamburg, Luruper Chaussee 149, 22761 arXiv:2012.14492v3 [hep-th] 22 Jan 2021 Hamburg, Germany e-mail:
[email protected] B.F.L. Ward Department of Physics, Baylor University, One Bear Place, # 97316, Waco, TX 76798-7316, USA e- mail: BFL{\protect\relax$\@@underline{\hbox{\}}\mathsurround\z@$\relax}
[email protected] S.A. Yost Department of Physics, The Citadel, 171 Moultrie St., Charleston, SC 29409, USA e-mail:
[email protected] 1 2 Authors Suppressed Due to Excessive Length 1 Introduction Recent interest in the analytical properties of Feynman diagrams has been motivated by processes at the LHC.