Extensions of Watson's theorem and the Ramanujan-Guinand formula

Abstract

Ramanujan provided several results involving the modified Bessel function Kz(x) in his Lost Notebook. One of them is the famous Ramanujan-Guinand formula, equivalent to the functional equation of the non-holomorphic Eiesenstien series on SL2(z). Recently, this formula was generalized by Dixit, Kesarwani, and Moll. In this article, we first obtain a generalization of a theorem of Watson and, as an application of it, give a new proof of the result of Dixit, Kesarwani, and Moll. Watson’s theorem is also generalized in a different direction using µKz(x, λ) which is itself a generalization of Kz(x). Analytic continuation of all these results are also given.