The Bessel Period Functional on SO(5): The Nontempered Case

Abstract: For automorphic representations in the nontempered cuspidal spectrum of $\mathrm{SO}_5$, we prove the refined Gan-Gross-Prasad conjecture by establishing a precise Bessel period formula, in which the square of the global Bessel period is expressed as an Euler product of regularized local Bessel period integrals of matrix coefficients.