Harmonic functions for Bessel operators

Abstract We establish the boundedness of the Riesz transform from the Hardy space associated with the operator to the Lebesgue space $$L^1$$ L 1 of integrable functions. For the standard Euclidean Laplace operator, this is a classical result that plays a significant role in harmonic analysis and theory of singular integral operators. Here, we consider a one-dimensional model of manifolds with ends and exterior Dirichlet boundary conditions. This setting extends the work of Hassell and the third author. Specifically, we examine the real line with the measure $$|x|^{d-1}dx$$ | x | d - 1 d x leading to various versions of Bessel operators. For integer d , this mimics the measure on Euclidean d -dimensional space and the obtained results are expected to provide good predictions for a class of Riemannian manifolds with Euclidean ends.