English

An inductive Julia-Caratheodory theorem for Pick functions in two variables

Complex Variables 2016-05-30 v1 Functional Analysis

Abstract

We study the asymptotic behavior of Pick functions, analytic functions which take the upper half plane to itself. We show that if a two variable Pick function ff has real residues to order 2N12N-1 at infinity and the imaginary part of the remainder between ff and this expansion is of order 2N+1,2N+1, then ff has real residues to order 2N2N and directional residues to order 2N+1.2N+1. Furthermore, ff has real residues to order 2N+12N+1 if and only if the 2N+12N+1-th derivative is given by a polynomial, thus obtaining a two variable analogue of a higher order Julia-Carath\'eodory type theorem.

Keywords

Cite

@article{arxiv.1605.08707,
  title  = {An inductive Julia-Caratheodory theorem for Pick functions in two variables},
  author = {J. E. Pascoe},
  journal= {arXiv preprint arXiv:1605.08707},
  year   = {2016}
}
R2 v1 2026-06-22T14:11:26.279Z