A+ CATEGORY SCIENTIFIC UNIT

Local theory of stable polynomials and bounded rational functions of several variables

Kelly Bickel, Greg Knese, James Eldred Pascoe, Alan Sola Annales Polonici Mathematici MSC: Primary 32A40; Secondary 13H10, 14H45 DOI: 10.4064/ap240229-9-9 Published online: 21 October 2024

Abstract

We provide detailed local descriptions of stable polynomials in terms of their homogeneous decompositions, Puiseux expansions, and transfer function realizations. We use this theory to first prove that bounded rational functions on the polydisk possess nontangential limits at every boundary point. We relate higher nontangential regularity and distinguished boundary behavior of bounded rational functions to geometric properties of the zero sets of stable polynomials via our local descriptions. For a fixed stable polynomial $p$, we analyze the ideal of numerators $q$ such that $q/p$ is bounded on the bi-upper half-plane. We completely characterize this ideal in several geometrically interesting situations including smooth points, double points, and ordinary multiple points of $p$. Finally, we analyze integrability properties of bounded rational functions and their derivatives on the bidisk.

Authors

  • Kelly BickelDepartment of Mathematics
    Bucknell University
    Lewisburg, PA 17837, USA
    e-mail
  • Greg KneseDepartment of Mathematics
    Washington University in St. Louis
    St. Louis, MO 63130, USA
    e-mail
  • James Eldred PascoeDepartment of Mathematics
    Drexel University
    Philadelphia, PA 19104, USA
    e-mail
  • Alan SolaDepartment of Mathematics
    Stockholm University
    106 91 Stockholm, Sweden
    e-mail

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