paper

Polya-Schur master theorems for circular domains and their boundaries

arXiv:math/0607416 · doi:10.4007/annals.2009.170.465

Abstract

We characterize all linear operators on finite or infinite-dimensional polynomial spaces that preserve the property of having the zero set inside a prescribed region for arbitrary closed circular domains (i.e., images of the closed unit disk under a Möbius transformation) and their boundaries. This provides a natural framework for dealing with several long-standing fundamental problems, which we solve in a unified way. In particular, for our results settle open questions that go back to Laguerre and Pólya-Schur.

Final version, to appear in Ann. of Math.; 23 pages, no figures, LaTeX2e

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