Kolloquien und Oberseminare Übersicht Detail

Vortragende Person/Vortragende Personen:
Olivier Benoist

A bad point of a positive semidefinite polynomial is a point at which a pole appears in all its possible representations as sums of squares of rational functions. We will give an example of a positive semidefinite polynomial in three variables for which the origin is a bad point, but which is however a sums of squares of formal power series. We will also give an example of a positive semidefinite polynomial in three variables with a complex bad point. These examples provide answers to questions of Brumfiel and Scheiderer.