English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

A bad point of a positive semidefinite real polynomial f is a point at whicha pole appears in all expressions of f as a sum of squares of rationalfunctions. We show that quartic polynomials in three variables never have badpoints. We give examples of positive semidefinite polynomials with a bad pointat the origin, that are nevertheless sums of squares of formal power series,answering a question of Brumfiel. We also give an example of a positivesemidefinite polynomial in three variables with a complex bad point that is notreal, answering a question of Scheiderer.

On the bad points of positive semidefinite polynomials