Note on Artin’s solution of Hilbert’s 17th problem
Note on Artin’s solution of Hilbert’s 17th problem
A uniquely orderable field F and a polynomial ƒ (X) over F are constructed in such a manner that ƒ(X), though positive at every point of F, is not a sum of squares of elements of the rational function field F(X).Artin's solution of Hubert's problem asserts [2] that if a …