Sums of squares and nonnegative polynomials in multigraded rings
Presenter
December 7, 2012
Keywords:
- commutative algebra
- algebraic combinatorics
- Stanley-Reisner rings
- sums of squares
- positive polynomials
- varieties of minimal degrees
- toric varieties
- multigraded rings
MSC:
- 05-XX
- 05EXX
- 05E15
- 05E40
- 11E25
- 42A82
- 14M25
Abstract
A polynomial with real coefficients is nonnegative if it takes on only nonnegative values. For example, any sum of squares is obviously nonnegative. For a homogeneous polynomial with respect to the standard grading, Hilbert famously characterized when the converse statement hold, i.e. when every nonnegative homogeneous polynomial is a sum of squares. In this talk, we will examine this converse for homogenous polynomials with respect to a positive multigrading. In particular, we will provide many new examples in which every nonnegative homogeneous polynomial is a sum of squares.