Blenders
arXiv:1008.4533
Abstract
A blender is a closed convex cone of real homogeneous polynomials that is also closed under linear changes of variable. Non-trivial blenders only occur in even degree. Examples include the cones of psd forms, sos forms, convex forms and sums of -th powers of forms of degree . We present some general properties of blenders and analyze the extremal elements of some specific blenders.
Revised version; will appear in "Notions of Positivity and the Geometry of Polynomials" (P. Branden, M. Passare, M. Putinar, editors), Trends in Math., Birkhauser, Basel