### Hyperbolic polynomials, interlacers and sums of squares

Plaumann, D *(Universität Konstanz)*

Friday 19 July 2013, 09:30-10:00

Seminar Room 1, Newton Institute

#### Abstract

A real polynomial is hyperbolic if it defines a hypersurface consisting of maximally nested ovaloids. These polynomials appear in many areas of mathematics, including convex optimisation, combinatorics and differential equations. We investigate the relation between a hyperbolic polynomial and the set of polynomials that interlace it. This set of interlacers is a convex cone, which we realize as a linear slice of the cone of nonnegative polynomials. We combine this with a sums-of-squares-relaxation to approximate a hyperbolicity cone explicitly by the projection of a spectrahdedron. A multiaffine example coming from the Vámos matroid shows that this relaxation is not always exact.

#### Presentation

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