2 papers
math.OC2015
Spectrahedra and Convex Hulls of Rank-One Elements
Martin Ames Harrison
The Helton-Nie Conjecture (HNC) is the proposition that every convex semialgebraic set is a spectrahedral shadow. Here we prove that HNC is equivalent to another propo- sition rela…
math.RA2011
Pfister's theorem fails in the free case
Martin Harrison
Artin solved Hilbert's problem by showing that every positive semidefinite polynomial can be realized as a sum of squares of rational functions. Pfister gave a bound on t…