An efficient sum of squares nonnegativity certificate for quaternary quartic

Dmitrii V. Pasechnik

For any 4-variate quartic form $f\ge 0$ (i.e. $f$ nonnegative, homogeneous polynomial of degree $4$ with real coefficients) there exist quadratic forms $q$ and $q^{\prime }$ so that $q{q}^{\prime }f$…