Projective null twistor space
= Projective null twistor space
{title2=$PN=\{[Z]\in\mathbb{CP}^3:h(Z,Z)=0\}$}
The five-real-dimensional space of projective <null twistors>. A projective line lies entirely in it precisely when its corresponding two-plane is totally isotropic for the <twistor Hermitian form>. Such lines represent real points of <Minkowski conformal compactification>. Two independent null twistors lie on one such line exactly when $h(X,Y)=0$.