Bifurcate Killing horizon
= Bifurcate Killing horizon
{title2=$K=\kappa(V\partial_V-U\partial_U)$}
A bifurcate Killing horizon consists of two intersecting null <Killing horizons> of the same <Killing vector field>, which vanishes on their spacelike intersection, the <bifurcation surface>. In regular Kruskal coordinates the horizons are $U=0$ and $V=0$, and their intersection is $U=V=0$. The displayed field is tangent and normal to each horizon branch and zero on the intersection.