Translating solutions to the Gauss curvature flow with flat sides
  We derive local $C^{2}$ estimates for complete non-compact translating solitons of the Gauss curvature flow in $\mathbb{R}^3$ which are graphs over a convex domain $\Omega$. This is closely is related to deriving local $C^{1,1}$ estimates for the degenerate Monge-Amp\'ere equation. As a result, given a weakly convex bounded domain $\Omega$, we establish the existence of a $C^{1,1}_{\text{loc}}$ translating soliton. In particular, when the boundary $\partial \Omega$ has a line segment, we show the existence of flat sides of the translator from a local a'priori non-degeneracy estimate near the free-boundary. 
Kyeongsu Choi, Panagiota Daskalopoulos, Ki-Ahm Lee
math.DG