$C^\infty$ local solutions of elliptical $2-$Hessian equation in   $\mathbb{R}^3$
  In this work, we study the existence of $C^{\infty}$ local solutions to $2$-Hessian equation in $\mathbb{R}^{3}$. We consider the case that the right hand side function $f$ possibly vanishes, changes the sign, is positively or negatively defined. We also give the convexities of solutions which are related with the annulation or the sign of right-hand side function $f$. The associated linearized operator are uniformly elliptic. 
Guiji Tian, Qi Wang, Chao-Jiang Xu (LMRS)
math.AP