Interior $C^2$ Estimates for 2-Sum Hessian Equations

C. Y. Ren, X. L. Sun

This paper establishes an interior $C^2$ estimate for solutions of \[ σ_2(D^2u)+α(x)σ_1(D^2u)=f(x,u,Du)>0, \] on the positive branch $\Delta u>0$, under the assumptions $\alpha \ge 0$ and $D^2α…