  We study the asymptotic behavior of the nonlinear parabolic flows
$u_{t}=F(D^2 u^m)$ when $t\ra \infty$ for $m\geq 1$, and the geometric
properties for solutions of the following elliptic nonlinear eigenvalue
problems:
  F(D^2 \vp) &+ \mu\vp^{p}=0, \quad \vp>0\quad\text{in $\Omega$}
  \vp&=0\quad\text{on $\p\Omega$} posed in a (strictly) convex and smooth
domain $\Omega\subset\re^n$ for $0< p \leq 1,$ where $F(\cdot)$ is uniformly
elliptic, positively homogeneous of order one and concave. We establish that
$\log (\vp)$ is concave in the case $p=1$ and that the function
$\vp^{\frac{1-p}{2}}$ is concave for $0<p<1.$
