On multiple positive ground state solutions for a mean curvature   equation in Minkowski space
  In this paper, we show how changes in the sign of nonlinearity leads to multiple radial ground state solutions of the mean curvature equation $ \nabla\cdot \Big[\frac{\nabla u}{\sqrt{1-|\nabla u|^2}}\Big] +\lambda f(u)=0\ \ \text{in} \ \mathbb{R}^N $ for sufficiently large $\lambda$ with $N\geq 2$. 
Ruyun Ma, Yanqiong Lu, Tianlan Chen
math.AP