I am trying to solve the following optimization problem.
$$ \max_{A} \min_{i,j,i\neq j} ||A(x_i-x_j)||_2^2 \\ \text{s.t } ||A||_F^2 <=1 $$
$A$ is a matrix and $x_i$ are given vectors. The min of convex functions is not a convex/concave function. Is there any tricks to convert it to a convex problem or an approximation of a convex problem?