In one dimension, this equals -1/r^2 for r < 0 and 1/r^2 for r > 0. So this is neither convex nor concave. Things don;t get any better in higher dimensions.
In one dimension, this equals -1/r^2 for r < 0 and 1/r^2 for r > 0. So this is neither convex nor concave. Things don;t get any better in higher dimensions.