To clarify all your doubts about the concave lens and convex lens, students can read this article. Here, the difference between a concave lens and a convex lens has been discussed in detail.

In this paper we are concerned with the problem of finding the global minimum of a concave function over a closed, convex, possibly unbounded set in R n. The intrinsic difficulty of this problem is ...

The classical one-sector problem of optimal growth theory over an infinite horizon in continuous times with a convex-concave production function is studied. Consumption and investment are subject to ...