1/16-BPS Black Holes and Giant Gravitons in the AdS_5 X S^5 Space

We explore 1/16-BPS objects of type IIB string theory in AdS_5 * S^5. First, we consider supersymmetric AdS_5 black holes, which should be 1/16-BPS and have a characteristic that not all physical charges are independent. We point out that the Bekenstein-Hawking entropy of these black holes admits a remarkably simple expression in terms of (dependent) physical charges, which suggests its microscopic origin via certain Cardy or Hardy-Ramanujan formula. We also note that there is an upper bound for the angular momenta given by the electric charges. Second, we construct a class of 1/16-BPS giant graviton solutions in AdS_5 * S^5 and explore their properties. The solutions are given by the intersections of AdS_5 * S^5 and complex 3 dimensional holomorphic hyperspaces in C^{1+5}, the latter being the zero loci of three holomorphic functions which are homogeneous with suitable weights on coordinates. We investigate examples of giant gravitons, including their degenerations to tensionless strings.