We study the index of N=4 Yang-Mills theory on
S3×R at large angular momenta. A generalized Cardy limit
exhibits macroscopic entropy at large N. Our result is derived using free QFT
analysis, and also a background field method on S3. The index sets a lower
bound on the entropy. It saturates the Bekenstein-Hawking entropy of known
supersymmetric AdS5 black holes, thus accounting for their microstates. We
further analyze the so-called Macdonald index, exploring small black holes and
possibly new black holes reminiscent of hairy black holes. Finally, we study
aspects of large supersymmetric AdS7 black holes, using background field
method on S5 and 't Hooft anomalies.Comment: 54 pages, 10 figure