Dynamics of Myers-Perry black holes with almost equal angular momenta in odd dimensions

We investigate the nonlinear dynamics of D = 2N + 3 Myers-Perry black holes with almost equal angular momenta, which have N equal spins out of possible N + 1 spins. In particular, we study the ultraspinning instability and the fate of its nonlinear evolution using the large D effective theory approach. We find that every stationary phase can be mapped to the counterpart in the singly rotating phase within the leading order effective theory. From the known results of singly rotating solutions, we obtain the phase diagram of almost equally rotating black holes. We also obtain a certain implication for the possible topology changing transition.