  Angular tension is an ADM charge that contributes a work term to the first
law of black hole mechanics when the range of an angular coordinate is varied
and leads to a new Smarr formula for stationary black holes. A phase diagram
for singly-spinning D=5 black holes shows that angular tension resolves the
degeneracies between spherical black holes and (dipole) black rings and
captures the physics of the black ring balance condition. Angular tension
depends on the behavior of the metric at rotational axes and we speculate on
its relation to rod/domain structure characterizations of higher dimensional
black holes and black hole uniqueness theorems.
