 The status of these competing definitions of a quasi-local black hole and of the differences among them, and what their respective virtues and demerits may be, appear to be open questions, though both Hayward and Ashtekar et al., in the works just cited, go some way towards answering some of them by using their respective definitions to prove generalizations of the so-called laws of black hole mechanics  (section 5.1  below). Hayward also demonstrates that analogues to some of the classical singularity theorems hold for his definition as well. Still, many questions remain open. To take one example, it is not clear whether or not the new definitions coincide with the traditional definition in those spacetimes in which the traditional definition can be formulated, or whether collateral conditions must be met for the two to coincide. It is also not clear whether the analogues to the classical No Hair Theorems hold using the new definitions or even what those analogues may be. 