“…Traditional description of black holes in terms of event horizons is inadequate for the expected observational data. For non-stationary spacetimes, quasi-local notions of trapped and marginal surfaces have now been found to be more useful within the framework of isolated, and dynamical trapping horizons [2,3,4,5,6,7,8]. These frameworks enable one to significantly extend the laws of black hole mechanics to the dynamical regime with the associated notions of energy, angular momentum and their fluxes, and have been applied to several problems in mathematical general relativity, numerical relativity, and quantum gravity [9].…”