Nicolò Drago (Trento)
Oliver Lindblad Petersen
We recall the Hamiltonian formulation of Einstein's vacuum equation and explain the exact meaning of the lapse function and the shift vector. In this form, Einstein's equation can be seen as a flow on the space of initial data. We discuss the relation to the classical linearisation stability results and conclude with some remarks on the meaning of "gauge invariance" in this setting.