David Hilditch (CENTRA, IST)
When solving general relativity numerically for a given physical problem we must use a formulation of the field equations for which the resulting partial differential equation problem is well-posed. Building such a good formulation usually requires making a coordinate choice. This leads to the standard statement that `gauge freedom in general relativity is the choice of coordinates'. The latter two facts have long bothered me, because one of the first lessons in relativity is that coordinates should in some sense not matter. In my talk I will explain the solution to my earlier confusion. Time permitting I will also describe ongoing work to exploit the solution for practical calculations.