 Again, all these questions are of great interest in their own right in physics, but there is strong reason to believe that their analysis may shed new light on several ongoing philosophical discussions about the nature of spacetime, with which they have obvious direct connections, especially concerning the dimensionality of space and spacetime, and the substantivalism-versus-relationalism debate. The interested reader should see de Haro et al. (2015) for a discussion of the relation of holography to gauge/gravity dualities in general, and a review of the philosophical issues that raises, and Castellani (2016) for philosophical discussion of the ontological issues raised by these dualities. 