Necessitating Spacetime

Abstract

We investigate structure that describes physical data in gravitational systems that is, to one degree or another, independent of the metric and affine structure. We dub such structure surplus structure and seek to incorporate it into our ontological commitments. An emphasis is placed on those structures which are required to constrain our models motivated by physical data. We look at the fall-offs of the gauge fields in asymptotically flat spacetimes, the computation of entanglement entropies in the AdS/CFT correspondence, and the addition of arbitrary parameters which modify the causal structure of spacetime in Kruskal coordinates. We also present a historical overview of the understanding of singularities in classical gravitation. Primary sources are turned to here. A toy cosmological model is also explored in which global topology is determined by an additional function which we prescribe as a dynamical $\Lambda$. Such surplus structure is classified using the language of intermediaries and positioned within the system of a shifting-scale ontology as introduced in prior work.