The Local Validity of Special Relativity, Part 2: Matter Dynamics

In this two-part essay, we distinguish several senses in which general relativity has been regarded as “locally special relativistic”. In Part 1, we focused on senses in which a relativistic spacetime may be said to be “locally (approximately) Minkowskian”. Here, in Part 2, we consider what it might mean to say that a matter theory is “locally special relativisitc”. We isolate and evaluate three criteria in the literature and show that they are incompatible: matter theories satisfying one will generally violate others. We then consider what would happen if any of those criteria failed for a given theory.