Gravity and Gauge

Philosophers of physics and physicists have long been intrigued by the analogies and disanalogies between gravitational theories and (Yang-Mills-type) gauge theories. Indeed, repeated attempts to collapse these disanalogies have made us acutely aware that there are fairly general obstacles to doing so. Nonetheless, there is a special case (viz. that of (2+1) spacetime dimensions) in which gravity is often claimed to be identical to a gauge theory. We subject this claim to philosophical scrutiny in this paper: in particular, we (i) analyze how the standard disanalogies can be overcome in (2+1) dimensions, and (ii) consider whether (i) really licenses the interpretation of (2+1) gravity as a gauge theory. Our conceptual analysis reveals more subtle disanalogies between gravity and gauge, and connects these to interpretive issues in classical and quantum gravity.\u