Constraints on Gravitation from Causality and Quantum Consistency

Understand

We examine the role of consistency with causality and quantum mechanics in determining the properties of gravitation.

• We begin by examining two different classes of interacting theories of massless spin 2 particles -- gravitons.
• One involves coupling the graviton with the lowest number of derivatives to matter, the other involves coupling the graviton with higher derivatives to matter, making use of the linearized Riemann tensor.
• The first class requires an infinite tower of terms for consistency, which is known to lead uniquely to general relativity.