Outline of a generally covariant quantum field theory and a quantum theory of gravity

We study a tentative generally covariant quantum field theory, denoted the T theory, as a tool to investigate the consistency of quantum general relativity. The theory describes the gravitational field and a minimally coupled scalar field; it is based on the loop representation, and on a certain number of quantization choices. Four-dimensional diffeomorphism-invariant quantum transition probabilities can be computed from the theory. We discuss the choices on which the T theory relies, and the possibilities of modifying them.