ABSTRACT
This chapter considers a number of questions connected with the higher-derivative gravity. General covariance is the most fundamental principle of general relativity. The Einstein action which is constructed on the basis of this principle contains second derivatives of the metric. It is well-known that the quantum theory is non-renormalizable off the mass shell. A point of view exists that superstring theory gives a good possibility for a consistent discussion of quantum gravity effects. The necessary renormalization includes a nonlinear reparametrization of the fields together with a corresponding gauge transformations and a non-linear reparametrization of the ghost field together with a corresponding brst-transformations. The renormalization structure of a quantum field theory in an external gravitational field with torsion looks like the same structure for a pure metric theory.
