On conformally invariant equations on RnRn-II. Exponential invariance

In this paper we provide a complete characterization of fully nonlinear differential operators of any integer order on Rn, which exhibit conformal invariance of exponential type. In this way we intend to complete the work that we undertook in Li et al. (2011) [2], where we introduced the family of elementary conformal tensors {Tm,αu} in order to describe all fully nonlinear differential operators of any integer order on Rn which are conformally invariant of degree α≠0α≠0. Examples of the differential operators that we study in this paper are those related to the QQ–curvature equation on R4 and to the Gauss equation on R2.