A compactness theorem for a fully nonlinear Yamabe problem under a lower Ricci curvature bound

We prove compactness of solutions of a fully nonlinear Yamabe problem satisfying a lower Ricci curvature bound, when the manifold is not conformally diffeomorphic to the standard sphere. This allows us to prove the existence of solutions when the associated cone Γ satisfies μΓ+⩽1, which includes the σk-Yamabe problem for k not smaller than half of the dimension of the manifold.