Ambient metric construction of $Q$-curvature in conformal and CR geometries

Charles Fefferman, Kengo Hirachi
2003 Mathematical Research Letters  
We give a geometric derivation of Branson's Q-curvature in terms of the ambient metric associated with conformal structures; it naturally follows from the ambient metric construction of conformally invariant operators and can be applied to a large class of invariant operators. This procedure can be also applied to CR geometry and gives a CR analog of the Q-curvature; it then turns out that the Q-curvature gives the coefficient of the logarithmic singularity of the Szego kernel of 3-dimensional
more » ... l of 3-dimensional CR manifolds.
doi:10.4310/mrl.2003.v10.n6.a9 fatcat:bxggzzqbevc4pjrqaes23acs7e