NONLINEAR 4D CONFORMAL GAUGE SPACETIME SYMMETRY

The nonlinear local theory of the 4D conformal spacetime group is pres ented. Effective theories of gravity quadratic in curvatures may be vi ewed as nonlinear realizations of this group. We find that in the abse nce of torsion and under very general assumptions derived from the str ucture of the algebra, the symmetry takes the form of the simpler Weyl scale invariance and the resulting theory is Einstein's gravity with, generally, a cosmological constant.