Abstract:
Invariance under the infinite-parameter generally covariant group is equivalent to simultaneous
invariance under the affine and the conformal group. A nonlinear realization of the
affine group (with linearization on the poincar6 group) leads to a symmetric tensor field as
Goldstone field. The requirement that the theory correspond simultaneously to a realization
of the conformal group as well leads uniquely to the theory of a tensor field whose equations
are Einstein's. This shows that the theory of the gravitational field is the theory of spontaneous
breaking of affine and conformal symmetries in the same way as chiral dynamics is the theory of spontaneous breaking of chiral symmetry. This analogy brings out new aspects of the role of gravitation in the theory of elementary particles.