  In order to facilitate the application of standard renormalization
techniques, gravitation should be decribed, if possible, in pure connection
formalism, as a Yang-Mills theory of a certain spacetime group, say the
Poincare or the affine group. This embodies the translational as well as the
linear connection. However, the coframe is not the standard Yang-Mills type
gauge field of the translations, since it lacks the inhomogeneous gradient term
in the gauge transformations. By explicitly restoring the "hidden" piece
responsible for this behavior within the framework of nonlinear realizations,
the usual geometrical interpretation of the dynamical theory becomes possible,
and in addition one can avoid the metric or coframe degeneracy which would
otherwise interfere with the integrations within the path integral. We claim
that nonlinear realizations provide a general mathematical scheme clarifying
the foundations of gauge theories of spacetime symmetries. When applied to
construct the Yang-Mills theory of the affine group, tetrads become identified
with nonlinear translational connections; the anholonomic metric does not
constitute any more an independent gravitational potential, since its degrees
of freedom reveal to correspond to eliminable Goldstone bosons. This may be an
important advantage for quantization.
