A unique theory of gravity and matter

The author has previously suggested that the ground state for 4-dimensional quantum gravity can be represented as a condensation of non-linear gravitons connected by Dirac strings. In this note we suggest that the low-lying excitations of this state can be described by a quasi-topological action of the form integral d(13)z F-4 boolean AND F-5 boolean AND F-4, corresponding to a trilinear coupling of solilonic 8-branes and 7-branes. It is shown that when the excitations associated with F-5 are neglected, the effective action can be interpreted as a theory of conformal gravity in four dimensions. This in turn suggests that ordinary gravity as well supersymmetric matter and phenomenological gauge symmetries arise from the spontaneous breaking of topological invariance. The possibly deep mathematical significance of this theory is also noted. (C) 1999 Elsevier Science Ltd. All rights reserved.