MEMBRANE PREGEOMETRY AND THE VANISHING OF THE COSMOLOGICAL CONSTANT

We suggest a model of induced gravity in which the fundamental object is a relativistic membrane minimally coupled to a background metric and to an external three-index gauge potential. We compute the low-energy limit of the two-loop effective action as a power expansion in the surface tension. A generalized bootstrap hypothesis is made in order to identify the physical metric and gauge field with the lowest-order terms in the expansion of the vacuum average of the composite operators conjugate to the background fields. We find that the large-distance behaviour of these classical fields is described by the Einstein action with a cosmological term plus a Maxwell-type action for the gauge potential. The Maxwell term enables us to apply the Hawking-Baum argument to show that the physical cosmological constant is `probably' zero.