OPEN INFLATIONARY UNIVERSES IN THE INDUCED GRAVITY THEORY

The induced gravity theory is a variant of Jordan-Brans-Dicke theory w here the ''dilaton'' field possesses a potential. It has the unusual f eature that in the presence of a false vacuum there is a stable static solution with the dilaton field displaced from the minimum of its pot ential, giving perfect de Sitter expansion. We demonstrate how this so lution can be used to implement the open inflationary universe scenari o. The necessary second phase of inflation after false vacuum decay by bubble nucleation is driven by the dilaton rolling from the static po int to the minimum of its potential. Because the static solution is st able whilst the false vacuum persists, the required evolution occurs f or a wide range of initial conditions. As the exterior of the bubble i s perfect de Sitter space, there is no problem with fields rolling out side the bubble, as in one of the related models considered by Linde a nd Mezhlumian, and the expansion rates before and after tunneling may be similar which prevents problematic high-amplitude supercurvature mo des from being generated. Once normalized to the microwave background anisotropies seen by the COBE satellite, the viable models form a one- parameter family for each possible Omega(0).