Pregeometry

This chapter attempts to find physical phenomena which can occur in pregeometry but not in Einstein's geometrical picture of gravitation. Pregeometry is defined as a fundamental theory from which Einstein's theory of gravitation is derived as an effective theory at low energies. Phenomena such as phase transitions of the space-time between the ''geometric phase'' and the ''pregeometric one'' are discussed. The temperature-dependent effective action for gravity in pregeometry is calculated, and it is determined that the effective potential for the space-time metric is minimum at the origin for extremely high temperature. It is proposed that the origin of the big bang of the Universe is a local and spontaneous phase transition from the pregeometric phase to the geometric one in the overcooled space-time manifold. It is further suggested that even in the present Universe there may exist ''pregeometric holes'' where the space-time metric absolutely vanishes (diverges) and/or ''space-time discontinuities'' where the metric discretely changes. Pregeometry in the limit of zero temperature is examined. Includes a table