Cosmological consequences of gravitationally interacting Planck-mass particles

The existence of Planck-mass particles (called geons) in pure gravity is suggested by the work of Friedman and Sorkin. These particles are very peculiar in the sense that they interact only gravitationally. In this paper we show that the existence of Planck-mass unstable geons may have many physically interesting implications. In particular we propose a scenario in which we show the possibility of formation of heavy black holes (with present number density equal to the galactic number density) which will have the capability of providing seeds for the galaxy formation. In this scenario lighter black holes provide the missing mass in the galactic halos. Also in this scenario the early geon-dominated era dilutes grand-unified-theory monopoles sufficiently providing a noninflationary solution to the monopole problem. Unfortunately, however, this scenario is in conflict with the standard calculations of helium synthesis and baryon excess. A scenario consistent with helium synthesis is briefly discussed.