Astrophysical and cosmological considerations on a string dilaton of a least coupling

Abstract

String-loop effects may generate very weak matter couplings for a (massless) dilaton. We examine limits on the shift of such a dilaton toward its present equilibrium value from big-bang nucleosynthesis and the binary pulsar. On the other hand, the approach of the dilaton toward its present value can be realized in the early universe in a quick and efficient way if an inflationary period is present. We comment briefly on some implications.

Comments: Revised version to appear in Astropart.Phys., numerical correction of the binary pulsar constraint. 18 pages, latex