An action inspired on the low-energy effective action for heterotic string
and Weyl integrable space-time theory is used to describe the radiation era
in scalar-tenser cosmology. The resulting field equations for a Friedmann-
Robertson-Walker geometry are written and the general solution for this sys
tem is obtained and its main properties are discussed. (C) 2000 Published b
y Elsevier Science B.V. All rights reserved.