DILATONIC DARK-MATTER AND UNIFIED COSMOLOGY - A NEW PARADIGM

We study the possibility that the dilaton--the fundamental scalar fiel d which exists in all existing unified field theories--plays the role of the dark matter of the universe. We End that the condition for the dilaton to be the dark matter strongly restricts its mass to be around 0.5 keV or 270 MeV. For the other mass ranges, the dilaton either und ercloses or overdoses the universe. The 0.5 keV dilaton has a free-str eaming distance of about 1.4 Mpc and becomes an excellent candidate fo r warm dark matter, while the 270 MeV one has a free-streaming distanc e of about 7.4 pc and becomes cold dark matter. We discuss the possibl e ways to detect the dilaton experimentally.