Dilaton dominance in the early Universe dilutes Dark Matter relic abundances

Understand

The role of the dilaton field and its coupling to matter may result to a dilution of Dark Matter (DM) relic densities.

• This is to be contrasted with quintessence scenarios in which relic densities are augmented, due to modification of the expansion rate, since Universe is not radiation dominated at DM decoupling.
• Dilaton field, besides this, affects relic densities through its coupling to dust which tends to decrease relic abundances.
• Thus two separate mechanisms compete each other resulting, in general, to a decrease of the relic density.