Dark Matter from Entropy Perturbations in Curved Field Space

Understand

The accumulated energy density of the excited entropy modes in multiple field inflationary scenarios can play the role of dark matter.

• In the usual case of a flat field space without any turning trajectory, only light superhorizon entropy modes can be excited through the gravitational instability.
• In the case of a negatively curved field space, we show that subhorizon entropy modes can be excited as well through the tachyonic instability induced by the negative curvature of the field space.
• The latter allows for production of entropy modes with masses larger than or at the order of the Hubble expansion rate during inflation, leading to a new dark matter scenario.