Spontaneous dark-matter mass generation along cosmological attractors in string theory

<!--HTML-->I will talk about a new scenario for generating a relic density of non-relativistic dark matter in the framework of heterotic string theory with spontaneously broken supersymmetry and at finite temperature. In this scenario, contrary to the standard thermal freeze-out process, dark-matter particles are produced while they are still relativistic and then decouple from the thermal bath because of a sudden increase of their mass above the universe temperature. The mass increase is sourced by the destabilization of a modulus triggered when the temperature of the universe drops below the supersymmetry breaking scale. This phase transition is enforced to take place in certain models thanks to a cosmological attractor mechanism.