micrOMEGAs5.0 : Freeze-in

Solution method: We solve the freeze-in Boltzmann equations while making as few simplifying assumptions as possible concerning the phase-space distribution of the particles involved in the dark matter production process. We include the case where dark matter is produced through the two-body decay of a particle whether or not it is in thermal equilibrium with the thermal bath as well as the one where dark matter is produced through 2→2 annihilations of a pair of bath particles. Two numerical methods are provided - one where the collision term in the Boltzmann equation is integrated directly and a more efficient one where some of the integrals are performed analytically.