  Non-thermal dark matter generation is an appealing alternative to the
standard paradigm of thermal WIMP dark matter. We reconsider non-thermal
production mechanisms in a systematic way, and develop a numerical code for
accurate computations of the dark matter relic density. We discuss in
particular scenarios with long-lived massive states decaying into dark matter
particles, appearing naturally in several beyond the standard model theories,
such as supergravity and superstring frameworks. Since non-thermal production
favors dark matter candidates with large pair annihilation rates, we analyze
the possible connection with the anomalies detected in the lepton cosmic-ray
flux by Pamela and Fermi. Concentrating on supersymmetric models, we consider
the effect of these non-standard cosmologies in selecting a preferred mass
scale for the lightest supersymmetric particle as dark matter candidate, and
the consequent impact on the interpretation of new physics discovered or
excluded at the LHC. Finally, we examine a rather predictive model, the
G2-MSSM, investigating some of the standard assumptions usually implemented in
the solution of the Boltzmann equation for the dark matter component, including
coannihilations. We question the hypothesis that kinetic equilibrium holds
along the whole phase of dark matter generation, and the validity of the
factorization usually implemented to rewrite the system of coupled Boltzmann
equation for each coannihilating species as a single equation for the sum of
all the number densities. As a byproduct we develop here a formalism to compute
the kinetic decoupling temperature in case of coannihilating particles, which
can be applied also to other particle physics frameworks, and also to standard
thermal relics within a standard cosmology.
