  The dark energy dominated warm dark matter (WDM) model is a promising
alternative cosmological scenario. We explore large-scale structure formation
in this paradigm. We do this in two different ways: with the halo model
approach and with the help of an ensemble of high resolution N-body
simulations. Combining these quasi-independent approaches, leads to a physical
understanding of the important processes which shape the formation of
structures. We take a detailed look at the halo mass function, the
concentrations and the linear halo bias of WDM. In all cases we find
interesting deviations with respect to CDM. In particular, the
concentration-mass relation displays a turnover for group scale dark matter
haloes, for the case of WDM particles with masses of the order ~0.25 keV. This
may be interpreted as a hint for top-down structure formation on small scales.
We implement our results into the halo model and find much better agreement
with simulations. On small scales the WDM halo model now performs as well as
its CDM counterpart.
