  We derive the luminosity-temperature relation for clusters of galaxies by
means of a modification of the self-similar model to take account of angular
momentum acquisition by protostructures and of an external pressure term in the
virial theorem. The fundamental result of the model is that gravitational
collapse, which takes account of angular momentum acquisition, can explain the
non self-similarity in the L-T relation, in disagreement with the largely
accepted assumption that heating/cooling processes and similar are fundamental
in the originating the non-self similar behavior (shaping) of the L-T relation.
