  Real Space Renormalization Group (RSRG) techniques and their applications,
mainly to quantum mechanics and to partial differential equations, are
discussed. Special emphasis is given to the theoretical insight and the reasons
for the success of some techniques, specially DMRG. Applications to the
spectrum of dendrimers and excitons on random media are considered. This work
is the Ph.D. of the author. Almost all the results have already been published.
The main interest of this text is paedagogical and as a review.
