  This Ph.D. thesis collects results obtained investigating two different
aspects of modern unifying theories. In the first part I summarized results
achieved investigating simplicial aspects of string dualities. Exploiting
Boundary Conformal Field Theory techniques, I investigated the coupling between
random Regge triangulations and open string theory, discussing its implications
in gauge/gravity correspondence. The second part reports results obtained in
the paper hep-th/0309237, devoted to look for cosmological backgrounds of
superstring theories.
