deals with the most relevant string model in the framework of the gauge/gravity duality -one of the most farreaching recent ideas in theoretical physics. This work is in my opinion remarkable for three aspects. First, it contains some of the technically hardest calculations in this framework (next-to-leading order results for string excitations which are highly coupled, as well as next-to-next-to-leading order results, the last one setting the current limit of perturbative string world-sheet analysis). Second, it contains the results of a new, highly interdisciplinary project -involving various themes in mathematical and high-energy physics -which initiates an entirely new way to analyze worldsheet string theory models: the use of Monte Carlo simulations for their lattice-discretized version. Finally, the thesis is very well written and highly pedagogical, thus enabling the reader to follow easily (and I believe with pleasure) the complex subjects treated and the analytic and numerical results reported.