Boundary versus Bulk Dynamics of Extended Objects and the Fractal   Structure of Quantum Spacetime
  Subject of this thesis is the study of a closed bosonic string: the treatment will follow an approach alternative with respect to the traditional one and stems from a research line pursued in by Eguchi. A description of the dynamics using Nonstandard Analysis is given in chapter 10 with prerequisites in appendices B and C. Detailed calculation are carried out explicitly, although many of them are deferred to appendix A.   Selected parts of this thesis have been published as separate articles by the author (ansoldi@trieste.infn.it) and collaborators. 
Stefano Ansoldi