Acknowledgements

This whole doctoral experience came unpredicted like the best things in everybody's life.

In the first two years I discovered the joy of research and theoretical speculation and I still remember vividly the moment in which I could go behind that reserved door of the faculty’s library and crawl personally through such an impressive repository of knowledge. It really felt like ‘standing on the shoulders of giants’.

Along with the last year I progressively started feeling the need for that ‘innovative’ contribution that had, until then, failed to materialize as some of the expectations from a few connections I had established.

Again it was with surprise, in the blink of an eye, that I discovered within me the idea that relieved that rising pressure and ultimately led to this document.

For all this I’m really grateful to Enrico De Angelis, who suggested me to enroll in the doctorate and then – becoming my tutor – allowed me to explore and research in several different directions, always providing wise and useful suggestions and references.

I’m also thankful to Prof. Bruno Daniotti who provided his help in a crucial moment and of course to Prof. Pietro Natale Maggi and Prof. Sergio Croce, who shaped the doctorate during these years.

I also wish to thank Gloria, who in the meantime has become my wife, and who is and will be the most unpredictable gift.