Aspetti quantisitic della string field theory

In this thesis we focus on quantum aspects of string field theory. In particular, we study the foundations of string field theory and the building of off-shell amplitudes, specializing to open, closed and (fully quantum) open-closed string field theory. Special attention is devoted to the so called stub deformation, which was originally introduced as a classical field redefinition by Schnabl&Stettinger and Erbin&Firat and generalized by Maccaferri,Poletti,Ruffino&Valsesia. We extend the deformation to the quantum case with a totally general procedure and apply the formalism to closed and open-closed string field theories. We prove that stub deformation theories are indeed equivalent to the starting ones by direct computation of 1-loop amplitudes within open-closed string field theory. We give an overview on the role that stubs can play in understanding the singular limits of open-closed string field theory.