Analytic progress in open string field theory

Abstract

Open string field theory provides an action functional for open string fields, and it is thus a manifestly off-shell formulation of open string theory. The solutions to the equation of motion of open string field theory are expected to describe consistent classical open string backgrounds. In this thesis, I present a number of analytic results in bosonic open string field theory. Firstly, I present analytic solutions to the equation of motion that describe an exactly marginal deformation of the chosen open string background. A prominent example in this class is the rolling-tachyon solution, which describes the decay of an unstable D-brane. Furthermore, I demonstrate that the Riemann surface geometry of string perturbation theory can be radically simplified using propagators of Schnabl gauge instead of Siegel gauge. In principle, this simplification allows the analytic computation of arbitrary off-shell one-loop open string amplitudes. Finally, I show that this simplicity of Schnabl gauge one-loop Riemann surfaces can be combined with the knowledge of analytic solutions to construct an analytically computable string field theory boundary state. For all known solutions, this boundary state precisely coincides with the BCFT boundary state of the open string background that the solution is expected to describe. This construction thus confirms the physical interpretation of known analytic solutions and thus provides a nice consistency check on open string field theory.