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Abstract

In this work we review Schnabl's construction of the tachyon vacuum solution to bosonic covariant open string field theory and the results that followed. We survey the state of the art of string field theory research preceding this construction focusing on Sen's conjectures and the results obtained using level truncation methods. The tachyon vacuum solution is described in various ways, in particular we describe its geometric representation using wedge states and its formal algebraic representation as a gauge solution. We also derive the form of the solution's building blocks in the oscillator representation. We show that some of Sen's conjectures can be proven analytically using this solution. The tools used in the context of the vacuum solution can be adapted to the construction of other solutions, namely various marginal deformations. We present some of the approaches used in the construction of these solutions. The generalization to open superstring field theory is derived in details. We start from the exposition of the problems one faces in the construction of superstring field theory. We then present the cubic and the non-polynomial versions of superstring field theory and prove their classical equivalence. Finally, the bosonic solutions are generalized to this case. In particular we focus on the (somewhat surprising) generalization of the tachyon solution to the case of a theory with no tachyons.