Singular gauge transformations in string field theory

Abstract

We show that the existence of a tachyon vacuum puts tight restrictions on the form of solutions to the equations of motion of string field theory. In particular, we demonstrate that every solution can be written as a – formal – gauge transformation of the tachyon vacuum. In order for a solution to be non-trivial, this gauge transformation must be singular and we argue that this will happen when the gauge transformation annihilates a projector of the star-algebra. We comment on possible applications of the formalism to finding new solutions. Contents 1