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Marginal deformations and open string field theory Longton, Matheson Edward


The study of solutions to open string field theory remains very much a work in progress, even for the bosonic string. In this dissertation I consider in detail two of these solutions involving marginal deformations of the original boundary conformal field theory. The first is a previously unknown solution in which two D-branes are translated before tachyon condensation occurs. This solution is studied in the level truncation scheme, in a sector which is larger than the universal subspace, but still less than the whole string Fock space due to several symmetries of the theory which take on a different content in the presence of two D-branes. This solution brings us a step closer to a full understanding of the relationship between the magnitude of a marginal deformation in BCFT and the strength of the corresponding marginal operator in OSFT. The other solution I study was first written down formally by Kiermaier and Okawa, and involves the renormalization of an exactly marginal operator. I consider the same solution with a more general renormalization scheme and find a set of sufficient restrictions for the solution’s validity. While this proceeds much as in the original work on this solution, I find some freedom in the solution as well as additional algebraic structure for renormalization schemes. I also present a collection of procedures written in Maple which define and manipulate wedge states with insertions, as well as computing correlation functions for such states provided that all inserted operators are sufficiently simple. Using this code I am able to calculate the tachyon profile of this solution for the time-symmetric rolling tachyon at 6th order in λ and describe its properties in comparison to previously known rolling tachyon profiles. I find the same unwanted oscillations that were seen in previous work on the time-asymmetric rolling tachyon.

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