String field theory at large B-field and noncommutative geometry

In the search for the exact minimum of the tachyon potential in the Witten's cubic string field theory we try to learn as much as possible from the string field theory in the large B-field background. We offer a simple alternative proof of the Witten's factorization, carry out the analysis of string field equations also for the noncommutative torus and find some novel relations to the algebraic K-theory. We note an intriguing relation between Chern-Simons and Chern classes of two noncommutative bundles. Finally we observe a certain pattern which enables us to make a plausible conjecture about the exact form of the minimum.Comment: 12 pages, JHEP style, v2: minor corrections, reference added, v3: few typos in formulas correcte

On Multibrane Solutions in Open String Field Theory

Existence of open string field theory solutions describing configurations of multiple space-filling D-branes has been a subject of numerous speculations for quite some time. In this talk we present some new results giving further support to these ideas.Comment: 8 pages. Contribution to the proceedings of the 3rd International Conference on String Field Theory and Related Aspects (SFT 2010), Kyoto, Japan, 18-22 Oct 201

Large BCFT moduli in open string field theory

We use the recently constructed solution for marginal deformations by one of the authors, to analytically relate the BCFT modulus (lambda_BCFT) to the coefficient of the boundary marginal field in the solution (lambda_SFT). We explicitly find that the relation is not one to one and the same value of lambda_SFT corresponds to a pair of different lambda_BCFT 's: a "small" one, and a "large" one. The BCFT moduli space is fully covered, but the coefficient of the marginal field in the solution is not a good global coordinate on such a space.Comment: 14 pages, 3 figures. v2: minor notation improvements, version published in JHE

Analytic solution for tachyon condensation in open string field theory

We propose a new basis in Witten's open string field theory, in which the star product simplifies considerably. For a convenient choice of gauge the classical string field equation of motion yields straightforwardly an exact analytic solution that represents the nonperturbative tachyon vacuum. The solution is given in terms of Bernoulli numbers and the equation of motion can be viewed as novel Euler--Ramanujan-type identity. It turns out that the solution is the Euler--Maclaurin asymptotic expansion of a sum over wedge states with certain insertions. This new form is fully regular from the point of view of level truncation. By computing the energy difference between the perturbative and nonperturbative vacua, we prove analytically Sen's first conjecture.Comment: 60 pages, 4 figures, v2: typos corrected, references adde

Constraints on the tachyon condensate from anomalous symmetries

Using anomalous symmetries of the cubic string field theory vertex we derive set of relations between the coefficients of the tachyon condensate. They are in agreement with the results obtained from level truncation approximation.Comment: 6 page

Anomalous reparametrizations and butterfly states in string field theory

The reparametrization symmetries of Witten's vertex in ordinary or vacuum string field theories can be used to extract useful information about classical solutions of the equations of motion corresponding to D-branes. It follows, that the vacuum string field theory in general has to be regularized. For the regularization recently considered by Gaiotto et al., we show that the identities we derive, are so constraining, that among all surface states they uniquely select the simplest butterfly projector discovered numerically by those authors. The reparametrization symmetries are also used to give a simple proof that the butterfly states and their generalizations are indeed projectors.Comment: 37 pages, 4 figures, v2: numerical factors in section 2.3 and Appendix C corrected, report number correcte