Open String Field Research Articles

Mapping between Witten and lightcone string field theories

We propose a transformation between the off-shell field variables of Witten’s open bosonic string field theory and the traditional lightcone string field theory of Kaku and Kikkawa, based on Mandelstam’s interacting string picture. This is accomplished by deforming the Witten vertex into lightcone cubic and quartic vertices, followed by integrating out the ghost and lightcone oscillator excitations from the string field. Surprisingly, the last step does not alter the cubic and quartic interactions and does not generate effective vertices, and leads precisely to Kaku and Kikkawa’s lightcone string field theory.

Open string fields as matrices

We show that the action expanded around Erler-Maccaferri's N D-brane solution describes the N+1 D-brane system where one D-brane disappears due to tachyon condensation. String fields on multi-branes can be regarded as block matrices of a string field on a single D-brane in the same way as matrix theories.

Application of KBc Subalgebra in String Field Theory

Recently, a classical solution of open cubic string field theory (CSFT) which corresponds to the closed string vacuum is found by Erler and Schnabl. In their work, a very simple subalgebra of open string star algebra — called KBc subalgebra — plays a crucial role. In this talk, we demonstrate two applications of the KBc subalgebra. One is evaluation of classical and effective tachyon potential. It turns out that the level expansion in the KBc subalgebra terminates at a certain level, so that analytic evaluation of effective potential is available. The other application is regularization of the identity based solutions. It is demonstrated that the Okawa-Erler-Schnabl type solution naturally includes gauge invariant regularization of identity based solutions.

Comments on regularization of identity based solutions in string field theory

We analyze the consistency of the recently proposed regularization of an identity based solution in open bosonic string field theory. We show that the equation of motion is satisfied when it is contracted with the regularized solution itself. Additionally, we propose a similar regularization of an identity based solution in the modified cubic superstring field theory.

Taming open/closed string duality with a Losev trick

A target space string field theory formulation for open and closed B-model is provided by giving a Batalin-Vilkovisky quantization of the holomorphic Chern-Simons theory with off-shell gravity background. The target space expression for the coefficients of the holomorphic anomaly equation for open strings are obtained. Furthermore, open/closed string duality is proved from a judicious integration over the open string fields. In particular, by restriction to the case of independence on continuous open moduli, the shift formulas of [8] are reproduced and shown therefore to encode the data of a closed string dual.

Exact Solutions in SFT and Marginal Deformation in BCFT

In this note we will study solution of open bosonic string field theory based on action of operators from chiral algebra of boundary conformal field theory on identity element of string field theory star algebra. We will demonstrate that the string field theory action for fluctuation fields around this classical solution can be mapped to the string field theory action defined through the new boundary conformal field theory that arises from the original one through the marginal deformation inserted on the world-sheet boundary.

Tachyon Matter

It is shown that classical decay of unstable D-branes in bosonic and superstring theories produces pressureless gas with non-zero energy density. The energy density is stored in the open string fields, even though around the minimum of the tachyon potential there are no open string degrees of freedom. We also give a description of this phenomenon in an effective field theory.

Exact Solutions of Open Bosonic String Field Theory

In this paper we present two solutions of open bosonic string field theory defined on D0-brane background that correspond to the change of the D0-brane position in the transverse space.

Tachyon condensation and open string field theory

We perform canonical quantization of the open string on a unstable D-brane in the background of the tachyon condensation. Evaluating the Polyakov path-integral on a stripe, we obtain the field theoretical propagator in the open string theory. As the condensation occurs the string field theory is continuously deformed. At the infrared fixed point of the condensation, the open string field on the unstable D-brane transmutes to that on the lower dimensional D-brane with the correct D-brane tension.

Transformation of the Dirac–Born–Infeld action under the Seiberg–Witten map

We explicitly evaluate the disk S-matrix elements of one closed string and an arbitrary number of open string states in the presence of a large background B-flux. From this calculation, we show that in the world-volume action of D-branes in terms of non-commutative fields, the closed string fields must be treated as functionals of the non-commutative gauge fields. We also find the generalized multiplication rule *_N between N open string fields on the world-volume of the D-brane. In particular, this result indicates that the difference between the familiar * and the *_N product is just some total derivative terms. We show that the *_N product and the dependence of the closed string fields on the non-commutative gauge fields emerge also from transforming the ordinary Dirac-Born-Infeld action(including the closed string fields) under the Seiberg-Witten map. We then conjecture a non-commutative DBI action for the transformation of the commutative DBI action under the SW map.

Test of Siegel gauge for the lump solution

We test the validity of the Siegel gauge condition for the lump solution of cubic open bosonic string field theory by checking the equations of motion of the string field components outside the Siegel gauge. At level (3,6) approximation, the linear and quadratic terms of the equations of motion of these fields are found to cancel within about 20%.

Action principle for subcritical string fields

We consider the problem of constructing multiloop amplitudes for open string dual resonance models in space-time dimension D less than 26. These amplitudes are constructed so that open string unitarity is automatic. For general subcritical dimension, we show to remove redundant states by including an extra scalar world-sheet field (the free field incarnation of the Liouville degree of freedom) to make the BRST charge nilpotent, and the constructing a vertex function invariant under this modified charge. We prove the existence and uniqueness of this modified vertex for D<25. Although explicit calculations beyond one loop are very difficult, the duality properties are manifest. Our results are summarized by giving a Witten style action for open subcritical string fields. For the case D = 25, there are actually two solutions for a BRST invariant vertex function. The simplest does not lead to the subcritical dual loop amplitudes, because some of the redundant states still circulate the loops. However, in this case the scalar degree of freedom can be interpreted as a 26th coordinate, but with Dirichlet conditions on the open string. This is just a version of the critical string. The other solution has all redundant states removed and corresponds to the true subcritical dual model for D = 25. We consider, with partial success, the implications of this work for the interactions of subcritical closed strings.

String field equation from renormalization group

We attempt to derive an equation of motion for an open bosonic string field which is introduced as a background field in a sigma model. By using the method of Klebanov and Susskind, we obtain the β-function for this background string field and investigate its properties. We show that this β-function generates string field S-matrices. The off-shell properties (such as 1PI properties), however, remain unresolved.

Gauge fixing of open bosonic string field theory action of neveu and west

Gauge fixing of open bosonic string field theory action of neveu and west

A covariant open bosonic string field theory including the endpoint and middlepoint interaction

Extending the usual endpoint and midpoint interactions, we introduce numerous kinds of interactions, labelled by a parameter λ and obtain a non-commutative and associative string field algebra by adding up all interactions. With this algebra we develop a covariant open bosonic string field theory, which reduces to Witten's open bosonic string field theory under a special string length choice.

Combinatorics of Strings and Equivalence of Witten's String Field Theory to Polyakov's String Theory

It is shown that Polyakov's string theory and Witten's open bosonic string field theory give the same vacuum amplitudes with correct combinatorial factors in arbitrary order of perturbation expansion. The proof is based on the fact that the symmetry factor of mapping class group and the combinatorial factor of string Feynman diagram are equal. Extension to the on-shell amplitudes is also discussed.

ON THE GAUGE SYMMETRY OF THE FREE RAMOND STRING FIELD THEORY

We present the gauge invariant free, open Ramond string field theory. Our construction is based on the non-nilpotent part of the true BRS charge. We argue that this truncated charge contains the information sufficient for restoring gauge invariance. By summing all auxiliary fields we are able to close the algebra and discover the new structure consisting of new guage invariant field strengths obeying the special set of Bianchi identities. This structure can be put in the standard BRS framework showing the relation between Yamrons and Banks, Friedan, Martinec, Peskin and Preitschopfs, Ramond actions. We also discuss other formulations of the model, including one proposed by Witten.