Boundary String Field Theory Research Articles

Open String Renormalization Group Flow as a Field Theory

AbstractThis article shows that the integral flow‐lines of the RG‐flow of open string theory can be interpreted as the solitons of a Hořova–Lifshitz sigma‐model of open membranes. The authors argue that the effective background description of this model implies the g‐theorem of open string theory. Its close connection to boundary string field theory is described. Additionally, the study endows the Hilbert space of the open membrane with a graded non‐commutative, associative, cyclic algebra and construct an open membrane field theory, whose action measures the energy difference between different backgrounds in open string field theory. The authors use an identity‐based membrane field to proof Sen's conjecture. Finally, the ideas are applied to the topological string and it is shown that the membrane action is quantized in equivariant K‐theory of the moduli space of framed instantons.

Local Zeta Functions and Koba–Nielsen String Amplitudes

This article is a survey of our recent work on the connections between Koba–Nielsen amplitudes and local zeta functions (in the sense of Gel’fand, Weil, Igusa, Sato, Bernstein, Denef, Loeser, etc.). Our research program is motivated by the fact that the p-adic strings seem to be related in some interesting ways with ordinary strings. p-Adic string amplitudes share desired characteristics with their Archimedean counterparts, such as crossing symmetry and invariance under Möbius transformations. A direct connection between p-adic amplitudes and the Archimedean ones is through the limit p→1. Gerasimov and Shatashvili studied the limit p→1 of the p-adic effective action introduced by Brekke, Freund, Olson and Witten. They showed that this limit gives rise to a boundary string field theory, which was previously proposed by Witten in the context of background independent string theory. Explicit computations in the cases of 4 and 5 points show that the Feynman amplitudes at the tree level of the Gerasimov–Shatashvili Lagrangian are related to the limit p→1 of the p-adic Koba–Nielsen amplitudes. At a mathematical level, this phenomenon is deeply connected with the topological zeta functions introduced by Denef and Loeser. A Koba–Nielsen amplitude is just a new type of local zeta function, which can be studied using embedded resolution of singularities. In this way, one shows the existence of a meromorphic continuations for the Koba–Nielsen amplitudes as functions of the kinematic parameters. The Koba–Nielsen local zeta functions are algebraic-geometric integrals that can be defined over arbitrary local fields (for instance R, C, Qp, Fp((T))), and it is completely natural to expect connections between these objects. The limit p tends to one of the Koba–Nielsen amplitudes give rise to new amplitudes which we have called Denef–Loeser amplitudes. Throughout the article, we have emphasized the explicit calculations in the cases of 4 and 5 points.

Classical open string amplitudes from boundary string field theory

We calculate the corrections to the open string BRST charge in boundary string field theory and show that the expansion coefficients agree with the perturbative S-matrix to all orders. In mathematical terms, boundary string field theory describes the minimal model of open string field theory.

Some special features of a rotating-moving Dp-brane

Using the boundary string field theory (BSFT) techniques we study the boundary state and partition function for a dynamical (rotating-moving) Dp-brane coupled to the electromagnetic and tachyonic background fields in superstring theory. By making use of the created partition function, the super BSFT action with a tachyonic field and Dirac-Born-Infeld–type action will be constructed. By analyzing the obtained action interesting features will be revealed.

Ramond-Ramond couplings of D-branes

Applying supersymmetric localization for superstring worldsheet theory with N=(1,1) supersymmetries on a cylinder and with arbitrary boundary interactions, we find the most general formula for the Ramond-Ramond (RR) coupling of D-branes. We allow all massive excitations of open superstrings, and find that only a finite number of them can contribute to the formula. The formula is written by Quillen's superconnection which includes higher form gauge fields, and the resultant general Chern-Simons terms are consistent with RR charge quantization. Applying the formula to boundary string field theory of a BPS D9-brane or a D9-antiD9 brane system, we find that any D9-brane creation via massive mode condensation is impossible.

A landscape in boundary string field theory: New class of solutions with massive state condensation

We solve the equation of motion of boundary string field theory allowing generic boundary operators quadratic in $X$, and explore string theory non-perturbative vacua with massive state condensation. Using numerical analysis, a large number of new solutions are found. Their energies turn out to distribute densely in the range between the D-brane tension and the energy of the tachyon vacuum. We discuss an interpretation of these solutions as perturbative closed string states. From the cosmological point of view, the distribution of the energies can be regarded as the so-called landscape of string theory, as we have a vast number of non-perturbative string theory solutions including one with small vacuum energy.

On open-closed extension of boundary string field theory

We investigate a classical open-closed string field theory whose open string sector is given by boundary string field theory. The open-closed interaction is introduced by the overlap of a boundary state with a closed string field. With the help of the Batalin-Vilkovisky formalism, the closed string sector is determined to be the HIKKO closed string field theory. We also discuss the gauge invariance of this theory in both open and closed string sides.

Backgrounds in boundary string field theory

We study the role of closed string backgrounds in boundary string field theory. Background independence requires introducing dual boundary fields, which are reminiscent of the doubled field formalism. We find a correspondence between closed string backgrounds and collective excitations of open strings described by vertex operators involving the dual fields. We discuss the renormalization group flow, solutions, and stability in an example.

Cosmology with non-minimally coupled k-field

We consider non-minimally coupled (with gravity) scalar field with non-canonical kinetic energy. The form of the kinetic term is of Dirac-Born-Infeld (DBI) form.We study the early evolution of the universe when it is sourced only by the k-field, as well as late time evolution when both the matter and k-field are present. For the k-field, we have considered constant potential as well as potential inspired from Boundary String Field Theory (B-SFT). We show that it is possible to have inflationary solution in early time as well as late time accelerating phase. The solutions also exhibit attractor property in a sense that it does not depend on the initial conditions for a certain values of the parameters.

On the general action of boundary (super) string field theory

On the general action of boundary (super) string field theory

Tachyon solutions in boundary and open string field theory

We construct rolling tachyon solutions of open and boundary string field theory (OSFT and BSFT, respectively), in the bosonic and supersymmetric (susy) case. The wildly oscillating solution of susy OSFT is recovered, together with a family of time-dependent BSFT solutions, for the bosonic and susy string. These are parametrized by an arbitrary constant $r$ involved in solving the Green equation of the target fields. When $r=0$ we recover previous results in BSFT, whereas for $r$ attaining the value predicted by OSFT it is shown that the bosonic OSFT solution is the derivative of the boundary one; in the supersymmetric case the relation between the two solutions is more complicated. This technical correspondence sheds some light on the nature of wild oscillations, which appear in both theories whenever $r>0$.

Tachyon condensation on torus and T-duality

We find an exact solution, with a nonzero net D-brane charge, in the boundary string field theory of brane-anti-brane pairs on a torus. We explicitly take the T-dual of this configuration. The Nahm-transformation of the instantons is derived from the tachyon condensation.

Nonlocal instantons and solitons in string models

We study a class of nonlocal systems which can be described by a local scalar field diffusing in an auxiliary radial dimension. As examples p-adic, open and boundary string field theory are considered on Minkowski, Friedmann–Robertson–Walker and Euclidean metric backgrounds. Starting from distribution-like initial field configurations which are constant almost everywhere, we construct exact and approximate nonlocal solutions. The Euclidean p-adic lump is interpreted as a solitonic brane, and the Euclidean kink of supersymmetric open string field theory as an instanton. Some relations between solutions of different string theories are highlighted also thanks to a reformulation of nonlocal systems as fixed points in a renormalization group flow.

On the general action of boundary (super)string field theory

We reconstruct boundary superstring field theory via boundary states. After a minor modification of the fermionic two-form, all the equations needed for Batalin-Vilkovisky formulation are simply represented by closed string oscillators and the proof of gauge invariance is drastically simplified. The general form of the action of boundary superstring field theory is also obtained without any assumption and found to take exactly the same form as the bosonic one. As a special case of this action, we revisit the conjecture that the action is simply given by the disk partition function when matter and ghosts are completely decoupled.

REFORMULATION OF BOUNDARY STRING FIELD THEORY IN TERMS OF BOUNDARY STATE

We reformulate bosonic boundary string field theory in terms of boundary state. In our formulation, we can formally perform the integration of target space equations of motion for arbitrary field configurations without assuming decoupling of matter and ghost. This is a short summary of our contribution to the international workshop "Progress of String Theory and Quantum Field Theory" at Osaka City University (December 7-10, 2007).

Reformulation of Boundary String Field Theory in terms of Boundary State

Reformulation of Boundary String Field Theory in terms of Boundary State

BPS limit of multi- D- and DF-strings in boundary string field theory

A BPS limit is systematically derived for straight multi- D- and DF-strings from the D3D¯3 system in the context of boundary superstring field theory. The BPS limit is obtained in the limit of thin D(F)-strings, where the Bogomolny equation supports singular static multi-D(F)-string solutions. For the BPS multi-string configurations with arbitrary separations, BPS sum rule is fulfilled under a Gaussian type tachyon potential and reproduces exactly the descent relation. For the DF-strings ((p,q)-strings), the distribution of fundamental string charge density coincides with its energy density and the Hamiltonian density takes the BPS formula of square-root form.

Exact BPS Kink in BCFT, DBI EFT, NCFT, and BSFT

We discuss single topological BPS kinks with non-zero thickness, which are exact solutions in various contexts including Dirac-Born-Infeld type effective field theory, noncommutative field theory, boundary conformal field theory, and boundary string field theory. The tachyon field is monotonically increasing (or decreasing) and connects the isolated vacua at positive and negative infinity irrespective of the theories of our interest. It is expressed by a simple linear function, τ (X) ∝ X, in the case of boundary conformal field theory. The obtained tachyon kink in the presence of critical electromagnetic field is interpreted as a single thick BPS D(p− 1)-brane (or D(p− 1)F1-composite) inside an unstable Dp-brane with background fluid of fundamental strings.

Tachyonic Kinks on Unstable D-branes in Boundary String Field Theory

Tachyonic Kinks on Unstable D-branes in Boundary String Field Theory

Open-closed string correspondence: D-brane decay in curved space

This paper analyzes the effect of curved closed string backgrounds on the stability of D-branes within boundary string field theory. We identify the non-local open string background that implements shifts in the closed string background and analyze the tachyonic sector off-shell. The renormalization group flow reveals some characteristic properties, which are expected for a curved background, like the absence of a stable space-filling brane. In 3-dimensions we describe tachyon condensation processes to lower-dimensional branes, including a curved 2-dimensional brane. We argue that this 2-brane is perturbatively stable. This is in agreement with the known maximally symmetric WZW-branes and provides further support to the bulk-boundary factorization approach to open-closed string correspondence.