Light-cone Gauge String Research Articles

Causality in string field theory

In this letter, we will investigate causality in string field theory using pp-wave light-cone gauge string field theory. We will generalise the Ramsey scheme to string field theory, and use it to analyze string field theoretical processes. An explicit characteristic function for interactive string field theory will be built using this string field theoretical Ramsey scheme. The average of the difference between the initial and final values of any operator described in string field theory will be obtained using this characteristic function. We will use the quantum information theoretical technique based on quantum Fisher information to extract information about such string field theoretical processes.

Supertwistor description of ambitwistor strings

A new ambitwistor string is constructed based on a ten-dimensional super-twistor model for the massless superparticle. Although covariant quantization is complicated by reducibility issues, a light-cone gauge analysis can be easily performed. We show that with this analysis, this supertwistor ambitwistor string is equivalent to the RNS ambitwistor string in light-cone gauge. In order to make the comparison, we develop the light-cone gauge analysis of the RNS ambitwistor string which has some novel features in terms of its expression of the scattering equations through interaction point operators.

Worldsheet theory of light-cone gauge noncritical strings on higher genus Riemann surfaces

It is possible to formulate light-cone gauge string field theory in noncritical dimensions. Such a theory corresponds to conformal gauge worldsheet theory with nonstandard longitudinal part. We study the longitudinal part of the worldsheet theory on higher genus Riemann surfaces. The results in this paper shall be used to study the dimensional regularization of light-cone gauge string field theory.

Integrable S-matrices, massive and massless modes and the AdS 2 × S 2 superstring

We derive the exact S-matrix for the scattering of particular representations of the centrally-extended psu(1|1)^2 Lie superalgebra, conjectured to be related to the massive modes of the light-cone gauge string theory on AdS_2 x S^2 x T^6. The S-matrix consists of two copies of a centrally-extended psu(1|1) invariant S-matrix and is in agreement with the tree-level result following from perturbation theory. Although the overall factor is left unfixed, the constraints following from crossing symmetry and unitarity are given. The scattering involves long representations of the symmetry algebra, and the relevant representation theory is studied in detail. We also discuss Yangian symmetry and find it has a standard form for a particular limit of the aforementioned representations. This has a natural interpretation as the massless limit, and we investigate the corresponding limits of the massive S-matrix. Under the assumption that the massless modes of the light-cone gauge string theory transform in these limiting representations, the resulting S-matrices would provide the building blocks for the full S-matrix. Finally, some brief comments are given on the Bethe ansatz.

AdS 3 × S 3 × M 4 string S-matrices from unitarity cuts

Continuing the program initiated in arXiv:1304.1798 we investigate unitarity methods applied to two-dimensional integrable field theories. The one-loop computation is generalized to encompass theories with different masses in the asymptotic spectrum and external leg corrections. Additionally, the prescription for working with potentially singular cuts is modified to cope with an ambiguity that was not encountered before. The resulting methods are then applied to three light-cone gauge string theories; i) AdS 3 × S 3 × T 4 supported by RR flux, ii) AdS 3 ×S 3 ×S 3 ×S 1 supported by RR flux and iii) AdS 3 ×S 3 ×T 4 supported by a mix of RR and NSNS fluxes. In the first case we find agreement with the exact result following from symmetry considerations and in the second case with one-loop semiclassical computations. This agreement crucially includes the rational terms and hence supports the conjecture that S-matrices of integrable field theories are cut-constructible, up to a possible shift in the coupling. In the final case, under the assumption that our methods continue to give all rational terms, we give a conjecture for the one-loop phases.

Quantum 3D tensionless string in light-cone gauge

We discuss the quantization of a tensionless closed string in light-cone gauge. It is known that by using a Hamiltonian BRST scheme the tensionless p-branes have no Lorentz anomaly in any space-time dimensions and no anomaly of space-time conformal symmetry in two dimensions. In this paper, we show that tensionless 3d strings in light-cone gauge also have no anomaly of space-time conformal symmetry. We also study the spectrum of a tensionless 3d closed string.

Amplitudes in Noncritical Dimensions and Dimensional Regularization

We study how the dimensional regularization works in the light-cone gauge string field theory. We show that it is not necessary to add a contact term to the string field theory action as a counter term in this regularization at least at the tree level. We also investigate the one-loop amplitudes of the bosonic theory in noncritical dimensions and show that they are modular invariant.

Light-cone gauge NSR strings in noncritical dimensions II — Ramond sector

Light-cone gauge superstring theory in noncritical dimensions corresponds to a worldsheet theory with nonstandard longitudinal part in the conformal gauge. The longitudinal part of the worldsheet theory is a superconformal field theory called X^{\pm} CFT. We show that the X^{\pm} CFT combined with the super-reparametrization ghost system can be described by free variables. It is possible to express the correlation functions in terms of these free variables. Bosonizing the free variables, we construct the spin fields and BRST invariant vertex operators for the Ramond sector in the conformal gauge formulation. By using these vertex operators, we can rewrite the tree amplitudes of the noncritical light-cone gauge string field theory, with external lines in the (R,R) sector as well as those in the (NS,NS) sector, in a BRST invariant way.

Light-Cone Gauge String Field Theory and Dimensional Regularization

We review our recent proposals to dimensionally regularize the light-cone gauge string field theory.

Light-cone gauge string field theory in noncritical dimensions

We study light-cone gauge string field theory in noncritical space-time dimensions. Such a theory corresponds to a string theory in a Lorentz noninvariant background. We identify the worldsheet theory for the longitudinal coordinate variables X± and study its properties. It is a CFT with the right value of Virasoro central charge, using which we propose a BRST invariant formulation of the worldsheet theory.

Observables and correlation functions inOSpinvariant string field theory

We define BRST invariant observables in the OSp invariant closed string field theory for bosonic strings. We evaluate correlation functions of these observables and show that the S-matrix elements derived from them coincide with those of the light-cone gauge string field theory.

Quantizing string theory in AdS5× S5: beyond the pp-wave

In a certain kinematic limit, where the effects of spacetime curvature (and other background fields) greatly simplify, the light-cone gauge worldsheet action for a type IIB superstring on AdS 5× S 5 reduces to that of a free field theory. It has been conjectured by Berenstein, Maldacena, and Nastase that the energy spectrum of this string theory matches the dimensions of operators in the appropriately defined large R-charge large- N c sector of N=4 supersymmetric Yang–Mills theory in four dimensions. This holographic equivalence is thought to be exact, independent of any simplifying kinematic limits. As a step toward verifying this larger conjecture, we have computed the complete set of first curvature corrections to the spectrum of light-cone gauge string theory that arises in the expansion of AdS 5× S 5 about the plane-wave limit. The resulting spectrum has the complete dependence on λ= g YM 2 N c ; corresponding results in the gauge theory are known only to second order in λ. We find precise agreement to this order, including the N=4 extended supermultiplet structure. In the process, we demonstrate that the complicated schemes put forward in recent years for defining the Green–Schwarz superstring action in background Ramond–Ramond fields can be reduced to a practical (and correct) method for quantizing the string.

Dielectric fundamental strings in matrix string theory

Matrix string theory is equivalent to type IIA superstring theory in the light-cone gauge, together with extra degrees of freedom representing D-brane states. It is therefore the appropriate framework in which to study systems of multiple fundamental strings expanding into higher-dimensional D-branes. Starting from Matrix theory in a weakly curved background, we construct the linear couplings of closed string fields to type IIA Matrix strings. As a check, we show that at weak coupling the resulting action reproduces light-cone gauge string theory in a weakly curved background. Further dualities give a type IIB Matrix string theory and a type IIA theory of Matrix strings with winding. We comment on the dielectric effect in each of these theories, giving some explicit solutions describing fundamental strings expanding into various D p-branes.

Temporal-gauge string field with open strings

A string field theory including open string fields is constructed in the temporal gauge. It consists of string interaction vertices similar to the light-cone gauge string field theory. A slight modification of the definition of the time coordinate is needed because of the existence of the open string end points.

Vacuum values for auxiliary string fields

Auxiliary string fields are introduced in light-cone gauge string field theory in order to express contact interactions as contractions of cubic vertices. The auxiliary field in the purely closed-string bosonic theory may be given a non-zero expectation value, giving rise to a phase in which world-sheets have boundaries.

Dilaton Condensation in the Covariantized Light-Cone Closed String Field Theory

We analyze dilaton condensation in the covariantized light·cone closed string field theory. We show by explicit calculation that an infinitesimal condensation of the dilaton field gives rise to the shift of the string coupling constant 9 by an amount (Jg= -(Cd -2)/2)g, where d is the space-time dimension. This agrees with Yoneya's result obtained in the light-cone gauge string field theory. We also show that the direct effect of the dilaton condensation is interpreted as the Weyl-scaling of the full OSP(d -1,112) metric including the ghost direction also.

Equivalence of the scattering amplitudes of the light-cone gauge and the Osp (26,2|2) invariant string field theories

It is shown that at all orders of perturbation the scattering amplitudes of the Osp(26,2|2) invariant bosonic string field theory of Neveu and West are equal to the ones which result from the light-cone gauge string field theory.

Lorentz Transformation in the Light-Cone Gauge String Field Theory

A complete form of Lorentz transformation law of string field is given explicitly in the light-cone gauge bosonic string field theory. It is shown that the α-symmetry which HIKKO have proved in their covariant string theory in fact implies the Lorentz invariance of the light-cone gauge string field action. We also clarify various properties of the string field products, from which the closure of the Lorentz algebra, for instancem, follows.

Heterotic string light-cone field theory

We formulate the string field theory of the heterotic string in light-cone gauge. To understand how the geometric continuity conditions that define the string interaction are implemented for the chiral torus coordinates, we study string field theory on a torus. Supersymmetry and SO 8 invariance determine the operator insertions necessary for representing the super-Poincaré algebra. The field theory of strings on orbifolds is sketched.