Elsevier

Physics Letters B

Volume 499, Issues 1–2, 1 February 2001, Pages 215-222
Physics Letters B

S-duality, noncritical open string and noncommutative gauge theory

https://doi.org/10.1016/S0370-2693(01)00029-6Get rights and content

Abstract

We examine several aspects of S-duality of four-dimensional noncommutative gauge theory. By making duality transformation explicit, we find that S-dual of noncommutative gauge theory is defined in terms of dual noncommutative deformation. In ‘magnetic’ noncommutative U(1) gauge theory, we show that, in addition to gauge bosons, open D-strings constitute important low-energy excitations: noncritical open D-strings. Upon S-duality, they are mapped to noncritical open F-strings. We propose that, in dual ‘electric’ noncommutative U(1) gauge theory, the latters are identified with gauge-invariant, open Wilson lines. We argue that the open Wilson lines are chiral due to underlying parity noninvariance and obey spacetime uncertainty relation. We finally argue that, at high energy–momentum limit, the ‘electric’ noncommutative gauge theory describes correctly dynamics of delocalized multiple F-strings.

Introduction

Following the recent understanding concerning the equivalence between noncommutative and commutative gauge theories [1], an immediate question to ask is how the theory behaves under the S-duality interchanging the strong and weak coupling regimes. Indeed, this question has been addressed in several recent works [2], [3], [4], [5], [6]. (See also related works [7], [8], [9], [10], [11], [12].)

One expects an answer as simple as follows. The four-dimensional non-commutative theory describes the low-energy worldvolume dynamics of a D3-brane in the presence of a background of NS–NS two-form potential (Kalb–Ramond potential) B2 but none others. Under the S-duality of the Type IIB string theory, the D3-brane is self-dual, while the NS–NS two-form potential B2 is swapped with the R–R two-form potential C2. Thus, after the S-duality, the dual theory appears to be the one describing the low-energy worldvolume dynamics of a D3-brane in the presence of a R–R two-form potential C2, but none others. Since there is no NS–NS two-form potential present, noncommutative deformation via Seiberg–Witten map is not possible and the resulting theory ought to be a commutative theory. However, this is apparently not the answer one obtains [3], [4], [6]. Starting with a noncommutative U(1) gauge theory with coupling constant g and noncommutativity tensor θ and taking the standard duality transformation, one finds that the dual theory still remains a noncommutative U(1) gauge theory, but with coupling and noncommutativity parameters gD=1gandθD=−g2θ̃, where θ̃μν=12ϵμναβθαβ. Alternatively, as is done in [3], [4], one may utilize the gauge invariance of (F+B2) to dial out the space–space noncommutativity and treat the theory as the standard gauge theory in a constant magnetic field. The S-duality would then turn this into a dual gauge theory, but now in a constant electric field, which is gauge equivalent to a theory with space–time noncommutativity. Actually, in the dual theory, it turns out to be impossible to take a field theory limit that the dual theory would be best described by a noncritical open string theory, whose tension is of the order of the noncommutativity scale.

The aim of this Letter is to understand the S-duality via the following routes: and, if possible, to reconcile these seemingly different results concerning the S-duality of the noncommutative gauge theory from various perspectives.

Section snippets

Naive S-duality

In this section, we shall be studying S-duality of noncommutative U(1) gauge theory.1 The latter is defined by the following action: S=14g2∫d4xTr(FF), where the noncommutative field strength is defined by F=F+i{Aμ,Aν},Fμν=(∂μAν−∂νAμ) and Tr refers to “matrix notation” for spacetime index contractions, for instance, Tr(FF) means FμνFνμ. Seiberg and Witten

Closer look — noncritical open string

We have seen, in the previous section, that the naive S-dual of a noncommutative gauge theory is again a noncommutative gauge theory, but with the noncommutativity parameter θD=−g2θ̃. Thus, if the original theory were defined with ‘magnetic’ noncommutativity, the dual theory would have ‘electric’ noncommutativity and vice versa. We also note that, in performing the S-duality map, as we have expanded the original and the dual actions as in , , respectively, the result would be valid only for θF⪡1

Yet another look — strong noncommutativity limit

We would like to discuss yet another piece of physics associated with the S-duality, Eq. (1). In the previous section, we have seen that, due to the dual electric field background, the open F-string is oriented predominantly along the x0x1 directions. See Eq. (14). There, we have also argued that the open string is macroscopically stretched. According to Eq. (13), the open string is made out of the dual gauge field Bμ as a sort of coherent state configuration. Thus, it ought to be possible to

Acknowledgements

We thank M.R. Douglas, J. Klusoň, U. Lindström and G. Moore for useful discussions. S.J.R. thanks warm hospitality of Marsaryk University, New High-Energy Theory Center at Rutgers University, and Theory Division at CERN during completion of the work.

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Work supported in part by BK-21 Initiative in Physics (SNU Team-2), KRF International Collaboration Grant, KOSEF Interdisciplinary Research Grant 98-07-02-07-01-5, and KOSEF Leading Scientist Program 2000-1-11200-001-1. The work of RvU was supported by the Czech Ministry of Education under contract No. 144310006 and by the Swedish Institute.

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