arXiv subjects

I. Y. Park

Publications and source records attributed to I. Y. Park.

67 records · Page 4Linked to original sources

arXiv2003

Improved Off-Shell Scattering Amplitudes in String Field Theory and New Computational Methods

We report on new results in Witten's cubic string field theory for the off-shell factor in the 4-tachyon amplitude that was not fully obtained explicitly before. This is achieved by completing the derivation of the Veneziano formula in the Moyal star formulation of Witten's string field theory (MSFT). We also demonstrate detailed agreement of MSFT with a number of on-shell and off-shell computations in other approaches to Witten's string field theory. We extend the techniques of computation in MSFT, and show that the j=0 representation of SL(2,R) generated by the Virasoro operators $L_{0},L_{\pm1}$ is a key structure in practical computations for generating numbers. We provide more insight into the Moyal structure that simplifies string field theory, and develop techniques that could be applied more generally, including nonperturbative processes.

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arXiv2003

Tachyon condensation and `bounce' in the D1-D5 system

We construct supergravity solutions dual to microstates of the D1-D3-D5 system with nonzero B field moduli. Just like the D1-D5 solutions in hep-th/0109154 these solutions are generically nonsingular everywhere, with the `throat' closing smoothly near r=0. We write expressions relating the asymptotic supergravity fields to the integral brane charges. We study the infall of a D1 brane down the throat of the geometries. This test brane `bounces' off the smooth end for generic initial conditions. The details of the bounce depend on both the choice of D1-D3-D5 microstate and the direction of approach of the infalling D1 brane. In the dual field theory description we see that the tachyon mode starts to condense, but the tachyon bounces back up the potential hill without reaching the deepest point of the potential.

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arXiv2002

AdS and dS Braneworld Kaluza-Klein Reduction

We obtain new results for consistent braneworld Kaluza-Klein reductions, showing how we can derive four-dimensional N=2 gauged supergravity ``localised on the AdS_4 brane'' as an exact embedding in five-dimensional N=4 gauged supergravity. Similarly, we obtain five-dimensional N=2 gauged supergravity localised on an AdS_5 brane as a consistent Kaluza-Klein reduction from six-dimensional N=4 gauged supergravity. These embeddings can be lifted to type IIB and massive type IIA supergravity respectively. The new AdS braneworld Kaluza-Klein reductions are generalisations of earlier results on braneworld reductions to ungauged supergravities. The lower-dimensional cosmological constant in our AdS braneworld reductions is an adjustable parameter, and so it can be chosen to be small enough to be phenomenologically realistic, even if the higher-dimensional one is of Planck scale. We also discuss analytic continuations to give a de Sitter gauged supergravity in four dimensions as a braneworld Kaluza-Klein reduction. We find that there are two distinct routes that lead to the same four-dimensional theory. In one, we start from a five-dimensional de Sitter supergravity, which itself arises from a Kaluza-Klein reduction of type IIB^* supergravity on the hyperbolic 5-sphere. In the other, we start from AdS gauged supergravity in five dimensions, with an analytic continuation of the two 2-form potentials, and embed the four-dimensional de Sitter supergravity in that. The five-dimensional theory itself comes from an O(4,3)/O(3,2) reduction of Hull's type IIB_{7+3} supergravity in ten dimensions.

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arXiv2001

On the M5 and the AdS7/CFT6 Correspondence

The chiral primary operators of the D=6 superconformal (2,0) theory corresponding to 14 scalars of N=4 D=7 supergravity are obtained by expanding the world volume action for the M5-brane around an AdS_7 x S^4 background. In the leading order, the operators take their values in the symmetric traceless representation of the SO(5) R-symmetry group in consistency with the early conjecture on their structure based on the superconformal symmetry and Matrix-like model arguments.

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arXiv2001

Strong Coupling Limit of Open String: Born-Infeld Analysis

We consider a large coupling limit of a Born-Infeld action in a curved background of an arbitrary metric and a constant two form field. Following hep-th/0009061, we go to the Hamiltonian description. The Hamiltonian can be dualized and the dual action admits a string-like configuration as its solution. We interpret it as a closed string configuration. The procedure can be viewed as a novel way of bringing out the appropriate degrees of freedom, a closed string, for a open string under the strong coupling limit. We argue that this interpretation implies a large number of dual pairs of gauge and gravity theories whose particular examples are AdS/CFT and matrix theory conjectures.

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arXiv2001

Supergravity duals of gauge theories from F(4) gauged supergravity in six dimensions

We construct supergravity solutions dual to twisted field theories that are the worldvolume theories of D4-branes wrapped on 2, 3-cycles, and NS-fivebranes on 3-cycles. We first obtain the solutions for the Romans' six-dimensional gauged supergravity theories and then up-lift them to ten dimensions. In particular, we find solutions for field configurations with either non-Abelian fields or B-fields being excited. One of these solutions, in the massless case, is up-lifted to the massless type IIA string theory. This is the first example of such a kind. The cases studied provide new examples of the AdS/CFT duality involving twisted field theories.

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arXiv2001

D-branes as Solitons of an N=1, D=10 Non-commutative Gauge Theory

We consider a Dp brane within a D9 brane in the presence of a B-field whose polarization is {\em transverse} to the Dp brane. To be definite, we take a D3-D9 system. It is observed that the system has the same pattern of supersymmetry breaking as that of a soliton of the six dimensional non-commutative gauge theory that is obtained by dimensional reduction of an {\cal N}=1, D=10 gauge theory. These results indicate that the soliton solution is the low energy realization of a D3 brane in a D9 brane with a transverse B-field, hence can be viewed as a generalization of the previous results in the literature where similar observations were made for lower codimensional cases.

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arXiv2000

Super Yang-Mills Operators from the D3-brane Action in a Curved Background

A consistent truncation of IIB on S^5 has been obtained in the sector of the metric and the 4-form potential. The ansatz contains 20 scalars and all 15 gauge fields of ${\cal N}=8$ gauged supergravity in five dimensions. With this fully non-linear ansatz, the calculations for n-point correlators of super Yang-Mills (SYM) theory via AdS/CFT are simpler than those in the literature that use {\em linear} ansatz followed by non-linear field redefinitions. We work out the SYM operators that couple to the scalars by expanding the Dirac-Born-Infeld (DBI) action plus Wess-Zumino (WZ) terms around an $AdS_5\timesS^5$ background with the metric fluctuations. The resulting operators agree with those based on a superconformal symmetry argument. We discuss the significance of our results.

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arXiv2000

Hyperkähler Quotients, Mirror Symmetry, and F-theory

Using the graphical method developed in hep-th/9908082, we obtain the full curve corresponding to the hyperkähler quotient from the extended E_7 Dynkin diagram. As in the E_6 case discussed in the same paper above, the resulting curve is the same as the one obtained by Minahan and Nemeschansky. Our results seem to indicate that it is possible to define a generalized Coulomb branch such that four dimensional mirror symmetry would act by interchanging the generalized Coulomb branch with the Higgs branch of the dual theory. To understand these phenomena, we discuss mirror symmetry and F-theory compactifications probed by D3 branes.

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arXiv1999

Fundamental vs. Solitonic Description of D3 branes

Type IIB string theory expanded around D3 brane backgrounds describes the dynamics of D3 branes as solitonic objects. On the other hand, there is a fundamental description of them via Polchinski's open strings with Dirichlet boundary conditions. Since these two descriptions describe the dynamics of the same objects, D3 branes, it is natural to believe that they are dual. Therefore at this level, we have a string-string duality as opposed to a string-field theory duality. Once we take the same limits in both descriptions, Maldacena Conjecture in its weaker form follows. We try to make this viewpoint precise and study the implication of it for the stronger form of Maldacena Conjecture.

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arXiv1999

Non-renormalization of two and three Point Correlators of N=4 SYM in N=1 Superspace

Certain two and three point functions of gauge invariant primary operators of ${\cal N}=4$ SYM are computed in ${\cal N}=1$ superspace keeping all the $þ$-components. This allows one to read off many component descendent correlators. Our results show the only possible $g^2_{YM}$ corrections to the free field correlators are contact terms. Therefore they vanish for operators at separate points, verifying the known non-renormalization theorems. This also implies the results are consistent with ${\cal N}=4$ supersymmetry even though the Lagrangian we use has only ${\cal N}=1$ manifest supersymmetry. We repeat some of the calculations using supersymmetric Landau gauge and obtain, as expected, the same results as those of supersymmetric Feynman gauge.

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arXiv1999

Self-Dual Effective Action of N=4 Super-Yang Mills

The full low energy effective action of N=4 SYM is believed to be self-dual. Starting with the first two leading terms in a momentum expansion of this effective action, we perform a duality transformation and find the conditions for self-duality. These determine some of the higher order terms. We compare the effective action of N=4 SYM with the probe-source description of type II_B D3-branes in the AdS_5 \times S_5 background. We find agreement up to six derivative terms if we identify the separation of the 3-branes with a redefinition of the gauge scalar that involves the gauge field strength.

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arXiv1998

On dual 3-brane actions with partially broken N=2 supersymmetry

The N=1 superspace generalization of the 3-brane action in 6 dimensions with partially broken N=2 supersymmetry can be constructed using N=1 chiral, complex linear, or real linear superfields. The physical scalars of these multiplets give equivalent descriptions of the two transverse coordinates. The second supersymmetry is realized nonlinearly in all these actions. We derive the superspace brane actions and their nonlinear supersymmetry for both kinds of linear superfields when we break N=2 supersymmetry spontaneously. This breaking is realized in the free action of hypermultiplets that live in N=2 projective superspace by constraining the N=2 multiplets to reduce them to a pure Goldstone multiplet. For the chiral superfield, the superspace brane action and nonlinear supersymmetry can be deduced by dualizing the brane action of either linear superfield. We find that the dual action is unique up to field redefinitions that introduce arbitrariness in the dependence on the auxiliary fields.

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