arXiv subjects

Changhyun Ahn

Publications and source records attributed to Changhyun Ahn.

At least 55 records · Page 3Linked to original sources

arXiv2013

Higher Spin Currents in the Holographic N=1 Coset Minimal Model

In the N=1 supersymmetric coset minimal model based on (B_N^{(1)} \oplus D_N^{(1)}, D_N^{(1)}) at level (k,1) studied recently, the standard N=1 super stress tensor of spins (3/2,2) is reviewed. By considering the stress tensor in the coset (B_N^{(1)}, D_N^{(1)}) at level k, the higher spin-2' Casimir current was obtained previously. By acting the above spin-3/2 current on the higher spin-2' Casimir current, its superpartner, the higher spin-5/2 current, can be generated and combined as the first higher spin supercurrent with spins (2', 5/2). By calculating the operator product expansions (OPE) between the higher spin supercurrent and itself, the next higher spin supercurrent can be generated with spins (7/2,4). Moreover, the other higher spin supercurrent with spins (4',9/2) can be generated by calculating the OPE between the first higher spin supercurrent with spins (2', 5/2) and the second higher spin supercurrent with spins (7/2,4). Finally, the higher spin supercurrent, (11/2,6), can be extracted from the right hand side of OPE between the higher spin supercurrents, (2', 5/2) and (4', 9/2).

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arXiv2013

Spin-5 Casimir Operator and Its Three-Point Functions with Two Scalars

By calculating the second-order pole in the operator product expansion (OPE) between the spin-3 Casimir operator and the spin-4 Casimir operator known previously, the spin-5 Casimir operator is obtained in the coset model based on (A_{N-1}^{(1)} \oplus A_{N-1}^{(1)}, A_{N-1}^{(1)}) at level (k,1). This spin-5 Casimir operator consisted of the quintic, quartic (with one derivative) and cubic (with two derivatives) WZW currents contracted with SU(N) invariant tensors. The three-point functions with two scalars for all values of 't Hooft coupling in the large N limit were obtained by analyzing the zero-mode eigenvalue equations carefully. These three-point functions were dual to those in AdS_3 higher spin gravity theory with matter. Furthermore, the exact three-point functions that hold for any finite N and k are obtained. The zero mode eigenvalue equations for the spin-5 current in CFT coincided with those of the spin-5 field in asymptotic symmetry algebra of the higher spin theory on the AdS_3. This paper also describes the structure constant appearing in the spin-4 Casimir operator from the OPE between the spin-3 Casimir operator and itself for N=4, 5 in the more general coset minimal model with two arbitrary levels (k_1, k_2).

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arXiv2013

Higher Spin Currents with Arbitrary N in the N=1 Stringy Coset Minimal Model

In the N=1 supersymmetric coset model based on (A_{N-1}^{(1)} \oplus A_{N-1}^{(1)}, A_{N-1}^{(1)}) at level (k, N), the lowest N=1 higher spin supercurrent with spins-(5/2, 3), in terms of two independent numerator WZW currents, is reviewed. By calculating the operator product expansions (OPE) between this N=1 higher spin supercurrent and itself, the next two N=1 higher spin supercurrents can be generated with spins-(7/2, 4) and (4, 9/2). These four currents are polynomials of degree 3, 4, 4, 4 in the first numerator WZW currents with level k. The complete nonlinear OPE of the lowest N=1 higher spin supercurrent for general N is obtained. The three-point functions involving two scalar primaries with one spin-2 current or spin-3 current are calculated in the large N limit for all values of the 't Hooft coupling. In particular, the light states that appeared in the case when the second level was fixed by 1 are no longer light ones because the eigenvalues are finite in the large N limit.

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arXiv2013

Higher Spin Currents in the N=1 Stringy Coset Minimal Model

This study reconsidered the N=1 supersymmetric extension of the W_3 algebra which was studied previously. This extension consists of seven higher spin supercurrents (fourteen higher spin currents in the components) as well as the N=1 stress energy tensor of spins (3/2, 2). Thus far, the complete expressions for the higher spin currents have not been derived. This paper constructs them explicitly in both the c=4 eight free fermion model and the supersymmetric coset model based on (A_2^{(1)} \oplus A_2^{(1)}, A_2^{(1)})$ at level (3,k). By acting with the above spin-3/2 current on the higher spin-3 Casimir current, its fermionic partner, the higher spin-5/2 current, can be generated and combined as a first higher spin supercurrent with spins (5/2, 3). By calculating the operator product expansions (OPE) between the higher spin supercurrent and itself, the next two higher spin supercurrents can be generated with spins (7/2, 4) and (4, 9/2). Moreover, the other two higher spin supercurrents with spins (4, 9/2) and (9/2, 5) can be generated by calculating the OPE between the first higher spin supercurrent with spins (5/2, 3) and the second higher spin supercurrent with spins (7/2, 4). Finally, the higher spin supercurrents, (11/2, 6) and (6, 13/2), can be extracted from the right hand side of the OPE between the higher spin supercurrents, (5/2, 3) and (4, 9/2).

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arXiv2013

The OPEs of Spin-4 Casimir Currents in the Holographic SO(N) Coset Minimal Models

We compute the operator product expansion (OPE) between the spin-4 current and itself in the WD_4 coset minimal model with SO(8) current algebra. The right hand side of this OPE contains the spin-6 Casimir current which is also a generator of WD_4 coset minimal model. Based on this N=8 result, we generalize the above OPE for the general N(in the WD_{N/2} coset minimal model) by using two N-generalized coupling constants initiated by Hornfeck sometime ago: the simplest OPE for the lowest higher spin currents. We also analyze the similar OPE in the WB_3(and WB_{(N-1)/2}) coset minimal model with SO(7) current algebra. The large N 't Hooft limits are discussed. Our results in two dimensional conformal field theory provide the asymptotic symmetry, at the quantum level, of the higher spin AdS_3 gravity found by Chen et al.

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arXiv2012

The Operator Product Expansion of the Lowest Higher Spin Current at Finite N

For the N=2 Kazama-Suzuki(KS) model on CP^3, the lowest higher spin current with spins (2, 5/2, 5/2,3) is obtained from the generalized GKO coset construction. By computing the operator product expansion of this current and itself, the next higher spin current with spins (3, 7/2, 7/2, 4) is also derived. This is a realization of the N=2 W_{N+1} algebra with N=3 in the supersymmetric WZW model. By incorporating the self-coupling constant of lowest higher spin current which is known for the general (N,k), we present the complete nonlinear operator product expansion of the lowest higher spin current with spins (2, 5/2, 5/2, 3) in the N=2 KS model on CP^N space. This should coincide with the asymptotic symmetry of the higher spin AdS_3 supergravity at the quantum level. The large (N,k) 't Hooft limit and the corresponding classical nonlinear algebra are also discussed.

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arXiv2012

The Large N 't Hooft Limit of Kazama-Suzuki Model

We consider N=2 Kazama-Suzuki model on CP^N=SU(N+1)/SU(N)xU(1). It is known that the N=2 current algebra for the supersymmetric WZW model, at level k, is a nonlinear algebra. The N=2 W_3 algebra corresponding to N=2 was recovered from the generalized GKO coset construction previously. For N=4, we construct one of the higher spin currents, in N=2 W_5 algebra, with spins (2, 5/2, 5/2, 3). The self-coupling constant in the operator product expansion of this current and itself depends on N as well as k explicitly. We also observe a new higher spin primary current of spins (3, 7/2, 7/2, 4). From the behaviors of N=2, 4 cases, we expect the operator product expansion of the lowest higher spin current and itself in N=2 W_{N+1} algebra. By taking the large (N, k) limit on the various operator product expansions in components, we reproduce, at the linear order, the corresponding operator product expansions in N=2 classical W_{\infty}^{cl}[λ] algebra which is the asymptotic symmetry of the higher spin AdS_3 supergravity found recently.

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arXiv2012

The Primary Spin-4 Casimir Operators in the Holographic SO(N) Coset Minimal Models

Starting from SO(N) current algebra, we construct two lowest primary higher spin-4 Casimir operators which are quartic in spin-1 fields. For N is odd, one of them corresponds to the current in the WB_{\frac{N-1}{2}} minimal model. For N is even, the other corresponds to the current in the WD_{\frac{N}{2}} minimal model. These primary higher spin currents, the generators of wedge subalgebra, are obtained from the operator product expansion of fermionic (or bosonic) primary spin-N/2 field with itself in each minimal model respectively. We obtain, indirectly, the three-point functions with two real scalars, in the large N 't Hooft limit, for all values of the 't Hooft coupling which should be dual to the three-point functions in the higher spin AdS_3 gravity with matter.

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arXiv2012

Towards New Membrane Flow from de Wit-Nicolai Construction

The internal 4-form field strengths with 7-dimensional indices have been constructed by de Wit and Nicolai in 1986. They are determined by the following six quantities: the 56-bein of 4-dimensional N=8 gauged supergravity, the Killing vectors on the round seven-sphere, the covariant derivative acting on these Killing vectors, the warp factor, the field strengths with 4-dimensional indices and the 7-dimensional metric. In this paper, by projecting out the remaining mixed 4-form field strengths in an SU(8) tensor that appears in the variation of spin 1/2 fermionic sector, we also write down them explicitly in terms of some of the above quantities. For the known critical points, the N=8 SO(8) point and the nonsupersymmetric SO(7)^{+} point, we reproduce the corresponding 11-dimensional uplifts by computing the full nonlinear expressions. Moreover, we find out the 11-dimensional lift of the nonsupersymmetric SO(7)^{+} invariant flow. We decode their implicit formula for the first time and the present work will provide how to obtain the new supersymmetric or nonsupersymmetric membrane flows in 11-dimensions.

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arXiv2012

The Coset Spin-4 Casimir Operator and Its Three-Point Functions with Scalars

We find the GKO coset construction of the dimension 4 Casimir operator that contains the quartic WZW currents contracted with completely symmetric SU(N) invariant tensors of ranks 4, 3, and 2. The requirements, that the operator product expansion with the diagonal current is regular and it should be primary under the coset Virasoro generator of dimension 2, fix all the coefficients in spin-4 current, up to two unknown coefficients. The operator product expansion of coset primary spin-3 field with itself fixes them completely. We compute the three-point functions with scalars for all values of the 't Hooft coupling in the large N limit. At fixed 't Hooft coupling, these three-point functions are dual to that found by Chang and Yin recently in the undeformed AdS_3 bulk theory (higher spin gravity with matter).

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arXiv2011

The Large N 't Hooft Limit of Coset Minimal Models

Recently, Gaberdiel and Gopakumar proposed that the two-dimensional WA_{N-1} minimal model conformal field theory in the large N 't Hooft limit is dual to the higher spin theories on the three-dimensional AdS space with two complex scalars. In this paper, we examine this proposal for the WD_{N/2} and WB_{(N-1)/2} minimal models initiated by Fateev and Lukyanov in 1988. By analyzing the renormalization group flows on these models, we find that the gravity duals in AdS space are higher spin theories coupled to two equally massive real scalar fields. We also describe the large N 't Hooft limit for the minimal model of the second parafermion theory.

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arXiv2010

Holographic N=1 Supersymmetric Membrane Flows

The M-theory lift of N=2 SU(3) x U(1)_R-invariant RG flow via a combinatorical use of the 4-dimensional flow and 11-dimensional Einstein-Maxwell equations was found previously. By taking the three internal coordinates differently and preserving only SU(3) symmetry from the CP^2 space, we find a new 11-dimensional solution of N=1 SU(3)-invariant RG flow interpolating from N=8 SO(8)-invariant UV fixed point to N=2 SU(3) x U(1)_R-invariant IR fixed point in 4-dimensions. We describe how the corresponding 3-dimensional N=1 superconformal Chern-Simons matter theory deforms. By replacing the above CP^2 space with the Einstein-Kahler 2-fold, we also find out new 11-dimensional solution of N=1 SU(2) x U(1)-invariant RG flow connecting above two fixed points in 4-dimensions.

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arXiv2010

Towards An N=1 SU(3)-Invariant Supersymmetric Membrane Flow In Eleven-Dimensional Supergravity

The M-theory lift of N=1 G_2-invariant RG flow via a combinatoric use of the 4-dimensional RG flow and 11-dimensional Einstein-Maxwell equations was found some time ago. The 11-dimensional metric, a warped product of an asymptotically AdS_4 space with a squashed and stretched 7-sphere, for SU(3)-invariance was found before. In this paper, by choosing the 4-dimensional internal space as CP^2 space, we discover an exact solution of N=1 G_2-invariant flow to the 11-dimensional field equations. By an appropriate coordinate transformation on the three internal coordinates, we also find an 11-dimensional solution of N=1 G_2-invariant flow interpolating from N=8 SO(8)-invariant UV fixed point to N=1 G_2-invariant IR fixed point. In particular, the 11-dimensional metric and 4-forms at the N=1 G_2 fixed point for the second solution will provide some hints for the 11-dimensional lift of whole N=1 SU(3) RG flow connecting this N=1 G_2 fixed point to N=2 SU(3) x U(1)_R fixed point in 4-dimensions.

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arXiv2010

The Gauge Dual of Gauged N=8 Supergravity Theory

The most general SU(3)-singlet space of gauged N=8 supergravity in four-dimensions is studied recently. The SU(3)-invariant six scalar fields are realized by six real four-forms. A family of holographic N=1 supersymmetric RG flows on M2-branes in three-dimensions is described. This family of flows is driven by three independent mass parameters from the N=8 SO(8) theory and is controlled by two IR fixed points, N=1 G_2-invariant one and N=2 SU(3) x U(1)-invariant one. The generic flow with arbitrary mass parameters is N=1 supersymmetric and reaches to the N=2 SU(3) x U(1) fixed point where the three masses become identical. A particular N=1 supersymmetric SU(3)-preserving RG flow from the N=1 G_2-invariant fixed point to the N=2 SU(3) x U(1)-invariant fixed point is also discussed.

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arXiv2010

N=8 Gauged Supergravity Theory and N=6 Superconformal Chern-Simons Matter Theory

By studying the previously known holographic N=4 supersymmetric renormalization group flow(Gowdigere-Warner) in four dimensions, we find the mass deformed Chern-Simons matter theory which has N=4 supersymmetry by adding the four mass terms among eight adjoint fields. The geometric superpotential from the eleven dimensions is found and provides the M2-brane probe analysis. As second example, we consider known holographic N=8 supersymmetric renormalization group flow(Pope-Warner) in four dimensions. The eight mass terms are added and similar geometric superpotential is obtained.

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arXiv2009

Are There Any New Vacua of Gauged N=8 Supergravity in Four Dimensions?

We consider the most general SU(3) singlet space of gauged N=8 supergravity in four-dimensions. The SU(3)-invariant six scalar fields in the theory can be viewed in terms of six real four-forms. By exponentiating these four-forms, we eventually obtain the new scalar potential. For the two extreme limits, we reproduce the previous results found by Warner in 1983. In particular, for the N=1 G_2 critical point, we find the constraint surface parametrized by three scalar fields on which the cosmological constant has the same value. We obtain the BPS domain-wall solutions for restricted scalar submanifold. We also describe the three-dimensional mass-deformed superconformal Chern-Simons matter theory dual to the above supersymmetric flows in four-dimensions.

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arXiv2009

The Gauge Dual of A Warped Product of AdS_4 and A Squashed and Stretched Seven-Manifold

Corrado, Pilch and Warner in 2001 have found the second 11-dimensional solution where the deformed geometry of S^7 in the lift contains S^2 x S^2. We identify the gauge dual of this background with the theory described by Franco, Klebanov and Rodriguez-Gomez recently. It is the U(N) x U(N) x U(N) gauge theory with two SU(2) doublet chiral fields B_1 transforming in the (N, Nbar, 1), B_2 transforming in the (1, N, Nbar), C_1 in the (1, Nbar, N) and C_2 in the (Nbar, N, 1) as well as an adjoint field Φin the (1, adj, 1) representation. By adding the mass term for adjoint field Φ, the detailed correspondence between fields of AdS_4 supergravity and composite operators of the IR field theory is determined. Moreover, we compute the spin-2 KK modes around a warped product of AdS_4 and a squashed and stretched seven-manifold. This background with global SU(2) x SU(2) x U(1)_R symmetry is related to a U(N) x U(N) x U(N) N=2 superconformal Chern-Simons matter theory with eighth-order superpotential and Chern-Simons level (1,1,-2). The mass-squared in AdS_4 depends on SU(2) x SU(2) x U(1)_R quantum numbers and KK excitation number. The dimensions of spin-2 operators are found.

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arXiv2009

More on Meta-Stable Brane Configurations by Dualizing the Multiple Gauge Groups

We reexamine the N=1 supersymmetric gauge theories with product gauge groups by adding the mass terms and the quartic terms for the flavors: two gauge group theory with fundamentals, bifundamentals and adjoints, three gauge group theory with fundamentals and bifundamentals, and their orientifold 4-plane generalizations. By moving the branes appropriately, we obtain the corresponding dual gauge theories. By analyzing the dual superpotentials, we present the type IIA nonsupersymmetric meta-stable brane configurations.

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