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Xiao-Jun Wang

Publications and source records attributed to Xiao-Jun Wang.

At least 19 recordsLinked to original sources
arXiv2006

BPS R-balls in N=4 SYM on R X S^3, Quantum Hall Analogy and AdS/CFT Holography

In this paper, we propose a new approach to study the BPS dynamics in N=4 supersymmetric U(N) Yang-Mills theory on R X S^3, in order to better understand the emergence of gravity in the gauge theory. Our approach is based on supersymmetric, space-filling Q-balls with R-charge, which we call R-balls. The usual collective coordinate method for non-topological scalar solitons is applied to quantize the half and quarter BPS R-balls. In each case, a different quantization method is also applied to confirm the results from the collective coordinate quantization. For finite N, the half BPS R-balls with a U(1) R-charge have a moduli space which, upon quantization, results in the states of a quantum Hall droplet with filling factor one. These states are known to correspond to the ``sources'' in the Lin-Lunin-Maldacena geometries in IIB supergravity. For large N, we find a new class of quarter BPS R-balls with a non-commutativity parameter. Quantization on the moduli space of such R-balls gives rise to a non-commutative Chern-Simons matrix mechanics, which is known to describe a fractional quantum Hall system. In view of AdS/CFT holography, this demonstrates a profound connection of emergent quantum gravity with non-commutative geometry, of which the quantum Hall effect is a special case.

hep-th↗
arXiv2005

Dynamics of Giant-Gravitons in the LLM geometry and the Fractional Quantum Hall Effect

The LLM's 1/2 BPS solutions of IIB supergravity are known to be closely related to the integer quantum Hall droplets with filling factor $ν=1$, and the giant gravitons in the LLM geometry behave like the quasi-holes in those droplets. In this paper we consider how the fractional quantum Hall effect may arise in this context, by studying the dynamics of giant graviton probes in a special LLM geometry, the AdS_5 X S^5 background, that corresponds to a circular droplet. The giant gravitons we study are D3-branes wrapping on a 3-sphere in S^5. Their low energy world-volume theory, truncated to the 1/2 BPS sector, is shown to be described by a Chern-Simons finite-matrix model. We demonstrate that these giant gravitons may condense at right density further into fractional quantum Hall fluid due to the repulsive interaction in the model, giving rise to the new states in IIB string theory. Some features of the novel physics of these new states are discussed.

hep-th↗
arXiv2005

Strings in Noncommutative Spacetime

Free bosonic strings in noncommutative spacetime are investigated. The string spectrum is obtained in terms of light-cone quantization. We construct two different models. In the first model the critical dimension is still required to be 26 while only extreme high energy spectrum is modified by noncommutative effect. In the second model, however, the critical dimension is reduced to be less than 26 while low-energy (massless) spectrum only contains degrees of freedom of our four dimensional physics.

hep-th↗
arXiv2005

Spinning Strings on Deformed AdS_5 x T^{1,1} with NS B-field

We study classical spinning closed string configuration on logarithmically deformed AdS_5 x T^{1,1} background with non-trivial Neveu-Schwarz B-field in which IIB string theory is dual to a non-conformal N=1 SU(N+M) x SU(N) gauge theory. The integrability on original AdS_5 x T^{1,1} background are significantly reduced by B-field. We find several spinning string solutions with two different ansatzs. Solutions for point-like strings and few circular strings are explicitly obtained. Folded spinning string solutions along radial direction are shown to be allowed in this background. These solutions exhibit novel properties and bring some challenges to understand them from dual quantum field theory.

hep-th↗
arXiv2004

Cosmological Constant as Vacuum Energy Density of Quantum Field Theories on Noncommutative Spacetime

We propose a new approach to understand hierarchy problem for cosmological constant in terms of considering noncommutative nature of space-time. We calculate that vacuum energy density of the noncommutative quantum field theories in nontrivial background, which admits a smaller cosmological constant by introducing an higher noncommutative scale $μ_{NC}\sim M_p$. The result $ρ_Λ\sim 10^{-6}Λ_{SUSY}^8M_p^4/μ_{NC}^8$ yields cosmological constant at the order of current observed value for supersymmetry breaking scale at 10TeV. It is the same as Banks' phenomenological formula for cosmological constant.

hep-th↗
arXiv2004

A note on brane/flux annihilation and dS vacua in string theory

We reconsider the dynamics of p anti-D3 branes inside the Klebanov-Strassler geometry, in which M units of R-R 3-form flux and K units of NS-NS 3-form flux are presented in deformed conifold. We find that anti-D3 branes blow up into a spherical D5-brane at weak string coupling via quantum tunnelling. The D5-brane can be either stable or unstable, depending on number of background flux. The nucleation rate of D5-brane is suppressed by \exp{-Mp^2}. The classical mechanically the evolution of unstable D5-brane annihilates one unit of R-R flux and ends with (K-p) D3-branes. This observation is consistent with one by Kachru, Pearson and Verlinde, who shew that anti-D3 branes in KS geometry can blow up into a spherical NS5 brane at strong string coupling, because NS5-brane is lighter that D5-brane at strong string coupling. We also argue that the system can end with a meta-stable dS vacuum by fine tuning of number of background flux.

hep-th↗
arXiv2004

Open Spin Chain and Open Spinning String

In this letter, we study the open spinning strings and their SYM duals. A new class of folded open spinning strings is found. At planar one-loop level in SYM, by solving the thermodynamic limit of the Bethe ansatz equations for an integrable open spin chain, we find good agreement with string theory predictions for energies of both circular and folded two-spin solutions. A universal relation between the open and closed spinning strings is verified in the spin chain approach.

hep-th↗
arXiv2004

Integrable Open Spin Chain in Super Yang-Mills and the Plane-wave/SYM duality

We investigate the integrable structures in an N=2 superconfomal Sp(N) Yang-Mills theory with matter, which is dual to an open+closed string system. We restrict ourselves to the BMN operators that correspond to free string states. In the closed string sector, an integrable structure is inherited from its parent theory, N=4 SYM. For the open string sector, the planar one-loop mixing matrix for gauge invariant holomorphic operators is identified with the Hamiltonian of an integrable SU(3) open spin chain. Using the K-matrix formalism we identify the integrable open-chain boundary conditions that correspond to string boundary conditions. The solutions to the algebraic Bethe ansatz equations (ABAE) with a few impurities are shown to recover the anomalous dimensions that exactly match the spectrum of free open string in the plane-wave background. We also discuss the properties of the solutions of ABAE beyond the BMN regime.

hep-th↗
arXiv2004

Intersecting branes and adding flavors to the Maldacena-Nunez background

We study adding flavors into the Maldacena-Nŭnez background. It is achieved by introducing spacetime filling D9-branes or intersecting D5$'$-branes into the background with a wrapping D5-brane. Both D9-branes and D5$'$-branes can be spacetime filling from the 5D bulk point of view. At the probe limit it corresponds to introducing non-chiral fundamental flavors into the dual N=1 SYM. We propose a method to twist the fundamental flavor which has to involve open string charge. It reflects the fact that coupling fundamental matter to SYM in the dual string theory corresponds to adding an open string sector

hep-th↗
arXiv2003

Integrable Spin Chain and Operator Mixing in N=1,2 Supersymmetric Theories

We study operator mixing, due to planar one-loop corrections, for composite operators in D=4 supersymmetric theories. We present some N=1,2 Yang-Mills and Wess-Zumino models, in which the planar one-loop anomalous dimension matrix in the sector of holomorphic scalars is identified with the Hamiltonian of an integrable quantum spin chain of SU(3) or SU(2) symmetry, even if the theory is away from the conformal points. This points to a more universal origin of the integrable structure beyond superconformal symmetry. We also emphasize the role of the superpotential in the appearance of the integrable structure. The computations of operator mixing in our examples by solving Bethe Ansatz equations show some new features absent in N=4 SYM.

hep-th↗
arXiv2003

Confinement of N=1 Super Yang-Mills from Supergravity

We calculate circular Wilson loop expectation value of pure ${\cal N}=1$ super Yang-Mills from the Klebanov-Strassker-Tseytlin solution of supergravity and the proposed gauge/gravity duality. The calculation is performed numerically via searching world-sheet minimal surface. It is shown that Wilson loop exhibits area law for large radius which implies that ${\cal N}=1$ super Yang-Mills is confined at large distance or low energy scale. Meanwhile, Wilson loop exhibits logarithmic behavior for small radius and it indicates asymptotical freedom of ${\cal N}=1$ super Yang-Mills at short distance or high energy scale.

hep-th↗
arXiv2003

The Scale on Chiral Symmetry Breaking

We study the relation between the scale of chiral symmetry spontaneously breaking and constituent quark mass. We argue that this relation partly reveals strong interaction origination of chiral symmetry breaking. We show that the relation can be obtained via checking unitarity region of low-energy effective field theory of QCD. This effective field theory must manifestly include consistent quark mass as parameter. Thus we derive this effective field theory from naive chiral constituent quark model. The phenomenological value obtained by this method agree with usual one determined by pion decay constant.

hep-ph↗
arXiv2003

Green Functions of N=1 SYM and Radial/Energy-Scale Relation

We study counter-terms of one- and two-point Green functions of some special operators in ${\cal N}=1$ SYM from their SUGRA duals from the consideration of AdS/CFT or gauge/gravity correspondence. We consider both the Maldacena-Nunez solution and the Klebanov-Strassler-Tseytlin solution that are proposed to be SUGRA duals of ${\cal N}=1$ SYM. We obtain radial/energy-scale relation for each solution by comparing SUGRA calculations with the field theory results. Using these relations we evaluate the $β$-function of ${\cal N}=1$ SYM. We find that the leading order term can be accurately obtained for both solutions and the higher order terms exhibit some ambiguities. We discuss the origin of these ambiguities and conclude that more studies are needed to check whether these SUGRA solutions are exactly dual to ${\cal N}=1$ SYM.

hep-th↗
arXiv2003

Resummation Study on Decay $ρ\toππ$ in $U(2)_L\times U(2)_R$ Chiral Theory of Mesons

We improve $O(p^4)$ calculation in $U(2)_L\times U(2)_R$ chiral theory of mesons by resummation calculation for vector mesons physics and restudy decay $ρ\toππ$. A complete and compact expression for $f_{ρππ}(p^2)$ (up to $O(p^\infty)$) is obtained, from which an important non-perturbative conclusion is given based on convergence and unitarity consideration.

hep-ph↗
arXiv2002

Holography and (1+1)-dimension non-relativistic Quantum Mechanics

I generalize classical gravity/quantum gauge theory duality in AdS/CFT correspondence to (1+1)-dimensional non-relativistic quantum mechanical system. It is shown that (1+1)-dimensional non-relativistic quantum mechanical system can be reproduced from holographic projection of (2+1)-dimension classical gravity at semiclassical limit. In this explanation every quantum path in 2-dimension corresponds to a classical path of 3-dimension gravity under definite holographic projection. I consider free particle and harmonic oscillator as two examples and find their dual gravity description.

hep-th↗
arXiv2002

Resummation Studies on Vector Meson Decays and Chiral Symmetry Spontaneously Breaking in Chiral Constituent Quark Model

We study on-shell decays of light vector meson resonances $ρ$, $K^*$ and $ϕ$ in the framework of chiral constituent quark model using resummation calculations. Such studies are necessary for showing that chiral dynamics works well at this energy scale. The effective action is derived by proper vertex method, where resummation of all orders of momentum expansion is accomplished. The loop effects of pseudoscalar meson are also taken into account, which play an important role at this energy scale. The numerical results agree well with the experimental data. A new method to explore the Chiral Symmetry Spontaneously Breaking (CSSB) is proposed. It is found that the unitarity of the effective meson theory resulted from resummation derivations demands an upper-limit to the momentum of vector meson. This upper-limit, being critical point, is just the energy scale of CSSB, and is found to be flavor-dependent.

hep-ph↗
arXiv2002

Gauge/Gravity Duality, Green Functions of N=2 SYM and Radial/Energy-Scale Relation

We consider supergravity configuration of D5 branes wrapped on supersymmetric 2-cycles and use it to calculate one-point and two-point Green functions of some special operators in N=2 super Yang-Mills theory. We show that Green functions obtained from supergravity include two very different parts. One of them corresponds to perturbative results of quantum field theory, and another is a non-perturbative effect which corresponds to contribution from instantons with fractional charge. Comparing Green functions obtained from supergravity and gauge theory, we obtain radial/energy-scale relation for this gauge/gravity correspondence with N=2 supersymmetry. This relation leads right beta-function of N=2 SYM from supergravity configuration.

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