Broken scale invariance, massless dilaton and confinement in QCD

Kharzeev, Dmitri E.; Levin, E.; Tuchin, Kirill

doi:10.1088/1126-6708/2009/06/055

Cited by 12 publications

(10 citation statements)

References 47 publications

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“…The dAFF mechanism is reminiscent of spontaneous symmetry breaking, however, this is not the case since there are no degenerate vacua [27] and thus a massless scalar 0 ++ state is not required. The dAFF mechanism is also different from usual explicit breaking by just adding a term to the Lagrangian [28].…”

Section: Discussionmentioning

confidence: 99%

Threefold complementary approach to holographic QCD

2014

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A complementary approach, derived from (a) higher-dimensional anti-de Sitter (AdS) space, (b) light-front quantization and (c) the invariance properties of the full conformal group in one dimension leads to a nonperturbative relativistic lightfront wave equation which incorporates essential spectroscopic and dynamical features of hadron physics. The fundamental conformal symmetry of the classical QCD Lagrangian in the limit of massless quarks is encoded in the resulting effective theory. The mass scale for confinement emerges from the isomorphism between the conformal group and SO(2, 1). This scale appears in the light-front Hamiltonian by mapping to the evolution operator in the formalism of de Alfaro, Fubini and Furlan, which retains the conformal invariance of the action. Remarkably, the specific form of the confinement interaction and the corresponding modification of AdS space are uniquely determined in this procedure.

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Section: Discussionmentioning

confidence: 99%

Threefold complementary approach to holographic QCD

2014

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“…The symmetry breaking in this procedure is reminiscent of spontaneous symmetry breaking, however, this is not the case since, in contrast with current algebra, there are no degenerate vacua [172] (the vacuum state is chosen ab initio) and thus a massless scalar 0 ++ state is not required. The dAFF mechanism is also different from usual explicit breaking by just adding a mass term to the Lagrangian [174].…”

Section: Connection To Light-front Dynamicsmentioning

confidence: 99%

Light-front holographic QCD and emerging confinement

et al. 2015

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a b s t r a c tIn this report we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. The light-front holographic methods described here give a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical space-time. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large q 2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low q 2 the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.

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“…On the other hand, the effective Lagrangian for pure gluon system can also be constructed in terms of lightest glueball [77][78][79] or one scalar particle -dilaton [80][81][82][83][84][85]. The dilaton field is an hypothetical scalar particle predicted by string theory and Kaluza-Klein type theories, and its expectation value probes the strength of the gauge coupling.…”

Section: Pure Gluon System: Quenched Dynamical Soft-wall Holographic mentioning

confidence: 99%

Dynamical holographic QCD model for glueball and light meson spectra

Huang

2013

J. High Energ. Phys.

134

112

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In this work, we offer a dynamical soft-wall model to describe the gluodynamics and chiral dynamics in one systematical framework. We firstly construct a quenched dynamical holographic QCD (hQCD) model in the graviton-dilaton framework for the pure gluon system, then develop a dynamical hQCD model for the two flavor system in the graviton-dilaton-scalar framework by adding light flavors on the gluodynamical background. For two forms of dilaton background field $\Phi=\mu_G^2z^2$ and $\Phi=\mu_G^2z^2\tanh(\mu_{G^2}^4z^2/\mu_G^2)$, the quadratic correction to dilaton background field at infrared encodes important non-perturbative gluodynamics and naturally induces a deformed warp factor of the metric. By self-consistently solving the deformed metric induced by the dilaton background field, we find that the scalar glueball spectra in the quenched dynamical model is in very well agreement with lattice data. For two flavor system in the graviton-dilaton-scalar framework, the deformed metric is self-consistently solved by considering both the chiral condensate and nonperturbative gluodynamics in the vacuum, which are responsible for the chiral symmetry breaking and linear confinement, respectively. It is found that the mixing between the chiral condensate and gluon condensate is important to produce the correct light flavor meson spectra. The pion form factor and the vector couplings are also investigated in the dynamical hQCD model. Besides, we give the criteria for the existence of linear quark potential from the metric structure, and show a negative quadratic dilaton background field is not favored in the graviton-dilaton framework.Comment: 49 pages, 23 figures, version accepted by JHE

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Broken scale invariance, massless dilaton and confinement in QCD

Cited by 12 publications

References 47 publications

Threefold complementary approach to holographic QCD

Threefold complementary approach to holographic QCD

Light-front holographic QCD and emerging confinement

Dynamical holographic QCD model for glueball and light meson spectra

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