The Witten-Sakai-Sugimoto model: A brief review and some recent results

Rebhan, Anton

doi:10.1051/epjconf/20149502005

Cited by 4 publications

(4 citation statements)

References 96 publications

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“…26 We weight with the model values rather than the errors because the experimental ones are tiny, while the theoretical ones are difficult to estimate reliably. 27 Note that a very similar value for λ was advocated in [51] to have a good fit of the ratio of the ρ meson mass and the (square root of) the string tension.…”

Section: Jhep02(2017)029mentioning

confidence: 94%

Theta dependence in holographic QCD

Bartolini

Bigazzi

Bolognesi

et al. 2017

J. High Energ. Phys.

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Abstract:We study the effects of the CP-breaking topological θ-term in the large N c QCD model by Witten, Sakai and Sugimoto with N f degenerate light flavors. We first compute the ground state energy density, the topological susceptibility and the masses of the lowest lying mesons, finding agreement with expectations from the QCD chiral effective action. Then, focusing on the N f = 2 case, we consider the baryonic sector and determine, to leading order in the small θ regime, the related holographic instantonic soliton solutions. We find that while the baryon spectrum does not receive O(θ) corrections, this is not the case for observables like the electromagnetic form factor of the nucleons. In particular, it exhibits a dipole term, which turns out to be vector-meson dominated. The resulting neutron electric dipole moment, which is exactly the opposite as that of the proton, is of the same order of magnitude of previous estimates in the literature. Finally, we compute the CP-violating pion-nucleon coupling constantḡ πN N , finding that it is zero to leading order in the large N c limit.

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Section: Jhep02(2017)029mentioning

confidence: 94%

Theta dependence in holographic QCD

Bartolini

Bigazzi

Bolognesi

et al. 2017

J. High Energ. Phys.

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“…As reviewed in [27], this model works also remarkably well quantitatively. Fixing M KK by the ρ meson mass and varying λ = 16.63 .…”

Section: Pos(cd15)124mentioning

confidence: 55%

Glueball decay in the Witten-Sakai-Sugimoto model

Brünner¹,

Rebhan²

2016

Proceedings of the 8th International Workshop on Chiral Dynamics — PoS(CD15)

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We discuss recent results on the calculation of glueball decay rates in the Witten-Sakai-Sugimoto model, which favor the f 0 (1710) meson as a glueball candidate. The flavor asymmetric decay of f 0 (1710) is frequently attributed to a putative chiral suppression in glueball decays, which is however questionable in view of the large constituent quark masses induced by chiral symmetry breaking. We find that this can be explained by what we call nonchiral enhancement when finite quark masses are included in the holographic model, with good quantitative agreement with experimental data for f 0 (1710). Assuming the latter to indeed be a nearly pure glueball, the model makes essentially parameter-free and thus falsifiable predictions for its decay rates involving vector mesons and an upper limit on the ηη decay rate.

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“…1. The gauge configuration is defined by the gauge field A AE defined on 6 The axial Uð1Þ subgroup of UðN f Þ L × UðN f Þ R is anomalous. This anomaly can also be seen in string theory as discussed in [5], but we will not discuss it here.…”

Section: B Problems Of the Cs Termmentioning

confidence: 99%

“…, denoted as Aj z→AE∞ ð¼ lim z→AE∞ A μ dx μ Þ, are interpreted as the external gauge fields associated with the chiral symmetry UðN f Þ L × UðN f Þ R in QCD. 6 More precisely, we set A AE ¼ Aj z→AE∞ , whereÂ þ andÂ − are the external gauge fields associated with UðN f Þ R and UðN f Þ L , respectively. Because the gauge field at the boundary is fixed, the gauge symmetry of the system consists of the gauge transformation that acts trivially at the boundaries.…”

mentioning

confidence: 99%

Chern-Simons five-form and holographic baryons

Lau

Sugimoto

2017

Phys. Rev. D

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In the top-down holographic model of QCD based on D4/D8-branes in type IIA string theory and some of the bottom-up models, the low energy effective theory of mesons is described by a five-dimensional Yang-Mills-Chern-Simons theory in a certain curved background with two boundaries. The fivedimensional Chern-Simons term plays a crucial role in reproducing the correct chiral anomaly in fourdimensional massless QCD. However, there are some subtle ambiguities in the definition of the Chern-Simons term for the cases with topologically nontrivial gauge bundles, which include the configurations with baryons. In particular, for the cases with three flavors, it was pointed out by Hata and Murata that the naive Chern-Simons term does not lead to an important constraint on the baryon spectrum, which is needed to pick out the correct baryon spectrum observed in nature. In this paper, we propose a formulation of a well-defined Chern-Simons term which can be used for the cases with baryons, and show that it recovers the correct baryon constraint as well as the chiral anomaly in QCD.

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The Witten-Sakai-Sugimoto model: A brief review and some recent results

Cited by 4 publications

References 96 publications

Theta dependence in holographic QCD

Theta dependence in holographic QCD

Glueball decay in the Witten-Sakai-Sugimoto model

Chern-Simons five-form and holographic baryons

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