# QCD and Light-Front Holography

## Abstract

The soft-wall AdS/QCD model, modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics. The model predicts a zero-mass pion for zero-mass quarks and a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number N. Light-Front Holography maps the amplitudes which are functions of the fifth dimension variable z of anti-de Sitter space to a corresponding hadron theory quantized on the light front. The resulting Lorentz-invariant relativistic light-front wave equations are functions of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. The result is to a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryon light-quark bound states, which in turn predict the behavior of the pion and nucleon form factors. The theory implements chiral symmetry in a novel way: the effects of chiral symmetry breaking increase as one goes toward large interquark separation, consistent with spectroscopic data, and the the hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks hasmore »

- Authors:

- Publication Date:

- Research Org.:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC)

- OSTI Identifier:
- 992880

- Report Number(s):
- SLAC-PUB-14258

arXiv:1009.4232; TRN: US1007913

- DOE Contract Number:
- AC02-76SF00515

- Resource Type:
- Conference

- Journal Name:
- Acta Phys.Polon.B41:2605-2643,2010

- Additional Journal Information:
- Conference: Invited talk at 50th Cracow School of Theoretical Physics: Developments in particle physics from a 50 year perspective of the Cracow School, Zakopane, Poland, 9-19 Jun 2010

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; AMPLITUDES; BARYONS; BOUND STATE; CHIRAL SYMMETRY; EIGENSTATES; FORM FACTORS; GLUONS; HADRONS; HOLOGRAPHY; MESONS; NUCLEONS; ORBITAL ANGULAR MOMENTUM; PIONS; PROTONS; QUANTUM CHROMODYNAMICS; QUANTUM NUMBERS; QUARKS; SPECTRA; SUM RULES; WAVE EQUATIONS; Phenomenology-HEP, Theory-HEP,HEPPH, HEPTH

### Citation Formats

```
Brodsky, Stanley J., /SLAC /Southern Denmark U., CP3-Origins, de Teramond, Guy F., and /Costa Rica U.
```*QCD and Light-Front Holography*. United States: N. p., 2010.
Web.

```
Brodsky, Stanley J., /SLAC /Southern Denmark U., CP3-Origins, de Teramond, Guy F., & /Costa Rica U.
```*QCD and Light-Front Holography*. United States.

```
Brodsky, Stanley J., /SLAC /Southern Denmark U., CP3-Origins, de Teramond, Guy F., and /Costa Rica U. Wed .
"QCD and Light-Front Holography". United States. https://www.osti.gov/servlets/purl/992880.
```

```
@article{osti_992880,
```

title = {QCD and Light-Front Holography},

author = {Brodsky, Stanley J. and /SLAC /Southern Denmark U., CP3-Origins and de Teramond, Guy F. and /Costa Rica U.},

abstractNote = {The soft-wall AdS/QCD model, modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics. The model predicts a zero-mass pion for zero-mass quarks and a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number N. Light-Front Holography maps the amplitudes which are functions of the fifth dimension variable z of anti-de Sitter space to a corresponding hadron theory quantized on the light front. The resulting Lorentz-invariant relativistic light-front wave equations are functions of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. The result is to a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryon light-quark bound states, which in turn predict the behavior of the pion and nucleon form factors. The theory implements chiral symmetry in a novel way: the effects of chiral symmetry breaking increase as one goes toward large interquark separation, consistent with spectroscopic data, and the the hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. The soft-wall model also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function which agrees with the effective coupling {alpha}{sub g1} extracted from the Bjorken sum rule. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also reviewed.},

doi = {},

journal = {Acta Phys.Polon.B41:2605-2643,2010},

number = ,

volume = ,

place = {United States},

year = {2010},

month = {10}

}