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Abstract: The AdS-CFT correspondence between string theory in AdS space and conformalfield theories in physical space-time leads to an analytic, semi-classicalmodel for strongly-coupled QCD which has scale invariance and dimensionalcounting at short distances and color confinement at large distances. TheAdS-CFT correspondence also provides insights into the inherentlynonperturbative aspects of QCD such as the orbital and radial spectra ofhadrons and the form of hadronic wavefunctions. In particular, we show thatthere is an exact correspondence between the fifth-dimensional coordinate ofAdS space $z$ and a specific impact variable $\zeta$ which measures theseparation of the quark and gluonic constituents within the hadron in ordinaryspace-time. This connection leads to AdS-CFT predictions for the analytic formof the frame-independent light-front wavefunctions LFWFs of mesons andbaryons, the fundamental entities which encode hadron properties. The LFWFs inturn predict decay constants and spin correlations, as well as dynamicalquantities such as form factors, structure functions, generalized partondistributions, and exclusive scattering amplitudes. Relativistic light-frontequations in ordinary space-time are found which reproduce the results obtainedusing the fifth-dimensional theory and have remarkable algebraic structures andintegrability properties. As specific examples we describe the behavior of thepion form factor in the space and time-like regions and determine the Diracnucleon form factors in the space-like region. An extension to nonzero quarkmass is used to determine hadronic distribution amplitudes of all mesons, heavyand light. We compare our results with the moments of the distributionamplitudes which have recently been computed from lattice gauge theory.



Author: Stanley J. Brodsky, Guy F. de Teramond

Source: https://arxiv.org/







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