A primary question in hadron physics is how the mass scale for hadronsconsisting of light quarks, such as the proton, emerges from the QCD Lagrangianeven in the limit of zero quark mass. If one requires the effective actionwhich underlies the QCD Lagrangian to remain conformally invariant and extendsthe formalism of de Alfaro, Fubini and Furlan to light-front Hamiltoniantheory, then a unique, color-confining potential with a mass parameter $\kappa$emerges. The actual value of the parameter $\kappa$ is not set by the model -only ratios of hadron masses and other hadronic mass scales are predicted. Theresult is a nonperturbative, relativistic light-front quantum mechanical waveequation, the Light-Front Schr\"odinger Equation which incorporates colorconfinement and other essential spectroscopic and dynamical features of hadronphysics, including a massless pion for zero quark mass and linear Reggetrajectories with the identical slope in the radial quantum number $n$ andorbital angular momentum $L$. The same light-front equations for mesons withspin $J$ also can be derived from the holographic mapping to QCD (3+1) at fixedlight-front time from the soft-wall model modification of AdS$_5$ space with aspecific dilaton profile. Light-front holography thus provides a preciserelation between the bound-state amplitudes in the fifth dimension of AdS spaceand the boost-invariant light-front wavefunctions describing the internalstructure of hadrons in physical space-time. One can also extend the analysisto baryons using superconformal algebra - $2 \times 2$ supersymmetricrepresentations of the conformal group. The resulting fermionic LF bound-stateequations predict striking similarities between the meson and baryon spectra.In fact, the holographic QCD light-front Hamiltonians for the states on themeson and baryon trajectories are identical if one shifts the internalangular...
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