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The relativistic light-front dynamics (LFD) method has been shown to give a correct description of the most recent data for the deuteron monopole and quadrupole charge form factors obtained at the Jefferson Laboratory for elastic electron-deuteron scattering for six values of the squared momentum transfer between 0.66 and 1.7 (GeV/c) 2 . The good agreement with the data is in contrast with the results of the existing non-relativistic approaches.In this work we firstly make a complementary test of the LFD applying it to calculate another important characteristic, the nucleon momentum distribution n(q) of the deuteron using six invariant functions fi (i = 1, ..., 6) instead of two (S-and D-waves) in the nonrelativistic case. The comparison with the y-scaling data shows the decisive role of the function f5 which at q ≥ 500 MeV/c exceeds all other f -functions (as well as the S-and D-waves) for the correct description of n(q) of the deuteron in the high-momentum region. Comparison with other calculations using S-and D-waves corresponding to various nucleon-nucleon potentials is made. Secondly, using clear indications that the high-momentum components of n(q) in heavier nuclei are related to those in the deuteron, we develop an approach within the natural orbital representation to calculate n(q) in (A, Z)-nuclei on the basis of the deuteron momentum distribution. As examples, n(q) in 4 He, 12 C and 56 Fe are calculated and good agreement with the y-scaling data is obtained.

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The nonrelativistic full-folding optical model approach for nucleon-nucleus scattering is extended into the relativistic regime. In doing so, kinematical issues involving the off-shell Lorentz boost of the colliding particles between the two nucleons and the projectile-nucleus center-of-mass reference frames have been taken into account. The two-body effective interaction is obtained in the framework of the nuclear matter g-matrix using nucleon-nucleon optical model potentials that fully account for the inelasticities and isobar resonances in the continuum at nucleon energies up to 3 GeV. Diverse nucleon-nucleon potential models were constructed by supplementing the basic Paris, Nijmegen, Argonne or Gel'fand-Levitan-Marchenko inversion potentials with complex separable terms. In each case the additional separable terms ensured that the combination led to NN scattering phase shifts in excellent agreement with experimental values. With each phase shift fitting potential nuclear matter g-matrices have been formed and with each of those relativistic full-folding optical potentials for nucleon-nucleus elastic scattering determined. Application to such scattering for projectile energies to 1.5 GeV have been made. Good and systematic agreement is obtained between the calculated and measured observables, both differential and integrated quantities, over the whole energy range of our study. A moderate sensitivity to off-shell effects in the differential scattering observables also is observed.