Power Corrections in Deep Inelastic Scattering and Non-perturbative Light-front Dynamics

In this thesis, we have investigated the higher twist structure functions in the recently developed method based on light-front Hamiltonian QCD. Because of various special properties of light-front QCD, this is a more intuitive approach towards deep inelastic scattering but has a well defined field theoretic calculational procedure. Because our method is different from the conventional one, we have obtained various new results. Also, it is easier to explore many aspects which are difficult to understand in the conventional way. The structure functions, twist four $F_L$ and $g_T$ contain non-trivial interaction dependence in the operator structure and therefore involve quark-gluon dynamics. We have shown that the intergrals of these are directly related to the light-front Hamiltonian density and transverse spin operator respectively. These are non-perturbative relations. We have also renormalized the twist four longitudinal structure function and the full transverse spin operator respectively upto one loop in light-front Hamiltonian perturbation theory. We have investigated twist four $F_L$ for bound states like a meson in 1+1 dimensional QCD and for a positronium in 3+1 dimensional QED.