Problems related to gauge invariance and momentum, spin decomposition in nucleon structure study

Abstract

How do the quark and gluon share the nucleon momentum? How does the nucleon spin distribute among its constituents? What means the quark and gluon momentum, spin and orbital angular momentum? These problems are analyzed and a solution is proposed based on {\it gauge invariance principle, canonical quantization rule and Poincar$\acute{e}$ covariance}.

Comments: 10 pages, no figures; acknowledgement for the acceptance as an invited contribution to a special issue of Physics of Elementary Particles and Atomic Nuclei is added