Spin Phenomena in Quantum Chromodynamics

The theory of spin effects (with the particular emphasis on T-odd ones) in QCD and its development in JINR is reviewed, including some personal recollections on the joint work with A.V. Efremov. The analysis of the sources of imaginary phases and respective cuts in hadronic kinematic variables leads to the effective character (non-universality) of T-odd distribution functions, contrary to universality of T-odd fragmentation functions. In particular, the model calculations of DIS with explicit T-violations can be used to predict the oscillations of T-odd polarizing fragmentation function. The comparison of polarization effects in hadronic and heavy-ion collisions is addressed.