Pure-Axial Weyl Invariance and Nieh–Yan Spin Holonomy

This paper gives an explicit Nieh--Yan realization of torsionful twistor transport. On cylindrical and warped Riemann--Cartan backgrounds, the torsionful transport holonomy is computed in closed form and checked against the Nieh--Yan boundary invariant. The result provides a concrete background-level companion to the abstract T-series classification of torsionful α\alphaα-surface transport and hidden quadratic obstruction mechanisms.