Transition between the Bjorken and GDH regimes

Characterize the transition between the perturbative Bjorken-sum-rule regime and the low-Q^2 GerasimovDrellHearn regime, which remains insufficiently understood.

Background

The paper discusses the Q2 dependence of the Bjorken sum rule across perturbative and nonperturbative momentum scales. At relatively high Q2, the behavior is described using perturbative QCD and the Bjorken sum rule, whereas at very low Q2 it is governed by the GerasimovDrellHearn sum rule. The intermediate transition between these descriptions is identified as an unresolved theoretical issue.

References

The transition between these two regimes is still not well understood.

— Bjorken sum rule down to the elastic region from the lattice  (2610.10006 - Crawford et al., 7 Oct 2026) in Section 1, Introduction