Euclid NIR-H Dipole Preregistration Q2/Q3 2026

This preregistration documents the testable prediction derived from the empirical detection of a probable North–South dipole in the NIR-H flux tail index (Hill estimator, k = 50) in the Euclid MER Q1 public catalogue (Debailleul, Zenodo, 2026, DOI: 10.5281/zenodo.18861360). The contrast Δα ≈ 0.80 between North zones (ā_N ≈ 2.01, δ ≈ +60°) and South zones (ā_S ≈ 1.21, δ ≈ −26° to −50°) was obtained with zero free parameters, full methodological transparency, and survived six independent robustness tests. This preregistration formally declares the falsifiable prediction for Euclid Q2/Q3 data expected in October 2026, using the identical pipeline and identical threshold k = 50.