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R25 · The odd-unimodular gluing correction (reverses R24)
RCHM × Hodge Research Round
R25 · The odd-unimodular gluing correction (reverses R24)
Odd-Unimodular Gluing Correction for Küchle c5: the Integral K3^[2] Primitive Lattice Reopens
The middle lattice of c5 is odd unimodular of signature (24,2); the hard complement T is even (the Wu class lies in the inherited sector); Milgram/Brown selection fixes the quadratic refinement so that −T is isometric to the primitive lattice of a degree-4, divisibility-1 K3^[2] polarization (Nikulin uniqueness) — the direct integral lattice template reopens; period realization and an algebraic correspondence remain open.
R25 reverses R24's negative conclusion: the direct integral lattice bridge is not obstructed; what remains is geometric.
This lattice-theoretic chain is internally exact but unreviewed; the geometric inputs (Kuznetsov numbers, blow-up pushforwards, the Wu-class argument) are hand-derived and only the arithmetic is machine-checked; the paper hedges it as 'not yet an algebraic-correspondence theorem'.
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