The codimension-two spin-genus representation conjecture for quadratic forms
Let and be integral quadratic forms with , and let
Assume that is primitively represented by an element of the spin genus of , and that . Codimension-two spin-genus representation conjecture. There exists a constant such that
implies that is primitively represented by . The local representation and minimum conditions are insufficient in codimension two because of spinor obstructions; the conjecture addresses whether the spin-genus condition becomes sufficient for sufficiently large minimum. Its case, concerning primitive representations of integers, has been established by Duke and Schulze-Pillot using estimates for Fourier coefficients of half-integral-weight forms, so the general statement is resolved only in that special case.
References
Primary source
Wooyeon Kim, Andreas Wieser and Pengyu Yang, “Representations of binary quadratic forms by quaternary quadratic forms”, arXiv:2604.19437 (2026).
Additional references
2 papers in this index state this conjecture (2025–2026). The statement above is taken from the most recent of them; the others are arXiv:2511.22877.
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