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Splitting of the SKK short exact sequence in odd dimensions for all twice-stabilised tangential structures

Prove that for every twice stabilised tangential structure ξ and every odd dimension n, the short exact sequence 0 → ⟨S_b^n⟩_{SKK_n} → SKK_n^{ξ} → Ω_n^{ξ} → 0 splits.

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Background

The paper establishes a short exact sequence relating SKK-groups to bordism groups, with kernel generated by the bounding sphere. In many odd-dimensional cases the authors construct splittings using the Kervaire semi-characteristic and other tools. Motivated by their systematic positive results across numerous tangential structures, they propose a general conjecture asserting that the short exact sequence should always split in odd dimensions once the structure is twice stabilised.

References

Conjecture. For every twice stabilised structure ξ and every odd dimension n, the \ref{SKKseq} is split.

SKK groups of manifolds and non-unitary invertible TQFTs (2504.07917 - Hoekzema et al., 10 Apr 2025) in Conjecture, Section “Splitting results for odd-dimensional SKK groups”