Conjecture on twisted L-groups and Q-groups from algebraic Wu classes

Let (B,β)(B_*,\beta) be a chain bundle with algebraic Wu class v^2k(β)\widehat v_{2k}(\beta), and let ev\operatorname{ev} denote evaluation on homology. Let Σ\Sigma, Σ8\Sigma_8, Λ\Lambda, Coker\operatorname{Coker}, QQ^-, and ι1\iota_1 be the constructions defined in the source. Conjecture on twisted groups. If (B,β)(B_*,\beta) is (2k1)(2k-1)-connected, then

L4k(B,β)W0(Qβ(2k))Σ(ev(v^2k(β)))L^{4k}(B_*,\beta)\cong W_0(Q_\beta(2k))\cong\Sigma\bigl(\operatorname{ev}(\widehat v_{2k}(\beta))\bigr)

and

Q4k(B,β)Σ8(ev(v^2k(β))).Q_{4k}(B_*,\beta)\cong\Sigma_8\bigl(\operatorname{ev}(\widehat v_{2k}(\beta))\bigr).

If (B,β)(B_*,\beta) is (2k2)(2k-2)-connected and ev(v^2k(β))=0\operatorname{ev}(\widehat v_{2k}(\beta))=0, then [vQβ(2k1)]=v^2k(β)[v'_{Q_\beta(2k-1)}]=\widehat v_{2k}(\beta) and

L4k2(B,β)W0(Qβ(2k1))Λ(vQβ(2k1))L^{4k-2}(B_*,\beta)\cong W_0(Q_\beta(2k-1))\cong\Lambda(v'_{Q_\beta(2k-1)})

and

Q4k2(B,β)Coker(Λ(ι1)Λ(vQβ(2k1))).Q_{4k-2}(B_*,\beta)\cong\operatorname{Coker}\bigl(\Lambda(\iota_1)\to\Lambda(v'_{Q_\beta(2k-1)})\bigr).

If instead (B,β)(B_*,\beta) is (2k2)(2k-2)-connected and ev(v^2k(β))0\operatorname{ev}(\widehat v_{2k}(\beta))\neq0, then Qβ(2k1)QH2k1(B)Q_\beta(2k-1)\cong Q^-\oplus H_{2k-1}(B_*) and

L4k2(B,β)Q4k2(B,β)W0(Qβ(2k1))Λ(H2k1(B))L^{4k-2}(B_*,\beta)\cong Q_{4k-2}(B_*,\beta)\cong W_0(Q_\beta(2k-1))\cong\Lambda(H_{2k-1}(B_*))

The conjecture is presented as a consequence of the preceding conjecture, the proposition computing quasi-Wu classes, and the theorem computing Witt groups; the source supplies no resolution.

Sources & referencesView supporting material

Primary source

Diarmuid Crowley and Csaba Nagy, “The Witt groups of extended quadratic forms over Z”, arXiv:2404.09189 (2026).

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