Mirror-duality conjecture for the two second Steenrod squares

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Let LL be a link and let L‾\overline{L} be its mirror. For ε∈Z/2Z\varepsilon\in \mathbb{Z}/2\mathbb{Z}, the Khovanov cohomology groups of LL and the dual groups of its mirror are related by the natural isomorphisms displayed in the diagram, with the second Steenrod square Sq⁡ε2\operatorname{Sq}^2_\varepsilon on the left and the dual of Sq⁡1+ε2\operatorname{Sq}^2_{1+\varepsilon} on the right.

Mirror-duality conjecture. The diagram

\begin{tikzpicture} \node at (0,2) {$\operatorname{Kh}^{i,j}(L;\mathbb{Z}/2\mathbb{Z})$}; \node at (5.6,2) {$\operatorname{Hom}(\operatorname{Kh}^{-i,-j}(\overline{L};\mathbb{Z}/2\mathbb{Z}),\mathbb{Z}/2\mathbb{Z})$}; \node at (0,0) {$\operatorname{Kh}^{i+2,j}(L;\mathbb{Z}/2\mathbb{Z})$}; \node at (5.6,0) {$\operatorname{Hom}(\operatorname{Kh}^{-i-2,-j}(\overline{L};\mathbb{Z}/2\mathbb{Z}),\mathbb{Z}/2\mathbb{Z})$}; \draw[->] (1.35,2) -- node[above] {$\cong$} (3,2); \draw[->] (1.5,0) -- node[above] {$\cong$} (2.8,0); \draw[->] (0,1.7) -- node[\right] {$\operatorname{Sq}^2_\varepsilon$} (0,0.3); \draw[->] (5.6,1.7) -- node[\right] {$(\operatorname{Sq}^2_{1+\varepsilon})^\ast$} (5.6,0.3); \end{tikzpicture}

commutes. Here the right vertical map is the dual of the second Steenrod square indexed by 1+ε1+\varepsilon.

This conjecture proposes the Spanier--Whitehead duality behavior for the two second Steenrod squares, extending the known duality relation for the Lipshitz--Sarkar stable homotopy type. The claimed behavior was confirmed by calculations for links in the Rolfsen table, but its validity for arbitrary links remains open.

References

Primary source

Dirk Schuetz, “Two second Steenrod squares for odd Khovanov homology”, arXiv:2209.00389 (2025).

Additional references

2 papers in this index state this conjecture (2003–2022). The statement above is taken from the most recent of them; the others are arXiv:math/0312417.

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