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Poincaré polynomials for skein lasagna modules of CP^2

Determine the Poincaré polynomials of the Khovanov skein lasagna modules S^2_0(CP^2;0;Q) and S^2_0(CP^2;1;Q) as the explicit infinite series specified by Conjecture 6.14: S^2_0(CP^2;0;Q) has polynomial 1 + \sum_{n≥1} t^{−2n^2} q^{6n^2−4n+1} K_{2n}(t,q^2) − 1, and S^2_0(CP^2;1;Q) has polynomial \sum_{n≥1} t^{−2n^2+2n} q^{6n^2−10n+4} K_{2n−1}(t,q^2) − 1, where K_n(t,q) denotes the Poincaré polynomial of Kh(T(n,n−1);Q).

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Background

A central computational goal in the paper is to understand S2_0(CP2), which plays a key role in constructing induced maps on Khovanov homology for cobordisms in kCP2 and in embedding obstructions.

Conjecture 6.14 proposes exact closed-form series for the Poincaré polynomials of S2_0(CP2;0;Q) and S2_0(CP2;1;Q) expressed via the Poincaré polynomials of Khovanov homology for the torus links T(n,n−1). The authors have verified compatibility with known data for small n, and resolving this conjecture would effectively determine S2_0(CP2).

References

Conjecture 6.14. Let K (t,q)ndenote the Poincar´ e polynomial of Kh(T(n,n − 1);Q) for n > 0. Then S (0P ;0;Q) has Poincar´ e polynomial ∞ 1+ t−2n2 q6n −4n+1K (t,q ) −1 (38) ∑ 2n n=1 and S 0P ;1;Q) has Poincar´ e polynomial ∞ −2n +2n 6n −10n+4 −1 ∑ t q K 2n−1 (t,q ). (39)

Khovanov homology and exotic $4$-manifolds (2402.10452 - Ren et al., 16 Feb 2024) in Section 6.9 (Conjecture 6.14)