Isomorphism between the sign-twisted curve complex and the Lagrangian sphere complex of the intersection of two quadrics

Determine whether the simplicial injection from the non-separating subcomplex of the sign-twisted curve complex of the genus-two surface into the Lagrangian sphere complex of the intersection of two generic quadrics in [?]mathbb{CP}^5 is a simplicial isomorphism.

Background

For the genus-two odd character variety M2oddM_2^{\mathrm{odd}}, identified symplectically with the intersection Q1∩Q2Q_1\cap Q_2 of two generic quadrics in CP5\mathbb{CP}^5, the paper constructs a simplicial injection from the subcomplex N(Σ2)\mathcal N(\Sigma_2) of non-separating vertices in the sign-twisted curve complex to the Lagrangian sphere complex L(Q1∩Q2)\mathcal L(Q_1\cap Q_2).

The unresolved issue is whether every Lagrangian sphere in Q1∩Q2Q_1\cap Q_2 arises from a sign-twisted non-separating curve. The paper notes that this would follow from two additional results: an isomorphism for the analogue of the mapping-class-group homomorphism for M2oddM_2^{\mathrm{odd}}, and transitivity of the symplectomorphism group of Q1∩Q2Q_1\cap Q_2 on Lagrangian spheres up to symplectic isotopy. Neither assertion is established there.

References

A natural question is whether eq:genus2injectionintro is an isomorphism, similar to Theorem \ref{thm:lagrangianspheres}.

eq:genus2injectionintro:

N(Σ2)↪L(Q1∩Q2)\mathcal{N}(\Sigma_2) \hookrightarrow \mathcal{L}(Q_1\cap Q_2)

— On symplectic aspects of $SU(2)$ character varieties for punctured surfaces  (2609.28907 - Daemi et al., 24 Sep 2026) in Introduction, subsection [?]Lagrangian spheres in the intersection of two quadrics in \(\mathbb{CP}^5\), immediately following Theorem \ref{thm:lagrangianspheresinquadricintersection}