Manageable description of the cokernel controlling the first shifted twisted Witt group of a real surface

Characterize the cokernel of the connecting homomorphism \partial_L:H^0(X,\overline{I})\to H^1(X,I^2(L)) for a smooth real surface X and line bundle L, in a manageable general form that accounts for its interaction with H^1(X,K^2(L)).

Background

For a smooth real surface X and line bundle L, the paper studies W1(X,L) through the exact sequence involving H1(X,I2(L)), the connecting homomorphism \partial_L, and the kernel of the twisted Steenrod square \Sq_L2. A purely topological description analogous to the one available for the top shifted Witt group fails because the image of \partial_L can intersect H1(X,K2(L)) nontrivially.

The paper gives an explicit product-of-elliptic-curves example in which this intersection is nontrivial, showing that the obstruction cannot generally be captured solely by the real-locus topology. It nevertheless leaves unresolved whether the resulting cokernel admits a manageable description in general.

References

It is unclear to us whether one can expect a manageable description of \Coker\partial_L in general.

Witt groups of smooth real curves and surfaces  (2608.18599 - Lerbet, 19 Aug 2026) in Remark \ref{rema:no_analogue_W1_surfaces}, Section 5, subsection “Shifted Witt groups of surfaces”