Poincaré Duality, Degeneracy, and Real Lefschetz Property for T-Hypersurfaces

In Bounding the Betti Numbers of Real Hypersurfaces near the Tropical Limit, [RS23], A. Renaudineau and K. Shaw presented a filtration of the cellular complex of a real, primitively patchworked, hypersurface in a non-singular toric variety. This filtration, inspired by the work of Kalinin, allows, by computation of the first page of its induced spectral sequence, for individual bounds on the Betti numbers of such a hypersurface. We present two structural results about this spectral sequence. The first is a Poincaré duality satisfied by all its pages of positive index. The second is a vanishing criterion. It reformulates the vanishing of the boundary operators of the spectral sequence in terms of homological properties of the inclusion of the hypersurface in its surrounding toric variety. It implies further that the Renaudineau-Shaw spectral sequence of a T-hypersurface degenerates at the second page if and only if the T-hypersurface satisfies a real version of the Lefschetz hyperplane section theorem. As a consequence the spectral sequence of an odd degree T-hypersurface in a projective space always degenerates at the second page. Acknowledgements : This research was funded, in whole or in part, by l'Agence Nationale de la Recherche (ANR), project ANR-22-CE40-0014. For the purpose of open access, the author has applied a CC-BY public copyright licence to any Author Accepted Manuscript (AAM) version arising from this submission.