Positive Characteristic Invariants via the Han-Monsky Representation Ring

Objective

The study of numerical invariants in characteristic p, such as the F-threshold, diagonal F-threshold, and F-signature, is closely related to the theory of F-singularities and has recently attracted growing attention in both commutative algebra and algebraic geometry. Unexpected connections have emerged between these invariants and other topics of independent interest, such as the cohomology of line bundles on flag varieties, the Han-Monsky representation ring, and the Lefschetz property in positive characteristic. This project aims to investigate these connections in depth, with the goal of achieving a comprehensive understanding of the Han-Monsky representation ring and using this knowledge to advance the study of invariants in characteristic p and the Weak Lefschetz Property. On one hand, the Fellow will focus on invariants in positive characteristic, with the objective of computing the diagonal F-threshold for classes of square-free hypersurfaces with underlying combinatorial structure. In particular, attention will be given to the cone over the Grassmannian Gr(2,4) and to hypersurfaces defined by spanning tree polynomials. In parallel, the researcher will study the graded Han-Monsky ring, aiming to prove a recursive formula for its multiplication in characteristic p>0. This result will then be applied to classify the Weak Lefschetz Property for monomial complete intersections in three or more variables. The two directions will eventually converge in the final research objective: use the Han-Monsky framework to refine the understanding of the F-signature of Fermat hypersurfaces. More broadly, this aims to establish a methodology for advancing the study of invariants such as the F-signature and the diagonal F-threshold. PrIMes will be hosted by the Università degli Studi di Genova and CIMAT (Mexico), leveraging the different expertise of the Supervisors and the Fellow to ensure the success of the goals of the Action.