Introduction to non-Abelian Patchworking

This paper introduces the framework of non-Abelian patchworking, a geometric method for constructing real algebraic surfaces in RP3\mathbb{R}P^3 via the real locus of non-Abelian complex-phase tropical hypersurfaces, which successfully reproduces all isotopy types of surfaces up to degree three and reveals that primitive PGL2PGL_2 surfaces can exhibit Euler characteristics distinct from their complex counterparts.

Turgay Akyar, Mikhail Shkolnikov2026-03-10🔢 math

The W-footrule coefficient: A copula-based measure of countermonotonicity

This paper introduces the WW-footrule coefficient, a new copula-based measure of negative association defined as the L1L^1-distance to the countermonotonic copula, establishes its theoretical relationship with Gini's gamma and Spearman's footrule, and provides a statistically rigorous rank-based estimator with proven consistency and asymptotic normality.

Enrique de Amo, David García-Fernández, Manuel Úbeda-Flores2026-03-10🔢 math