Finiteness of specializations of the qq-deformed modular group at roots of unity

This paper establishes that the qq-deformed modular group PSLq(2,Z)\operatorname{PSL}_q(2,{\mathbb Z}) specializes to a finite group at a complex parameter ζ\zeta if and only if ζ\zeta is a primitive nn-th root of unity for n{2,3,4,5}n \in \{2,3,4,5\}, in which cases the resulting groups are isomorphic to specific binary polyhedral groups, while the case n=6n=6 yields an infinite but "mild" structure with applications to Jones polynomials.

Takuma Byakuno, Xin Ren, Kohji YanagawaTue, 10 Ma🔢 math

On Representing Matroids via Modular Independence

This paper introduces a matrix-based notion of matroid representation over local commutative rings using modular independence, establishing conditions under which this system forms a matroid, deriving structural properties for codes over chain rings, and demonstrating that certain non-field-representable matroids, such as the Vámos matroid, can be represented over rings like Z/8Z\mathbb{Z}/8\mathbb{Z}.

Koji Imamura, Keisuke ShiromotoTue, 10 Ma🔢 math