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

Extreme value theorem for geodesic flow on the quotient of the theta group

This paper establishes an extreme value theorem for the geodesic flow on the hyperbolic surface associated with the theta group by introducing a spliced continued fraction algorithm, proving its dynamical equivalence to the flow's first return map, and deriving a Galambos-type extreme value law for maximal cusp excursions via spectral analysis of the transfer operator.

Jaelin Kim, Seul Bee Lee, Seonhee LimTue, 10 Ma🔢 math