English

On quasi-arithmeticity of hyperbolic gluings

Geometric Topology 2025-07-18 v3 Group Theory Number Theory

Abstract

We study a more general version of the gluings of hyperbolic orbifolds in the spirit of Gromov and Piatetski-Shapiro, where the gluing pieces, called the building blocks, are no longer assumed to be arithmetic or incommensurable. We prove that if such a general hyperbolic gluing along a common finite-volume totally geodesic hypersurface is quasi-arithmetic (this is a broader notion than that of arithmeticity) then each building block must be quasi-arithmetic as well and, moreover, with the same ambient group and adjoint trace field. We also show that there exist arithmetic gluings whose building blocks are incommensurable even despite the reflection with respect to the lift of the gluing locus commensurates the fundamental group of the gluing. On the other hand, we provide an example of nonarithmetic but quasi-arithmetic orbifolds such that a specific gluing of such an orbifold with itself along the boundary gives rise to an arithmetic hyperbolic orbifold. We illustrate the above results in the setting of reflection groups and hyperbolic Coxeter polyhedra and apply them to rule out the (quasi-)arithmeticity of a family of ideal hyperbolic right-angled 33-polyhedra, namely, certain ``twisted'' ideal right-angled antiprisms, which play an important role in low-dimensional geometry and topology.

Keywords

Cite

@article{arxiv.2307.07000,
  title  = {On quasi-arithmeticity of hyperbolic gluings},
  author = {Nikolay Bogachev and Dmitry Guschin and Andrei Vesnin},
  journal= {arXiv preprint arXiv:2307.07000},
  year   = {2025}
}

Comments

28 pages, 8 figures, significant improvement of the exposition: the title changed, main results were generalized and improved, some wrong claims fixed, new examples provided