English

The classification of Rank 3 Reflective Hyperbolic Lattices over Z[\sqrt{2}]

Group Theory 2017-02-23 v1

Abstract

There are 432 strongly squarefree symmetric bilinear forms of signature (2,1)(2,1) defined over Z[2]\Z[\sqrt{2}] whose integral isometry groups are generated up to finite index by finitely many reflections. We adapted Allcock's method (based on Nikulin's) of analysis for the 22-dimensional Weyl chamber to the real quadratic setting, and used it to produce a finite list of quadratic forms which contains all of the ones of interest to us as a sub-list. The standard method for determining whether a hyperbolic reflection group is generated up to finite index by reflections is an algorithm of Vinberg. However, for a large number of our quadratic forms the computation time required by Vinberg's algorithm was too long. We invented some alternatives, which we present here.

Keywords

Cite

@article{arxiv.1512.01133,
  title  = {The classification of Rank 3 Reflective Hyperbolic Lattices over Z[\sqrt{2}]},
  author = {Alice Mark},
  journal= {arXiv preprint arXiv:1512.01133},
  year   = {2017}
}

Comments

The first 40 pages or so are the paper. The rest of it is a giant table