PreprintCC BYHAL
Depth of free-by-cyclic groups
Abstract
For a free group automorphism, we prove that its poset of attracting lamination orbits is a canonical invariant of the associated mapping torus. That is, if a free-by-cyclic group splits as a mapping torus in two different ways, then the corresponding automorphisms have isomorphic posets of lamination orbits. Further, we show that the lamination depth, the size of the largest chain in this poset, is a commensurability invariant of the free-by-cyclic group.
Related
- Finite index rigidity of free-by-cyclic groups
- The Diophantine Problem with constraints in some free-by-cyclic groups
- Finiteness properties of centralisers in Out(FN) and automorphisms of free-by-cyclic groups
- Conjugator Length in Iterated Cyclic Amalgams of Free Groups
- Fuglede's Conjecture for Cyclic Groups of Square-free Order
BibTeX
@misc{dowdall2026depth,
title = {{Depth of free-by-cyclic groups}},
author = {Spencer Dowdall and Yassine Guerch and Radhika Gupta and Jean Pierre Mutanguha and Caglar Uyanik},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2602.10433},
eprint = {2602.10433},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05798895v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Depth of free-by-cyclic groups
AU - Spencer Dowdall
AU - Yassine Guerch
AU - Radhika Gupta
AU - Jean Pierre Mutanguha
AU - Caglar Uyanik
PY - 2026
DA - 2026/10/14
PB - HAL
DO - 10.48550/arxiv.2602.10433
UR - https://hal.science/hal-05798895v1
AB - For a free group automorphism, we prove that its poset of attracting lamination orbits is a canonical invariant of the associated mapping torus. That is, if a free-by-cyclic group splits as a mapping torus in two different ways, then the corresponding automorphisms have isomorphic posets of lamination orbits. Further, we show that the lamination depth, the size of the largest chain in this poset, is a commensurability invariant of the free-by-cyclic group.
ER -