Stability in the homology of congruence subgroups

Abstract

The homology groups of many natural sequences of groups $\{G_n{\}}_{n=1}^{\infty }$ (e.g. general linear groups, mapping class groups, etc.) stabilize as $n\to \infty$. Indeed, there is a well-known machine for proving such results that goes back to early work of Quillen. Church and Farb discovered that many sequences of groups whose homology groups do not stabilize in the classical sense actually stabilize in some sense as representations. They called this phenomena representation stability. We prove that the homology groups of congruence subgroups of $G{L}_n(R)$ (for almost any reasonable ring $R$) satisfy a strong version of representation stability that we call central stability. The definition of central stability is very different from Church-Farb's definition of representation stability (it is defined via a universal property), but we prove that it implies representation stability. Our main tool is a new machine for proving central stability that is analogous to the classical homological stability machine.

26 pages; to appear in Invent. Math

Cited by in corpus (13)

• Representation stability and finite linear groups
• Homology of FI-modules
• Central stability for the homology of congruence subgroups and the second homology of Torelli groups
• Higher order representation stability and ordered configuration spaces of manifolds
• Stability in the high-dimensional cohomology of congruence subgroups
• Generating the Johnson filtration
• Central stability homology
• Stability in the homology of unipotent groups
• Categorifications of rational Hilbert series and characters of $F{S}^{op}$ modules
• Equivariant group presentations and the second homology group of the Torelli group
• Polynomial conditions and homology of FI-modules
• Regularity and stable ranges of FI-modules
• Higher representation stability for ordered configuration spaces and twisted commutative factorization algebras