A simplification of "Effective quasimorphisms on right-angled Artin groups"

Abstract

This paper presents a simplification of the main argument in "Effective quasimorphisms on right-angled Artin groups" by Fern\'os, Forester and Tao. Their article introduces a family of quasimorphisms on a certain class of groups (called RAAG-like) acting on CAT(0) cube complexes. They show that these have uniform defect of $12$ and take the value of at least $1$ on a chosen element. With the Bavard Duality they conclude that hyperbolic elements of RAAG-like groups have stable commutator length of at least $1/24$. Their proof that the quasimorphisms take the value $1$ is quite technical and relies on some tools they introduce: the essential characteristic set and equivariant Euclidean embeddings. Here it is shown that this is unnecessary and a much shorter proof is given. This was originally part of my master thesis "Stable commutator length gap in RAAG-like groups" supervised by Alessandra Iozzi at ETH Z\"urich.