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Let G be the automorphism group of a regular right-angled building X. The standard uniform lattice Gamma_0 in G is a canonical graph product of finite groups, which acts discretely on X with quotient a chamber. We prove that the commensurator of Gamma_0 is dense in G. This result was also obtained by Haglund. For our proof, we develop carefully a technique of unfoldings of complexes of groups. We use unfoldings to construct a sequence of uniform lattices Gamma_n in G, each commensurable to Gamma_0, and then apply the theory of group actions on complexes of groups to the sequence Gamma_n. As further applications of unfoldings, we determine exactly when the group G is nondiscrete, and we prove that G acts strongly transitively on X.
We show that if a right-angled Artin group $A(Gamma)$ has a non-trivial, minimal action on a tree $T$ which is not a line, then $Gamma$ contains a separating subgraph $Lambda$ such that $A(Lambda)$ stabilizes an edge in $T$.
We consider the question of which right-angled Artin groups contain closed hyperbolic surface subgroups. It is known that a right-angled Artin group $A(K)$ has such a subgroup if its defining graph $K$ contains an $n$-hole (i.e. an induced cycle of l
We characterize when (and how) a Right-Angled Artin group splits nontrivially over an abelian subgroup.
The Tits Conjecture, proved by Crisp and Paris, states that squares of the standard generators of any Artin group generate an obvious right-angled Artin subgroup. We consider a larger set of elements consisting of all the centers of the irreducible s
We show that certain right-angled Coxeter groups have finite index subgroups that quotient to $mathbb Z$ with finitely generated kernels. The proof uses Bestvina-Brady Morse theory facilitated by combinatorial arguments. We describe a variety of exam