No Arabic abstract
For a finitely generated group $G$ we calculate the Bieri-Neumann-Strebel-Renz invariant $Sigma^1(X(G))$ for the weak commutativity construction $X(G)$. Identifying $S(X(G))$ with $S(X(G) / W(G))$ we show $Sigma^2(X(G),Z) subseteq Sigma^2(X(G)/ W(G),Z)$ and $Sigma^2(X(G)) subseteq $ $ Sigma^2(X(G)/ W(G))$ that are equalities when $W(G)$ is finitely generated and we explicitly calculate $Sigma^2(X(G)/ W(G),Z)$ and $ Sigma^2(X(G)/ W(G))$ in terms of the $Sigma$-invariants of $G$. We calculate completely the $Sigma$-invariants in dimensions 1 and 2 of the group $ u(G)$ and show that if $G$ is finitely generated group with finitely presented commutator subgroup then the non-abelian tensor square $G otimes G$ is finitely presented.
We study the Bieri-Neumann-Strebel-Renz invariants and we prove the following criterion: for groups $H$ and $K$ of type $FP_n$ such that $[H,H] subseteq K subseteq H$ and a character $chi : K to mathbb{R}$ with $chi([H,H]) = 0$ we have $[chi] in Sigma^n(K, mathbb{Z})$ if and only if $[mu] in Sigma^n(H, mathbb{Z})$ for every character $mu : H to mathbb{R}$ that extends $chi$. The same holds for the homotopical invariants $Sigma^n(-)$ when $K$ and $H$ are groups of type $F_n$. We use these criteria to complete the description of the $Sigma$-invariants of the Bieri-Stallings groups $G_m$ and more generally to describe the $Sigma$-invariants of the Bestvina-Brady groups. We also show that the only if direction of such criterion holds if we assume only that $K$ is a subnormal subgroup of $H$, where both groups are of type $FP_n$. We apply this last result to wreath products.
For a group $G$ that is a limit group over Droms RAAGs such that $G$ has trivial center, we show that $Sigma^1(G) = emptyset = Sigma^1(G, mathbb{Q})$. For a group $H$ that is a finitely presented residually Droms RAAG we calculate $Sigma^1(H)$ and $Sigma^2(H)_{dis}$. In addition, we obtain a necessary condition for $[chi]$ to belong to $Sigma^n(H)$.
We calculate the Bieri-Neumann-Strebel-Renz invariant $Sigma^1(G)$ for even Artin groups $G$ with underlying graph $Gamma$ such that if there is a closed reduced path in $Gamma$ with all labels bigger than 2 then the length of such path is always odd. We show that $Sigma^1(G)^c$ is a rationally defined spherical polyhedron.
We compute the BNS-invariant for the pure symmetric automorphism groups of right-angled Artin groups. We use this calculation to show that the pure symmetric automorphism group of a right-angled Artin group is itself not a right-angled Artin group provided that its defining graph contains a separating intersection of links.
In this paper, we compute the {Sigma}^n(G) and {Omega}^n(G) invariants when 1 rightarrow H rightarrow G rightarrow K rightarrow 1 is a short exact sequence of finitely generated groups with K finite. We also give sufficient conditions for G to have the R_{infty} property in terms of {Omega}^n(H) and {Omega}^n(K) when either K is finite or the sequence splits. As an application, we construct a group F rtimes? Z_2 where F is the R. Thompsons group F and show that F rtimes Z_2 has the R_{infty} property while F is not characteristic.