Dehn functions of subgroups of products of free groups. Part II: Precise computations

Abstract

We prove that the Bridson-Dison group has quartic Dehn function, thereby providing the first precise computation of the Dehn function of a subgroup of a direct product of free groups with super-quadratic Dehn function. We also prove that coabelian subgroups of direct products of $n$ free groups of finiteness type ${\mathcal{F}}_{n-1}$ and of corank $r\le n-2$ have quadratic Dehn functions.

The paper arXiv:2406.19860v1 was split into two parts. This is the second part (Theorem B and E of the original version). The first part is available at arXiv:2406.19860v2. 27 pages, 3 figures