Nilpotent groups with Dehn function $n^2 \log n$

Abstract

We exhibit 2-step Carnot groups with Dehn function $n^2 \log n$, sharpening Wenger's superquadratic lower bound for these groups. Some of these groups admit lattices, yielding finitely generated nilpotent groups with Dehn function $n^2 \log n$. This gives the first exact computation of a Dehn function which does not grow like $n^\alpha$ for any $\alpha \geq 1$ among nilpotent groups and, more generally, among finitely presented solvable groups with subexponential Dehn function.