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 $\alpha \ge 1$ among nilpotent groups and, more generally, among finitely presented solvable groups with subexponential Dehn function.

19 pages. Comments and suggestions are welcome!