Quadratic isometric functions of the Heisenberg groups. A combinatorial proof
It is presented a completely combinatorial proof of the theorem: The 5-dimensional Heisenberg group \({\mathcal H}^5=\langle x,y,u,v\mid[x,u]=[x,v]=[y,u]=[y,v]=[x,y][v,u]=1\rangle\) has a quadratic isoperimetric function. This theorem and its proof can be easily extended to any Heisenberg group \({\mathcal H}^{2n+1}\) with \(n\geq 2\) and to some other 2-nilpotent groups which are central products.
scientific article; zbMATH DE number 1315226