Stable Rigidity in the Heisenberg Groups

For $n\ge 2$, we prove that the $C^2$ boundary of a bounded nonempty open set in ${\mathbb{H}}^n$ is volume-preserving stable if and only if it is a Pansu sphere up to left translation and Heisenberg dilation. The proof combines centre reconstruction with a volume-constrained test field derived from Pansu dilation. Consequently, every isoperimetric region admitting an open representative with $C^2$ boundary is a Pansu ball up to these symmetries.