Automorphisms of Sylow $p$-Subgroups of Chevalley Groups Defined over Residue Rings of Integers

We deal with automorphisms of Sylow $p$-subgroups $S\Phi(Z_{p^m})$ of Chevalley groups of normal types $\Phi$, defined over residue rings $Z_{p^m}$ of integers modulo $p^m$, where $m\geqslant 2$ and $p>3$ is a prime. It is shown that in this case all automorphisms of $S\Phi(Z_{p^m})$ factor into a product of inner, diagonal, graph, central automorphisms and some explicitly specified automorphism of order $p$. The results obtained give the answer (under the condition that $p>3$) to Question 12.42 posed by Levchyuk in [4], which called for furnishing a description of automorphisms of a Sylow $p$-subgroup of a normal type Chevalley group over a residue ring of integers modulo $p^m$, where $m\geqslant 2$ and $p$ is a prime.