A characterization of the symmetry groups of mono-monostatic convex bodies

Answering a question of Conway and Guy in a 1968 paper, L'angi in 2021 proved the existence of a monostable polyhedron with $n$-fold rotational symmetry for any $n\ge 3$, and arbitrarily close to a Euclidean ball. In this paper we strengthen this result by characterizing the possible symmetry groups of all mono-monostatic smooth convex bodies and convex polyhedra. Our result also answers a stronger version of the question of Conway and Guy, asked in the above paper of L'angi.