Cyclic symmetry averaging
= Cyclic symmetry averaging
If a convex subset of $\mathbb R^n$ is invariant under cyclic coordinate permutation, averaging the $n$ cyclic images of $x$ shows that
$$
\left(\frac1n\sum_jx_j,\ldots,\frac1n\sum_jx_j\right)
$$
also belongs to the set.