is there a way to describe the convexeconvex hull of the set of permutation matrices with exactly one non-trivial cycle?
or maybe I should ask for the convexeconvex hull of cycle matrices :
let $(i_{1},..,i_{k})$ be a cycle then $A$ is a cycle matrix if the entries $(i_{1},i_{2})$ ...$(i_{k},i_{1})$ are $1/k$, and all the others are 0. (it seems to me that this convex hull is the set of non-negative matrices of entries sum equal to 1)