The first $p$-widths of the unit disk

On compact 2-manifolds with non-empty convex boundary, we prove a regularity result for integral 1-varifolds $V$ that are stationary with free boundary and $\mathbb{Z}_2$-almost minimizing in small annuli. That regularity says that $V$ is a free boundary finite geodesic network. Next, using that regularity, we compute the first $p$-widths of the unit closed ball $B^2,$ for $p=1, . . . , 4.$