V.D41 — Clopen frame

A clopen frame at depth n is a pair (U_k^(n), e_k^(n)) where U_k^(n) = [alpha_k, alpha_{k+1}] is the k-th clopen arc of tau^1 and e_k^(n) = (e_gamma, e_eta, e_omega) is a coherence basis for the fiber T^2 over that arc.