(1) School of Mathematical Sciences, Peking University, 100871 Beijing, China
Abstract:
It is proved thatKq(h)=K0(h) for everyh in some class of quasisymmetric mappings of the unit circle with substantial points, whereKq(h):=sup{M(h(Q))/M(Q);Q is a quadrilateral with the domain unit disk} andK0(h) is the extremal maximum dilatation ofh.