The critical curve C which Im<(tau)over cap>=0, <(tau)over cap>=a(D)/a
, in, determines hyperbolic domains whose Poincare metric can be const
ructed in terms of a(D) and a. We describe C in a parametric form rela
ted to a Schwarzian equation and prove new relations for N=2 supersymm
etric SU(2) Yang-Mills theory. In particular, using the Koebe 1/4 theo
rem and Schwarz's lemma, we obtain inequalities involving u, a(D), and
a which seem related to the renormalization group. Furthermore, we ob
tain a closed form for the prepotential as a function of a. Finally, w
e show that partial derivative(<(tau)over cap>) [tr phi(2)]<((tau)over
cap>)=1/8 pi ib(1)[phi](<(tau)over cap>)(2), where b(1) is the one-lo
op coefficient of the beta function.