Determining surfaces by short curves and applications

The goal of this work is to give new quantitative results about the distribution of semi-arithmetic hyperbolic surfaces in the moduli space of closed hyperbolic surfaces. We show that two coverings of genus g of a fixed arithmetic surface S are P (1g) apart from each other with respect to Teichmuller metric, where P is a polynomial depending only on S whose degree is universal. We also give a super-exponential upper bound for the number of semi-arithmetic hyperbolic surfaces with bounded genus, stretch and degree of the invariant trace field, generalizing for this class similar well known bounds for arithmetic hyperbolic surfaces. In order to get these results we establish, for any closed hyperbolic surface S with injectivity radius at least s, a parametrization of the Teichmuller space by length functions whose values on S are bounded by a linear function (with constants depending only on s) on the logarithm of the genus of S.