The Weil-Petersson and Thurston symplectic forms

We present a new topological interpretation of the Weil-Petersson form on the Teichmuller space tau(S) of a compact oriented surface S with negative Euler characteristic, i.e. with genus at least 2, in terms of the shearing coordinates for tau(S) associated to a maximal geodesic lamination lambda on S. In the corresponding expression, the Weil-Petersson form coincides, up to a multiplicative constant, with the Thurston intersection form on the space of transverse cocycles for a maximal geodesic lamination lambda on S.