Curvatures on the Teichm\"uller curve

The Teichm"{u}ller curve is the fiber space over Teichm"{u}ller space of closed Riemann surfaces, where the fiber over a point in Teichm"{u}ller space is the underlying surface. We derive formulas for sectional curvatures on the Teichm"{u}ller curve. In particular, our method can be applied to investigate the geometry of the Weil-Petersson geodesic as a three-manifold, and the degeneration of the curvatures near the infinity of the augmented Teichm"{u}ller space along a Weil-Petersson geodesic, as well as the minimality of hyperbolic surfaces in this three-manifold.