# Tevelev degrees and Hurwitz moduli spaces

Alessio Cela, Rahul Pandharipande, Johannes Schmitt

Alessio Cela, Rahul Pandharipande, Johannes Schmitt

**25/3/21**Published in : arXiv:2103.14055

We interpret the degrees which arise in Tevelev's study of scattering amplitudes in terms of moduli spaces of Hurwitz covers. Via excess intersection theory, the boundary geometry of the Hurwitz moduli space yields a simple recursion for the Tevelev degrees (together with their natural two parameter generalization). We find exact solutions which specialize to Tevelev's formula in his cases and connect to the projective geometry of lines and Castelnuovo's classical count of linear series in other cases. For almost all values, the calculation of the two parameter generalization of the Tevelev degree is new.