Given a Gromov-Witten invariant involving
marked points but with no constraints on the last point, the
string equation expresses this in terms of invariants with fewer
marked points. It is equivalent to annihilation by the differential
operator in the Virasoro conjecture. (The string equation is
a known fact; this part of the Virasoro conjecture is a proved
theorem.)

Jeffrey Herschel Giansiracusa
2005-06-27