m at h . A G ] 1 5 Ju l 2 00 5 Gromov - Witten Invariants of P 2 - Stacks

The Gromov-Witten theory of Deligne-Mumford stacks is a recent development, and hardly any computations have been done beyond 3-point genus 0 invariants. This paper provides explicit recursions which, together with some invariants computed by hand, determine all genus 0 invariants of the stack PD,2 . Here D is a smooth plane curve and PD,2 is locally isomorphic to the stack quotient [U/(Z/(2))], where U → V ⊂ P2 is a double cover branched along D ∩ V . The introduction discusses an enumerative application of these invariants.