Remarks on GW/PT under del Pezzo transitions

Abstract

A projective threefold transition $Y \xrightarrow{\phi} \bar{Y} \rightsquigarrow X$ is del Pezzo if $\phi$ contracts a smooth del Pezzo surface to a point. We show that the GW/PT correspondence holds on $Y$ implies that it holds on $X$. In particular, a hypersurface of degree $6$ in $\mathbb{P} (3, 2, 1, 1, 1)$ gives a new example to the correspondence. The main tools are (i) the double point degeneration constructed in arXiv:2508.01374 and (ii) deformations of del Pezzo surfaces into toric surfaces (Proposition 3.12). Applications of the degeneration formulas in GW and PT then reduce the problem to known cases.