Wall-crossing for zero-dimensional sheaves and Hilbert schemes of points on Calabi-Yau 4-folds

Abstract: Gross-Joyce-Tanaka arXiv:2005.05637 proposed a wall-crossing conjecture for Calabi-Yau fourfolds. Assuming it, we prove the conjecture of Cao-Kool arXiv:1712.07347 for 0-dimensional sheaf-counting invariants on projective Calabi-Yau 4-folds. From it, we extract the full topological information contained in the virtual fundamental classes of Hilbert schemes of points which turns out to be equivalent to the data of all descendent integrals. As a consequence, we can express many generating series of invariants in terms of explicit universal power series. i) On $\mathbb{C}^4$, Nekrasov proposed invariants with a conjectured closed form arXiv:1712.08128. We show that an analog of his formula holds for compact Calabi-Yau 4-folds satisfying the wall-crossing conjecture. ii) We notice a relationship to corresponding generating series for Quot schemes on elliptic surfaces which are also governed by a wall-crossing formula. This leads to a Segre-Verlinde correspondence for Calabi-Yau fourfolds.