Hilbert-Burch matrices and explicit torus-stable families of finite subschemes of $\mathbb A ^2$

Abstract: Using Hilbert-Burch matrices, we give an explicit description of the Bia{\l}ynicki-Birula cells on the Hilbert scheme of points on $\mathbb A ^2$ with isolated fixed points. If the fixed point locus is positive dimensional we obtain an \'etale rational map to the cell. We prove Conjecture 4.2 from arXiv:2309.06871 which we realize as a special case of our construction. We also show examples when the construction provides a rational \'etale map to the Hilbert scheme which is not contained in any Bia{\l}ynicki-Birula cell. Finally, we give an explicit description of the formal deformations of any ideal in the Hilbert scheme of points on the plane.