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

Using Hilbert-Burch matrices, we give an explicit description of the Białynicki-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 étale 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 étale map to the Hilbert scheme which is not contained in any Białynicki-Birula cell. Finally, we give an explicit description of the formal deformations of any ideal in the Hilbert scheme of points on the plane.