Rational pullbacks of toric foliations

Abstract

This article is dedicated to the study of singular codimension $1$ foliations $\mathcal{F}$ on a simplicial complete toric variety $X$ and their pullbacks by dominant rational maps $\varphi:\mathbb{P}^n\dashrightarrow X$. First, we describe the singularities of $\mathcal{F}$ and $\varphi^*\mathcal{F}$ for a generic pair $(\varphi,\mathcal{F})$. Then we show that the first order deformations of $\varphi^*\mathcal{F}$ arising from first order unfoldings are the families of the form $\varphi_\varepsilon^*\mathcal{F}$, where $\varphi_\varepsilon$ is a perturbation of $\varphi$. We also prove that the deformations of the form $\varphi^*\mathcal{F}_\varepsilon$ consist exactly of the families which are tangent to the fibers of $\varphi$. In order to do so, we state some results of independent interest regarding the Kupka singularities of these foliations.