Verdier specialization and restrictions of Hodge modules

Abstract

We give an explicit formula to express the cohomological pullback functors of Hodge modules under closed immersions of smooth varieties using Verdier specializations and $V$-filtrations of Kashiwara and Malgrange. This was locally obtained by the first two authors assuming the existence of global defining functions. We also give a quite simplified proof of the theorem reducing to the monodromical case via the Verdier specialization and using induction on codimension.