Moderate Growth and Rapid Decay Nearby Cycles via Enhanced Ind-Sheaves

Abstract

For any holomorphic function $f:X\to \mathbb{C}$ on a complex manifold $X$, we define and study moderate growth and rapid decay objects associated to an enhanced ind-sheaf on $X$. These will be sheaves on the real oriented blow-up space of $X$ along $f$. We show that, in the context of the irregular Riemann–Hilbert correspondence of D’Agnolo–Kashiwara, these objects recover the classical de Rham complexes with moderate growth and rapid decay associated to a holonomic ${\mathcal{D}}_X$-module. In order to prove the latter, we resolve a recent conjectural duality of Sabbah between these de Rham complexes of holonomic ${\mathcal{D}}_X$-modules with growth conditions along a normal crossing divisor by making the connection with a classic duality result of Kashiwara–Schapira between certain topological vector spaces. Via a standard dévissage argument, we then prove Sabbah’s conjecture for arbitrary divisors. As a corollary, we recover the well-known perfect pairing between the algebraic de Rham cohomology and rapid decay homology associated to integrable connections on smooth varieties due to Bloch–Esnault and Hien.