$L^2$ and intersection cohomologies for the reductive representation of the fundamental groups of quasiprojective manifolds with unipotent local monodromy

Research paper by Xuanming Ye, Kang Zuo

Indexed on: 11 Jul '12Published on: 11 Jul '12Published in: Mathematics - Differential Geometry


Let $X$ be a projective manifold, and $D$ be a normal crossing divisor of $X$. By Jost-Zuo's theorem that if we have a reductive representation $\rho$ of the fundamental group $\pi_{1}(X^{*})$ with unipotent local monodromy, where $X^*=X-D$, then there exists a tame pluriharmonic metric $h$ on the flat bundle $\mathcal V$ associated to the local system $\mathbb V$ obtain from $\rho$ over $X^*$. Therefore, we get a harmonic bundle $(E, \theta, h)$, where $\theta$ is the Higgs field, i.e. a holomorphic section of $End(E)\otimes\Omega^{1,0}_{X^*}$ satisfying $\theta^2=0$. In this paper, we study the harmonic bundle $(E,\theta,h)$ over $X^*$. We are going to prove that the intersection cohomology $IH^{k}(X; \mathbb V)$ is isomorphic to the $L^{2}$-cohomology $H^{k}(X, (\mathcal A_{(2)}^{\cdot}(X,\mathcal V), \mathbb D))$.