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Let $X$ be a complex smooth projective variety and $D$ a divisor on $X$ with normal crossings. As usual, denote by $D(m)$ the disjoint union of all possible intersections of $m$ irreducible components of $D$. Let $W$ be the weight filtration on the sheaf of logarithmic differentials $\Omega^\bullet_X(\log D)$.

Is the following equality of dimensions true? $$ h^q(X, \mathrm{Gr}^W_m \Omega^p_X(\log D))=h^q(D(m), \Omega^{p-m}_{D(m)}) $$

I have seen that there is an isomorphism of complexes $\mathrm{Gr}_m^W \Omega^\bullet_X(\log D) \simeq (a_m)_\ast \Omega^\bullet_{D(m)}[-m]$, but I am uncertain about the meaning of $[-m]$.

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  • $\begingroup$ The index means what you think it does: dimension shift. $\endgroup$ Jun 18, 2015 at 19:24
  • $\begingroup$ Given a complex, $(A[-m])^n= A^{n-m}$ (and sometimes the differential gets multiplied by $(-1)^{-m}$). This implies that equality you ask about is true. $\endgroup$ Jun 18, 2015 at 19:44

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