Directed immersions for complex structures

Abstract

We analyze the differential relation corresponding to integrability of almost complex structures, reformulated as a directed immersion relation by Demailly and Gaussier. Combining results of Clemente [3], we show that applying h-principle techniques yields the following statement: for an almost complex manifold with arbitrary metric $(X, J, g)$, and for $ε> 0$, there exists a smooth function $f : X \rightarrow \mathbb{R}$ and almost complex structure $J'$ on $X$ such that $J$ and $J'$ are $C^0$-close on the graph of $f$ with respect to the extended metric on $X \times \mathbb{R}$, and such that the Nijenhuis tensor of $J'$ on the graph has pointwise sup norm less than $Cε$, where $C$ is a constant depending only on $J$ and $g$. This is an updated version of a previous preprint titled "Almost complex manifolds are (almost) complex".