# Directed immersions for complex structures

## TL;DR

This paper applies h-principle techniques to almost complex structures, showing they can be approximated by structures with small Nijenhuis tensor on a graph, indicating near integrability.

## Contribution

It demonstrates that any almost complex structure can be approximated by a nearby structure with nearly vanishing Nijenhuis tensor using directed immersion methods.

## Key findings

- Existence of a smooth function and almost complex structure close to the original
- Approximate structures have Nijenhuis tensor norm less than a specified epsilon
- Results extend previous work on the near integrability of almost complex manifolds

## 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 $\epsilon > 0$, 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 $C\epsilon$, 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".