Let $X,Y$ be complex manifolds of $\dim X=n$, $\dim Y=m>1$, $U\subset X$ open and $g\colon U\to Y$ holomorphic embedding. Then $g(U)$ is a submanifold of codimension $m-n\ge1$. It seems clear that $Y\setminus g(U)$ is connected, think for example at $\Bbb C\setminus\{0\}$. I'm searching for a reference, as it seems a well known fact.
1 Answer
$\begingroup$
$\endgroup$
Every (real) codimension $2^+$ embedding has path connected complement.
The proof is by using the tubular neighborhood theorem to reduce to showing that the total space of the normal bundle of $g(U)$ in $Y$ minus the zero section is connected, and noticing that the normal bundle is a rank $2^+$ vector bundle.
See this MO answer.