TITLE: Does pullback and d and dbar commute?
QUESTION [6 upvotes]: If $M$ is a complex manifold. we can write $d = \partial + \overline{\partial}$. Does pullback  commute with either $\partial$ or $\overline{\partial}$?

REPLY [4 votes]: If $M$ and $N$ are complex manifolds and $f:M\to N$ is a smooth map, then $f^*$ commutes with $\partial$ and $\bar\partial$ if and only if $f$ is holomorphic.  To prove the "only if" implication, write $f$ in local holomorphic coordinates as $(w^1,\dots,w^n) = (f^1(z),\dots,f^n(z))$, and note that the equation $\bar\partial(f^*w^j)=  f^*(\bar\partial f^j)$ reduces to $\bar\partial f^j=0$, which is exactly the Cauchy-Riemann equations for $f^j$.  The converse is a straightforward computation in local holomorphic coordinates.