# Complex analytic space

In mathematics, a complex analytic space is a generalization of a complex manifold which allows the presence of singularities. Complex analytic spaces are locally ringed spaces which are locally isomorphic to local model spaces, where a local model space is an open subset of the vanishing locus of a finite set of holomorphic functions.

## Definition

Denote the constant sheaf on a topological space with value $\mathbb{C}$ by $\underline{\mathbb{C}}$. A $\mathbb{C}$-space is a locally ringed space $(X, \mathcal{O}_X)$ whose structure sheaf is an algebra over $\underline{\mathbb{C}}$.

Choose an open subset $U$ of some complex affine space $\mathbb{C}^n$, and fix finitely many holomorphic functions $f_1,\dots,f_k$ in $U$. Let $X=V(f_1,\dots,f_k)$ be the common vanishing locus of these holomorphic functions, that is, $X=\{x\mid f_1(x)=\cdots=f_k(x)=0\}$. Define a sheaf of rings on $X$ by letting $\mathcal{O}_X$ be the restriction to $X$ of $\mathcal{O}_U/(f_1, \ldots, f_k)$, where $\mathcal{O}_U$ is the sheaf of holomorphic functions on $U$. Then the locally ringed $\mathbb{C}$-space $(X, \mathcal{O}_X)$ is a local model space.

A complex analytic space is a locally ringed $\mathbb{C}$-space $(X, \mathcal{O}_X)$ which is locally isomorphic to a local model space.

Morphisms of complex analytic spaces are defined to be morphisms of the underlying locally ringed spaces, it is also called holomorphic maps.