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Complex geometry is the study of complex manifolds, complex algebraic varieties, complex analytic spaces, and, by extension, of almost complex structures. It is a part of differential geometry, algebraic geometry and analytic geometry.

5 votes
Accepted

Determine complex analytic germ along a smooth compact curve via normal bundle?

This is equivalent to asking whether for any smooth curve $C$ on a complex manifold $X$, there is an analytic neighborhood of $C$ in $X$ that is equivalent to a neighborhood of $C$ in the normal bundl …
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2 votes

Generalizing the square theorem

There are many examples. Take $X := \mathbb A^1$ and $Y := \mathbb A^2 \smallsetminus \{(0,0)\}$; since all vector bundles on $X$ and $Y$ are trivial, it is sufficient to give an example of a vector b …
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10 votes
Accepted

Branched covers of compact Riemann surfaces

From your group-theoretic description, it seems to me that you are asking for a covering $S' \to S$ which is only ramified over one point of $S$, and the ramification index of each point of the invers …
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2 votes
Accepted

Rational functions on reduced complex varieties that extend to global holomorphic functions

Let $A$ be a noetherian integral domain, $K$ its field of fractions, and $f \in K$. Assume that for each maximal ideal $\frak m$ of $A$ the element $f \in K \subseteq K\otimes_{A}\hat{A}_{\frak m}$ is …
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5 votes
Accepted

Automorphism group of ruled surface

Any automorphisms of $X$ lies over an automorphism of $C$. It seems to me that there is a unique section $C \to X$ with trivial normal bundle, so this section should be carried to itself by an automor …
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5 votes
Accepted

When are the Smooth Sections of a Bundle Generated as a Module (over Smooth Functions) by th...

Swan has proved that taking global section gives an anti-equivalence between finitely generate projective $\Gamma^{\infty}(M)$-modules and $C^{\infty}$ vector bundles on $M$; this correspondence is fu …
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6 votes

Is there an obvious way for showing singularities are quotient?

This is essentially Abhyankar's lemma. What VA says is correct. However, one can simply remark that the subgroups $(d\mathbb Z)^n$ for $d>0$ form a cofinal system of subgroups of finite index, and t …
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3 votes

sections of morphisms of complex spaces

I meant to write this as a comment, but it won't fit. In my opinion, you are confusing the étale analytic with the étale algebraic topology. The étale analytic topology is essentially the same the sa …
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5 votes
Accepted

Uniformity of injectivity for maps associated to linear systems

I think this is true. The condition implies that for some $n$ the sections of $L^{\otimes n}$ are base point free, so $L^{\otimes n}$ is obtained by pulling back $\mathcal O(1)$ along a map $X \to \m …
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14 votes
Accepted

Pushing Complex Structure Forward

For 1): take a double covering $E\to B$, where $E$ and $B$ are compact oriented surface of genus 3 and 2 respectively, and give $E$ a structure of Riemann surface with trivial automorphism group. Abo …
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5 votes

Does a generic curve inside the space of curves with a node at a specific point have only fi...

Yes, a generic curve with one node at a fixed point of $\mathbb P^2$ over a field of characteristic $0$ has only that singularity. This is true in any degree $d$ at least $2$. By looking at a generic …
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12 votes

A simple question about the degree of some vector bundle over rational curve.

Complex curves with anti-holomorphic involutions correspond to real algebraic curves. Your involution has no fixed points, so your curve corresponds to a real curve $C$ of genus 0 with no real points …
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4 votes

What is the local structure of a general Artin stack?

The stack of curves of genus 0 with at most one node is a quotient stack (see The integral Chow ring of the stack of at most 1-nodal rational curves, but Edidin and Fulghesu), so you are fine in this …
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