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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.

34 votes
6 answers
5k views

Kähler structure on cotangent bundle?

The total space of cotangent bundle of any manifold $M$ is a symplectic manifold. Is it true/false/unknown that for any $M$, $T^*M$ has Kähler structure? Please support your claim with reference or co …
2 votes

Kähler structure on cotangent bundle?

In the reference mentioned by Zemisch, Guillemin and Stenzel prove: Theorem. For an analytic manifold $L$ and analytic metric $g$ on $L$, there is a $\sigma$-invariant neighborhood ($\sigma(x,v)=(x,-v …
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11 votes
4 answers
4k views

Question on Kähler/ample cone, cone of curves....

Assume $X$ is smooth "simply connected" complex projective variety and $Y\subset X$ a smooth hyperplane section. ( $Y= X\cap H$, $H\subset \mathbb{P}^n$). Let's $NE(X)$ be the cone of effective 1-cyc …
12 votes
3 answers
4k views

Lefschetz hyper-plane theorem for singular projective varieties?

Lefschetz hyper-plane theorem for smooth projective varieties, $X\subset \mathbb{P}^{n+1}$ says: For smooth hyperplane section $Y= X\cap H$, the restriction map $H^i(X) \rightarrow H^i(Y)$ is an isomo …
3 votes
2 answers
333 views

Fixed-point free holomorphic involutions

Here is the new version of the question which is more explicit. The older version is below. I am looking for complex projective varieties (in dimensions $2$ and higher) admitting a fixed-point free ho …
2 votes
2 answers
2k views

Toroidal embedding

Its known ( see " The birational geometry of degenerations") that there exist a smooth one parameter family (i.e. total space is smooth) of two dimensional complex toris over unit disk whose central f …
1 vote
1 answer
2k views

Section for a given fibration

Let $X\rightarrow S$ be a (projective, flat... or any other assumption which makes you happy) fibration of a smooth threefold over a smooth surface with connected one-dimensional fibers. As an exampl …
4 votes
3 answers
901 views

wedge product of second chern class and kahler form on Calabi-Yau 3-folds.

Let $X$ be a smooth Calabi-Yau 3-fold with Kahler form $w$, It is true that $\int c_2(TX) \wedge w \geq 0$ (for any Kahler form $w$ on $X$). Proof via algebraic geometry is rather difficult. Some wh …
16 votes
3 answers
5k views

Do we have non-abelian sheaf cohomology?

Lets $X$ be a complex manifold (algebraic variety), $N$ an integer, and consider the sheaf $F$ defined by: $F(U)$ ={ holomorphic maps $f: U\rightarrow GL(N,\mathbb{C})$ } with multiplicative structur …
9 votes
2 answers
4k views

Reference request: moduli spaces of vector bundles

I am trying to study the moduli spaces of holomorphic vector bundles quickly, and I'm primarily interested in understanding: Why and where the stability condition is used. How are the moduli spaces …
21 votes
3 answers
5k views

flatness in complex analytic geometry

It is always a pain to move back and forth between definitions in algebraic geometry and complex analytic geometry. Dictionary is much easier when are working with (family of) smooth varieties but the …
4 votes
0 answers
148 views

Looking for some abelian surface fibration

Do you know of any explicit smooth complex projective threefold $X$ with an Abelian surface fibration over $\mathbb{P}^1$ such that $K_X = [-F]$ where $F$ is the fiber class divisor. I am not lookin …
3 votes
1 answer
256 views

Local holomorphic equations for symplectic divisors

If $(X,\omega)$ is a symplectic manifold and $J\colon TX \to TX$ is an almost complex structure, we know that $J$ is actually a complex structure if and only if the Nijenhuis tensor $N_J(\cdot,\cdot)$ …
2 votes
1 answer
331 views

almost holomorphic line bundles

Let $(L,\omega_L) \to (M,\omega_M)$ be a symplectic line bundle (symplectic line=real dimension 2) over a symplectic manifold $M$. Each of these objects can be equipped with an almost complex structur …
16 votes
4 answers
3k views

Moduli space of genus 2 curves

Does any body know any reference in which the geometry of compactified moduli space of genus two curves ( Which is a three dimensional variety/stack/...) has been studied?

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