Questions tagged [complex-geometry]
Complex geometry is the study of complex manifolds and complex algebraic varieties. It is a part of both differential geometry and algebraic geometry. For elementary questions about geometry in the complex plane, use the tags (complex-numbers) and (geometry) instead.
4,037 questions
3 votes
0 answers
58 views
Canonical divisor of a singular surface.
Let $S$ be a normal projective algebraic surface over a complex numbr field ${\Bbb C}$. Suppose that $S$ has a single isolated singular point $p \in S$. Let $U \colon= S\setminus p$ be a smooth open ...
1 vote
1 answer
109 views
First Chern class of a line bundle
I'm trying to follow my lecture course in fiber bundles and I'm not sure whether my lecturer has made a mistake. Definition. Let $M$ be a complex manifold. Then define the picard group $\mathrm{Pic} (...
2 votes
0 answers
43 views
Splitting of the Chiral de Rham differential for affine space
I am currently reading through Malikov, Schechtman and Vaintrob's paper Chiral de Rham Complex. In the proof of Theorem 2.4, i.e. that the chiral de Rham complex extends the usual de Rham complex for ...
6 votes
1 answer
159 views
Why don't all complex manifolds admit spin structures?
I've been studying $\mathrm{Spin}^c$-structures on complex manifolds, in particular attempting to understand why every complex $n$-manifold with $n \geq 2$ has a canonical such structure. The usual ...
4 votes
1 answer
175 views
How to understand the twists physicists use in topological string theory?
I have a very hard time to understand something physicists call $A$ or $B$ twists in the context of topological string theory. A canonical reference seems to be this Witten's paper. Let $\Sigma$ be a ...
0 votes
0 answers
47 views
Induced connection on pull-back of conjugate bundle
Suppose X be a Riemann surface endowed with anti-holomorphic involution $\sigma_X$. $V$ is a holomorphic vector bundle on $X$ with holomorphic connection $D$. It is a fact that $\sigma_X^*\overline{V}$...
1 vote
1 answer
119 views
Global holomorphic sections of $\mathcal{O}(1)$
Let us consider the complex projective space $\mathbb{CP}^n$ as a complex manifold. The holomorphic line bundle $\mathcal{O}(1)$ over $\mathbb{CP}^n$ may be defined as the dual bundle of the ...
0 votes
0 answers
49 views
Existence domain as a complex 1-manifold
I'm working through Kerr's notes (#4 here) in algebraic geometry and am stuck on the following exercise: Show that the existence domain $M$ of $$ \mathfrak{F}(z) = \left( \prod_{i=1}^{2g+2} (z-\...
2 votes
0 answers
73 views
Understanding modular curves as "moduli of Hodge structures"
It is well-known that modular curves parametrize elliptic curves with level structures. For the purpose of this question, I will work complex-analytically and describe analytically the moduli space $$\...
2 votes
1 answer
94 views
Why does $f$ map components of the critical locus to a point? (Griffiths-Harris, pp. 19-20)
I am stuck on a step in the proof of the proposition on pages 19-20 of Griffiths-Harris's "Principles of Algebraic Geometry" that may be obvious. Let $f: U → V$ be a holomorphic map between ...
8 votes
0 answers
248 views
Explicit calculation of the Poincare residue for a pole of order 2
I have been learning about the Poincare residue in the context of the cohomology of projective hypersurfaces. For such a hypersurface, $X\subset\mathbb{P}^{n+1}$ with defining equation $F$, the ...
3 votes
2 answers
118 views
Why do we have $q_* \mathcal{O}_{\mathbb P^n \times S}(m) = H^0(\mathbb P^n, \mathcal{O}_{\mathbb P^n}(m)) \otimes \mathcal{O}_S$?
All schemes in the following are assumed to be of finite type over $\mathbb C$. Let $\mathbb P^n$ be a projective space and $S$ a scheme. Denote by $$p : \mathbb P^n \times_{\mathbb C} S \to \mathbb P^...
1 vote
0 answers
69 views
Morphism of holomorphic vector bundles
In Huybrechts' Complex Geometry, he defines a morphism of holomorphic vector bundles $\pi_E: E \to X$ and $\pi_F: F \to X$ to be a holomorphic map $f: E \to F$ such that $\pi_E = \pi_F \circ f$, the ...
1 vote
0 answers
61 views
Families of Almost Complex Structures that Determine a Symplectic Form [closed]
If you have a given symplectic form $\omega \in \Omega^{2}(M)$ on a smooth manifold $M$ it determines a space $\mathcal{J}(M,\omega)$ of compatible almost complex structures. Now, given a manifold $M$ ...
0 votes
0 answers
42 views
what does analytically isomorphic mean for complex spaces?
Here"analytically isomorphic"means that the completion of the local rings of two points in some complex spaces are isomorphic. The smooth case is trivial so the only interesting case is that ...