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31 votes
11 answers
13k views

Uniformization theorem for Riemann surfaces

How does one prove that every simply connected Riemann surface is conformally equivalent to the open unit disk, the complex plane, or the Riemann sphere, and these are not conformally equivalent to ...
29 votes
7 answers
7k views

Elementary proof of Riemann-Roch for compact Riemann surfaces

I am supposed to give a talk about the Riemann-Roch theorem to a seminar of first and second year graduate students. I want to do Riemann-Roch for compact Riemann surfaces, but I am open to perhaps ...
user avatar
20 votes
2 answers
1k views

Belyi functions on non-compact surfaces; or: Building Riemann surfaces from equilateral triangles

Some background on (compact) Belyi surfaces $\newcommand{\Ch}{\hat{\mathbb{C}}}$ A compact Riemann surface $X$ is called a Belyi surface if there exists a branched covering map $f:X\to \Ch$ such that $...
Lasse Rempe's user avatar
  • 6,548
9 votes
3 answers
927 views

Are real-analytic functions in $\mathbb{R}^2$ holomorphic after suitable change of coordinates?

I'm not sure this is a research-level question, but I couldn't find an answer after a bit of searching, so here goes. Let $f: \mathbb{R}^2 \to \mathbb{R}^2$ be a real-analytic function. Can we always ...
Mikhail Tikhomirov's user avatar
12 votes
2 answers
849 views

Visualizing holomorphic differentials on a compact Riemann surface?

It is a classical result that the vector space of holomorphic differentials on a compact Riemann surface of genus $g$ has dimension $g$. I am wondering if there is a way of visualizing this wonderful ...
Timothy Chow's user avatar
  • 82.6k
12 votes
2 answers
2k views

Universal covering of a 2-sphere without $n$ points

Let $X$ be the $\mathbb{C}\mathbb{P}^1$ with $n$ points deleted. Let $n\geq 3$. If I understand correctly, the universal covering of $X$ is isomorphic to the upper half plane as a complex analytic ...
asv's user avatar
  • 21.8k
11 votes
3 answers
748 views

Explicit triples of isomorphic Riemann surfaces

Inspired by a discussion with Neil Strickland I am very interested to hear of explicit examples (one per answer, please), as follows. A compact Riemann surface can be presented in many different ways....
9 votes
3 answers
1k views

An analytic proof of the De Franchis theorem

The De Franchis theorem in its simplest form states that given two compact Riemann surfaces $\Sigma_{g_1},\Sigma_{g_2}$ where $g_1,g_2 > 1$, there are only finitely many non-constant holomorphic ...
Jaikrishnan's user avatar
  • 1,159
8 votes
2 answers
392 views

Image of boundary circle under map from punctured elliptic curve to ℂ

Let $E=\mathbb C/\Lambda$ be an elliptic curve, and let $D\subset E$ be a very small disc. ($D$ is round for the usual flat metric on $E$) By the main result of [1], there exists a holomorphic ...
André Henriques's user avatar
7 votes
1 answer
794 views

Non-algebraic curve visualisation

Is there any software which can automatically visualise a non-algebraic complex curve, I mean the structure of it's ramification points and sheet? I think a good test example would be the Lambert ...
Sasha's user avatar
  • 1,343